JPH0541344A - Projection exposure device - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to measure the image forming characteristics such as field curvature, image surface inclination, and average focal plane without using a test reticle, and to correct the image forming characteristics. To do. [Configuration] Five openings (21a to 2a) on the Z stage 14
1e) is provided, and the openings 21a to 21 are provided.
Each of e is illuminated from below, and the illumination light is made incident on the reticle R. Then, of the light that reaches the reticle R, the photoelectric detector 2 that receives the light that is reflected by the reticle R and that passes through each of the openings 21 again and outputs a photoelectric signal according to the amount of received light.
Based on the output of 8 and the output of the focus detection system 29, the focus position detection unit 32A detects the image plane state, and the image formation characteristic detection unit 32B uses this detection information to form the image formation characteristic (field curvature,
Image plane inclination). Based on the measurement result, the lens element (40, 41, 43, 45) is driven to correct the image forming characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus, and more particularly to a projection exposure apparatus for manufacturing a semiconductor integrated circuit or for manufacturing a large-sized liquid crystal substrate, which has a mechanism for measuring the image forming characteristics of a projection optical system. It is about.

[0002]

2. Description of the Related Art Techniques for measuring the image forming characteristics of a projection optical system and correcting the projection optical system so that the image forming state of a mask pattern is the best are disclosed in JP-A-60-26343 and JP-A-60-26343. 63-306626 or JP-A-1-27.
3318 gazette etc. are disclosed.

The one disclosed in Japanese Patent Application Laid-Open No. 60-26343 is a test reticle having minute line elements,
A light receiving element that is installed on the stage and that receives the transmitted light of the test reticle through a minute slit, and that receives light when the stage is moved up and down on the Z axis (axis of the optical axis of the projection optical system). Based on the change in the output signal from the element, the characteristics of the projection optical system, for example, the image plane inclination and the image plane curvature are obtained. Then, the image forming characteristic of the projection optical system is corrected based on this measurement result.

The one disclosed in JP-A-63-306626 or JP-A-1-273318 is a reference reticle having a reference mark provided on a stage and a test reticle having a special reference mark. Is provided, the reference member is irradiated from the lower surface thereof, and the light flux transmitted through each reference mark of the reference member and the test reticle is received so that the imaging characteristics of the projection optical system can be measured. Then, a change in the image forming characteristic of the projection optical system due to a temperature rise due to the absorption of the exposure light is predicted in advance, and based on the result, the change in the image forming characteristic at the time of exposure is predicted and corrected. According to these devices, it is possible to correct, in real time, the imaging characteristics of the projection optical system due to thermal energy during exposure, for example, changes such as image plane inclination and image plane curvature.

[0005]

However, in the focus position detection by the through-the-lens (TTL) method of this kind, a reticle having a specific mark (a specific mark is formed around a test reticle or an exposure area). I needed an actual reticle). Therefore, when the imaging characteristic is measured using the test reticle every time the measurement is performed and the imaging characteristic is corrected, the decrease in throughput cannot be avoided. Furthermore, when a test reticle is used, it is not possible to measure the in-focus position for each pattern portion of the actual reticle immediately before exposure, and it is not possible to accurately detect the imaging characteristics of the projection optical system immediately before actual exposure. There wasn't. When detecting the imaging characteristics of the projection optical system using an actual device reticle (actual reticle) without using a test reticle, the image plane state is measured using the marks formed around the exposure area. However, it is unrealistic to arrange the marks in each portion in the transfer area, which adversely affects the degree of integration of the circuit pattern.
For this reason, the focus cannot be detected in the central portion of the exposure area, and it is impossible to measure the curvature of field or the tilt of the image plane of the projection optical system. There was a problem.

Further, it is necessary to previously focus the optical system of the focus position detection system of the TTL system and the reticle, and further, the stage is made to scan in the direction perpendicular to the optical axis, or the stage is temporarily moved in the optical axis direction. After moving, it is necessary to repeat the scanning in the direction perpendicular to the optical axis. For this reason,
It takes time to detect the focus, resulting in a decrease in throughput.

The present invention has been made in view of the above problems, and image formation such as field curvature, image plane inclination, and average focal plane immediately before actual exposure of a projection optical system without using a test reticle or the like. The purpose is to measure the characteristics with good throughput and to correct the imaging characteristics of the projection optical system.

[0008]

In order to solve the above problems, in the present invention, a first illumination system (1) for uniformly illuminating a mask (R) having a predetermined mask pattern with exposure light (IL). 2, 6, 7, 9, 10, 12, 13), a projection optical system (PL) for forming an image of a mask pattern on a predetermined image forming plane, and a photosensitizer so as to substantially coincide with the predetermined image forming plane. Holding the substrate (W), the optical axis (AX) of the projection optical system (PL)
In a projection exposure apparatus having a stage and a stage (14, 15) movable in a direction perpendicular to an optical axis (AX), a plurality of minute apertures (21a to 21a) are arranged on a surface in a predetermined arrangement relationship.
The reference member (20) on which e) is formed and a plurality of minute openings are illuminated from the stage side with exposure light or light having a wavelength substantially equal to the exposure light, and the transmitted light transmitted through the plurality of minute openings is projected. The second illumination system (22, 23, 24, 25, 26, 27) that is incident on the mask through the optical system and the light that reaches the mask by the illumination of the second illumination system is reflected by the mask. Photoelectric detection means (28) having a light receiving surface for individually receiving the reflected light that has passed through each of the plurality of minute apertures again via the projection optical system, and individually outputting a photoelectric signal corresponding to each amount of received light. And the optical axis direction at each position of the plurality of minute apertures on the predetermined image forming surface based on each photoelectric signal output from the photoelectric detection means when the stage is moved in the optical axis direction of the projection optical system. Image plane state detecting means (32A) for detecting the position of the Based on the position information detected by the state detecting means, the focal position of the projection optical system, the imaging characteristic detecting means for calculating at least one characteristic of the image plane tilt and curvature of field and (32B) is provided.

[0009]

According to the present invention, a specific pattern (opening) provided on or near the reticle back surface (pattern surface) and the projection optical system is exposed to the exposure light or the exposure light from the side opposite to the projection optical system. Illumination with light having substantially the same wavelength, and light that has passed through the specific pattern reaches the reticle via the projection optical system. Then, the light reflected on the back surface of the reticle again passes through the specific pattern through the projection optical system and enters the photoelectric detector. The position where the reticle back surface and the specific pattern are optically conjugate with respect to the projection optical system, that is, the image formation position of the specific pattern on the reticle back surface (focus position of the projection optical system)
Is used, the maximum amount of light incident on the photoelectric detector is used.

In accordance with this principle, in the area on the reference member corresponding to the exposure field (image field) IF of the projection optical system, for example, specific patterns (openings) are provided at the four corners of the center and the peripheral part, and the center of the reference member is provided. The reference member is moved to below the projection optical system so that the optical axis of the projection optical system and the optical axis of the projection optical system substantially coincide with each other. After that, the reference member is scanned for a certain distance in the optical axis direction of the projection optical system while measuring the distance between the projection optical system and the reference member by, for example, an oblique incidence type AF detection system. At this time, the signal from the photoelectric converter that individually outputs the signal corresponding to the light amount obtained from each specific pattern and the signal from the AF detection system are simultaneously sampled at regular intervals (for example, 0.02 μm). , A / D converted signal is stored in the memory. Then, the value of the signal from the AF detection system when the signal from the photoelectric converter reaches the peak value is obtained. By performing this process for each specific pattern, the imaging characteristics such as the field curvature and the image tilt of the projection optical system are obtained, and the AF detection system at the time of the peak of the photoelectric signal obtained from each specific pattern is obtained. The average focus position of the image plane can be obtained by averaging the obtained signal values. The imaging characteristic is corrected based on this result.

As described above, according to the present invention, a specific mark is not required on the reticle, and when the actual mask pattern is set, the reference member is simply scanned only once in the optical axis direction of the projection optical system. Since the image plane position, the image plane curvature, and the image plane inclination are obtained, the image forming characteristics of the projection optical system can be measured at high speed. Furthermore, since the image forming characteristic correcting means corrects the image forming characteristic so as to cancel the variation, it is possible to always maintain a good image forming characteristic.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing a schematic configuration of a projection exposure apparatus according to an embodiment of the present invention. In FIG. 1, an illumination light source 1 for exposure such as an ultra-high pressure mercury lamp or an excimer laser light source is a g-line, i-line, or ultraviolet pulsed light (for example, Kr light).
Illumination light IL having a wavelength (exposure wavelength) that exposes a resist layer such as an F excimer laser) is generated. Illumination light I
L is an illumination including a shutter 2 that closes and opens the optical path of the illumination light, and a semi-transmissive mirror 4 that allows most (90% or more) of the illumination light to pass, and then includes an optical integrator (fly-eye lens) and the like. Reach the optical system 6. At this time, the mirror 22 is retracted from the optical path in the normal state (at the time of exposure), and is moved on the optical axis by the motor and the air pressure only when measuring the image forming characteristics of the projection optical system PL as described later.

The shutter 2 is driven by a drive unit 3 so that the transmission and blocking of illumination light can be controlled. Also,
A part of the illumination light reflected by the semi-transmissive mirror 4 enters a photoelectric detector (power monitor) 5 such as a PIN photodiode. The power monitor 5 photoelectrically detects the illumination light IL and outputs light information (intensity value) PS to the main control system 32.
S is basic data for obtaining a variation amount of the image forming characteristic of the projection optical system PL during exposure (details will be described later).

Illumination light IL, whose light flux has been made uniform and speckles have been reduced in the illumination optical system 6, is reflected by the mirror 7, passes through the relay lenses 9a and 9b and the variable blind 10, and then the mirror. The light is reflected vertically downward at 12 to reach the main condenser lens 13, and illuminates the pattern area PA of the reticle R with uniform illuminance. Since the surface of the variable blind 10 is in an image-forming relationship with the reticle R, the drive motor 11 opens and closes the movable blade that constitutes the variable blind 10 to change the aperture position and shape, thereby arbitrarily selecting the illumination field of the reticle R. can do. Further, in the present embodiment, the reflected light generated from the wafer W by the irradiation of the illumination light IL passes through the mirror 7 and is incident on the photoelectric detector (reflection amount monitor) 8. The reflection amount monitor 8 photoelectrically detects the reflected light and outputs optical information (intensity value) RS to the main control system 32. Here, the optical information RS serves as basic data for obtaining the variation amount of the image forming characteristic of the projection optical system PL during exposure. (Details will be described later) The reticle R is 2 in a plane perpendicular to the optical axis AX of the projection optical system PL.
It is placed on the reticle stage RST that can move dimensionally,
The center point of the pattern area PA is the optical axis AX of the projection optical system PL.
The positioning is performed so as to coincide with. Initialization of the reticle R is performed by finely moving the reticle stage RST based on a mark detection signal from a reticle alignment system RA that photoelectrically detects an alignment mark (not shown) around the reticle. The reticle R is used after being appropriately replaced by a reticle exchanger (not shown). In particular, when performing high-mix low-volume production, replacement is frequently performed.

The illumination light IL that has passed through the pattern area PA is incident on the projection optical system PL which is telecentric on both sides, and the projection optical system PL forms a projection image of the circuit pattern of the reticle R on which a resist layer is formed. Projection (image formation) is performed by superimposing it on one shot area on the existing wafer W.
The wafer W is placed on a leveling stage (not shown),
The leveling stage is provided on a Z stage 14 that can be finely moved in the optical axis direction (Z direction) by a drive motor 17. Further, the Z stage 14 is mounted on the XY stage 15 which can be two-dimensionally moved by the step-and-repeat method by the drive motor 18, and the XY stage 15 transfers and exposes the reticle R onto one shot area on the wafer W. When finished, the next shot area on the wafer is moved until it coincides with the exposure area of the projection optical system PL.
The two-dimensional position of the XY stage 15 is constantly detected by the interferometer 19 with a resolution of about 0.01 μm,
A movable mirror 14m that reflects the laser beam from the interferometer 19 is fixed to the end of the Z stage 14. Interferometer 1
9 and the movable mirror 14m are provided in pairs for position detection in the X and Y directions.

A dose monitor 16 is provided on the Z stage 14, and the dose monitor 16 is provided with a light-receiving surface having substantially the same area as the image field of the projection optical system PL or the projection area of the reticle pattern, for example. The photoelectric detector is provided on the Z stage 14 so that its light receiving surface is substantially aligned with the surface position of the wafer W. The information LS on the irradiation amount of the shot area obtained from the irradiation amount monitor 16 is sent to the main control system 32 and serves as basic data for obtaining the variation amount of the imaging characteristic of the projection optical system PL during the exposure. (Details will be described later) Z
On the stage 14, there is provided a reference member 20 used when measuring the image forming characteristics of the projection optical system PL, for example, the focus position, the field curvature, and the image surface inclination. FIG. 3 shows this reference member 20, and in FIG. 3, the circle of radius L is the maximum exposure area (image field) IF of the projection optical system PL.
The square inscribed in this circle represents the maximum square chip area CH when actually exposing the wafer. As shown in FIG. 3, openings 21a to 21e are provided on the surface of the reference member 20 at positions corresponding to one central portion and four peripheral portions of the image field IF. The openings 21a to 21e are provided with, for example, a checkerboard pattern shown in FIG. 2A or a lattice pattern shown in FIG. 2B, and the surface of the reference member 20 and the surface of the wafer W are substantially coincident with each other. Is desirable. As the shape of the pattern (opening pattern) provided in the opening 21, it is necessary to select a shape whose projected image does not exactly overlap the circuit pattern on the reticle R. This is because when the projected image of the aperture pattern is exactly overlapped with the circuit pattern, the position at which the maximum or minimum of the change in the amount of light reflected from the reticle R that passes through the aperture 21 (described in detail later) is not necessarily the focal point. This is because there is no limit.

Here, by making the opening pattern a checkered pattern as shown in FIG. 2A, the influence of this circuit pattern can be reduced, and the influence of astigmatism of the projection optical system can be reduced. Can be avoided. Also,
Even in the lattice pattern as shown in FIG. 2B, the influence of the circuit pattern can be prevented by inclining its side with respect to the side of the circuit pattern by about 10 to 30 degrees. this is,
This is because there are many vertical and horizontal patterns (0 degrees, 90 degrees) orthogonal to each other in the circuit pattern used for semiconductor manufacturing. Further, the shape of the aperture pattern is preferably a plurality of parallel lines that are not parallel to any line of the circuit pattern, and the parallel lines are preferably orthogonal to each other in the sense of avoiding the influence of astigmatism of the projection optical system. .. Further, the area ratio of the light-shielding portion and the transmission portion of the opening pattern is set to 1: 1 so that the SN ratio becomes the best.
Is desirable. In the present specification, the opening 21
The a to 21e are collectively referred to as the opening 21.

Normally, when the plane such as the inclination of the image plane is to be obtained, the number of the openings 21 may be three, and even when the curvature of the image is to be obtained, the three openings 21 are required.
It may be four points, which is one point in the center plus one point. However,
In the present embodiment, the opening 21 is set to 5 points in consideration of the case where the projection optical system is asymmetrical, or there is eccentricity. Further, by providing a plurality of points with the openings 21 and measuring at a larger number of points, more information such as waviness of the image plane can be obtained. However, if the number of apertures 21 is large, the optical system is complicated and the throughput is reduced. Therefore, here, in consideration of the fact that the optical aberration such as field curvature becomes the maximum between the optical axis AX of the projection optical system PL and the outermost portion of the image field IF, the four points in the peripheral portion are the maximum chips. In the area on the reference member 20 corresponding to the area CH, the four points (21c to 21e) farthest from the center of the reference member 20 are selected, and the minimum required five points are combined with the center (21a) of the image field. Is selected. In other words, the maximum value of the field curvature can be measured, and the throughput can be increased while maintaining the detection reliability of the image plane tilt and the focal plane. In addition, the device can be simplified by using the minimum number of openings 21.

Now, in FIG. 1, the opening 21 is illuminated from below (on the stage side) by the measurement illumination system LL. The measurement illumination system LL includes a mirror 22 and a half mirror 2 which are inserted into the optical path of the illumination light IL by a driving device (not shown).
3, lens 24, optical fiber 25, lens 26, and mirror 27, and guides the illumination light IL into the wafer stage 15. The illumination light emitted from the opening 21 reaches the reticle R via the projection optical system PL, is reflected by the back surface (pattern surface) of the reticle R, and returns to the opening 21 again via the projection optical system PL. After passing through the opening 21, the reflected light is incident on a photoelectric detector 28 including a photomultiplier, an SPD, etc. via a mirror 27, a lens 24, a fiber 25, a lens 26, and a half mirror 23, and the photoelectric detector 28. Is converted into an electric signal by photoelectric conversion. Here, although not shown, the measurement illumination system LL is configured to individually illuminate the five sets of openings 21a to 21e, and the photoelectric detector 28 individually receives the reflected light. It should be noted that the entire back surface of the opening 21 is illuminated and the five pairs of openings 21a to
It may be configured to individually receive the reflected light from each of 21e.

Further, for example, the entire back surface of the reference member 20 can be illuminated, and the reference member 20 and the fiber 25 can be illuminated.
The variable diaphragm may be arranged between the end surface of the variable aperture and the end surface of the variable aperture, and the variable diaphragm may be driven to detect the focal position at each aperture pattern position so that the illumination light is emitted only to the desired aperture. .. Further, even if the variable diaphragm is not provided, the reference member 20
It is also possible to illuminate the entire back surface of the device and electrically mask the signal from the photoelectric detector 28 so that only the signal corresponding to the reflected light from the desired aperture is processed. With this arrangement, the illumination system and the photoelectric detector need only be one set, and the device can be simplified.

The illumination light IL is emitted from the light source 1 to the mirror 22.
It is supposed that the light is guided to the reference member 20 via the light source 1.
The reference member 20 may be illuminated by separately providing a light source that emits light having a wavelength substantially equal to that of the illumination light IL. On the other hand, in FIG. 1, reference numeral 34 is an oblique-incidence type detection optical system.
It is disclosed in the publication. This oblique incidence type detection optical system 34
Is a focus detection system 29 that detects the vertical position (Z direction) of the wafer surface with respect to, for example, the best designed image plane of the projection optical system PL, and detects the in-focus state between the wafer W and the projection optical system PL. And a horizontal position detection system 30 for detecting the inclination of the wafer surface with respect to the designed image plane of a predetermined area on the wafer W.
It is a combination of and.

Focus detection system 29 and horizontal position detection system 30
Are light sources 29a and 30a for emitting illumination light incident on the wafer surface from an oblique direction with respect to the optical axis AX, a half mirror 31a, light receiving optical systems 29b and 30b for receiving reflected light on the wafer surface, and half And a mirror 31b.
The illumination light emitted from the light source 29a is an imaging light flux that forms an image of a pinhole or a slit, and the light source 30a.
The illumination light emitted from is a parallel light flux. In this embodiment, the angle of the parallel flat glass (plane parallel) (not shown) provided inside the light receiving optical system 29b is adjusted in advance so that the best designed image plane becomes the zero point reference, and the focus is adjusted. While the detection system 29 is calibrated,
When the surface of the wafer W coincides with the image plane, the light source 30a
The horizontal position detection system is calibrated so that the parallel light flux from the light source is focused at the center position of the four-division light receiving element (not shown) inside the light receiving optical system 30b.

Next, the structure of the correction means for correcting the image formation state will be described. In this embodiment, the image forming characteristics (projection magnification, distortion, curvature of field, etc.) are corrected by driving the lens elements of the projection optical system PL. A part of the optical element is movable in order to be adjustable. As shown in FIG. 1, the lens elements 40 and 41 of the first group closest to the reticle R are the support members 4
The lens element 43 of the second group is fixed by the supporting member 44, and the lens element 45 of the third group is fixed by the supporting member 46. The lens elements below the lens element 45 are fixed to the lens barrel portion 47 of the projection optical system PL.

FIG. 4 is a view of the projection optical system PL viewed from above (reticle side). The driving elements 48a to 48c are arranged at positions rotated by 120 °, respectively, and can be independently controlled by the driving element control unit 23. Has become. Similarly, the drive elements 49a to 49c and 50a to 50c are also rotated by 120 °, respectively, and can be independently controlled by the drive element control unit 33. The drive elements 48a, 49a and 50a are arranged offset from each other by 40 °, and the drive elements 48b, 49b and 50b and
8c, 49c and 50c are also 40
They are arranged at different degrees. As the drive elements 48 to 50, for example, an electrostrictive element or a magnetostrictive element is used, and the displacement amount of the drive element according to the voltage or magnetic field applied to the drive element is obtained in advance. Although not shown here, a capacitive displacement sensor, a differential transformer or the like is provided as a position detection device near the drive element in consideration of the hysteresis of the drive element. As a result, the position of the drive element corresponding to the voltage or magnetic field applied to the drive element can be monitored, so that highly accurate drive is possible.

In the present embodiment, the optical axis AX of the projection optical system PL refers to the optical axis of the lens element fixed to the lens barrel portion 47. Now, the support member 46
Is connected to the lens barrel portion 47 of the projection optical system PL by extendable drive elements 50a, 50b, 50c. Also,
The support member 44 includes drive elements 49a, 49b, 4 which can be expanded and contracted.
The support member 42 is connected to the support member 46 by means of 9c, and the support member 42 is capable of expanding and contracting the drive elements 48a, 48b, 48c.
It is connected to the support member 44 by. Here, in this embodiment, the lens elements (40, 41), 43, and 45 close to the reticle R can be independently moved by controlling the above-mentioned drive elements by the drive element control unit 33. The element (1) is selected so that the influence on the image forming characteristics such as magnification, distortion, image plane curvature, image plane inclination, and focal position is greatly controlled compared to other lens elements. Further, in this embodiment, since the movable lens element is composed of three groups, it is possible to increase the movement range by moving the lens element while suppressing the fluctuation of other various aberrations. Moreover, it is possible to cope with various shape distortions (trapezoidal, rhombic, barrel-shaped, pincushion-shaped, etc.), and it is possible to sufficiently cope with fluctuations in the imaging characteristics of the projection optical system PL due to absorption of exposure light. still,
It is assumed that the lens element is moved within a range in which influences on other aberrations (eg, astigmatism, spherical aberration, etc.) of the projection optical system PL can be ignored. Alternatively, as described above, by adjusting the distance between the lens elements, it is possible to employ a method of controlling the field curvature and also correcting other various aberrations (distortion, etc.).

With the above configuration, the three peripheral points of the lens elements (40, 41), 43 and 45 of the three groups are independently driven by the drive command given from the main control system 32 in the optical axis AX direction of the projection optical system PL. It can be moved by an appropriate amount. As a result, the three groups of lens elements (40, 4
Each of 1), 43, and 45 can be translated substantially along the optical axis AX, and can be arbitrarily tilted with respect to a plane substantially perpendicular to the optical axis AX.
The lens elements are supposed to be tilted with the optical axis AX as a virtual tilt reference. The lens elements (40, 41), 43 and 45 are movable in a plane substantially perpendicular to the optical axis AX.

The main control system 32 not only controls the drive element controller 33, but also the focus position detector 32A as will be described later.
(Image plane state detecting means according to the present invention), image forming characteristic detecting section 3
The imaging characteristics of the projection optical system PL having 2B, such as the field curvature, the image surface inclination, and the average focus position, are obtained. Further, as will be described later, the optical information is respectively obtained from the power monitor 5, the reflection monitor 8, and the irradiation amount monitor 16, and the fluctuation amount of the image forming characteristic of the projection optical system PL during the exposure is calculated and the stage is started. Controls the entire device including the above.

Next, a method of measuring the image forming characteristics of the projection optical system PL such as the field curvature and the image surface inclination in this embodiment will be described. While monitoring the stage position with the interferometer 19 while the reticle R is placed on the reticle stage RST, the XY is set so that the center of the opening 21 (a) on the reference member 20 is on the optical axis AX of the projection optical system. The stage 15 is moved by the motor 18. At this time, the motor 17 is driven at the same time to move the Z stage 14 to the expected focus variation amount (variation amount of the image forming characteristic) from the position considered to be the best focus position (best image forming surface) in the design of the projection optical system PL. Lower or raise it by several times. This is, for example, the depth of focus (± DOF)
It may be lowered about twice (2 · DOF) or raised.

At the same time, the mirror 22 is moved into the optical path to guide the illumination light IL to the opening 21, and the back surface (pattern surface) of the reticle R is illuminated via the opening 21 and the projection optical system PL. The illumination light reflected from the reticle R again passes through the projection optical system PL and the opening 21, and then the mirror 27 and the lens 2
6, optical fiber 25, lens 24, 27 via half mirror 23, photoelectric detector 28 via half mirror 24
Incident on. Thereafter, in this state, the Z stage 14 is moved upwards (or downwards) to the above-mentioned expected focus variation amount 2
Scan about twice. At this time, the main control system 32 simultaneously outputs the output of the photoelectric detector 28 and the output of the focus detection system 29, for example, Z
The unit movement amount of the stage 14 (for example, 0.02 μm) is sampled and A / D converted to obtain the relationship shown in FIG. Here, the vertical axis of FIG. 5 represents the photoelectric detector 28 according to the amount of reflected light that has passed through one of the openings 21a to 21e.
From the focus detection system 29, and the horizontal axis represents the magnitude of the output from the focus detection system 29 corresponding to the position of the Z stage 14.

The reason why the relationship shown in FIG. 5 is obtained can be explained as follows. When the opening 21 is in the defocus area of the projection optical system PL with respect to the back surface of the reticle R, the illumination light emitted from the opening 21 passes through the projection optical system PL and forms an opening pattern (for example, a checkerboard pattern) on the back surface of the reticle R. Make a defocused image. After that, when the illumination light reflected on the back surface of the reticle R is incident on the opening 21 again via the projection optical system PL, it becomes an image of a further defocused opening pattern. Therefore, when this reflected light passes through the aperture pattern, the defocused portion does not pass through the light-shielding portion of the aperture pattern, and the amount of its spectrum is reduced.

On the other hand, when the opening 21 is at a position optically conjugate with the back surface of the reticle R with respect to the projection optical system PL, that is, at the focal plane (imaging plane) of the projection optical system PL, the opening 2
Since the illumination light emitted from No. 1 forms a sharp image on the back surface of the reticle R, when the reflected light passes through the aperture pattern, almost all of the reflected light reaches the light shield portion of the aperture pattern (is eclipsed by the light shield portion). Instead, the amount of light received by the photoelectric detector 28 increases as compared with the case of defocusing. Therefore, in FIG. 5, the position (position in the Z direction) corresponding to the output value f obtained by the focus detection system 29 at the peak output of the photoelectric detector 28 is the best focus position (best focus position) of the projection optical system PL. Become. Here, it is also possible to obtain the best focus position by using a transparent reticle R having no circuit pattern or a reticle R provided with a light-shielding portion on the entire surface of the circuit pattern area. It may be possible to periodically check whether or not the focus position is measured without being affected by the circuit pattern. By the way, in the case of a transparent reticle having no circuit pattern, the glass surface on the back surface of the reticle serves as a reflecting surface, and its reflectance is about 4%, but it can be sufficiently detected by increasing the detection sensitivity.

The best focus position is detected by the focus position detector 32A in the main control system 32. The focus position detector 32A obtains the peak value from the output of the photoelectric detector 28 as described above, and at that time. From the output value of the focus detection system 29, the focus position (Z
Direction position). This processing is performed for each opening 21a.
~ 21e, the openings 21a ~ 2 as shown in FIG.
The best focus position for each 1e is obtained from the output value of the focus detection system 29. Here, f _{1 to} f ₃ indicate the output of the focus detector 29 when the output value of the photoelectric detector 28 is the peak value. In this embodiment, the reference member 20 has five openings 21.
Since a to 21e are provided and the reflected light transmitted through each of the openings 21a to 21e can be individually received, the Z of the Z stage 14 in the measurement operation as described above is performed.
Since the scanning in the direction is required only once, the measurement with high throughput becomes possible.

Based on the result of FIG. 6, the relationship of the output value of the focus detection system 29 with respect to the image height (the distance from the optical axis AX to the periphery of the exposure area) is obtained, and the graph of FIG. 7 is obtained. The graph of FIG. 8 is obtained by separating the data on the surface inclination and the data on the field curvature. 7 and 8
The vertical axis represents the output of the focus detection system 29, the horizontal axis represents the image height, Z ₁ is the maximum focus position when the image plane tilt component is removed from the data values shown in FIG. 7, and Z ₂ is the figure. The lowest focus position when the field curvature component is removed from the data value shown in 7, Z ₃
Is the highest focus position when the field curvature component is removed from the data values shown in FIG.

Then, in FIG. 7, the image plane inclination ΔZ is obtained from the data of the openings 21a to 21e excluding the central opening 21a.
Ask for. First, Z ₂ and Z _{3 which} are basic data for obtaining the image plane inclination are obtained by the following equation. Z ₃ = f ₁ + (f ₃ −f ₂ ) / 2 Z ₂ = f ₁ − (f ₃ −f ₂ ) / 2 Then, using Z ₂ and Z ₃ , the image plane inclination ΔZ is ΔZ = Z obtained in decreasing _{3 -Z 2 = f 3 -f 2} , represented by a straight line on the Figure 8.

Here, the image plane inclination ΔZ is corrected by calculation, and the central aperture outputs are added to the four corner aperture outputs to obtain the image plane curvature Δr. Here, there is a relationship of Z ₁ = (f ₂ + f ₃ ) / 2, and from this, the field curvature Δr becomes Δr = Z ₁ −f ₁ , which is represented by the lower curve in FIG. 8. Further, the average focus position f _A is obtained as f _A = f ₁ + Δr / 2.

Incidentally, these image plane inclination ΔZ and image plane curvature Δ
The calculation for obtaining r and the average focus position f _A is performed by the imaging characteristic detection unit 32B in the main controllability 32. Next, a method of correcting the field curvature, the field inclination, and the average focus position will be described.
Basically, as described above, by driving the three lens elements (40, 41), 43 and 45 of the projection optical system so as to be tilted with the optical axis direction or an axis perpendicular to the optical axis as the rotation axis. , Obtain a desired image formation state. (Here, for the sake of simplicity, only the field curvature, the image tilt, and the average focus position will be described, but the projection magnification, the distortion, etc. can be corrected.) For example, the lens element (40, 41). The change in the curvature of field due to the driving of) will be described with reference to FIG. Here, the change of the field curvature shown in FIG. 9 is 1
It is one example, not a general one, and the way of changing actually varies depending on the configuration of the lens element. In this embodiment, the curvature of field changes as shown in FIG. 9 by moving the lens element 40 or 41 in the optical axis direction. Further, depending on the method of configuring the lens, the field curvature is changed by moving the lens elements (40, 41) and 42 in the direction perpendicular to the optical axis. The relationship between the drive amounts of the lens elements (40, 41), 43 and 45 and the change amount of the field curvature is stored in the memory in the main control system 32 in advance.

Driving the lens elements to correct the field curvature may deteriorate magnification, distortion, and other aberrations (for example, coma and astigmatism), but drives a plurality of lens elements. Therefore, desired field curvature correction can be performed while correcting aberration. Further, aberrations and the like may be corrected by changing the image forming characteristic of the projection optical system by changing the pressure of the air portion between the lens elements as disclosed in JP-A-60-78454. Lens element (40, 4
1), 43, and 45 may cause the image plane to move up and down, but if the output value of the focus detection system 29 is offset according to the amount of change, the wafer W
Is always set to the best image plane, preventing this effect.

The correction of the image plane inclination is performed by the above-mentioned image forming characteristic detecting section 3
Calibration may be performed by adding the focus differences (image plane inclinations) at the four corners of the exposure field obtained from 2B to the horizontal position detection system 30 as offsets. That is, the tilt of the image plane is corrected by driving the leveling stage and tilting the wafer W while detecting the horizontal position of the wafer surface by the horizontal position detection system 30 to which the offset is applied.

As for the focal point position, the average focal point position f _A is obtained as described above, and the motor 17 is driven based on this value to control the Z stage 14 so that the wafer W and the image plane always match. At this time, it is desirable to perform calibration so that the zero point reference of the focus detection system 29 becomes the average focus position f _A. As described above, when the Z stage 14 is controlled, the front surface of the wafer is optically conjugate with the back surface of the reticle R, and a good image is obtained. Further, although the simple average value is used in the above, the focus detection system 29 may be calibrated on a surface that minimizes the maximum deviation between the image plane and the wafer surface. As described above, by performing the exposure on the surface or the average focus position where the maximum deviation is minimized, better exposure is performed as compared with the conventional case even when the field curvature is not sufficiently corrected. .. If the linearity guarantee range of the focus detection system 29 (in other words, the detectable range) is small, the motor 17 is provided with a position sensor such as an encoder. The Z stage 14 is scanned by the value of this position sensor to obtain the relationship between the output signal of the photoelectric detector 28 and the focus position (Z stage position) as shown in FIG. After that, while driving the herbing glass in the focus detection system 29 by a drive system (not shown), the focus position (encoder value) is associated with the output of the focus detection system 29, and finally the focus detection system 29 is detected. The output of the photoelectric detector 28 is obtained.

Here, in the case of correcting the field curvature or the field inclination, when exposing only half the exposure area, for example, FIG.
In the case where the field curvature is 81 as shown in FIG. 7, the variable blind 10 exposes the area left from the center line 80, and the surface of 82 is aligned so that the wafer W is better aligned with the image plane. A method of bringing the wafer W is also conceivable.

Also, regarding the image plane tilt and the average focus position, the main control system 32 preliminarily shows the relationship between the drive amounts of the lens elements (40, 41), 43 and 45 and the image plane tilt and the change amount of the focus position.
It can be corrected by storing it in the internal memory and driving the lens elements (40, 41), 43 and 45 as described above. At this time, an average image forming surface is obtained based on the image surface curvature, the image surface inclination, and the average focus position measured by using the opening 21, and the lens elements (40, 41) and 42 are aligned with the image forming surface. It may be driven. As a result, the exposure can be started in a state where the image forming characteristic is corrected in advance.

Incidentally, the measurement of the image forming characteristic of the projection optical system as in the above-mentioned embodiment may be carried out every unit time or every predetermined number of processed wafers. Next, the operation of this embodiment will be described. (1) First, the image plane curvature, image plane inclination, and average focus position that the projection optical system PL has in the initial state are reflected light obtained from the aperture 21 by scanning the Z stage 14 as described above when the system is set up. Is measured by a method for obtaining an image forming characteristic based on a signal corresponding to
0, 41), 43, 45, or by driving the lens elements (40, 41), 43, 45, the leveling stage, and the Z stage so that the optimum image formation state and the focus position can be obtained. You can correct it.

(2) Further, the focus position and the image plane are changed by the change of environment such as atmospheric pressure and temperature, the absorption of the illumination light of the projection optical system PL, or the deflection of the reticle R by its own weight and the deformation of the reticle R by the absorption of the illumination light. Even if the curvature and the inclination of the image plane change from those at the time of system up, those changes are relatively slow, or the focus position at regular measurement intervals (for example, every 10 wafer exchanges, every wafer exchange, every several shots, etc.) If the amount of change in the curvature of field or the inclination of the field is negligible, the Z stage 14 is periodically scanned, for example, when the wafer is replaced, and the result is obtained based on the signal corresponding to the reflected light obtained from the opening 21. The image characteristics may be measured and correction may be performed in the same manner as (1).

(3) The imaging characteristics of the projection optical system PL (focal position, field curvature,
When the change of the image plane inclination) is fast, the predictive control and the above-mentioned aperture 2
By using the measurement using 1 together, it becomes possible to deal with the change of the imaging characteristic. The predictive control is, for example, JP-A-1-27.
Similarly to the one disclosed in Japanese Patent No. 3318, the imaging characteristics that vary depending on the amount of heat that the projection optical system PL receives from the exposure light are stored in advance in the memory, and based on the values stored in this memory, the actual exposure is performed. The imaging characteristic is corrected in the same manner as (1). Here, for example, the correction by the predictive control is performed by driving the lens element.

The change characteristic of the image formation state of the projection optical system PL is
Open / close information of the shutter 2, output PS of the power monitor 5, the reflectance monitor 8 and the dose monitor 16,
The amount of heat is measured by using RS and LS, and the state variable of the imaging characteristic that changes depending on the amount of heat is stored in the memory of the main control system 32. The amount of heat is calculated based on the output value LS of the irradiation amount monitor 16 that detects the irradiation energy for each exposure condition and the open time of the shutter 2. Here, when the reflectance of the base of the projection optical system PL is zero, the projection optical system P
Although it is only necessary to consider the transmitted light of L, the amount of heat accumulated in the projection optical system PL varies depending on the reflectance of the base of the projection optical system PL. Therefore, when the reflectance is not zero, the transmitted light + the reflected light is thermal energy. Contribute to. Therefore, in this case, the output value from the reflectance monitor 8 is also used. Further, the power monitor 5 constantly monitors changes with time such as fluctuations of the light source during exposure, and the projection optical system P is also considered in consideration of changes in its output value LS.
Determine the amount of heat stored in L.

When the image forming state of the projection optical system PL fluctuates due to other factors such as atmospheric pressure change, data previously measured and stored (for example, the image forming characteristic with respect to atmospheric pressure change). These changes are also added to the state variables based on the fluctuation data). Calculate the optimum correction amount for the average focus position, field curvature, and field tilt for this total value,
The lens elements (40, 41), 43, and 45 are driven by the lens element driving elements 48 to 50 to perform correction.

In this way, for example, during exposure of one wafer, the lens element (40,
41), 43 and 45 are driven by predictive control. On the other hand, the opening 21 is regularly scanned while scanning the Z stage 14 in the same manner as described above, for example, every time the wafer is exchanged or every unit number of processed wafers (for example, every reticle exchange, every 10 wafers processed).
The signal from the photoelectric detector 28 corresponding to the reflected light from the reticle that transmits the light is detected, and the focus position, the field curvature, and the image surface inclination are calculated from the results. When the focus position, the field curvature, and the image plane inclination of the predictive control are corrected by the focus position, the field curvature, and the image plane inclination obtained from the photoelectric detector 28, the predictive control is periodically calibrated and the projection optical system. The imaging characteristics of PL are improved.

In this calibration, the error between the predictive control and the measurement is calculated, and the predictive control value is corrected to the measured value.
This is performed by correcting the calculation formula of the predictive control. Further, when the predictive control is also used, a number setting means (a counter or the like) for setting, for example, how many wafers the imaging characteristics of the projection optical system as described above should be measured should be provided. Is desirable. Generally, from the start of the exposure operation to the predetermined number of wafers, the difference (calculation error) between the image formation characteristic calculated by calculation in the predictive control and the actual image formation characteristic obtained by the above measurement is small, The number of wafers set in the number setting means may be large, and here, for example, 1
It shall be set to 0 sheets.

As described above, when the number setting means is used,
After measuring and correcting the imaging characteristics before starting the exposure operation,
The wafers up to the tenth wafer are exposed while the imaging characteristics are corrected only by the predictive control, and the measurement and the correction are performed again when the exposure is completed. Then, this measurement result is compared with the imaging characteristic calculated by the calculation of the predictive control, and the difference is equal to or more than a predetermined allowable value (a value determined by the depth of focus of the projection optical system or the control accuracy of the imaging characteristic). In such a case, the set number set in the number setting means may be changed and, for example, measurement and correction may be performed for each wafer. With this method, the number of measurements can be reduced and throughput is improved. Furthermore, by determining the state variable based on the actually measured data and comparing it with the state variable in the predictive control, it is determined how many more wafers will be exposed and the difference will be equal to or greater than the allowable value, The set number may be automatically changed to a smaller number (for example, for each wafer). As a result, the set number can be changed without the difference exceeding the allowable value, and if the image forming state is stable, the exposure can be performed only by the predictive control without the difference exceeding the allowable value. Can be expected to improve.

It should be noted that, for example, an environmental sensor for monitoring environmental changes (pressure, temperature, humidity, etc.) is provided, and during the predictive control, an abnormality such that the image forming characteristic of the projection optical system PL may greatly change can be detected. When the abnormality is detected, the exposure operation is immediately stopped at the time when the abnormality is detected, the measurement using the opening 21 is performed as described above, and the imaging characteristic of the projection optical system PL is corrected by driving the lens element. You can

When the change of the imaging characteristic is fast, the measurement is performed more easily than the above method every time the wafer is exchanged without performing the predictive control, and the linear interpolation or the secondary interpolation is performed based on the value at the time of the previous measurement or the measurement before the second measurement. A certain degree of effect can be obtained by making a prediction in the manner of the next interpolation. Here, even if the reference member 20 is inclined, the inclination is measured in advance by changing the position of the XY stage by the oblique incidence AF, and the opening 21 is opened.
It is also possible to correct the error amount caused by the inclination during measurement by.

In the above-described embodiments, the projection optical system P
The case where only the focus detection system 29 for measuring the center of the optical axis of L is provided has been described, but a plurality of focus detection systems may be provided so that measurement can be performed at various points in the exposure area.
At this time, the plurality of focus detection systems 29 are connected to the opening 21a of FIG.
If each point of ~ 21e can be measured, the reference member 2
Even if 0 is tilted or the tilt is changed, measurement can be performed without error. On the contrary, if the reference member 20 can be held strictly horizontally, the plurality of openings 21 of the reference member 20 can be used for calibration of the plurality of focus detection systems 29.

Further, even when it is not possible to provide a plurality of openings 21 on the reference member 20, when the Z stage 14 is scanned using only the opening 21 (a) at the center of the reference member, the XY stage 15 has the opening 21 (a). Positioning is performed so that a) is located at the positions of the openings 21 (b) to (e) in the present embodiment, the Z stage 14 is scanned each time, and the signal output from the opening 21 (a) may be sampled. However, in this case, there is a disadvantage in throughput from the above-described embodiment. Further, although the number of the openings 21 on the reference member 20 is set to 5 in the above-described embodiment, it is set to 4 if only the image plane inclination is measured.
At points (3 points in an idealized state without asymmetry or eccentricity), the measurement process becomes faster.

Further, in this case, more detailed focusing is possible by taking into consideration the unevenness of the image plane and the unevenness of the wafer W. For example, the image plane can be intentionally curved and exposed in accordance with the warpage of the wafer W. The focus detection system 29 and the horizontal position detection system 30 are not limited to the configuration of this embodiment. For example, by irradiating the four corners of the rectangular shot area on the wafer and the center of the shot area with slit or pinhole images, the height detection position (position in the Z direction) at each point is detected. With this configuration, the inclination amount of the wafer surface can be obtained from the height positions at five points without providing a horizontal position detection system.

Next, a modification of the pattern of the opening 21 will be described. In the embodiments described above, the pattern of the openings 21 is shown in FIG.
Although the description has been made with the combination pattern of the transmission part and the light shielding part as shown in (a) and (b), a pattern equivalent to that of FIG. 2 is formed by using a phase grating pattern that shifts the wavelength of the measurement light by ¼ wavelength. it can. This principle will be briefly described with reference to FIG. As shown in FIG. 11A, the phase grating pattern 21
Illumination from below generates diffracted light. At this time, 0
The ± 1st order light is out of phase with the next light by 1/4 wavelength. These rays are reflected by the back surface of the reticle R and return to the pattern 21 again. When the pattern 21 is on the focal plane of the projection optical system PL, the ± first-order light is diffracted again as shown in FIG. 11B, and the ± first-order light rays return along the same optical path as the zero-order light. At this time, the phases of the light beams ± first-order light are further shifted by ¼ wavelength, and the phases are shifted by ½ wavelength from the zero-order light. Therefore, the light beams ± first-order light act to cancel the zero-order light. When the pattern 21 is not on the focal plane of the projection optical system PL, the phase difference does not become ½ wavelength, and thus the condition for canceling out is not satisfied. From the above, the best focus is when the output of the photoelectric detector 28 corresponding to the reflected light passing through the opening 21 is minimized as shown in FIG. As described above, according to the method using the phase shift pattern, all the light rays pass through the pattern 21 as compared with the above-described method.
The / N ratio becomes high and the best focus point can be easily found.

Further, when the image forming characteristic is corrected on the basis of the measurement result (image surface curvature, image surface inclination, etc.), the herbing glass of the focus detection system 29 is driven by the above-described predictive control so that the approximate focus position is obtained in advance. You may find out. In this case, the scanning range of the Z stage 14 can be reduced and the focus detection system 29
The Z stage can be scanned only by the output of, and the time required for scanning can be shortened and high throughput can be achieved. The focus detection system 2
9 and the method of giving an osset during the calibration of the horizontal position detection system 30 is either an optical method (such as driving a herring glass) or an electrical method (such as electrically adding an offset amount to an output value). But good. Further, an average image forming surface of the projection optical system PL is obtained based on the measurement result (image surface curvature, image surface inclination, average focus position), and the focus detecting system 29 and the focus detecting system 29 are set so that this image forming surface serves as a zero point reference. It suffices to simply calibrate the horizontal position detection system 30. At this time, the average image plane detected as described above is evaluated, and the change amount of this average image plane with respect to the best image plane (design value) is set to a predetermined allowable value (focus detection system 29 or horizontal direction). If it is within the detectable range of the position detection system 30), only the calibration may be performed, and if it exceeds the allowable value, the correction may be performed by the method such as the lens driving described above.

Here, in the above-described embodiment, the projection optical system PL
As an example of means for correcting the image forming characteristic of the projection optical system P
Although a mechanism for driving a part of the lens elements constituting L is used, the correction means applicable to the present invention is not limited to the above mechanism, and for example, a method of driving the reticle R, or a reticle R and projection optics. A field lens arranged between the lens and the system PL is two-dimensionally moved in a plane perpendicular to the optical axis of the projection optical system PL, or is tilted with respect to this plane, or the air pressure between specific lens elements is changed. It is also possible to adopt a method of making it possible.

Further, it is also possible to obtain a graph as shown in FIG. 7 in the same manner as the above-described measuring method and obtain the spherical aberration from the asymmetry, and it is possible to similarly correct by driving the lens element as described above. is there. The spherical aberration can be corrected by inserting a parallel flat plate glass between the projection optical system PL and the wafer and changing the thickness thereof. To change the thickness, for example, slide a pair of wedge-shaped glass,
It suffices to rotate a rotating plate equipped with a plurality of types of glass having different thicknesses.

Further, in the above description, the reference member 20 having the opening 21 is arranged on the Z stage 14, and the illumination light for measuring the image forming characteristic of the projection optical system PL is irradiated from the lower side of the stage to emit light from the back surface of the reticle. Although the reflected light is received again by the photoelectric detector 28 through the projection optical system PL and the opening 21, the illumination light for measuring the imaging characteristics may be emitted as follows.

A test reticle having an aperture pattern is used, and the aperture pattern and projection optical system P are arranged from above the reticle.
The reference reflecting surface on the wafer stage is irradiated with the measurement illumination light via L, and the reflected light from the reference reflecting surface is received by the photoelectric detector through the projection optical system PL and the opening 21 of the reticle. In this case, the photoelectric detector is arranged at a position almost conjugate with the reticle. Here, without using the test reticle,
By providing the openings 21 at a plurality of positions on the actual reticle, the imaging characteristics can be similarly obtained.

Although the reduction type projection exposure apparatus for manufacturing a semiconductor integrated circuit has been described above, the present invention is not limited to the projection exposure apparatus, for example, an exposure apparatus used for manufacturing a large-sized liquid crystal device. Can also be applied to. The device disclosed in the above embodiments can also be applied to a surface position detecting device for detecting the surface position of the second substrate with respect to the first substrate.

[0062]

As described above, according to the present invention, the curvature of field, the inclination of the field, and the average focus position can be obtained at high speed and with high accuracy.
The image forming characteristics of the projection optical system can be periodically corrected without reducing the throughput of the apparatus. Further, even when a mask provided with an actual circuit pattern is set, the imaging characteristics of the projection optical system can be measured without lowering the throughput. Further, the predictive control can be calibrated by combining with the predictive control of the image forming characteristic, and the accuracy of correcting the image forming characteristic is improved.

[Brief description of drawings]

FIG. 1 is a plan view showing the overall configuration of a projection device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an opening pattern.

FIG. 3 is a diagram showing an opening installation location on a reference member corresponding to an exposure area.

FIG. 4 is a top view of the projection optical system PL.

FIG. 5 is a graph showing the relationship between the output of the focus detection system 29 and the output of the photoelectric detector 28.

FIG. 6 is a graph showing the relationship of FIG. 5 for five sets of openings.

FIG. 7 is a graph showing the output of the focus detection system 29 with respect to the image height.

8 is a graph showing the output of the focus detection system 29 with respect to the image height, in which the image plane tilt component and the image plane curvature component are extracted from the graph of FIG.

FIG. 9 is a diagram illustrating removal of field curvature.

FIG. 10 is an explanatory diagram when only half of the exposure area is used.

FIG. 11 is a diagram illustrating a phase grating pattern.

FIG. 12 shows a case where a phase grating pattern is used,
The figure which shows the relationship between the focus detection system 29 and the output of the photoelectric detector 28.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 2 shutter 14 Z stage 15 XY stage 19 interferometer 20 reference member 21 aperture 28 photoelectric detector 29 focus detection system 30 horizontal position detection system 32 main control system 32A focused position detection unit 32B imaging characteristic detection unit 33 drive element Control system 40, 41, 43, 45 Lens element 48, 49, 50 Driving element R Reticle W Wafer PL Projection optical system

Claims (3)

[Claims] 1. A first illumination system for uniformly illuminating a mask having a predetermined mask pattern with exposure light, a projection optical system for forming an image of the mask pattern in a predetermined image plane, and A projection exposure apparatus having a stage that holds a photosensitive substrate so as to substantially coincide with a predetermined image plane and is movable in the optical axis direction of the projection optical system and in a direction perpendicular to the optical axis. A reference member that is arranged and has a plurality of minute openings formed on the surface in a predetermined arrangement relationship; and illuminating the plurality of minute openings from the stage side with the exposure light or light having a wavelength substantially equal to the exposure light. A second illumination system that causes the transmitted light that has passed through the plurality of minute openings to enter the mask through the projection optical system; and out of the light that reaches the mask by illumination by the second illumination system. , Anti-mask Then, the photoelectric detection has a light receiving surface for individually receiving the reflected light transmitted through each of the plurality of minute apertures through the projection optical system, and individually outputs a photoelectric signal according to each received light amount. Each of the plurality of minute apertures on the predetermined image plane based on each photoelectric signal output from the photoelectric detection unit when the stage is moved in the optical axis direction of the projection optical system. Image plane state detecting means for detecting a position in the optical axis direction at a position; focus position of the projection optical system, image plane inclination, and image plane curvature based on each position information detected by the image plane state detecting means And an image forming characteristic detecting unit for calculating at least one characteristic of the projection exposing apparatus. 2. By driving a part of the optical element of the projection optical system or a part of the stage based on the measurement value obtained by the image formation characteristic detecting means,
The projection exposure apparatus according to claim 1, further comprising an image formation characteristic correction unit that corrects an image formation characteristic of the projection optical system. 3. The projection exposure apparatus according to claim 1, wherein each of the plurality of minute openings is provided with a checkered pattern or a grid pattern.