JPH0312975A - Laser oscillator and exposure device using same - Google Patents

Abstract

PURPOSE:To obtain a laser beam having a stable oscillation wavelength by detecting variation of a monitoring means itself, obtaining monitor output to correct an amount corresponding to the variation, and detecting an wavelength corresponding to the wavelength of the laser oscillation. CONSTITUTION:A reference light source 17 is provided that lets reference light of a stable wavelength strike into a wavelength-monitoring means 2-4, 7 with almost the same axis as that of a part of a laser beam. The wavelength- monitoring means 2-4, 7 is provided with monitoring etalons 2 which make the first interference fringe corresponding to the wavelength of the laser beam at a position distant from the center line and besides the second interference fringe corresponding to the wavelength of the reference light between the center line and the first interference fringe, and a photodetector 7 detecting the relative positional relation between the first and the second interference fringes photoelectrically. Then, a processing device 13 detects a change of the wavelength of the laser beam according to this relative positional relation. And, this makes it possible to obtain a laser beam having a stable wavelength.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a laser oscillation device used in a precision exposure device such as a microfabrication device or a semiconductor manufacturing device, and particularly relates to a device for stabilizing the wavelength of laser oscillation light. The present invention relates to a laser oscillation device equipped with the present invention.

[Prior Art] Optical systems used in precision exposure equipment are designed to be optimal for specific wavelengths, and are also corrected for various aberrations. An illumination optical system (light source) that stably supplies light is required. In particular, it has been proposed to use a laser light source in the ultraviolet region for exposure equipment and the like, focusing on the energy of the illumination light, and efforts are being made to put it into practical use.

As a laser light source used in this type of exposure apparatus, an excimer laser having a wavelength narrowing element is known. In a laser oscillation device equipped with a wavelength selection element (band narrowing element) in a laser resonator, the wavelength selection band of the wavelength selection element fluctuates due to the effects of heat of the emitted laser light, vibration of the device, etc. As a result, the laser oscillation wavelength may vary.

For this reason, as a means for monitoring the oscillation wavelength of a laser oscillation device, for example, the laser light transmission characteristics of an etalon are used to extract a part of the laser oscillation output light and make it enter a monitoring etalon with a predetermined divergence angle. A wavelength monitor means may be used to measure the wavelength of laser oscillation light from interference fringes generated on a light receiving element by transmitted light.

In the conventional laser oscillation device N using this type of device,
The wavelength of the laser oscillation light and its changes are measured by forming the above-mentioned interference fringes on, for example, a one-dimensional grid and measuring the positions and changes in the positions of these fringes.

That is, the wavelength of the laser oscillation light and the amount of change thereof are detected from the position information of the interference fringes obtained from the photo array,
Based on the detection results, a predetermined control signal is sent to the drive means for changing the wavelength transmission band of the wavelength selection element in the laser resonator, such as an etalon or a grating 1 prism, to oscillate the laser oscillation light. The wavelength is stabilized.

Here, the measurement of the laser oscillation wavelength, etc. is performed at the time of starting up this laser oscillation device and periodically during the exposure operation during operation of the exposure device. It is necessary to obtain illumination light of a stable wavelength throughout the exposure work period.

[Problem to be solved by the invention] However, in the conventional technology as described in Section 2, the wavelength monitoring means itself is affected by thermal deformation caused by the laser beam, for example, the position and interval of the interference fringes fluctuate. This results in a different monitor output that does not correspond to the actual laser oscillation wavelength.
In some cases, errors may occur in the measured values.

For this reason, even when the laser oscillation wavelength does not change, the detection output signal of the monitoring means fluctuates, and the laser oscillation wavelength is controlled by the monitor output having a different value that does not correspond to the actual laser oscillation wavelength. There is a problem that may cause malfunction.

Roughly speaking, when the laser oscillation wavelength fluctuates, the monitor output corresponding to the fluctuating wavelength is added to the output due to the fluctuation of the monitoring means itself, resulting in a monitor output containing errors. there were.

In addition, in exposure equipment that performs exposure IA processing using the output laser light from such a laser oscillation device, periodic calibration is required to monitor the wavelength of the output laser light even during exposure work. However, there is a problem in that during that time, the original exposure work cannot be done.

Furthermore, if the exposure operation is temporarily stopped during this monitoring, a problem arises in that the oscillation wavelength cannot be accurately measured due to changes in temperature and the like over time.

The present invention has been made in view of these conventional problems, and it enables the laser oscillation wavelength to always match the set target value.
In addition to obtaining a laser oscillation device that can obtain output laser light with a stable wavelength, when this laser oscillation device oscillates pulsed laser light, it is possible to use the pulsed laser light for calibration operation when using the pulsed laser light in an exposure device. The purpose is to obtain an exposure device that does not require special time or at all.

[Means for Solving the Problems] In view of the second object, the present invention comprises a wavelength selection element disposed on an optical path within a laser resonator, and a driving means for changing the selected wavelength of the wavelength selection element. , wavelength monitoring means for inputting a part of the output laser light from the resonator and outputting a detection signal according to a change in wavelength of the laser light; and control means for controlling the driving means based on the detection signal. The laser oscillation device includes a reference light source that makes a wavelength-stable reference light enter the wavelength monitoring means substantially coaxially with a portion of the laser beam, and the wavelength monitoring means and the reference light are incident along a predetermined center line, a first interference fringe corresponding to the wavelength of the laser beam is created at a position away from the center line, and a first interference fringe corresponding to the wavelength of the reference light is created at a position away from the center line. a second interference fringe for forming a second interference fringe between the center line and the first interference fringe; and a light receiving element for photoelectrically detecting the relative positional relationship between the first and second interference fringes. , the wavelength change of the laser beam is detected from this relative positional relationship.

Here, the wavelength monitoring means has a lens element that adjusts the laser beam and the reference light that are incident on the monitoring etalon to a predetermined degree of divergence or convergence, and this lens element allows the first interference The fringe and the second interference fringe may be formed on an annular zone centered on the center line, and the light receiving element may be arranged to receive light from a diameter portion of the first or second interference fringe. .

Further, a wavelength selection element is disposed on the optical path within the laser resonator, and a part of the pulsed laser light outputted from the resonator at the first repetition period is incident thereon to respond to the wavelength change of the pulsed laser light. A wavelength monitor system that outputs a detection signal allows
In an exposure apparatus that includes a laser oscillation device that changes the selected wavelength of the wavelength selection element and sequentially exposes a plurality of substrates using the output pulsed laser light, a reference light having a stable wavelength is input to the wavelength monitor system. In the process of sequentially processing the plurality of substrates, if the exposure of the substrates to the pulsed laser light is interrupted for a predetermined period of time or more, the pulsed laser light is oscillated at a first repetition period. at least one of the pulsed laser beams emitted at the second repetition period while the exposure of the pulsed laser beam to the substrate is interrupted; A pulse is made incident on the wavelength monitoring system, a relative change in wavelength between the wavelength of the reference light and the wavelength of the pulsed laser light is detected (1), and the selected wavelength of the wavelength selection element is controlled based on this detection result. and second control means.

Here, the exposure apparatus has a mechanism for sequentially stepping a plurality of regions of the substrate to the irradiation position of the pulsed laser beam, and the first control means is configured to control whether or not the exposure of the pulsed laser beam is interrupted. It is preferable that the predetermined time be set longer than the time required for stepping.

[Function] Since the laser oscillation device according to claim (1) of the present application is configured as described above, the second interference signal corresponding to the wavelength of the stable reference light that is used in the monitoring means is Fringes are formed inside the first interference fringe, and the relative positional relationship of these interference fringes is detected.

Here, drying with a monitor etalon? ! The spacing between the fringes is determined by the wavelength of the human silk light and the etalon gap of the monitoring etalon, so the etalon cap or the wavelength of the incident light or its variation can be measured from the positional spacing of the interference fringes and the amount of movement thereof. Ru・.

In other words, if the amount of variation in the monitoring means itself due to the laser beam appears as a gap change in the monitoring etalon, the amount of variation in the monitoring means itself, that is, the amount of variation in the monitoring etalon, can be determined from the position of the second interference fringe and its movement amount. When detecting the gap or the amount of change thereof, and detecting the amount of change in the laser oscillation wavelength calculated from the position of the first interference fringe, the amount of movement thereof, etc., the influence of the amount of change of the monitoring means itself is corrected. Based on a signal corresponding to a change in the true laser oscillation wavelength from the etalon gap, a driving means for changing the selection wavelength of the wavelength selection element in the laser resonator is controlled.

Here, the amount of change in the spacing of the interference fringes with respect to the change in the etalon gap is greater for the inner fringes (fringes closer to the center line of the incident light), so the second interference fringe is compared to the first interference fringe. By forming the cap on the inside of the monitor etalon, it can respond sensitively to changes in the cap of the monitor etalon.

In the laser oscillation device according to claim (2) of the present application, the first and second interference fringes are formed in an annular shape by a predetermined lens element of the wavelength monitoring means.

1 Furthermore, the light-receiving element receives the diameter portions of these interference fringes and detects their intervals.

Therefore, if the center line of the incident light mechanically changes its position (eccentricity) due to fluctuations in the wavelength monitoring means, the position of the entire interference fringe or the photodetector will change, but the diameter of the interference fringe will not change at all. Therefore, accurate wavelength detection is always performed from this light receiving element.

The exposure apparatus according to claim (3) of the present application utilizes the above-mentioned laser oscillation device, and sequentially targets a plurality of substrates using pulsed laser light output from the laser oscillation device at a predetermined first repetition period. It is exposed to light.

In this exposure apparatus, the process of sequentially processing multiple substrates,
For example, when exchanging substrates (wafers or resicles), aligning substrates) - operation, or switching the irradiation position on the substrate, the time during which the exposure of the substrate is interrupted in the sequence of the equipment for a predetermined period of time or more. Using this, the wavelength measurement and control of the laser oscillation light are performed by the second control means in substantially the same manner as described above.

Here, in order to prevent the laser oscillation efficiency of the laser oscillation device from decreasing, it is desirable to suppress unnecessary laser emission. For this reason, the first control means controls the oscillation of the pulsed laser light at the first repetition period (for example, a frequency of about 100 to 50011z) when controlling the wavelength monitor, etc.
(e.g. 01~l01l)
(approximately z).

This second repetition period is determined by the temporal characteristics of the stability of the etalon, but it may be a period in which at least one light emission occurs during a predetermined period of time during which the exposure is interrupted; If at least one pulse of laser oscillation is detected by the wavelength monitoring system, the deviation from the absolute value of the laser oscillation wavelength is detected and the oscillation wavelength is corrected.

In the exposure apparatus according to claim (4) of the present application, the exposure apparatus has a mechanism for sequentially stepping a plurality of areas on the substrate to the irradiation position of the pulsed laser beam, and for example, the time required for stepping is If the above-mentioned interruption time is short (for example, 1 second or less), the correction control of the laser oscillation wavelength by the wavelength monitor system is maintained (locked) at the state immediately before it during the stepping operation. It is something to keep.

[Example] Embodiments of the wooden invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of a laser oscillation device according to the invention. In the figure, 1.1' is the rear mirror 8 which has almost 100% reflectance, and the front mirror 1 to which has slight transmittance.
The spectral distribution of excimer laser light oscillated by the laser chamber 14, which is an etalon installed on the optical path within the laser resonator consisting of a mirror 9 and filled with a rare gas/halide such as r-F or Xe-Cl. By transmitting only laser light of a predetermined wavelength, the oscillation wavelength is narrowed. Etalon 1.1'' is etalon driving means 6
By changing, for example, the etalon gap or the tilt angle with respect to the optical axis, the selected wavelength can be shifted. The laser generator 14 emits pulsed light by applying a high-voltage pulse to a discharge electrode, and the pulse interval,
The timing of light emission and the like are controlled by a pulse control section 18.

The laser beam emitted from the front mirror 9 passes through the heem splitter 10, and as the shutter 25 opens and closes,
Mirror 22. A mask 30 having a predetermined circuit pattern is irradiated through an illuminance uniformizing optical system 33 including a fly-eye lens, a speckle reduction element, and the like.

The mask 30 and the wafer 31 are arranged on a plane that is conjugate with respect to the projection optical system 21, and the irradiation laser beam of the narrow band specific wavelength is disposed on a plane that is conjugate with respect to the projection optical system 21. The circuit pattern of the mask 30 is transferred to the wafer 31 by
irradiate a predetermined projection area. The wafer 31 is fixed to a wafer stage 20, and the wafer stage 20 performs exposure by sequentially stepping a plurality of predetermined projection areas of the wafer 31'2 relative to the projected image position of the mask 30. Further, the shutter 25 opens and closes in conjunction with the stepping of the wafer stage 20, wafer exchange, recycle conversion 5, and other operations.

By the way, a part of the laser beam emitted from the Freon mirror 9 is reflected by the hems blitter 1o, attenuated by a predetermined amount by the attenuator 5, and further reflected by the hems blitter 11, and then reflected by the concave lens 3. Monitor etalon 2. The light enters a monitor optical system consisting of a convex lens 4, a light receiving element 7, etc. along the optical axis.

In addition, 17 is a reference light source that emits reference light with a stable absolute wavelength.
The excimer laser beam coaxially makes the reference light beam from the reference light source 17 enter the monitor optical system through the reference light source 17.

In this example, the emission line of an Hg lamp with a narrow spectral width is used, but a reference light source such as a wavelength-stable laser light source such as a Le-Ne laser or a He-Cd laser may also be used. .

In this monitor optical system, light incident on its front axis is appropriately diverged by a concave lens 3 and made to enter a monitor etalon 2. Of this human DJ light, only the light incident at a certain angle fx (divergence angle) is transmitted through the monitor etalon 2 due to an interference phenomenon.

This transmitted light is converged by the convex lens 4 and onto the light receiving element 7 with a diameter corresponding to the wavelength of this transmitted light (incident light).
Annular interference fringes (fringes) 12 consisting of bright lines are formed.

Here, the light receiving element 7 is a one-dimensional image sensor extending in the diameter direction of the fringe or a one-dimensional photo array,
It has a configuration that can detect two or more lights at the same time, and receives fringes with diameters of +2 and 12" according to the wavelengths of the laser oscillation light and reference light, and determines the position and spacing (diameter) of the fringes.
Detect etc.

Reference numeral 13 denotes a processing device of the wavelength monitoring means, which calculates a change in the wavelength of the laser oscillation light based on the detection signal from the light receiving element 7, and detects a change in the wavelength of the laser oscillation light when the wavelength changes from a predetermined setting value (the above-mentioned specific wavelength). controls the tilt angle of the etalon 1.1' via the drive means 6 so as to reduce the amount of variation thereof.

This calculation means will be further explained with reference to FIG.

A detection output signal (serial image signal of n-bit pixels) 41 from the light receiving element 7 is A/D converted and stored in the memory 43 .

The data stored in the memory 43 can be directly accessed by the processing device 13, and this data is used to perform the 7-tri operation.

The light receiving element 7 outputs a TRG signal 47 in synchronization with the output of each pixel, and a conversion start signal 4 of the A/D converter.
8. It is also used to create addresses for the mail order 43 (created within the counter 44).

A programmable timer 45 is also provided which is set by the processing device 13, and this timer 45 generates clock and laser trigger signals.

The clock signal is a signal that sets the self-scanning speed of the light receiving element 7, and can be set to any speed. With this device, the time required for - scans is approximately 20. 48
(msec).

Further, the laser trigger signal is used as an external trigger signal of the laser oscillation device and is sent to the pulse controller 18. This device uses 200 yen, which is necessary for the exposure processing of the exposure device.
(Hz).

In other words, the light emission interval is 5 (msec), and in this period, light is emitted at least four times during one scan on the light receiving element 7.

The light-receiving element 7 used in this device uses a charge storage type so as not to limit the laser oscillation frequency, and is configured to read out the sum of outputs from multiple laser emissions in one scan. In order to obtain a perfect fringe (interference fringe) signal, the output of all pixels must be controlled by the same number of times of light emission. Therefore, a start signal, which is a scan start signal for the light-receiving element 7, is generated by frequency-dividing the laser trigger signal every predetermined number of times of light emission by the frequency dividing circuit 46.

FIG. 4 shows a time chart of the laser trigger signal and scan (clock signal) when the number of frequency divisions is six.

Next, with reference to FIG. 2, the principle of controlling the wavelength change of light according to the fringe position using the monitor optical system used in this embodiment will be explained.

In this figure, the distance (radius) h from the optical axis center to the first-order fringe is given by the following equation.

Therefore, when h and d are measured, λ can be indirectly measured.

Here, if dh) a constant value d. That is, the function h=gcl of the equation (]). (^)...Equation (2) is obtained, and λ can be measured by measuring only 1].

However, if the pulsed laser beam enters the monitor optical system for a long period of time, the monitor etalon 2. Concave lens 3. The convex lens 4 and the metal fitting 0 absorb part of the energy of the pulsed laser beam, for example as heat, and also change the temperature. Optical rigidity is changed by changes in W degree, atmospheric pressure, etc. For example, when the etalon gap d changes, 1] becomes a two-variable function as shown in equation (1).

Here, as shown in the configuration of the present invention, the reference light (wavelength λst
) and a pulsed laser beam (wavelength λex) are input at the same time nJ.

The etalon cap d changes for the reasons mentioned above, but since the wavelength λ is known when focusing on the reference light, it is possible to calculate the changed d by measuring the fringe hst corresponding to this reference light. .

That is, d is considered to be a constant determined for each measurement of the fringe hst in equation (1), and is the fringe h corresponding to the pulsed laser beam. By using d determined here when measuring 8, the laser oscillation wavelength λ can be determined without being affected by characteristic fluctuations of the monitor etalon 2, etc. can always be measured positively.

Furthermore, in this embodiment, the shape of the fringe 12.12 and the positional relationship of the light receiving element 7 carved on the fringe are
The settings were as shown in Figure (8).

Here, within the range of expected wavelength fluctuations of the pulsed laser beam and changes in optical characteristics with the optical elements of the monitoring means, at least the first fringe (innermost one) of both beams is measured as viewed from the optical axis of the monitoring optical system. The focal point f1 of the monitor optical system and the etalon gap d and the wavelength λ of the reference light are selected so that the arrangement of .

As an example where this condition is not met, the reference light source in this embodiment is a base 4 having a longer wavelength than the pulsed laser light (in order to obtain light,
An Hg lamp is used.

Therefore, the primary fringe 12 corresponding to the reference light is formed inside the fringe 12 of the pulsed laser light.

However, when considered from the viewpoint of wavelength measurement in a dither system, there is basically no problem even if the reference light is outside the fringe 12° or the fringe 12.

However, the same wavelength change (or etalon A thickness change)
On the other hand, the shift amount (diameter change) of the inner fringe is larger than the outer side when viewed from the optical axis, and the light receiving element 7
The detection signal from scan star 1 to the vicinity of pixels (PC
Since noise is likely to occur near either end of D, and there is a possibility that the fringe position cannot be accurately measured in this vicinity, in this example, the fringe 12' corresponding to the reference light is It is formed almost concentrically inside the fringe 12.

The two-dimensional optical system of this example set as described above is as follows:
For hunting, the innermost part is the primary fringe 12° due to the reference light, and the outermost part is the primary fringe 12° due to the pulsed laser beam.
This shows a one-to-one correspondence.

In other words, in the processing of the detection output signal from the light receiving element 7, when detecting the etalon cap d, the deviation is good only for the two fringe positions determined by the diameter of the innermost fringe 12'', and the wavelength of the laser light is When measuring, only the two fringe positions determined by the diameter of the outer fringe 12 are targeted.

3 In this way, the light receiving element 7 is connected to the 2t fringe 12, 12' through the center of the light IQb of the monitor optical system (almost coaxial with the optical axis of the desired light), perpendicular to this front axis, and for both people. It is arranged at a position where the diameter of the primary fringe 12.12' of light can be detected.

The reason why it was decided to detect the diameter portion of the fringe is because there is a possibility that the entire fringe may shift due to the influence of, for example, positional deviation of the light receiving element 7 or drift of various optical elements.

In this case, for example, if the configuration is such that only the radius or knitted part of the fringe is detected, a measurement error will occur due to the lift, but if the diameter of the fringe is measured, it will be difficult to detect the entire fringe or the shift. This is because its diameter does not change as long as ~.

If these effects (such as Schiff l-) can be ignored in whole or in part in the monitor system, the method shown in Figure 5 (
11) It is possible to arrange the light-receiving elements 7 as shown in (C), and in this case, a two-tar system can be constructed using shorter light-receiving elements (with a smaller number of pixels).

2/1 Here, Table 1 shows the relationship between each configuration of the light receiving elements in FIGS. 5(8), (B), and (C) and error conditions. In Table 1, Y indicates that there is no problem even if each deviation occurs, and N indicates that only one deviation is allowed.

Table 1 Y, Yes N: None Figure 5 (B) shows the light receiving element 7 arranged so as to monitor only the radius of two fringe 12, 12°, and Figure 5 (C) shows the reference light The fringe 12° of the excimer laser beam allows the diameter to be monitored, and the fringe 12° of the excimer laser beam
The light receiving element 7 is arranged so as to monitor the radius.

The diameter of the primary fringe of the beam for both people is detected from the doublet optical system configured as described above, and the amount of change from the absolute wavelength of the pulsed laser beam and the correction control amount are calculated by the steps described below. It is determined by

The wavelength of the reference light incident on the initial setting monitor optical system is λS T +
− diameter of the next fringe] ST, its natural number m + 11
If s7, then from equation (1), the etalon gap d is expressed as follows.

Here, within the expected range of change in diameter IST, the diameter 1
Cap f as an argument by subdividing sT into minute steps
td(IsA) is stored in memory in advance.

Step 1 Process the detected fringe signal, consider the innermost fringe 12'' as the primary fringe of the reference light, and its diameter as IST, and the outer fringe 12 as the primary fringe of the pulsed laser beam, and calculate its diameter. Let it be Iex.

Step 2 Using the diameter IST obtained in Step 1 as an argument, calculate the corresponding gap amount (1s'r) from table d.

Step 3 Set the target wavelength of the laser oscillation light to λ2. Assuming that the diameter of the primary fringe that C approaches the target wavelength is 1p, and the natural number m corresponding to the −th order fringe is m, , X, then from equation (1), 11. is calculated using the following formula.

Therefore, by using d(+s'r) obtained in step 2, 1. Find out.

Step 4 If the wavelength of the pulsed laser beam is λ, the equation (1) is obtained, and the current laser oscillation wavelength can be measured.

Here, from equation (1), lp>1. In the case of ), it is possible to correct the laser oscillation wavelength.

Through the above steps, it is possible to measure the laser oscillation wavelength with high precision and control the wavelength stabilization, and it is possible to obtain an output pulsed laser beam stabilized to a substantially single absolute wavelength.

Furthermore, by changing λ1 (target wavelength) in the trial calculation formula, it is also possible to obtain pulsed laser light of any wavelength.

The second embodiment is characterized in that the reference light and the laser light are detected simultaneously, but by opening and closing the shutter 15 provided on the optical path of the reference light, the reference light can be detected in a time-divided manner. It is also possible to detect the laser beam and the laser beam separately, which is effective mainly in the case of low-frequency pulsed light emission.

Here, focusing on the N-th pixel that falls on the light receiving element 7, the pulse emission of the laser oscillator, the accumulated charge amount of the light receiving element 7, the scan timing of the light receiving element 7, and the opening/closing time chart of the shutter 15 are shown in the seventh column. Shown in Figure (B). In addition, Figure 7 (A) shows the time difference 1~ when time division is not performed.
Shown below.

In FIG. 7(A), the pulse emission frequency of the laser is 200
Hz, and as mentioned above, the light receiving element 7 detects six pulse emission signals.

Further, in FIG. 7(B), the pulse emission frequency of the laser is 20 Hz, and one pulse emission signal is detected.

In these figures, ■ indicates the timing of pulsed light emission;
■ is the output of the pulsed light emission at the Nth pixel (light receiving element 7
(2) also represents the output of the Hg lamp (the amount of charge stored in the light receiving element 7), (2) represents the scanning timing of the light receiving element 7, and (2) represents the open/closed state of the shutter 15.

Using the time division method as shown in FIG. 7 (If) has the following advantages. Of course, detection is also possible when the fringes of the excimer laser and the reference light are almost overlapped. In this case, there is an advantage that a shorter light-receiving element can be used, and furthermore, the time required for one calculation process can be shortened.

In Figure 7 (B), the pulse emission frequency of the laser is 20H.
Since the case of z has been shown, the detection of the pulsed laser beam and the detection of the reference light are performed alternately. However, when using pulsed light with an even lower frequency, this can usually be handled by detecting the base light and detecting the pulsed laser light only when pulsed light is emitted.

This method can be applied to low-frequency light emission during non-exposure (standby mode 1 to 1), for example, when used as a light source for semiconductor manufacturing equipment.

In the exposure apparatus according to this embodiment, the wafer stage 20
Command signals for all Stellar Pig operations and command signals for opening and closing the shutter 25 for exposure light are sent to the processing device 13 of the wavelength monitoring means, as shown in FIGS. 1 and 3.

The IA control device 13 changes the program in the timer 45 as needed based on these command signals, and changes the cycle of the laser trigger signal during non-exposure periods such as reticle conversion, wafer exchange, alignment, etc. to the period during exposure. Fig. 7 (b)
The wavelength dimmer and its control are performed at the same timing.

1] In the case of the Q-Nistepsher, the stepping operation is completed within one second, so there is no need to specifically activate the wavelength control loop.

However, like wafer exchange, flymen 1~operation, etc.
If the oscillation of the excimer laser is interrupted for more than 1 second, and if there is a wavelength shift or 12-ter system fluctuation during that time, the absolute wavelength of the laser light will change at the moment when the next exposure operation starts. Sometimes it's off.

Therefore, in a sequence period in which laser oscillation is interrupted for a period longer than the stepping time, for example, for a period that causes a problem due to fluctuations in the monitor optical system, the shutter 25 is closed and the laser oscillation is stopped at a frequency of about IHz. Make it a low frequency.

Normally, during exposure operation, laser oscillation is performed at 100 to 20011 z. Then, while monitoring the reference light using the monitor optical system and detecting fluctuations in the monitor etalon 2,
When a 11Z pulse laser is used in a monitor optical system, it is possible to immediately detect a shift in the absolute wavelength of the excimer laser beam and perform wavelength control using the various calculations described above.

Of course, if the stepping time is originally long, or if wavelength fluctuation occurs during the stepping time of about 1 (second), the shutter 25 is closed and at least one pulse of laser oscillation is performed during stepping. Wavelength control can also be performed.

[Effects of the Invention] As explained above, the laser oscillation device according to the invention as set forth in claim (1) of the present application detects fluctuations in the monitoring means 2 and obtains a monitor output corrected by an amount corresponding to the fluctuation amount. As a result, wavelength detection is performed that accurately corresponds to the laser oscillation wavelength, and wavelength control is performed that accurately corresponds to the amount of fluctuation in the true laser oscillation wavelength, so malfunctions due to fluctuations in the wavelength monitoring means are prevented. Furthermore, it is possible to perform accurate control with fewer errors, and the advantage is that the oscillation wavelength and stable laser light can be obtained.

Furthermore, since the interference fringes corresponding to the wavelength of the reference light are formed inside the interference fringes corresponding to the wavelength of the laser beam,
It has been able to respond accurately and sensitively to fluctuations in the monitoring means, improving the stability of the oscillation wavelength of the laser beam.

In addition, since the oscillation wavelength can be monitored at the same time while the laser oscillation device is being driven (laser oscillation), there is no need for calibration as in the past, which has the advantage of improving the throughput of work using this device. be.

The laser oscillation device according to the invention described in claim (2) of the present application has a configuration in which interference fringes are formed on an annular zone and the diameter portion thereof is detected. It also has the advantage of being able to deal with positive radiation, and providing laser light with a stable wavelength even in these cases.

Since the exposure apparatus according to the invention described in claim (3) uses the above-mentioned laser oscillation device, stable wavelength laser light can be used, so there is no effect of defocusing due to wavelength fluctuation, etc. It has the advantage of being able to perform precise exposure work accurately.

Further, since pulsed laser emission is suppressed during non-exposure operation, there is an advantage that the gas life of the laser oscillation device itself can be extended.

In the exposure apparatus according to the invention described in claim (4) of the present application, the non-exposure time that inevitably occurs in the sequence of the exposure apparatus is used to monitor the laser oscillation wavelength and to control the same. This has the advantage of making effective use of the working time and improving throughput.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an exposure apparatus using a laser oscillation device according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a partial configuration of a monitor optical system in the embodiment of FIG. 1. , Figure 3 is an explanatory diagram showing the configuration of the monitor calculation section, etc., and Figure 4 is a diagram showing the timing of the laser oscillation pulse emission and the scanning that falls on the light receiving element in the monitor part. The explanatory diagram shown in Figure 5 shows the fringe and light receiving element on a part of the monitor.
It is a conceptual diagram showing the relative positional relationship, and (8) (
B) and (C) each show a different positional relationship. Figure 6 is an explanatory diagram showing the relationship between the wavelength shift of laser oscillation light and the shift of the fringe corresponding to the wavelength shift. show. FIG. 7(B) shows pulsed light emission from the laser oscillation device. The amount of charge accumulated in the light receiving element 7, the scan timing of the light receiving element 7,
FIG. 7 (Δ) is an explanatory diagram showing a time chart of opening and closing of the shutter 15, and FIG. 7 (Δ) is an explanatory diagram without showing a time chart when time division is not performed.
■ is the pulse emission timing, ■ is the output of the pulse emission at the Nth pixel (the amount of charge accumulated in the light receiving element 7), ■ is the output of the Hg lamp, ■ is the scanning timing of the light receiving element 7, represents the open/closed state of the shutter 15. [Explanation of symbols of main parts] 1.1 etalon, 2 monitor etalon, 3 concave lens, 4 convex lens, 5 attenuator, 6 etalon drive section, 7 light receiving element, 8 laser mirror, 9 output laser (half) mirror, 10.11 Half mirror
11212 Fringe (interference fringe), 13 Processing device, 14
Laser diember, 15 Reference light shutter 17 Reference light source, 20 Wafer stage, 25 Exposure light shutter 6

Claims (4)

[Claims] (1) A wavelength selection element disposed on the optical path within the laser resonator, a driving means for changing the selected wavelength of the wavelength selection element, and a part of the output laser light from the resonator incident thereon to select the wavelength selection element. A laser oscillation device comprising a wavelength monitor means for outputting a detection signal according to a change in the wavelength of laser light, and a control means for controlling the drive means based on the detection signal, wherein the wavelength monitor means has a stable wavelength. The wavelength monitoring means includes a reference light source that makes a reference light incident substantially coaxially with a part of the laser light, and the wavelength monitoring means detects when the part of the laser light and the reference light are incident along a predetermined center line. A first interference fringe corresponding to the wavelength of the laser beam is created at a position away from the center line, and a second interference fringe corresponding to the wavelength of the reference light is created.
a monitoring etalon that creates interference fringes between the center line and the first interference fringes, and a light receiving element that photoelectrically detects the relative positional relationship between the first and second interference fringes, A laser oscillation device characterized in that a change in the wavelength of the laser beam is detected from the relationship. (2) The wavelength monitoring means adjusts the laser beam and the reference light incident on the monitoring etalon to a predetermined degree of divergence.
or a lens element that adjusts the degree of convergence, the lens element forms the first interference fringe and the second interference fringe in a ring shape centered on the center line, and the light receiving element Claim (1) characterized in that the device is arranged so as to receive the diameter portion of the first or second interference fringe.
The laser oscillation device described. (3) A wavelength selection element is arranged on the optical path inside the laser resonator, and a part of the pulsed laser light output from the resonator at the first repetition period is inputted to respond to the wavelength change of the pulsed laser light. The wavelength monitor system outputs the detected signal.
In an exposure apparatus that includes a laser oscillation device that changes the selected wavelength of the wavelength selection element and sequentially exposes a plurality of substrates using the output pulsed laser light, a reference light having a stable wavelength is made incident on the wavelength monitor system. a reference light source for
When the exposure of the pulsed laser light to the substrate is interrupted, a first control means that switches the oscillation of the pulsed laser light to a second repetition period that is longer than the first repetition period; When at least one pulse of the pulsed laser light emitted at the second repetition period enters the wavelength monitoring system while exposure of the substrate is interrupted, the wavelength of the reference light and the wavelength of the pulsed laser light and second control means for detecting a relative change in wavelength with respect to the wavelength selection element and correcting the selected wavelength of the wavelength selection element based on the detection result. Exposure equipment. (4) The exposure apparatus has a mechanism for sequentially stepping a plurality of regions on the substrate to the irradiation position of the pulsed laser light, and the first control means is configured to control a predetermined position at which the exposure of the pulsed laser light is interrupted. 4. The exposure apparatus according to claim 3, wherein the time is set longer than the time required for stepping.