JPH07106243A - Horizontal position detector - Google Patents

Abstract

PURPOSE:To make it possible to detect accurately th angle of inclination of the surface of an object to a prescribed reference surface even when the object is transparent, specially is transparent and has a high-reflectivity film on the back. CONSTITUTION:A pattern image of a reticle 2 is formed on a glass substrate 3 coated with a sensitive material via a projection objective optical system 1. Either of the images through groups 17 and 18 of slit-shaped open holes in a first light-shielding plate 15 is projected on the surface of the substrate 3 obliquely to the optical axis 1a and the reflected light from the substrate 3 is received in a quadripartite photodetector 23 via either of the groups 17A and 18A of slit-shaped open holes in a second light-shielding plate 24. The groups 17 and 18 are different from each other in the width of an opening part and either of the groups 17 and 18 is used according to the intensity of the reflected light on the back of the substrate 3.

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 apparatus for detecting the inclination of a surface of a test object with respect to a predetermined reference surface, and more particularly to an exposure apparatus used in the manufacturing process of semiconductor elements and liquid crystal display elements. The present invention relates to a horizontal position detecting device that is suitable for use in.

[0002]

2. Description of the Related Art In general, a projection exposure apparatus (eg, stepper) for manufacturing a semiconductor device or a liquid crystal display device uses a projection objective optical system having a large numerical aperture (NA), and therefore the allowable focus range. Is very small. Therefore, the exposure area on the photosensitive substrate (semiconductor wafer or glass substrate whose surface is coated with resist) is parallel to a predetermined reference plane, that is, the image plane of the projection objective optical system within the range of the depth of focus. Unless maintained, a clear pattern cannot be exposed over the entire exposed area of the photosensitive substrate. When a resist-coated wafer is used as the photosensitive substrate, the height (position in the optical axis direction of the projection objective optical system) at at least three points on the wafer surface is detected by a separately provided autofocus mechanism, The exposure surface of the wafer as a whole can be aligned substantially perpendicular to the optical axis of the projection objective optical system.

However, when the size of the wafer is large or the flatness of the wafer itself is unstable, it is necessary to partially detect the height of the exposed surface of the wafer. Then, since the deformation of the wafer is further increased by the exposure and chemical treatment for each layer on the wafer, the tilt angle of the average surface of the exposure surface of the wafer with respect to the image plane of the projection objective optical system is accurately detected. Horizontal position detection is becoming indispensable.

Therefore, in order to maintain each exposed region on the wafer in the best condition, a horizontal position detecting device for detecting the average inclination of the surface of each region is proposed in the present application. It has been proposed by a person as JP-A-58-113706. The device disclosed here is
In the projection type exposure apparatus, the perpendicularity to the optical axis of the projection objective optical system can be accurately measured for each exposure area of the wafer, and the measurement performance is extremely excellent.

[0005]

However, in the conventional horizontal position detecting device as described above, when the object of tilt detection is a transparent glass substrate coated with resist,
Especially when a film having a high reflectance such as aluminum is formed on the back surface of the glass substrate, the reflected light from the back surface of the glass substrate is mixed with the reflected light from the front surface of the glass substrate,
There is an inconvenience that an error may occur in the tilt detection. Further, the light reflected from the back surface of the glass substrate is reflected on the front surface of the glass substrate and returns to the back surface, and then the light reflected on the back surface again or the light repeatedly reflected many times between the back surface and the front surface of the glass substrate. Since the light passes through the surface of the glass substrate and reaches the light receiving element, the error in tilt detection may increase.

In view of the above point, the present invention provides a predetermined test surface of the test object even when the test object is a transparent substrate, particularly a transparent substrate having a high reflectance film on the back surface. An object of the present invention is to provide a horizontal position detecting device capable of accurately detecting a tilt angle with respect to a reference plane (for example, an image plane of a projection objective optical system).

[0007]

The first horizontal position detecting apparatus according to the present invention is, for example, as shown in FIGS. 1 and 2, a surface to be inspected of an object (3) to be inspected through an irradiation objective lens (14). Irradiation optical system (10) for irradiating a parallel light beam obliquely to
And a condensing optical system (20) having a condensing objective lens (21) for condensing the light flux reflected by the surface to be inspected and a light receiving element (23) for receiving the condensed light flux, In a horizontal position detecting device for detecting the inclination of a surface to be inspected with respect to a predetermined reference surface based on a detection signal of a light receiving element (23), a slit projected onto the surface to be inspected in an irradiation optical system (10). First light blocking member (1) having a group of apertures (17)
5), and second condensing optical system (20) having a slit-shaped opening group (17A) of the same or similar shape as the slit-shaped opening group (17) in the first light-shielding member (15). The member (24) is provided at a position conjugate with the surface to be inspected, and the first light shielding member (15) and the second light shielding member (24) are arranged at a position conjugate with each other through reflection on the surface to be inspected. In addition, the longitudinal direction of each slit-shaped opening of the slit-shaped opening group (17) of the first light-shielding member (15) and the slit-shaped opening group (17A) of the second light-shielding member (24) is set to the irradiation optical system (10) and the collection. It is installed perpendicularly to the incident surface including the optical axis of the optical optical system (20), and further, the slit-shaped opening group (17) of the first light shielding member (15) and the slit-shaped opening of the second light shielding member (24). Adjusting means for changing the width of the light shielding part in each array direction of the group (17A) 31, MT _1, MT ₂₎ in which the provided.

In this case, the object (3) to be inspected is a transparent substrate onto which a predetermined pattern is transferred, and the irradiation area of the parallel light flux onto the transparent substrate (13) by the irradiation optical system (10) is the predetermined pattern. It is desirable that the size is set to be approximately the same as the size of the transfer area of. Further, the adjusting means is a slit-shaped opening group (17) of the first light shielding member (15).
It is desirable to set the width of the light-shielding portion and the width of the light-shielding portion of the slit-shaped opening group (17A) of the second light-shielding member (24) to be about twice or more the width of the corresponding slit-shaped opening group. There are cases. The first light blocking member (15) and the second light blocking member (24) each have a plurality of sets of slit-shaped opening groups (17, 18 and 17A, 18A) whose light blocking portions have different widths, and the adjustment thereof is performed. The means has exchange means (MT ₁ , MT ₂ ) for arranging each of the plurality of slit-shaped aperture groups in the optical path of the corresponding irradiation optical system (10) and condensing optical system (20) in an exchangeable manner. You may.

Further, both the first light-shielding member (15) and the second light-shielding member (24) are composed of a liquid crystal display element or an electrochromic element, and the adjusting means thereof is the first light-shielding member (15) and the second light-shielding member. A voltage controller for controlling the voltage applied to each of the light shielding member (24) may be included. Further, the adjusting means continuously or stepwise changes the widths of the respective light shielding portions of the slit-shaped opening group of the first light-shielding member (15) and the slit-shaped opening group of the second light-shielding member (24). At times, it is desirable to set the width of the light shielding portion to an optimum value for the object to be inspected (3) based on the change in the output signal output from the light receiving element (23). Next, the second horizontal position detecting device according to the present invention has the same premise as the first horizontal position detecting device.

The second horizontal position detecting device is
For example, as shown in FIG. 7, in the irradiation optical system (10), there is provided a first slit-shaped opening group projected onto the surface to be inspected.
A second light shielding member (52) provided with a light shielding member (51) and having a slit-shaped opening group in the condensing optical system (20) that is the same as or similar to the slit-shaped opening group in the first light shielding member.
Is provided at a position conjugate with the surface to be inspected, and the first light shielding member (5
1) and the second light shielding member (52) are arranged in a conjugate position through reflection on the surface to be inspected, and the first light shielding member (51)
And the second light-shielding member (52) to the irradiation optical system (1
0) and adjusting means (31, MT ₁ , MT ₂ ) for rotating about axes (51a, 52a) in the incident surface including the optical axis of the condensing optical system (20), and the adjusting means are provided. By rotating the first light-shielding member (51) and the second light-shielding member (52) via the light-shielding member, the irradiation optical system and the condensing optical system on the surface to be detected along the incident surface including the optical axis The slit-shaped opening group of the first light shielding member (51) with respect to the incident direction at
And the pitch of the conjugate image on the test surface of the slit-shaped opening group of the second light shielding member (52).

Next, the third horizontal position detecting device according to the present invention has the same premise as that of the first horizontal position detecting device.
For example, as shown in FIG. 8, in the irradiation optical system (10), there is provided a first slit-shaped opening group projected onto the surface to be inspected.
A second light blocking member (57) provided with a light blocking member (56) and having a slit-shaped opening group in the condensing optical system (20) that is the same as or similar to the slit-shaped opening group in the first light blocking member.
Are provided at positions substantially conjugate with the surface to be inspected, and the first light shielding member and the second light shielding member are arranged in a conjugate positional relationship through reflection on the surface to be inspected, and the first light shielding member ( 56)
And the longitudinal direction of each slit-shaped opening of the slit-shaped opening group of the second light shielding member (57) is set perpendicularly to the incident surface including the optical axes of the irradiation optical system and the condensing optical system,
Further, adjusting means (31, MT ₁ , MT ₂ ) for rotating the first and second light shielding members (56, 57) about axes (56a, 57a) perpendicular to the incident surface are provided, and the adjusting means are provided. By rotating the first and second light blocking members (56, 57) through the light source, the inspection of the irradiation optical system (10) and the condensing optical system (20) along the incident surface including the optical axis is performed. The pitch of the conjugate image of the slit-shaped aperture group of the first light shielding member (56) and the second light shielding member (57) on the surface to be inspected is changed with respect to the incident direction on the surface.

In the third horizontal position detecting device, the shapes of the slit-shaped opening group of the first light-shielding member (51) and the slit-shaped opening group of the second light-shielding member (52) are shown in FIG. The pattern (58) is used, and the pitches in the first periodic direction and the second periodic direction of the checkered pattern are made different from each other, and the first light shielding member (51) and the second light shielding member (5
By rotating 2) around the axes in the incident plane including the optical axes of the irradiation optical system and the condensing optical system, respectively, the first periodic direction or the second periodic direction of the checkered pattern can be obtained. Conjugate direction on the surface (60, 61)
May be set in a direction along the incident surface including the optical axes of the irradiation optical system and the condensing optical system.

[0013]

According to the first horizontal position detecting apparatus of the present invention, the object to be inspected (3) is passed through the slit-shaped opening group (17) of the first light shielding member (15) in the irradiation optical system (10). ) A slit-shaped opening of the second light-shielding member (24), which projects an image of the slit-shaped pattern group on the surface to be inspected and arranges the light from the object to be inspected (3) in the condensing optical system (20). Receive light through group (17A). At this time, the first light blocking member (15) and the second light blocking member (15)
Since the light-shielding member (24) and the light-shielding member (24) are conjugate with each other with respect to the reflection on the test surface, the light receiving element (23) can receive only the reflected light from the test surface. That is, the object to be inspected (3)
From the back surface of the object, the reflected light from the back surface of the object (3) to be reflected and the reflected light from the back surface twice, and the back surface is reflected three times or more. Most of the reflected light is removed by the light-shielding portion of the slit-shaped opening group (17A) of the second light-shielding member (25) arranged in the condensing optical system (20). Therefore, the influence of reflected light on the back surface of the object to be inspected (3) on the horizontal position detection is reduced, and the tilt angle of the surface to be inspected can be accurately detected.

Also, the adjustment is performed to change the width of the light-shielding portion in the arrangement direction of the slit-shaped opening group (17) of the first light-shielding member (15) and the slit-shaped opening group (17A) of the second light-shielding member (24). Since the means (31, MT ₁ , MT ₂ ) is provided, by changing the width of the light-shielding portion, for example, only the light reflected by the first reflection on the back surface of the object (3) to be inspected or It is possible to receive only the light reflected by the second reflection on the back surface. This allows
The influence on the horizontal detection of the reflected light by the first and second reflections on the back surface of the object to be inspected (3) can be individually known. Further, the object to be inspected (3) is a transparent substrate onto which a predetermined pattern is transferred, and the irradiation area of the parallel light flux onto the transparent substrate (3) by the irradiation optical system (10) is the transfer area of the predetermined pattern. When the size is set to be approximately the same as the size, the influence of the reflected light on the back surface of the transparent substrate (3) is removed, and then the average surface inclination angle of the transfer area is accurately obtained. be able to.

Further, the adjusting means is the first light shielding member (1
5) The width of the light shielding portion of the slit-shaped opening group (17) and the second
When the width of the light-shielding portion of the slit-shaped opening group (17A) of the light-shielding member (24) is set to be about twice the width of the opening of the corresponding slit-shaped opening group or more, for example, as shown in FIG. , The width of the dark part (26A) of the image (25) of the slit-shaped aperture group on the test object (3) is the width w of the bright part (26B).
More than twice. Therefore, 2 on the back surface of the object to be inspected (3)
It is possible to block the light that is reflected once. In addition, the first light shielding member (15) and the second light shielding member (24) each have a plurality of sets of slit-shaped opening groups (17, 18 and 17A, 18A) having mutually different widths of the light shielding portions, and adjusting the same. The means includes an irradiation optical system (10) and a condensing optical system (2) corresponding to each of the plurality of sets of slit-shaped apertures interchangeably.
In the case of having the exchange means (MT ₁ , MT ₂ ) arranged in the optical path of 0), the width of the light shielding portion can be easily changed mechanically.

Further, both the first light-shielding member (15) and the second light-shielding member (24) are composed of a liquid crystal display element or an electrochromic element, and the adjusting means is the first light-shielding member (15) and the first light-shielding member (15). When a voltage controller for controlling the voltage applied to each of the two light blocking members (24) is provided, the slit-shaped opening group (17) of the first light blocking member (15) and the second light blocking member (24) The slit-shaped opening group (17A) can be expressed in the form of a liquid crystal pattern or the like. Therefore, the width of the light shielding portion of the slit-shaped opening group (17, 17A) can be electronically and easily and substantially continuously changed. Further, the adjusting means continuously or stepwise changes the widths of the respective light shielding portions of the slit-shaped opening group of the first light shielding member (15) and the slit-shaped opening group of the second light shielding member (24). When the width of the light-shielding portion is set to an optimum value for the object to be inspected (3) on the basis of the change in the output signal output from the light receiving element (23), the object to be inspected (3) may be changed. A light-shielding portion having an optimum width is set.

Next, according to the second horizontal position detecting device of the present invention, as shown in FIGS. 7 (a) and 7 (b), for example, the adjusting means (31, MT ₁ , MT ₂ ) When the first light blocking member (51) and the second light blocking member (52) are rotated, an image (5) of the slit-shaped aperture group on the test surface of the test object (3) is obtained.
3) longitudinal direction and the direction of the incident surface on the test surface (5
5) angle θ _x changes and the direction of the incident surface (55)
The pitch px of the image (53) of the slit-shaped aperture group to is also changed. Therefore, when the object to be inspected (3) is a transparent substrate and the light reflected from the back surface thereof is strong, the light reflected from the back surface of the object to be inspected (3) has a slit-shaped opening group depending on the thickness of the object to be inspected (3). The angle θ _x (pitch p so that it enters the dark part of the image (53)
Adjust x). This allows the reflected light from the back surface to
The light is blocked by the light blocking member (52), and the inclination angle of the test surface with respect to a predetermined reference plane can be accurately detected.

Next, according to the third horizontal position detecting device of the present invention, for example, as shown in FIG.
The first light blocking member (56) and the second light blocking member (56) through T ₁ , MT ₂ )
The light blocking member (57) is connected to the axis (56a, 57a) perpendicular to the incident surface.
When it is rotated around a), the pitch of the image of the slit-shaped aperture group in the direction (55) of the incident surface on the test surface changes. In this case, the image of the slit-shaped aperture group is partially defocused depending on the rotation angle, but it is substantially a problem when the size of the light source (11) in the irradiation optical system (10) is small. Alternatively, by making the irradiation optical system (10) and the condensing optical system (20) telecentric, the pitch uniformity of the image of the slit-shaped aperture group is maintained. Therefore, like the second horizontal position detecting device,
The object to be inspected (3) is adjusted by adjusting the pitch of the image of the slit-shaped aperture group according to the thickness of the object to be inspected (3).
The reflected light from the back surface of the light is blocked by the second light blocking member (57), and the inclination angle of the test surface with respect to the predetermined reference surface can be accurately detected.

Further, in the third horizontal position detecting device, the shapes of the slit-shaped opening group of the first light-shielding member (51) and the slit-shaped opening group of the second light-shielding member (52) are shown in FIG. The checkerboard pattern (58) shown is provided, and the pitches in the first and second periodic directions of the checkerboard pattern are made different from each other, and the first light-shielding member (51) and the second light-shielding member (52) are respectively irradiated with these irradiation optics. By rotating about the axis in the incident plane including the optical axis of the system and the condensing optical system, the first periodic direction of the checkered pattern or the second periodic direction thereof
Direction on the surface to be inspected (60, 6)
By setting 1) in the direction (X direction) along the incident surface including the optical axes of the irradiation optical system and the condensing optical system, the pitch of the images of the slit-shaped aperture group on the surface to be inspected is increased. Can be changed.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a horizontal position detecting device according to the present invention will be described below with reference to the drawings. In this example,
The present invention is applied to a leveling system of a reduction projection type exposure apparatus that projects and exposes a pattern image of a reticle onto a glass substrate coated with a photoresist. FIG. 1 is a schematic optical path diagram of a reduction projection type exposure apparatus of the present embodiment. In FIG. 1, a pattern formation surface of a reticle 2 and a surface of a glass substrate 3 coated with a photoresist (exposure) with respect to the projection objective optical system 1. Plane) and the pattern image on the reticle 2 illuminated by an illumination optical system (not shown) are reduced and projected onto the surface of the glass substrate 3. The glass substrate 3 is held on the wafer stage 33 via the wafer holder 34. The wafer stage 33 moves the glass substrate 3 in a plane (XY plane) perpendicular to the optical axis of the projection objective optical system 1.
XY stage for positioning, the Z stage for positioning the glass substrate 3 in the Z direction parallel to the optical axis of the projection objective optical system 1, and the tilt angle of the exposure surface of the glass substrate 3 for imaging the projection objective optical system 1. It is composed of a leveling stage etc. for setting parallel to the surface. As an example, this leveling stage adjusts the inclination angle of the glass substrate 3 by adjusting the amount of protrusion of each of the three fulcrums in the Z direction.

When the pattern of the reticle 2 is exposed on the glass substrate 3, a main control system 31 for controlling the operation of the entire apparatus.
Drives the wafer stage 33 via the drive unit 32,
Printing exposure is repeated by a step-and-repeat method while sequentially moving the glass substrate 3 by a predetermined amount.
Then, the same exposure operation is repeated every time a reticle having a different pattern is exchanged. Further, the irradiation optical system 10 and the condensing optical system 20 are arranged symmetrically in the X direction parallel to the paper surface of FIG. 1 with the optical axis 1a of the projection objective optical system 1 interposed therebetween.
When the glass substrate 3 is leveled, the irradiation optical system 10 irradiates the glass substrate 3 as an object to be detected with detection light. Then, the reflected light from the glass substrate 3 is received by the condensing optical system 20, and the horizontal position of the exposure area of the glass substrate 3 is detected, that is, the optical axis 1 of the projection objective optical system 1.
The tilt is detected from a plane (image plane) perpendicular to a.

The irradiation optical system 10 comprises a light source 11, a collimator lens 12a, a condenser lens 12b, a diaphragm 13 having a minute circular aperture, an irradiation objective lens 14 and the like. In the irradiation optical system 10, the light from the light source 11 is converted into a parallel light flux by the collimator lens 12a, the parallel light flux is guided to the condenser lens 12b via the mirror M ₁ , and the condenser lens 12b collects the parallel light flux. Illuminates and stops the image of the light source 11
3 is formed on the minute opening. The irradiation objective lens 14 has a focus on a minute aperture of the diaphragm 13, and the irradiation objective lens 14
Converts the divergent light beam from the minute aperture into a parallel light beam and supplies it to the glass substrate 3. Further, between the collimator lens 12a and the condenser lens 12b of this example, a disk-shaped first light shielding plate 15 having a plurality of slit-shaped opening groups is arranged.

FIG. 2A shows the first light shielding plate 15,
In FIG. 2 (a), circular light transmission plates 16 are formed around the first light shielding plate 15 at intervals of approximately 90 °, and first light shielding plates and light transmitting portions are alternately arranged in the radial direction. The slit-shaped opening group 17, the second slit-shaped opening group 18 formed by alternately arranging the light shielding part and the light transmitting part in the radial direction, and the second light shielding part and the light transmitting part are alternately arranged in the circumferential direction. The formed third slit-shaped opening group 19 is provided. The main control system 31 rotates the first light-shielding plate 15 about the shaft 15a via the drive motor MT ₁ (see FIG. 1), so that the light transmitting plate 16 and the first slit-shaped opening groups 17 to 3 are formed. Any one of the slit-shaped aperture groups 19 is set to the collimator lens 1 of FIG.
It can be arranged between 2a and the condenser lens 12b. Collimator lens 12a and condenser lens 12b of FIG.
And the slit-shaped opening groups 17 and 1 when arranged between
The longitudinal direction of each of the openings 17a and 18a of 8 is a direction perpendicular to the paper surface of FIG. 1, and the longitudinal direction of each of the opening portions 19a of the third slit-shaped opening group 19 is parallel to the paper surface of FIG. Direction.

For example, assuming that the first slit-shaped opening group 17 in the first light shielding plate 15 is arranged between the collimator lens 12a and the condenser lens 12b in FIG. 1, the first slit-shaped opening group 17 is formed. Images of the plurality of openings 17a of the opening group 17 are projected onto the surface of the glass substrate 3 as the object to be inspected. The longitudinal direction of each opening 17a of the first slit-shaped opening group 17 is defined by the optical axis 10a of the irradiation optical system 10 and the focusing optical system 2.
It is perpendicular to the incident surface (the paper surface of FIG. 1) including the optical axis 20a of 0. The light supplied from the irradiation optical system 10 has a wavelength different from that of the exposure light for illuminating the reticle 2 because the resist on the glass substrate 3 is not exposed. The irradiation area of the light flux irradiated from the irradiation optical system 10 to the surface of the glass substrate 3 is substantially the same as the exposure field of the projection objective optical system 1 on the glass substrate 3. Thereby, the inclination of the exposure field can be detected.

Further, in this example, with respect to the irradiation side image forming optical system including the condenser lens 12b and the irradiation objective lens 14,
The arrangement surface of the first light shielding plate 15 and the surface of the glass substrate 3 satisfy the so-called tilted arrangement based on the Scheimpflug principle. The so-called tilted arrangement based on the Scheimpflug's principle is generally an arrangement in which three planes of the object plane, the image plane, and the main plane of the imaging optical system intersect in a straight line. In this arrangement, since the object distance and the image distance are different between the conjugate planes, it is inevitable that the imaging magnification varies depending on the position, but a clear image of the object can be formed over the entire image surface. Therefore, in the exposure area of the glass substrate 3 of this example, images of the plurality of openings of the first slit-shaped opening group 17 in the first light shielding plate 15 are clearly formed on the entire surface.

On the other hand, the condensing optical system 20 includes the condensing objective lens 2
1, collimator lens 22a, condenser lenses 22b and 4
It has a divided light receiving element 23 and the like. The luminous flux supplied from the irradiation optical system 10 and reflected on the surface of the glass substrate 3 is condensed by the condenser objective lens 21 in the condenser optical system 20.
After being focused at the focal position of 1, the collimator lens 22a
Is converted into a parallel light flux by. This parallel light beam is reflected by the mirror M
₂ is incident on the condenser lens 22b via
By b, the light is focused on the four-division light receiving element 23 provided at the rear focus position. The detection signals of the four light receiving portions of the four-division light receiving element 23 are supplied to the main control system 31. The main control system 31 obtains the coordinates of the center of gravity of the light amount distribution of the reflected light on the light receiving surface of the four-division light receiving element 23 based on the magnitude relationship of these four detection signals. When the surface of the glass substrate 3 tilts,
Since the position of the center of gravity of the light amount distribution on the light receiving surface of the four-division light receiving element 23 changes, the main control system 31 obtains the inclination angle of the surface of the glass substrate 3 from the position of the center of gravity of the light amount distribution on the light receiving surface. . Further, when the surface of the glass substrate 3 is parallel to the image forming plane of the projection image forming optical system 1, the barycentric position (reference position) of the light amount distribution is obtained, and the main control system 1 moves the inside of the wafer stage 33. Driving the leveling stage, part 4
By setting the barycentric position of the light amount distribution of the light receiving surface of the divided light receiving element 23 at its reference position, the surface of the glass substrate 3 is set parallel to the image forming surface of the projection objective optical system 1. In addition,
An image pickup device such as a two-dimensional CCD may be used instead of the four-division light receiving device 23.

However, since the glass substrate 3 has a back surface reflection, it is necessary to remove the influence of the back surface reflection. Therefore, in this example, the collimator lens 22 in the condensing optical system 20
A disk-shaped second light shielding plate 24 is disposed between a and the condenser lens 22b. The arrangement surface of the second light shielding plate 24 is conjugate with the surface of the glass substrate 3 as the object to be inspected, and regarding the reflection on the surface of the glass substrate 3, the second light shielding plate 24 is the first light shielding plate in the irradiation optical system. It is conjugate with 15. The second light shielding plate 24 has a plurality of slit-shaped opening groups, like the first light shielding plate 15. FIG. 2B shows the second light shield plate 24. In FIG. 2B, the circular light transmission plates 16A and the first light shield plate 15 are arranged around the second light shield plate 24 at intervals of approximately 90 °. The first slit-shaped aperture group 17 and the substantially first conjugate
17A, the second slit-shaped opening group 18A of the first light-shielding plate 15, and the second slit-shaped opening group 18A of the first light-shielding plate 15 and the third slit-shaped opening group 19 of the first light-shielding plate 15 A conjugate third slit-shaped opening group 19A is provided. By rotating the second light shielding plate 24 via the main control system 31 drives the motor MT ₂ (see FIG. 1) about the shaft 24a, the light transmitting plate 16A, a first slit-shaped aperture group 17A~ third Any of the slit-shaped aperture groups 19A can be arranged between the collimator lens 22a and the condenser lens 22b in FIG.

When arranged between the collimator lens 22a and the condenser lens 22b of FIG. 2, the slit-shaped aperture group 1
The longitudinal direction of each of the openings 17Aa and 18Aa of 7A and 18A is the direction perpendicular to the paper surface of FIG.
The longitudinal direction of each opening 19Aa of the slit-shaped opening group 19A is parallel to the paper surface of FIG. Here, assuming that the first slit-shaped opening group 17A in the second light shielding plate 24 is arranged between the collimator lens 22a and the condenser lens 22b in FIG. 1, the first slit-shaped opening group is formed. The longitudinal direction of each opening of 17A is perpendicular to the incident surface (paper surface of FIG. 1) including the optical axis 10a of the irradiation optical system 10 and the optical axis 20a of the condensing optical system 20. Furthermore, in this example,
Regarding the condensing side imaging optical system including the condensing objective lens 21 and the collimator lens 22a, the surface of the glass substrate 3 and the disposition surface of the second light shielding plate 24 satisfy the so-called tilted disposition based on the Scheimpflug principle. Has become. Therefore, the first slit-shaped opening group 1 of the second light shielding plate 24 of this example
An image of the first slit-shaped aperture group 17 projected on the surface of the glass substrate 3 is clearly formed on the entire surface of 7A.

In FIG. 1, light rays showing the conjugate relationship with the light source 11 are shown by solid lines, and light rays showing the conjugate relationship between the respective light shielding plates 15 and 24 and the surface of the glass substrate 3 are shown by broken lines. Figure 1
As indicated by a solid line therein, the light flux irradiated on the surface of the glass substrate 3 is a parallel light flux, and the first light shielding plate 15 is also arranged in the parallel light flux. As described above, the projection system of the first light shield plate 15 by the irradiation optical system 10 is telecentric on both the object side and the image side. Similarly, in the condensing optical system 20, the surface of the glass substrate 3 and the second light shielding plate 24.
The projection system that conjugates and is also telecentric on both sides. Therefore, even if the first light shielding plate 15 and the second light shielding plate 24 are arranged so as to be inclined with respect to the optical axes 10a and 20a of the respective optical systems, and the so-called tilted arrangement based on the Scheimpflug's principle is adopted, the respective light shielding is There is no partial difference in magnification between the projected images of the plates 15 and 24 on the surface of the glass substrate 3. That is, the constant pitch of the slit-shaped openings of the first light-shielding plate 15 is set on the surface of the glass substrate 3 as well.
Strictly maintained on the second light shielding plate 24, respectively.

In the so-called tilting arrangement based on the Scheimpflug's principle, the object distance and the image distance are different between the conjugate planes, so that it is inevitable that the imaging magnification differs depending on the position. By adjusting to a predetermined inclination, a clear image of the object can be formed over the entire image plane. By using the Scheimpflug's principle in this way, even when the conjugate area on the surface of the glass substrate 3, that is, the area on the glass substrate 3 onto which the pattern on the reticle 2 is projected by the projection objective optical system 1, is large, It is possible to form an image of each slit-shaped opening group clearly over the entire surface. Here, the operation of the first light shielding plate 15 and the second light shielding plate 24 of this embodiment will be described with reference to FIGS. 3 and 4.

As described above, the irradiation optical system 10 allows the first slit-shaped aperture group 1 of the first light shielding plate 15 shown in FIG.
7 is projected onto the surface of the glass substrate 3 as the object to be inspected, and the first slit-shaped opening group 17A of the second light-shielding plate 24 in the condensing optical system 20 is also arranged conjugate with the surface of the glass substrate 3. . Here, since the glass substrate 3 is a transparent substrate,
The generation of reflected light from the back surface is inevitable. Further, when a film having a high reflectance such as aluminum is provided on the back surface of the glass substrate 3, the reflected light from the back surface is reflected on the back surface side by the front surface of the glass substrate 3 and is reflected on the back surface for the second time. The reflection on this back surface continues in the same way from the second time onward, but 3
Since the reflected light that is reflected more than once has a low intensity, it is assumed here that the horizontal position detection is not affected.

Due to the conjugate relationship between the first light shielding plate 15 and the second light shielding plate 24 as described above, the reflected light reflected by the back surface of the glass substrate 3 at the first and second times can be removed. To this end, the first slit-shaped opening group 17 of the first light-shielding plate 15 and the first slit-shaped opening group 17A provided in the second light-shielding plate 24 are obtained by projecting them on the surface of the glass substrate 3, respectively. The pitch p of the images of the slit-shaped aperture group and the width w of the images of the apertures need to be determined in the following relationship. FIG. 3 shows a first light shielding plate 15 projected on the surface 3a of the glass substrate 3 as an object to be inspected.
6 is an optical path diagram showing a state in which an image 25 of the first slit-shaped aperture group 17 and a parallel light flux reaching the front surface 3a of the glass substrate 3 are reflected by the front surface 3a and the back surface 3b. In FIG. 3, the optical path of the light reflected to the outside by the front surface 3a of the glass substrate 3 is shown by a solid line, and the optical path of the light reflected by the back surface 3b of the glass substrate 3 is shown by a broken line. The image 25 of 17 is obtained by arranging dark portions 26A and bright portions 26B having a width w at a pitch p in a direction (X direction) parallel to the paper surface of FIG. Further, in FIG. 3, the glass substrate 3 of the first slit-shaped opening group 17A (see FIG. 2B) in the second light shielding plate 24 provided in the condensing optical system 20 of FIG.
The conjugate image on the surface 3a of the is almost coincident with the image 25.

FIG. 4 is a plan view of the image 25 projected on the surface 3a of the glass substrate 3 in FIG. 3. As shown in FIG. 4, the image 25 is the image of the projection objective optical system 1 of FIG. It is formed in a circular area that substantially matches the exposure field. Returning to FIG. 3, in this example, only the reflected light on the surface 3a of the glass substrate 3 of the image-forming light flux of the image 25 of the first slit-shaped aperture group 17 projected by the irradiation optical system 10 is a condensing optical system. 20
It is configured to pass through the openings of the first slit-shaped opening group 17A of the second light shielding plate 24 arranged inside. Specifically, in FIG. 3, the bright portion 26B of the image 25 corresponds to the opening 17a of the first slit-shaped opening group 17 and the opening 17Aa of the first slit-shaped opening group 17A of FIG.
The dark portion 26A of 5 corresponds to the light shielding portion of the first slit-shaped opening 17 and the light shielding portion of the first slit-shaped opening 17A of FIG. Then, as shown in FIG. 3, the light reflected by the back surface 3b of the glass substrate 3 (indicated by the broken line) is the dark portion 26A, that is, the light shielding portion of the first slit-shaped opening 17A of the second light shielding plate 24. It is configured to be shielded from light.

Here, in FIG. 3, the light L ₀ supplied to the surface 3a of the glass substrate 3 by the irradiation optical system 10 of FIG.
Where θ _{1 is} the incident angle of light, θ ₂ is the refraction angle of the light L _{0 in} the glass substrate 3, d is the thickness of the glass substrate 3, and n is the refractive index of the glass substrate 3, the well-known refraction law is known. Therefore, the following equation is established. sin θ ₁ = n sin θ ₂ (1) Then, the reflected light on the front surface 3 a of the glass substrate 3 and the back surface 3 b
The amount of lateral deviation from the reflected light in the X direction in the X direction, that is, the deviation amount x of the back surface reflected light due to the back surface reflection in the glass substrate 3 is as follows.

X = 2 dtan θ₂ (2) Then, the reflection caused by the first reflection on the back surface 3b
Light L₁ Lateral shift amount of x ₁ For the second reflection on the back surface 3b
Reflected light L generated by₂ Lateral shift amount of x₂ Then,
Since the thickness d of the lath substrate 3 is constant, the following relation holds.
stand. x₁ = X₂ (= X) (3) As is clear from FIG. 3, the glass substrate of the slit-shaped opening group.
The width w and the pitch p of the bright portions 26B of the image 25 on the plate 3
Therefore, the following relationships must be satisfied.

2x + w <p (4) and w <x (5) By combining the expressions (4) and (5), the following relationship is obtained. w <x <(p−w) / 2 (6) Therefore, the image 2 of the slit-shaped opening group on the glass substrate 3
It is necessary that the width w and the pitch p of the bright portion 26B of No. 5 satisfy this relationship.

By the way, the pitch p of the image 15 and the width w of the bright portion 26B on the surface 3a of the glass substrate 3 are arbitrary within a range satisfying the relationship of the above expression (6). It is desirable to select an appropriate value in consideration of the fluctuation range of the thickness d. However, from the above relationship, the bright part 26
It is clear that the width w of B must not exceed 1/3 of the pitch p. Since the bright portion 26B corresponds to the opening portion 17a of the first slit-shaped opening group 17, the value (w / p) of the ratio of the width w of the bright portion and the pitch p is defined as the "opening ratio" of the slit-shaped opening group. ". However, in order to maximize the aperture ratio (w / p), if w = p / 3, the thickness d of the glass substrate 3 satisfying the relationship of the above formula (6) becomes the following single value. It will be limited.

D = p / (6 tan θ ₂ ) (7) This causes inconvenience when the thickness of the glass substrate 3 varies or when substrates having different thicknesses are dealt with, so the aperture ratio is smaller than 1/3. Will be required. Aperture ratio 1 /
If it is smaller than 3, a substrate having a thickness d in a certain range can be dealt with, but the aperture ratio (w /
It is desirable to set p) between 20% and 30%.
For example, the refractive index n of the glass substrate 3 is 1.50, the irradiation optical system 1
The incident angle θ of the parallel light flux irradiated onto the glass substrate 3 by 0
₁ at 60 °, image 2 of slit-shaped aperture group on glass substrate 3
The pitch p of 5 is 4 mm, and the bright portion 26B which is the image of the opening
Assuming that the width w of 1 is 1 mm, the following is obtained from the above equation (5).

1 mm <x <1.5 mm By substituting this into the above equation (2), the range of the thickness d of the glass substrate 3 is as follows. 0.7 mm <d <1.4 mm Therefore, the above condition can be satisfied in this range. Thus, the pitch p and the width w of the bright portion of the image 25 of the slit-shaped aperture group on the surface 3a of the glass substrate 3 are as follows.
From the value of, the pitch p ₁ and the width w ₁ of the opening 17a for the first slit-shaped aperture group 17 of the first light-shielding plate 15 in the irradiation optical system 10 and the second light-shielding plate in the condensing optical system 20. The pitch p ₂ and the width w _{2 of the} opening width of the 24 first slit-shaped opening groups 17A are determined. That is, the values of the pitch of the slit-shaped opening groups and the width of the openings in the first light shielding plate 15 and the second light shielding plate 24 are the glass substrate 3 respectively.
It is given by the product of the value relating to the upper projected image 25 and the reciprocal of the projection magnification on the surface 3a of the glass substrate 3. For this reason,
When the first light-shielding plate 15 and the second light-shielding plate 24 are in a conjugate relationship of equal magnification through reflection on the surface 3a of the glass substrate 3, both light-shielding plates have the same shape and the same slit. Since each of the plurality of aperture groups is provided, the pitch and the aperture width are equalized as follows.

P ₁ = p ₂ , w ₁ = w ₂ However, when the conjugate relationship between the first light-shielding plate 15 and the second light-shielding plate 24 is out of the same size, each slit-shaped opening group has a similar shape. Become. In a practical configuration, the first light shield 1
5 is projected on the surface 3a of the glass substrate 3 at a magnification of 1/2, and the second light shielding plate 24 also has a conjugate relation of 1/2 to the surface 3a of the glass substrate 3. In this case, The values of the pitch and the opening width of the slit-shaped opening groups on both the light shielding plates 15 and 24 are the same as the above-mentioned surface 3 of the glass substrate 3.
It will have twice the value on a. That is, the following relationship holds.

P ₁ = p ₂ = 2p, w ₁ = w ₂ = 2w If there is no film having a high reflectance on the back surface 3 b of the glass substrate 3, that is, the second reflected light on the back surface is detected horizontally. When the intensity is so low that there is no influence, the first light shielding plate 15 and the second light shielding plate 24 need only remove the reflected light L ₁ from the first back surface 3b. As a matter of course, depending on the relationship between the pitch p of the slit-shaped aperture group and the width w of the aperture image as described above, this 1
Although the reflected light on the back surface of the second time can be removed, the amount of light condensed on the four-division light receiving element 23 in FIG. 1 is small. If the width w of the aperture image of the slit-shaped aperture group is made as large as possible, more accurate horizontal detection can be performed.
It is desirable that the pitch and the opening width of the fifth and second light shielding plates 24 have the following relationship so that only the reflected light from the back surface of the first time is removed. In addition, as the slit-shaped opening group used to remove only the first reflected light on the back surface 3b of the glass substrate 3 as described above, the second slit-shaped opening group 18 (see FIG. 2) is used in the first light shielding plate 15. ) Is used, and the second light shielding plate 24 uses the second slit-shaped opening group 18A.

FIG. 5 shows an image 27 of the second slit-shaped aperture group 18 projected on the surface 3a of the glass substrate 3 as an object to be inspected and a parallel light flux reaching the surface 3a of the glass substrate 3 on the glass substrate. 3 is an optical path diagram showing a state of being reflected on the front surface and the back surface of FIG. 3, and the image 27 has a dark portion 2 at a pitch p ′ in the X direction.
8A and bright portions 28B having a width w'are arrayed. In FIG. 5, the light reflected by the front surface 3a of the glass substrate 3 is shown by a solid line, and the light reflected by the back surface 3b is shown by a broken line. Further, the incident angle θ ₁ and the refraction angle θ of the light L ₀ incident on the glass substrate 3 are
₂ , the thickness d of the glass substrate 3 and the refractive index n of the glass substrate 3
For, the relationship of the above equations (1) and (2) is established. When the lateral deviation amount of the _first reflected light L _{1 on} the back surface 3b is x ′, the width w ′ and the pitch p ′ of the bright portion of the image 27 on the glass substrate 3 need to satisfy the following relationships. is there.

X '+ w'<p'(8) and w'<x'(9) By combining these relationships, the following condition is obtained. w '<x'<(p'-w') (10) Therefore, the width w'and the pitch p'of the bright portion 28B of the image 27 need to satisfy this relationship.

By the way, the pitch p'on the surface 3a of the glass substrate 3 and the width w'of the bright portion 28B are arbitrary within the range satisfying the above relationship, but the fluctuation range of the thickness of the glass substrate 3 or the like. It is desirable to select an appropriate value from the relationship of. However, from the above relationship, it is clear that the width w'of the bright portion 28B should not exceed 1/2 of the pitch p '. However, if the width w'of the bright portion 28B is p '/ 2 in order to maximize the aperture ratio (w' / p '), the thickness d of the substrate satisfying the relationship of the above formula (5) is It is limited to only one value like. d = p / (4 tan θ ₂ ) (11) This causes inconvenience when the thickness of the glass substrate 3 is changed or when substrates having different thicknesses are dealt with.
It is necessary to make it smaller than 50%. If the aperture ratio is smaller than 50%, it is possible to deal with a substrate having a thickness d within a certain range, but the aperture ratio (w ′ /
It is desirable to set p ') between 10% and 50%.

For example, the refractive index n of the glass substrate 3 is 1.50,
The incident angle θ ₁ of the parallel light flux irradiated onto the glass substrate 3 by the irradiation optical system 10 is 60 °, the pitch p ′ of the image 27 of the slit-shaped aperture group on the glass substrate 3 is 3 mm, and the width of the image 28B of the bright portion. When w'is 1 mm, the following is obtained from the above equation (5). 1 mm <x <2 mm Further, the range of the thickness d of the glass substrate 3 is as follows from the relationship of the above formula (2).

0.7 mm <d <1.4 mm Within this range, the above conditions can be satisfied. In this example, by simply rotating the first light shielding plate 15 and the second light shielding plate 24 in FIG. 1, the first slit-shaped aperture groups 17 and 17A corresponding to the projection image 25 in FIG. 3 and the projection image 27 in FIG. The second slit-shaped opening groups 18 and 18A corresponding to can be easily exchanged. Therefore, it is possible to detect the horizontal position with high accuracy according to the state of the reflectance or the like of the back surface 3a of the glass substrate 3. In addition to this, by simply rotating the first light shielding plate 15 and the second light shielding plate 24 of FIG. 1, the light transmitting plate 16 and the light transmitting plate 16 having no light shielding portion in each of the irradiation optical system 10 and the condensing optical system 20 are transmitted. A plate 16A can be placed. This makes it possible to determine the magnitude of the influence of the reflected light on the back surface 3b of the first and second times on the horizontal position detection,
The optimum slit-shaped aperture group or light transmission plate can be selected. Hereinafter, a method of selecting the plurality of slit-shaped aperture groups and the light transmission plate will be described.

First, the light transmission of the first light shielding plate 15 of FIG.
Over plate 16, used to block only the back surface reflected light for the first time
The second slit-shaped opening group 18 used and the back of the second time
First slit used for blocking surface reflection light
The amount of light passing through each of the aperture groups 17 is 1, a and
And b. Instead of the glass substrate 3,
Silicon wafer with no internal refraction or fiducial mark plate, etc.
By arranging, it is possible to measure accurately.
Further, in each case, the light reaches the four-division light receiving element 23.
The light intensity is A₀ , A₁ And A₂And Actual standard
Light quantity B ₀ , B₁ And B₂Respectively as follows
become.

B ₀ = A ₀ (12) B ₁ = A ₁ / a (13) B ₂ = A ₂ / b (14) At this time, the light quantity B ₀ is the front surface reflected light, the first back surface reflected light and It is the sum of the second back surface reflected light. Similarly, the amount of light B ₁
Is the sum of the front surface reflected light and the second back surface reflected light, and the light quantity B ₂ is the light quantity of only the front surface reflected light. Therefore, the size of the light quantity C ₂ of first light quantity C ₁ of the light reflected by the lower surface, the second light reflected by the lower surface, respectively as follows.

C₁= B₀-B₁ (15) C₂= B₁-B₂ (16) Light amount C of the back surface reflected light of the first time₁ And second reverse side
Light intensity C₂Is the amount of surface reflected light B₀When compared with
The influence on the horizontal position detection of each depending on the size of
You can look up. For example, the light amount C₁ And C₂Each of
Each value is the light intensity B ₀If it exceeds 10%, the horizontal position detection will be affected.
Is given, (C₁+ C₂) / B₀ <0.1 (10%)
For example, light transmission plates 16, 16A, C₁/ B₀ > 0.1 and C₂/ B₀ 
If <0.1, the second pickpocket that blocks the first back reflection light.
Group of apertures 18, 18A, C₂/ B₀ > 0.1 twice
First slit-shaped opening group for blocking back-side reflected light up to eyes
Control is performed so as to select 17, 17A respectively.

With the configuration shown in FIGS. 3 and 5 as described above, it is possible to satisfactorily remove the reflected light from the back surface, which cannot be avoided when the object to be inspected is transparent like the glass substrate 3. Become. Since the optical axis 10a of the irradiation optical system 10 and the optical axis 20a of the condensing optical system 20 are symmetrically arranged with respect to the optical axis 1a of the projection objective optical system 1, the optical axis of the projection objective optical system is arranged. The surface 3 of the glass substrate 3 with respect to 1a
If the exposure area of a is perpendicular to the optical axis 1a, the light beam from the irradiation optical system 10 is condensed at the central position of the four-division light receiving element 23. Further, if the exposure area of the surface 3 a of the glass substrate 3 is tilted by an angle α from the state perpendicular to the optical axis 1 a, the parallel light flux from the irradiation optical system 10 reflected by the glass substrate 3 is condensed by the focusing optical system 20. 2α with respect to the optical axis 20a of
Therefore, the light beam is condensed on the four-division light receiving element 23 at a position off the center. Therefore, the tilt direction of the exposure area of the glass substrate 3 is detected from the position of the condensing point on the four-division light receiving element 23, and the control means 31 corresponds to the displacement direction and the amount of the condensing point on the four-division light receiving element. Then, the drive device 32 drives the wafer stage 33 to move the wafer holder 34 so as to correct the inclination of the exposure surface of the glass substrate 3.

Then, partial inclination detection is performed on the exposed surface of the glass substrate 3 in the range irradiated by the irradiation optical system 10, and the irradiation area on the glass substrate 3 is almost the same as the exposure area by the projection objective optical system 1. By setting the size, the average surface of the exposure area can be automatically set to be in a state of being accurately perpendicular to the optical axis 1a of the projection objective optical system 1. The detection of the inclination of the surface of the surface to be detected by the position of the focused spot formed on the light receiving element is also disclosed in detail in the above-mentioned Japanese Patent Laid-Open No. 58-113706. In the configuration of the embodiment shown in FIG. 1, as described above, the first light-shielding plate 15 projected by the irradiation optical system 10 and the second light-shielding plate 24 arranged in the condensing optical system 20 form respective images. Is telecentric on both sides with respect to each other, so that it is possible to accurately project a slit image with a constant pitch without causing a partial magnification difference even in the tilted arrangement. However, as described in relation to the pitch of the image of the slit-shaped aperture group on the surface of the glass substrate 3 and the width of the bright portion,
Since there is a certain allowable range in practical use, the first light shield 1
The telecentricity on both sides of the fifth and second light shields 24 is not always necessary. However, since it is necessary to make parallel light flux on the glass substrate 3 side, telecentricity on the glass substrate 3 side is required.

Further, both the first and second shading plates 15 and 24 are arranged in a so-called tilting manner based on the Scheimpflug's principle, but when the size of the light source 11 is sufficiently small and the depth of focus is large, each shading plate is arranged. It is also possible to arrange 15 and 24 perpendicular to the optical axes 10a and 20a, respectively. In this case, each shading plate 1 is provided on the surface of the glass substrate 3.
Although the images of Nos. 5 and 24 are slightly blurred at their peripheral portions, even if the light-shielding plate side (object side) is not telecentric, there is no difference in magnification between the periphery and the center of the images. Therefore, the blurring in the peripheral portion depends on the size of the area on the surface of the glass substrate 3 on which each shading plate is to be projected, that is, the size of the area on which the image of the reticle 2 is reduced and projected by the projection objective optical system 1. If the amount is acceptable, each shading plate 15, 2
It is possible to make the change in the pitch of the image of the slit-shaped aperture group of No. 4 smaller than in the case of the tilt arrangement.

The third slit-shaped opening group 19 in the first light-shielding plate 15 and the third slit-shaped opening group 19A in the second light-shielding plate 24 shown in FIG. It can be used to detect the inclination angle of the surface of a semiconductor wafer or the like and when a predetermined circuit pattern or the like is formed on the surface.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the first light shielding plate 15 and the second light shielding plate 24 of the embodiment of FIG. 1 are replaced with liquid crystal panel type light shielding plates, and the arrangement method of each light shielding plate is changed. Portions corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 6A shows
FIG. 7 is a schematic optical path diagram of the reduction projection type exposure apparatus of the present embodiment, and in FIG. 6A, a liquid crystal panel in the irradiation optical system 10 between the collimator lens 12 a and the condenser lens 12 b is perpendicular to the optical axis 10 a. A first light blocking plate 29 of the formula is arranged. Further, in the condensing optical system 20, the collimator lens 22a
A second light-shielding plate 30 of a liquid crystal panel type is arranged between the light collecting lens 22b and the condenser lens 22b perpendicularly to the optical axis 20a.

FIG. 6B shows a liquid crystal panel type first light shielding plate 2.
9B, in the first light-shielding plate 29, the dark portion 41B and the width w ₁ are formed on the first light-shielding plate 29 at a pitch p ₁ in a direction conjugate with the X direction of the surface of the glass substrate 3 of FIG. 6A. A slit-shaped opening pattern group 40 in which a plurality of bright portions 41A are arranged is displayed. The bright portion 41A corresponds to the openings 17a, 18a, 19a of the first light shielding plate 15 of FIG. The longitudinal direction of the bright portion 41A is the direction (Y direction) perpendicular to the paper surface of FIG. The pattern in the illumination area 42 of the slit-shaped opening pattern group 40 is image-projected on the surface of the glass substrate 3. Then, the main control system 31A of this example includes the slit-shaped opening pattern group 4 displayed on the first light-shielding plate 29 via the driving device 32A.
The pitch p _{1 of} 0 and the width w ₁ of the bright portion 41A can be set to arbitrary values. At this time, depending on the voltage supplied from the driving device 32A to the first light shielding plate 29, the bright portion 41A
The width w ₁ may be changed.

Similarly to the first light-shielding plate 29, the second light-shielding plate 30 of the liquid crystal panel type has a dark portion and a width at a pitch p ₂ in a direction conjugate with the X-direction on the surface of the glass substrate 3 of FIG. 6A. A slit-shaped opening pattern group in which a plurality of bright portions of w ₂ are arranged is displayed. The main control system 31A in this example is the drive unit 3
2A, the pitch p ₂ and the width w ₂ of the bright portion are set to values corresponding to the pitch p ₁ of the first light-shielding plate 29 and the width w _{1 of the} bright portion, respectively. It goes without saying that a display panel such as an electrochromic device can be used in addition to the liquid crystal panel. Returning to FIG. 6A, in the image forming relationship between the first light shielding plate 29 and the second light shielding plate 30 respectively arranged in the irradiation optical system 10 and the condensing optical system 20, only the glass substrate 3 side is telecentric. The light-shielding plate side is not telecentric, and the light-shielding plates 29, 30 are
Are arranged perpendicular to the optical axes 10a and 20a, respectively. Therefore, the arrangement surface of the first light shielding plate 29 and the surface of the glass substrate 3 are substantially conjugated, and the surface of the glass substrate 3 and the arrangement surface of the second light shielding plate 30 are substantially conjugated. The other structure is substantially the same as that of the embodiment of FIG.

In such a structure, since the liquid crystal panel type first light blocking plate 29 and the second light blocking plate 30 are perpendicular to the respective optical axes, the respective conjugate relations with the surface of the glass substrate 3 are constant. An image on the surface of the glass substrate 3 of the slit-shaped opening pattern group of the pitch is maintained at a constant pitch,
Blurring in the peripheral portion of the projected image can be substantially ignored by reducing the size of the light source 11. Then, also in this embodiment, as described with reference to FIG. 3, it is possible to satisfactorily remove the reflected light from the back surface due to the fact that the test object (glass substrate 3) is transparent. Become. Strictly speaking, the images of the respective shading plates 29 and 30 on the glass substrate 3 are perpendicular to the optical axis and are not parallel to the surface of the glass substrate 3 as shown in FIG.
It can be considered that the configuration is substantially the same as that of FIG. Also,
According to the output of the four-division light receiving element 23, the surface of the glass substrate 3 is set to the optimum position by the main control system 31A via the driving device 32A, as in the above-described embodiment.

Next, a third embodiment of the present invention will be described with reference to FIG. 7, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. Figure 7 (a)
Shows the reduction projection type exposure apparatus of the present embodiment.
In (a), the optical axis of the irradiation optical system 10 and the optical axis 1 are arranged between the mirror M ₁ and the condenser lens 12b in the irradiation optical system 10.
The first light shielding plate 51 is arranged rotatably around an axis 51a in the incident surface including a and. Further, a second light shielding plate 52 is arranged between the collimator lens 22a in the condensing optical system 20 and the mirror M ₂ so as to be rotatable about an axis 52a in the incident surface thereof, and the axes 51a and 52a are connected to each other. The drive motors MT ₁ and MT ₂ can be rotated by an arbitrary angle.

Slit-shaped opening groups are formed on the light-shielding plate 51 at a predetermined pitch, and the slit-shaped opening groups are also formed on the light-shielding plate 52 so as to be conjugated with the slit-shaped opening groups through the surface of the glass substrate 3. Are formed. That is, the first light shielding plate 51 is in a positional relationship with the surface of the glass substrate 3 and the Scheimpflug condition is satisfied, and the surface of the glass substrate 3 and the second light shielding plate 52 is in a relationship with the Scheimpflug condition. In this case, the projected image of the slit-shaped opening group of the first light shielding plate 51 on the surface of the glass substrate 3 is, as shown in FIG. 7B, an incident surface (light of the irradiation optical system 10 and the condensing optical system 20). (A plane including the axis) and an incident direction 55 along the line of intersection of the surface and the surface, the lattice pattern image 53 intersects at an angle θ _x , and the lattice pattern image 53 has dark portions 54A and bright portions 54B perpendicular to the longitudinal direction. It is arranged at a pitch p in the direction.

The lattice pattern image 53 in the incident direction 55
Is px, and the pitch px changes depending on the angle θ _x . In this embodiment, the glass substrate 3 is rotated by rotating the light shielding plates 51 and 52 about the shafts 51a and 52a.
The pitch px can be set according to the thickness of the. The pitch px is set so that the light, which has passed through the bright portion 54B of the lattice pattern image 53 of FIG. 7B and is directed to the back surface of the glass substrate 3, reaches the dark portion 54A after being reflected by the back surface.

When the size of the light source 11 is small,
Since the light rays that illuminate the slit-shaped aperture groups on the light blocking plates 51 and 52 are substantially parallel to each other, the first light blocking plate 51 and the surface of the glass substrate 3, and the surface of the glass substrate 3 and the second light blocking plate 52 are not always required. It does not need to meet the conditions of the Scheimpulf. In that case, as in the embodiment of FIG.
The normal directions of the surfaces 1, 52 may be parallel to the optical axes of the irradiation optical system 10 and the condensing optical system 20, respectively.

In FIG. 7B, the angle θ _x formed by the incident direction 55 (direction parallel to the X axis) and the lattice pattern image 53 on the surface to be inspected, and the pitch px of the lattice pattern image 53 in the incident direction 55. Has the following relationship. px = p / | sin θ _x | (17) From this expression, the pitch p can be adjusted by adjusting the angle θ _x.
It can be seen that x can be varied continuously from p to infinity. Therefore, the glass substrate 3 having any thickness can be used. Specifically, as in FIG. 3, the incident angle of the irradiation light from the irradiation optical system 10 with respect to the glass substrate 3 having the refractive index n is set to θ ₁ , and the thickness d of the glass substrate 3 which is input in advance or the thickness sensor measures it. The condition of the pitch px in the incident direction 55 is as follows using the different thickness d.

Px ≧ 2d / (n ² / sin ² θ ₁ −1) (18) By satisfying this condition, the duty ratio (aperture ratio) of the lattice pattern image 53 can be brought close to the maximum value of 50%. Therefore, the amount of detected light increases, and the S of the detection signal is increased.
The N ratio becomes high. Next, a fourth embodiment of the present invention will be described with reference to FIG.
Will be described with reference to. 8, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 8 shows a reduction projection type exposure apparatus of this embodiment. In FIG. 8, the mirror M ₁ and the condenser lens 12b in the irradiation optical system 10 are shown.
The first light-shielding plate 56 is rotatably provided between the first light-shielding plate 56 and the optical axis of the irradiation optical system 10 and the optical axis 1a. Further, a second light shielding plate 57 is arranged between the collimator lens 22a and the mirror M ₂ in the condensing optical system 20 so as to be rotatable about a vertical axis 57a in the plane of incidence thereof, and the axes 56a and 57a. Can be rotated by arbitrary angles by drive motors MT ₁ and MT _{2 (} not shown).

Slit-shaped openings are formed on the light-shielding plate 56 at a predetermined pitch, and slit-shaped openings are also formed on the light-shielding plate 57 so as to be substantially conjugate with the slit-shaped openings through the surface of the glass substrate 3. A group is formed. The longitudinal directions of the slit-shaped openings of the slit-shaped opening group on the light shielding plates 56 and 57 are set to axes 56a and 57a (directions perpendicular to the incident surface), respectively. In this case, the first light-shielding plate 51 does not satisfy the surface of the glass substrate 3 and the condition of Scheimpflug, and the surface of the glass substrate 3 and the second light-shielding plate 52 do not satisfy the condition of Scheimpflug. However, since the light source 11 is small and the light shielding plate 56 is illuminated by the substantially parallel light flux, the unevenness in magnification of the projected image on the surface of the glass substrate 3 is negligible.

In this embodiment, the light shielding plates 56 and 57 are used.
By rotating each of them about axes 56a and 57a, respectively, the pitch in the incident direction of the lattice pattern image projected on the surface of the glass substrate 3 is continuously changed. Therefore, the influence of the back surface reflection of the glass substrate 3 can be reduced by adjusting the pitch according to the thickness of the glass substrate 3.

In the third embodiment shown in FIG. 7, the checkerboard pattern may be formed on the light shielding plates 51 and 52. FIG. 9 shows a projected image of the checkered pattern on the surface of the glass substrate 3. In FIG. 9, the checkered pattern image 58 has a pitch px in the first direction 60 and a second direction 61 orthogonal to the first direction 60. Dark pitch 59 with pitch py
A and bright portions 59B are arranged in a checkered pattern.
In this case, the shading plates 51 and 52 of FIG.
When rotated around 2a, the checkered pattern image 58 rotates in the φ direction in FIG. Therefore, the checkered grid pattern image 58 is rotated in the φ direction, and the first direction 60 or the second direction 61 is set to the direction of the incident surface (the direction parallel to the X axis). The thickness can be accommodated.

By the way, in the above description, it is determined whether or not the partial area which is the exposure area on the surface of the glass substrate 3 by the projection objective optical system 1 is perpendicular to the optical axis 1a of the projection objective optical system 1. It was made possible to detect. However, the reticle image projected onto the glass substrate 3 by the projection objective optical system 1 intentionally moves the glass substrate 3 onto the optical axis 1a because of the superposition with the pattern already exposed and transferred onto the glass substrate 3. On the other hand, there is also a case where the exposure is performed with a slight angle tilted from a vertical surface. In such a case, it goes without saying that what should be detected is whether or not the surface of the glass substrate 3 as the object surface to be inspected is parallel to the image plane of the projection objective optical system 1. However, since the surface of the glass substrate 3 is basically arranged to be perpendicular to the optical axis of the projection objective optical system 1, in the above-mentioned embodiment, the above-mentioned structure is used for the sake of clarity and simplification of the configuration. In such a case, whether or not the surface of the glass substrate 3 is perpendicular to the optical axis of the projection objective optical system 1 is detected.

The horizontal position detecting device according to the present invention is
The present invention is not limited to the reduction projection type exposure apparatus shown in the embodiments, but can be used, for example, when inspecting an object to be inspected with a microscope. In this case, it goes without saying that the observation area of the microscope is irradiated with the light beam for tilt detection on the observation surface of the object to be inspected. 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.

[0069]

According to the first horizontal position detecting device of the present invention, by the combination of the first light shielding member and the second light shielding member,
Since it is possible to satisfactorily remove the reflected light generated on the back surface of the object to be inspected, even if the object to be inspected is formed of a transparent substrate, particularly a transparent substrate having a film of high reflectance on the back surface, There is an advantage that the inclination angle of the surface to be inspected with respect to a predetermined reference plane (for example, the image plane of the projection objective optical system) can be accurately detected.

Further, since the width of the light-shielding portion of the slit-shaped opening group can be changed by the adjusting means, when there is a film having a high reflectance on the back surface of the transparent substrate as the object to be inspected,
The optimum width of the light-shielding portion can be selected when reflection on the back surface does not occur, and the horizontal position can be detected with high accuracy. Further, the adjusting means sets the width of the light shielding portion of the slit-shaped opening group of the first light shielding member and the width of the light shielding portion of the slit-shaped opening group of the second light shielding member to the width of the opening portion of the corresponding slit-shaped opening group. When it is set to about twice or more, the reflected light reflected twice on the back surface of the transparent substrate as the test object can be removed.

The first light-shielding member and the second light-shielding member each have a plurality of sets of slit-shaped opening groups each having a width of the light-shielding portion different from each other, and the adjusting means adjusts the slit-shaped opening group of the plurality of sets. When the exchanging means is arranged in the optical path of the corresponding irradiation optical system and condensing optical system so as to be exchangeable, the width of the light shielding portion of the slit-shaped opening group can be easily changed mechanically.

Further, the first light shielding member and the second light shielding member are
When the liquid crystal display element or the electrochromic element is used and the adjusting means has a voltage controller that controls the voltage applied to each of the first light shielding member and the second light shielding member, electronically simple control is possible. With slit-shaped opening (pattern)
The width of the light blocking portions of the group can be changed almost continuously. Further, when the adjusting means continuously or stepwise changes the widths of the light shielding portions of the slit-shaped opening group of the first light-shielding member and the slit-shaped opening group of the second light-shielding member, the output from the light-receiving element is performed. When the width of the light shielding portion is set to an optimum value for the object to be inspected based on the change in the output signal, the inclination angle of the surface to be inspected of the object to be inspected can be detected more accurately.

Next, according to the second horizontal position detecting device of the present invention, the first light-shielding member and the second light-shielding member are rotated about an axis in the incident plane, so that the surface to be inspected is rotated. The pitch of the slit-shaped aperture group image in the incident direction can be adjusted. According to the third horizontal position detecting device of the present invention,
By rotating the first light shielding member and the second light shielding member about an axis perpendicular to the incident surface, the pitch in the incident direction of the slit-shaped aperture group image on the test surface can be adjusted. Therefore, according to these second and third horizontal position detecting devices,
Since the reflected light generated on the back surface of the object to be inspected can be removed well, even if the object to be inspected is made of a transparent substrate, particularly a transparent substrate having a high-reflectance film on the back surface, a predetermined object to be inspected There is an advantage that the tilt angle of the surface with respect to a predetermined reference plane (for example, the image plane of the projection objective optical system) can be accurately detected. In this case, since the aperture ratio of the slit-shaped aperture group can be set to about 50%, the SN of the detection signal is good.

Further, in the third horizontal position detecting device, the slit-shaped opening group of the first light-shielding member and the slit-shaped opening group of the second light-shielding member each have a checkered pattern, and the checkered pattern When the pitches in the first periodic direction and the second periodic direction are made different from each other, it is possible to deal with transparent inspected objects having two types of thicknesses with a simple configuration.

[Brief description of drawings]

FIG. 1 is an optical path diagram showing a schematic configuration of a reduction projection type exposure apparatus to which a first embodiment of a horizontal position detecting apparatus according to the present invention is applied.

2A is a front view showing a configuration of a first light shielding plate in FIG. 1, and FIG. 2B is a plan view showing a configuration of a second light shielding plate in FIG.

FIG. 3 is a cross-sectional view showing a projected image of a slit-shaped opening group and an optical path of irradiated light when the light reflected once or twice by the back surface of the glass substrate 3 is removed.

FIG. 4 is a plan view showing a projected image of a slit-shaped opening group in FIG.

FIG. 5 is a cross-sectional view showing a projected image of a slit-shaped opening group and an optical path of irradiated light when the light once reflected on the back surface of the glass substrate 3 is removed.

6A is an optical path diagram showing a schematic configuration when a second embodiment of the present invention is applied to a reduction projection type exposure apparatus, and FIG. 6B is a first liquid crystal panel type in FIG. 6A. It is a figure which shows the display pattern of the light-shielding plate 29.

7A is an optical path diagram showing a schematic configuration when a third embodiment of the present invention is applied to a reduction projection type exposure apparatus, and FIG. 7B is a projected image on the glass substrate 3 of FIG. 7A. FIG.

FIG. 8 is an optical path diagram showing a schematic configuration when a fourth embodiment of the present invention is applied to a reduction projection type exposure apparatus.

9 is an enlarged plan view showing another example of the projected image on the glass substrate 3 used in the third embodiment of FIG.

[Explanation of symbols]

 1 Projection Objective Optical System 2 Reticle 3 Glass Substrate 10 Irradiation Optical System 12b Collimator Lens 13 Aperture 14 Irradiation Objective Lens 15 First Light-Shielding Plate 17, 18, 19 Slit-Shaped Aperture Group 17A, 18A, 19A Slit-Shaped Aperture Group 20 Focusing Optics System 23 4-division light receiving element 24 Second light-shielding plate 51 First light-shielding plate 52 Second light-shielding plate 55 Incident direction

Claims (9)

[Claims] 1. An irradiation optical system for irradiating a test surface of a test object with a parallel light flux from an oblique direction through the irradiation objective lens, and a condenser objective lens for condensing the light flux reflected by the test surface. In a horizontal position detecting device, comprising: a light collecting optical system having a light receiving element for receiving the collected light flux, and detecting an inclination of the surface to be inspected with respect to a predetermined reference surface based on a detection signal of the light receiving element, A first light blocking member having a slit-shaped opening group projected on the surface to be inspected is provided in the irradiation optical system, and is the same as the slit-shaped opening group in the first light blocking member in the condensing optical system. Alternatively, a second light-shielding member having a similar slit-shaped opening group is provided at a position conjugate with the surface to be inspected, and the first light-shielding member and the second light-shielding member are reflected by the surface to be inspected. The slit of the first light shielding member is arranged at a conjugate position The slit-shaped openings of the slit-shaped opening group and the slit-shaped opening group of the second light-shielding member, the longitudinal direction of which is set perpendicularly to the incident surface including the optical axes of the irradiation optical system and the condensing optical system, and A horizontal position detecting device comprising: an adjusting unit that changes a width of a light shielding portion in each array direction of the slit-shaped opening group of the first light shielding member and the slit-shaped opening group of the second light shielding member. 2. The object to be inspected is a transparent substrate onto which a predetermined pattern is transferred, and the irradiation area of the parallel light flux onto the transparent substrate by the irradiation optical system is approximately the size of the transfer area of the predetermined pattern. The horizontal position detecting device according to claim 1, wherein the horizontal position detecting devices have the same size. 3. The slit-shaped opening corresponding to the width of the light-shielding portion of the slit-shaped opening group of the first light-shielding member and the width of the light-shielding portion of the slit-shaped opening group of the second light-shielding member, respectively. 3. The horizontal position detecting device according to claim 1, wherein the horizontal position detecting device is set to have a width of at least twice the width of the opening of the group. 4. The first light-shielding member and the second light-shielding member each have a plurality of sets of slit-shaped openings each having a different width of the light-shielding portion, and the adjusting means has a plurality of sets of slit-shaped openings. The horizontal position detecting device according to claim 1 or 2, further comprising an exchanging unit for arranging each of the groups in an exchangeable manner in the optical paths of the irradiation optical system and the condensing optical system. 5. The first light-shielding member and the second light-shielding member are both composed of a liquid crystal display element or an electrochromic element, and the adjusting means includes the first light-shielding member and the second light-shielding member. The horizontal position detecting device according to claim 1, further comprising a voltage controller that controls a voltage applied to each of them. 6. The adjusting means continuously or stepwise changes the widths of the respective light shielding portions of the slit-shaped opening group of the first light-shielding member and the slit-shaped opening group of the second light-shielding member. The horizontal position detecting device according to claim 1 or 5, wherein the width of the light shielding portion is set to an optimum value for the object to be inspected, based on a change in the output signal output from the light receiving element. . 7. An irradiation optical system for irradiating a test surface of a test object with a parallel light beam from an oblique direction through the irradiation objective lens, and a condenser objective lens for condensing the light beam reflected by the test surface. In a horizontal position detecting device, comprising: a light collecting optical system having a light receiving element for receiving the collected light flux, and detecting an inclination of the surface to be inspected with respect to a predetermined reference surface based on a detection signal of the light receiving element, A first light blocking member having a slit-shaped opening group projected on the surface to be inspected is provided in the irradiation optical system, and is the same as the slit-shaped opening group in the first light blocking member in the condensing optical system. Alternatively, a second light-shielding member having a similar slit-shaped opening group is provided at a position conjugate with the surface to be inspected, and the first light-shielding member and the second light-shielding member are reflected by the surface to be inspected. Are arranged in a conjugate positional relationship, and the first
Adjustment means for rotating the light-shielding member and the second light-shielding member around an axis in the incident plane including the optical axes of the irradiation optical system and the condensing optical system are provided, and through the adjusting means, By rotating the first light shielding member and the second light shielding member, with respect to the incident direction on the surface to be inspected along the incident surface including the irradiation optical system and the optical axis of the condensing optical system, A horizontal position detecting device, characterized in that the pitch of the conjugate image of the slit-shaped opening group of the first light-shielding member and the slit-shaped opening group of the second light-shielding member on the test surface is changed. 8. An irradiation optical system for irradiating a test surface of a test object with a parallel light beam from an oblique direction through the irradiation objective lens, and a condenser objective lens for condensing a light beam reflected by the test surface. In a horizontal position detecting device, comprising: a light collecting optical system having a light receiving element for receiving the collected light flux, and detecting an inclination of the surface to be inspected with respect to a predetermined reference surface based on a detection signal of the light receiving element, A first light blocking member having a slit-shaped opening group projected on the surface to be inspected is provided in the irradiation optical system, and is the same as the slit-shaped opening group in the first light blocking member in the condensing optical system. Alternatively, a second light blocking member having a slit-shaped opening group having a similar shape is provided at a position substantially conjugate with the test surface, and the first light blocking member and the second light blocking member are provided on the test surface via reflection. Are arranged in a conjugate positional relationship, and the first
The longitudinal direction of each slit-shaped opening of the slit-shaped opening group of the light-shielding member and the slit-shaped opening group of the second light-shielding member is set perpendicular to the incident surface including the optical axes of the irradiation optical system and the condensing optical system. Further, adjusting means for rotating the first and second light shielding members about an axis perpendicular to the incident surface is provided, and the first light shielding member and the second light shielding member are rotated through the adjusting means. By moving, the irradiation optical system, and the slit-shaped opening group of the first light shielding member with respect to the incident direction on the surface to be detected along the incident surface including the optical axis of the condensing optical system, and A horizontal position detecting device, wherein the pitch of the conjugate image of the slit-shaped opening group of the second light shielding member on the surface to be detected is changed. 9. The slit-shaped opening group of the first light-shielding member and the slit-shaped opening group of the second light-shielding member each have a checkered pattern, and the first checkerboard pattern has a first periodic direction and a second checkered pattern. By making the pitches in the periodic direction different from each other, and rotating the first light-shielding member and the second light-shielding member about axes in the incident plane including the optical axes of the irradiation optical system and the condensing optical system, respectively. , A direction on the surface to be inspected, which is conjugate with the first periodic direction or the second periodic direction of the checkerboard pattern, is defined as an incident surface including the optical axis of the irradiation optical system and the condensing optical system. The horizontal position detecting device according to claim 7, wherein the horizontal position detecting device is set in a direction along the horizontal direction.