JPH10270345A - Scanning exposure method and scanning type exposure apparatus - Google Patents

Abstract

(57) [Summary] [Problem] To always perform exposure in the shortest time regardless of the set exposure amount. SOLUTION: At the time of scanning exposure, a main controller 50 controls a mask R and a photosensitive substrate W according to the number of exposure pulses per point determined by the relationship between a set exposure amount and a measured average pulse energy. The oscillation frequency of the light source 16 is controlled so as to maintain at least one of the maximum scanning speed and the maximum oscillation frequency of the pulse laser light source 16. Therefore, in a high sensitivity region where the set exposure amount is small and the oscillation frequency does not need to be so high, scanning exposure at the highest scanning speed can be performed regardless of the set exposure amount. On the other hand, when the set exposure amount becomes large, the oscillation frequency must be increased accordingly.However, since the oscillation frequency is the upper limit of the maximum oscillation frequency, in a low sensitivity region where the set exposure amount is large and the maximum scanning speed cannot be maintained. The exposure is performed by setting the oscillation frequency to the maximum oscillation frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning exposure method and a scanning exposure apparatus, and more particularly, to a method for manufacturing a semiconductor device, a liquid crystal display device, an image pickup device (CCD or the like), a thin film magnetic head, and the like. The present invention relates to a scanning exposure method and a scanning exposure apparatus using a pulse laser light source used in a lithography process.

[0002]

2. Description of the Related Art Conventionally, when manufacturing semiconductor devices and the like,
2. Related Art A projection exposure apparatus that transfers and exposes a pattern of a reticle as a mask to each shot area on a wafer (or a glass plate or the like) coated with a photoresist via a projection optical system is used. One basic function of such a projection exposure apparatus is an exposure amount control function for keeping the integrated exposure amount (integrated exposure energy) for each point in each shot area of the wafer within an appropriate range.

[0003] A batch exposure type projection exposure apparatus such as a conventional stepper (when performing exposure of a reticle pattern on a shot area on a wafer, exposure is performed collectively while a wafer stage on which the wafer is mounted is stationary). In the case of using either a continuous light source such as an ultra-high pressure mercury lamp or a pulsed laser light source such as an excimer laser light source as the exposure light source, cutoff control is basically used as the exposure control method. It had been. In this cut-off control, while the exposure light is being irradiated on the wafer coated with the photosensitive material (photoresist), a part of the exposure light is branched and guided to a photoelectric detector called an integrator sensor. Indirectly, the exposure amount on the wafer is detected, and the integrated value of the detection result is a predetermined level (hereinafter, referred to as “set exposure amount”) corresponding to the integrated exposure amount required for the photosensitive material (hereinafter, referred to as “set exposure amount”). The control is such that laser emission is continued until the critical level is exceeded (in the case of continuous light, the shutter is started to close when the critical level is exceeded).

Further, when a pulse laser light source is used as an exposure light source, since a pulse laser beam has energy variation, a plurality of pulses of a certain number or more (hereinafter referred to as "minimum exposure pulse number") or more are used. Exposure with laser light achieves desired exposure amount control accuracy reproducibility. In this case, for example, when exposing a high-sensitivity resist, since the set exposure amount is small, if the laser light from the pulsed laser light source is used as it is, it becomes impossible to perform exposure with more than the minimum number of exposure pulses. Therefore, when the set exposure amount is small, the pulse laser beam is dimmed by, for example, a dimming unit provided in the optical path, so that exposure can be performed with a pulse number equal to or more than the minimum exposure pulse number.

In recent years, in order to transfer a pattern of a larger area onto a wafer with high accuracy without excessively increasing the burden on the projection optical system, a part of the pattern of the reticle is transferred to the projection optical system. In which the reticle and the wafer are sequentially transferred and exposed to each shot area on the wafer by synchronously scanning the reticle and the wafer with respect to the projection optical system in a state where the reticle and the wafer are projected on the wafer.
Scanning projection exposure apparatuses such as the AND scan method have also been developed. In such a scanning exposure type apparatus, the above-described cutoff control cannot be applied because the exposure amount control focusing on only one point on the wafer cannot be applied. Therefore, conventionally, as a first control method, a method of simply integrating the light amounts of the respective pulsed illumination lights to perform exposure control (open exposure control method) has been used. As a second control method, for example, as disclosed in Japanese Patent Application Laid-Open No. 6-252022, a slit-shaped exposure area (a conjugate with a slit-shaped illumination area on a reticle) is provided in a scanning direction on a wafer. Area, the wafer is scanned relative to this area), the integrated exposure amount is measured in real time for each pulse illumination light, and the target of the next pulse illumination light is measured based on the integrated exposure amount. A method of individually calculating energy and controlling the energy of each pulsed illumination light (pulse exposure amount control method) has been considered, but the algorithm is complicated.

In the former first control method, the pulse energy is finely adjusted so that the following relationship is satisfied in order to obtain the desired linearity of the exposure amount control, that is, the number of exposure pulses is an integer. There is a need to.

(Set exposure amount) = (Number of pulses) × (Average energy of one pulse) (1) Here, the average energy of one pulse is a value measured by an integrator sensor immediately before exposure. For this reason, a pulse energy fine modulator has been provided in the optical path.

FIGS. 11A and 11B show an example of a conventional energy fine modulator. Of these, FIG.
In the fine grating modulator of the double grating system shown in FIG. 1, a fixed grating plate 72 in which transmission portions and light shielding portions are formed at a predetermined pitch on the optical path of the laser beam LB to be pulsed.
And a movable grid plate 74 that is movable in the pitch direction of the grid are superposed, and the transmittance of the laser beam LB can be finely modulated by shifting the relative positions of the two grid plates 72, 74. It has become. FIG.
In the fine modulator shown in (B), two glass plates 76 and 78 each having an antireflection coating applied to both surfaces are inclined symmetrically at a variable inclination angle θ on the optical path of the laser beam LB. It is arranged in. Then, by utilizing the characteristic that the transmittance of the glass plates 76 and 78 changes according to the incident angle of the laser beam LB, the overall transmittance for the laser beam LB is finely adjusted by controlling the inclination angle θ. I have. In addition, there is an example in which the set energy of the laser itself, which is the light source, is modulated.

In the case of a scanning exposure apparatus, the following equation must be satisfied. V = Ws / N × f (2) In the above equation, V is the scanning speed during scanning exposure of the wafer (wafer stage), and Ws is the width of the slit-like exposure area on the wafer surface in the scanning direction (slit width). ), N is the number of exposure pulses per point, and f is the laser oscillation frequency.

In the flow of the conventional exposure sequence, the exposure amount is set, the average energy on the image plane is measured, the number of pulses per point is calculated, the slit width Ws treated as a constant, and the laser oscillation frequency f Thus, the scanning speed V was determined. In this case, the laser oscillation frequency f is fixed to the maximum oscillation frequency f ₀ that is determined by the maximum scanning speed (the maximum scanning speed) defined by the performance (including the mechanical performance) of the stage control system of the exposure apparatus. I was

[0011] That is, in the conventional scanning exposure apparatus, the slit width Ws is a fixed value determined from optical design, maximum oscillating corresponding to the laser oscillation frequency f also scan fastest V _max determined by the performance of the stage control system Frequency f
_Since it was fixed at ₀ (f = f ₀ ), 1
When the exposure pulse number N per point is minimum exposure pulse number N _min, i.e. when it is N = N _min, (2) the scanning speed V from the relation of expression had become as defined in V _max.

[0012]

By the way, in the case of the scanning type exposure apparatus as well, in order to obtain a predetermined exposure dose reproducibility, a certain number (minimum) It is necessary to perform exposure with a plurality of pulse laser beams equal to or more than the number of exposure pulses. Also in this case, when the set exposure amount is small, for example, when exposing a high-sensitivity resist, the pulse laser beam is dimmed by, for example, a dimming means (energy coarse adjuster) installed on the optical path, and the minimum exposure pulse We meet the conditions.

As the energy rough adjuster in this case, for example, as shown in FIG. 11C, a plurality of discs having different transmittances (= 1-dimming rate) are provided on a rotatable disk 80 called a revolver. An ND filter 84 is arranged in one or more stages, and an energy rough adjuster is used. By rotating each revolver 80, the transmittance for the incident laser beam LB can be changed from 100% to several stages. (6 × 6 = 36 steps in the case of FIG. 11C). That is, the setting of the transmittance by the energy rough adjuster is discrete (usually in a geometric series).

For this reason, depending on the set exposure amount, it may be difficult to set a corresponding (proportional) dimming rate, and in the case of such a set exposure amount, the dimming ratio corresponding to the set exposure amount may be difficult. Without selecting an ND filter that provides the closest dimming rate among combinations of dimming rates below the rate, the number N of exposure pulses per point is determined by the discrete amount of the ND filter transmittance (ideal It has to be set to a value larger than the minimum exposure pulse number _Nmin by the difference from the dimming rate corresponding to the set exposure amount set by the continuously variable energy modulator. Therefore, (2) As is clear from the relationship of the formula, it can not maintain the scanning speed V always the maximum speed V _max, resulting in the exposure time T _exp (= Ws / V) of ND filter permeability As a result, it takes extra time for the discrete amount, and the ideal throughput is reduced at a certain set exposure amount. That is,
The relationship between the set exposure amount (S ₀ ) and the exposure time (T _exp ) is
It was like the dotted line shown in FIG.

The present invention has been made under such circumstances, and an object of the present invention is to provide a scanning apparatus capable of always performing exposure in the shortest time regardless of a high sensitivity area and a low sensitivity area. An object of the present invention is to provide an exposure method.

It is another object of the present invention to perform exposure in a high sensitivity region in the shortest time without being affected by the discrete dimming rate of the dimming means, and to achieve low sensitivity. An object of the present invention is to provide a scanning exposure apparatus capable of improving the throughput even in a region.

It is still another object of the present invention to provide a method for producing a desired integrated exposure for the next shot while maintaining the scanning speed when the pulse energy during exposure fluctuates, particularly in a high sensitivity exposure region. It is an object of the present invention to provide a scanning exposure method capable of performing exposure to obtain an amount.

It is still another object of the present invention to provide a method for producing a desired integrated exposure for the next shot while maintaining a scanning speed when a pulse energy during exposure is changed, particularly in a high sensitivity exposure region. It is an object of the present invention to provide a scanning exposure apparatus capable of performing exposure to obtain an amount.

[0019]

According to the first aspect of the present invention, a predetermined illumination area on a mask (R) is illuminated by pulsed light from a pulse laser light source (16), and the mask (R) is exposed to light. A scanning exposure method for sequentially projecting and exposing a pattern formed on the mask (R) onto a photosensitive substrate (W) while relatively scanning the substrate (W) with respect to a projection optical system (PL); Measuring the average pulse energy of the pulsed light from the pulse laser light source (16); and scanning according to the number of exposure pulses per point determined by the relationship between the set exposure amount and the measured average pulse energy. At the time of exposure, the oscillation frequency of the pulse laser light source is maintained so as to maintain at least one of the maximum scanning speed of the mask (R) and the photosensitive substrate (W) and the maximum oscillation frequency of the pulse laser light source (16). And a step of controlling the number.

According to this, prior to the scanning exposure, the average pulse energy of the pulse light from the pulse laser light source is measured, and at the time of the scanning exposure, the relationship between the set exposure amount and the measured average pulse energy is measured. The oscillation frequency of the pulse laser light source is controlled so as to maintain at least one of the maximum scanning speed between the mask and the photosensitive substrate and the maximum oscillation frequency of the pulse laser light source according to the number of exposure pulses per point determined by . That is, according to the present invention, the oscillation frequency f of the pulse laser light source, which has been a fixed value in the past, changes the maximum scanning speed between the mask and the photosensitive substrate (the highest scanning speed) or the pulse laser light source according to the number N of exposure pulses. Is controlled so as to maintain at least one of the maximum oscillation frequencies. For this reason, in the region where the set exposure amount is small and the oscillation frequency necessary to obtain the maximum speed is within the maximum oscillation frequency,
Scanning exposure can be performed at the highest scanning speed regardless of at least the set exposure amount, and the throughput can be maintained at the highest. In this case, the oscillation frequency of the pulse laser light source is controlled based on the relationship of the above-described equation (2). On the other hand, when the set exposure amount increases, the laser oscillation frequency must be increased accordingly. However, the laser oscillation frequency cannot be higher than the maximum oscillation frequency which is the upper limit. Therefore, in an area where the set exposure amount is large and the maximum scanning speed cannot be maintained (this area is referred to as a “low sensitivity area” in this specification), the laser oscillation frequency is set to the maximum oscillation frequency, and the above-described (2) The exposure is performed at a scanning speed determined based on the relationship of the expression (1). in this case,
As is clear from equation (2), the maximum oscillation frequency is set to f _max
Then, the scanning speed becomes (f _max / f ₀ ) times the conventional one, and the exposure time per point is suppressed to the conventional f ₀ / f _max , and clearly f _max ≧ f ₀ , so that the low sensitivity is obtained. Throughput also improves in the area. Also, even if the energy of the pulse laser light source can be continuously modulated, since f _max ≧ f ₀ , the range of the set exposure amount that can be exposed at the maximum scanning speed becomes wider than before.

According to a second aspect of the present invention, a predetermined illumination area on a mask (R) is illuminated by pulsed light from a pulse laser light source (16), and the mask (R) and the photosensitive substrate (W) are illuminated. A scanning type exposure apparatus for sequentially projecting and exposing a pattern formed on said mask (R) onto a photosensitive substrate (W) while relatively scanning with respect to a projection optical system (PL),
A mask stage (RST) holding the mask (R) and movable in a predetermined scanning direction; a substrate stage (14) holding the photosensitive substrate (W) and movable at least in the scanning direction; A stage control system (48, 5) that relatively scans the mask stage (RST) and the substrate stage (14) at a predetermined speed ratio with respect to the projection optical system (PL).
0, 54R, 54W, 56); frequency changing means (16) for changing the oscillation frequency of the pulse laser light source (16).
d) ;; dimming means (20) having a discrete dimming rate for dimming the pulsed light from the pulse laser light source (16); and the pulse laser light source dimmed by the dimming means (20). Energy measuring means (46) for measuring the average pulse energy of the pulse light from (16); and the stage control according to the number of exposure pulses per point determined by the relationship between the set exposure amount and the average pulse energy. System (48,
50, 54R, 54W, 56), the frequency changing means (16d) to maintain at least one of the maximum scanning speed of the two stages (RST, 14) and the maximum oscillation frequency of the pulse laser light source (16). Control means (50) for controlling.

According to this, in the case where the set exposure amount is small and the dimming rate is 0% (transmittance is 100%), if the minimum number of exposure pulses cannot be secured, the dimming means uses the pulse from the pulse laser light source. Light is dimmed. The average pulse energy of the pulsed light from the pulse laser light source that has been dimmed by the dimming means is measured by the energy measuring means. However, since the dimming rate of the dimming means is discrete, the number of exposure pulses per point determined by the set exposure amount and the measured average pulse energy is not always the minimum exposure pulse number. In most cases, the number is larger than the number of exposure pulses. Therefore, the control means controls the frequency changing means so as to maintain at least one of the maximum scanning speed of both stages and the maximum oscillation frequency of the pulse laser light source by the stage control system according to the number of exposure pulses per point. I do.

That is, according to the present invention, the oscillation frequency f of the pulse laser light source, which was conventionally a fixed value, is changed by the control means in accordance with the exposure pulse number N to the maximum scanning speed (both stages) of both stages by the stage control system. Control is performed via the frequency changing means so as to maintain at least one of the highest scanning frequency or the maximum oscillation frequency of the pulse laser light source.
For this reason, in a high sensitivity region where the set exposure amount is small and the laser oscillation frequency does not need to be so high, even if the number of exposure pulses per point increases due to the discrete amount of the dimming rate, it increases in proportion to the increase. Since the laser oscillation frequency is increased and changed via the frequency changing means, both stages are scanned at the highest scanning speed by the stage control system during exposure regardless of the set exposure amount, and the throughput is maintained at the highest. Becomes possible. In this case, the oscillation frequency of the pulse laser light source is controlled based on the relationship of the above-described equation (2). On the other hand, when the set exposure amount increases, the number of exposure pulses per point increases, and the laser oscillation frequency must be increased accordingly. However, the laser oscillation frequency cannot be higher than the maximum oscillation frequency, which is the upper limit. Accordingly, a low sensitivity area where the set exposure amount is large and the maximum scanning speed cannot be maintained (in this area, the light reduction rate by the light reduction means is 0%).
% (Set to 100% transmittance)), the laser oscillation frequency is set to the maximum oscillation frequency, and exposure is performed at a scanning speed determined based on the relationship of the above equation (2). In this case, as is apparent from equation (2), assuming that the maximum oscillation frequency is f _max , the scanning speed is equal to the conventional (f
_max / f ₀ ), and the exposure time per point is suppressed to the conventional _value f ₀ / f _max , and obviously f _max ≧ f ₀ , so that the throughput is improved even in the low-sensitivity region.
Also, even if the energy of the pulse laser light source can be continuously modulated, since f _max ≧ f ₀ , the range of the set exposure amount that can be exposed at the maximum scanning speed becomes wider than before.

According to a third aspect of the present invention, a mask (R) is illuminated by pulse light from a pulse laser light source (16), and the mask (R) and the photosensitive substrate (W) are projected onto a projection optical system (PL). A scanning exposure method of sequentially projecting and exposing a pattern formed on the mask (R) to a plurality of shot areas on a photosensitive substrate (W) while relatively scanning with respect to each of the shots on the photosensitive substrate (W). Each time the mask pattern is exposed to an area, the pulse laser light source (1
6) detecting the average pulse energy and calculating the integrated exposure amount up to that time;
When the average pulse energy of the pulse laser light source fluctuates, the pulse laser light source (16) is used to secure the necessary number of exposure pulses per point based on the integrated exposure amount of the immediately preceding shot area.
Is characterized by controlling the oscillation frequency of.

According to this, every time the mask pattern is exposed to each shot area on the photosensitive substrate, the average pulse energy of the pulse laser light source is detected and the integrated exposure up to that time is calculated. Then, when the average pulse energy of the pulse laser light source fluctuates, the oscillation frequency of the pulse laser light source is controlled based on the integrated exposure amount of the immediately preceding shot area in order to secure the required number of exposure pulses per point. As described above, according to the present invention, when the exposure of the mask pattern to each shot area on the photosensitive substrate is sequentially performed, the average pulse energy of the pulse laser light source fluctuates. If an error occurs that is unacceptable,
In order to secure the required number of exposure pulses per point, that is, the number of exposure pulses per point determined by the set exposure amount and the measured average pulse energy, the pulse laser is determined based on the integrated exposure amount of the immediately preceding shot area. The oscillation frequency of the light source is controlled. As a result, as is apparent from the above equation (2), by changing the number of exposure pulses without changing the scanning speed, for example, in the case where exposure is performed at the highest scanning speed in a high-sensitivity region, there are certain cases. If the average pulse energy of the pulse laser light source fluctuates during or after exposure of the shot area, the desired integrated exposure amount can be obtained for the next shot while maintaining the maximum scanning speed without being affected by this. Exposure is possible.

According to a fourth aspect of the present invention, the mask (R) is illuminated by pulse light from the pulse laser light source (16), and the mask (R) and the photosensitive substrate (W) are projected onto the projection optical system (PL). A scanning type exposure apparatus for sequentially projecting and exposing a pattern formed on said mask (R) to a plurality of shot areas on a photosensitive substrate (W) while relatively scanning with said pulse laser light source (16). Frequency changing means (16d) for changing the oscillation frequency of the pulse laser light source (1).
Energy measuring means (46) for measuring the average pulse energy of the pulsed light from (6); and the pulse laser light source (16) for each exposure of the mask pattern to each shot area on the photosensitive substrate (W). , And the integrated exposure amount up to that is calculated,
When the average pulse energy of the pulse laser light source fluctuates, control is performed to control the frequency changing means (16d) based on the integrated exposure amount in the immediately preceding shot area so as to secure the required number of exposure pulses per point. Means (50).

According to this, the average pulse energy of the pulse light from the pulse laser light source is measured by the energy measuring means. The control means detects the average pulse energy of the pulse laser light source through the energy measuring means and calculates the integrated exposure amount up to that time every time the mask pattern is exposed to each shot area on the photosensitive substrate. When the average pulse energy of the light source fluctuates,
Based on the integrated exposure amount of the immediately preceding shot area,
The frequency changing means is controlled to secure the number of exposure pulses per point. As described above, according to the present invention, when the exposure of the mask pattern to each shot area on the photosensitive substrate is sequentially performed, the average pulse energy of the pulse laser light source fluctuates. When the error occurs to an unacceptable degree,
In order to secure the number of exposure pulses per point, that is, the number of exposure pulses per point determined by the set exposure amount and the measured average pulse energy, oscillation of the pulse laser light source is performed based on the integrated exposure amount of the immediately preceding shot area. The frequency is controlled. Therefore, by changing the number of exposure pulses without changing the scanning speed, for example, in the case where exposure was performed at the highest scanning speed in a high-sensitivity region, the average of the pulsed laser light source during or after exposure of a certain shot region was exposed. When the pulse energy fluctuates, exposure to obtain the desired integrated exposure amount can be performed for the next shot while maintaining the maximum scanning speed without being affected by the fluctuation.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION

<< First Embodiment >> A first embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a schematic configuration of a scanning exposure apparatus 10 according to the first embodiment. The scanning exposure apparatus 10 is a step-and-scan type scanning exposure apparatus using an excimer laser light source as a pulse laser light source as an exposure light source.

The scanning exposure apparatus 10 includes an illumination system 12 including an excimer laser light source 16 and a reticle R as a mask stage which holds a reticle R illuminated by the illumination system 12 and moves in a predetermined scanning direction. A stage RST, a projection optical system PL for projecting the pattern of the reticle R onto a wafer W as a photosensitive substrate, and an XY stage 1 that holds the wafer W and moves on a horizontal plane (within an XY plane).
4 and a control system for them.

The illumination system 12 includes the excimer laser light source 1
6, beam shaping optical system 18, energy rough adjuster 20, fly-eye lens 22, illumination system aperture stop plate 24, beam splitter 26, first relay lens 28A, second relay lens 28B, fixed reticle blind 30A, movable reticle blind 30B, a mirror M for bending the optical path, a condenser lens 32, and the like.

Here, the components of the illumination system 12 will be described. As the excimer laser light source 16, K
An rF excimer laser light source (oscillation wavelength 248 nm), an ArF excimer laser light source (oscillation wavelength 193 nm), or the like is used. Instead of the excimer laser light source 16, a pulse light source such as a metal vapor laser light source or a harmonic generator of a YAG laser may be used as the exposure light source.

The beam shaping optical system 18 shapes the cross-sectional shape of the laser beam LB pulsed from the excimer laser light source 16 so that the laser beam LB efficiently enters a fly-eye lens 22 provided behind the optical path of the laser beam LB. It is composed of, for example, a cylinder lens and a beam expander (both not shown).

The energy rough adjuster 20 is disposed on the optical path of the laser beam LB behind the beam shaping optical system 18. Here, a plurality of energy adjusters 20 are provided around the rotating plate 34 with different transmittances (= 1−dimming rate). The ND filters (for example, six) (two ND filters 36A and 36D are shown in FIG. 1) are arranged, and the rotating plate 34 is rotated by a drive motor 38, so that the incident laser is The transmittance for the beam LB can be switched from 100% in geometric progression in a plurality of stages. The drive motor 38 is controlled by a main controller 50 described later. Note that a rotary plate similar to the rotary plate 34 may be arranged in two stages so that the transmittance can be more finely adjusted by a combination of two sets of ND filters (see FIG. 11C).

The fly-eye lens 22 is disposed on the optical path of the laser beam LB behind the energy rough adjuster 20,
In order to illuminate the reticle R with a uniform illuminance distribution, a large number of 2
The next light source is formed. Hereinafter, the laser beam emitted from the secondary light source is referred to as “pulse illumination light IL”.

In the vicinity of the exit surface of the fly-eye lens 22,
An illumination system aperture stop plate 24 made of a disk-shaped member is arranged. This illumination system aperture stop plate 24 is provided at equal angular intervals,
For example, an aperture stop composed of a normal circular aperture, an aperture stop composed of small circular apertures for reducing the σ value that is a coherence factor, a ring-shaped aperture stop for annular illumination, and a plurality of apertures for a modified light source method. A modified aperture stop which is eccentrically arranged (only two types of aperture stops are shown in FIG. 1) and the like are arranged. The illumination system aperture stop plate 24 is configured to be rotated by a driving device 40 such as a motor controlled by a main controller 50 described later, so that one of the aperture stops is positioned on the optical path of the pulse illumination light IL. Is set selectively.

On the optical path of the pulsed illumination light IL behind the illumination system aperture stop plate 24, a beam splitter 26 having a small reflectance and a large transmittance is arranged.
A relay optical system including a first relay lens 28A and a second relay lens 28B is disposed with a fixed reticle blind 30A and a movable reticle blind 30B interposed therebetween.

The fixed reticle blind 30A is disposed on a plane slightly defocused from a plane conjugate to the pattern plane of the reticle R, and has a rectangular opening defining an illumination area 42R on the reticle R. In addition, a movable reticle blind 30B having an opening whose position and width in the scanning direction are variable near the fixed reticle blind 30A.
Is arranged, and at the start and end of the scanning exposure, the illumination area 42R is further restricted via the movable reticle blind 30B, so that exposure of an unnecessary portion is prevented.

On the optical path of the pulse illumination light IL behind the second relay lens 28B constituting the relay optical system, the second
A folding mirror M that reflects the pulsed illumination light IL that has passed through the relay lens 28B toward the reticle R is disposed,
A condenser lens 32 is arranged on the optical path of the pulse illumination light IL behind the mirror M.

The operation of the illumination system 12 configured as described above will be briefly described. A laser beam LB pulse-emitted from an excimer laser light source 16 enters a beam shaping optical system 18 where a rear fly-back beam is emitted. After its cross-sectional shape is shaped so as to efficiently enter the eye lens 22,
The light enters the energy rough adjuster 20. Then, the laser beam LB that has passed through one of the ND filters of the energy rough adjuster 20 enters the fly-eye lens 22. Thus, a number of secondary light sources are formed at the exit end of the fly-eye lens 22. After passing through one of the aperture stops on the illumination system aperture stop plate 24, the pulsed illumination light IL emitted from the many secondary light sources reaches a beam splitter 26 having a large transmittance and a small reflectance. The pulse illumination light IL as the exposure light transmitted through the beam splitter 26 passes through the first relay lens 28A, and passes through the fixed reticle blind 3
0A rectangular opening and movable reticle blind 30B
After passing through the second relay lens 28B, the optical path is bent vertically downward by the mirror M, and then passes through the condenser lens 32, and then passes through the condenser lens 32 to form a rectangular illumination area 42R on the reticle R held on the reticle stage RST. Is illuminated with a uniform illuminance distribution.

On the other hand, the pulsed illumination light IL reflected by the beam splitter 26 is received by an integrator sensor 46 composed of a photoelectric conversion element via a condenser lens 44, and the photoelectric conversion signal of the integrator sensor 46 has a peak (not shown). Output DS via hold circuit and A / D converter
(Digit / pulse) is supplied to the main controller 50. As the integrator 46, for example, a PIN-type photodiode or the like having sensitivity in the deep ultraviolet region and having a high response frequency for detecting pulse emission of the excimer laser light source 16 can be used. This integrator sensor 46
And the pulse illumination light IL on the surface of the wafer W
The correlation coefficient with the illuminance (exposure amount) is obtained in advance and stored in the memory 51 provided with the main controller 50.

A reticle R is mounted on the reticle stage RST, and is held by suction via a vacuum chuck (not shown). The reticle stage RST is finely drivable in a horizontal plane (XY plane), and is scanned by a reticle stage driving unit 48 in a predetermined stroke range in a scanning direction (here, the Y direction which is the horizontal direction in FIG. 1). It has become so. The position of the reticle stage RST during this scanning is the same as that of the reticle stage RS.
Measurement is performed by an external laser interferometer 54R via a movable mirror 52R fixed on T, and the laser interferometer 54R
Are supplied to the main controller 50.

The projection optical system PL is composed of a plurality of lens elements having a common optical axis AX in the Z-axis direction arranged to have a telecentric optical arrangement on both sides. The projection optical system PL has a projection magnification α (α is, for example, ４ or ５). Therefore, as described above, the pulsed illumination light I
When the illumination area 42R on the reticle R is illuminated by L, an image obtained by reducing the pattern formed on the reticle R by the projection optical system PL at the projection magnification α is coated on the surface with a resist (photosensitive agent). Projection exposure is performed on the slit-shaped exposure area 42W on W.

The XY stage 14 is scanned by the wafer stage driving unit 56 in the Y direction which is the scanning direction in the XY plane and the X direction orthogonal thereto (the direction perpendicular to the plane of FIG. 1).
Are driven two-dimensionally. On the XY stage 14, a Z tilt stage 58 is mounted.
The wafer W is held on the tilt stage 58 via a wafer holder (not shown) by vacuum suction or the like. The Z tilt stage 58 has a function of adjusting the position (focus position) of the wafer W in the Z direction and adjusting the inclination angle of the wafer W with respect to the XY plane. Also, XY stage 1
4 is measured by an external laser interferometer 54W via a movable mirror 52W fixed on a Z tilt stage 58, and the measured value of the laser interferometer 54W is
0 is supplied.

The control system is mainly constituted by a main controller 50 as a control means in FIG. Main controller 50
Is configured to include a so-called microcomputer (or minicomputer) including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, so that the exposure operation can be performed accurately. As described above, for example, synchronous scanning of the reticle R and the wafer W, stepping of the wafer W, exposure timing, and the like are collectively controlled.

[0046] Specifically, the main controller 50, for example, at the time of scanning exposure, in synchronism with the reticle R is scanned at a speed V _R in via the reticle stage RST + Y direction (or the -Y direction), as the wafer W via the XY stage 14 is scanned in the -Y direction with respect to the exposure area 42W (or + Y direction) (the alpha projection magnification to the wafer W from the reticle R) velocity alpha · V _R, the laser interferometer 54R, 54 in total
Based on the measured value of W, the position and speed of reticle stage RST and XY stage 14 are controlled via reticle stage drive unit 48 and wafer stage drive unit 56, respectively. Further, at the time of stepping, main controller 50 controls the position of XY stage 14 via wafer stage driving unit 56 based on the measurement value of laser interferometer 54W. As described above, in the first embodiment, the main controller 50, the laser interferometers 54R and 54W, the reticle stage driving unit 48, and the wafer stage driving unit 56
A stage control system is configured.

In the main control unit 50, the control information TS
Is supplied to the excimer laser light source 16, thereby controlling the light emission timing and the light emission power of the excimer laser light source 16. Further, main controller 50 controls energy rough adjuster 20 and illumination system aperture stop plate 24 via motor 38 and drive device 40, respectively, and further opens and closes movable reticle blind 30B in synchronization with stage system operation information. Control behavior. As described above, in the present embodiment, the main controller 50 also has a role of an exposure controller and a stage controller. Needless to say, these controllers may be provided separately from main controller 50.

Next, the configuration of the exposure control system of the scanning exposure apparatus 10 of the present embodiment will be described with reference to FIG.

FIG. 2 shows components of the scanning exposure apparatus 10 shown in FIG. As shown in FIG. 2, the excimer laser light source 1
6, a laser resonator 16a, a beam splitter 16b, an energy monitor 16c, an energy controller 16d, a high-voltage power supply 16e, and the like are provided.

In FIG. 2, a laser beam emitted in a pulse form from a laser resonator 16a is incident on a beam splitter 16b having a high transmittance and a small reflectance, and a laser beam LB transmitted through the beam splitter 16b is externally transmitted. Injected into. The laser beam reflected by the beam splitter 16b enters an energy monitor 16c composed of a photoelectric conversion element, and a photoelectric conversion signal from the energy monitor 16c is output via a peak hold circuit (not shown).
S is supplied to the energy controller 16d. The unit of the control amount of the energy corresponding to the output ES of the energy monitor 16c is (mJ / pulse). During normal light emission, the energy controller 16d operates the high-voltage power supply so that the output ES of the energy monitor 16c becomes a value corresponding to the target value of energy per pulse in the control information TS supplied from the main controller 50. The power supply voltage at 16e is feedback-controlled. The energy controller 16d also changes the oscillation frequency by controlling the energy supplied to the laser resonator 16a via the high-voltage power supply 16e. That is, the energy controller 16
d sets the oscillation frequency of the excimer laser light source 16 to the frequency instructed by the main controller 50 according to the control information TS from the main controller 50, and the energy per pulse of the excimer laser light source 16 is Control device 50
The feedback control of the power supply voltage of the high-voltage power supply 16e is performed so as to have the value specified by.

Outside the beam splitter 16b in the excimer laser light source 16, a shutter 16f for blocking the laser beam LB in accordance with control information from the main controller 50 is also provided.

Further, when a control table described later is created, the output ES of the energy monitor 16c is supplied to the main controller 50 via the energy controller 16d, and the main controller 50 outputs the output ES of the energy controller 16c.
The correlation between S and the output DS of the integrator sensor 46 is determined. Then, at the time of scanning exposure, the main controller 50 sends predetermined control information TS to the energy controller 16c to cause the excimer laser light source 16 to perform pulse emission,
The output DS from the integrator sensor 46 is integrated for each pulsed illumination light, and the integrated exposure amount at each point on the wafer W is sequentially obtained. Main controller 50 adjusts the transmittance of energy rough adjuster 20 and adjusts the energy per pulse of excimer laser light source 16 so that the integrated exposure amount at each point becomes the set exposure amount for the photoresist on wafer W. Fine adjustment before exposure of the wafer.

Next, an example of an exposure amount control operation in the scanning exposure apparatus 10 configured as described above will be described.

First, a procedure for creating a control table which is a premise of exposure amount control will be described. Here, since the control table is created around the integrator sensor 46,
The unit of the output ES (unit of the energy control amount) of the energy monitor 16c in the excimer laser light source 16 is (mJ / pulse).
Assume e). As described above, the integrator sensor 4
The unit of output DS 6 (unit of energy control amount) is (digi
t / pulse).

Here, the output DS of the integrator sensor 46 is applied to an image plane (ie, an image plane) on the Z tilt stage 58 in FIG.
It is assumed that the output of a reference illuminometer (not shown) installed at the same height as the surface of the wafer has been calibrated in advance. The data processing unit of the reference illuminometer is a physical quantity of (mJ / (cm ² · pulse)). Calibration of the integrator sensor 46 means that the output DS (digit / pulse) of the integrator sensor 46 is obtained by exposing the image on the image plane. To obtain a conversion coefficient or a conversion function for converting into a quantity (mJ / (cm ² · pulse)). This conversion factor,
Alternatively, if a conversion function is used, the integrator sensor 46
Can be measured indirectly from the output DS. Therefore, in the following description, the exposure amount on the image plane indirectly obtained from the output DS of the integrator sensor 46 will be described as the processing amount P (mJ / (cm ² · pulse)) by the integrator sensor 46.

Now, what is to be obtained is the exposure amount on the image plane, that is, the processing amount P (m) of the integrator sensor 46.
J / (cm ² · pulse)) and the output ES (mJ / pulse) of the energy monitor 16c in the excimer laser light source 16. As a precondition for this, it is assumed that the energy E per pulse of the laser beam LB from the excimer laser light source 16 in FIG. 1 is stabilized at a predetermined center energy E ₀ . Also, the transmittance in the energy rough adjuster 20 is set to 100% (open).

Then, the energy E of the laser beam LB
Is changed above and below the center energy E ₀ as follows. However, the number of data used for acquiring correlation data is N _DATA .

E = E ₀ {1 ± (i / N _DATA ) × E _R / E ₀ } (3) where E _R is a necessary energy modulation range,
Typically, E _R / E ₀ is 0.02 to 0.03. In addition, i is an integer, and the value of i is changed in a range of 0 to N _DATA , for example.

Then, by causing the excimer laser light source 16 to perform pulse emission while actually changing the value of i, the value P _i of the processing amount P of the integrator sensor 46 and the value E _i of the output ES of the energy monitor 16c are calculated. To the correlation data (P _i ,
Record as E _i ). One data may be a result of one pulse, an average value of a plurality of pulses, or any data as long as it is data measured simultaneously.

FIG. 3 shows the correlation data (P _i , E _i ) thus obtained. In FIG. 3, the horizontal axis represents the processing amount value P _i of the integrator sensor 46, and the vertical axis represents the output value E _i of the energy monitor 16c. Then, for example, the correlation data of FIG. 3 is interpolated to obtain the processing amount P (mJ / (cm ² · pul) of the integrator sensor 46.
se)) to the output ES (mJ / pu) of the energy monitor 16c.
1se) or a conversion coefficient for obtaining the output ES from the processing amount P, and the conversion function f (P) or the conversion coefficient is used as a control table. 1 in the memory 51. Thereafter, the main controller 50 can accurately calculate the corresponding output ES of the energy monitor 16c based on the control table and the processing amount P of the integrator sensor 46.

In the following description, for simplicity, the correlation between the integrator sensor 46 and the energy monitor 16c is very linear, and the correlation data (P _i , E _i ) is as shown by the solid straight line in FIG. It is represented by a linear function, the offset of which can be regarded as 0, and the slope of which is expressed by a conversion coefficient β
It can be treated as That is, it is assumed that the output ES (mJ / pulse) of the energy monitor 16c can be calculated from the following equation using the processing amount P (mJ / (cm ² · pulse)) of the integrator sensor 46 and the conversion coefficient β.

ES = β · P (4) Then, main controller 50 obtains a conversion coefficient β from the correlation data of FIG. 3 by, for example, least squares approximation, and stores this conversion coefficient β as a control table in memory 51. Remember. This completes the creation of the control table.

Next, with respect to the basic exposure control sequence of the scanning exposure apparatus 10 of the present embodiment, the main controller 5
A description will be given with reference to the flowchart of FIG. The energy rough adjuster 2 for the laser beam LB from the excimer laser light source 16
Since the transmittance based on 0 may be simply set so that the number of exposure pulses is equal to or greater than the required number of exposure pulses, the following description focuses on the fine modulation operation of the energy of the laser beam LB.

First, the quantities used in the following description are defined as follows.

(A) S ₀ : Exposure amount (set exposure amount) to be given to the photoresist on wafer W set by the operator. (B) N: pulse number (exposure pulse number) of the pulse illumination light IL irradiated per one point on the wafer. (C) p: average pulse energy density (mJ) on the image plane measured indirectly by the integrator sensor 46 before exposure
/ (Cm ² · pulse)). (D) A _t: target error (exposure amount target value precision) of the average exposure amount error in each shot area on the actual wafer for the set exposure amount. (E) P _t : Set pulse energy (mJ / (cm ² · pulse)) based on the integrator sensor 46. (F) _Et : Excimer laser light source 16 is the main controller 50
Set value of laser beam LB received from (mJ /
pulse). That is, the following equation is established corresponding to equation (4). E _t = β · P _t (5)

(G) V _max : The maximum scanning speed of the XY stage 14 (mm / s). (H) N _min : minimum number of exposure pulses per point. (I) Ws; effective exposure slit width (m
m). (J) f _max : the actual maximum oscillation frequency (Hz) of the excimer laser light source 16.

As a precondition, the neutral value of the laser oscillation frequency f is assumed to be f ₀ . f ₀ is calculated by the following equation. This is the same as the fixed oscillation frequency in the conventional exposure amount control.

F ₀ = V _max × N _min / Ws (6) In the present embodiment, f ₀ <f _max and f ₀ <f <f
It is assumed that the oscillation frequency can be modulated in the range of _max .

It is assumed that the transmittance of the energy rough adjuster 20 is designed so that the discrete transmittance becomes a geometric progression in order to minimize the exposure time over the entire set exposure amount.
Assuming that the common ratio is r, in the present embodiment, r <f ₀ / f
_Let it be _max .

The normal exposure control sequence is as follows.

First, in step 100 of FIG. 4, the process waits for the operator to set the set exposure amount S _O via the input / output device 62 (see FIG. 1) such as a console, and then sets the set exposure amount S _0. If that, the process proceeds to the next step 101, set in the center energy E _O energy setpoint E _t per pulse of the laser beam LB in accordance with the set exposure amount S _0.

In the next step 102, the excimer laser light source 16 is made to emit pulses a plurality of times (for example, several hundred times), and the output of the integrator sensor 46 is integrated to indirectly average the pulse energy on the wafer W. The density p (mJ / (cm ² · pulse)) is measured. This measurement is performed, for example, in a state where the reticle movable blind 30B is driven to completely close its opening, and the illumination light IL is prevented from reaching the reticle R side. Of course, it may be performed in a state where the XY stage 14 is driven to retract the wafer W.

In the next step 103, the number N of exposure pulses is calculated from the following equation. N = cint (S0 _/ p) (7) Here, the function cint represents the rounding of the value of the first digit after the decimal point.

In the next step 104, the number of exposure pulses N
Is greater than or equal to the minimum number N _{min of} exposure pulses for obtaining the required exposure amount control reproduction accuracy. here,
The minimum exposure pulse number N _min is a value obtained based on, for example, the ratio δp / p of the pulse energy variation (3σ value) δp measured in advance and set as a device constant to the average pulse energy density p.

If the determination at step 104 is denied, that is, if the number N of exposure pulses is smaller than the minimum number Nmin of exposure pulses, the _routine proceeds to step 105, where the energy coarse controller 20 of FIG. After selecting and setting the transmittance closest to S ₀ / (N _min × p) from among the transmittances that can be set by the ND filter and satisfying N ≧ N _min , The processing is performed again, and if the determination in step 104 is affirmed in this way or if the determination in step 104 is affirmed from the beginning (if N ≧ N _min ), step 10
6, the actual measurement value A of the exposure target value accuracy is obtained from the following equation.
Calculate _tgt .

[0076] _{A tgt = ABS (1-pN} / S 0) ...... (8) where the function ABS is a function for obtaining the absolute values.

In the next step 107, it is determined whether or not fine modulation of the pulse energy in the excimer laser light source 16 is necessary, that is, the actual measurement value _Atgt of the exposure target value accuracy is _{equal to} or more than the exposure target value accuracy At described above. It is determined whether or not. When the judgment is negative, that is, when the measured value A _tgt is smaller than the exposure amount target value precision A _t is
In step 109, the laser oscillation frequency f is calculated by the following equation with the scan speed V = the maximum scan speed (V _max ).

F = int (V _max × N / Ws) (9) Here, the function int (a) represents the largest integer not exceeding the real number a.

[0079] On the other hand, if the determination in step 107 is affirmative, i.e., if it is A _tgt ≧ A _t because fine modulation of the pulse energy is needed, the process proceeds to step 108. In step 108, first calculates the set relative to the integrator sensor 46 by the following equation pulse energy ^{_{P t (mJ / (cm 2}} · pulse)). P _t = S ₀ / cint (S ₀ / p) (10)

Next, the energy set value E _t (mJ / pulse) of the laser beam LB at the excimer laser light source 16 is calculated from the equation (5) using the conversion coefficient β held as a control table in the memory 51. and, after supplying the energy setpoint E _t to the energy controller 16d, the process proceeds to step 109 to calculate the laser oscillation frequency f as the scan speed V = scan fastest as the (V _max).

In the next step 110, the laser oscillation frequency f calculated above is the maximum oscillation frequency f _{max of the} laser.
It is determined whether or not: When the judgment is affirmative, the process proceeds to step 111, the laser oscillation frequency scanning target velocity (scanning speed) and sets the value calculated above to scan fastest V _max via the energy controller 16d Set. On the other hand, if the determination in step 110 is negative, step 11
Move to 2. In this step 112, it is impossible to set the laser oscillation frequency calculated above. Therefore, after setting the laser oscillation frequency f to the maximum oscillation frequency f _max via the energy controller 16d, the process proceeds to step 113, where the scan speed is set. V is set based on the following equation.

V = Ws × f _max / N (11) In step 114, exposure is performed under the set conditions (V, f, P _t ) determined in the steps up to that point.

FIG. 5 shows the relationship between the set exposure amount (S ₀ ) and the exposure time per point (T _exp ) in the exposure amount control sequence according to the flowchart of FIG. 4 described above. In FIG. 5, a solid line shows the case of the present embodiment, and a dotted line shows a conventional case for comparison.

As is apparent from FIG. 5, according to the present embodiment, in the region corresponding to the high-sensitivity resist (the region of the set exposure amount S ₀ ≤ PN _min · (f _{max /} f ₀ )), the energy is roughly adjusted. The exposure can always be performed at the maximum scanning speed (V _max ) (independent of the value of the set exposure amount S ₀ ) without being affected by the discrete dimming rate of the detector 20, and the exposure time (T _exp ) Is minimized. Further, a region corresponding to the low-sensitivity resist (set exposure amount S ₀ > PN _min · (f _{max /} f ₀ ))
But the region), to become exposed at the maximum oscillation frequency f _{ma x} with the laser, the gradient of the dotted line showing a conventional example ∂T / ∂N
= 1 / f ₀ and the gradient ΔT / ΔN of the solid line indicating the present embodiment.
As is clear from comparison with = 1 / _fmax , the exposure time is shortened. That is, it is possible to obtain the maximum as the throughput of the set exposure area in a wide range. Also, the range of the set exposure amount that can be exposed at the highest scanning speed is S ₀ = PN
_min to PN _min · (f _{max /} f ₀ ).

Further, in this embodiment, since the pulse energy of the excimer laser light source 16 is finely modulated, the exposure amount of the laser beam LB to the wafer W can be controlled at high speed and with high accuracy. Thus, a desired integrated exposure amount can be obtained.

Incidentally, the exposure amount control sequence described above exerts a greater effect in the case of an illumination condition with a low image plane illuminance. An illumination optical system that does not reduce the energy transmission efficiency has been proposed for the power loss when the illumination condition is changed by the illumination system aperture stop plate 24 or the like. However, a complete system in which the difference between the illumination conditions is zero is proposed. Is difficult to achieve, and a difference between illumination conditions of illuminance (average pulse energy) is inevitable.

Here, as an example, the efficiency with respect to the standard illumination condition in which the average pulse energy is maximized is E (E <1).
An example in which the exposure amount control sequence of the present embodiment exerts a greater effect will be described with reference to FIG. In FIG. 6, it is assumed that an attenuator (modulator) whose transmittance is continuously variable is used to simplify the description.

Under the standard illumination condition in the conventional sequence, as shown in case 1 in FIG. 6, the minimum exposure time per point under the illumination condition is (Ws / V _max ) = (N
_min / f ₀ ), and the maximum exposure amount that can be exposed in the minimum exposure time can be expressed as PN _min . On the other hand, under the illumination condition of the efficiency E, the maximum exposure amount that can be exposed in the minimum exposure time is EPN _min as shown in a case 2 in FIG. Overall throughput was not good.

[0089] In contrast, when the sequence of this embodiment is adapted to light conditions in the efficiency E, as shown in case 3 of FIG. 6, the minimum exposure time is Ws / V _max,
Although not different from the case of the conventional example, the maximum set exposure amount S ₀ that can be exposed in the minimum exposure time is EPN _min × (f _max / f
₀ ), which is the maximum set exposure amount S ₀ = under the standard illumination condition in the conventional sequence shown in Case 1.
Increased by PN _min . This is because, in the present embodiment, the effective illuminance can be increased by increasing the laser oscillation frequency (repetition frequency), and the decrease in the average pulse energy due to the change in the illumination conditions can be compensated. As described above, according to the above sequence, the exposure time is shortened in the range where the oscillation frequency f can be modulated (EPN _min ≦ S ₀ <EPN _min (f _max / f ₀ )) under the illumination condition of low illuminance, and the low sensitivity Throughput is improved throughout the area.

In the above embodiment, the case where the pulse energy of the excimer laser light source 16 is finely modulated has been described. However, the present invention is not limited to this, and the energy fine modulation may be performed instead or together with this. Of course, the pulse energy may be finely modulated using an energy fine modulator as shown in FIGS. 11A and 11B described above. In this case, the fine modulator is arranged, for example, on the optical path of the laser beam LB between the energy rough adjuster 20 and the fly-eye lens 22 in FIG. This is controlled by main controller 50 so that the integrated exposure amount is obtained.

<< Second Embodiment >> Next, a second embodiment of the present invention will be described with reference to FIGS. Here, the same reference numerals are used for the same or equivalent components as those in the first embodiment, and the description thereof will be simplified or omitted.

FIG. 7 schematically shows the configuration of a scanning exposure apparatus 70 according to the second embodiment. The point of performing fine modulation of the pulse energy using the energy fine modulator is that the scanning exposure apparatus 70 finely modulates the output pulse energy itself of the excimer laser light source 16.
This is different from the scanning exposure apparatus 10 of the embodiment.

For this reason, in this scanning type exposure apparatus 70,
As shown in FIG. 7, an energy fine modulator 21 is provided on the optical path of the laser beam LB between the rough energy adjuster 20 and the fly-eye lens 22. As the energy fine modulator 21, for example, the above-described double grating type fine modulator shown in FIG.
An energy filter comprising two optical filter plates whose transmittance is finely adjusted according to the respective incident angles, and a drive device for adjusting the crossing angle of the two optical filter plates within a predetermined range as shown in FIG. Fine modulators can be used. The fine control amount _TF by the energy fine modulator 21 is controlled by the main controller 50.

As the energy fine modulator 21, for example, an acousto-optic modulator utilizing Raman-Nass diffraction (Debye-Shears effect) or the like is used, and by controlling the modulation state of this acousto-optic modulator, the amount of transmitted light can be increased. May be changed continuously.

FIG. 8 shows, as a straight line Q, the relationship between the amount of control of the driving device (not shown) in the energy fine modulator 21 from the outside and the amount of change in transmittance. In FIG. 8, the transmittance obtained by dividing the light amount of the emitted laser beam by the light amount of the incident laser beam is defined as a fine adjustment amount _TF . In the present embodiment, the adjustment range of the fine adjustment amount _TF is a continuous range from a predetermined minimum value _Tmin to a maximum value _Tmax , and the control amount for the internal driving device is set to a central value (neutral point). by fine metering T _F is adjusted to the center value T ₀ of the minimum value T _min and a maximum value T _max. Further, when the energy fine modulator 21 is reset, the control amount is set to the neutral point, and the fine adjustment amount T
_F is set to the median T ₀ .

The configuration of the other parts is the same as that of main controller 50.
The configuration is the same as that of the scanning exposure apparatus 10 of the first embodiment except that the control algorithm of the CPU is different.

Next, with respect to the basic exposure control sequence of the scanning type exposure apparatus 70 of the present embodiment, the main controller 5
9 and 10 showing the control algorithm of the CPU within 0
This will be described with reference to the flowchart of FIG. Note that the transmittance of the laser beam LB from the excimer laser light source 16 by the energy rough adjuster 20 may be simply set so that the number of exposure pulses is equal to or more than the required number of exposure pulses. The following description focuses on the fine modulation operation described above.

The exposure amount control in this embodiment is performed by a pulse count method in each shot area, but a predetermined energy modulation is performed between shot areas.

First, in step 201 of FIG. 9, for example, center coordinates (exposure positions) of a number of shot areas to be exposed on the wafer W by the operator via the input / output device 62 (see FIG. 7) such as a console. The movement distance (scan length) L of the wafer W in the scanning direction when performing exposure to each shot area, and the target integrated exposure amount (set exposure amount) S ₀ to be irradiated per point on the wafer W (set exposure amount) S ₀ ( mJ / cm ² )
Wait for setting etc. Then, when the set exposure amount S _{0 and the} like are set, the process proceeds to the next step 202, where the excimer laser light source 16 performs pulse emission a plurality of times (for example, several hundred times) to integrate the output of the integrator sensor 46. Indirectly, the average pulse energy density p (mJ / (cm ² · pulse)) on the wafer W is measured.
This measurement is performed, for example, in a state where the reticle movable blind 30B is driven to completely close its opening, and the illumination light IL is prevented from reaching the reticle R side. Of course, X
The operation may be performed in a state where the Y stage 14 is driven to retract the wafer W. When measuring the above average pulse energy density, the ratio δP / p of the value (variation) δP of three times (3σ) the standard deviation of the pulse energy of the laser beam LB to the average pulse energy density p may be obtained. It is possible.

In the next step 203, the number N of exposure pulses is calculated in the same manner as in step 103 described above.

Following the calculation of the number N of exposure pulses, although not shown, the CPU in the main control device 50 has, for example, a variation (3σ value) δP in pulse energy measured in advance and set as a device constant. Based on the ratio δP / p to the average pulse energy density p, the minimum number N _{min of} exposure pulses required to suppress the variation of the integrated exposure amount within each shot area on the wafer W within a predetermined allowable value.
Ask for. Note that δP / p obtained in step 202 above
The minimum number of exposure pulses N _min may be obtained based on In the method of sequentially exposing the pulse light from one excimer laser light source 16 as in this embodiment, the distribution of the integrated exposure amount S per point on the wafer is, for example, as disclosed in
As disclosed in JP-A-250402, a normal distribution having an average value of Np and a value of 3σ of N ^1/2 · δP is obtained. Further, if the reproducibility of the integrated exposure amount in each shot area on the wafer W is A ₀ and the reproducibility of the integrated exposure amount required at each point on the wafer W is A _rep , The minimum number N _min of exposure pulses required to keep the reproducibility of the exposure amount within the _region A _rep is determined so as to satisfy the following condition.

N _min ≧ [(δP / P) ² / A ₀ ] ² (12) In the next step 204, the exposure pulse number N calculated in the above step 203 is used to obtain necessary exposure amount control reproduction accuracy. _Is determined to be not less than the minimum exposure pulse number _Nmin .

If the determination in step 204 is denied, that is, if the number N of exposure pulses is smaller than the minimum number Nmin of exposure pulses, the _routine proceeds to step 205, where the energy coarse controller 20 of FIG. After selecting and setting the transmittance closest to S ₀ / (N _min × p) from among the transmittances that can be set by the ND filter and satisfying N ≧ N _min , the above steps 202 and 203 The processing is performed again, and if the determination in step 204 is affirmed in this way or if the determination in step 204 is affirmed from the beginning (if N ≧ N _min ), step 20 is performed.
Then, the flow goes to 6 to calculate the actual measurement value _Atgt of the exposure target value accuracy in the same manner as in step 106 described above.

In the next step 207, it is determined whether or not fine modulation of the pulse energy is necessary, that is, whether or not the actually measured value _Atgt of the exposure target value accuracy is _{equal to} or greater than the above-described exposure target value accuracy At. I do. When the judgment is negative, that is, when the measured value A _tgt is smaller than the exposure amount target value precision A _t, the process proceeds to step 209, scan speed V = scan fastest to (V _max) as the laser oscillation frequency f It is calculated in the same manner as in step 109 described above. That is, scan speed V = scan maximum speed (V
_The laser oscillation frequency f is calculated by the above-mentioned equation (9) as _max ). Thus, the exposure pulse number N is the minimum exposure pulse N _min by larger amount, is to maintain the scan fastest V _max by increasing the laser oscillator frequency f.

On the other hand, if the determination in step 207 is affirmative, the routine proceeds to step 208, where the fine adjustment amount _TF in the energy fine modulator 21 in FIG. After adjusting the value, the process proceeds to step 209. T _F = S ₀ / (pN) (13)

The fine adjustment amount (transmittance) T _F in the energy fine modulator 21 changes between the minimum value T _min and the maximum value T _max as described above with reference to FIG. maximum value T _max by using the exposure pulse number N _min, and the exposure amount target value precision a _t, and the minimum value T _min can be respectively expressed as follows.

T _max = (N _min +1) (1−A _t ) / N _min (14A) T _min = N _min (1 + A _t ) / (N _min +1) (14B) and the value of the fine amount T _F at the time of reset is set to _{(T max + T min) /} 2, i.e., T _0.

In the next step 210, the laser oscillation frequency f calculated above is the maximum oscillation frequency f _{max of the} laser.
It is determined whether or not: When the judgment is affirmative, the process proceeds to step 211, the laser oscillation frequency scanning target velocity (scanning speed) and sets the value calculated above to scan fastest V _max via the energy controller 16d Set. On the other hand, if the determination in step 210 is negative, step 21
Move to 2. In this step 212, it is impossible to set the laser oscillation frequency calculated above. Therefore, after setting the laser oscillation frequency f to the maximum oscillation frequency f _max via the energy controller 16d, the process proceeds to step 213, where the scan speed is set. V is set in the same manner as in step 113 described above.

Since the initial setting has been performed as described above, in the next step 214 (step 214 in FIG. 10), the pattern of the reticle R is set in the designated shot area on the wafer W by the scanning exposure method with the set exposure amount. Expose the image.

During this scanning exposure, C in the main controller 50
In the PU, the wafer W by the laser beam LB from the excimer laser light source 16 via the integrator sensor 46
The integrated exposure amount on the above shot area is calculated. In this case, since the number of exposure pulses for each point on the wafer W is N, the pulse from the integrator sensor 46 during the scan of the exposure area 42W in FIG. These photoelectric conversion signals are integrated M times for each N pulses (M is an integer of 2 or more) to sequentially calculate an integrated exposure amount S. Thereby, M positions Y _j (j = 1 to M) arranged at substantially equal intervals in the Y direction on the wafer W.
Integrated exposure amount S _j in is calculated. Note that a specific method of calculating the integrated exposure amount _Sj is described in, for example,
Since it is disclosed in -250402 and the like, a detailed description is omitted here.

In the next step 215, M
The average value S _rst of the integrated exposure amounts S _j is calculated, and
The average pulse energy p 'during the exposure is calculated.

S _rst = (S ₁ + S ₂ +... + S _M ) / M (15) p ′ = S _rst / N (16) In the next step 216, the actual value in the exposed shot area is calculated. Target integrated exposure amount S ₀ of average value S _rst of integrated exposure amounts
Target value error ABS (S _rst / S ₀ −
1) is equal to or greater than the above-described exposure amount target value precision A _t. Then, if the determination is affirmative, that is, the target value error if it exceeds exposure amount target value precision A _t, the process proceeds to step 217, calculates a correction amount of exposure required. More specifically, the correction amount _Tadd , which is a value obtained by dividing the corrected exposure amount for each pulse of the laser beam LB by the current exposure amount, is set as follows.

T _add = S ₀ / S _rst (17) In this case, the coarse adjustment amount (transmittance) T _R of the exposure amount in the energy rough adjuster 20 for the shot area where the exposure has been completed,
And fine adjustment amount T _F of the exposure amount in energy fine modulator 21
Is stored in the memory 51 as information of the previous shot area.

Therefore, in the next step 218, it is determined whether or not the value obtained by multiplying the fine adjustment amount _TF of the energy fine modulator 21 by the correction amount _Tadd is within the adjustable range of the energy fine modulator 21. It is determined based on the following equation.

T _min ≦ T _add · _TF ≦ T _max (18) Then, when the equation (18) is satisfied, step 219 is performed.
And then adjusts the fine adjustment amount T _F of the energy fine modulator 21 to T _add ·
After changing to T _F (= T _F ′), step 230
Move to In this step 230, it is determined whether or not a shot area to be exposed remains, and if there is a shot area to be exposed, the process returns to step 214 to determine the fine adjustment amount T _F ′ of the newly set energy fine modulator 21. First, exposure is performed by a scanning exposure method. At this time, the exposure amount because it is corrected based on the actual accumulated exposure amount at the immediately preceding shot area, the integrated exposure amount obtained becomes close to the target integrated exposure amount (set exposure amount) S _0.

On the other hand, if the determination in step 216 is negative, that is, if the target value error ABS (S _rst /
S ₀ when -1) is less than the exposure amount target value precision A _t is directly because there is no need to change the exposure conditions Step 23
The state shifts to 0, and exposure to the next shot area is performed.
Then, when the shot area to be exposed is exhausted, a series of processing of this routine ends.

On the other hand, in step 218,
When the product of the fine adjustment amount T _F and the correction amount T _add is not within the range of the expression (18), the process proceeds to step 220, and the number N of exposure pulses per one point on the wafer W is changed to N ′ in the following expression. change.
The average pulse energy p 'is the actual average pulse energy obtained by the equation (16).

[0118] _{N '= cint (S 0 /} p') ...... (19) Then, in the next step 221, the exposure pulse number N 'after the correction is, whether it is the required minimum number of exposure pulses N _min or more If the determination is negative, that is, if N ′ is smaller than N _min , the energy fine modulator 21 is reset in step 222 and the fine adjustment amount _TF is set to the median value T ₀ , and then FIG. Then, the process returns to step 205 to adjust the coarse adjustment amount of the energy coarse adjuster 20 so that N ′ ≧ N _min, and then returns to step 202.

On the other hand, if the determination at step 221 is affirmative, that is, if N ′ ≧ N _min is satisfied, the routine proceeds to step 223, where the target integrated exposure of the expected integrated exposure amount N ′ · p ′ after correction is performed. the amount target value error is an error with respect to S ₀ is determined based on whether or not larger than the above-described exposure amount target value precision a _t the following equation.

[0120] ABS (N '· p' / S 0 -1)> A t ...... (20) Then, if the determination is affirmative, that is, when the target value error exceeds the exposure amount target value precision A _t is Then, the process proceeds to step 224 to calculate the necessary exposure amount correction amount. Specifically, the fine adjustment amount _TF in the energy fine modulator 21 is changed to the next _TF '.

T _F ′ = T _F · S ₀ / (N′p ′) (21) Then, in the next step 225 to step 229, the same processing as the above-described step 209 to step 213 is performed. That is, the laser oscillation frequency f corresponding to the new exposure pulse number N 'is calculated in the state where the scan speed is set to the highest speed, and if the calculated f is equal to or lower than the laser maximum oscillation frequency _{fmax, the} laser oscillation frequency is calculated via the energy controller. with changing the lasing frequency to, set the scan speed to scan fastest V _max, calculated f
Is larger than the laser maximum oscillation frequency f _max , the laser oscillation frequency is changed to the laser maximum oscillation frequency f _max , and the scan speed V according to f _max and N ′ is set. Thereafter, the operation shifts to step 230 to perform exposure on the next shot area.

On the other hand, if the determination in step 223 is negative, that is, the expected target value error ABS
(N '· p' / S 0 -1) if is equal to or less than the exposure amount target value precision A _t, there is no need to set the energy fine modulator 21 changes, the process proceeds directly to step 225 below, the The laser oscillation frequency and the scan speed are set in the same manner as described above. Thereafter, the flow shifts to step 230 to perform exposure on the next shot area.

As described above, according to the exposure amount control sequence according to the flowcharts shown in FIGS. 9 and 10,
As shown in Steps 215 to 230 (excluding Step 222), in order to obtain exposure stability between shots on the wafer W, the exposure of each shot area is controlled based on the output of the integrator sensor 46. When the integrated exposure amount data (running window data) is acquired through the above operation and the average integrated exposure amount of the immediately preceding shot is out of the allowable range, the energy is calculated based on the integrated exposure amount measured in the shot area exposed immediately before. Fine adjustment amount T in fine modulator 21
_Since the pulse energy is corrected by adjusting _F , the integrated exposure amount for each shot area can be accurately brought close to the target integrated exposure amount.

According to the above embodiment, the average power of the laser light source 16 is increased during the exposure of one wafer W coated with the high-sensitivity resist (in this case, the scanning exposure is performed at the highest scanning speed). When the fluctuation, that is, the power fluctuation corresponding to one pulse, occurs and is out of the fine adjustment dynamic range of the fine modulator 21 (when the judgment of step 218 is denied), the same exposure amount as before the reduction is applied. In order to obtain the same, the number of exposure pulses at one point on the wafer is changed in step 220. For example, even when the change of the number of pulses N → (N + 1) is calculated, the oscillation frequency f of the laser light source 16 is increased in step 225. Shot of (N +
1) Since it is set to be / N times, a desired exposure amount can be obtained without changing the scanning speed as a result. Therefore, even in such a case, the exposure time does not increase and the throughput can be maintained.

The above exposure amount control is repeated until the average pulse energy of the laser beam from the excimer laser light source 16 is actually measured (this is called “energy check”) at step 202. It is.
However, step 221 → step 222 → step 20
5, the coarse adjustment amount T _R in the energy rough adjuster 20 is obtained.
When changing the is the energy check is performed in step 202, the frequency of this change the coarse metering T _R in rough energy adjuster 20 during exposure to the shot area is quite low. The normal energy check is performed at intervals such as every time a wafer is exchanged or each time a wafer lot is exchanged. Therefore, for example, it is not necessary to perform an energy check during the exposure of one wafer, and the throughput of the exposure process (the number of processed wafers per unit time) is kept high in this respect.

In step 215, the average value S _rst of the M integrated exposure amounts S _j (j = 1 to M) is calculated from equation (15). Average value S _rst 'of the integrated exposure amounts S _j (m <M) May be used. Thus, it is possible to perform exposure amount control corresponding to a short-term output fluctuation of the excimer laser light source 16.

Furthermore, in the second embodiment, the energy coarse adjuster 20 and the energy fine modulator 21 are used as pulse energy modulators. However, the present invention is not limited to this. Similarly, it goes without saying that the power (applied voltage) of the excimer laser light source 16 may be controlled. In this case, for example, there is no energy loss of (1−T ₀ ) based on the fine adjustment amount (transmittance) T ₀ in the initial state of the energy fine modulator 21, so that the energy use efficiency is improved as a whole.

In the above embodiment, step 216,
As shown in 217, but to correct the exposure amount when the average value S _rst integrated exposure amount exceeds the allowable value, when the average value S _{rs t} is within the allowable value even each shot area The data of the average value S _rst is continuously accumulated for each exposure to. If the average value S _rst has a tendency to increase or decrease,
The exposure amount may be corrected in advance before the average value _Srst exceeds the allowable value. With such predictive control,
There is an advantage that the number of shot areas where the integrated exposure amount is out of the allowable value is reduced.

Further, in the above embodiment, the exposure amount is modulated via the energy fine modulator 21 or the like during the exposure to each shot area, but the partial integration up to that time is performed during each pulse exposure. The exposure amount may be modulated via the energy fine modulator 21 or the like based on the exposure amount. Thus, the integrated exposure amount in each shot area can be more accurately brought close to the target integrated exposure amount.

[0130]

As described above, according to the first aspect of the present invention, there is provided a scanning exposure method capable of always performing exposure in the shortest time regardless of the high sensitivity area and the low sensitivity area. .

According to the second aspect of the present invention, exposure can always be performed in the shortest time in a high sensitivity region without being affected by the discrete dimming rate of the dimming means, and the low sensitivity can be obtained. It is possible to provide an unprecedented excellent scanning exposure apparatus capable of improving throughput even in a region.

According to the third aspect of the present invention, in a high sensitivity exposure region, when the pulse energy during exposure varies, the desired integrated exposure for the next shot is maintained while maintaining the scanning speed. There is provided a scanning exposure method capable of performing a quantitative exposure.

According to the fourth aspect of the present invention, particularly in a high sensitivity exposure area, when the pulse energy during exposure varies, the desired integrated exposure for the next shot is maintained while maintaining the scanning speed. It is possible to provide an excellent scanning type exposure apparatus capable of performing exposure to obtain an amount.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a configuration of a scanning exposure apparatus according to a first embodiment.

FIG. 2 is a block diagram schematically showing a configuration of an exposure amount control system of the apparatus of FIG.

FIG. 3 is a diagram illustrating an example of correlation data between a processing amount of an integrator sensor and an output of an energy monitor.

FIG. 4 is a flowchart illustrating an exposure amount control algorithm of a CPU in a main control device according to the first embodiment.

FIG. 5 is a diagram showing a relationship between a set exposure amount (S ₀ ) and an exposure time per point (T _exp ) together with a comparative example in an exposure amount control sequence according to the flowchart of FIG.

FIG. 6 is a diagram for explaining an example in which the exposure amount control sequence of FIG. 4 exerts a greater effect by taking an illumination condition where the efficiency with respect to the standard illumination condition is E (E <1).

FIG. 7 is a view schematically showing a configuration of a scanning exposure apparatus according to a second embodiment.

FIG. 8 is a diagram illustrating a relationship between a control amount from outside of a driving device in an energy fine modulator according to a second embodiment and a change amount of transmittance.

FIG. 9 is a flowchart illustrating a part of an exposure amount control algorithm of a CPU in a main control device according to a second embodiment.

FIG. 10 is a flowchart illustrating the remaining part of the exposure control algorithm of the CPU in the main control device according to the second embodiment.

11A and 11B are diagrams each showing an example of an energy fine modulator, and FIG. 11C is a diagram showing an example of an energy coarse modulator.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Scanning exposure apparatus 14 XY stage (substrate stage) 16 Excimer laser light source (pulse laser light source) 16d Energy controller (frequency changing means) 20 Energy rough adjuster (darkening means) 46 Integrator sensor (energy measuring means) 48 reticle stage Drive unit (part of stage control system) 50 Main controller (part of stage control system, control means) 54R Laser interferometer (part of stage control system) 54W Laser interferometer (part of stage control system) 56 Wafer stage driving unit (part of stage control system) 70 Scanning exposure apparatus R Reticle (mask) W Photosensitive substrate PL Projection optical system RST Reticle stage (mask stage)

Claims (4)

[Claims] An illumination area on a mask is illuminated by a pulsed light from a pulse laser light source, and a pattern formed on the mask is scanned while the mask and the photosensitive substrate are relatively scanned with respect to a projection optical system. A scanning exposure method for sequentially projecting and exposing on a photosensitive substrate, comprising: a step of measuring an average pulse energy of pulsed light from the pulse laser light source; and a step of measuring a relationship between a set exposure amount and the measured average pulse energy. In accordance with the determined number of exposure pulses per point, during the scanning exposure, the pulse laser is used to maintain at least one of a maximum scanning speed between the mask and the photosensitive substrate and a maximum oscillation frequency of the pulse laser light source. Controlling the oscillation frequency of the light source. 2. A predetermined illumination area on a mask is illuminated by pulsed light from a pulsed laser light source, and a pattern formed on the mask is scanned while the mask and the photosensitive substrate are relatively scanned with respect to a projection optical system. What is claimed is: 1. A scanning exposure apparatus for sequentially projecting and exposing on a photosensitive substrate, comprising: a mask stage holding the mask and movable in a predetermined scanning direction; and a substrate holding the photosensitive substrate and movable at least in the scanning direction. A stage control system for relatively scanning the mask stage and the substrate stage with respect to the projection optical system at a predetermined speed ratio; frequency changing means for changing an oscillation frequency of the pulse laser light source; Dimming means for dimming the pulsed light from the light source; and an average of the pulsed light from the pulsed laser light source which is dimmed by the dimming means. Energy measuring means for measuring the pulse energy; the maximum scanning speed of the two stages by the stage control system and the pulse laser in accordance with the number of exposure pulses per point determined by the relationship between the set exposure amount and the average pulse energy. A control unit for controlling the frequency changing unit so as to maintain at least one of a maximum oscillation frequency of the light source. 3. A mask formed by illuminating a mask with pulsed light from a pulsed laser light source and relatively scanning the mask and the photosensitive substrate with respect to a projection optical system. In a scanning exposure method of sequentially projecting and exposing a shot area, each time the mask pattern is exposed to each shot area on the photosensitive substrate, an average pulse energy of the pulse laser light source is detected and an integrated exposure amount up to that is detected. When the average pulse energy of the pulse laser light source fluctuates, the oscillation frequency of the pulse laser light source is changed based on the integrated exposure amount of the immediately preceding shot area to secure the required number of exposure pulses per point. A scanning exposure method characterized by controlling. 4. A mask formed by illuminating a mask with pulsed light from a pulsed laser light source and scanning the mask and the photosensitive substrate relative to a projection optical system while simultaneously scanning a plurality of patterns formed on the photosensitive substrate. A scanning type exposure apparatus for sequentially projecting and exposing a shot area, comprising: frequency changing means for changing an oscillation frequency of the pulse laser light source; and energy measuring means for measuring an average pulse energy of pulse light from the pulse laser light source; Each time the mask pattern is exposed to each shot area on the photosensitive substrate, the average pulse energy of the pulse laser light source is detected and the integrated exposure amount up to that is calculated, and the average pulse energy of the pulse laser light source is calculated. When it fluctuates, secure the required number of exposure pulses per point based on the integrated exposure amount of the immediately preceding shot area Order, scanning exposure apparatus and a control means for controlling the frequency changing means.