JPH04143607A - Device for detecting horizontal position - Google Patents

Abstract

PURPOSE:To improve S/N and to enable execution of detection of high precision by a method wherein the direction of illumination on a surface to be inspected is made different from each direction in the directional properties of two directions of a pattern on the surface which intersect each other perpendicularly. CONSTITUTION:In order for a resist applied on a wafer 3 not to be exposed to light, a light flux from a light source 11 supplying a light of a different wavelength from an exposure light is focused on a stop 13 and a light source image is formed. A light flux from the light source image is turned into a parallel light flux through a first relay lens 15 and focused at a focal position through a second relay lens 17. Then, a parallel light flux from an objective lens 18 for illumination having the focus at the focal position of the lens 17 illuminates obliquely an area to be inspected being also an area of exposure on the wafer, at an angle theta of incidence. Patterns formed on areas (WP1 to WP2) to be inspected have directional properties in the directions X and Y intersecting each other perpendicularly, and a construction is so made that the direction of illumination of the parallel light flux from the objective lens 18 for illumination is inclined by an angle gamma in respect to the axis X when the illuminated area 3a is viewed from just above it. By this method, execution of detection of high precision is enabled.

Description

[Detailed Description of the Invention] [Industrial Application Field] A reference position detection device for accurately setting a wafer surface or a test object surface at a perpendicular position to the optical axis of the objective lens of the present invention;
In particular, it relates to an inclination detection device.

[Conventional technology]

In general, a reduction projection exposure apparatus for manufacturing integrated circuits uses a projection objective lens having a large numerical aperture (N, A, '), so the allowable focal range is extremely small.

Therefore, unless the exposure area of the wafer is maintained in a precise perpendicular position to the optical axis of the projection objective, it is not possible to expose a clear pattern over the entire exposure area. The entire wafer can be aligned almost perpendicularly to the optical axis of the objective lens by detecting three points on the wafer surface using a separate autofocus mechanism, but as the wafer becomes larger and With new materials, the flatness of the wafer itself becomes unstable, so it is necessary to detect the partially tilted state of the wafer. Since the deformation of the wafer is further increased by multiple exposures and chemical treatments, it is especially necessary to accurately detect the tilted state of the exposed area.

As described above, it has become essential to accurately detect the inclination of the exposure area. For example, a device for detecting the inclination of the exposure area is disclosed in Japanese Patent Laid-Open No.
In Japanese Patent No. 8-113706, a collimator-type tilt detection device as shown in FIG. 9 was proposed.

To explain this apparatus in detail, as shown in FIG. 9, the reticle 2 and the wafer 3 are maintained conjugate with respect to the projection objective lens l, and the pattern on the reticle 2 illuminated by an illumination optical system (not shown) is projected onto the wafer 3. It is reduced and projected onto the top.

On the other hand, the irradiation optical system 10 and the condensing optical system 20 are arranged symmetrically with respect to the optical axis of the projection objective lens l.

Irradiation optical system 10 that supplies a light beam with a wavelength different from that of the exposure light
The light beam from the light source 11 is focused by a condenser lens 12 onto the aperture of the diaphragm 13, and the irradiation objective lens 17 having a focal point on the diaphragm 13 converts the light beam into a parallel beam or the wafer 3.
be led upwards. The parallel light beam reflected from the wafer 3 is condensed by a condensing objective lens 21, and is received on a four-division light receiving element 22 provided at its focal position. That is, the image of the aperture 13 in the irradiation optical system is detected on this four-part light receiving element 22.

When the exposure area on the wafer 3 is kept vertical, this condensed light is received at the center of the four-part light receiving element 22, and when the exposure area on the wafer 3 is tilted by ψ from the vertical plane, the wafer 3, the parallel light beam reflected by the condensing optical system 20
is tilted by 2ψ with respect to the optical axis 20a.

Therefore, depending on the position of the focal point on the light receiving element 22, the wafer 3
The inclination of the upper exposure area is detected, the control means 31 generates a control signal corresponding to the direction and amount of displacement of the condensed light 7 east Φ on the light receiving element 22, and the drive means 32 moves the support device 33. The tilt of the exposed surface of the wafer is corrected.

[Problem to be solved by the invention]

When overprinting another pattern on a wafer on which a predetermined pattern is formed, when trying to detect the tilted state of the exposure area of wafer 3 on which the predetermined pattern is formed, the irradiation is caused by the pattern on this wafer. The parallel light beam from the objective lens 14 is diffracted, and an image of the aperture 13 in the irradiation optical system due to the specularly reflected light from the wafer (0th order forward light) is detected on the light receiving element 22, as well as ± 1. The diffraction image of the diaphragm 13 is also detected at the same time from the ±2-111·±nn next beam.

For example, when the exposure area of a wafer on which a grid-like pattern of regular unevenness is formed as shown in (b) of FIG. 1O is maintained horizontally, as shown in 1)) of FIG. , the diffracted light intensity on the light receiving element 22 has a laterally symmetrical distribution. Since the light-receiving element 22 can detect the light center of gravity of the diffracted light intensity at its center position, it is possible to actually detect a horizontal plane as an average plane, as shown by the dotted line in (bl) in FIG. can.

However, if the exposure area of the wafer on which a regular serrated grating (blazed grating) pattern as shown in FIG. 10 (al) is maintained horizontally,
As shown in (a) of the figure, the intensity of the diffracted light on the light receiving element 22 has an asymmetric distribution, and the light center of gravity shifts to the right from the center. Therefore, this light-receiving element 22 incorrectly detects that the exposure area of the wafer surface is tilted by the light gravity center position shifted to the right from the center of the light-receiving element 22. The wafer surface can be tilted. As a result, as shown by the dotted line (bl) in FIG. 12, an actually inclined surface is detected as a correct horizontal average surface.

As described above, the conventional apparatus has a problem in that it is completely unable to detect the inclination of an exposure area on a wafer surface that has a pattern with an asymmetrical diffracted light intensity distribution.

Therefore, in the above-mentioned Japanese Patent Application Laid-open No. 58-113706,
In addition to the configuration shown in FIG. 9, by arranging a relay lens that relays the four-split light receiving element 22 and a diaphragm having a minute aperture at the focal position of the condensing optical system 21, it is possible to Unnecessary diffracted light from the surface area is collected by the condensing optical system 2.
After passing through 1, it is removed by this aperture, so highly accurate detection can be achieved.

However, since the specularly reflected light (0th order light) from the wafer 3 that has passed through the micro aperture of this diaphragm is extracted as the detection light, a large amount of light cannot be obtained on the light receiving element 22, making it more stable. However, there are problems in achieving highly accurate detection.

The present invention has been made in view of the above problems, and by significantly improving the amount of light detected on the light receiving element,
It is an object of the present invention to provide a tilt detection device that can further improve the /N ratio and achieve extremely excellent detection accuracy.

[Means to solve the problem]

In order to achieve the above object, the present invention forms a predetermined region on a test surface in which a pattern having directionality in two mutually orthogonal directions is formed in a predetermined conjugate relationship, as shown in FIG. An irradiation optical system 10 includes a main objective lens 1 for the purpose of irradiation, a light source 11 for supplying a parallel light beam onto the test surface from outside the optical axis 1a of the main objective lens, and an irradiation objective lens 18.
and a condensing optical system 20 having a condensing objective lens 21 for condensing the light beam supplied from the irradiation optical system 10 and reflected on the test surface on the light receiving element 22, and A diaphragm having an aperture 13 of a predetermined shape is provided in the optical system IO at a position substantially conjugate with the light receiving element 22, and the optical axes 10a and 20a of both the optical systems are symmetrical with respect to the optical axis 1a of the main objective lens. and the light receiving element 2
2, the horizontal position detection device detects the horizontal position of a conjugate region on the test surface based on the output signal of the irradiation optical system; The irradiation direction on the test surface where the conjugate region of the test surface intersects is different for each of the two mutually orthogonal directions of the pattern on the test surface. be.

Based on the above basic configuration, the diaphragm 13 is
It is desirable to have a slit-like opening.

A more preferable configuration is that the irradiation direction on the surface to be inspected is such that a plane including the optical axis 10a of the irradiation optical system and the optical axis 1a of the main objective lens intersects a conjugate region of the surface to be inspected; Let γ be the angle formed by one of the two mutually orthogonal directions of the pattern on the test surface, and the optical axis 1a of the main objective lens and the light of the irradiation optical system. Axis 10a
When the angle formed with is θ, it is preferable that the following conditions are satisfied.

tan-1(cos θ)≦γ≦tan-' (
1/cos θ) [Function] When the parallel light beam from the irradiation optical system 10 in the conventional configuration shown in FIG. Let's look at the state of the diffracted light.

FIG. 13 shows the surface to be tested on the wafer 3 viewed from directly above.
in the direction, with a predetermined equal pitch (P in the X direction,
In the X direction, a two-dimensional diffraction grating-like pattern having P a) is formed.

Now, the irradiation direction of the parallel light beam from the irradiation objective lens 18 is
The X direction is the same as the direction of the pattern formed on the wafer, and the irradiation optical system 10 irradiates the diffraction grating pattern on the wafer 3 with a circular irradiation area 3a. .

Then, diffracted light is generated by the diffraction grating pattern within the irradiation area 3a.

To make this more concrete and easy to explain, let us take the XY coordinates with the center of the irradiation area 3a as the origin 0, and consider a ray traveling on the optical axis 10a of the irradiation objective lens 18.
As shown in FIG. 14, due to the two-dimensional lattice pattern on the wafer, the 0th order forward light (regularly reflected light) is focused on the condensing objective lens 2.
Proceeding on the optical axis 2Oa of . Since the light-receiving element 22 is placed at the focal point of the condensing objective lens 21, that is, at the pupil position It (Fourier plane), these diffracted lights on the light-receiving element 22 are processed as Franhofer diffraction. can be analyzed.

Therefore, the optical axis 20a of the condensing objective lens 21 and the irradiation area 3
Optical axis 20a of the condensing objective lens 21 for the ±1st-order diffracted light generated within a plane including the X axis of a (X° axis in the virtual plane P)
The diffraction angle is α8, and the optical axis 20a of the condensing objective lens 22 and the Y axis of the irradiation area 3a (Y' axis in the virtual plane P)
α2 is the diffraction angle of the ±1st-order diffracted light generated in a plane containing the optical axis 20a of the condensing objective lens 22, λ is the light source wavelength of the horizontal position detection device, and is the optical axis 1a of the main objective lens I.
The angle formed by the optical axis 10a of the irradiation objective lens 18 is θ
Then, the following equation is obtained.

λ 5in(θ+a, ) = −+sin θ −
-(11P.

λ sin αa = −−・−(2
)Y And since the diffraction angle of the ±1st-order diffracted light is small, sin
all#a, , sin a, cape α, , cos a
t #l, cosar #1, the above equations (1) and (
2) becomes λ λ αa = Y.

Next, the state of the diffracted light on the light receiving element 22 generated by the two-dimensional grating pattern in the test area shown in FIG. 13 will be explained.

Now, it is assumed that the test area WP on the wafer 3 within the circular irradiation area 3a irradiated by the parallel light beam from the irradiation optical system 10 is in a horizontal state, and the light receiving surface 22 of the light receiving element 22
Assuming that the shape of a is rectangular and the shape of the aperture of the aperture 13 disposed at a position conjugate with the light receiving element 22 is circular, the image S of the aperture 13 is formed on the light receiving surface 2 on the light receiving element 22, as shown in FIG.
It is formed at the center of 2a.

Here, the center on the light receiving surface 22a of the light receiving element 22 is the origin O
The xy drift is determined by the XY coordinates of the center of the irradiation area 3a on the wafer 3 and the focusing objective lens 21 shown in FIG.
This corresponds to the X'Y' coordinates of a virtual plane P whose origin is the optical axis 20a.

Therefore, the ±1st-order diffracted light (D to D,) shown in FIG.
is a ±1 diffraction image (DS) of the aperture of the aperture 13 along the xy axis of the light receiving surface 22a on the light receiving element 22.

~DS,) is formed two-dimensionally.

Now, the distances from the center of the light-receiving surface 22a of the light-receiving element to the centers of ±1 diffraction images (DS, to DS4) in the x and y directions are respectively I! 1. ! , the focal length of the condensing objective lens 21 is f, the length of the light receiving surface 22a of the light receiving element 22 in the x direction is L, the length of the light receiving surface 22a of the light receiving element 22 in the y direction is L, and the aperture 13 The radius of the image S (diffraction image DS) is r, and the optical axis 20a of the condensing objective lens 21 and the X axis of the irradiation area 3a (X' axis in the virtual plane P) shown in FIG.
The diffraction angle with respect to the optical axis 20a of the condensing objective lens 21 of the ±1st-order diffracted light generated in a plane including α is the diffraction angle of the ±1st-order diffracted light generated in a plane including
.

Then, the size of the light-receiving surface 22a of the light-receiving element 22 is expressed by a linear equation.

1, = fα, ≧□ + r −−−− (5) L
.

la=fα, ≧□r−(6) and this (
By substituting the above equations (3) and (41) into the equations 5) and 6+, the following results are obtained.

2 f λ PxCOS　θ P.

Therefore, by selecting the size of the light-receiving surface of the light-receiving element 22 so as to satisfy equations (7) and (8), it is possible to remove the diffracted light that causes detection errors.

Furthermore, as shown in FIG. 13, there are N, N, two-dimensional grid patterns on the Y-axis and
Assuming that only NY items are included, the above formulas (7) and (8)
is as follows.

D cos θ 2N, f λ L +2r≦ −・−m As an example, N t = N y = 10, D =
20mm, λ=700nm, θ=75°, then from equation (9) and αα equation, L x + 2 r≦0
．． 135mm L, +2r≦0.035mm. The radius r of the image of the aperture 13 is 0.01 mm.
Assuming that, L, ≦0.115 mm L, ≦0.015+nm.

Therefore, the size of the light receiving element is set to 0.015 mm XO,1
If it is 15 mm (L x L a) or less, the light receiving element 22 can detect the image S due to the necessary specular reflection light without detecting the image (DS, -DS4) due to unnecessary diffracted light.
Highly accurate detection of the test surface is possible.

In addition, as mentioned above, in addition to the configuration shown in FIG. Even in this case, by configuring the opening of the diaphragm provided at the focal position of the condensing objective lens 21 so as to satisfy the above equations (9) and αα, the diaphragm 13 can be filled with the necessary specularly reflected light. This has the effect that only the image S can be detected.

However, only a point light source image limited by the diaphragm in the irradiation optical system provided at a position conjugate with the light receiving element 22 can be obtained on the light receiving element 22, and since diffracted light is removed, The amount of detection light for horizontal detection becomes weak.

Therefore, the detection accuracy not only greatly depends on the performance of the light receiving element 22, but also deterioration of the S/N ratio cannot be avoided, and more stable and highly accurate detection of the horizontal position of the test surface cannot be expected. .

Therefore, the present invention focuses on the directionality of the diffracted light depending on the irradiation direction of the irradiation light beam with respect to the two-dimensional pattern formed on the surface to be inspected, and it is possible to significantly increase the amount of detected light and significantly improve the detection accuracy. The optimal configuration of the horizontal position detection device has been discovered.

〔Example〕

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG.
The same symbols are attached to the members that are functionally the same as those in the figures. The present invention will be explained with reference to FIG.

As shown, the reticle 2 and the wafer 3 are each maintained at a conjugate position with respect to the projection objective l as the main objective lens, and the pattern on the reticle 2 is illuminated by an illumination optical system (not shown), and the wafer 3 is It is reduced and projected onto the top. The printing exposure of the wafer 3 is performed in steps,
This is called the AND/REPEAT method, in which the wafer 3 is moved by a predetermined amount and exposure is performed repeatedly.

Illumination optical system lO symmetrically with respect to the optical axis of projection objective l
and a condensing optical system 20 are installed diagonally, and these two optical systems constitute a horizontal position detection device.

The illumination optical system IO includes a light source 11 and a condenser lens 12.
, an aperture 13 having a slit-shaped opening having a longitudinal direction perpendicular to the paper surface, a reflecting mirror 14, a first relay lens,
Field diaphragm 16 and second relay lens 1 that limit the detection range
7. Consists of an irradiation objective lens 18.

In this illumination optical system, in order to prevent the resist spread on the wafer 3 from being exposed to light, a light beam from a light source 11 that supplies light with a wavelength different from that of the exposure light is condensed by a condenser 12 on an aperture 13. A light source image is formed. The light flux from this light source image is reflected by the reflecting mirror 14, then becomes a parallel light flux by the first relay lens 15 having a focal point on the aperture 13, passes through the field aperture 16, and is converted into a parallel light flux by the second relay lens 17. The light is focused at the focal point. After that, the focus (focusing) of this second relay lens 17
A parallel light beam from an irradiation objective lens 18 having a focal point at a certain position obliquely illuminates a test region, which is also an exposure region on a wafer, at an incident angle θ.

As shown in FIG. 2, the pattern formed on this test area (WP+ to WP) has directionality in the XX directions perpendicular to each other, and the irradiation area 3a is irradiated when viewed from directly above. The irradiation direction of the parallel light beam from the objective lens 18 is configured to be inclined by an angle γ with respect to the X axis. With this configuration, the direction in which diffracted light is generated from the pattern of the surface to be detected on the light receiving element can be controlled, and the shape of the light receiving element of the light receiving element can be enlarged in accordance with the shape of the aperture of the aperture 13. This will be explained in detail later.

The field diaphragm 16 is connected to the test area on the wafer (exposure area WP+~
wp, >, and is formed so that the image of the aperture of the field stop 16 has the same size as, for example, a rectangular exposure area. In other words, the irradiation optical system 1
The irradiation area 3a on the test area irradiated by the parallel light beam from 0 is the exposure area (WP, ~WP,
) is formed to approximately match the

For example, the shape of the irradiation area 3a is as shown in (a) and (
As shown in bl, the field diaphragm 16 having a circular opening is provided obliquely in the optical path according to the tilt principle so as to form a circular area inscribed or circumscribed in the rectangular exposure area WP6.

Note that the field stop 16 having this obliquely provided circular opening
Instead, a field stop having an elliptical opening is arranged perpendicular to the optical path, and the irradiation area 3a or the rectangular exposure area WP is
, may be a circular area inscribed or circumscribed by . Furthermore, as shown in FIG. 3 (C1), the shape of the irradiation region 3a is not limited to a circle, and the opening shape of the field stop 16 may be made rectangular so that it almost coincides with the rectangular exposure region WP5. .

Furthermore, as disclosed in Japanese Unexamined Patent Publication No. 1-164033, the irradiation area may be changed in accordance with changes in the shape of the exposure area.

Now, the condensing optical system 20 consists of a condensing objective lens 21 and a four-part light receiving element 22 as a light receiving element.

The parallel light beam from the irradiation optical system 10 is reflected on the wafer 3 as the surface to be inspected, and is focused by the condensing objective lens 21 on the four-divided light receiving element 22 provided at its focal position.

The light-receiving surface 22a of this four-part light-receiving element 22 is formed in a rectangular shape (rectangular shape) having a longitudinal direction in the plane of the paper.
The light-receiving surface 22a is formed to a predetermined size so as to eliminate unnecessary diffracted light due to the pattern on the surface to be measured.

With the above configuration, the image S of the slit-shaped aperture of the diaphragm 13 is formed on the light-receiving surface of the four-part light-receiving element 22, so the amount of light that can be received can be greatly increased, resulting in a much more stable and highly accurate light receiving surface. Horizontal position detection can be achieved.

Note that this 4-split light-receiving element 22 is configured such that when the inclination of the image-forming surface 3a of the reticle 3 and the inclination of the upper surface of the wafer 3 match, the light beam from the irradiation optical system 10 or the center of the light-receiving surface of the 4-split light-receiving element 22 The position is set in advance so that the light is focused on the

Note that the operation of detecting inclination with the above configuration is the same as that in Japanese Patent Application Laid-open No. 113706/1983 described in the section of the prior art, so a description thereof will be omitted.

Next, the principle of the embodiment of the present invention having the above configuration will be explained. Prior to this explanation, first, the phenomenon of diffraction on the light receiving element 22 will be explained when the irradiation direction of the parallel light beam from the irradiation objective lens 18 is tilted with respect to the direction of the pattern on the test surface.

Here, it is assumed that the aperture shape of the diaphragm 13 in the irradiation optical system IO provided at a position conjugate with the light receiving element 22 is a circular shape similar to the conventional one, which is different from the above-mentioned slit shape. In addition, in order to simplify the explanation, as shown in Fig. 4,
A predetermined equal pitch in the X and X directions, which are orthogonal to each other (P work in the X direction).

It is assumed that a two-dimensional diffraction grating-like pattern with P, ) in the X direction is formed, and a pinch in the X and Y directions of the two-dimensional diffraction pattern formed on the test surface is
, , Pa) are both assumed to have the same pitch P.

In the embodiment of the present invention, as described above, when the wafer 3 is viewed directly above, the irradiation direction of the parallel light beam from the irradiation optical system 1O is controlled by the formation of a two-dimensional diffraction grating pattern. In other words, the irradiation direction of the parallel light beam from the irradiation optical system 10 is γ with respect to the X direction of the diffraction grating pattern on the wafer 3. I'm only tilting it.

As a result, on the light-receiving surface of the light-receiving element 22, as shown in FIG.
, ) changes, y' is tilted by β with respect to the X axis, and the X° axis is tilted by δ with respect to the X axis. The images (DS, to DS4) of the diaphragm 13 formed by the ±1st-order diffracted light are generated at positions separated by the same distance from the origin 0.

Therefore, even if the diffraction image (DS, to DS,) of the aperture 13 is extended greatly in the X direction, this diffraction image (DS to DS,) will not be detected. Therefore, if the shape of the aperture of the diaphragm I3 is made rectangular, for example, as shown in FIG. It can be made significantly larger.

Therefore, focusing on the directionality of the diffracted light on the light receiving element depending on the irradiation direction of the irradiation light beam with respect to the two-dimensional pattern formed on the surface to be inspected, the diffraction phenomenon in the case of FIG. 6 will be analyzed.

The length of the diffraction image (DS, -DS,) from the origin 0 in each component direction of x and y is determined by the focal length of the condensing objective lens 21 being f, and the length of the two-dimensional image formed on the test surface. When the pitch (P, , P,) of the diffraction pattern in the X and X directions is P, the following relationship holds true. Incidentally, this holds true in FIG. 5 as well, and these are approximations when the diffraction angle is small, that is, when λ/2 (l).

tan γ cos θ tan δ= cos θ・tan 7 ”−
""'αG Therefore, the light receiving surface 2 of the light receiving element 22 in the X direction
The length of 2a is L, and the light receiving surface 2 of the light receiving element 22 in the X direction
2a, the length of the image S (diffraction image DS,') of the aperture 13 in the X direction is S! , the image S of the aperture 13 in the X direction (
The length of the diffraction image DS, ) is Sa, the diameter of the irradiation area is D,
Assuming that the irradiation area 3a includes N8 and Nv two-dimensional lattice patterns on the X-axis and Y-axis, respectively, the size of the light-receiving surface 22a of the light-receiving element 22 is determined by the above formula 011.
From the set α9 of ゜α2゜0, 1---αη .

However, Nx = Ny, tanβ = cos θ
/lanγ, tanδ=tan7−CO3θ.

Here, if 0<β≦45°, as can be seen from FIG. 6, I y', ≧I! In order to avoid detecting the image of the aperture 13 (DSa, DSa) which becomes y'a and is unnecessary for detection, I! It is sufficient to consider only the length of y'. In other words, the light receiving element 22 in the X direction that satisfies the αη equation
The size of the light-receiving surface of the light-receiving surface of the light-receiving element 22 in the X direction can be made arbitrarily long.

Similarly, if 0 and δ≦45°, then 12
X', ≧lx'a, and in order not to detect the image of the aperture 13 (DS, DS,) which is unnecessary for detection, ix'
, only the length of . In other words, it is sufficient to consider the size of the light receiving surface of the light receiving element 22 in the X direction that satisfies formula 09, and similarly to the above, the size of the light receiving surface of the light receiving element 22 in the
The light-receiving surface of can be made arbitrarily long.

Therefore, when the length of the light-receiving surface of the light-receiving element 22 in one direction can be increased as described above, a two-dimensional pattern X is formed on the surface to be inspected.

The optimum range in which the irradiation direction of the parallel light beam from the irradiation optical system 10 can be tilted with respect to the X direction will be described without reference to FIG.

As shown in Figure 7 (al), the ±1st order diffraction images (DS2, D
S, ) is β=4 with respect to the X axis on the detection surface on the light receiving element 22.
In the case of occurrence on the y′ wheel axis tilted by 5°, the inclination γ of the irradiation direction of the parallel light beam from the irradiation optical system lO with respect to the X direction in which the two-dimensional pattern formed on the test surface is formed is: From formula 03, 7=tan "' (cosθ
) --(21).

In addition, a ±1st-order diffraction image (DS, , DS,) on the X′ fine axis tilted by δ with respect to the X axis is generated, and the value of δ at this time is α
From Equations 3 and 05, δ=tan −1(cos” θ) ·−1−(22).

For example, the incident angle of the parallel light beam from the irradiation optical system IO is set to θ(
If the angle between the optical axis 10a of the irradiation optical system and the optical axis 1a of the main objective lens is 75°, then δ=3.83°,
From the above equation (21), γ=14.51'.

Therefore, in this case, ZYx≦l X', so the light receiving surface of the light receiving element 22 is I! It is sufficient to consider the size of y', and as long as it is configured to a size that satisfies the above expression αη in the X direction, it can be made arbitrarily large in the X direction.

Next, by decreasing the value of γ from the state shown in fal in FIG. 7, ±1st-order diffraction images (DSt, DS,) are generated with respect to the (b) in Fig. 7, where the angle β with the axis is equal to the angle δ with the
).

In this state, the inclination γ of the irradiation direction of the parallel light beam from the irradiation optical system 10 with respect to the X direction in which the two-dimensional pattern is formed on the surface to be inspected is expressed by formula 03.

From the 00 type, γ=45° −・−, (23).

Then, the values of β and δ at this time are β=δ=tan ”(cosθ)−(24) from equations 03 and 00, and for example, the incident angle of the parallel light flux from the irradiation optical system 10 is set as θ( Optical axis 10a of the irradiation optical system and optical axis 1a of the main objective lens
If the angle formed by

Therefore, in this case, 1. y', = 1x', so the light receiving surface of the light receiving element 22 can be made arbitrarily large in the X direction as long as it is configured to a size that satisfies Equation 09 or measurement formula in the X direction.

Next, the value of γ is decreased from the state shown in (bl) in FIG.
Let us consider the case shown in FC+ in FIG. 7, which occurs on the X' fine axis tilted by δ=45° with respect to the X axis on the upper detection plane.

In this case, the inclination γ of the irradiation direction of the parallel light beam from the irradiation optical system 1° with respect to the X direction in which the two-dimensional pattern is formed on the surface to be inspected is calculated from equation 05 as 7 = tan
-' (1/cos θ) --1 (25).

In addition, ±1st-order diffraction images (DS, , DS4) on the y° wheel axis tilted by β with respect to the X axis are generated, and the value of β at this time is α
From formula 3 and formula 00, β=tan ”(cos” θ) −1−−−−
(26).

For example, the incident angle of the parallel light beam from the irradiation optical system IO is set to θ(
If the angle between the optical axis 10a of the irradiation optical system and the optical axis 1a of the main objective lens is 75°, β = 3.83°,
From the above equation (25), γ=75.49°.

Therefore, in this case, I! Since y', ≧/X', the light-receiving surface of the light-receiving element 22 may have a size of 1x°. Therefore, if it is configured to a size that satisfies the above formula 09 in the X direction, it can be made arbitrarily large in the X direction.

In this way, when the length of the light-receiving surface of the light-receiving element 22 in one direction can be increased, the length of the light-receiving surface of the light-receiving element 22 in one direction can be increased. On the other hand, the optimal range in which the irradiation direction of the parallel light beam from the irradiation optical system 1O can be tilted is the range shown in the following equation from the above equations (21) and (25).

tan-' (cos θ)≦γ≦tan-'
(1/cos θ) Therefore, by determining the irradiation direction of the parallel light beam from the irradiation optical system 10 so as to satisfy this equation (27), the length of the light receiving surface of the light receiving element 22 in one direction can be determined. The aperture of the diaphragm 13, which is provided at a position conjugate with the light-receiving surface of the light-receiving element 22, has a slit shape with a longitudinal direction, such as a rectangular shape or an ellipse shape. Significant increases can be achieved.

Therefore, it is possible to significantly improve the detection accuracy of the surface to be inspected, and also to stabilize the detection accuracy at the same time.

Here, as an example, the number N of patterns in the X direction in the test area is 1O1, the focal length f of the condensing objective lens 21 is 10
0+nm, the wavelength λ of the light source 11 is 700 nm, and the diameter of the irradiation area is 20111 m1.Irradiation optical system 1 for the test surface
The incident angle θ from 0 is 75°, and the length S8 of the image of the aperture 13 in the X direction is 0.02 mm, as shown in FIG.
(bl, (Let's look at the size of the light receiving element in the three cases of C1.

In the case of (al in FIG. 7, γ=14 from the above formula (21)
, 51°, and from the above formula (17), L8≦0.270x
sin(14,51')-0,02=0.048.

Therefore, the length of the light receiving surface 22a of the light receiving element in the X direction is
may be set to 0.048 mm or less.

In the case of (bl in Fig. 7), the above equations (13), (16)
Therefore, γ=45°, and from the above formula (17) or (19), ≦0.270xcos(45°) −0,02=
It becomes O1171.

Therefore, the length L8 of the light receiving surface 22a of the light receiving element in the X direction
may be set to 0.171 mm or less.

In Figure 7 (in the case of C1, γ = 75 from the above formula (25)
, 49°, and from the above formula (19), L1≦0.270
x cos (75,49°) −0,02=0.04
It becomes 8.

Therefore, the length L8 of the light receiving surface 22a of the light receiving element 22 in the X direction may be set to 0.048 ff1m or less.

In this way, in the case of γ=45°, which is indicated by (bl) in FIG. 7, the length of the light receiving surface 22a of the light receiving element in the X direction can be made the longest.

In the above, in order to simplify the explanation, the pattern on the test surface has been described based on a two-dimensional diffraction grating, but the above equation (27) is not limited to that case. In other words, equation (27) can be generally applied to any test pattern that has directionality in two orthogonal directions for boat fishing, as shown in WF2 in Figure 2, and in cases such as those described above. Needless to say, the same effect can be obtained.

In addition, in this embodiment, the aperture shape of the aperture 13 in the irradiation optical system 10, which is provided at a position conjugate with the light receiving element 22, is rectangular as shown in FIG. (
Any shape having a longitudinal direction such as an ellipse as shown in b) may be used.

Furthermore, the shape of the light-receiving surface 22a of the light-receiving element may be rectangular (square, rectangular), circular, elliptical, or the like.

〔Effect of the invention〕

As described above, according to the present invention, the direction in which the diffraction image generated on the light receiving element is generated can be optimally controlled. can be enlarged into a slit-like shape, and a significant improvement in the amount of detected light can be achieved.

Therefore, since the S/N ratio can be improved, the detection accuracy of the surface to be inspected can be significantly improved, and moreover, more stable horizontal position detection can be achieved.

In addition, since the length of the light-receiving surface of the light-receiving element in one direction can be arbitrarily increased, the aperture of the diaphragm in the irradiation optical system provided at a position conjugate with the light-receiving element can be increased accordingly. This makes it possible to further increase the amount of detected light.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an apparatus according to an embodiment of the present invention. Figure 2 shows two perpendicular lines in the exposure area formed on the wafer.
FIG. 2 is a plan view of a wafer showing a state in which a light beam is obliquely irradiated onto a pattern having directionality. FIG. 3 is a diagram showing the state of the irradiation area with respect to the exposure area. FIG. 4 is a plan view of the test area showing a state in which a two-dimensional grating pattern formed on the test surface is irradiated with a light beam in an oblique direction. FIG. 5 shows that when the aperture of the diaphragm 13 has a circular shape, by irradiating the light beam obliquely onto the two-dimensional grating pattern formed on the surface to be inspected shown in FIG.
FIG. 3 is a diagram showing a diffraction image formed on the light receiving surface of a light receiving element. FIG. 6 shows that when the aperture of the diaphragm 13 is rectangular in shape, by irradiating the light beam in an oblique direction onto the two-dimensional grating pattern formed on the test surface shown in FIG. FIG. 3 is a diagram showing a diffraction image formed on the light receiving surface of a light receiving element. Figure 7 shows the state of the diffraction image formed on the light-receiving surface of the light-receiving element when the irradiation direction of the light beam is changed with respect to the two-dimensional grating pattern formed on the test surface shown in Figure 4. FIG. FIG. 8 is a diagram showing the aperture of the diaphragm 13 in the irradiation optical system according to the present invention. FIG. 9 is a block diagram of a conventional device. FIG. 10 is a diagram showing the pattern formed on the surface to be inspected. FIG. 11 is a diagram showing the distribution of the amount of diffracted light according to the pattern of FIG. 10. FIG. 12 is a diagram showing how the horizontal position is detected using the pattern of FIG. 10. FIG. 13 is a plan view of the test area showing a state in which a light beam is irradiated parallel to the X direction of a two-dimensional lattice pattern formed on the test surface. FIG. 14 is a perspective view showing a state in which a light beam is irradiated parallel to the X direction of a two-dimensional grating pattern formed on a surface to be inspected. Figure 15 shows the diffraction image formed on the light-receiving surface of the light-receiving element when a light beam is irradiated parallel to the X direction of the two-dimensional grating pattern formed on the test surface shown in Figure 14. FIG. [Explanation of symbols of main parts] 1 --- Projection objective lens 2-- Reticle 3 --- Wafer 10 --- Irradiation optical system 11 ---
-Light source 13 -Aperture 20 -Condensing optical system 22 -4-split light receiving element la -.
Optical axis 10a of projection objective lens - Optical axis 20a of irradiation optical system - Condensing optical system

Claims (1)

[Scope of Claims] 1) A main objective lens for forming a predetermined region on a test surface in a predetermined conjugate relationship on which a pattern having directionality in two mutually orthogonal directions is formed, and the main objective lens. an irradiation optical system having a light source and an irradiation objective lens for supplying a parallel light beam onto the test surface from off the optical axis of the irradiation optical system; and receiving a light flux supplied from the irradiation optical system and reflected on the test surface. a condensing optical system having a condensing objective lens for condensing light on the element, and a diaphragm having an aperture of a predetermined shape at a position substantially conjugate with the light receiving element in the irradiation optical system, In the horizontal position detection device, the optical axes of both optical systems are arranged symmetrically with respect to the optical axis of the main objective lens, and the horizontal position of the conjugate region on the test surface is detected based on the output signal of the light receiving element, The irradiation directions on the test surface where the plane including the optical axis of the irradiation optical system and the optical axis of the main objective lens intersect with the conjugate region of the test surface are mutually orthogonal, which the patterns on the test surface have. A horizontal position detection device characterized in that the directionality is different for each direction in two directions. 2) The horizontal position detection device according to claim 1, wherein the diaphragm has a slit-like opening. 3) The pattern on the test surface has an irradiation direction on the test surface where a plane including the optical axis of the irradiation objective lens and the optical axis of the main objective lens intersects with a conjugate region of the test surface. Let γ be the angle formed by one of the two mutually orthogonal directions, and θ be the angle formed by the optical axis of the main objective lens and the optical axis of the irradiation objective lens. The horizontal position detecting device according to claim 1 or 2, wherein the horizontal position detecting device satisfies the following conditions. tan^-^1(cosθ)≦γ≦tan^-^1(1
/cosθ)