JPH10242035A - Position detection method and semiconductor substrate and exposure mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detection method capable of high accuracy alignment capable of position detection during exposure without deteriorating throughput. SOLUTION: There are disposed a wafer 11 having a wafer mark 13 having an edge for scattering incident light on an exposure surface in which wafer an image obtained by vertically protecting the edge onto a parallel plane to the exposure surface is curved, and an exposure mask 12 having a mask mark 14 having an edge for scattering incident light on a surface in which mask an image obtained by vertically projecting the edge onto a parallel plane to the surface is curved, putting a gap therebetween such that the exposure surface opposes to the exposure mask 12. Herein, the curved edge parts of the wafer mask 13 and the mask mark 14 are irradiated with illumination light, and scattered light from the curved edges is observed from a direction inclined with respect to the exposure surface to detect a relative position between the wafer 11 and the exposure mask 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a position at the time of alignment, and an alignment mark.
The present invention relates to a position detection method suitable for improving the throughput of proximity exposure and an alignment mark.

[0002]

2. Description of the Related Art A vertical detection method and an oblique detection method are known as methods for aligning a wafer and a mask by using an alignment device combining a lens system and an image processing system. The vertical detection method is a method of observing the alignment mark from a direction perpendicular to the mask surface, and the oblique detection method is a method of observing the alignment mark obliquely.

As a focusing method used in the vertical detection method,
The chromatic double focus method is known. In the chromatic aberration double focus method, a mask mark formed on a mask and a wafer mark formed on a wafer (the wafer mark and the mask mark are collectively referred to as an alignment mark) are observed with light of different wavelengths and a lens is observed. This is a method of forming an image on the same plane using chromatic aberration of the system. In the chromatic aberration double focus method, since the optical resolution of the lens can be set high in principle, the absolute position detection accuracy can be increased.

On the other hand, in order to observe the alignment mark in the vertical direction, an optical system for observation enters the exposure area. If the exposure is performed as it is, the optical system blocks the exposure light. Therefore, it is necessary to retract the optical system from the exposure area during the exposure. Since a moving time for evacuation is required, the throughput is reduced. Further, since the alignment mark cannot be observed at the time of exposure, the position cannot be detected. This causes a reduction in alignment accuracy during exposure.

In the oblique detection method, since the optical system is arranged so that the optical axis is oblique to the mask surface, it can be arranged so as not to block the exposure light. Therefore, it is not necessary to retract the optical system during exposure, and the alignment mark can be observed even during exposure. Therefore, it is possible to prevent the displacement during the exposure without lowering the throughput.

[0006]

In the oblique detection method, since the wafer mark and the mask mark are observed obliquely to form an image, the absolute accuracy of position detection is reduced due to image distortion. Also,
Since the optical axis of the illumination light does not match the optical axis of the observation light, the optical axis of the illumination light cannot be arranged coaxially with the optical axis of the observation light. Therefore, the illumination optical axis is likely to deviate from the ideal optical axis. If the illumination optical axis deviates from the ideal optical axis, the image changes and it becomes difficult to perform accurate position detection.

It is an object of the present invention to provide a position detecting method capable of performing high-precision alignment capable of detecting a position during exposure without lowering the throughput.

[0008]

According to one aspect of the present invention, there is provided a wafer having a wafer mark having an edge for scattering incident light on an exposure surface, the edge of the wafer being a plane parallel to the exposure surface. The wafer having a curved portion in which a vertically projected image is curved, and an exposure mask having on its surface a mask mark having an edge that scatters incident light, wherein the edge of the exposure mask is a surface of the exposure mask. And the exposure mask having a curved portion in which an image vertically projected on a plane parallel to the exposure mask, a step of arranging a gap so that the exposure surface faces the exposure mask,
Irradiation light is applied to a curved portion of the edges of the wafer mark and the mask mark, scattered light from the curved portion is observed obliquely with respect to the exposure surface, and the relative position between the wafer and the exposure mask is measured. Detecting the position.

Since the scattered light from the edge is observed obliquely, it is possible to adopt a configuration in which the observation optical system does not enter the exposure area. Therefore, it is not necessary to retract the optical system during exposure, and scattered light from the edge can be observed even during the exposure period. Since the edges are curved, variations in the edge shape and position due to the effects of manufacturing process variations can be reduced.

According to another aspect of the present invention, there is provided an exposure surface on which an alignment wafer mark having an edge for scattering incident light is formed, and the wafer mark is perpendicular to the incident surface of the incident light. Are arranged along different directions,
A semiconductor substrate is provided in which at least a part of a vertical projection image of each edge onto the exposure surface is curved.

According to another aspect of the present invention, a positioning mask mark having an edge for scattering incident light is formed, and the plurality of mask marks are arranged along a direction perpendicular to the incident surface of the incident light. A plurality of exposure masks are provided, wherein at least a part of a vertical projection image of each edge on the surface of the exposure mask is curved.

Since the edge has a curved shape, it is possible to reduce variations in edge shape and position due to the effects of manufacturing process variations. Further, since a plurality of edges are arranged in a direction perpendicular to the incident surface, a plurality of images can be observed at the same time. By superimposing these images in parallel, the relative positions can be easily detected.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing embodiments of the present invention,
The previous proposal (Japanese Patent Application No. 7-294485) of the inventor of the present application will be described.

FIG. 1A is a schematic sectional view of a position detecting device used in an embodiment of the present invention. The position detecting device includes a wafer / mask holding unit 10, an optical system 20, and a control device 30.
It is comprised including.

The wafer / mask holder 10 comprises a wafer holder 15, a mask holder 16, and a driving mechanism 17. At the time of alignment, the wafer 11 is held on the upper surface of the wafer holder 15 and the mask 12 is held on the lower surface of the mask holder 16. The wafer 11 and the mask 12 are arranged in parallel so that a certain gap is formed between the exposure surface of the wafer 11 and the lower surface (mask surface) of the mask 12.
A wafer mark 13 for positioning is formed on the exposure surface of the wafer 11, and a mask mark 14 for positioning is formed on the mask surface of the mask 12.

The wafer mark 13 and the mask mark 14 have edges formed to scatter incident light. When light enters these marks, the incident light that strikes the edges is scattered, and the incident light that strikes other areas is specularly reflected. Here, the specular reflection refers to reflection in a form in which almost all components of the incident light are reflected in the same reflection direction.

The driving mechanism 17 can relatively move the wafer holder 15 and the mask holder 16. When the X axis is taken from left to right in the figure, the Y axis is taken from the front to the back in a direction perpendicular to the paper surface, and the Z axis is taken in the normal direction of the exposed surface, the wafer 11 and the mask 12 are relatively in the X axis direction. , Y-axis direction,
It can be moved in the Z-axis direction, the rotation direction around the Z-axis (θ _Z direction), and the rotation (tilt) direction around the X-axis and Y-axis (θ _X and θ _Y directions).

The optical system 20 includes an image detecting device 21, a lens 2
2, a half mirror 23, and a light source 24.

The optical system 20 is arranged so that its optical axis 25 is oblique to the exposure surface. Illumination light emitted from the light source 24 is reflected by the half mirror 23 and is reflected on the optical axis 25.
Are obliquely incident on the exposure surface through the lens 22. The light source 24 is disposed at the image-side focal point of the lens 22, and the illumination light emitted from the light source 24
The light is collimated by 2 into a parallel light beam. The light source 2
4 can adjust the intensity of irradiation light.

Among the scattered light scattered at the edges of the wafer mark 13 and the mask mark 14, the light incident on the lens 22 is converged by the lens 22 and forms an image on the light receiving surface of the image detecting device 21. Thus, the illumination by the optical system 20 is telecentric illumination, and the illumination optical axis and the observation optical axis are the same optical axis.

The image detecting device 21 obtains an image signal by photoelectrically converting an image scattered from the wafer mark and the mask mark formed on the light receiving surface. The image signal is input to the control device 30.

The control device 30 processes the image signal input from the image detection device 21 to detect the relative position between the wafer mark 13 and the mask mark 14. Further, a control signal is sent to the driving mechanism 17 so that the wafer mark 13 and the mask mark 14 have a predetermined relative positional relationship. The drive mechanism 17 moves the wafer holder 15 or the mask holder 16 based on the control signal.

FIG. 1B is a plan view showing the relative positional relationship between the wafer mark 13 and the mask mark 14. One mark is formed by arranging three rectangular patterns having four sides parallel to the X-axis or the Y-axis in the X-axis direction. Note that three or more rectangular patterns may be arranged as described later. The wafer mark 13 is constituted by a pair, and the mask mark 14 is arranged between the pair of wafer marks 13.

The cross section of the wafer mark 13 and the mask mark 14 in FIG. 1A is taken along the dashed line A1-A1 in FIG. 1B. The illumination light that has entered the wafer mark 13 and the mask mark 14 is scattered at the edge protruding toward the optical axis of each rectangular pattern in FIG.
The light applied to the area other than the edge is specularly reflected, and the
No light is incident on 2. Therefore, only the scattered light from the edge can be detected by the image detection device 21.

Next, the nature of an image due to edge scattered light will be described. The light intensity distribution I of an image by incoherent monochromatic light is

[0026]

(Equation 1)

## EQU2 ## Here, O (x, y) is the intensity distribution of the reflected light from the surface of the observation object, PSF (x, y) is the point spread function (point spread function) of the lens, and the integral is the integral over the entire surface of the observation object. Represent.

Focusing on one edge of each rectangular pattern in FIG. 1B, it can be considered that minute points reflecting light are arranged in parallel to the y-axis. It is assumed that the reflected light intensity distribution from this minute point is a Dirac delta function δ. In fact, the intensity distribution of the scattered light from a minute point could be approximated by a delta function. Assuming that the edge extends in the y-axis direction within a range in which the lens isoplanatism is established, O (x, y) = δ (x).

Equation (1) is

[0030]

(Equation 2)

It can be modified as follows. This I (x) is a line image intensity distribution (line spread function) of the lens,

[0032]

I (x) = LSF (x) (3) Here, LSF (x) represents the linear image intensity distribution of the lens.

When the illumination light has a continuous spectrum,

[0034]

(Equation 4)

## EQU2 ## Where λ is the wavelength of light, LS
Fλ is the line image intensity distribution of the wavelength λ, Δxλ is the lateral shift amount of the line image due to the chromatic aberration of the lens with respect to the light of the wavelength λ, and the integral is the integral over the entire wavelength region.

From equation (4), it can be seen that observing the scattered light from the edge is equivalent to observing the linear image intensity distribution of the lens. Therefore, by observing the scattered light from the edge, a stable image can always be obtained without being influenced by the in-plane intensity distribution of the reflected light from the observation object.

FIG. 1C shows the shape of an image formed by scattered light formed on the light receiving surface of the image detecting device 21 shown in FIG. 1A. The x-axis is the direction of intersection between the incident surface including the observation optical axis and the light-receiving surface (the direction corresponding to the X-axis direction of the exposure surface), and the direction orthogonal to the x-axis in the light-receiving surface (corresponds to the Y-axis direction of the exposure surface) Is defined as the y-axis, the image formed by one edge has a linear shape parallel to the y-axis. Therefore, the image of each mark has a shape in which three linear images parallel to the y-axis are arranged in the x-axis direction.

An image 14A caused by the edge scattered light of the mask mark 14 appears between the pair of images 13A caused by the edge scattered light of the wafer mark 13. Further, since the observation optical axis is oblique to the exposure surface, the image 14A of the mask mark and the image 13A of the wafer mark are detected at different positions in the x-axis direction.

FIG. 1 (C) shows the light intensity distribution in the y-axis direction of the image 13A of the wafer mark and the image 14A of the mask mark. The distance between the one wafer mark image 13A and the mask mark image 14A in the y-axis direction is y1, and the distance between the other wafer mark image 13A and the mask mark image 14A is y.
The axial distance is defined as y2. By measuring y1 and y2, the relative positional relationship between the wafer mark 13 and the mask mark 14 in FIG. 1B in the y-axis direction, that is, the direction perpendicular to the illumination light incident surface can be known.

For example, when it is desired to position the mask mark such that the mask mark is located at the center of the pair of wafer marks in the Y-axis direction, one of the wafer and the mask is positioned relative to the other such that y1 and y2 are equal. What is necessary is just to move relatively. Thus, alignment can be performed in the Y-axis direction in FIG. FIG.
(A), by three pairs arrangement for alignment marks and the optical system as shown in (B), X axis, Y axis and theta _Z
It can be aligned with respect to direction. FIG.
In (A), the case where the illumination optical axis and the observation optical axis are coaxial has been described, but it is not always necessary to be coaxial. Any condition may be used as long as specularly reflected light does not enter the objective lens of the observation optical system and only scattered light enters.

Next, a method for measuring the distance between the exposure surface and the mask surface will be described. Scattered light from a point on one plane perpendicular to the optical axis 25 in the object space of the optical system 20 simultaneously forms an image on the light receiving surface of the image detection device 21. The plane in which the points in the object space that are imaged on the light receiving surface
Call it.

Of the respective edges of the wafer mark and the mask mark, the scattered light from the edge on the object surface is focused on the light receiving surface, while the scattered light from the edge not on the object surface is not focused. Out of focus as you move away from the surface. Therefore,
An image due to scattered light from the edge closest to the object surface among the edges of each mark becomes the sharpest, and an image blurred as the distance from the edge in the X-axis direction increases.

In FIG. 1C, the distance x ₁ represents the distance in the x-axis direction between the most in-focus points of the wafer mark image 13A and the mask mark image 14A. That is, the distance x ₁ is substantially equal to the interval between the points at which the focal point of the wafer mark and the focal point of the mask mark are vertically projected on the incident surface.

FIG. 1D shows the exposure surface 11 and the mask surface 1.
2 is a cross-sectional view of the incident surface near the object surface of FIG. Point Q_TwoIs
Point Q on intersection of wafer surface 11 and object surface, point Q₁Is the mask surface
It is a point on the line of intersection between 12 and the object surface. Line segment Q₁Q_TwoLength of
Is the distance x in FIG. ₁Corresponding to

When the length of the line segment Q ₁ Q ₂ is represented by L (Q ₁ Q ₂ ), the distance δ between the exposure surface 11 and the mask surface 12 is

[0046]

Δ = L (Q ₁ Q ₂ ) × sin (α) (5) Here, α is the angle between the normal direction of the exposure surface 11 and the optical axis 25. Therefore, by determining the length of the line segment Q ₁ Q ₂ by measuring the distance x ₁ in FIG. 1 (C), the can know the interval [delta]. In order to know the interval δ more accurately, it is preferable to accurately measure the distance x ₁ . For this purpose, it is better that the focal depth of the lens is shallow. Further, in FIG. 1B, it is preferable to arrange a large number of rectangular patterns in the X-axis direction.

The control device 30 stores the distance x in advance.₁Target value
Memorized and measured distance x ₁Approaches the target value
The exposure mechanism 11 by controlling the driving mechanism 17 as described above.
The distance between the mask and the mask surface 12 can be set to a desired distance.
it can.

FIG. 2A shows an example of a perspective view of one rectangular pattern of a wafer mark. Illumination light is obliquely incident along an oblique optical axis in the XZ plane in the figure, and scattered light from an edge extending along the Y axis is observed. In this case, the image due to the scattered light has an intensity distribution represented by the above-described equation (4),
As shown in FIG. 2B, an image that is long in one direction extending along the y-axis of the light receiving surface is obtained. This image corresponds to the linear image intensity distribution of the lens.

FIG. 2C shows a pattern obtained by shortening the length in the Y-axis direction of the rectangular pattern shown in FIG. 2A. When the edge length becomes shorter than the resolution of the lens, the intensity distribution O (x, y) of the reflected light in the equation (1) becomes δ
(X, y). Therefore, equation (1) becomes

[0050]

(Equation 6)

Can be modified as follows. Where PSF
(X, y) represents the point image intensity distribution of the lens.

When the illumination light has a continuous spectrum,

[0053]

(Equation 7)

Can be expressed as follows. Here, λ is the wavelength of light, PSFλ is the point image intensity distribution of wavelength λ, and Δxλ is the wavelength λ
Represents the lateral displacement of the point image in the x-axis direction due to the chromatic aberration of the lens with respect to the light of the wavelength .DELTA.y.lamda. Represents the lateral displacement of the point image in the y-axis direction due to the chromatic aberration of the lens with respect to the light of wavelength .lamda.

As described above, by setting the length of the edge to be equal to or less than the resolution of the lens, a point image approximate to the point image intensity distribution of the lens can be obtained as shown in FIG.

FIG. 2E is a perspective view of a rectangular pattern that scatters illumination light by the vicinity of a vertex where three planes intersect. It is considered that the image due to the scattered light from the vicinity of the vertex as shown in FIG. 2E is also approximated to the point image intensity distribution as shown in Expressions (6) and (7). In this specification, one unit of a pattern having an edge that scatters illumination light is called an edge pattern.

FIG. 3 shows an example of an arrangement of a mask mark and a wafer mark having a vertex for scattering illumination light. Mask mark 62 is arranged between wafer marks 52A and 52B. Each alignment mark 52A, 52B,
And 62 are configured by arranging three rows of edge patterns having a square planar shape at a pitch P in the X-axis direction and two columns in the Y-axis direction. One vertex of each square edge pattern is arranged so as to face the positive direction of the X axis, that is, the direction of the observation optical axis.

As shown in FIG. 3, when an edge pattern having vertices for scattering the illumination light is arranged and the scattered light from the vertices is observed, the method described with reference to FIGS. The wafer and the mask can be aligned in a similar manner.

Next, a position detecting method according to an embodiment of the present invention will be described. The oblique detection optical system used in the embodiment,
This is the same as that shown in FIG. FIGS. 1B and 2A illustrate a case where positioning is performed by observing scattered light from a linear edge, and FIGS. 2E and 3 illustrate a case in which scattered light from a vertex is detected. The case where positioning is performed by observation is described. In this embodiment, the scattered light from the edge where the vertical projection image on the exposure surface or the mask surface is curved is observed.

FIG. 4A is a plan view of a wafer mark having a curved edge, and FIG. 4B is a perspective view of the wafer mark. This wafer mark is formed by patterning a Ta ₄ B film deposited on a SiC layer formed on a silicon substrate surface, and has a length of about 3 μm and a width of about 1 μm.
Are formed from three edge patterns having the mesa structure described above. Both ends of each edge pattern have a radius of curvature of about 0.5 μm
Of a semicircle. Note that an X-ray mask is formed by removing part of the silicon substrate by back etching and leaving the SiC layer.

When observing the edge scattered light from the wafer mark shown in FIG.
The silicon substrate is placed on the wafer holder 15 shown in FIG. 1A so that the in-plane direction orthogonal to it and the substrate normal direction are the X-axis, Y-axis, and Z-axis in FIG. Place on. That is, scattered light from a curved edge having a radius of curvature of 0.5 μm is observed.

FIG. 5 shows one of the wafer marks shown in FIG.
FIG. 3 shows a measurement result of a light intensity distribution when scattered light from two curved edges is observed by the oblique detection optical system shown in FIG. The vertical direction in FIG. 5 represents the light intensity, and the horizontal direction corresponds to the Y axis on the surface of the silicon substrate. That is, FIG.
(C) corresponds to the y-axis, and the depth direction corresponds to the x-axis.
The magnification of the lens of the observation optical system is 100 times, the aperture angle (NA) of the objective lens is 0.35, and the illumination light is white light.

As shown in FIG. 5, the image due to the scattered light from the curved edge is substantially dot-shaped, and the light intensity has a maximum value at almost one point. That is, it can be seen that an image substantially similar to the scattered light from the apex of the wafer mark having the apex is obtained.

The positions of the vertices as shown in FIG. 2E are easily affected by variations in the manufacturing process when forming a wafer mark. On the other hand, the position of the circumferential edge is hardly affected by variations in the manufacturing process. Therefore, it is possible to stably perform high-accuracy alignment. Although FIG. 4 shows a case where the edge of the wafer mark has a semicircular shape, any other smooth curve may be used as long as a substantially point-shaped image can be obtained. Also, in order to form a wafer mark having such a shape, it is not always necessary to smooth the outer periphery of the wafer mark pattern for forming the wafer mark. The outer periphery of the photomask may be rectangular, and a smooth edge may be formed by side etching during etching.

The radius of curvature of the edge of the wafer mark shown in FIG. 4 was about 0.5 μm. This is approximately equal to the resolution of the lens. If the radius of curvature of the edge is substantially equal to or less than the resolution of the lens, an almost point-like image is obtained by the scattered light from the edge. Therefore, in order to perform high-accuracy alignment, it is preferable that the radius of curvature of the edge is equal to or less than the resolution of the lens. This does not mean that edges with a radius of curvature larger than the resolution of the lens cannot be used. It is preferable to experimentally confirm what curvature radius is preferable in order to obtain a desired alignment accuracy by using edges having various shapes.

FIGS. 6A and 6B show an example of the arrangement of a mask mark and a wafer mark. Both have two wafer marks 40A and 40B and wafer marks 42A and 42
B are arranged in the Y-axis direction. Mask marks 41 and 4
3 are located between the two wafer marks 40A and 40B, and 42A and 42B, respectively.

Each alignment mark 4 shown in FIG.
Each of 0A, 40B, and 41 is configured by arranging an edge pattern having an oblong planar shape long in the X-axis direction in two rows in the X-axis direction and two columns in the Y-axis direction.

Each alignment mark 4 shown in FIG.
2A, 42B, and 43 are configured by arranging three rows of edge patterns having a circular planar shape in the X-axis direction and two columns in the Y-axis direction.

As shown in FIGS. 6A and 6B, even if edge patterns having smooth edges are arranged and scattered light from the edges is observed, FIGS. The alignment between the wafer and the mask can be performed by the same method as described in the above. 6 (A) and 6 (B),
Each alignment mark is configured such that when alignment is completed, one alignment mark can be translated and overlapped with another alignment mark. Therefore, the distance in the Y-axis direction between the alignment marks can be easily measured. Also, by arranging a plurality of edge patterns at a predetermined pitch in the X-axis direction, it is possible to focus on any edge,
Position detection can be performed stably. FIG.
As described in (D), the distance between the wafer and the mask can be obtained.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0071]

As described above, according to the present invention,
By observing the scattered light from the edges of the wafer mark and the mask mark obliquely, the position can be detected with high accuracy. Since the edge has a smooth curved shape, it is possible to reduce the influence of variations in the manufacturing process when forming the edge pattern. When exposing the wafer after the alignment, it is not necessary to dispose an optical system in the exposure range, so that the position can be always detected even during the exposure period. Therefore, high-precision exposure can be performed.

[Brief description of the drawings]

FIG. 1A is a schematic cross-sectional view of a position detection device used in the previous proposal and the embodiment of the present invention, and FIG. 1B is a plan view of a wafer mark and a mask mark according to the previous proposal. ,
FIG. 1C is a diagram showing an image due to edge scattered light from the wafer mark and the mask mark in FIG. 1B and a light intensity distribution in the image plane, and FIG. It is sectional drawing of the object surface vicinity.

FIG. 2 is a diagram showing a perspective view of a wafer mark and an image appearing on an image forming surface according to the above proposal.

FIG. 3 is a plan view of a wafer mark and a mask mark having vertices for scattering illumination light.

FIG. 4 is a plan view and a perspective view of an edge pattern forming a wafer mark according to an embodiment of the present invention.

FIG. 5 is a diagram showing a light intensity distribution of an image due to scattered light from one edge of the wafer mark of FIG. 4;

FIG. 6 is a plan view showing an example of the arrangement of wafer marks and mask marks according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 wafer / mask holder 11 wafer 12 mask 13 wafer mark 14 mask mark 15 wafer holder 16 mask holder 17 drive mechanism 20 optical system 21 image detector 22 lens 23 half mirror 24 light source 25 optical axis 30 controller 52, 40 , 42 Wafer mark 62, 41, 43 Mask mark 72 Object surface 73 Optical axis

Claims (10)

[Claims] 1. A wafer having, on an exposure surface, a wafer mark having an edge that scatters incident light, wherein the edge of the wafer is a curved portion in which an image vertically projected on a plane parallel to the exposure surface is curved. An exposure mask having on its surface a mask mark having an edge that scatters incident light, wherein the edge of the exposure mask has a curved image perpendicularly projected onto a plane parallel to the surface of the exposure mask. Disposing the exposure mask having a curved portion with a gap so that the exposure surface faces the exposure mask; and illuminating light on the curved portion of the edges of the wafer mark and the mask mark. And observing the scattered light from the curved portion from an oblique direction with respect to the exposure surface to detect a relative position between the wafer and the exposure mask. Law. 2. A radius of curvature of an image obtained by vertically projecting a curved portion of the edges of the mask mark and the wafer mark onto an exposure surface or a mask surface is substantially equal to or less than the resolution of an observation optical system. 2. The position detection method according to 1. 3. In the step of detecting the relative position,
The scattered light is observed by an optical system having an observation optical axis oblique to the exposure surface, and the illumination light is emitted from a direction in which specular reflection light from the wafer mark and the mask mark does not enter the optical system. The position detection method according to claim 1. 4. The position detecting method according to claim 3, wherein the optical axis of the illumination light and the observation optical axis are common. 5. A plurality of the wafer marks are arranged along a direction perpendicular to the plane of incidence of the illumination light, and the mask marks are arranged along a direction perpendicular to the plane of incidence of the illumination light. 5. The position detecting method according to claim 4, wherein a plurality of arrays are arranged, and in the step of detecting the relative position, a relative position in a direction perpendicular to a plane of incidence of the illumination light is detected. 6. The edge of the wafer mark and the edge of the mask mark are arranged so that one can be translated and overlapped with the other when alignment is completed, and the relative position is detected. 6. The step of moving the wafer and the exposure mask so that, when one of the edge of the wafer mark and the edge of the mask mark is moved in parallel, the edge of the mask can be overlapped with the other. The position detection method according to 1. 7. An exposure surface on which an alignment wafer mark having an edge for scattering incident light is formed, wherein a plurality of wafer marks are provided along a direction perpendicular to the incident surface of the incident light. A semiconductor substrate which is arranged and at least a part of a vertical projection image of each edge onto the exposure surface is curved. 8. The semiconductor substrate according to claim 7, wherein a plurality of said wafer marks are arranged along a direction parallel to an incident surface of said incident light. 9. An exposure mask in which a plurality of alignment mask marks having edges for scattering incident light are formed, and the plurality of mask marks are arranged along a direction perpendicular to an incident surface of the incident light. The exposure mask, wherein at least a part of a vertical projection image of each edge onto the surface of the exposure mask is curved. 10. The exposure mask according to claim 9, wherein a plurality of the mask marks are arranged along a direction parallel to an incident surface of the incident light.