JPH06267820A - Position detector - Google Patents

Abstract

PURPOSE:To more accurately detect the two-dimensional position of an object to be detected, by correcting the astigmatism generated in an optical system for position detection. CONSTITUTION:The pattern of a reticle R is exposed on a wafer W via a projection aligner. In an alignment system 4 on the side surface of the projection aligner, the alignment light from a wafer mark WM on the wafer W forms an image of the wafer mark WM on a focal plate 11, through an objective 7, a beam splitter 6, a negative cylindrical lens 8, and a positive cylindrical lens 9. The image on the focal plate 11 is picked up by image sensing elements 13M and 13S, via an imagery lens 11. By changing the absolute rotation angles of the cylirxdrical lenses 8, 9 or the relative rotation angle or the interval, the astigmatism generated by the objective 7 and the beam spitter 6 us cancelled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device for detecting the position of an object to be inspected, and particularly in a projection exposure apparatus used for manufacturing a semiconductor element, a liquid crystal display element or the like, a circuit pattern is formed. The present invention relates to a position detection device suitable for application to an alignment device for relatively aligning (aligning) the reticle formed with the photosensitive substrate onto which the circuit pattern is transferred.

[0002]

2. Description of the Related Art When manufacturing a semiconductor device, a liquid crystal display device, or the like by a photolithography process, a photomask or reticle (hereinafter referred to as "reticle") pattern coated with a photoresist at high resolution is used. , A projection exposure apparatus for transfer onto a photosensitive substrate is used. As such a projection exposure apparatus, a step-and-repeat type reduction projection exposure apparatus (so-called stepper) is often used. In general, a semiconductor element is formed by stacking a large number of circuit patterns on a wafer, and therefore, a stepper forms a projected image of a reticle pattern to be exposed and a matrix formed on the wafer by the steps up to that point. An alignment device is provided for accurately overlapping the existing circuit pattern (chip).

Such an alignment apparatus has an alignment mark (reticle mark) formed on a reticle.
And the positional relationship between the alignment marks (wafer marks) formed on the wafer by the steps up to that,
The reticle and each shot area of the wafer are aligned with each other. Therefore, in the alignment apparatus, first, the alignment system for detecting the positions of the reticle mark and the wafer mark plays an important role.

As a conventional alignment apparatus, for example, Japanese Patent Application Laid-Open No. 60-130742 discloses an alignment apparatus of TTL (through the lens) type and laser step alignment type. The laser step alignment type alignment system
An elongated strip-shaped spot light is irradiated onto a diffraction grating wafer mark through a projection optical system, and diffracted light (or scattered light) generated from the wafer mark is photoelectrically detected.

A so-called die-by-die type alignment apparatus is known as another conventional alignment apparatus.
In this method, as the alignment light, light having an exposure wavelength for exposing a circuit pattern or white light in a wide band is mainly used, and a reticle mark and a wafer mark are exposed before each shot area on the wafer is exposed. And are detected individually or simultaneously. As the alignment system for the die-by-die system, an alignment system for photoelectrically detecting a wafer mark or the like similar to the laser step alignment system, or a CC image for reticle mark and wafer mark is used.
An FIA (field image alignment) type alignment system has been used which detects a position by capturing an image with a D camera or the like and processing it as image data.

[0006]

In the prior art as described above, when the position of the reticle mark and the wafer mark is detected by the FIA type alignment system, a reticle mark is usually used by using a one-dimensional image pickup device. Also, the wafer mark is displayed on the screen of the monitor receiver, for example, and the positional deviation of each mark is obtained from the state of the image on the screen.

By the way, since the object to be detected is the position in the two-dimensional coordinates consisting of the X coordinate and the Y coordinate, in order to detect the position in the two-dimensional coordinates by using the one-dimensional image sensor, at least two lines are required. It is necessary to use a one-dimensional image sensor or rotate the one-dimensional image sensor within two-dimensional coordinates. In this case, since the method of rotating the one-dimensional image sensor lacks stability, conventionally, two one-dimensional image sensors are used by dividing the optical path from each mark. However, when two one-dimensional image pickup devices are used in this way, two display screens corresponding to the two one-dimensional image pickup devices are generated due to astigmatism caused by an assembly error of the optical system for position detection and the like. However, there is a disadvantage in that one or both of the images are blurred and the position cannot be accurately detected by image processing.

However, when the amount of the astigmatism is fixed, the influence of the astigmatism can be eliminated by adjusting the positions of the image pickup surfaces of the two one-dimensional image pickup devices. . However, even in this case, if the amount of astigmatism changes due to external conditions such as temperature, it is necessary to readjust the positions of the image pickup surfaces of the two one-dimensional image pickup elements. Such readjustment is difficult.

Further, when the position of the wafer mark is detected by the FIA type alignment system, the optical system is simplified by using the two-dimensional image pickup device. However, 2
When a three-dimensional image sensor is used, images in two directions are
Since the image is picked up by one image pickup surface, the astigmatism cannot be corrected by shifting the position of the image pickup element, and the influence of the astigmatism caused by the optical system for position detection becomes particularly large. Further, in the alignment system of the laser step alignment method described above, imaging is not performed by the image sensor, but in order to detect the position more accurately, astigmatism in the optical system for position detection should be reduced. Is desirable.

In view of such a point, the present invention guides the light for position detection from the measurement mark on the object to be examined onto the observation surface through the position detection optical system, and detects the position on the observation surface. In a position detection device that detects the position of an object to be inspected from the position of the light for inspection, it is possible to correct the astigmatism generated in the optical system for position detection to more accurately detect the position of the object to be inspected. To aim.

[0011]

A first position detecting device according to the present invention detects a position detecting light from a measuring mark (WM) on an object (W) as shown in FIG. 1, for example. In a device which guides light onto an observation surface (10) through a detection optical system (6, 7) and detects the position of a test object (W) from the position of light for detecting the position on the observation surface (10). , Test object (W)
A first toric lens (8) and a second toric lens (9) are arranged along the optical path of the light for position detection between the lens and the observation surface (10), and at least one of these two toric lenses is arranged. Of the toric lens is provided so as to be rotatable about the optical axis of the lens or movable along the optical axis, and its position can be detected by rotating or moving at least one of the two toric lenses. Position detection optical system (6
The astigmatism generated in 7) is corrected.

The second position detecting device according to the present invention, as shown in FIG. 1, for example, condenses the position detecting light from the measuring mark (WM) on the object (W) to be used as a reference. A position detection optical system (6, which forms an image of the measurement mark (WM) on the reference mark plate (10) on which the mark (IM) is formed.
7), reference mark (IM) and measurement mark (WM)
Means for detecting the two-dimensional displacement of the image of the
1, 12, 13M, 13S), and the reference mark (I
M) and a device for detecting the position of the test object (W) from the amount of positional deviation between the image of the measurement mark (WM) and its position between the test object (W) and the reference mark plate (10). A first toric lens (8) and a second toric lens (9) are arranged along the optical path of the detection light, and at least one toric lens of these two toric lenses is centered on the optical axis of this lens. A drive means (50) that rotates or moves along this optical axis is provided, and by rotating or moving at least one of the two toric lenses, the position detection light is detected. The astigmatism generated in the position detection optical system (6, 7) is corrected.

Further, in the third position detecting device according to the present invention, as shown in FIG. 8, for example, the image of the pattern formed on the mask (R) is passed through the projection optical system (PL) to the photosensitive substrate (W). It is provided in the exposure device for projecting on the projection optical system (P) from the measurement mark (WM) on the photosensitive substrate (W).
Position detection optical system (PL, 28, 27, 29) that collects the light for position detection obtained via L) and forms an image of the measurement mark (WM) on the observation surface (imaging surface of 35). , 54,
36, 34) and measuring means (35, 4) for detecting the two-dimensional positional deviation amount of the image of the measuring mark on the observation surface.
1) and a position detection device for detecting the position of the photosensitive substrate (W) from the amount of positional deviation of the image of the measurement mark (WM), the position detection device between the projection optical system (PL) and its observation surface. A first toric lens (9) and a second toric lens (8) are arranged along the optical path of the light for position detection, and at least one of the two toric lenses is placed around the optical axis of this lens. Rotatably or movably along the optical axis, and by rotating or moving at least one toric lens of the two toric lenses, the projection optical system is adapted to the position detecting light. The astigmatism that occurs is corrected.

[0014]

According to the first position detecting device of the present invention,
A correction optical system having first and second optical members for correcting astigmatism is provided, and two toric lenses (8, 9) are used as the first and second optical members. Generally, a toric lens is a lens having different refractive powers in two directions orthogonal to each other in a plane perpendicular to the optical axis, and the rotation angle (absolute rotation angle) of the two toric lenses as a unit and the relative rotation of the two toric lenses. By changing the angle or the interval, it is possible to change the shift amount of the focal position of the light passing through the two toric lenses in two directions orthogonal to each other. In other words, by changing the absolute rotation angle, the relative rotation angle, or the distance between the two toric lenses, it is possible to give a desired amount of astigmatism to the light passing through these two toric lenses. Therefore, by canceling the astigmatism generated in the position detection optical system by the astigmatism generated in the two toric lenses, for example,
It is possible to accurately detect the two-dimensional position of the image of the measurement mark (WM).

Similarly, also in the second position detecting device of the present invention, a correction optical system for correcting astigmatism having the first and second optical members is provided, and the first and second optical members are provided. For, two toric lenses (8, 9) are used. Further, in the present invention, the measurement mark (WM) is provided on the reference mark plate (10) on which the reference mark (IM) is formed.
This is a method of forming an image of the measurement mark (WM). Therefore, if astigmatism occurs in the position detection optical system, if no correction is made, the two-dimensional position of the image of the measurement mark (WM) is determined. It cannot be detected accurately. Therefore, in the present invention, the astigmatism generated in the position detection optical system is adjusted by the drive means (50) to adjust the relative rotation angle or the distance between the two toric lenses. By canceling with, the two-dimensional position of the image of the measurement mark (WM) can be accurately detected.

Also, in the third position detecting device of the present invention, a correction optical system for correcting astigmatism having the first and second optical members is provided, and the first and second optical members are used as the correction optical system. Uses two toric lenses (8, 9). Further, in the present invention, the light for position detection from the measurement mark (WM) on the photosensitive substrate (W) is projected by the projection optical system (P).
However, the projection optical system (PL) has various aberrations corrected for the exposure light. Therefore, especially when the wavelength of the light for position detection is different from the exposure wavelength, astigmatism may occur in the projection optical system (PL) with respect to the light for position detection. Therefore, in the present invention, those 2
By adjusting the absolute rotation angle, the relative rotation angle, or the interval of the two toric lenses and canceling the astigmatism generated in the projection optical system (PL) by the astigmatism generated in these two toric lenses, the measurement mark ( It is possible to accurately detect the two-dimensional position of the image of WM), and thus to accurately detect the position of the photosensitive substrate (W).

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the position detecting device according to the present invention will be described below with reference to FIGS. In this example,
The present invention is applied to an off-axis FIA type alignment system provided in a projection exposure apparatus. Figure 1
1 shows the main part of the projection exposure apparatus of the present embodiment. In FIG. 1, the pattern of the reticle R is illuminated with uniform illuminance by the exposure light from the illumination optical system (not shown), and the image of the pattern of the reticle R is formed. Through the projection optical system PL, each shot area on the wafer W is exposed by reducing or enlarging it with the same magnification or a predetermined magnification. Positioning reticle marks RM are formed near the pattern area of the reticle R, and corresponding positioning wafer marks WM are formed near the shot areas on the wafer W, respectively. The wafer W is placed on the wafer stage 1,
The wafer stage 1 includes an XY stage for positioning the wafer W on a two-dimensional plane perpendicular to the optical axis AX1 of the projection optical system PL (the orthogonal coordinate axes are the X axis and the Y axis) and a Z axis parallel to the optical axis AX1. Z for positioning the wafer W in the direction
It is composed of stages and the like.

An objective lens 2 for a reticle alignment system for detecting the position of the reticle mark RM is arranged on the reticle R, and a mirror 3 for bending an optical path is arranged between the objective lens 2 and the reticle R. There is. The optical axis AX2 of the reticle alignment system extends to the wafer W side through the projection optical system PL. In the reticle alignment system, for example, the reticle mark RM and the index mark (not shown) on the wafer stage 1 via the objective lens 2. It is possible to detect the amount of positional deviation between and.

An off-axis FIA alignment system 4 is arranged on the side surface of the projection optical system PL, and in this alignment system 4, the position detection illumination light (alignment light) emitted from the light source 5 is detected. The light transmitted through the beam splitter 6 is irradiated onto the wafer mark WM on the wafer W via the objective lens 7. Then, the alignment light reflected by the wafer mark WM returns to the beam splitter 6 via the objective lens 7, and the alignment light reflected by the beam splitter 6 passes through the negative cylindrical lens 8 and the positive cylindrical lens 9 and then the focusing screen. An image of the wafer mark WM is formed on the wafer 10.

An index mark IM is formed on the focusing screen 10. The alignment light transmitted through the focusing screen 10 reaches the half prism 12 through the relay lens 11, and the light transmitted through the half prism 12 is two-dimensional. Images of the wafer mark WM and the index mark IM are formed on the image pickup surface of the first image pickup device 13M formed of a CCD. Also, half prism 1
The light reflected by 2 is reflected by the wafer mark WM and the index mark I on the image pickup surface of the second image pickup device 13S including a two-dimensional CCD.
Form an image of M. Optical axis AX3 of this alignment system 4
If the intersection with the wafer W is shifted in the X direction with respect to the optical axis AX1 of the projection optical system PL, the projection optical system P
The meridional direction of L is the X direction, and the projection optical system PL
The sagittal direction of is the Y direction.

In the first image pickup device 13M of this example, the direction of the horizontal scanning line is set in the image pickup plane in a direction conjugate with the meridional direction, and the image of the wafer mark WM is obtained from the image pickup signal of the first image pickup device 13M. The amount of positional deviation between the index mark IM and the meridional direction (X direction in this example) can be detected. On the other hand, in the second image pickup device 13S, the direction of the horizontal scanning line is set to the direction conjugate with the sagittal direction on the image pickup surface, and the image of the wafer mark WM and the index mark IM are obtained from the image pickup signal of the second image pickup device 13S. The amount of positional deviation in the sagittal direction (Y direction in this example) can be detected.

In this example, by processing the image pickup signals of the first image pickup device 13M and the second image pickup device 13S, the two-dimensional image of the image of the wafer mark WM on the wafer W on the focusing screen 10 and the index mark IM is processed. It is possible to obtain a large amount of positional deviation. Therefore, a baseline amount, which is the distance between the optical axis AX3 of the alignment system and the optical axis AX1 of the projection optical system PL shown in FIG. 1, is obtained in advance, and, for example, the wafer stage 1 is driven to obtain an image of the wafer mark WM. After the amount of positional deviation from the index mark IM is brought into a predetermined range, the wafer stage 1 is moved by the amount of the base line so that the shot area to which the wafer mark WM belongs is exposed in the exposure field of the projection optical system PL. Can be set to.

However, at this time, if astigmatism is generated with respect to the alignment light by the objective lens 7 and the beam splitter 6 for routing the optical path, the image of the wafer mark WM formed on the focusing screen 10 is meridional direction. Defocusing occurs in the sagittal direction. Therefore, if the focus position of the image of the wafer mark WM in the meridional direction is aligned with the focus plate 10, the focus position of the image of the wafer mark WM in the sagittal direction will deviate from the focus plate 10 and the image of the wafer mark WM The index mark IM cannot be simultaneously focused in the meridional direction and the sagittal direction. Therefore, the first image sensor 13M or the second image sensor 1
In either or both of 3S, the amount of positional deviation between the image of the wafer mark WM and the index mark IM cannot be accurately detected.

Therefore, in the present embodiment, the relative rotation angle between the negative cylindrical lens 8 and the positive cylindrical lens 9 forming the correction optical system for correcting astigmatism or the distance between these two cylindrical lenses is changed. As a result, the astigmatism generated by the two cylindrical lenses cancels the astigmatism generated by the objective lens 7 or the beam splitter 6. As a result, the amount of positional deviation between the image of the wafer mark WM and the index mark IM in the meridional direction and the sagittal direction is respectively calculated by the first image sensor 13.
It can be accurately obtained from M and the image pickup signal of the second image pickup device 13S.

Further, in the present embodiment, a setting device 50 is provided for setting the relative rotation angle and the interval of these two cylindrical lenses to desired states.
In this example, the focusing screen 10 and the image pickup devices 13M, 1
3S, that is, when astigmatism occurs in the relay lens 11, for example, the optical axes AX of the image pickup devices 13M and 13S.
Focusing can be performed by adjusting the positions in the three directions. Therefore, the focusing screen 10 and the image pickup device 13M,
When astigmatism occurs only between the lens and 13S, it is not necessary to install the cylindrical lenses 8 and 9.

Next, with reference to FIGS. 2 and 3, it will be quantitatively described how the astigmatism changes depending on the relative rotation angle of the cylindrical lenses 8 and 9 of FIG. 1 or the interval between them. Here, the focal length of the negative cylindrical lens 8 is −f _C , the focal length of the positive cylindrical lens 9 is f _C , and the two cylindrical lenses 8 and 9 are treated as a thin lens system.

A. Change in Astigmatism When Rotated First, as shown in FIG. 2A, the amount of astigmatism when the negative cylindrical lens 8 is rotated by an angle θ around the optical axis AX3 is obtained. When the angle θ is 0 and the refracting powers of the cylindrical lenses 8 and 9 are both 0, that is, when the generatrix direction of the first cylindrical lens 8 and the generatrix direction of the second cylindrical lens 9 coincide with each other, the fixed first The meridional direction of the second cylindrical lens 9 is the meridional direction (M direction), and the direction perpendicular to this M direction is the sagittal direction (S direction). As shown in FIG. 2B, the distance from the principal point of the cylindrical lenses 8 and 9 to the object point is a, and the distances from the principal point to the image points in the meridional direction and the sagittal direction are b _M and b, respectively. _S.

In this case, when the synthetic focal length of the two cylindrical lenses 8 and 9 in the meridional direction is F _M , the following two formulas are obtained from the imaging formula of the thin lens in the meridional direction.

[0029]

[Equation 1]

[0030]

[Equation 2]

Similarly, two cylindrical lenses 8,
Assuming that the composite focal length of 9 in the sagittal direction is F _S , the following two equations can be obtained from the imaging formula of the thin lens in the sagittal direction.

[0032]

[Equation 3]

[0033]

[Equation 4]

When the incident light flux is a parallel light flux, the outgoing light flux in the meridional direction or the sagittal direction diverges. Therefore, in the following, a parallel system of the incident light flux and the incident light flux are converging light fluxes. The image system will be described separately.

A-1. In case of parallel system FIG. 2C shows an optical path diagram of a parallel system. As shown in FIG. 2C, in the parallel system, two cylindrical lenses 8 and 9 are provided with a convex lens 14 having a focal length f. Then, the image forming position by the convex lens 14 is considered. Then, in the meridional direction, the imaging relationship as shown by the solid line in FIG. 2C is established, and by substituting (a = ∞) into (Equation 2), the following equation is obtained.

[0036]

[Equation 5]

Further, in the sagittal direction, the imaging relationship as shown by the chain double-dashed line in FIG. 2C is established, and by substituting (a = ∞) into (Equation 3) and (Equation 4), The following equation is obtained.

[0038]

[Equation 6]

The distance between the principal points of the cylindrical lenses 8 and 9 and the principal point of the convex lens 14 (imaging lens) is x ₁ and the images in the meridional and sagittal directions formed by the convex lens 14 and the convex lens 14 are formed. _Assuming that the distance from the principal point is C _M and C _S , respectively, the convex lens 1 in the meridional direction can be obtained from the relationship shown by the solid line in FIG.
From the imaging formula for 4 the following equation is obtained.

[0040]

[Equation 7]

Similarly, from the relationship shown by the chain double-dashed line in FIG. 2C, the following equation can be obtained from the image formation formula for the convex lens 14 in the sagittal direction.

[0042]

[Equation 8]

Therefore, the astigmatic difference δ _RP which is the difference between the image forming position in the meridional direction and the image forming position in the sagittal direction by the cylindrical lenses 8 and 9 and the convex lens 14 is as follows. This astigmatic difference δ _RP quantitatively shows astigmatism in the parallel system of FIG.

[0044]

[Equation 9]

Here, the structure when the above relationship (Equation 9) is established will be described with reference to the embodiment of FIG. In the embodiment shown in FIG. 1, an imaging lens 14 as shown in FIG. 2C is arranged between the two cylindrical lenses 8 and 9 and the focusing screen 10 to align the alignment light reflected from the wafer mark WM with the objective lens 7. Is converted into a substantially parallel light beam and guided to the two cylindrical lenses 8 and 9, and the parallel light beam is condensed through these two cylindrical lenses 8 and 9 to form an image of the wafer mark WM on the focusing screen 10. The above relationship (Equation 9) is established when the configuration is adopted. At this time, the two cylindrical lenses 8 and 9 arranged between the objective lens 7 and the imaging lens 14 are arranged such that the negative cylindrical lens 8 and the positive cylindrical lens 9 are arranged in order from the objective lens 7 side. However, conversely, a positive cylindrical lens 9 and a negative cylindrical lens 8 are arranged in this order from the objective lens 7 side, and when the both cylindrical lenses are relatively rotated, ) Is established.

A-2. In the case of the imaging system In the case of the imaging system, in FIG. 2B, the difference between the distance b _M to the imaging position in the meridional direction and the distance b _S to the imaging position in the sagittal direction is astigmatic. It becomes a gap. That is, the distance b _M is as follows from (Equation 1) and (Equation 2).

[0047]

[Equation 10]

Further, from (Equation 3) and (Equation 4), the distance b _S
Is as follows.

[0049]

[Equation 11]

Therefore, the astigmatic difference δ _RC , which is the difference between the image forming position in the meridional direction and the image forming position in the sagittal direction by the cylindrical lenses 8 and 9, is as follows.

[0051]

[Equation 12]

Here, the above (Equation 12) will be explained in correspondence with the embodiment of FIG. 1. In the convergent light beam condensed by the objective lens 7, the negative cylindrical lens is arranged in order from the objective lens 7 side. 8, the result obtained in the case where the positive cylindrical lens 9 is arranged, conversely, the positive cylindrical lens 9 and the negative cylindrical lens 8 are arranged in order from the objective lens 7 side, and both cylindrical lenses are arranged. The above (Equation 1
The relationship of 2) is established.

B. Change in Astigmatism When Changing Interval As shown in FIG. 3A, a positive (focal length f _C ) cylindrical lens 9 and a negative (focal length −f _C ) cylindrical lens about the optical axis AX3 as an axis. The astigmatism amount when the distance from 8 is set to d is obtained. A direction in which the refractive powers of the cylindrical lenses 9 and 8 are both 0, that is, when the generatrix direction of the first cylindrical lens 8 and the generatrix direction of the second cylindrical lens 9 coincide with each other, Let the meridional direction be the meridional direction (M direction), and let the direction perpendicular to this M direction be the sagittal direction (S direction). Therefore, the imaging position in the meridional direction is not affected by the cylindrical lenses 9 and 8 at all.

When the incident light flux is a parallel light flux, the light flux exiting in the meridional direction does not converge. Therefore, in the following, the incident light flux is divided into a parallel system of parallel light flux and an imaging system in which the incident light flux is a convergent light flux. Explain.

B-1. In case of parallel system FIG. 3B shows an optical path diagram of a parallel system. As shown in FIG. 3B, in the parallel system, two cylindrical lenses 9 and 8 are followed by a convex lens 14 (conjunction of focal length f). Image lens)
Are arranged and the image forming position by the convex lens 14 is considered. Then, the light beam incident on the cylindrical 9 has an optical axis A
Assuming that the parallel light flux is parallel to X3, the image forming position in the meridional direction by the cylindrical lenses 9 and 8 and the convex lens 14 is the convex lens 1 as shown by the chain double-dashed line in FIG.
4 is a distance f. Further, as shown by the solid line in FIG. 3B, regarding the image formation in the sagittal direction by the positive cylindrical lens 9, if the distance from the principal point of the cylindrical lens 9 to the image point is b _A , the following relationship is established. To do.

[0056]

[Equation 13]

Further, since the spacing between the cylindrical lenses 9 and 8 is d, as shown by the solid line in FIG. 3B, with respect to the image formation in the sagittal direction regarding the negative cylindrical lens 8, from the principal point of the cylindrical lens 8. Given that the distance to the image point is c _A , the following relationship holds from the imaging formula.

[0058]

[Equation 14]

Solving this equation for the distance c _A gives the following.

[0060]

[Equation 15]

As shown by the solid line in FIG. 3B, the distance from the principal point of the convex lens 14 to the object point is x in the sagittal image formation with respect to the convex lens 14 (imaging lens).
Letting _{S be} the distance from the principal point to the image point be y _S , the following relation holds from the imaging formula.

[0062]

[Equation 16]

If the distance from the positive cylindrical lens 9 to the convex lens 14 is x ₁ , then the following relationship holds.

[0064]

[Equation 17]

Substituting the (Equation 17) into the (Equation 16) and solving for the distance y _S is as follows.

[0066]

[Equation 18]

Therefore, the astigmatic difference δ _GP , which is the difference between the image forming position in the meridional direction and the image forming position in the sagittal direction by the cylindrical lenses 9 and 8 and the convex lens 14, is as follows.

[0068]

[Formula 19]

Here, the structure when the relationship of the above (Formula 19) is established will be explained in correspondence with the embodiment of FIG. In the embodiment shown in FIG. 1, an imaging lens 14 as shown in FIG. 3B is arranged between the two cylindrical lenses 8 and 9 and the focusing screen 10 to align the alignment light reflected from the wafer mark WM with the objective lens 7. Is converted into a substantially parallel light beam and guided to the two cylindrical lenses 8 and 9, and the parallel light beam is condensed through these two cylindrical lenses 8 and 9 to form an image of the wafer mark WM on the focusing screen 10. The above relationship (Equation 19) is established when the configuration is adopted. At this time, the two cylindrical lenses 8 and 9 arranged between the objective lens 7 and the imaging lens 14 are, in order from the objective lens 7 side, a positive cylindrical lens 9 and a negative cylindrical lens 8.
However, on the contrary, the objective lens 7
When the negative cylindrical lens 8 and the positive cylindrical lens 9 are arranged in this order from the side, and the cylindrical lenses of both are relatively rotated, the following relationship (Equation 20) is established.

[0070]

[Equation 20]

B-2. Case of Imaging System FIG. 3C shows an imaging system. In FIG. 3C,
When the distance between the principal point of the cylindrical lens 9 and the object point is a _A , this distance a _A is the distance from the principal point of the cylindrical lens 9 to the image formation position of the cylindrical lenses 9 and 8 in the meridional direction.

Then, as shown by the solid line in FIG. 3C, regarding the image formation in the sagittal direction by the positive cylindrical lens 9, if the distance from the principal point of the cylindrical lens 9 to the image point is b _A , then the following relation Is established.

[0073]

[Equation 21]

Since the distance between the cylindrical lenses 9 and 8 is d, the image forming in the sagittal direction with respect to the negative cylindrical lens 8 is from the principal point of the cylindrical lens 8 from the relationship shown by the solid line in FIG. Given that the distance to the image point is c _A , the following relationship holds from the imaging formula.

[0075]

[Equation 22]

When the distance b _A is deleted from (Equation 20) and (Equation 21), the distance c _A becomes as follows.

[0077]

[Equation 23]

Therefore, the astigmatic difference δ _GC , which is the difference between the image forming position in the meridional direction and the image forming position in the sagittal direction by the cylindrical lenses 9 and 8, is as follows.

[0079]

[Equation 24]

Here, the above (Formula 24) will be described in correspondence with the embodiment of FIG. 1. In the convergent light beam condensed by the objective lens 7, the positive cylindrical lens is sequentially arranged from the objective lens 7 side. 9, the results obtained for the case where the negative cylindrical lens 8 is arranged, conversely, the negative cylindrical lens 8 and the positive cylindrical lens 9 are arranged sequentially from the objective lens 7 side, and both cylindrical lenses are arranged. When rotating relatively, the following (Equation 2
The relationship of 5) is established.

[0081]

[Equation 25]

As described above, in this example, the desired astigmatism can be given to the alignment light by changing the relative rotation angle or the interval between the two cylindrical lenses 8 and 9 as toric lenses. . Next, in the embodiment of FIG. 1, the cylindrical lens 8,
An example of the operation when correcting the astigmatism generated in the objective lens 7 and the beam splitter 6 by 9 will be described. First, as shown in FIG. 4A, an index mark IM including a pair of L-shaped marks is formed on the focusing screen 10 of FIG. Among the marks WM, the mark for position detection in the meridional direction is a mark WM1 having a line-and-space pattern arranged at a predetermined pitch in the meridional direction, as shown in FIG. 4B. In this case,
As shown in FIG. 4C, the index mark image IM 'and the mark image WM1' are superimposed and formed on the screen 13Ma of the monitor receiver connected to the first image pickup device 13M.

FIGS. 5A to 5C show image pickup signals obtained when the image of FIG. 4C is scanned along a certain horizontal scanning line LX. Further, FIGS. 5A to 5C are imaging signals obtained when the height (position in the Z direction) of the exposure surface of the wafer W is changed via the wafer stage 1 in FIG. Signals 51 and 52 are signals respectively corresponding to the index mark image IM ', and the image pickup signals 53A to 53A.
53C are signals respectively corresponding to the mark image WM1 '. As can be seen from FIGS. 5A to 5C, when the height of the exposure surface of the wafer W is changed, the contrast between the peak and the bottom of the index mark image IM ′ is always constant, but the mark image WM1 ′ has a constant contrast. The contrast between the peak and bottom gradually changes. Then, as shown in FIG. 5B, when the contrast of the image pickup signal 53B is the best, the wafer mark WM of the wafer W is in the meridional direction and the focus plate 10 is in the meridional direction.
It is thought that it is time to focus.

Therefore, in FIG. 1, the wafer stage 1
Are scanned in the Z direction, and the wafer mark WM is in the meridional direction according to the image pickup signal of the first image pickup device 13M.
Height Z of the wafer stage 1 in the Z direction when focused on
_Ask for _M. Similarly, in FIG. 1, the wafer stage 1
Is scanned in the Z direction, and the height Z _S of the wafer stage 1 in the Z direction when the wafer mark WM is focused on the focusing screen 10 in the sagittal direction is obtained from the image pickup signal of the second image pickup device 13S. In order to detect the focus in the sagittal direction, for example, as shown in FIG. 6, a mark WM2 having a line-and-space pattern formed at a predetermined pitch in the sagittal direction in the wafer mark WM is used. As a result, the difference between the height Z _M when focusing in the meridional direction and the height Z _S when focusing in the sagittal direction represents the amount of astigmatism. Therefore, by adjusting the relative rotation angle or the spacing of the cylindrical lenses 8 and 9 by the setting device 50 of FIG. 1 to make the height Z _M and the height Z _S coincide with each other, the objective lens 7 and the beam splitter 6
The astigmatism due to is completely corrected.

Next, a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, the present invention is applied to a TTL (through the lens) type alignment system. FIG. 7 shows the main part of the projection exposure apparatus of this example.
At, the pattern of the reticle R is exposed on the wafer W via the projection optical system PL by exposure light from an illumination optical system (not shown). Further, a wafer mark WM is formed near each shot area on the wafer W. Above the side surface of the projection optical system PL of this example, a TTL alignment system 15 is arranged, and in this alignment system 15, the alignment light emitted from the light source 16 is the light of the first relay lens 17 and the light of a predetermined wavelength. The light enters the beam splitter 20 through the filter plate 18 and the second relay lens 19 for selecting. Beam splitter 2
The alignment light transmitted through 1 is incident on the projection optical system PL via the objective lens 21 and the mirror 22 for bending the optical path, and the alignment light emitted from the projection optical system PL is irradiated on the wafer mark WM. The wavelength of the alignment light in this example is different from the wavelength of the exposure light so that the photosensitive material on the wafer W is not exposed.

The alignment light reflected from the wafer mark WM passes through the projection optical system PL and the bending mirror 22 and forms an image of the wafer mark WM on the conjugate plane R ′ with the exposure surface of the wafer W. The conjugate surface R ′ is separated from the exposure surface of the wafer W by the distance ΔL under the exposure light. This interval ΔL is an amount due to chromatic aberration in the projection optical system PL with respect to the exposure light and the alignment light.
The alignment light from the conjugate plane R ′ is the objective lens 2
1, the beam returns to the beam splitter 20, and the alignment light reflected by the beam splitter 20 has a prism 23 for correcting chromatic aberration of magnification, a positive cylindrical lens 9,
An image of the wafer mark WM is formed on the image pickup surface of the two-dimensional image pickup device 25 including a two-dimensional CCD through the negative cylindrical lens 8 and the image forming lens 24.

From the two-dimensional position of the image of the wafer mark WM on the image pickup surface of the two-dimensional image pickup device 25, the amount of displacement of the wafer mark WM from the predetermined reference position can be detected. In the first and second elliptical zone plates 8 and 9 in this example, the alignment light that reflects the wafer mark WM causes the projection optical system PL, the mirror 22 and the objective lens 2 to be aligned.
Objective lens 21 which becomes a substantially parallel light beam condensed via 1
And the imaging lens 24, the first elliptical zone plate 8 is formed so as to satisfy the above (Equation 9).
And the second elliptical zone plate 9 are relatively rotated, or the distance between the first elliptical zone plate 8 and the second elliptical zone plate 9 is relatively changed so as to satisfy the above (Equation 19). Preferably. . As a result, astigmatism generated in the alignment system 15 can be corrected.

In particular, in this example, since the alignment is performed by the light of the wavelength different from the exposure light by the TTL method, astigmatism is mainly generated in the projection optical system PL, but two elliptical zone plates are used. By adjusting the relative rotation angle or the interval of 8 and 9, the astigmatism can be made zero as a whole. Moreover, even when the astigmatism with respect to the alignment light is generated not only by the projection optical system PL but also by the bending mirror 22, the objective lens 21, the beam splitter 20, the imaging lens 24, etc., the two elliptical zone plates 8 are used. , 9 to adjust the relative rotation angle or the interval, the astigmatism can be made zero as a whole. Thereby, the two-dimensional position of the wafer mark WM can be accurately detected.

The folding mirror 2 is used during normal exposure.
Since 2 is an obstacle, it is desirable to retract the bending mirror 22 during exposure in order to widen the exposure field of the projection optical system PL. However, when the folding mirror 22 is retracted, the position of the wafer mark WM is detected again, so that the folding mirror 22 is moved to the reticle R.
The positional reproducibility when setting between the projection optical system PL and the projection optical system PL becomes a problem. That is, depending on the position of the folding mirror 22,
This is because the amount of astigmatism generated with respect to the alignment light is different and accurate position detection of the wafer mark WM cannot be performed.

Therefore, a sensor for measuring the set position of the bending mirror 22 is provided, and the bending mirror 2 is previously set.
When the amount of astigmatism is measured at the setting position of 2, and then the bending mirror 22 is set, the bending is changed by changing the relative rotation angle or the interval of the cylindrical lenses 9 and 8 according to the position. The amount of change in astigmatism due to the position of the mirror 22 may be corrected. Further, since the amount of astigmatism also changes depending on the room temperature or the atmospheric pressure around the projection optical system PL, the amount of change in the astigmatism due to the room temperature and the atmospheric pressure is measured in advance, and when the projection exposure apparatus is used,
The amount of astigmatism generated by the cylindrical lenses 9 and 8 may be adjusted according to the measurement results of the temperature sensor and the atmospheric pressure sensor.

Next, a third embodiment of the present invention will be described with reference to FIG. In this example, the present invention is applied to a TTR (through the reticle) type alignment system. FIG. 8 shows the main part of the projection exposure apparatus of this example.
At, the pattern of the reticle R is exposed on the wafer W via the projection optical system PL by exposure light from an illumination optical system (not shown). Further, a wafer mark WM is formed near each shot area on the wafer W. A TTR type alignment system 26 is arranged above the reticle R of this example, and in the alignment system 26, the alignment light emitted from the light source 16 is a filter that selects the first relay lens 17 and light of a predetermined wavelength. The light enters the beam splitter 27 through the plate 18 and the second relay lens 19. The alignment light reflected by the beam splitter 27 is reflected by the objective lens 28 and the reticle R.
After passing through the projection optical system PL, the alignment light emitted from the projection optical system PL is irradiated onto the wafer mark WM. The wavelength of the alignment light in this example is different from the wavelength of the exposure light so that the photosensitive material on the wafer W is not exposed.

A reticle mark RM for position detection is formed on the reticle R, and the alignment light emitted from the objective lens 28 is also applied to the reticle mark RM. The reflected light from the reticle mark RM returns to the objective lens 18 as it is. On the other hand, the alignment light reflected from the wafer mark WM is generated by the projection optical system PL and the reticle R.
After that, an image of the wafer mark WM is formed on the conjugate surface R ′ of the exposure surface of the wafer W. The conjugate surface R ′ is separated from the pattern forming surface of the reticle R by a distance ΔL. This interval ΔL is an amount due to chromatic aberration in the projection optical system PL with respect to the exposure light and the alignment light. Therefore, with the common optical system, the image of the wafer mark WM and the image of the reticle mark RM cannot be observed at the same time.

That is, the alignment light from the wafer mark WM and the alignment light from the reticle mark RM are
It returns to the beam splitter 27 via the objective lens 28.
Of the alignment light transmitted through the beam splitter 27, the light reflected by the beam splitter 29 and the mirror 30 is the parallel plate glass 31 and the imaging lens 32.
And the beam splitter 34 via the mirror 33.
The light reflected by the beam splitter 34 forms an image of the reticle mark RM on the image pickup surface of the two-dimensional image pickup device 35 including a two-dimensional CCD.

On the other hand, the alignment light, which has passed through the beam splitter 27 and then through the beam splitter 29, passes through the parallel plate glass 54, the positive cylindrical lens 9, the negative cylindrical lens 8 and the imaging lens 36, and then to the beam splitter 34. The light that has reached and has passed through the beam splitter 34 forms an image of the wafer mark WM on the image pickup surface of the two-dimensional image pickup device 35. At this time, the light from the wafer mark WM is mixed in the light flux from the imaging lens 32, but the image of the wafer mark WM is defocused on the image pickup surface of the two-dimensional image pickup device 35. Similarly, the reticle mark R is included in the light beam from the imaging lens 36.
Although the light from M is mixed, the image of the reticle mark RM is defocused on the image pickup surface of the two-dimensional image pickup device 35. Therefore, on the image pickup surface of the two-dimensional image pickup device 35,
The image of the reticle mark RM and the image of the wafer mark WM are superposed and clearly imaged. The image pickup signal of the two-dimensional image pickup device 35 is supplied to the signal processing device 41, and the position information of the wafer mark WM and the reticle mark RM obtained by the signal processing device 41 is supplied to the main control system 38 for controlling the operation of the entire device. Has been done.

In the signal processing device 41, the shot of the reticle R and the wafer W is determined from the two-dimensional positional deviation between the image of the wafer mark WM and the image of the reticle mark RM on the image pickup surface of the two-dimensional image pickup device 35. The amount of positional deviation from the area is detected. The first and second elliptical zone plates 8 and 9 in the present example serve as an objective lens 28 in which alignment light that reflects the wafer mark WM is condensed through the projection optical system PL and the objective lens 28 to become a substantially parallel light beam. Since it is arranged between the imaging lens 36 and the imaging lens 36, the first elliptical zone plate 8 and the second elliptical zone plate 9 are relatively rotated so as to satisfy the above (Equation 9), or (Equation 1
It is preferable to relatively change the distance between the first elliptical zone plate 8 and the second elliptical zone plate 9 so as to satisfy 9). As a result, astigmatism generated in the alignment system 15 can be corrected.

In particular, in this example, since the TTR method is used to perform alignment with light having a wavelength different from that of the exposure light, astigmatism mainly occurs in the projection optical system PL, but two elliptical zone plates are used. By adjusting the relative rotation angle or the interval of 8 and 9, the astigmatism can be made zero as a whole. Moreover, when the astigmatism with respect to the alignment light is generated not only by the projection optical system PL but also by the objective lens 28, the beam splitters 27 and 29, the imaging lens 36, the beam splitter 34, etc., two elliptical zones are used. By adjusting the relative rotation angle or the spacing of the plates 8 and 9,
Astigmatism can be set to 0 as a whole.

As a result, it is possible to accurately detect the two-dimensional displacement amount of the wafer mark WM with respect to the reticle mark RM. In this example, a driving device 37 for adjusting the relative rotation angle or the interval between the two cylindrical lenses 9 and 8 is provided, and the driving device 37 is based on a command from a main control system 38 that controls the operation of the entire device. Operate. By the way, when the reticle size is changed or the position of the alignment mark is changed, the alignment system 26 is moved in a direction orthogonal to the optical axis Ax1 of the projection optical system PL,
Alignment must be done. However,
There is a problem that the amount of astigmatism generated in the projection optical system PL changes each time the position of the alignment mark (reticle mark RM, wafer mark WM) with respect to the optical axis Ax1 of the projection optical system PL changes.

Therefore, in this example, the alignment system driving device 50 is provided so that the alignment system 26 can move in the direction orthogonal to the optical axis Ax1 of the projection optical system PL (direction parallel to the reticle R). Device 50
Are controlled by the main control system 38. Then, an astigmatism amount according to the position of the alignment mark (reticle mark RM, wafer mark WM) with respect to the optical axis Ax1 of the projection optical system PL is stored in the memory section inside the main control system 38.
In other words, information on the amount of astigmatism according to the image height with respect to the optical axis Ax1 of the projection optical system PL is stored in advance.

Here, when the reticle size is changed or the position of the alignment mark is changed,
The main control system 38 moves the alignment system 26 in a direction orthogonal to the optical axis Ax1 of the projection optical system PL by the alignment system driving device 50 to set it at a predetermined position, and then aligns the alignment system 26 with respect to the optical axis Ax1 of the projection optical system PL. System 26
The astigmatism amount corresponding to the position of the optical axis is calculated based on the information in the memory section. Then, the main control system 38 drives the drive device 37 based on the obtained astigmatism amount, and adjusts the relative rotation angle or the interval between the two elliptical zone plates 8 and 9. The point aberration can be corrected so as to be zero as a whole.

As described above, according to this example, even if the reticle size is changed or the position of the alignment mark is changed, the astigmatism generated in the projection optical system PL can be corrected and the wafer mark WM 2 with reticle mark RM
It is possible to accurately detect the dimensional position. It should be noted that if the configuration of this example is added to the apparatus of the second example of the TTL system shown in FIG. 7, the projection optical system P is changed even when the reticle size is changed or the position of the wafer mark WM is changed.
It goes without saying that the astigmatism generated at L can be corrected.

Further, it is known that the image forming characteristics of the projection optical system PL, such as the projection magnification and the distortion, change depending on the room temperature, the atmospheric pressure, etc. around the projection optical system PL. Therefore, in order to expose the pattern image of the reticle R onto the wafer W with higher accuracy, a mechanism for correcting the image forming characteristic of the projection optical system PL is necessary. Therefore, the projection optical system PL of this example is provided with an image forming characteristic correction device 39 for adjusting the image forming characteristics such as a magnification error of the projection optical system PL within a predetermined range.
The image formation characteristic correction device 39 is, for example, a projection optical system PL.
The pressure of the gas in a predetermined lens chamber is variable in the space (lens chamber) between the plurality of lenses forming the lens, and the magnification error of the projection optical system PL is changed by changing the pressure of the gas in the lens chamber. It is possible to change the image forming characteristics such as .. within a predetermined range.

An environment sensor 40 for measuring room temperature and atmospheric pressure is connected to the main control system 38.
Corrects the image forming characteristic of the projection optical system PL via the image forming characteristic correcting device 39 according to the measurement result of the environment sensor 40. Further, it is conceivable that the amount of astigmatism in the projection optical system PL and other optical members may change due to room temperature or atmospheric pressure. Therefore, the relationship between the measurement result by the environment sensor 40 and the amount of change in astigmatism in those optical members is measured in advance, and the main control system 38 connects the projection optical system PL via the imaging characteristic correction device 39. In parallel with the correction of the image characteristics, the relative rotation angle or the interval between the two cylindrical lenses 9 and 8 is adjusted via the driving device 37. As a result, the astigmatism changed due to the environment can be offset by the amount of change in astigmatism between the two cylindrical lenses 9 and 8.

Also, during normal exposure, the alignment system 2
Since 6 is an obstacle, the alignment system 26 can be retracted during exposure. However, when the alignment system 26 is retracted, the wafer mark WM
Also, since the position of the reticle mark RM is detected, the position reproducibility when setting the alignment system 26 on the reticle R becomes a problem. That is, the amount of astigmatism generated with respect to the alignment light differs depending on the position of the alignment system 26, and accurate position detection of the wafer mark WM cannot be performed.

Therefore, a sensor for measuring the set position of the alignment system 26 is provided, and the alignment system 2 is set in advance.
When the amount of astigmatism with respect to the set position of 6 is measured, and then the alignment system 26 is set, the alignment is changed by changing the relative rotation angle or the interval of the cylindrical lenses 9 and 8 according to the position. The amount of change in astigmatism due to the position of the system 26 is corrected.

In the above embodiment, at least one of the two cylindrical lenses 8 and 9 is rotated to move the relative rotation angle or at least one of the two cylindrical lenses 8 and 9 is moved to move the relative lens. The amount of astigmatism is adjusted by changing the interval, but the state of astigmatism can be changed to some extent even if the two cylindrical lenses 8 and 9 are integrally rotated around the optical axis. it can. Therefore, the astigmatism generated in the optical system for position detection may be corrected by changing the rotation angle (hereinafter referred to as “absolute rotation angle”) of the two cylindrical lenses 8 and 9 as a unit. good. Further, the positions where the cylindrical lenses 8 and 9 are arranged are arbitrary, and in the example of FIG. 1, they may be arranged anywhere between the wafer W and the focusing screen 10.

Although the cylindrical lens is used as the toric lens in the above-described embodiment, two general toric lenses having different focal lengths in two directions orthogonal to each other are used, and these two toric lenses are used. It is obvious that the astigmatism generated in the optical system for position detection can be corrected by changing the absolute rotation angle, the relative rotation angle or the interval of the lens.

Further, not only when the image of the wafer mark WM is image-processed, but also when the light from the wafer mark WM is photoelectrically converted as a whole as in the alignment system of the laser step alignment system, the present invention can be used. By correcting the astigmatism using the toric lens as described above, the position of the wafer mark WM can be detected more accurately.

Furthermore, it goes without saying that the present invention can be applied not only to an exposure apparatus for manufacturing semiconductor elements and the like, but also to a microscope and the like. As described above, the present invention is not limited to the above-described embodiments, and various configurations can be adopted without departing from the gist of the present invention.

[0109]

According to the first, second or third position detecting device of the present invention, the position detecting optical system (for example, the objective lens, the mirror for bending the optical path, etc.) or the projection optical system is used. Astigmatism can be corrected without replacing the optical member, and there is an advantage that the two-dimensional position detection of the test object can be performed with higher accuracy. In addition, even if the working distance of the optical system for position detection changes when the substrate or the like as the object to be tested is warped or undulated due to chemical treatment,
There is also the advantage that it can be handled with a single toric lens.

When a driving device for changing the rotation angle or the position of at least one of the two toric lenses is provided like the second position detecting device, for example, due to a change in room temperature or atmospheric pressure. Even when the astigmatism of the optical system for position detection changes, the astigmatism can be easily corrected.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a main part of a projection exposure apparatus to which a first embodiment of a position detection device according to the present invention is applied.

FIG. 2A is a perspective view showing a case where the rotation angles of two cylindrical lenses are changed in the first embodiment, and FIG.
Is an optical path diagram showing an imaging system, and (c) is an optical path diagram showing a parallel system.

3A is a perspective view showing a case where the distance between two cylindrical lenses is changed in the first embodiment, FIG. 3B is an optical path diagram showing a parallel system, and FIG. 3C is an optical path diagram showing an image forming system. Is.

FIG. 4A is an enlarged view showing an index mark IM, and FIG.
Is an enlarged view showing the wafer mark for the meridional direction,
(C) is a figure which shows the image imaged by the image sensor.

FIG. 5 is a waveform diagram showing changes in the image pickup signal when the height of the exposed surface of the wafer W is gradually changed in the first embodiment.

FIG. 6 is an enlarged view showing a wafer mark for a sagittal direction in the first embodiment.

FIG. 7 is a configuration diagram showing a main part of a projection exposure apparatus to which a second embodiment of the present invention has been applied.

FIG. 8 is a configuration diagram showing a main part of a projection exposure apparatus to which a third embodiment of the present invention has been applied.

[Explanation of symbols]

 R Reticle PL Projection optical system W Wafer WM Wafer mark IM Index mark 1 Wafer stage 4 Alignment system 6 Beam splitter 7 Objective lens 8 Negative cylindrical lens 9 Positive cylindrical lens 10 Focus plate 11 Imaging lens 13M, 13S Image sensor

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Ayako Sugaya 3 2-3 Marunouchi, Chiyoda-ku, Tokyo Inside Nikon Corporation

Claims (3)

[Claims] 1. A light for position detection from a measurement mark on an object to be examined is guided to an observation surface through a position detection optical system, and the position detection light is moved from the position on the observation surface to the position. In a device for detecting the position of an object to be inspected, a first toric lens and a second toric lens are arranged along an optical path of the light for position detection between the object to be inspected and the observation surface, and the two toric lenses are arranged. At least one of the toric lenses is provided so as to be rotatable about the optical axis of the lens or movable along the optical axis, and at least one of the two toric lenses is rotated or moved. By doing so, the astigmatism generated in the position detecting optical system with respect to the light for position detection is corrected. 2. A position detection optical system that collects light for position detection from a measurement mark on an object to be measured and forms an image of the measurement mark on a reference mark plate on which a reference mark is formed. A measuring means for detecting a two-dimensional positional deviation amount between the reference mark and the measurement mark images, and the object to be inspected based on the positional deviation amount between the reference mark and the measurement mark image. In a device for detecting a position, a first toric lens and a second toric lens are arranged along an optical path of the light for position detection between the test object and the reference mark plate, and the two toric lenses are A driving means for rotating at least one of the toric lenses in the optical axis of the lens or moving the toric lens along the optical axis, and rotating at least one of the two toric lenses; Position detecting device is characterized in that as by moving, for correction of astigmatism occurring at said position detecting optical system with respect to the light for the position detection. 3. An exposure device, which projects an image of a pattern formed on a mask onto a photosensitive substrate via a projection optical system, and is obtained from a measurement mark on the photosensitive substrate via the projection optical system. A position detection optical system that collects light for position detection, and forms an image of the measurement mark on the observation surface.
A position detecting means for detecting a two-dimensional displacement amount of the measurement mark image on the observation surface, and detecting the position of the photosensitive substrate from the displacement amount of the measurement mark image. In the device, a first toric lens and a second toric lens are arranged along an optical path of the light for position detection between the projection optical system and the observation surface, and at least one of the two toric lenses is arranged. A toric lens is provided so as to be rotatable about the optical axis of the lens or movable along the optical axis, and at least one toric lens of the two toric lenses is rotated or moved to detect the position. The position detection device is configured to correct the astigmatism generated in the projection optical system with respect to the light.