JPH05343292A - Exposure apparatus - Google Patents

Abstract

PURPOSE:To accurately measure a distortion aberration of a projecting optical system by correcting an oblique angle of an exposure optical axis. CONSTITUTION:A cross-shaped pattern WM on a stage board 21 is irradiated with an exposure light passed through a reticle R and a projecting optical system PL, and an image of a measuring mark RM on the pattern WM and the reticle R is observed by an imaging element 40 through an observing optical system VF, etc. An oblique angle correcting optical system 12 for correcting the oblique angle to an optical axis AX of a main light ray of the exposure light is disposed in illuminating optical systems 11, 17, 19, and telecentricity of the exposure light for the pattern WM is proved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus equipped with, for example, a distortion aberration measuring mechanism of a projection optical system.

[0002]

2. Description of the Related Art A projection exposure apparatus for transferring a reticle pattern onto a wafer through a projection optical system is used when manufacturing a semiconductor element, a liquid crystal display element or the like by using a photolithography technique. One of the important performances of such a projection exposure apparatus is the overlay accuracy, and the main factors affecting this overlay accuracy are the magnification error and distortion of the projection optical system. For example, the line width of patterns used in VLSI and the like is becoming finer year by year, and there is an increasing demand for improvement in overlay accuracy on a wafer. Therefore, there is an increasing need to keep the magnification error and distortion of the projection optical system within a predetermined range.

In this regard, if the distance between the reticle and the projection optical system and the relative position of each lens element inside the projection optical system do not change, the overlay error due to the magnification error and the distortion aberration is constant. Such an overlay error can be said to be a systematic error. Then, for example, if the relative position of each lens element inside the projection optical system changes due to absorption of exposure light for a long time, the magnification error and the distortion aberration may change. A mechanism capable of measuring the state of distortion has been developed (see, for example, Japanese Patent Laid-Open No. 59-94032). The magnification error can be measured simultaneously by a distortion aberration measuring mechanism.

A conventional distortion aberration measuring mechanism uses a reticle on which a large number of marks for distortion aberration measurement are formed and a measurement pattern formed on the wafer stage side, and moves the wafer stage to move the projection optical system. The measurement pattern is two-dimensionally moved within the exposure area. The measurement pattern is illuminated with light having the same wavelength as the exposure light, and the two-dimensional coordinates of the wafer stage when the conjugate image of the measurement pattern by the projection optical system matches the measurement marks on the reticle side. To detect. The difference between the detected two-dimensional coordinates and the two-dimensional coordinates obtained by multiplying the two-dimensional coordinates of the reticle measurement mark by the projection magnification of the projection optical system is the distortion aberration.

In this case, the method of illuminating the measurement pattern on the wafer stage side is the first method in which the exposure light emitted from the illumination optical system toward the reticle is used, and the exposure light is transmitted through the light guide or the like to the wafer stage. There is a second method in which the exposure light is guided from the wafer stage side, and a third method in which the exposure light is independently illuminated by the illumination light from the measurement microscope. In the present application, the case of illuminating the measurement pattern on the wafer stage side by the first method is dealt with.

[0006]

Generally, in a projection exposure apparatus, the projection optical system is telecentric at least on the wafer side. However, when the exposure pattern emitted from the illumination optical system to the reticle side is used to illuminate the measurement pattern on the wafer stage side via the projection optical system, the telecentricity of the exposure light with respect to this measurement pattern is used. However, there is a disadvantage that the exposure area of the projection optical system is not always guaranteed. Therefore, asymmetry or distortion may occur in the conjugate image of the measurement pattern on the wafer stage side by the projection optical system, and an error may occur in the position measurement of the conjugate image on the reticle.

In view of such a point, the present invention has an object to provide an exposure apparatus capable of measuring distortion aberration of a projection optical system with higher accuracy.

[0008]

An exposure apparatus according to the present invention is, for example, as shown in FIG. 1, a light source (1) for generating exposure light, and an illumination optical system for condensing the exposure light and illuminating a mask R. (8, 11, 17, 19) and a projection optical system PL for transferring the pattern of the mask R onto the photosensitive substrate W on the stage (20) under the exposure light, and the mask R by the illumination optical system. The inclination correction means (13, 14) for partially correcting the inclination angle of the principal ray of the exposure light irradiated to the optical axis AX of the illumination optical system, and the inclination angle of the principal ray by this inclination correction means. The first mark RM on the mask R illuminated by the corrected exposure light and the exposure light whose inclination angle of the chief ray is corrected by the inclination correction means, the mask R and the projection optical system P.
Image pickup means (31, 32, 40) for detecting the positional relationship of each mark image with the second mark WM on the stage (20) illuminated through L, and each mark image detected by this image pickup means And an image forming characteristic control means (7, 29) for controlling the image forming characteristic of the projection optical system PL in accordance with the positional relationship of.

[0009]

According to the present invention, the inclination correcting means (1
3, 14), the inclination angle of the principal ray of the exposure light with which the mask R is irradiated with respect to the optical axis AX of the illumination optical system can be partially corrected. Then, stage (20)
By the inclination correction means (13, 14), the exposure light that illuminates the second mark WM formed above via the projection optical system PL becomes telecentric at the current position of the second mark WM. adjust. As a result, even if the second mark WM moves to any position in the exposure area of the projection optical system PL, the telecentricity of the exposure light with respect to the second mark WM can always be guaranteed, and the distortion aberration can be highly accurate. Can be measured.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of an exposure apparatus according to the present invention will be described below with reference to FIG. In this embodiment, the present invention is applied to a reduction projection type exposure apparatus (stepper) having a distortion aberration measuring mechanism of a projection optical system.

FIG. 1 shows the overall structure of the exposure apparatus of this embodiment. In FIG. 1, 1 is a mercury lamp. The exposure light IL from the mercury lamp 1 is focused by the elliptic mirror 2, reflected by the mirror 3, and then converted into a substantially parallel light flux by the input lens 4. A shutter 5 is arranged between the ellipsoidal mirror 2 and the mirror 3, and the shutter 5 is closed by the drive motor 6 so that the supply of the exposure light IL to the input lens 4 can be stopped. Reference numeral 7 denotes a main control system that controls the operation of the entire apparatus, and the main control system 7 controls the operation of the drive motor 6. In addition to the mercury lamp 1, a pulsed laser light source such as a KrF excimer laser or other light source is used.

When the shutter 5 is in the open state, the exposure light IL emitted from the input lens 4 is incident on the fly-eye lens 8 as an optical integrator and is emitted to the exit side (reticle R side) of the fly-eye lens 8. A large number of secondary light sources are formed on the focal plane. A variable aperture diaphragm 9 is arranged on the surface on which the secondary light source is formed, and the main control system 7 sets the shape of the opening of the variable aperture diaphragm 9 to a shape corresponding to the reticle to be transferred, via a driving device 10. To do. During exposure of the wafer W, the opening of the variable aperture stop 9, that is, the exposure light IL emitted from the secondary light source, is emitted by the first relay lens 1
1, reticle blind 15, second relay lens 17,
The reticle R is illuminated with a substantially uniform illuminance after being focused appropriately through the mirror 18 and the main condenser lens 19.

The reticle blind 15 and the pattern forming surface of the reticle R are conjugated, and the reticle blind 15
The illumination field of the reticle R is set by the opening. Further, when measuring the distortion aberration, the tilt angle correction optical system 12 is provided immediately before the reticle blind 15 on the first relay lens 11 side.
Are placed. The tilt angle correction optical system 12 is configured by disposing two deflection angle prisms 13 and 14 along the optical axis AX of the illumination optical system.
By changing the relative rotation angle around the optical axis AX of, the tilt angle of the principal ray of the exposure light passing through the opening of the subsequent reticle blind 15 with respect to the optical axis AX can be adjusted. Further, by rotating the deflection angle prisms 13 and 14 integrally around the optical axis AX, the principal ray of the exposure light can be rotated around the optical axis AX. The main control system 7 includes a reticle blind 15 via a drive unit 16.
Position and size of the aperture of the deviation angle prisms 13 and 14
And the integral rotation angle of the deflection prisms 13 and 14 is set to a predetermined state.

In the pattern area of the reticle R of this example, a large number of rectangular frame-shaped measuring marks RM are formed in a matrix. These measurement marks RM are the projection optical system PL
It is used to measure the distortion aberration of. When the wafer W is exposed, the exposure light IL that has passed through the pattern area of the reticle R
Are focused on the shot area on the wafer W by the projection optical system PL, so that the pattern of the reticle R is changed to the wafer W.
Is transferred to the shot area at a predetermined reduction ratio. The Fourier transform plane (pupil plane) of the projection optical system PL is conjugate with the secondary light source formation surface of the fly-eye lens 8. Also, the wafer W
Is held on the wafer stage 20, and the wafer stage 2
0 indicates an XY stage that two-dimensionally positions the wafer W in a plane (XY plane) perpendicular to the optical axis of the projection optical system PL and the wafer W in the direction (Z direction) parallel to the optical axis of the projection optical system PL. It is composed of a Z stage and the like for positioning.

A light-transmissive stage substrate 21 is attached in the vicinity of the wafer W on the wafer stage 20, and the surface of the stage substrate 21 is set at the same height as the exposed surface of the wafer W. A cross-shaped pattern WM for measuring distortion aberration is formed on the stage substrate 21. As will be described later, the cross-shaped pattern WM is illuminated by exposure light that is transmitted through the reticle R in the vicinity of the measurement mark RM and is emitted via the projection optical system PL.

A moving mirror 23 for reflecting the laser beam of the laser interferometer 24 is fixed on the wafer stage 20, and the laser interferometer 24 measures the two-dimensional coordinates of the XY stage in the wafer stage 20. The main control system 7 positions the wafer stage 20 via the drive unit 25 while monitoring the two-dimensional coordinates measured by the laser interferometer 24. Reference numeral 26 denotes an irradiation optical system of the focus detection system, and 27 denotes a light receiving optical system of the focus detection system. The irradiation optical system 26 obliquely projects an image of, for example, a slit pattern at a predetermined position in the exposure area of the projection optical system PL. Light receiving optical system 2
7 re-images the image of the slit pattern on, for example, a vibrating slit plate. A light receiving element is arranged on the back surface of the vibrating slit plate, and a detection signal of the light receiving element is synchronously rectified by a drive signal of the vibrating slit plate so that an object in the exposure area of the projection optical system PL is projected onto the projection optical system. A focus signal having a predetermined level is obtained when the focus signal matches the focal plane of PL. The main control system 7 controls the operation of the Z stage in the wafer stage 20 via the drive unit 25 so that the focus signal becomes a predetermined level. As a result, autofocus control is performed.

A variable aperture stop 2 is provided on the pupil plane of the projection optical system PL.
8 is provided, and the main control system 7 sets the aperture state of the variable aperture stop 28. Further, the main control system 7 finely adjusts the tilt angle of the reticle R with respect to the plane perpendicular to the optical axis of the projection optical system PL via the drive unit 29. By this fine adjustment, the state of distortion of the projection optical system PL can be adjusted to some extent. In addition, for example, a mechanism for adjusting the pressure of a predetermined air chamber of the projection optical system PL, a mechanism for adjusting the distance between the lens groups forming the projection optical system PL, or the like may be provided. Through these mechanisms, the main control system 7 can adjust the imaging characteristics such as magnification error and distortion of the projection optical system PL within a predetermined range.

When measuring the distortion of the projection optical system PL, the stage substrate 21 is placed in the exposure area of the projection optical system PL.
Cross pattern WM is arranged. Then, above the measurement mark RM on the reticle R at a position conjugate with the cross-shaped pattern WM, the beam splitter 31 and the first mark are formed.
An observation optical system VF including the objective lens 32 is movably arranged in a plane perpendicular to the optical axis of the projection optical system PL. In response to moving the cross pattern WM by moving the XY stage in the wafer stage 20, the main control system 7 moves the observation optical system VF above the reticle R via the drive unit 30.

At the time of measuring the distortion aberration, the exposure light emitted from the opening of the reticle blind 15 after the inclination angle of the principal ray with respect to the optical axis AX is corrected by the inclination angle correction optical system 12, the second relay lens 17, The exposure light that has been irradiated to the vicinity of the measurement mark RM via the mirror 18, the main condenser lens 19 and the beam splitter 31 and that has transmitted through the vicinity of the measurement mark RM passes through the projection optical system PL and is on the stage substrate 21. Illuminate the character pattern WM.
The exposure light reflected from the cross pattern WM passes through the projection optical system PL and the measurement mark RM of the reticle R and enters the beam splitter 31. In parallel, the exposure light reflected from the measurement mark RM itself of the reticle R also enters the beam splitter 31.

The exposure light from the measurement mark RM and the exposure light from the cross pattern WM reflected by the beam splitter 31 pass through the first objective lens 32 and then enter the beam splitter 34 through the optical path length correction means 33. .. The optical path length correction unit 33 corrects the optical path length of the exposure light passing through the inside so as to cancel the movement amount of the observation optical system VF according to the control signal supplied from the main control system 7 via the driving device 30. .. The exposure light reflected by the beam splitter 34 is focused by the second objective lens 35, and the reticle R
Measurement mark RM on the surface P1 which is conjugate with the pattern formation surface of
And an image of the cross pattern WM is formed. The exposure light from these images is further subjected to the first relay lens 36, the optical axis correcting means 37, the variable aperture stop 38 and the second relay lens 39.
Is focused on the image pickup surface of the image pickup element 40 formed of a two-dimensional CCD, and the measurement mark RM
And an image of the cross pattern WM is formed.

In this case, the optical axis correcting means 37 corrects the tilt angle of the principal ray of the exposure light of the image of the cross pattern WM which is tilted by the tilt angle correcting optical system 12 and enters the reticle R with respect to the reticle R, The variable aperture stop 38 is the projection element 4
The measurement mark RM and the cross-shaped pattern WM that enter 0 determine the state of the light flux of each image, and the second relay lens 38 moves in the optical axis direction to move the measurement mark RM and the cross-shaped pattern WM.
Focus each image. The main control system 7 controls the correction operation of the optical axis correction means 37, the shape of the opening of the variable aperture stop 38, and the moving position of the second relay lens 39 via the drive device 41. The tilt angle correction optical system 12 is driven according to a correction program predetermined for each measurement position on the reticle. In determining the shape of the aperture of the variable aperture stop 38, the variable aperture stop 2 on the pupil plane of the projection optical system PL is used.
The shape of the aperture of the variable aperture stop 38 may be set independently, although it may be adjusted in conjunction with the shape of the aperture of No. 8. To move the position of the second relay lens 39, first, the exposure light transmitted through the beam splitter 34 is received by the focus detection means 42. This focus detection means 4
Reference numeral 2 detects a focus shift caused by variations in the reticle thickness at the measurement position on the reticle R of the image of the measurement mark RM and the image of the cross pattern WM on the image pickup surface of the two-dimensional CCD image pickup device 40, and this detection is performed. The information on the focused state is supplied to the main control system 7, and from this information, the main control system 7 corrects the focus by moving the second relay lens 39 via the driving device 41. By these three correction operations, the vignetting of the light flux of the image of the measurement mark RM and the cross-shaped pattern WM is eliminated, the imaging characteristics are optimized, and the C of the measurement mark RM image and the cross-shaped pattern WM image due to defocusing is optimized.
Since it is possible to prevent the positional deviation on the CD, it is possible to further reduce the detection error at the time of measuring the later-described distortion aberration.

Next, the operation when measuring the distortion aberration of the projection optical system PL will be described in detail. In this case, the tilt angle correction optical system 12 is arranged immediately before the reticle blind 15, and the position of the opening of the reticle blind 15 is set near the conjugate position of the measurement mark RM to be measured on the reticle R. The size of the opening of the reticle blind 15 is set to a size that illuminates only a predetermined area near the measurement mark RM. Then, the chief ray of the exposure light, which has passed through the vicinity of the measurement mark RM and then is irradiated onto the cross-shaped pattern WM on the stage substrate 21 via the projection optical system PL, becomes perpendicular to the stage substrate 21. Thus, the tilt angle correction optical system 12 adjusts the tilt angle of the principal ray of the exposure light. The adjustment state of the tilt angle in the tilt angle correction optical system 12 is stored in advance in the storage means inside the main control system 7 in correspondence with the measurement coordinates on the reticle R, for example.

In this state, the main control system 7 detects the positional relationship between the image of the measuring mark RM on the reticle R and the image of the cross-shaped pattern WM on the stage substrate 21 via the image pickup means 40. Similarly, the main control system 7 moves the cross-shaped pattern WM on the stage substrate 21 two-dimensionally within the exposure area of the projection optical system PL, and the images of a large number of measurement marks RM on the reticle R and their tenths. The positional relationship between the character pattern WM and the image is detected. Since the state of the distortion of the projection optical system PL can be known from this, the main control system 7 is, for example, the drive unit 2.
The projection optical system P by adjusting the tilt angle of the reticle R via
The state of distortion of L is adjusted to a predetermined state. In this way, although the distortion aberration measurement is completed, as a method for further preventing the measurement error, when detecting the positional deviation between the measurement mark RM image and the cross-shaped pattern WM image on the image pickup means 40, this image pickup means is used. The absolute position of the cross-shaped pattern WM image on 40 is also detected, and this position information is stored in the main control system 7.

In FIG. 1, reference numeral 44 denotes a light guide. One end of the light guide 44 is arranged near the shutter 5, and the other end of the light guide 44 is housed in the wafer stage 20. In the state where the shutter 5 is closed, the exposure light IL reflected by the shutter 5 is focused on one end surface of the light guide 44 by the condenser lens 43, and the exposure light IL is emitted from the other end surface of the light guide 44 in the wafer stage 20. Is ejected. The emitted exposure light is converted into a substantially parallel light flux by the condenser lens 45, and then is reflected by the mirror 46 to illuminate the opening mark 22 on the stage substrate 21 vertically upward from the bottom surface side. This 2
2 determines the Teruno. Therefore, when the wafer stage 20 is moved to cause the aperture mark 22 to emit light near the conjugate position of the measurement mark RM via the projection optical system PL, the aperture mark 22 emitted perpendicularly to the stage substrate 21. The exposure light from the measurement mark RM on the reticle R at its conjugate position passes through the projection optical system PL.
Illuminate through. Unlike the reflected light from the measurement mark RM, the principal ray of the light beam illuminated and emitted from the measurement mark RM has the same inclination angle as the principal ray of the cross pattern WM and the reticle R when it is emitted. Will be done. The position of the measurement mark RM image on the image pickup means 40 is detected, and the difference from the position of the cross-shaped pattern WM image stored previously is the detected value. By using such a detection method, it is possible to prevent the detection accuracy from deteriorating even if there is insufficient focusing due to an error in the movement of the focus detection unit 42 or the second relay lens 39 which is the focusing mechanism.

Next, another example of an optical system capable of correcting the tilt angle of the principal ray of the exposure light, similar to the tilt angle correction optical system 12 in the first embodiment of FIG. 1, will be described with reference to FIG. First,
FIG. 2A shows an example in which the tilt angle of the chief ray of the exposure light is corrected using a field lens. In FIG. 2A, a field lens 47 having a visual field capable of covering the measurement region of the measurement mark RM on the reticle R is arranged immediately in front of the opening of the reticle blind 15 on the first relay lens 11 side. The field lens 47 is removed during normal exposure. Further, when measuring the distortion aberration of the projection optical system, the field lens 47 is two-dimensionally moved immediately before the reticle blind 15 in response to the movement of the opening of the reticle blind 15.

FIG. 2B shows an example in which the tilt angle of the chief ray of the exposure light is corrected by using the variable aperture stop 9 on the secondary light source forming surface of the fly-eye lens 8. In this case, with the aperture of the variable aperture diaphragm 9 narrowed down,
When it is moved dimensionally, the exposure light irradiated on the reticle R in FIG. 1 becomes a parallel light beam, and the inclination angle of this parallel light beam with respect to the optical axis of the projection optical system PL is corrected as a whole.

Further, FIG. 2C shows an example using two parallel flat glass plates. In FIG. 2C, a space between the variable aperture stop 9 and the first relay lens 11 is arranged along the optical axis. ,
A first parallel flat glass plate 48 rotatably arranged around an axis 48a perpendicular to the plane of FIG.
The second parallel plate glass 49 is provided so as to be rotatable about an axis 49a parallel to the paper surface of (c). By adjusting the rotation angles of the two parallel plate glasses 48 and 49, the inclination angle of the principal ray of the exposure light emitted from the opening of the reticle blind 15 can be arbitrarily adjusted.

Next, a second embodiment of the present invention will be described with reference to FIG. 3 in which parts corresponding to those in FIG. FIG. 3 shows the main part of the projection exposure apparatus of this example. In FIG. 3, the cross-shaped pattern W on the stage substrate 21 is shown.
A second objective lens 55, a second parallel plate glass 54 rotatable around an axis perpendicular to the plane of FIG. 3, and a second tilted mirror 53 are arranged below M in this order. Further, the first tilting mirror 52 is arranged so as to form a wedge shape with respect to the second tilting mirror 53, and the first tilting mirror 52 is rotatable above the first tilting mirror 52 about an axis parallel to the paper surface of FIG. The flat glass 51 and the first objective lens 50 are arranged. The main control system 7 adjusts the rotation angles of the two parallel plate glasses 51 and 54 via the drive device 56.

At the time of measuring the distortion of the projection optical system PL, the aperture of the reticle blind 15 is made small and the position of the aperture is shifted so that the measurement mark RM to be measured on the reticle R by the exposure light. Illuminates the area adjacent to. As a result, the area adjacent to the cross pattern WM on the stage substrate 21 is illuminated with the exposure light that has passed through the reticle R and the projection optical system PL. The exposure light from the irradiation area on the stage substrate 21 is transferred to the first objective lens 5
The cross-shaped pattern WM on the stage substrate 21 is irradiated with 0, the first parallel flat glass 51, the first tilt mirror 52, the second tilt mirror 53, the second parallel flat glass 54, and the second objective lens 55. The exposure light irradiation region on the stage substrate 21 and the formation region of the cross-shaped pattern WM are conjugated.

In this case, the tilt angle of the principal ray of the exposure light illuminating the cross pattern WM from the bottom with respect to the optical axis of the projection optical system PL is adjusted by adjusting the rotation angles of the two parallel flat glass plates 51 and 54, respectively. Can be set to 0 to ensure the telecentricity of the exposure light with respect to the cross pattern WM of the stage substrate 21. Further, the images of the cross-shaped pattern WM on the stage substrate 21 and the measurement mark RM on the reticle R can be picked up through the observation optical system VF as in the first embodiment.

Next, a third embodiment of the present invention will be described with reference to FIG. 4 in which parts corresponding to those in FIG. FIG. 4 shows the main part of the projection exposure apparatus of this example. In FIG. 4, no mark for distortion aberration measurement is formed on the stage substrate 21. Then, inside the wafer stage 20, a first objective lens 58, a parallel flat glass plate 54 rotatable around an axis perpendicular to the paper surface of FIG. 4, and an axis parallel to the paper surface of FIG. A rotatable parallel flat plate glass 51, a second objective lens 57 and a reflecting plate 59 are arranged at the center, and a cross-shaped pattern WM for measuring distortion aberration is formed on the reflecting plate 59. First objective lens 58
The upper surface of the stage substrate 21 and the surface of the reflection plate 59 are conjugated with each other by the second objective lens 57.

In FIG. 4, at the time of measuring the distortion of the projection optical system PL, the aperture of the reticle blind 15 is made small and the position of the aperture is shifted so that the exposure light is used as a measurement target on the reticle R. The area in the vicinity of the mark RM is illuminated. As a result, the corresponding area on the stage substrate 21 is illuminated with the exposure light that has passed through the reticle R and the projection optical system PL. The exposure light from the irradiation area on the stage substrate 21 is applied to the cross-shaped pattern WM on the reflecting plate 59 via the first objective lens 58, the parallel plate glass 54, the parallel plate glass 51, and the second objective lens 57. The main control system 7 adjusts the rotation angles of the two parallel plate glasses 54 and 51 via the drive unit 56, so that the telecentricity of the exposure light with respect to the cross pattern WM can be guaranteed.

Furthermore, the cross-shaped pattern WM on the reflection plate 59
Image is relayed on the stage substrate 21 and then relayed on the reticle R. Then, the images of the cross-shaped pattern WM on the reflection plate 59 and the measurement mark RM on the reticle R can be picked up via the observation optical system VF in the same manner as in the first embodiment.

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 5A is a plan view of the reticle R of this example. In FIG. 5A, two observation optical systems VFA and VFB corresponding to the observation optical system VF of FIG. 1 are located above the reticle R. It is arranged. One observation optical system V
FA is the beam splitter 31A and the first objective lens 3
2A, and the other observation optical system VFB also includes a beam splitter 31B and a first objective lens 32B. The observation optical systems VFA and VFB are provided with the optical systems 33 to 40 and 42 of FIG. 1, respectively. By using a plurality of observation optical systems in this way, the measurement efficiency of distortion can be improved.

However, in this example, the optical axis of the observation optical system VFA and the optical axis of the observation optical system VFB are separated by a variable length L in the direction parallel to the reticle R, and the observation optical system V
Move FA and VFB. FIG. 5B is a side view of the reticle R of this example, showing the observation optical systems VFA and VFA.
By separating the optical axis of FB, the beam splitter 31
The reflected lights ILA and ILB from A and 31B are prevented from becoming noise of the other observation optical system, and the measurement accuracy can be improved. In addition, a plurality of observation optical systems V
Instead of shifting the optical axes of FA and VFB in a direction parallel to reticle R, the optical axes of observation optical systems VFA and VFB may be shifted in the height direction (the optical axis direction of the projection optical system).

Further, in order to prevent noise of reflected light between a plurality of observation optical systems, wedge prisms 60A and 60B may be used as beam splitters as shown in FIG. By using the surfaces 60Aa and 60Ba of the wedge prisms 60A and 60B on the reticle R side as beam splitter surfaces, it is possible to prevent reflected light from directly entering the other observation optical system.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0038]

According to the present invention, since the inclination angle of the principal ray of the exposure light with respect to the optical axis of the illumination optical system can be corrected, the telecentricity of the exposure light with respect to the second mark on the stage can be maintained. Therefore, there is an advantage that the distortion of the projection optical system can be measured with higher accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram including a partial sectional view showing an entire first embodiment of an exposure apparatus according to the present invention.

FIG. 2 is a configuration diagram of a main part showing a modified example of the first embodiment.

FIG. 3 is a configuration diagram including a partial cross-sectional view showing an essential part of a second embodiment of the present invention.

FIG. 4 is a configuration diagram including a partial cross-sectional view showing an essential part of a third embodiment of the present invention.

5A is a plan view showing a configuration near a reticle according to a fourth embodiment of the present invention, and FIG. 5B is a side view of FIG. 5A.

FIG. 6 is a side view showing a main part of a modified example of the fourth embodiment.

[Explanation of symbols]

 1 Mercury Lamp 7 Main Control System 8 Fly's Eye Lens 9 Aperture Stopper 11 First Relay Lens 12 Tilt Angle Correction Optical System 15 Reticle Blind 17 Second Relay Lens 19 Main Condenser Lens R Reticle PL Projection Optical System W Wafer RM Measurement Mark WM Cross pattern 20 Wafer stage 21 Stage substrate VF Observation optical system 33 Optical path length correction means 37 Optical axis correction means

Claims (1)

[Claims] 1. A light source that generates exposure light, an illumination optical system that condenses the exposure light and illuminates a mask, and transfers the pattern of the mask onto a photosensitive substrate on a stage under the exposure light. A projection optical system, a tilt correction means for partially correcting a tilt angle of a chief ray of the exposure light with which the illumination optical system is irradiated on the mask with respect to an optical axis of the illumination optical system, and the tilt correction means The first mark on the mask illuminated by the exposure light whose inclination angle of the chief ray is corrected and the exposure light whose inclination angle of the principal ray is corrected by the inclination correcting means, and the mask and the projection optical system. Imaging means for detecting the positional relationship between each mark image and the second mark on the stage illuminated through the system, and the projection optical system according to the positional relationship between each mark image detected by the imaging means. Exposure apparatus, characterized in that it has a imaging characteristics control means for controlling the imaging properties.