JPH06163363A - Horizontal position detecting method - Google Patents

Abstract

PURPOSE:To detect an inclination angle of a surface of a detection object accurately without being affected by reflection light from a rear of the detection object when the detection object transmits light. CONSTITUTION:A horizontal position detection system for leveling is constituted of an irradiation optical system 14 with a first light screening board 18, a conversing optical system 22 with a second light screening board 25 and a photosensitive element 28. A focus position detecting system is constituted of light source 29 to a photosensitive element 35. After a surface 1a of a glass plate 1 is lowered to a lowermost position, it is raised gradually and a detection region of the surface 1a is aligned to a best image forming surface of a projection optical system 8 by using an in-focus position detecting system. Thereafter, an inclination angle of the surface 1a is detected by a horizontal position detecting system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal position detecting method suitable for leveling a photosensitive substrate in a projection exposure apparatus having a photosensitive substrate leveling mechanism and an autofocus mechanism.

[0002]

2. Description of the Related Art When a semiconductor device, a liquid crystal display device, or the like is manufactured by using a photolithography technique, a pattern image of a photomask or a reticle (hereinafter referred to as a "reticle") is exposed through a projection optical system. A projection exposure apparatus that exposes light onto a substrate is used. In such a projection exposure apparatus, since the pattern to be exposed is extremely fine, the numerical aperture (NA) of the projection optical system is large and the allowable depth of focus is very small. Therefore, in order to expose the reticle pattern image on the exposure surface of the photosensitive substrate with high resolution, a mechanism for aligning the exposure surface with the best image formation surface of the projection optical system within the allowable depth of focus is provided. is necessary.

The mechanism for aligning the exposure surface of the photosensitive substrate with the best image plane within the range of the allowable depth of focus is a leveling mechanism for setting the exposure plane parallel to the best image plane and the exposure thereof. It is composed of an auto-focus mechanism for adjusting the height of a predetermined measurement point on the surface in the optical axis direction of the projection optical system to the best image forming surface. The horizontal position detection system of the leveling mechanism generally irradiates the photosensitive substrate with a substantially parallel light beam and detects the inclination of the photosensitive substrate from the direction of the reflected light beam. On the other hand, the focus position detection system of the autofocus mechanism generally projects an image of, for example, a slit-shaped or cross-shaped pattern on a photosensitive substrate obliquely, and re-images the reflected light from the position of the photosensitive substrate. The height is detected.

In this case, for example, when manufacturing a liquid crystal display device or the like, a light-transmissive glass plate coated with a photosensitive material is used as the photosensitive substrate, but when the photosensitive substrate is light-transmissive, Due to the back surface reflection of the photosensitive substrate, an error may occur in the detection of the tilt angle or the like. Therefore, the present applicant has previously proposed a horizontal position detection system in which a detection error is unlikely to occur even when the photosensitive substrate is light transmissive.

FIG. 4 (a) is a diagram for explaining the principle of the horizontal position detecting system proposed by the present applicant. In FIG. 4 (a), the surface 1a of the glass plate is the surface to be inspected and is not shown. The tilt angle of the surface 1a with respect to the plane perpendicular to the optical axis AX of the projection optical system is the detection target. Then, the detection light emitted from the light source 2 is converted into a substantially parallel light beam by the collimator lens 3 and illuminates the lattice-shaped first light shielding plate 4. The first light-shielding plate 4 is configured by arranging the openings 4a and the light-shielding portions 4b in a direction parallel to the paper surface of FIG. 4A at a predetermined pitch, and the width of the opening 4a in the pitch direction is the light-shielding portion 4.
It is less than the width of b in the pitch direction. The longitudinal direction of the opening 4a and the light shield 4b is a direction perpendicular to the paper surface of FIG. 4 (a).

The detection light passing through the opening 4a of the first light shielding plate 4 reaches the surface 1a obliquely with respect to the optical axis AX, and the detection light reflected by the surface 1a is emitted from the opening 5a and the light shielding portion 5b. The second light shielding plate 5 in the form of a grid is illuminated. The second light shielding plate 5 has the same configuration as the first light shielding plate 4, and the first light shielding plate 4 and the second light shielding plate 5 are arranged symmetrically with respect to the optical axis AX. The detection light passing through the opening 5a of the second light shielding plate 5 is condensed by the condensing lens 6 to a point P on the light receiving surface of the light receiving element 7.
Focused on 0. FIG. 4A shows a state in which the surface 1a matches the best image plane of the projection optical system (not shown), and in this state, all the detection light reflected by the surface 1a is the second.
The position of the second light shielding plate 5 in the R direction, which is the pitch direction, is adjusted so as to pass through the opening 5a of the light shielding plate 5.

Then, as shown in FIG. 4B, the surface 1
When a is tilted with respect to the best image plane with respect to the point P1 on the optical axis AX in the plane of FIG. 1, the detection light reflected by the surface 1a passes through the opening of the second light shielding plate 5. , Is focused by the condenser lens 6 at a point P2 on the light receiving surface of the light receiving element 7.
Since the point P2 is deviated from the point P0 in FIG.
The tilted state of the surface 1a is detected. As the light receiving element 7, a light receiving element that can detect the barycentric position of the light amount distribution of the detection light focused on the light receiving surface, for example, a four-divided light receiving element is used.

In this case, a part of the detection light reflected by the surface 1a is blocked by the light blocking portion 5b of the second light blocking plate 5 and the output signal of the photoelectric conversion element 7 becomes small, but the detection light is focused. Since the positions of the points P2 are the same, the inclination angle of the surface 1a is accurately detected. An image forming optical system is arranged between the first light shielding plate 4 and the surface 1a and between the surface 1a and the second light shielding plate 5, but for simplicity, FIG.
Then, those image forming optical systems are omitted.

Next, the principle of eliminating the influence of the back surface reflection of the glass plate will be described. FIG. 5 shows the configuration of the lower part of the surface 1a of FIG. 4 (a). In this FIG. 5, the detection light L1 is incident on the surface 1a of the glass plate 1 at an incident angle θ ₁ , and within this detection light L1 The detection light L2 reflected by the surface 1a goes toward the second light shielding plate 5 in FIG. Surface 1
4A, the areas corresponding to the openings 4a and the light shielding portions 4b of the first light shielding plate 4 in FIG. The pitch in the direction parallel to the paper surface of FIG.
Let w be the width of each bright portion 4bP in the direction parallel to the paper surface of FIG. On the other hand, in the detection light L1, the detection light L3 traveling toward the back surface 1b of the glass plate 1 at the refraction angle θ ₂ is partially reflected by the back surface 1b and returns to the front surface 1a again.

At this time, the thickness of the glass plate 1 is set to d,
When the refractive index of the glass plate 1 is n, the following equation is established according to the well-known law of refraction.

[Number 1] and sinθ ₁ = n · sinθ _2, positional deviation amount of the surface 1a of the detection light L3 reflected by the detection light L2 and the back surface 1b, which is reflected by the surface 1a, i.e. by back reflection of the glass plate 1 The deviation amount x of the detection light L3 is as follows.

[Formula ₂ ] x = 2 · d · tan θ ₂

In this case, the detection light L reflected by the back surface 1b
3 is not detected by the light receiving element 7 of FIG. 4A, the detection light L3 reflected by the back surface 1b is the front surface 1a.
It suffices if it fits within the dark portion 4bP. In this way, the detection light L3 reflected by the back surface 1b is the dark portion 4bP of the front surface 1a.
The conditions to fit in are as follows.

## EQU00003 ## x + w.ltoreq.p, w.ltoreq.x When the relationship of (Equation 3) is summarized, the following one condition is obtained.

(4) w ≦ x ≦ p−w

In this case, the maximum value of the aperture ratio, which is the ratio (w / p) of the width w of the bright portion 4aP to the pitch p, is 1/2 (w).
= P / 2), and the thickness d of the glass plate 1 for satisfying (Equation 4) when the aperture ratio is maximum is limited to a single value as follows.

D = p / (4 · tan θ ₂ ) On the other hand, when the aperture ratio is smaller than 50%, the allowable value of the thickness d becomes a value within a certain range. However, in order to secure a certain amount of light, it is desirable to set the aperture ratio between 10% and 50%. This makes it possible to widen the selection range of the thickness d of the glass plate 1 to some extent and prevent the influence of reflection on the back surface 1b of the glass plate 1.

[0013]

As described above, as shown in FIG.
In the horizontal position detection system of the system for projecting the image of the grid pattern shown in (a), the surface 1a as the surface to be inspected is aligned with the best image plane of the projection optical system, and The light fluxes that have passed through the plurality of openings 4a of the first light shielding plate 4 are adjusted so as to enter the plurality of openings 5a of the second light shielding plate 5 on the light receiving system side. When the object to be inspected is the glass plate 1, the rear surface 1b of the glass plate 1 is in a state where the front surface 1a is substantially aligned with the best image plane.
It is adjusted so that the reflected light at (5) is blocked by the light blocking portion 5b of the second light blocking plate 5.

However, in the state where the surface 1a is deviated from the best image plane by more than the allowable range, all the reflected light from the surface 1a out of the detected light which has passed through the first light shielding plate 4 is the first. It does not enter the opening 5a of the second shading plate 5. Further, since the reflected light from the back surface 1b of the glass plate 1 also enters the opening 5a of the second light shielding plate 5, an error occurs in the detection of the tilt angle (horizontal position detection) of the front surface 1a with respect to the best image plane. There are cases. Therefore, even in the actual exposure sequence, if the surface 1a is focused after the surface 1a is leveled, a leveling error is likely to occur.

In this regard, when the focus position of the front surface 1a of the glass plate 1 is detected by the current optical focus position detection system, the reflected light on the front surface 1a of the glass plate 1 and the reflected light on the rear surface 1b are detected. Are separated and reach the light receiving surface of the detection system. However, since the intensity of the reflected light on the back surface 1b is sufficient to apply the focus servo, the focus servo may be applied in a state where the back surface 1b matches the best imaging plane.

In view of the above point, the present invention uses a horizontal position detection system of a system in which an image of a grid pattern is projected on the surface of an object to be inspected, when the object is optically transparent. But
An object of the present invention is to enable accurate detection of the tilt angle of the surface of the test object without being affected by the reflected light from the back surface of the test object. Furthermore, the present invention provides a method in which an object to be inspected is used when a horizontal position detection system that projects an image of a grid pattern on the surface to be inspected of the object and an optical focus position detection system are used together. An object of the present invention is to enable accurate detection of the tilt angle of the surface of the test object without being affected by the reflected light from the back surface of the test object even in the case of light transmission.

[0017]

A horizontal position detecting method according to the present invention is a projection optical system for projecting an image of a predetermined pattern on a surface (1a) to be inspected of an object (1) as shown in FIG. A stage (1) on which the system (8) and the test object (1) are placed and the test object (1) is positioned in the optical axis direction of the projection optical system (8).
0, 11), an irradiation optical system (14) for obliquely projecting an image of a grid pattern from the outside of the optical axis of the projection optical system (8) to the detection area on the surface to be inspected (1a), and the grid shape. The condensing optical system (22) for re-imaging the image of the pattern and the image of the lattice-like pattern re-formed in this way is arranged on the image plane of the re-formed image. A light-shielding plate (25) having a pitch and a grid pattern in the same direction, and a light-receiving element (28) for photoelectrically converting light passing through the light-shielding plate (25).
And the leveling detection means (14, 22 ,,) for detecting the amount of inclination of the surface to be detected (1a) with respect to the surface perpendicular to the optical axis of the projection optical system (8) from the photoelectric conversion signal of the light receiving element (28).
28) and the focus position detecting means (29-3) for detecting the position of the surface to be inspected (1a) in the optical axis direction of the projection optical system (8).
5) is a method for detecting the inclination of the surface to be inspected (1a) by a projection optical device having

In the present invention, the focus position detecting means (29 to 35) is used to detect the position in the optical axis direction of the projection optical system (8) in the detection area of the surface to be inspected (1a) to be inspected. After the detection area of the surface (1a) is aligned with the best imaging plane of the projection optical system (8), the leveling detection means (14, 2).
2, 28) is used to detect the inclination of the surface to be inspected (1a).

In this case, when the test object (1) is a light-transmissive substrate, the surface (1a) of the substrate (1) is largely separated from the best image plane of the projection optical system (8) to the outside. Then, the detection area of the surface (1a) of the substrate (1) is aligned with the best image plane of the projection optical system (8) while gradually bringing the substrate (1) closer to the projection optical system (8). You may choose not to.

[0020]

According to the present invention, the focus position detecting means is detected before the tilt amount of the surface (1a) to be detected is detected by using the leveling detecting means (14, 22, 28) as the horizontal position detecting system. (29 to 35) is used to detect the position of the detection area of the surface to be inspected (1a) in the optical axis direction of the projection optical system (8), and the detection area of the surface to be inspected (1a) is projected to the projection optical system (8). To the best image plane of. Therefore, even when the test object (1) is light-transmissive, the reflected light from the back surface (1b) of the test object (1) is reflected by the light blocking portion of the light blocking plate (25) on the condensing optical system (22) side. Since it is almost blocked, the leveling detection means (14, 2
2, 28) accurately detects the amount of inclination of the surface (1a) to be inspected.

When the object (1) to be inspected is a light transmissive substrate, focus position detecting means (29-3).
Reflected light from the front surface (1a) and reflected light from the rear surface (1b) of the substrate (1) are incident on the light receiving surface of 5). Therefore, after setting the surface (1a) of the substrate (1) so as to be largely separated from the best imaging plane of the projection optical system (8),
When the substrate (1) is gradually brought closer to the projection optical system (8), the reflected light from the surface (1a) first enters the light receiving surface of the focus position detecting means (29 to 35). Therefore, by detecting the first peak position of the reflected light, the detection area of the surface (1a) of the substrate (1) is projected onto the projection optical system (8).
Can be accurately adjusted to the best image forming plane.

After setting the surface (1a) of the substrate (1) so as to be much closer to the inner side from the best image plane of the projection optical system (8), the substrate (1) is gradually moved to the projection optical system (8).
If you avoid the distance from the focus position detection means (29
Is incident on the light receiving surface of the substrate (1) to the back surface (1) of the substrate (1).
The reflected light is from b), and the second incident light on the light receiving surface is the reflected light from the surface (1a) of the substrate (1).
Therefore, when the substrate (1) is gradually moved away from the projection optical system (8), the detection area of the surface (1a) can be accurately aligned with the best image plane by capturing the second peak of the reflected light. Can be adjusted to. However, the method of gradually bringing the substrate (1) closer to the projection optical system (8) as in the present invention is more practical.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the position detecting method of the present invention will be described below with reference to FIGS. In this embodiment, the present invention is applied when the surface (exposure surface) of a glass plate as a photosensitive substrate is aligned with the best image plane of the projection optical system in a reduction projection type projection exposure apparatus.

FIG. 1 shows the structure of the main part of the projection exposure apparatus of this embodiment. In FIG. 1, the pattern forming surface of the reticle 9 and the surface (exposure surface) 1a of the glass plate 1 are related to the projection optical system 8. Glass plate 1 arranged in conjugation
A photoresist as a photosensitive material is applied to the surface 1a of the. An image of the pattern of the reticle 9 illuminated by exposure light from an illumination optical system (not shown) is reduced and projected on the surface of the glass plate 1 via the projection optical system 8. The glass plate 1 is held on a holding stage 10, and the holding stage 10 is placed on a photosensitive substrate stage 11. The photosensitive substrate stage 11 is an XY stage that positions the glass plate 1 in a plane perpendicular to the optical axis of the projection optical system 8, and a Z stage that positions the glass plate 1 in the Z direction parallel to the optical axis of the projection optical system 8. And a leveling stage for adjusting the inclination angle of the surface of the glass plate 1.

Then, the control unit 12 for controlling the operation of the entire apparatus is driven by the drive unit 13 to move the stage 11 for the photosensitive substrate.
Control the behavior of. When actually printing and exposing the pattern of the reticle on the glass plate 1, the glass plate 1 is sequentially moved by a predetermined amount by the step-and-repeat method so that the exposure is repeated, and the reticle 9 is formed on different patterns. The same exposure operation is repeated each time the reticle is replaced with a reticle formed with.

The horizontal position detection system of the leveling mechanism of this example is composed of an irradiation optical system 14, a condensing optical system 22 and a four-divided light receiving element 28, and the optical axis 14 of the irradiation optical system 14 is used.
a and the optical axis 22a of the condensing optical system 22 are inclined symmetrically with respect to the optical axis 8a of the projection optical system 8. First, in the irradiation optical system 14, the light source 1 such as a light emitting diode (LED)
The detection light from 5 is converted into a parallel light flux by the collimator lens 16, and the parallel light flux illuminates the lattice-shaped first light shielding plate 18 via the mirror 17. The first light-shielding plate 18 is configured by repeating a light-shielding portion and an opening portion at a predetermined pitch P1 in a direction diagonally intersecting the optical axis 14a in the plane of FIG. 1, and the ratio of the width w1 of the opening portion to the pitch P1. The aperture ratio of (w1 / P1) is, for example, 10% to 50%.

The detection light that has passed through the opening of the first light shielding plate 18 has a condenser lens 19, a minute circular aperture of the diaphragm 20, and an irradiation objective lens 2 having a front focus on the minute circular aperture.
The surface 1a of the glass plate 1 is illuminated via 1. The condenser lens 19 condenses the detection light that has passed through the first light shielding plate 18 to form an image of the light source 15 in the minute aperture of the diaphragm 20, and the divergent light flux from the minute aperture of the diaphragm 20 is The glass plate 1 is converted into a parallel light flux by the irradiation objective lens 21.
Incident on the surface of. The detection light supplied from the irradiation optical system 14 to the surface of the glass plate 1 has a wavelength different from that of the exposure light for illuminating the reticle 9 so that the photoresist on the glass plate 1 is not exposed.

Further, the arrangement surface of the first light shielding plate 18 and the surface 1a of the glass plate 1 are conjugate with respect to the image forming optical systems 19 and 21 composed of the condenser lens 19 and the irradiation objective lens 21. In this case, the surface of the glass plate 1 is the optical axis 1.
Since it is not perpendicular to 4a, the first shading plate 18 also
The first light-shielding plate 18 and the surface of the glass plate 1 which are arranged obliquely with respect to a are set in a so-called tilted arrangement based on the Scheimpflug principle. The so-called tilted arrangement based on the Scheimpflug principle means three planes of the first light-shielding plate 18 (the object plane), the surface of the glass plate 1 (the image plane), and the main planes of the imaging optical systems 19 and 21. An arrangement in which two planes intersect on a straight line. In this arrangement, the image of the grid pattern of the first light shielding plate 18 is clearly formed on the entire surface of the glass plate 1. Further, the grid-shaped pattern image of the first light shielding plate 18 is projected so as to cover the entire exposure field on the glass plate 1 that is conjugate with the pattern area of the reticle 9.

However, in such a tilted arrangement, the imaging magnification generally differs depending on the position on the surface of the glass plate 1. Therefore, in this embodiment, the imaging optical systems 19 and 21 are made telecentric on both sides and the imaging magnification is changed. Is almost constant on the surface of the glass plate 1. The imaging magnification from the first light shielding plate 18 to the surface of the glass plate 1 is β
Set to 1.

The detection light reflected by the front surface and the back surface of the glass plate 1 enters the condensing optical system 22. In the focusing optical system 22, the detection light from the glass plate 1 is focused on the rear focal plane by the focusing objective lens 23. The light flux diverging from the rear focal plane is converted into a parallel light flux by the collimator lens 24 and illuminates the lattice-shaped second light shielding plate 25. The second shading plate 25 is provided on the optical axis 22 in the plane of FIG.
The light-shielding portion and the opening are repeatedly formed at a predetermined pitch P2 in the R1 direction diagonally intersecting a, and the opening ratio, which is the ratio (w2 / P2) of the width w2 of the opening to the pitch P2, is, for example, 10% to 50%. %. In addition, the second light shielding plate 25,
It is supported so that the position can be adjusted in the R1 direction which is the pitch direction.

Further, the surface of the glass plate 1 and the surface on which the second light shield plate 25 is arranged are conjugate with respect to the image forming optical systems 23 and 24 including the condenser objective lens 23 and the collimator lens 24. In this case, since the surface of the glass plate 1 is not perpendicular to the optical axis 22a, the second light shielding plate 25 also has the optical axis 2a.
The surface of the glass plate 1 and the second light shielding plate 25 are arranged obliquely with respect to 2a, and are set in a so-called tilted arrangement based on the Scheimpflug principle. In this arrangement, the image of the grid pattern of the first light shield plate 18 formed on the surface of the glass plate 1 is clearly re-imaged on the entire surface of the second light shield plate 25.

However, in such a tilted arrangement, the image forming magnification is generally different depending on the position on the second light shielding plate 25. Therefore, in this embodiment, the image forming optical systems 23 and 24 are made telecentric on both sides to form an image. The magnification is set to be substantially constant on the second light shield plate 25. If the imaging magnification from the surface of the glass plate 1 to the second light shielding plate 25 is β2,
Since the imaging magnification of the imaging optical systems 19 and 21 is β1, the pitch P2 of the second light shielding plate 25 and the width w2 of the opening are as follows.

[Equation 6] P2 = β1 · β2 · P1, w2 = β1 · β2 · w1

The detection light that has passed through the opening of the second light shield plate 25 passes through the mirror 26 and the condenser lens 27 and is condensed on the light receiving surface of the four-divided light receiving element 28. The light receiving surface of the light receiving element 28 is divided into four, and the photoelectric conversion signals independently generated by these four light receiving portions are supplied to the control device 12. The controller 12 can determine the position of the spot of the detection light focused on the light receiving surface of the light receiving element 28 from the magnitudes of these four photoelectric conversion signals. Then, in a state where the surface of the glass plate 1 matches the best image forming surface of the projection optical system 8 in advance, the second light shielding is performed so that the sum of photoelectric conversion signals from the four light receiving surfaces of the light receiving element 28 becomes maximum. R of plate 25
Determine the position in one direction. Further, by obtaining the position of the spot on the light receiving element 28 when the surface of the glass plate 1 matches the best image plane of the projection optical system 8, the inclination angle of the surface of the glass plate 1 can be obtained. it can. A more detailed detection method is disclosed in, for example, JP-A-58-11.
It is disclosed in Japanese Patent No. 3706.

In this case, the reflected light from the back surface of the glass plate 1 may become an optical noise, but as described with reference to FIG. 5, the first light shielding plate 18 and the second light shielding plate 25. Therefore, as long as the surface 1a of the glass plate 1 is near the best image plane of the projection optical system 8, the reflected light from the back surface of the glass plate 1 does not cause a detection error of the horizontal position detection system. Therefore, how to set the surface 1a of the glass plate 1 near the best image plane of the projection optical system 8 becomes a problem, but in this example, the focus position detection system of the autofocus mechanism is used.

In the focus position detection system of FIG. 1, the first slit plate 30 is illuminated by the detection light from the light source 29. On the first slit plate 30, a slit-shaped opening pattern having a longitudinal direction perpendicular to the plane of FIG. 1 is formed. The detection light that has passed through the slit-shaped opening pattern of the first slit plate 30 has the optical axis 31a as the optical axis 8a.
Is focused on the surface 1a of the glass plate 1 via the objective lens 31 that is largely inclined with respect to the first slit plate 30 and the slit-shaped opening pattern image of the first slit plate 30 is formed at the center of the exposure field on the surface of the glass plate 1. It is projected diagonally. The longitudinal direction of the slit-shaped opening pattern image thus projected is the direction perpendicular to the paper surface of FIG.

Then, the detection light reflected from the front surface and the back surface of the glass plate 1 is focused on the second slit plate 33 by the objective lens 32 and near the slit-shaped opening pattern of the second slit plate 33. The slit-shaped aperture pattern image projected on the surface of the glass plate 1 is re-imaged. The optical axis 32a of the objective lens 32 is connected to the projection optical system 8
The optical axis 8a is inclined symmetrically with the optical axis 31a of the objective lens 31. The longitudinal direction of the slit-shaped opening pattern on the second slit plate 33 is also the direction perpendicular to the paper surface of FIG. 1, and the second slit plate 33 is vibrated by the vibrating device 34 so that R2 is perpendicular to the longitudinal direction of the opening pattern. It is supported so as to vibrate in a predetermined direction in a predetermined direction.

The detection light that has passed through the opening pattern of the second slit plate 33 is incident on the light receiving surface of the light receiving element 35. The operation of the vibration device 34 is controlled by the control device 12, and the photoelectric conversion signal of the light receiving element 35 is supplied to the control device 12.
The control device 12 obtains a focus signal by synchronously rectifying the photoelectric conversion signal of the light receiving element 35 with the drive signal of the vibration device 34. In this case, with the surface of the glass plate 1 aligned with the best image plane of the projection optical system 8, the image of the slit-shaped opening pattern of the first slit plate 30 becomes the slit of the second slit plate 33. The second slit plate 33 is positioned in the R2 direction so as to match the vibration center of the circular opening pattern.

When the surface of the glass plate 1 deviates from the best image plane of the projection optical system 8 in the Z direction, the image of the opening pattern of the first slit plate 30 on the second slit plate 33 moves in the R2 direction. The level of the focus signal obtained by laterally shifting and synchronously rectifying the photoelectric conversion signal of the light receiving element 35 changes. This makes it possible to detect the amount of positional deviation in the Z direction from the best imaging plane of the projection optical system 8 in the detection area (projection area of the slit-shaped opening pattern image) on the surface of the glass plate 1. The controller 12 adjusts the position in the Z direction of the Z stage in the photosensitive substrate stage 11 via the drive device 13 so that the focus signal becomes a predetermined level (for example, 0), so that the glass plate 1 of the glass plate 1 is adjusted. The detection area on the surface is aligned with the best image plane of the projection optics 8.

However, in the case of the glass plate 1, since there is reflection on the back surface, if the position in the Z direction (focus position) is controlled based on the focus signal obtained by simply processing the photoelectric conversion signal of the light receiving element 35. The back surface of the glass plate 1 may be aligned with the best image plane of the projection optical system 8. FIG. 2 shows the positional relationship between the glass plate 1 and the focus position detection system. In FIG. 2, the chief ray L4 of the detection light that has passed through the opening pattern of the first slit plate 30.
Is reflected by the surface 1a of the glass plate 1, and the chief ray L5 of the reflected light is directed to the second slit plate 33. The remaining portion of the principal ray L4 is refracted and goes to the back surface 1b, and the principal ray L6 reflected by the back surface 1b goes from the front surface 1a to the second slit plate 33 in parallel with the principal ray L5.

In this case, assuming that the refractive index of the glass plate 1 is n, the thickness is d, the incident angle of the principal ray L4 is θ ₃ , and the refracted principal ray L6 is θ ₄ , the second slit plate 3
Front surface 1a of back surface 1b of glass plate 1 when viewed from 3
The depth e from is as follows.

Equation 7] _{e = d · tanθ 4 · tan} (90 ° -θ 3) Here, the refraction angle theta ₄ is defined by the following equation according to the law of known refractive.

FIG. 8 n = sin θ ₃ / sin θ ₄

For example, the thickness d of the glass plate 1 is 1 m.
m, incident angle θ ₃ is 80 °, and refractive index n is 1.5,
From (Equation 8), θ ₄ = 41 °, and from (Equation 7), the apparent depth e is as follows. e = 0.15 [mm]

That is, the principal ray L5 of the reflected light on the front surface 1a of the glass plate 1 and the principal ray L6 of the reflected light on the rear surface 1b of the glass plate 1 are slit-shaped openings on the second slit plate 33. 0 in the direction perpendicular to the longitudinal direction of the pattern.
Although they are separated by about 15 mm, there is such strength that the focus servo is sufficiently applied even with the reflected light from the back surface 1b. Further, once the focus servo is applied to the surface 1a of the glass plate 1, the focus position does not largely shift, and therefore the focus servo continues to match the surface 1a. Furthermore, even if the glass plate 1 is replaced, the position of the Z stage of the photosensitive substrate stage 11 is not moved, and the thickness unevenness of the glass plate 1 is compared with the apparent depth e of the back surface 1b with respect to the front surface 1a. Then, if it is small, the focus servo is not applied to the back surface 1b. The premise of this is that the intensity of the reflected light on the front surface 1a is weaker than that of the reflected light on the rear surface 1b.

Therefore, when exposing one glass plate 1, the glass plate 1 is taken in the first exposure shot.
It suffices that the detection area of the surface 1a of the above is aligned with the best imaging plane of the projection optical system 8. Further, if the change in the thickness of each glass plate is small in one lot, the detection area on the surface of the glass plate is best connected to the projection optical system 8 in the first exposure shot of the first glass plate in the one lot. You can see that it is better to match it to the image plane.

Next, the entire operation when exposing one glass plate 1 in this example will be described. First, when the top shot area of the glass plate 1 is exposed, the height of the Z stage in the photosensitive substrate stage 11 of FIG. 1 is once lowered to the lowest position, that is, a position away from the projection optical system 8. Lower to. As a result, as shown in FIG. 3A, the surface 1a of the glass plate 1 is located below the best imaging plane 36 of the projection optical system 8. Therefore, the chief ray L5 of the reflected light from the front surface 1a of the glass plate 1 and the chief ray L6 of the reflected light from the back surface 1b of the detection light that has passed through the first slit plate 30 are both the second slit plate 33.
Is displaced toward the glass plate 1 side with respect to the opening pattern.

From this state, the height of the Z stage of the stage 11 for the photosensitive substrate in FIG.
The surface 1a of 1 is raised toward the best imaging plane 36. As a result, first, the chief ray L5 of the reflected light from the surface 1a of the glass plate 1 reaches the vibration center of the opening pattern of the second slit plate 33, and the detection area of the surface 1a becomes the best imaging plane 36. The focus servo is applied after the adjustment. Next, in this way, the surface 1a of the glass plate 1 is
In the state in which the focus servo is applied at, the control device 12 of FIG.
The tilt angle of the surface 1a of the glass plate 1 with respect to the best imaging plane 36 is detected from the photoelectric conversion signals, and the glass plate 1 is leveled via the photosensitive substrate stage 11 so that the tilt angle becomes zero. .

In this case, since the entire exposure field on the surface 1a of the glass plate 1 is near the best imaging plane 36, the action of the first light shield plate 18 and the second light shield plate 25 causes the back surface of the glass plate 1. The reflected light from 1b does not enter the light receiving element 28, and accurate leveling is performed. Then, the pattern image of the reticle 9 is exposed on the top shot area of the glass plate 1 through the projection optical system 8. After that, when the remaining shot areas of the glass plate 1 are exposed, the exposure is performed after the leveling is performed while the focus servo is continuously applied from the first shot area.

As described above, according to this embodiment, focusing is performed by gradually moving the surface 1a of the glass plate 1 closer to the projection optical system 8 from a state in which the surface 1a of the glass plate 1 is separated from the best image forming surface 36 in advance. Since it is performed, the focus servo can be surely applied to the surface 1a of the glass plate 1. Therefore, the leveling of the surface 1a of the glass plate 1 by the horizontal position detection system can be performed accurately thereafter.

Contrary to the above embodiment, the surface 1a of the glass plate 1 is previously moved to the inside of the best image forming surface 36, and then the glass plate 1 is gradually moved away from the projection optical system 8 for focusing. A method of doing is also possible. In this case, in the initial state, as shown in FIG.
Both the surfaces having an apparent depth of e corresponding to the front surface 1a and the back surface 1b of the glass plate 1 are located above the best imaging plane 36 of the projection optical system 8. Therefore, the principal ray L5 of the reflected light from the front surface 1a of the glass plate 1 and the principal ray L6 of the reflected light from the back surface 1b of the detection light that has passed through the first slit plate 30 are both generated by the second slit plate 33. It is displaced toward the projection optical system 8 side with respect to the aperture pattern.

From this state, the height of the Z stage of the stage 11 for the photosensitive substrate shown in FIG.
The surface 1a of 1 is lowered toward the best image plane 36. As a result, first, the chief ray L6 of the reflected light from the back surface 1b of the glass plate 1 reaches the oscillation center of the opening pattern of the second slit plate 33, but the focus signal at this time is ignored and the glass plate 1 is further ignored. Lower. Next, the chief ray L5 of the reflected light from the surface 1a of the glass plate 1
When the focus signal obtained when the center of vibration of the aperture pattern of the slit plate 33 is reached is valid, the detection area of the surface 1a is aligned with the best image forming surface 36, and focus servo is applied. Next, by performing the leveling in the state where the focus servo is applied on the front surface 1a of the glass plate 1 as described above, the reflected light from the back surface 1b is blocked and the accurate leveling is performed.

Next, an example of the calibration method of the horizontal position detection system of this example will be described. In FIG.
Even if the positional relationship between the first light shielding plate 18 and the second light shielding plate 25 is first accurately matched, the position of the best image plane of the projection optical system 8 may be displaced due to changes with time or the like. Alternatively, the positional relationship between the first light shielding plate 18 and the second light shielding plate 25 may be displaced. Therefore, it is necessary to readjust the position of the second light shielding plate 25, that is, calibrate the horizontal position detection system.

Therefore, in this example, first, in a state where the detection area of the surface 1a of the glass plate 1 is aligned with the best image forming plane of the projection optical system 8, photoelectric conversion from the four light receiving surfaces of the light receiving element 28 is performed. The second light blocking plate 25 is positioned in the R1 direction so that the sum signal of the converted signals becomes maximum. At this time, almost all of the light flux reflected by the surface 1 a of the glass plate 1 is incident on the opening of the second light shield plate 25. An actuator (for example, a mechanism that drives a micrometer by a motor) that slightly moves the second light shielding plate 25 in the R1 direction is provided,
By positioning the second light shielding plate 25 so that the sum signal of the photoelectric conversion signals from the light receiving element 28 becomes maximum,
The calibration can be performed automatically.

Since reference mark plates for various alignments are arranged on the holding stage 10 in FIG. 1, the surface of the reference mark plate may be used for calibration. Further, since the glass plate 1 is affected by the back surface reflection, an opaque substrate such as a silicon wafer may be used only when calibration is performed. As a result, it is possible to perform accurate calibration without any back surface reflection.

Further, the second light shielding plate 25 may be formed by using, for example, an electrochromic element. Even if the relationship between the transparent portion and the light shielding portion is changed by the electrochromic element, the same effect as moving the second light shielding plate 25 in the R1 direction can be obtained. 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.

[0054]

According to the present invention, the focus position detecting means is used in advance to align the detection area on the surface of the object with the best image plane of the projection optical system. When using a horizontal position detection system that projects onto the surface of the test object, even if the test object is light transmissive, it can be accurately measured without being affected by the reflected light from the back surface of the test surface. There is an advantage that the inclination angle of the surface can be detected.

When the object to be inspected is a light-transmissive substrate, after setting the surface of the substrate largely outside from the best image plane of the projection optical system, the substrate is gradually moved to the If the detection area of the surface to be inspected of the substrate is aligned with the best image plane of the projection optical system while approaching the projection optical system, the back surface of the substrate becomes the best image plane of the projection optical system. It is no longer matched.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a main part of a projection exposure apparatus to which an embodiment of the present invention is applied.

FIG. 2 is a side view showing the relationship between the glass plate 1 and the focus position detection system in the embodiment of FIG.

FIG. 3A is an explanatory view of a focusing method in which the glass plate 1 is gradually brought closer to the projection optical system, and FIG. 3B is an explanatory view of a focusing method in which the glass plate 1 is gradually moved away from the projection optical system.

FIG. 4 is a principle explanatory diagram of a horizontal position detection system of a system of projecting an image of a grid pattern on the surface of a test object according to the applicant's prior application.

FIG. 5 is a diagram for explaining the influence of back surface reflection when the test object is a glass plate.

[Explanation of symbols]

 1 Glass Plate 8 Projection Optical System 9 Reticle 10 Holding Stage 11 Photosensitive Substrate Stage 12 Control Device 13 Driving Device 14 Irradiation Optical System 18 First Light-Shielding Plate 22 Condensing Optical System 25 Second Light-Shielding Plate 28 Four-divided Light-Receiving Element 30, 33 Slit plate 31, 32 Objective lens 35 Light receiving element

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G03F 9/00 H 9122-2H

Claims (2)

[Claims] 1. A projection optical system for projecting an image of a predetermined pattern on a test surface of a test object, and mounting the test object on the test optical system in an optical axis direction of the projection optical system. A stage for positioning, an irradiation optical system for obliquely projecting an image of a grid pattern from the optical axis of the projection optical system to a detection area on the surface to be inspected, and an image of the grid pattern for re-imaging A condensing optical system and a light shield which is arranged on the image plane of the re-formed image and has a grid pattern in the same pitch and in the same direction as the re-formed image of the grid pattern. A plate and a light receiving element for photoelectrically converting the light passing through the light shielding plate, and detecting the amount of inclination of the surface to be inspected with respect to a surface perpendicular to the optical axis of the projection optical system from the photoelectric conversion signal of the light receiving element. A leveling detection unit and a focus detecting unit that detects a position of the surface to be detected in the optical axis direction of the projection optical system. In a method of detecting the inclination of the surface to be inspected by a projection optical device having a residue position detecting means, the position of the detection area of the surface to be inspected in the optical axis direction of the projection optical system is detected by using the focus position detecting means. Then, after the detection area of the surface to be inspected is aligned with the best image forming surface of the projection optical system, the inclination of the surface to be inspected is detected by using the leveling detection means. Method. 2. When the object to be inspected is a light transmissive substrate, after setting the surface of the substrate largely outside from the best image plane of the projection optical system, the substrate is gradually moved. 2. The horizontal position detecting method according to claim 1, wherein the detection area on the surface of the substrate is aligned with the best image plane of the projection optical system while being brought close to the projection optical system.