JP2569713B2 - Projection exposure equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning apparatus in a projection exposure apparatus for manufacturing a semiconductor integrated circuit, and particularly to a focusing apparatus.

2. Description of the Related Art A step-and-repeat type reduction projection exposure apparatus, which is mainly used in a lithography process in the manufacture of a semiconductor integrated circuit, a so-called stepper, is formed on a mask or a reticle (hereinafter referred to as a reticle). A circuit pattern is exposed on a photosensitive substrate (hereinafter, referred to as a wafer) via a projection lens. At this time, if the projected image of the circuit pattern of the reticle is not accurately formed on the wafer, a blurred pattern is formed on the wafer, resulting in a problem of poor resolution. In addition, a projection lens having a large numerical aperture (NA) is generally used for such a stepper. Recently, however, the numerical aperture (NA) corresponding to the minimum line width of a circuit pattern formed on the order of sub-microns has been increased. Further increasing, the practical depth of focus of the projection lens has become very small. For this reason, in order to obtain a semiconductor integrated circuit that satisfies the desired characteristics, it is necessary to exactly match the imaging surface of the projection lens with the wafer surface. As a device having this focusing function,
For example, there is an apparatus as disclosed in Japanese Patent Application Laid-Open No. 60-168112 filed by the applicant of the present invention. In this type of apparatus, a so-called through-the-lens (TTL) type optical system for detecting a first mark on a reticle and detecting a second mark on a wafer via a projection lens is provided. For this, adjust this optical system to focus,
Thereafter, focusing is performed on the second mark by changing the distance between the wafer and the projection lens in the optical axis direction. Therefore, the reticle and the wafer are kept conjugate with respect to the projection lens, and the projected image of the circuit pattern of the reticle is always focused on the wafer (best focus).
Is projected.

[Problems to be solved by the invention]

However, in this type of apparatus, when focusing is performed by changing the distance between the wafer and the projection lens in the optical axis direction, the wafer is moved, for example, by Δn in the optical axis direction of the projection reticle, and a TTL type optical system is used. Therefore, it is necessary to detect the contrast of the mark image of the second mark for each position.
Also, when performing focusing between the TTL optical system and the reticle, measurement must be performed a plurality of times in the same manner, and there is a problem that time is required for focusing and throughput is reduced.

The present invention has been made in consideration of the above points, and has as its object to obtain a projection exposure apparatus having a focusing device capable of performing focusing with high accuracy and in a short time.

[Means for solving the problem]

The invention described in claim 1 of the present application for solving such a problem is a fiducial pattern as a reference pattern having a light-transmitting mark FMx (rectangular transparent window) formed extending in the Y-axis direction. A reference member 10 as a first substrate on which a mark FM is provided, and an illumination system which is arranged in the wafer stage 7 on the opposite side of the projection lens 6 with respect to the reference member 10 and illuminates the fiducial mark FM from the back surface. The circuit pattern formed in the pattern area Pa of the reticle R as the second substrate is projected and exposed on the photosensitive substrate (wafer W) via the projection reticle 6 while checking the various alignment systems of the fiber 11. Applies to equipment.

In the first aspect of the present invention, the first direction (X) is provided on the end face of the fiber 11 so as to be substantially conjugate with the pupil plane of the projection lens 6 and intersects the edge direction (Y-axis direction) of the mark FMx. The polarization filter 12 as a polarization means for changing the polarization characteristics of the illumination light from the fiber 11 with respect to the axial direction), and of the light transmitted through the mark FMx, incident on the pattern area Pa of the reticle R via the projection lens 6. It is arranged in the optical path of the illumination light passing through the reticle R without being interrupted by the formed mark RMx (cross mark), and the illumination light passing through this optical path is converted into a first polarization (P polarization) and a second polarization (S polarization). ), A polarizing beam splitter 15 as a polarization splitting means, a first detector 16 as a first photoelectric detecting means for receiving P-polarized light, and a second detector as a second photoelectric detecting means for receiving S-polarized light. And a main controller 30 as an adjusting means for changing an optical path length between the reticle R and the reference member 10 based on an output signal of the first detector 16 and an output signal of the second detector 17. I did it.

Further, according to the invention described in claim 2 of the present application, an optical image of the first pattern (fiducial mark FM) formed on the first substrate (reference member 10) is formed on a predetermined surface of the second substrate (reticle R). A projection optical system (projection lens 6) for projecting onto a portion, and a moving means (wafer stage 7) for relatively scanning and moving a first substrate (reference member 10) and a second substrate (reticle R).
And a second pattern (RMx, RMy1, R) defined on a predetermined portion of the second substrate (reticle R) by a transmission portion and a light shielding portion.
My2) and the first pattern (Fiducial Mark FM)
A projection exposure apparatus for detecting a relative image formation state between a first substrate (reference member 10) and a second substrate (reticle R) based on transmitted light generated when a light image of the first substrate is relatively scanned and moved. Applied to

In the invention described in claim 2 of the present application, the first
The light image of the pattern (fiducial mark FM) is an edge extending in a predetermined first direction when viewed in the plane of the scanning movement (for example, an image FM extending in the Y direction as shown in FIG. 4 (a)).
x ′), and the edge of the transmission part and the light-shielding part of the second pattern (for example, mark RMx extending in the Y direction as shown in FIG. 4A) when viewed in the plane of the scanning movement It is formed in a position substantially conjugate with the pupil plane of the projection optical system (6) by the transmitted light of the first pattern (for example, the transmitted light beam of FMx ') which is extended in the first direction and transmitted through the transparent portion of the second pattern. Photoelectric element and second photoelectric element which divide a pupil image (Ht in FIG. 7) into two substantially in a second direction which intersects a first direction (for example, the Y direction) at approximately 45 degrees and individually detect light amounts. (For example, two detectors 1 in FIG. 1)
6, 17 and the pupil dividing optical member Ms in FIG. 7 and the moving means (stage 7), the light image of the first pattern (for example, the image
FMx ′) and a second pattern (for example, mark RMx) are relatively scanned in a direction (X direction) orthogonal to the first direction.
The first scanning position (the fourth scanning position) where the signal waveform from the photoelectric element changes
Measurement means (waveform processing device 18) for measuring a stage position a) in FIG. 4B and a second scanning position (stage position b in FIG. 4B) where the signal waveform from the second photoelectric element changes. )
And the first substrate (reference member 1) based on the measured first operation position (position a) and the second scanning position (position b).
Calculating means (main controller 30) for calculating an error (defocus amount ΔZs, ΔZm) from the conjugate relationship between the second substrate (reticle R).

According to a third aspect of the present invention, the photoelectric detecting means defined in the second aspect of the present invention is disposed at a position substantially conjugate with a pupil of the projection optical system (6), and is disposed within a scanning movement plane (XY plane). When viewed from the inside, the pupil image is configured to include an optical member (Ms) for inclining by 45 degrees with respect to the first direction (one of the X direction and the Y direction) and dividing the pupil image into two. ), The light amount of one pupil image divided by the first photoelectric element (for example, one of the detectors 16 and 17) is detected, and the light amount of the other pupil image is detected by the second photoelectric element (for example, the other of the detectors 16 and 17). Detected.

According to a fourth aspect of the present invention, the moving means (wafer stage 7) holds the first substrate (reference member 10) and projects the first pattern (fiducial mark FM) onto the projection optical system (6). , And a desired photosensitive substrate (wafer W) is placed thereon.

According to a fifth aspect of the present invention, as the second substrate, a circuit pattern area (Pa) for projecting and exposing a photosensitive substrate (wafer W) on a stage (7) through a projection optical system (6) is provided. The formed reticle R is provided, and the second pattern (RMx, RMy1, RMy2) is formed at each of a plurality of locations around the circuit pattern area (Pa).

According to a sixth aspect of the present invention, in the projection exposure apparatus defined in the fifth aspect, the surface of the photosensitive substrate (wafer W) mounted on the stage (7) or the first substrate (reference member)
The surface of (10) is irradiated with an image forming light beam obliquely, and the reflected light beam is received, so that the photosensitive substrate (wafer W) or the first substrate (reference member 10) with respect to the image forming surface of the projection optical system (6).
Oblique incidence type focus detection means (20a,
20b) and a photosensitive substrate (wafer W) or a first substrate (reference member) based on the detection results of the focus detection means (20a, 20b).
An adjustment means (drive unit 9) for adjusting the stage (7) so as to change the distance between the projection optical system (6) and the projection optical system (6) is provided.

According to the seventh aspect of the present invention, the interval adjusted by the adjustment type (drive unit 9) based on the detection result of the oblique incidence type focus detection means (20a, 20b) is calculated by the arithmetic means (main controller 30). Correction means for calibrating according to the error calculated (for example, a tiltable parallel flat glass for focus offset provided in the focus detection system 20)
Was provided.

[Action]

According to the first aspect of the present invention, a conjugate between a reticle and a reference member on a wafer stage is formed as a projection lens for a light beam having an inclination of a principal ray with respect to the optical axis of the projection lens (hereinafter referred to as telecentric inclination). When the relationship is broken, the reticle-side focal position or the image forming position of the projection lens is X-axis perpendicular to the optical axis direction of the projection lens on the reticle pattern surface.
Shifting in the Y-axis direction is used. Therefore, the illumination light is divided into two parts, P-polarized light and S-polarized light (ordinary ray and extraordinary ray), which have different polarization characteristics by a polarizing filter, and the fiducial mark is projected on the fiducial mark. Scan the mark. Then, the illumination light passing through the reticle without being blocked by the reticle alignment mark is split into P-polarized light and S-polarized light by the polarizing beam splitter, and is received by the first detector and the second detector, respectively. Therefore, only by scanning the wafer stage once in the X direction, the amount of defocus (the amount of defocus) of the projection lens between the reticle and the reference member in the optical axis direction is calculated, and focusing is performed. The time required can be reduced.

Further, in the invention of claim 2 of the present application, a mark formed on the reticle R extending in the X-axis direction and a mark formed on the reticle R in the Y-axis direction are detected by common photoelectric detection means. The pupil image of the first pattern image FMx ′ of the reference member 10 generated at a position substantially conjugate with the pupil plane of the lens 6 is X or Y
A photoelectric detecting means is provided which is configured to divide the light into two parts in a direction inclined by about 45 degrees with respect to the axial direction and to receive each divided light individually with a photoelectric element. Therefore, the mark on the reticle R extending in the X direction and the mark on the reticle R extending in the Y direction are scanned by the fiducial mark FM on the reference member 10 in each direction, and the X-axis The defocus amount by measuring the direction and the defocus amount by measuring in the Y-axis direction can be obtained by a common sensor.

Further, in each of the second to seventh aspects of the present invention, a pupil image generated at a position substantially conjugate with the pupil of the projection lens 6 (for example, a position in the exposure illumination optical systems 1 to 4 in FIG. 1) is divided into two parts. Since the light beams forming the divided pupil images are individually photoelectrically detected, the polarization of the polarization means (polarization filter 12) and the polarization splitting means (polarization beam splitter 15) as in the first invention is performed. It is possible to prevent the occurrence of offset due to astigmatism of the projection lens 6 without using an operation.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a stepper having a focusing device according to a first embodiment of the present invention.

In FIG. 1, an unillustrated illumination light source for exposure is g-line,
Illumination light having a wavelength (exposure wavelength) for exposing a resist such as i-line is generated. This illumination light passes through a fly-eye lens 1 and a beam splitter 2 and then reaches a condenser lens 4 via a mirror 3. The pattern area Pa of the reticle R held on the reticle stage 5 is illuminated with uniform illuminance. Here, as shown in FIG. 2, marks RMx, RMy ₁ and RMy ₂ having cross marks formed of a chrome layer on a transparent window are projected on the reticle R as reticle alignment marks RM, which are attached to the pattern area Pa. The lens 6 is provided in the exposure field IF. The two-sided or one-sided telecentric projection lens 6 is used to
Is projected onto the wafer W on which the resist has been applied. However, the reticle alignment mark RM may be shielded from light during actual element exposure by a reticle blind (not shown). The wafer W is provided on a wafer stage 7 via a wafer holder (θ table) (not shown), and the position of the wafer stage 7 in the X direction is
And a plane mirror 8m provided on the wafer stage 7. A reference member 10 such as a glass substrate provided with a fiducial mark FM used for performing focusing, baseline measurement, etc., is placed on the wafer stage 7.
Are provided so as to substantially coincide with the surface position of the wafer W. This reference member 10 has a fiducial mark FM
Is a rectangular mark that is a light-transmitting slitter pattern extending in the Y-axis and X-axis directions used for focusing and the like.
FMx and FMy, and a diffraction grating mark formed by a concave and convex with a light-reflective chromium layer used for position detection of the off-axis type wafer alignment system 19 and the like are provided. The fiducial mark FM is moved downward (inside the wafer stage 7) through the lens 13 and the mirror 14 by illumination light (exposure light) such as g-line and i-line transmitted below the reference member 10 using the fiber 11. ). Here, as shown in FIG. 3, a filter 12p that passes only P-polarized light,
A polarizing filter 12 consisting of a fiducial 12s that passes only S-polarized light is provided on the end face of the fiber 11 by a polarizing filter 12s.
Is orthogonal to the edge direction (Y-axis direction) of the mark FMx, that is, the division direction coincides with the X-axis direction, and is substantially conjugate with the pupil plane of the projection lens 6. Therefore, fiducial mark FM will be illuminated by the illumination light consisting of S-polarized light having a P-polarized light having the telecentricity inclination theta _1, telecentricity inclination theta _2. The light transmitted through the fiducial mark FM forms an image of the fiducial mark FM on the pattern surface of the reticle R via the projection lens 6. Further, the light transmitted through the reticle R without being blocked by the reticle alignment mark RM is incident on the polarization beam splitter 15 via the beam splitter 2 and the like, and is split into P-polarized light and S-polarized light. It is configured to be received by the second detector 17. The off-axis type wafer alignment system 19 irradiates a predetermined diffraction grating mark (wafer mark) formed on the wafer W with spot light (sheet beam) extending in the Y direction, and moves the wafer stage 7 in the X direction. In the X direction of the wafer mark. Further, an image forming light flux l ₁ for forming an image of a pinhole or a slit toward the image forming surface of the projection lens 6.
An irradiation optical system 20a for irradiating obliquely, the light receiving optical system 20b for receiving reflected light beam l ₂ of the wafer W surface of the imaging light beam l ₁
And a focus detection system 20 of the oblique incident light type. The configuration and the like of the focus detection system 20 are disclosed in, for example, Japanese Patent Application Laid-Open No. 60-168112 filed earlier by the present applicant, and the description thereof is omitted. Is detected and the wafer W and the projection lens 6 are detected.
Is to detect the in-focus state with the image forming plane. The main controller 30 controls the position of the projection lens 6 of the wafer stage 7 in the optical axis direction (Z direction) based on the output signal of the first detector 16 and the output signal of the second detector 17 and also performs wafer alignment. The overall operation of the apparatus including the system 19 and the focus detection system 20 is totally controlled. Further, it outputs a predetermined drive command to the drive unit 9 and the like of the wafer stage 7 according to the calculation value of the main controller 30 and the amount of displacement detected by various alignment systems.

Next, the operation of the device configured as in the present embodiment will be described. In FIG. 1, the main controller 30 first detects the telecentric inclinations θ ₁ and θ ₂ of the P-polarized light and the S-polarized light of the illumination light from the fiber 11. Therefore, the wafer stage 7 is moved to Z
After moving in the direction, the reference member 10 is positioned at a predetermined position (coordinate value Z ₁ ) using the focus detection system 20, and then the reference member 10 is illuminated from below with the illumination light transmitted by the fiber 11,
Mark on the pattern surface of reticle R via projection lens 6
The projection image FMx ′ of FMx is formed. Next, as shown in FIG. 4 (a), the wafer stage 7 is moved in the X direction so that the projected image FMx 'relatively scans the rectangular mark portion extending in the Y axis direction of the mark RMx in the X direction. Move slightly. At this time, mark
The light transmitted through the reticle R without being blocked by the RMx enters the polarization beam splitter 15 via the condenser lens 4, the mirror 3, and the beam splitter 2. Then, in the polarization beam splitter 15, the illumination light is split into P-polarized light and S-polarized light, and the first detector 16
And the second detector 17. On this occasion,
When the projected image FMx 'and the mark RMx match, the amount of light passing through the reticle R becomes the smallest, and the amount of light sequentially increases according to the shift. Next, the P-polarized light and the S-polarized light
The photoelectric conversion is performed by the detector 16 and the second detector 17, and the photoelectric signal is output to the waveform processing device 18. In this waveform processing device 18, the photoelectric signal is processed in synchronization with the position signal of the wafer stage 7 by the laser interferometer 8, and the waveform signals S ₁ and S ₂ as shown in FIG.
Output to In the waveform signals S ₁ and S ₂ , the position a is P
The position where the projected image FMx ′ by polarized light and the mark RMx match,
The position b is a position where the projected image FMx 'by S-polarized light and the mark RMx match. Therefore, the main controller 30 sets the position a,
The position of b in the X direction is detected, and its value is stored as coordinate values Xp ₁ and Xs ₁ .

Next, the wafer stage 7 is moved in the Z direction to move the reference member.
After positioning the position 10 at a predetermined position (coordinate value Z ₂ ) using the focus detection system 20, a position where the mark RMx and the projected image FMx ′ match at the coordinate value Z ₂ is detected by the same operation as described above, The values are stored as coordinate values Xp ₂ and Xs ₂ . The resulting Z
FIG. 4C shows the relationship between the position in the direction (focal position) and the matching position. In FIG. 4 (c), since the inclinations of the straight lines correspond to the telecentric inclinations θ ₁ and θ ₂ of the P-polarized light and the S-polarized light, respectively, the main controller 30 calculates the telecentric inclinations θ ₁ and θ ₂ from these inclinations. And memorize. Note that the telecentric inclination θ
_In the detection of ₁ , θ ₂ , the operation similar to the above, that is, the mark RMx and the projected image FM
It is preferable to detect the position where x 'coincides a plurality of times and calculate and store the telecentric inclinations θ ₁ and θ ₂ from the average inclination of the straight line obtained as a result.

The main controller 30 moves the wafer stage 7 in the Z direction to move the surface of the reference member 10 to a predetermined reference position (coordinate value Zn) using the focus detection system 20 in order to perform focusing.
Position. Then, the mark FMx is illuminated from below with the illumination light transmitted through the fiber 11 in the same manner as the detection operation of the telecentric inclinations θ ₁ and θ ₂ , and the projected image FMx ′ becomes the mark RMx
The wafer stage 7 is slightly moved in the X direction so that the rectangular mark portion extending in the Y axis direction is relatively scanned in the X direction.
Next, the illumination light that has passed through the reticle R without being blocked by the mark RMx is incident on the polarization beam splitter 15 via the beam splitter 2 and the like, split into P-polarized light and S-polarized light, and Light is received by the two detectors 17. The waveform processing device 18 detects a waveform signal similar to the waveform signal shown in FIG. 4B based on the photoelectric signals of the first detector 16 and the second detector 17 and the position signal from the laser interferometer 8. Then, it outputs to main controller 30. Main controller 30 detects the positions Xpn and Xsn where mark RMx and projecting agent FMx 'of mark FMx match from this waveform signal, as shown in FIG. In FIG. 5, the straight lines f (θ ₁ ) and f (θ ₂ ) are characteristics previously obtained by the operation of FIG. next,
The deviation amount ΔX (ΔX = Xpn−Xsn) of the matched position,
Based on the telecentric inclinations θ ₁ and θ ₂ , a defocus amount ΔZ between the reticle R and the reference member 10 is calculated from the following equation (1).

Next, with respect to the projection lens 6, the reticle R and the reference member 10
The main controller 30 moves the wafer stage 7 in the Z-axis direction via the drive unit 9 so that the detection value at the position (coordinate value Zn) of the focus detection system 20 changes by ΔZ so that Move by the defocus amount ΔZ. Thus, the reticle R and the reference member 10 are set at conjugate positions with respect to the projection lens 6, and the surface of the reference member 10 and the image forming surface of the projection lens 6,
In other words, the surface of the wafer W and the image plane exactly match, and the positioning (focusing) in the Z direction ends.

Next, focusing when the wafer W has unevenness in resist thickness or the like will be described. Therefore, the main controller 30 first corrects (calibrates) the focus position of the focus detection system 20 using the reference member 10 located on the image plane of the projection lens 6. Here, the calibration of the focus detection system 20 will be briefly described since it is disclosed in, for example, Japanese Patent Application Laid-Open No. 60-168112 filed by the present applicant.
First, the irradiation optical system 20a irradiates a parallel light beam onto the reference member 10 from an oblique direction through a slit opening, a parallel plate glass (plane parallel) or the like, and forms a slit image on the reference member 10. Then, the light receiving optical system 20b receives the parallel light beam reflected from the reference member 10 by a photoelectric detector via a vibration mirror, a slit plate, and the like. At this time, in the light receiving optical system 20b, the slit image reciprocates on the slit plate with a constant amplitude by the vibrating mirror, and the position of the vibration center on the light receiving surface of the photoelectric detector is one in the Z direction of the reference member 10. Shift accordingly. Therefore, the angle of the parallel plate glass is adjusted and fixed so that the center of vibration of the slit image on the slit plate coincides with the slit opening. This completes the calibration of the focus detection system 20 using the surface of the reference member 10 in the Z direction, that is, the image plane of the projection lens 6 as a zero point reference. Instead of using the reference member 10 has been positioned in the coordinate value Z ₀ and the wafer stage 7 defocus amount ΔZ is moved in the Z direction, the reference member 10 of the position detected defocus amount ΔZ
Using the (coordinate value Zn), the angle of the parallel flat glass may be adjusted so that an offset is generated by the defocus amount ΔZ, and the focus detection system 20 may be calibrated.

Next, the wafer stage 7 is moved to a predetermined exposure start position, and exposure is started after positioning the wafer W. Therefore, main controller 30 uses focus detection system 20 to control wafer W
The position of the upper exposure area in the Z direction is detected. Then, the focus detection system 20 is adjusted so that the difference between this position and the zero point reference becomes zero.
The wafer stage 7 is moved in the Z direction on the basis of the output signal of. As a result, the projected image of the circuit pattern of the reticle R is projected onto the exposure area on the wafer W in a focused state (best focus), and the exposure is performed without occurrence of resolution failure due to defocus. Next, after the wafer stage 7 is stepped by a predetermined amount, focusing is similarly performed by the focus detection system 20, and then the circuit pattern of the reticle R is transferred onto the wafer W. By performing focusing by the focus detection system 20 for each exposure area in this way, occurrence of resolution failure or the like due to unevenness in resist thickness or the like is prevented, and the entire surface of the wafer W is always exposed in focus.

In this embodiment, the polarization fiducial 12 is applied to the end face of the fiber 11 so as to be substantially conjugate with the pupil plane of the projection lens 6.
However, there is no particular need to use a fiber, and another means may be used without using the fiber 11. For example, a relay optical system, a mirror or the like is used to guide the illumination light so that the image of the illumination light source is formed on the polarizing filter 12 disposed at a position conjugate with the pupil plane of the projection lens 6. To illuminate the fiducial mark FM. Similarly, a rectangular mark portion extending in the Y-axis direction of the marks RMy ₁ and RMy ₂ is used, and the defocus amount Δ at that position is used.
If Z is detected, the image plane inclination of the projection lens 6 and the like can be obtained.

Thus, according to the present embodiment, the absolute value of the defocus amount ΔZ is detected only by scanning the wafer stage 7 once, so that the time required for focusing can be reduced, and the focused state (best Exposure).

As described above, in the embodiment of the present invention, the telecentric inclinations θ ₁ and θ ₂ have been obtained in advance, but the intersection of the straight line shown in FIG. 4 (c) corresponds to the projected image FMx ′ as in FIG. , The position at which the defocus amount ΔZ between the reticle R and the reference member 10 becomes zero (in-focus position). Accordingly, by moving the wafer stage 7 in the Z direction based on the defocus amount ΔZ obtained from the in-focus position in parallel with the detection of the telecentric inclinations θ ₁ and θ ₂ , focusing can be performed in the same manner as in the above-described embodiment. It is clear that can be done.

In addition, off-axis type wafer alignment system
When measuring the relative positional relationship between the 19 mark detection center position and the position of the projected image of the reference point (reticle alignment mark or the like) on the reticle R, that is, the measurement of the position of the reticle alignment mark RM when measuring the so-called baseline. Fiber
In a state where the chief ray of the illumination light from 11 is tilted with respect to the optical axis of the projection lens 6 due to a manufacturing error or the like and is not accurately focused, an offset occurs at a measured position. It was necessary to perform baseline measurement from. However, it is apparent that the focus measurement can be performed and the baseline measurement, that is, the position of the reticle alignment mark RM can be detected at the same time when the focusing apparatus according to the present embodiment is used. For example, at a predetermined reference position (coordinate value Zn), the mark FMx
Is scanned over the rectangular upper mark portion of the mark RMx extending in the Y-axis direction with the projected image FMx ′. At this time, a graph as shown in FIG. 5 is obtained from the positions Xpn and Xsn where the projected image FMx ′ obtained from the waveform signal detected by the waveform processing device 18 and the mark RMx match, and the telecentric inclinations θ ₁ and θ ₂ . Is detected. Here, in FIG. 5, the intersection of the straight lines f (θ ₁ ) and f (θ ₂ ) represents the focus position (coordinate value Z ₀ ) as in FIG. 4 (c). By moving the wafer stage 7 in the Z direction by the defocus amount ΔZ (ΔZ = Z ₀ −Zn) detected based on the above, focusing can be performed. Now,
The coordinate value X _{0 of the} intersection detected together with the focus position (coordinate value Z ₀ )
Indicates a position where the projected image FMx ′ and the mark RMx match at the in-focus position. That is, the position of the mark RMx can be accurately detected without including a detection error due to defocus at the same time as the detection of the defocus amount ΔZ, and it is not necessary to perform focusing before the baseline measurement. Therefore, the baseline is measured from the position of the mark RMx detected in this way and the detection center position of the wafer alignment system 19 detected using the diffraction grating mark formed on the reference member 10, and the baseline is measured. The time required for measurement can be reduced.

Further, in the present embodiment, a rectangular mark portion extending in the Y-axis direction of the mark RMx arranged in the exposure field IF of the projection lens 6 shown in FIG. To detect the defocus amount ΔZ at that position. Here, mark as in this embodiment
The case where the defocus amount ΔZ is detected using the rectangular mark portion extending in the S direction of RMx, and the case where the mark RMx extends in the X-axis direction, that is, the meridional direction (hereinafter, referred to as M direction).
In the case where the defocus amount ΔZ is detected using the rectangular mark portion of, the imaging position of the projection lens 6 in the optical axis direction on the reticle side differs due to astigmatism of the projection lens 6, and S
In the detection of the defocus amount ΔZ using only the rectangular mark portions extending in the direction, an offset may occur. Therefore, the third
The polarizing filter 12 is provided on the end face of the fiber 11 so that the dividing direction of the polarizing filter 12 shown in the drawing is inclined by 45 degrees in the plane of the coordinate system XY. Then, the rectangular mark portion extending in the S direction of the mark RMx in the projected image of the mark FMx is scanned once in the X-axis direction to detect the defocus amount ΔZs, and similarly, the M of the mark RMx is detected in the projected image of the mark FMy. The defocus amount ΔZm is detected by scanning the rectangular mark portion extending in the direction once in the Y-axis direction. Based on this result, a predetermined reference position (coordinate value Z
If the configuration is such that the defocus amount ΔZ in n) is obtained, occurrence of an offset due to astigmatism of the projection lens 6 can be prevented. Also, as shown in FIG.
It is apparent that the same effect can be obtained by using a polarizing filter in which the light shielding portions 12a and 12b are provided in the divided quadrants facing each other, by using the polarizing filter 12 inclined at 45 degrees.

Although the polarization fiducial 12 is used in this embodiment, the illumination light transmitted through the reticle R is spatially divided at a position substantially conjugate with the pupil plane of the projection lens 6 as shown in FIG. In other words, if the optical member Ms for dividing the pupil image Ht in the X-axis direction with respect to the wavefront is provided, and the detector is configured to receive the two divided light beams, the mark RM
The defocus amount ΔZ at each position can be detected using a rectangular mark extending in the Y-axis direction of x, RMy ₁ , and RMy ₂ , and the same effect can be obtained without using the polarizing filter 12. Is clear. Alternatively, instead of the above-described optical member Ms, a four-divided light receiving element is provided at a position substantially conjugate with the pupil plane.
The same effect can be obtained even if the divided light receiving element is configured to receive the illumination light transmitted through the reticle R by dividing the illumination light into two in the X-axis direction, and to emit light respectively. Further, as an embodiment corresponding to the invention of claim 2 of the present application, the above-mentioned optical member Ms moves the pupil image Ht with respect to the X axis or the Y axis of the coordinate system XY.
If the optical member Ms is inclined at 45 degrees in the plane of the coordinate system XY so as to be divided into two in the direction inclined by degrees, and provided at a position substantially conjugate with the pupil plane of the projection lens 6, for example, the X axis of the mark RMx, the Y axis Using each rectangular mark extending in the axial direction, the defocus amount ΔZ at that position can be obtained from the defocus amounts ΔZs and ΔZm. Even when measurement is performed without using the polarization fiducial 12, projection is performed. The occurrence of offset due to astigmatism of the lens 6 can be prevented. As shown in FIG. 8, when the mark RM 'is provided at a position rotated by 45 degrees with respect to the reticle center RC in the coordinate system XY as a reticle alignment mark, the illumination light transmitted through the fiducial mark FM is: In the mark RM ', it is necessary to consider the telecentric inclination in two directions, that is, the reticle center direction (S direction) and the concentric tangent direction (M direction).
Accordingly, the light receiving optical system composed of the above-described optical member Ms and the two detectors for receiving the illumination light transmitted through the mark RM ′ is inclined by 45 degrees with respect to the pupil image Mt in the S direction and the M direction, that is, the coordinate system XY. And two sets are arranged so as to receive light in two directions with respect to the direction, for example, the mark RM 'in the projected image of the mark FMx.
If it is configured to scan a rectangular mark portion extending in the Y-axis direction, the defocus amounts ΔZs and ΔZm are detected in one scan without using the polarization filter 12, and
The defocus amount ΔZ at that position can be detected, and the occurrence of offset due to astigmatism can be prevented.

〔The invention's effect〕

As described above, according to the present invention, the defocus amount is detected only by scanning the wafer stage once, so that the time required for focusing can be reduced. Also,
Since the position where the projected image of the fiducial mark matches the reticle alignment mark is measured without depending on the stepping accuracy of the wafer stage, the amount of defocus can be detected with high accuracy, and a high-precision focus can be obtained. Matching can be performed. Furthermore, the position of the reticle alignment mark is also detected simultaneously when detecting the defocus amount, so that the time required for the baseline measurement can be shortened and without depending on the telecentricity of the illumination light, the focal position, and the like. Since measurement is performed, highly accurate baseline measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a plan view showing a schematic configuration of a stepper having a focusing device according to a first embodiment of the present invention, FIG. 2 is a plan view showing a schematic configuration of a reticle, and FIG. FIG. 4 (a) is a diagram for explaining a schematic configuration and arrangement of the wafer, FIG. 4 (a) is a diagram for explaining when a projected image of a fiducial mark scans a reticle alignment mark, and FIG. FIG. 4C is a diagram showing a waveform signal obtained when detecting a change in the amount of light of the first and second detectors in synchronization with the position signal of the stage. FIG. FIG. 6 is a diagram illustrating an example of a configuration of a polarization filter, FIG. 6 is a diagram illustrating an example of a configuration of a polarization filter, and FIG. 7 is a diagram illustrating a schematic arrangement of an optical member that performs wavefront division. Fig. 8 shows an example of the reticle configuration It illustrates. 2 Beam splitter 6 Projection lens 7
Wafer stage, 10 Reference member, 11 Fiber
12 ... Polarizing filter, 15 ... Polarizing beam splitter, 16, 17 ... Detector, 18 ... Waveform processing device, 20
a: Irradiation optical system, 20b: Light receiving optical system, 30: Main controller, R: Reticle, W: Wafer, FM: Fiducial mark

Claims (7)

(57) [Claims] A first substrate having a light-transmissive reference pattern having a predetermined shape; and an illumination system disposed on a side opposite to the projection optical system with respect to the first substrate and illuminating the reference pattern. An apparatus for projecting and exposing a pattern formed on two substrates onto a photosensitive substrate via the projection optical system, wherein a polarization characteristic of a light beam from the illumination system is made different in a first direction intersecting an edge direction of the substrate pattern. Polarizing means; arranged in an optical path of the light beam passing through the second substrate from the reference pattern via the administration optical system;
Polarization splitting means for splitting the optical path into first polarized light and second polarized light; first photoelectric detecting means for receiving the first polarized light; second photoelectric detecting means for receiving the second polarized light; Adjusting means for changing an optical path length between the second substrate and the first substrate based on an output signal of a photoelectric detecting means and an output signal of the second photoelectric detecting means. Projection exposure equipment. 2. A projection optical system for projecting a light image of a first pattern formed on a first substrate onto a predetermined portion on a second substrate, and relatively moving the first substrate and the second substrate by scanning. Moving means for moving the optical image of the second pattern and the light image of the first pattern, which are defined by a transparent portion and a light-shielding portion in a predetermined portion on the second substrate. In a projection exposure apparatus that detects a relative image forming state between the first substrate and the second substrate based on transmitted light, the light image of the first pattern is a predetermined first image when viewed in a plane of the scanning movement. The second pattern is shaped so as to have an edge extending in one direction, and the edge of the transmission part and the light-shielding part of the second pattern extends in the first direction when viewed in the plane of the scanning movement; A pupil image formed at a position substantially conjugate with the pupil plane of the projection optical system, Photoelectric detection means including a first photoelectric element and a second photoelectric element which are divided into two substantially in a second direction which intersects the first direction at substantially 45 degrees and individually detect the amount of light; When the image and the second pattern are relatively scanned in a direction orthogonal to the first direction, the first scanning position where the signal waveform from the first photoelectric element changes and the signal waveform from the second photoelectric element change Measuring means for measuring a second scanning position to be calculated; calculating an error from a conjugate relationship between the first substrate and the second substrate based on the measured first scanning position and the second scanning position. A projection exposure apparatus comprising: a calculation unit. 3. The photoelectric detecting means is arranged at a position substantially conjugate with a pupil plane of the projection optical system, and when viewed in the plane of the scanning movement, shifts the pupil image by 45 degrees with respect to the first direction. The first photoelectric element detects the light amount of one pupil image divided by the optical member and detects the light amount of the other pupil image by the second photoelectric element The projection exposure apparatus according to claim 2, wherein: 4. The moving means is a stage for holding the first substrate, moving the first pattern two-dimensionally within the field of view of the projection optical system, and mounting a desired photosensitive substrate. 4. The projection exposure apparatus according to claim 3, wherein: 5. A circuit pattern area for projecting and exposing a photosensitive substrate on the stage through the projection optical system is formed on the second substrate, and the second substrate is provided at each of a plurality of locations around the circuit pattern area. 5. The projection exposure apparatus according to claim 4, wherein the projection exposure apparatus is a reticle on which a pattern is arranged. 6. The projection exposure apparatus according to claim 1, wherein the projection exposure apparatus irradiates the surface of the photosensitive substrate placed on the stage or the surface of the first substrate with an image forming light beam obliquely and receives the reflected light beam. Oblique incident light type focus detection means for detecting a focus shift of the photosensitive substrate or the first substrate with respect to an image forming plane of the projection optical system, and the photosensitive substrate or the first substrate based on a detection result of the focus detection means. 6. The projection exposure apparatus according to claim 5, further comprising adjusting means for adjusting the stage so as to change a distance between the substrate and the projection optical system. 7. The projection exposure apparatus includes correction means for calibrating an interval adjusted by the adjustment means based on a detection result of the focus detection means in accordance with an error calculated by the calculation means. 7. The projection exposure apparatus according to claim 6, wherein: