# Patent

## Title
Surface position detection apparatus, exposure apparatus, and exposure method

## Abstract

A surface position detection apparatus capable of highly precisely detecting the surface position of a surface to be detected without substantially being affected by relative positional displacement due to a polarization component occurring in a light flux having passed through a reflective surface. In the apparatus, a projection system has a projection side prism member (7) having first reflective surfaces (7b, 7c), and a light receiving system has a light receiving prism member (8) having second reflective surfaces (8b, 8c) arranged in correspondence with the projection side prism member. The surface position detection apparatus further has a member for compensating relative positional displacement due to a polarization component of a light flux having passed through the first and second reflective surfaces.

## Background
TECHNICAL FIELD
The present invention relates to a surface position detection apparatus, an exposure apparatus, and an exposure method. More particularly, the present invention relates to detection of the surface position of a photosensitive substrate in a projection exposure apparatus used to transfer a mask pattern onto the photosensitive substrate in a lithography process for manufacturing a device such as a semiconductor device, a liquid crystal display device, an imaging device, and a thin-film magnetic head.
BACKGROUND ART
A surface position detection apparatus that detects a surface position using diagonal incident light described in Japanese Laid-Open Patent Publication No. 2001-296105 and corresponding U.S. Pat. No. 6,897,462 (Patent Document 1) is known in the art as a surface position detection apparatus optimal for use as a projection exposure apparatus. To improve the detection accuracy of the surface position of a detected surface theoretically, the diagonal incident light type surface position detection apparatus is required to increase (toward 90 degrees) the incidence angle of a light beam that enters the detected surface. To prevent the structure and arrangement of a projection optical system and a condensing optical system of the surface position detection apparatus from being restricted by the detected surface, a prism having a pair of parallel inner reflection surfaces is arranged in an optical path of the projection optical system and in an optical path of the condensing optical system so as to arrange the projection optical system and the condensing optical system distant from the detected surface (refer to FIG. 7 in Patent Document 1).

    Patent Document 1: Japanese Laid-Open Patent Publication No. 2001-296105


DISCLOSURE OF THE INVENTION
Problems that are to be Solved by the Invention
However, in the conventional surface position detection apparatus described in FIG. 7 of Patent Document 1, a light beam reflected totally by the two parallel inner reflection surfaces of the projection side rhombic prism may cause relative displacement of polarization components. As a result, a clear pattern image may not be formed on the detected surface. In the same manner, a light beam reflected totally by the two parallel inner reflection surfaces of the light receiving side rhombic prism may cause relative displacement of polarization components. This may result in a secondary image of the pattern becoming further bluredly.
In an exposure apparatus, when such a conventional surface position detection apparatus is used to detect the surface position of a wafer (photosensitive substrate) of which surface is coated with a resist, the reflectivity of light with a specific polarization component is known to change in accordance with the thickness of the resist layer. Due to the relative displacement of polarization components in the light beam passing through the inner reflection surfaces of rhombic prisms and reflectivity changes caused by the thickness of the resist layer of the photosensitive substrate, detection errors of the surface position of the detected surface are apt to occur in the conventional surface position detection apparatus.
In view of the above problem, it is an object of the present invention to provide a surface position detection apparatus that detects the surface position of a detected surface with high precision without being virtually affected by relative displacement of polarization components in a light beam passing through a reflection surface. It is also an object of the present invention to provide an exposure apparatus, an exposure method, and a device manufacturing method that enable a pattern surface of a mask and an exposed surface of a photosensitive substrate to be aligned with a projection optical system with high precision using a surface position detection apparatus that detects the surface position of a detected surface with high precision.
Solutions for Solving the Problems
To solve the above problem, a first aspect of the present invention provides a surface position detection apparatus including a projection system which projects a light beam in a diagonal direction onto a detected surface and a light receiving system which receives a light beam reflected by the detected surface. The surface position detection apparatus detects a surface position of the detected surface based on an output of the light receiving system. The projection system includes a first reflection surface. The light receiving system includes a second reflection surface. The surface position detection apparatus further includes a displacement offset member which offsets relative displacement of polarization components in a light beam passing through the first reflection surface of the projection system and the second reflection surface of the light receiving system.
A second aspect of the present invention provides a surface position detection apparatus including a projection system which projects a light beam in a diagonal direction onto a detected surface and a light receiving system which receives a light beam reflected by the detected surface. The surface position detection apparatus detects a surface position of the detected surface based on an output of the light receiving system. At least one of the projection system and the light receiving system includes a reflection surface. The surface position detection apparatus further includes a displacement offset member which offsets relative displacement of polarization components in a light beam passing through the reflection surface.
A third aspect of the present invention provides a surface position detection apparatus including a projection system which projects a light beam in a diagonal direction onto a detected surface and a light receiving system which receives a light beam reflected by the detected surface. The surface position detection apparatus detects a surface position of the detected surface based on an output of the light receiving system. The projection system includes a first reflection surface and a projection side depolarizer arranged at a light-emitting side of the first reflection surface. The light receiving system includes a second reflection surface arranged in correspondence with the first reflection surface and a light receiving side depolarizer arranged at a light entering side of the second reflection surface.
A fourth aspect of the present invention provides an exposure apparatus for projecting and exposing a predetermined pattern onto a photosensitive substrate with a projection optical system. The exposure apparatus includes a surface position detection apparatus according to any one of the first to third aspects for detecting a surface position of the predetermined pattern surface or an exposed surface of the photosensitive substrate with respect to the projection optical system as the surface position of the detected surface. An alignment means aligns the predetermined pattern surface or the exposed surface of the photosensitive substrate with the projection optical system based on a detection result of the surface position detection apparatus.
A fifth aspect of the present invention provides an exposure method for projecting and exposing a predetermined pattern onto a photosensitive substrate with a projection optical system. The exposure method includes a detection step of using the surface position detection apparatus according to any one of the first to third aspects to detect a surface position of the predetermined pattern surface or an exposed surface the photosensitive substrate with respect to the projection optical system as the surface position of the detected surface, and an alignment step of aligning the predetermined pattern surface or the exposed surface of the photosensitive substrate with the projection optical system based on a detection result of the detection step.
A sixth aspect of the present invention provides a device manufacturing method including an exposure step of projecting and exposing a predetermined pattern onto a photosensitive substrate with a projection optical system, a detection step of using the surface position detection apparatus according to any one of the first to third aspects to detect a surface position of the predetermined pattern surface or an exposed surface of the photosensitive substrate with respect to the projection optical system as the surface position of the detected surface, an alignment step of aligning the predetermined pattern surface or the exposed surface of the photosensitive substrate with the projection optical system based on a detection result of the detection step, and a development step of developing the photosensitive substrate that has undergone the exposure step.
A seventh aspect of the present invention provides a method for manufacturing a surface position detection apparatus including a projection system, which projects a light beam in a diagonal direction onto a detected surface, and a light receiving system, which receives a light beam reflected by the detected surface. The surface position detection apparatus detects a surface position of the detected surface based on an output of the light receiving system. The method includes the steps of preparing a first reflection surface arranged in the projection system, preparing a second reflection surface arranged in the light receiving system, and offsetting relative displacement of polarization components in a light beam passing through the first reflection surface of the projection system and the second reflection surface of the light receiving system.
An eighth aspect of the present invention provides an adjustment method for a surface position detection apparatus including a projection system, which projects a light beam through a first reflection surface in a diagonal direction onto a detected surface, and a light receiving system, which receives a light beam reflected by the detected surface through a second reflection surface. The surface position detection apparatus detects a surface position of the detected surface based on an output of the light receiving system. The adjustment method includes the steps of preparing a polarizing member for generating an emission light beam having different characteristics in accordance with polarization components of an incident light beam, and using the polarizing member to offset relative displacement of polarization components in a light beam passing through the first reflection surface of the projection system and the second reflection surface of the light receiving system.
Effect of the Invention
A surface position detection apparatus according to a typical aspect of the present invention includes an offset element arranged in a pupil space of a projection system or in a pupil space of a light receiving system to change the travel direction of an emission light beam by a different angle in accordance with the deflection direction of an incident light beam or an offset element arranged in an object space or an image space of a projection system or in an object space or an image space of a light receiving system to shift in parallel the travel direction of an emission light beam by a different distance from the deflection direction of an incident light beam as a displacement offset member for offsetting relative displacement of polarization components in a light beam passing through a reflection surface of at least one of the projection system and the light receiving system. The offset element functions to enable the surface position of a detected surface to be detected with high precision without substantially being affected by relative displacement of polarization components in a light beam passing through the reflection surface or the like.
Further, a surface position detection apparatus according to another aspect of the present invention includes a depolarizer for reducing relative displacement of polarization components in a light beam passing through a reflection surface in a projection system and a reflection surface in a light receiving system. The depolarizer enables the surface position of a detected surface to be detected with high precision without being substantially affected by relative displacement of polarization components of a light beam passing through the reflection surface or the like.
Accordingly, when the surface position detection apparatus of the present invention is applied to detect the surface position of a photosensitive substrate with respect to a projection optical system in an exposure apparatus, the surface position detection apparatus detects the surface position of the detected surface with high precision without being substantially affected by relative displacement of polarization components in a light beam passing through the reflection surface or the like and enables a pattern surface of a mask to be aligned with an exposed surface of the photosensitive substrate relative to the projection optical system with high precision. This enables a device to be manufactured in a satisfactory manner.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram showing the structure of an exposure apparatus including a surface position detection apparatus according to an embodiment of the present invention;
FIG. 2 is a schematic optical path diagram illustrating that a projection optical system and a condensing optical system shown in FIG. 1 are both-side telecentric;
FIG. 3 is a schematic diagram showing the structure between a pair of pentaprisms in the surface position detection apparatus of the present embodiment;
FIG. 4 is a perspective diagram showing a detected surface Wa on which a primary image of a lattice pattern 3a is formed;
FIG. 5 is a schematic diagram showing the structure of a light receiving slit S having five rectangular open portions Sa1 to Sa5 elongated in the X-direction;
FIG. 6 shows a light receiving surface 14a of a light receiving unit 14 on which five silicon photodiodes PD1 to PD5 are arranged to optically correspond to the open portions Sa1 to Sa5 of the light receiving slit S;
FIG. 7 is a diagram illustrating the structure and operation of a displacement offset member arranged in the surface position detection apparatus of the present embodiment;
FIG. 8 is a diagram illustrating the main structure and operation of a first modification of the present embodiment;
FIG. 9 is a diagram illustrating the main structure and operation of a second modification of the present embodiment;
FIG. 10 is a diagram illustrating the main structure and operation of a third modification of the present embodiment;
FIG. 11 is a flowchart illustrating the procedures for forming a semiconductor device serving as a microdevice; and
FIG. 12 is a flowchart illustrating the procedures for forming a liquid crystal display device serving as a microdevice.



DESCRIPTION OF REFERENCE NUMERALS


    1 light source
    2 condenser lens
    3 deflection prism
    4, 5 projection optical system
    6, 9 pentaprism
    7, 8 rhombic prism
    10, 11 condensing optical system
    12 oscillating mirror
    perspective correction prism
    14a, 14b relay optical system
    15 light receiving unit
    16 mirror driving unit
    17 position detection unit
    18 correction amount calculation unit
    19 Nomarski prism (first offset element)
    20 beam displacer (second offset element)
    21 wafer holder
    22 holder supporting mechanism
    23 holder driving unit
    31 half-wave plate (phase member)
    32, 33 depolarizer
    IL illumination system
    R reticle
    RH reticle holder
    PL projection optical system
    W wafer


BEST MODE FOR CARRYING OUT THE INVENTION
One embodiment of the present invention will now be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing the structure of an exposure apparatus that includes a surface position detection apparatus according to the embodiment of the present invention. FIG. 2 is an optical path diagram showing that a projection optical system and a condensing optical system in FIG. 1 are both-side telecentric. FIG. 3 is a schematic diagram showing the structure between a pair of pentaprisms in the surface position detection apparatus according to the embodiment of the present embodiment.
To make the drawings clear, FIGS. 1 and 2 do not show the structure between the pentaprisms 6 and 9. In FIG. 1, a the Z-axis is set to be parallel to an optical axis AX of a projection optical system PL, a Y-axis is set to be parallel to the plane of FIG. 1 within a plane orthogonal to the optical axis AX, and an X-axis is set to be orthogonal to the plane of FIG. 1. In the present embodiment, the surface position detection apparatus of the present invention is used to detect the surface position of a photosensitive substrate in a projection exposure apparatus.
The shown exposure apparatus includes an illumination system IL for illuminating a reticle R used as a mask, on which a predetermined pattern is formed, with illumination light (exposure light) emitted from an exposure light source (not shown). A reticle holder RH supports the reticle R on a reticle stage (not shown) in a manner that the reticle R is parallel to the XY plane. The reticle stage is movable in a two-dimensional manner along a reticle surface (that is, the XY plane) when driven by a drive system (not shown). The coordinates representing the position of the reticle stage are measured by a reticle interferometer (not shown) to control the position of the reticle stage.
Light from the pattern of the reticle R enters the projection optical system PL, which forms a pattern image of the reticle R on a surface (exposed surface) Wa of a wafer W, which is a photosensitive substrate. The wafer W is held on a wafer holder 21, and the wafer holder 21 is supported by a holder supporting mechanism 22. The holder supporting mechanism 22 supports the wafer holder 21 with three support points 22a to 22c (only two support points 22a and 22b are shown in FIG. 1), which are movable in upward and downward directions (Z-direction).
A holder driving unit 23 controls the upward and downward movement of the support points 22a to 22c of the holder supporting mechanism 22 to level and move the wafer holder 21 in the Z-direction (focusing direction). This consequently levels and moves the wafer W in the Z-direction. The wafer holder 21 and the holder supporting mechanism 22 are further supported on a wafer stage (not shown). The wafer stage is movable in a two-dimensional manner along a wafer surface (i.e., the XY plane) when driven by a drive mechanism (not shown) and is also rotatable about the Z-axis. The coordinates representing the position of the wafer stage are measured by a wafer interferometer (not shown) to control the position of the wafer stage.
To transfer a circuit pattern formed on the pattern surface of the reticle R onto exposure fields of the exposed surface Wa of the wafer W in a satisfactory manner, each exposure field in the exposed surface Wa must be positioned during exposure within the range of the focal depth of the projection optical system PL that is centered about an imaging plane of the projection optical system PL. To position an exposure field, the surface positions of points in the present exposure field, that is, surface positions along the optical axis AX of the projection optical system PL may first be accurately detected. Then, the wafer holder 21 may be leveled and moved in the Z-direction to consequently level and move the wafer W in the Z-direction so that the exposed surface Wa falls within the range of the focal depth of the projection optical system PL.
Accordingly, the projection exposure apparatus of the present embodiment includes a surface position detection apparatus for detecting the surface position of each point within the present exposure field of the exposed surface Wa. Referring to FIG. 1, the surface position detection apparatus of the present embodiment includes a light source 1 for supplying detection light. The surface Wa of the wafer W, which serves as the detected surface, is normally coated with a thin film of resist or the like. To reduce the influence of interference between light and the thin film, it is preferable that the light source 1 be a white light source having a wide wavelength range (e.g., a halogen lamp that supplies illumination light having a wavelength range of 600 to 900 nm or a xenon light source that supplies illumination light in a similar band as the halogen lamp). A light emitting diode that supplies light in a wavelength band in which resist has weak photosensitivity may also be used as the light source 1.
A divergent beam from the light source 1 is converted to a generally parallel beam by a condenser lens 2 and then enters a deflection prism 3. The deflection prism 3 deflects the generally parallel light beam from the condenser lens 2 in the −Z direction by refracting the light beam. A transmissive lattice pattern 3a is formed at a light-emitting side of the deflection prism 3. The transmissive lattice pattern 3a is formed by alternately arranging elongate light transmitting portions extending in the X-direction and elongated light shielding portions extending in the X-direction at regular intervals. Alternatively, a reflective diffraction grating having projections and recesses or a reflective lattice pattern formed by alternately forming reflective portions and nonreflective portions may be used in lieu of the transmissive lattice pattern.
Light passing through the transmissive lattice pattern 3a enters a projection optical system (4 and 5), which is arranged along an optical axis AX1 that is parallel to the optical axis AX of the projection optical system. The projection optical system (4 and 5) is formed by a projection condenser lens 4 and a projection optical lens 5. A light beam passing through the projection optical system (4 and 5) enters a pentaprism 6. The pentaprism 6 is a pentagonal deflection prism with a longitudinal axis extending in the X-direction. The pentaprism 6 has a first transmissive surface 6a for transmitting incident light along the optical axis AX1 without refracting the incident light. The first transmissive surface 6a is set to be orthogonal to the optical axis AX1.
Light passing through the first transmissive surface 6a and propagating inside the pentaprism 6 along the optical axis AX1 is reflected by a first reflection surface 6b and then reflected again by a second reflection surface 6c along an optical axis AX2. The light reflected by the second reflection surface 6c and propagating inside the pentaprism 6 along the optical axis AX2 passes through a second transmissive surface 6d without being refracted by the second transmissive surface 6d. The second transmissive surface 6d is set to be orthogonal to the optical axis AX2. The pentaprism 6 is formed from an optical material having low thermal expansion and low divergent properties, such as quartz glass. A reflection film made of, for example, aluminum or silver is formed on the first reflection surface 6b and the second reflection surface 6c. 
Light entering the pentaprism 6 in the −Z direction along the optical axis AX1 is significantly deflected by the pentaprism 6 and guided along the optical axis AX2 toward the detected surface Wa. The direction of the optical axis AX2 is set so that the incidence angle on the detected surface Wa is sufficiently large. This consequently sets the deflection angle at which the light is deflected by the pentaprism 6. More specifically, as shown in FIG. 3, a light beam emitted from the pentaprism 6 along the optical axis AX2 enters a projection side rhombic prism 7.
The rhombic prism 7 is a quadratic prism having a rhombic cross-section. The longitudinal axis of the rhombic prism 7 extends in the X-direction in the same manner as the pentaprism 6. In the rhombic prism 7, light passing through a first transmissive surface 7a, which is orthogonal to the optical axis AX2, is sequentially reflected by two parallel reflection surfaces 7b and 7c and then passes through a second transmissive surface 7d, which is parallel to the first transmissive surface 7a. The light is then emitted from the rhombic prism 7 along an optical axis AX21 that is parallel to the optical axis AX2. The light beam emitted from the rhombic prism 7 along the optical axis AX21 enters the detected surface Wa.
In a state in which the detected surface Wa coincides with an imaging plane of the projection optical system PL, the projection optical system (4 and 5) is formed so that the surface on which the lattice pattern 3a is formed (that is, the light emitting surface of the deflection prism 3) and the detected surface Wa are conjugate to each other. Also, the surface on which the lattice pattern 3a is formed and the detected surface Wa satisfy the Scheimpflug condition with respect to the projection optical system (4 and 5). As a result, light from the lattice pattern 3a is precisely focused over the entire pattern image formation surface of the detected surface Wa with the projection optical system (4 and 5).
The optical path indicated by a broken line in FIG. 2, shows that the projection optical system (4 and 5), which is formed by the projection condenser lens 4 and the projection objective lens 5, is a both-side telecentric optical system. Accordingly, points on the formation surface of the lattice pattern 3a and the detected surface Wa that are conjugate to each other have the same magnification over the entire surfaces. In this manner, referring to FIG. 4, a primary image of the lattice pattern 3a is accurately formed over the entire detected surface Wa.
Referring again to FIG. 1, a light beam reflected by the detected surface Wa along an optical axis AX31, which is symmetric to the optical axis AX21 with respect to the optical axis AX of the projection optical system PL, enters a light receiving side rhombic prism 8. The rhombic prism 8 is a quadratic prism having a longitudinal axis extending in the X-direction and having a rhombic cross-section like the rhombic prism 7. In the rhombic prism 8, light passing through a first transmissive surface 8a, which is orthogonal to the optical axis AX31, is sequentially reflected by two parallel reflection surfaces 8b and 8c and then passes through a second transmissive surface 8d, which is parallel to the first transmissive surface 8a. The light is emitted from the rhombic prism 8 along an optical axis AX3, which is parallel to the optical axis AX31.
The light emitted from the rhombic prism 8 along the optical axis AX3 enters a condensing optical system (10 and 11) after passing through a pentaprism 9, which has the same structure as the pentaprism 6 described above. More specifically, light reflected by the detected surface Wa enters the pentaprism 9 along the optical axis AX3, which is symmetric to the optical axis AX2 with respect to the optical axis AX of the projection optical system PL. In the pentaprism 9, light passing through a first transmissive surface 9a, which is orthogonal to the optical axis AX3, is sequentially reflected by a first reflection surface 9b and a second reflection surface 9c and then reaches a second transmissive surface 9d along an optical axis AX4 extending in the Z-direction. Light passing through the second transmissive surface 9d, which is orthogonal to the optical axis AX4, enters the condensing optical system (10 and 11) in the +Z direction along the optical axis AX4.
The condensing optical system (10 and 11) is formed by a light receiving objective lens 10 and a light receiving condenser lens 11. An oscillating mirror 12, which serves as a scanning means, is arranged in an optical path formed between the light receiving objective lens 10 and the light receiving condenser lens 11. Thus, light entering the light receiving objective lens 10 along the optical axis AX4 is deflected by the oscillating mirror 12 and reaches the light receiving condenser lens 11 along an optical axis AX5. In the present embodiment, the oscillating mirror 12 is generally arranged at a pupil plane of the condensing optical system (10 and 11). However, the present invention is not limited in such a manner and the oscillating mirror 12 may be arranged at any position in the optical path formed between the detected surface Wa and a perspective correction prism 13, which will be described later, or at an optical path formed between the detected surface Wa and the deflection prism 3.
Light passing through the condensing optical system (10 and 11) enters the perspective correction prism 13, which has the same structure as the deflection prism 3. In a state in which the detected surface Wa coincides with the imaging plane of the projection optical system PL, the condensing optical system (10 and 11) is formed so that the detected surface Wa and a light entering surface 13a of the perspective correction prism 13 are conjugate to each other. With this structure, a secondary image of the lattice pattern 3a is formed on the light entering surface 13a of the perspective correction prism 13.
The light entering surface 13a of the perspective correction prism 13 includes a light receiving slit S, which serves as a light shielding means. As shown in FIG. 5, the light receiving slit S may include, for example, five open portions Sa1 to Sa5, each of which has an elongated rectangular shape extending in the X-direction. Light reflected from the detected surface Wa and passing through the condensing optical system (10 and 11) enters the perspective correction prism 13 through the open portions Sa1 to Sa5 of the light receiving slit S.
The number of the open portions Sa of the light receiving slit S corresponds to the number of detection points on the detected surface Wa. FIG. 4 shows the detected surface Wa on which a primary image of the lattice pattern 3a is formed. In this state, detection points (detection regions) Da1 to Da5 on the detected surface Wa optically correspond to the five open portions Sa1 to Sa5 of the light receiving slit S shown in FIG. 5. The number of detection points on the detected surface Wa may be increased by just increasing the number of open portions Sa. An increase in the number of detection points does not make the structure complicated.
The imaging plane of the projection optical system PL and the light entering surface 13a of the perspective correction prism 13 satisfy the Scheimpflug condition with respect to the condensing optical system (10 and 11). Accordingly, in a state in which the detected surface Wa and the imaging plane coincide with each other, light from the lattice pattern 3a is accurately focused again over the entire pattern image formation surface on the prism light entering surface 13a by the condensing optical system (10 and 11).
As shown by the optical path indicated by a broken line in FIG. 2, the condensing optical system (10 and 11) is a two-side telecentric optical system. Accordingly, points on the detected surface Wa and conjugate points on the prism light entering surface 13a have the same magnification over the entire surface. Thus, a secondary image of the lattice pattern 3a is accurately formed over the entire light entering surface 13a of the perspective correction prism 13.
When a light receiving surface is located at the light entering surface 13a of the perspective correction prism 13, an incidence angle θ of a light beam on the detected surface Wa is large. Thus, the incidence angle of the light beam on the light receiving surface increases accordingly. In this case, if, for example, a silicon photodiode is arranged on the light receiving surface, a light beam enters the silicon photodiode at a large incidence angle. This increases the surface reflection of the silicon photodiode and causes vignetting. This may result in a significant decrease of the light receiving amount.
To prevent the light receiving amount from decreasing due to the incidence angle of a light beam on the light receiving surface, in the present embodiment, the light entering surface 13a of the perspective correction prism 13, which serves as a deflection optical system, is arranged on a surface conjugate to the detected surface Wa with respect to the condensing optical system (10 and 11). As a result, a light beam incident on the light entering surface 13a of the perspective correction prism 13 along the optical axis AX5 with the condensing optical system (10 and 11) is deflected at a refraction angle that is the same as the vertex angle of the perspective correction prism 13 (angle formed by the light receiving surface and the light emitting surface) and then emitted from the light emitting surface 13b along optical axis AX6. The light emitting surface 13b is set to be orthogonal to the optical axis AX6.
The light beam emitted from the light emitting surface 13b of the perspective correction prism 13 along the optical axis AX6 enters a relay optical system (14a and 14b), which is formed by two lenses 14a and 14b. Light passing through the relay optical system (14a and 14b) forms an image conjugate to the secondary image of the lattice pattern 3a formed on the light entering surface 13a of the perspective correction prism 13 and the open portions Sa1 to Sa5 of the light receiving slit S on the light receiving surface 15a of the light receiving unit 15. As shown in FIG. 6, five silicon photodiodes PD1 to PD5 formed on the light receiving surface 15a optically correspond to the open portions Sa1 to Sa5 of the light receiving slit S. Two-dimensional CCDs (charge-coupled device) or photomultipliers may be used in lieu of the silicon photodiodes.
As described above, in the present embodiment, the perspective correction prism 13 serving as a deflection optical system is used. This sufficiently decreases the incidence angle of the light beam entering the light receiving surface 15a and prevents the light receiving amount from being decreased by the incidence angle of the light beam on the light receiving surface 15a. It is preferable that the relay optical system (14a and 14b) be a both-side telecentric optical system as shown in FIG. 2. It is further preferable that the light entering surface 13a and the light receiving surface 15a of the perspective correction prism 13 satisfy the Scheimpflug condition with respect to the relay optical system (14a and 14b).
As described above, the light entering surface 13a of the perspective correction prism 13 includes the light receiving slit S, which has the five open portions Sa1 to Sa5. Thus, the light receiving slit S partially shields light from the secondary image of the lattice pattern 3a formed on the light entering surface 13a. In other words, only the light beam from the secondary image of the lattice pattern 3a that is formed in the regions of the open portions Sa1 to Sa5 of the light receiving slit S pass through the perspective correction prism 13 and the relay optical system (14a and 14b) and reach the light receiving surface 15a. 
In this manner, referring to FIG. 6, images of the open portions Sa1 to Sa5 of the light receiving slit S, that is, slit images SL1 to SL5, are formed on the silicon photodiodes PD1 to PD5, which are arranged on the light receiving surface 15a of the light receiving unit 15. The slit images SL1 to SL5 are formed inside the rectangular light receiving regions of the silicon photodiodes PD1 to PD5.
When the detected surface Wa is moved upward and downward in the Z-direction along the optical axis AX of the projection optical system PL, the secondary image of the lattice pattern 3a formed on the light entering surface 13a of the perspective correction prism 13 is displaced laterally in the pitch direction of the pattern in accordance with the upward and downward movement of the detected surface Wa. In the present embodiment, for example, the amount of lateral displacement of the secondary image of the lattice pattern 3a may be detected based on the principle of a photoelectric microscope disclosed in Japanese Laid-Open Patent Publication No. 6-97045 by the same applicant as the present application. The surface position of the detected surface Wa along the optical axis AX of the projection optical system PL may be detected based on the detected lateral displacement amount.
A mirror driving unit 16 drives the oscillating mirror 12. A position detection unit 17 synchronously detects the waveform of detection signals from the silicon photodiodes PD1 to PD5 based on an alternating current signal from the mirror driving unit 16. A correction amount calculation unit 18 calculates the amount of inclination correction and the amount of correction in the Z-direction required to position the detected surface Wa within the range of the focal depth of the projection optical system PL. The holder driving unit 23 drives the holder supporting mechanism 22 based on the inclination correction amount and the Z-direction correction amount, levels the wafer holder 21, and moves the wafer holder 21 in the Z-direction. Such operations of the mirror driving unit 16, the position detection unit 17, the correction amount calculation unit 18, and the holder driving unit 23 are identical to the operations performed by the apparatuses disclosed in Japanese Laid-Open Patent Publication No. 2001-296105 and its corresponding U.S. Pat. No. 6,897,462 by the same applicant as the present application and will not be described in the present embodiment.
The Scheimpflug condition, the structure and operation of the deflection prism 3 and the perspective correction prism 13, specific applications of the principle of the photoelectric microscope and the like are described in detail in U.S. Pat. No. 5,633,721. The structure and operation of the pentaprisms 6 and 9 are described in detail in Japanese Laid-Open Patent Publication No. 2001-296105 and its corresponding U.S. Pat. No. 6,897,462. Either one or both of the pentaprisms 6 and 9 may be eliminated. U.S. Pat. No. 5,633,721 and U.S. Pat. No. 6,897,462 are incorporated herein by reference.
In the present embodiment, the pentaprism 6 is arranged in the optical path formed between the projection optical system (4 and 5) and the detected surface Wa, and the pentaprism 9 is arranged in the optical path formed between the condensing optical system (10 and 11) and the detected surface Wa. The optical path of a light beam incident on the detected surface Wa and the optical path of a light beam reflected by the detected surface Wa are deflected by a significant amount by the pentaprisms 6 and 9 so as to arrange the projection optical system (4 and 5) and the condensing optical system (10 and 11) at positions sufficiently distant from the detected surface Wa. As a result, the structure and arrangement of the projection optical system (4 and 5) and the condensing optical system (10 and 11) are substantially not restricted by the detected surface Wa.
In the present embodiment, the rhombic prism 7 is arranged in the optical path formed between the pentaprism 6 and the detected surface Wa, and the rhombic prism 8 is arranged in the optical path formed between the pentaprism 9 and the detected surface Wa. Thus, the optical path of a light beam incident on the detected surface Wa and the optical path of a light beam reflected from the detected surface W are each shifted in parallel by the rhombic prisms 7 and 8. As a result, the pentaprisms 6 and 9 are arranged at positions distant from the detected surface Wa. The structure and arrangement of the pentaprisms 6 and 9 and their supporting members are substantially not restricted by the detected surface Wa.
The surface position detection apparatus of the present embodiment includes the projection side prism member, or the rhombic prism 7, and the light receiving side prism member, or the rhombic prism 8. The rhombic prism 7 includes the two inner reflection surfaces (7b and 7c) arranged in the optical path of the projection system to shift in parallel the optical path of an incident light beam. The rhombic prism 8 includes the two inner reflection surfaces (8b and 8c) arranged in correspondence with the projection side prism member 7 in the optical path of the light receiving system to shift in parallel the optical path of an incident light beam from the detected surface Wa. In this case, relative displacement of polarization components occurs in a light beam totally reflected by the two parallel inner reflection surfaces (7b and 7c) of the projection side rhombic prism 7. As a result, a clear pattern image is not formed on the detected surface Wa.
More specifically, in a light beam reaching the detected surface Wa, relative displacement occurs between p-polarized light and s-polarized light with respect to the detected surface Wa. Consequently, a pattern image formed on the detected surface Wa by the p-polarized light and a pattern image formed on the detected surface Wa by the s-polarized light are displaced relative to each other. In the same manner, relative displacement of polarization components occurs in a light beam reflected by the detected surface Wa and totally reflected by the two parallel inner reflection surfaces (8b and 8c) of the light receiving side rhombic prism 8. As a result, a secondary image of a pattern formed on the light entering surface 13a of the perspective correction prism 13 will becomes further unclear.
In other words, the total reflection on the inner reflection surfaces (8b and 8c) of the light receiving side rhombic prism 8 accentuates relative displacement that occurs between a secondary image of a pattern formed on the light entering surface 13a by the p-polarized light and a secondary image of the pattern formed on the light entering surface 13a by the s-polarized light.
The surface position detection apparatus of the present embodiment is used to detect the surface position of a wafer W that has various different surface states during a semiconductor exposure process (e.g., structures on the wafer W being formed from various materials or the wafer W having various structures (multi-layer structure)). The wafer surface is normally coated with a resist. When the surface state of such a wafer W has variations (e.g., when the thicknesses of a layer forming the wafer surface has variations or properties such as the purity of a material forming the wafer surface layer has variations) or the resist thickness has variations, the reflectivity of the wafer surface to light having specific polarization components (e.g., p-polarized light or s-polarized light) changes in accordance with such variations.
If no countermeasures are taken against such a problem, the surface position detection apparatus of the present embodiment would have a tendency of producing detection errors of the surface position of the detected surface Wa due to the relative displacement of polarization components in a light beam passing through the inner reflection surfaces (7b and 7c or 8b and 8c) of the rhombic prisms (7 and 8) and the reflectivity changes of specific polarization components caused by the surface state variations of the wafer W or the resist thickness variations of the wafer W.
In recent years, miniaturization of projection exposure patterns has results in a demand for a wafer surface having higher flatness and higher precision for surface position detection. Further, an exposure apparatus using an ArF excimer laser light source tends to have a thinner resist coating on the wafer surface. For such an exposure apparatus, surface position detection errors caused by surface state variations or resist thickness variations described above cannot be ignored.
To cope with this problem, the surface position detection apparatus of the present embodiment includes a displacement offset member for offsetting relative displacement of polarization components in a light beam passing through the inner reflection surfaces (7b and 7c) of the projection side prism member (rhombic prism) 7 and the inner reflection surfaces (8b and 8c) of the light receiving side prism member (rhombic prism) 8.
FIG. 7 is a diagram describing the structure and effects of the displacement offset member included in the surface position detection apparatus of the present embodiment. For the sake of brevity, FIG. 7 shows an optical path extending from the detected surface Wa to the light entering surface 13a of the perspective correction prism 13 along the linear optical axis AX. The oscillating mirror 12 is not shown. The same applies to FIG. 8, which is related to FIG. 7. Referring to FIG. 7, the surface position detection apparatus of the present embodiment includes a Nomarski prism 19, which serves as the displacement offset member, at a pupil position of the condensing optical system (10 and 11) in the optical path between the light receiving objective lens 10 and the light receiving condenser lens 11 or near the pupil position.
The Nomarski prism 19 is an optical element (first offset element) functioning to change the travel direction of an emission light beam by a different angle depending on the polarization direction of an incident light beam. More specifically, as shown in FIG. 7, the total reflection on the inner reflection surfaces (7b and 7c or 8b and 8c) of the rhombic prisms (7 and 8) causes relative displacement between the p-polarized light and the s-polarized light, and representative p-polarized light 71a and representative s-polarized light 72a, which are inclined at different angles with respect to the optical axis AX, enter the Nomarski prism 19 at substantially a single point on the optical axis AX. Based on its function for changing the travel direction of an emission light beam by the different angle from the polarization direction of an incident light beam, the Nomarski prism 19 converts the incident p-polarized light 71a, which is inclined to the optical axis AX, into p-polarized emission light 71b that substantially travels along the optical axis AX and also converts the incident s-polarized light 72a, which is inclined with respect to the optical axis AX, into s-polarized emission light 72b that travels substantially along the optical axis AX.
In this manner, the relative displacement of the p-polarized light and the s-polarized light caused by the total reflection on the inner reflection surfaces (7b and 7c or 8b and 8c) of the rhombic prisms (7 and 8) is offset by the Nomarski prism 19. As a result, the p-polarized emission light 71b and the s-polarized emission light 72b from the Nomarski prism 19 travel along substantially the same path and reach substantially a single point on the light entering surface 13a of the perspective correction prism 13. As a result, the surface position detection apparatus of the present embodiment forms a clear secondary image of the pattern on the light entering surface 13a of the perspective correction prism 13 with the Nomarski prism 19, which serves as the displacement offset member, and consequently detects the surface position of the detected surface Wa with high precision without being virtually affected by relative displacement of polarization components in a light beam passing through the inner reflection surfaces (7b and 7c or 8b and 8c) of the prism members (rhombic prisms) 7 and 8. Without the Nomarski prism 19, the p-polarized emission light (indicated by a broken line in the drawing) 71c and the s-polarized emission light (indicated by a broken line in the drawing) 72c from the Nomarski prism 19 would travel along different paths and reach different positions on the light entering surface 13a of the perspective correction prism 13. In such a case, a sharp secondary image of the pattern would not be formed on the light entering surface 13a of the perspective correction prism 13.
In the above description, the Nomarski prism is used as the displacement offset member that functions to change the travel direction of an emission light beam by the different angle from the polarization direction of an incident light beam. However, the present invention is not limited to such a structure. For example, a Wollaston prism may be used in lieu of a Nomarski prism. Further, when a Nomarski prism or a Wollaston prism is used as the displacement correction member, a direct-vision prism may be arranged near the Nomarski prism or the Wollaston Prism to correct color shifting.
For the sake of simplicity, a wedge prism plate formed from a birefringent crystal material, such as calcite, quartz, yttrium orthovanadate crystal, or rutile crystal, may be used in lieu of the prism to cause an incident ordinary light beam and an incident extraordinary light beam to travel at different angles. In this case, for example, the crystal optical axis and the wedge are oriented to cause the incident ordinary light beam and the incident extraordinary light beam to travel at different angles. Alternatively, a structure in which such a wedge prism plate and a wedge prism plate made of normal optical glass are bonded together may be used. In such a case, the same advantages are produced as when the above Nomarski prism is used.
In the above description, the Nomarski prism 19 is arranged at or near the pupil position of the condensing optical system (10 and 11) in the optical path formed between the light receiving objective lens 10 and the condensing objective lens 11. However, the present invention is not limited to such a structure and the Nomarski prism may be arranged normally in a pupil space of the projection system or a pupil space of the light receiving system. When arranged in the pupil space of a projection system, the Nomarski prism may be located at or near the pupil position of the projection optical system (4 and 5) in the optical path formed between the projection condenser lens 4 and the projection objective lens 5. Further, when the Wollaston prism us used as the displacement offset member, the Wollaston prism may be arranged in the pupil space of the projection system or the pupil space of the light receiving system. However, when the displacement offset member, such as the Nomarski prism or the Wollaston prism, is added to an existing apparatus to improve performance, it would be easier to arrange the displacement offset member in the pupil space of the light receiving system than in the pupil space of the projection system.
In the above description, an optical element (such as the Nomarski prism and the Wollaston prism) that functions to change the travel direction of an emission light beam by a different angle from the polarization direction of an incident light beam is used as the displacement offset member. However, the present invention is not limited to such a structure. As shown in FIG. 8, a modification may be made so that an optical element shifts in parallel the travel direction of an emission light beam by a different distance from the polarization direction of an incident light beam (second offset element). Alternatively, as shown in FIG. 9, a modification may be made so that a phase member used as the displacement offset member is arranged in an optical path formed between the projection prism member (rhombic prism) 7 and the light receiving side prism member (rhombic prism 8) to change the polarization direction of an incident light beam.
Referring to FIG. 8, a beam displacer 20, which functions as the displacement offset member of the first modification, is arranged in an optical path between the light receiving condenser lens 11 and the perspective correction prism 13. The beam displacer 20 may be formed of, for example, a birefringent crystal material, such as calcite, quartz, yttrium orthovanadate (YVO4) crystal, or rutile (TiO2) crystal, and functions to emit an incident ordinary light beam and an incident extraordinary light beam in a manner parallel to each other. In other words, the beam displacer 20 functions to shift in parallel the travel direction of an emission light beam by a different distance from an incident light beam.
More specifically, referring to FIG. 8, relative displacement occurs between the p-polarized light and s-polarized light due to the influence of the total reflection on the inner reflection surfaces (7b and 7c or 8b and 8c) of the rhombic prisms (7 and 8). The representative p-polarized light 73a and s-polarized light 74a travel along different paths that are substantially parallel to the optical axis AX and enter the beam displacer 20. Based on the function for shifting in parallel the travel direction of an emission light beam by a different distance from the incident light beam, the beam displacer 20 transmits the incident p-polarized light 73a and converts the p-polarized light 73a to p-polarized emission light 73b, which travels along a path that extends substantially parallel to the optical axis AX, and also shifts in parallel the incident s-polarized light 74a to convert the s-polarized light 74a to s-polarized emission light 74b that travels substantially along the same path as the p-polarized emission light 73b. 
In this manner, the beam displacer 20 functions to offset the relative displacement of the p-polarized light and the s-polarized light caused by the total reflection at the inner reflection surfaces (7b and 7c or 8b and 8c) of the rhombic prisms (7 and 8). As a result, the p-polarized light 73b and the s-polarized light 74b emitted from the beam displacer 20 travel substantially along the same path and reach substantially a single point on the light entering surface 13a of the perspective correction prism 13. As a result, in the first modification example shown in FIG. 8, the beam displacer 20, which functions as the displacement offset member, also enables a sharp secondary image of a pattern to be formed on the light entering surface 13a of the perspective correction prism 13 and consequently enables the surface position of the detected surface Wa to be detected with high precision. Without the beam displacer 20, the p-polarized light 73c and the s-polarized light 74c (indicated by a broken line in the drawing) emitted from the beam displacer 20 would travel along different paths and reach different positions on the light entering surface 13a of the perspective correction prism 13. In such a case, a sharp secondary image of the pattern is not formed on the light entering surface 13a of the perspective correction prism 13.
In the first modification, the beam displacer 20 is arranged in the optical path formed between the light receiving condenser lens 11 and the perspective correction prism 13. In other words, the beam displacer 20 is arranged in an image space of the light receiving system. However, the present invention is not limited to such a structure, and the beam displacer may generally be arranged in the optical path between the deflection prism 3 and the perspective correction prism 13, that is, in an object space or an image space of the projection system or an object space or an image space of the light receiving system. However, when the displacement offset member, such as the beam displacer, is added to an existing apparatus to improve performance, it is preferable that the displacement offset member be arranged in the image space of the light receiving system in order to facilitate optical adjustment.
Referring to FIG. 9, a half-wave plate 31, which functions as a displacement offset member in a second modification, is arranged near the light receiving rhombic prism 8 in an optical path formed between the two prism members (rhombic prisms) 7 and 8. The half-wave plate 31, which is a phase member for changing the polarization direction of an incident light beam, functions to convert incident p-polarized light to s-polarized light and emit the s-polarized light and convert incident s-polarized light to p-polarized light and emit the p-polarized light.
In this case, p-polarized light passing through the inner reflection surfaces (7b and 7c) of the projection side rhombic prism 7 is converted to s-polarized light by the half-wave plate 31 and passes through the inner reflection surfaces (8b and 8c) of the light receiving side rhombic prism 8. In the same manner, s-polarized light passing through the inner reflection surfaces (7b and 7c) of the projection side rhombic prism 7 is converted to p-polarized light by the half-wave plate 31 and passes through the inner reflection surfaces (8b and 8c) of the light receiving side rhombic prism 8. In the second modification, displacement of the p-polarized light caused by the total reflection on the inner reflection surfaces (7b and 7c) of the projection side rhombic prism 7 is offset by displacement of the s-polarized light caused by the total reflection on the inner reflection surfaces (8b and 8c) of the light receiving side rhombic prism 8. Displacement of the s-polarized light caused by the total reflection on the inner reflection surfaces (7b and 7c) of the projection side rhombic prism 7 is offset by displacement of the p-polarized light caused by the total reflection on the inner reflection surfaces (8b and 8c) of the light receiving side rhombic prism 8. As a result, in the second modification shown in FIG. 9, the half-wave plate 31, which functions as the displacement offset member, enables a clear secondary image of the pattern to be formed on the light entering surface 13a of the perspective correction prism 13 and consequently enables the surface position of the detected surface Wa to be detected with high precision.
In the second modification described above, the half-wave plate 31 is used as the phase member arranged in the optical path between the projection side prism member 7 and the light receiving side prism, member 8 to change the polarization direction of an incident light beam. However, the present invention is not limited to such a structure and a Faraday rotator (Faraday optical rotator) may be used as the phase member in lieu of the half-wave plate 31.
Further, in the second modification described above, the half-wave plate 31, which functions as the phase member, is arranged near the light receiving side rhombic prism 8 in the optical path between the pair of prism members (rhombic prisms) 7 and 8. However, the present invention is not limited to such a structure, and a phase member, such as a half-wave plate, may be arranged at an appropriate position at the projection side or the light receiving side in the optical path between the pair of prism members (rhombic prisms) 7 and 8.
Also, in the above embodiment and modifications, displacement offset members (19, 20, and 31), which offset the relative displacement of polarization components in a light beam passing through the inner reflection surfaces of the projection side prism member 7 and the inner reflection surfaces of the light receiving side prism member 8, are used. However, the present invention is not limited to such a structure. As shown in FIG. 10, a depolarizer for randomly changing the polarization direction of an incident light beam may be used as a third modification.
In the third modification shown in FIG. 10, a projection side depolarizer 32 is arranged near a light-emitting side of a projection side prism member (rhombic prism) 7 and a light receiving side depolarizer 33 is arranged near a light entering side of a light receiving side prism member (rhombic prism) 8. The depolarizers 32 and 33 may be, for example, deflection prisms (wedge-shaped prisms) formed from a birefringent crystal material, such as quartz crystal or magnesium fluoride, and function to substantially depolarize incident p-polarized light and incident s-polarized light.
In this case, the polarization direction of light before entering the wafer W and after exiting the wafer W is randomized by the two depolarizers 32 and 33. This reduces the influence of changes in the reflectivity of the p-polarized light and s-polarized light caused by the resist layer formed on the wafer W. As a result, in the third modification, the surface position of the detected surface Wa is detected with high precision without being substantially affected by relative displacement of polarization components in a light beam passing through the inner reflection surfaces (7b and 7c or 8b and 8c) of the prism members (rhombic prisms) 7 and 8.
In the present embodiment, a reflection film, such as a metal film made of aluminum, may be formed on an outer surface of each of the inner reflection surfaces (7b and 7c or 8b and 8c) of the projection side rhombic prism 7 and the light receiving side rhombic prism 8. This structure prevents the total reflection phenomenon of the rhombic prisms 7 and 8 and substantially prevents relative displacement of polarization components in a light beam passing through the rhombic prisms 7 and 8.
In the present embodiment, a projection side second rhombic prism may be arranged adjacent to the projection side rhombic prism 7, and a light receiving side second rhombic prism may be arranged adjacent to the light receiving side rhombic prism 8. With this structure, the influence of the total reflection of the inner reflection surfaces (7b and 7c) in the projection side rhombic prism 7 is offset by the influence of the total reflection of the inner reflection surfaces in the projection side second rhombic prism. Further, the influence of the total reflection of the inner reflection surfaces (8b and 8c) in the light receiving side rhombic prism 8 is offset by the influence of the total reflection of the inner reflection surfaces in the light receiving side second rhombic prism. This substantially prevents relative displacement caused by polarization components of a light beam passing through the rhombic prisms 7 and 8.
Further, in the present embodiment, a polarizer for selectively transmitting specific polarization components of an incident light beam may be arranged in an optical path of the projection system or an optical path of the light receiving system. In such a case, the resist layer formed on the wafer W has a higher reflectivity with respect to s-polarized light than p-polarized light. Thus, it is preferable that a polarizing member be used to selectively transmit only s-polarized light with respect to the detected surface Wa. In this structure, only light with a specific polarization component is received. This enables the surface position of the detected surface to be detected with high precision without being affected by relative displacement of polarization components in a light beam passing through the inner reflection surfaces of the prism member or the like. However, the use of such a polarizer is not practical from the viewpoint of light loss.
In the above embodiment, relative displacement between p-polarized light and s-polarized light is caused by the total reflection in the rhombic prisms (7 and 8), which has inner reflection surfaces. However, relative displacement between p-polarized light and s-polarized light may also be caused by reflection on outer reflection surfaces. In the above embodiment, a modification may be made so that relative displacement between p-polarized light and s-polarized light caused by reflection on such outer reflection surfaces is offset.
In the above embodiment, the exposure apparatus includes a single surface position detection apparatus. However, the present invention is not limited to such a structure and a plurality of surface position detection apparatuses may be used when necessary to divide a detection view field. In this case, the apparatuses may be calibrated based on a detection result obtained in a common view field of the detection field of a first surface position detection apparatus and the detection field of a second surface position detection apparatus.
In the above embodiment, the present invention is applied to the detection of a surface position of a photosensitive substrate in a projection exposure apparatus. However, the present invention may be applied to the detection of a surface position of a mask in a projection exposure apparatus. Further, in the above embodiment, the present invention is applied to the detection of a surface position of a photosensitive substrate in a projection exposure apparatus. However, the present invention may also be applied to the detection of the surface position of any normal detected surface.
The surface position detection apparatus and the exposure apparatus according to the above embodiment are manufactured by assembling various subsystems including elements described in the claims of the present application so as to maintain predetermined mechanical precision, electric precision, and optical precision. To maintain this precision, the optical systems are adjusted to obtain the optical precision, the mechanical systems are adjusted to obtain the mechanical precision, and the electric systems are adjusted to obtain the electric precision before and after the assembling process. The processes for assembling the exposure apparatus from the subsystems include mechanically connecting the subsystems to one another, wiring the electric circuits, and piping the pressure circuits. Processes for assembling each subsystem are performed before the process for assembling the subsystems to the exposure apparatus. After the process of assembling the exposure apparatus from the subsystems is completed, the apparatus is subjected to overall adjustment to obtain the required precision. It is preferable that the exposure apparatus be manufactured in a clean room under conditions, such as temperature and cleanness, which are controlled.
For example, a method for manufacturing the surface position detection apparatus of the above embodiment includes a process for preparing a first reflection surface (7b and 7c) arranged in a projection system, a process for preparing a second reflection surface (8b and 8c) arranged in a light receiving system, and a process for offsetting relative displacement of polarization components in a light beam passing through the first reflection surface of the projection system and the second reflection surface of the light receiving system.
A method for adjusting the surface position detection apparatus of the above embodiment includes a process for preparing a polarizing member (19, 20, 31, and 33) for generating an emission light beam having a characteristic that differs in accordance with a polarization component of an incident light beam, a process for offsetting relative displacement of polarization components in a light beam passing through the first reflection surface of the projection system and the second reflection surface of the light receiving system.
The exposure apparatus of the above embodiment may be used to fabricate microdevices (including semiconductor devices, imaging devices, liquid crystal display devices, and thin-film magnetic heads) by illuminating a reticle (mask) with an illumination system (illumination process) and exposing a transfer pattern formed on a mask onto a photosensitive substrate with a projection optical system (exposure process). One example of the procedures for fabricating a semiconductor device serving as a microdevice through formation of a predetermined circuit pattern on a photosensitive substrate, such as a wafer, using the exposure apparatus of the present embodiment will now be described with reference to a flowchart shown in FIG. 11.
In step S301 shown in FIG. 11, a metal film is first vapor-deposited on wafers of a first lot. In step S302, photoresist is applied to the metal film formed on each wafer of the first lot. In step S303, an image of a pattern formed on a mask is exposed and transferred sequentially onto shot-regions of each wafer of the first lot through a projection optical system with the use of the exposure apparatus of the present embodiment. In step S304, the photoresist formed on each wafer of the first lot is developed. In step S305, each wafer of the first lot is etched using the resist pattern formed on the wafer as a mask. This forms a circuit pattern corresponding to the mask pattern in the shot-regions of each wafer.
Afterwards, circuit patterns for upper layers are formed to complete a device such as a semiconductor element. The above-described semiconductor device manufacturing method fabricates semiconductor devices having ultra-fine circuit patterns with a high throughput. In steps S301 to S305, metal is deposited on the wafer through vapor deposition, resist is applied to the metal film, and then the processes in which the resist is exposed, developed, and etched are performed. Prior to these processes, a silicon oxide film may first be formed on the wafer, the resist may be applied to the silicon oxide film, and the processes in which the resist is exposed, developed, and etched may then be performed.
Further, the exposure apparatus of the present embodiment may be used to fabricate a liquid crystal display device serving as a microdevice by forming a predetermined pattern (a circuit pattern or an electrode pattern) on a plate (glass substrate). One example of a method for manufacturing a liquid crystal display device will now be described with reference to a flowchart shown in FIG. 12. In FIG. 12, in a pattern formation process S401, a mask pattern is transferred and exposed onto a photosensitive substrate (e.g., a glass substrate coated with resist) with the exposure apparatus of the present embodiment. In other words, a photolithography process is performed. Through the photolithography process, a predetermined pattern including many electrodes is formed on the photosensitive substrate. Afterwards, a predetermined pattern is formed on the substrate through processes including a developing process, an etching process, and a resist removing process. Then, a color filter formation process is performed in step S402.
In the color filter formation process S402, a color filter is formed by, for example, arranging many sets of R (red), G (green), and B (blue) dots in a matrix, or arranging a plurality of sets of filters formed by R, G, and B stripes in horizontal scanning line directions. After the color filter formation process S402, a cell assembly process is performed in step S403. In the cell assembly process S403, the substrate having a predetermined pattern obtained through the pattern formation process S401 and the color filter or the like obtained through the color filter formation process S402 are assembled together to form the liquid crystal panel (liquid crystal cell).
In the cell assembly process S403, for example, liquid crystal is injected between the substrate having the predetermined pattern obtained through the pattern formation process S401 and the color filter obtained through the color filter formation process S402 to form a liquid crystal panel (liquid crystal cell). In a module assembly process performed subsequently in step S404, an electric circuit for enabling the assembled liquid crystal panel (liquid crystal cell) to perform a display operation and other components including a backlight are attached to complete the liquid crystal display device. With the above-described liquid crystal display device manufacturing method, a liquid crystal display device having an ultra-fine circuit pattern is manufactured with a high throughput.

## Claims

1. A surface position detection apparatus for detecting a surface position of a surface to be detected, the surface position detection apparatus comprising:
a projection system which projects a light beam in a diagonal direction onto the surface to be detected;
a light receiving system which receives the light beam reflected by the surface to be detected; and
a displacement offset member which offsets relative displacement between two polarization components being different from each other in a polarization direction in the light beam reflected by a reflection surface arranged in at least one of the projection system and the light receiving system.

2. The surface position detection apparatus according to claim 1, wherein the displacement offset member includes an offset element which inclines travel direction of an emission light beam by a different angle in accordance with a polarization direction of an incident light beam.

3. The surface position detection apparatus according to claim 2, wherein the offset element is arranged in one of a pupil space of the projection system and a pupil space of the light receiving system.

4. The surface position detection apparatus according to claim 2, wherein:
the projection system includes a projection side imaging optical system which defines a position optically conjugate to the surface to be detected;
the light receiving system includes a light receiving side imaging optical system which defines a position optically conjugate to the surface to be detected; and
the offset element is arranged in one of a pupil space of the projection side imaging optical system and a pupil space of the light receiving side imaging optical system.

5. The surface position detection apparatus according to claim 1, wherein the displacement offset member includes an offset element which shifts in parallel travel direction of an emission light beam by a different distance in accordance with a polarization direction of an incident light beam.

6. The surface position detection apparatus according to claim 5, wherein the offset element is arranged in one of an object space or image space of the projection system and an object space or image space of the light receiving system.

7. The surface position detection apparatus according to claim 5, wherein:
the projection system includes a projection side imaging optical system which defines a position optically conjugate to the surface to be detected;
the light receiving system includes a light receiving side imaging optical system which defines a position optically conjugate to the surface to be detected; and
the offset element is arranged in one of an object space or image space of the projection side imaging optical system and an object space or image space of the light receiving side imaging optical system.

8. An exposure apparatus for projecting and exposing a predetermined pattern onto a photosensitive substrate with a projection optical system, the exposure apparatus comprising:
the surface position detection apparatus according to claim 1 which detects one of a surface position of a surface of the predetermined pattern and a surface to be exposed of the photosensitive substrate; and
an alignment device which aligns one of the surface of the predetermined pattern and the surface to be exposed of the photosensitive substrate with respect to the projection optical system based on a detection result of the surface position detection apparatus.

9. An exposure method for projecting and exposing a predetermined pattern onto a photosensitive substrate with a projection optical system, the exposure method comprising:
detecting a surface position of one of a surface of the predetermined pattern and a surface to be exposed of the photosensitive substrate using the surface position detection apparatus according to claim 1; and
aligning one of the surface of the predetermined pattern and the surface to be exposed of the photosensitive substrate with the projection optical system based on a detection result of the surface position detection apparatus.

10. A device manufacturing method comprising:
detecting a surface position of one of a surface of a predetermined pattern and a surface to be exposed of a photosensitive substrate using the surface position detection apparatus according to claim 1;
aligning one of the surface of the predetermined pattern and the surface to be exposed of the photosensitive substrate with a projection optical system based on a detection result of the surface position detection apparatus;
projecting and exposing the predetermined pattern onto the photosensitive substrate with the projection optical system; and
developing the photosensitive substrate that includes undergone the exposure.