JPH10294268A - Projection aligner and positioning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection aligner and a positioning method, which can reduce base line errors and can improve the precision of base line measurement on the projection aligner and the positioning method. SOLUTION: The device is provided with an illumination light source 2 illuminating a reticle R, a projection optical system PL projecting the pattern of the reticle R on a photosensitive substrate W loaded on a substrate stage WST, an alignment reference board 10 where reference marks 12, 20 and 22 used for measuring a relative position (base line) between the reticle R and a substrate alignment optical system 14, a stage sensor part 26 measuring the respective positions of the space images of a plurality of relicle alignment marks, and a controller 52 correcting the value of a base line and controlling illumination light IL so that the illumination of an exposure pattern plotting area and the illumination of the reticle alignment marks are switched.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a projection exposure apparatus and a positioning method used in a photolithography process for manufacturing a semiconductor device, a liquid crystal display device, a thin film magnetic head, and the like.

[0002]

2. Description of the Related Art In a photolithography process in a manufacturing process of a semiconductor device, a liquid crystal display device, a thin film magnetic head, or the like, a projection exposure apparatus is used to form a fine circuit pattern on a semiconductor layer or a metal wiring layer. This projection exposure apparatus places a reticle or a photomask (hereinafter, collectively referred to as a reticle) on which a circuit pattern is drawn on a reticle stage, and applies a resist-coated semiconductor substrate or glass substrate (hereinafter, referred to as a photosensitive substrate). The mounted substrate stage moves two-dimensionally in the X and Y directions relative to the reticle to project and expose a circuit pattern of the reticle onto a predetermined region of the photosensitive substrate. At this time, the projection image of the reticle circuit pattern by the projection optical system needs to be accurately aligned (aligned) with a predetermined position on the photosensitive substrate.

As an alignment method, there is an off-axis alignment method. The off-axis alignment method detects the position of an alignment mark on a photosensitive substrate using a substrate alignment optical system having an optical axis at a position different from the optical axis of the projection optical system, and mounts the photosensitive substrate on the basis of the position. This is a method in which the substrate stage placed is moved by a predetermined amount, and the photosensitive substrate is positioned in the projection area of the projection optical system and exposed.

In order to realize accurate alignment by using this off-axis alignment method, a position between a projection center position of a circuit pattern on a reticle and a detection position of a mark on a photosensitive substrate by a substrate alignment optical system is required. It is necessary to accurately measure the distance (hereinafter, referred to as a baseline) in advance.

[0005] For example, the reference line provided on the substrate stage is detected by a substrate alignment optical system, the position of the substrate stage at that time is measured by a laser interferometer, and then the substrate stage is moved. The superimposed image of the reference mark image and the image of the alignment reticle alignment mark provided on the reticle is detected by the reticle alignment optical system, and the position of the substrate stage at that time is measured by a laser interferometer. ,
It is measured as the amount of movement of the substrate stage.

An example of the baseline measurement in such an off-axis alignment method is disclosed in
There is one disclosed in Japanese Patent No. 7823. In this method, a light quantity detector is provided on a substrate stage, and an image of an alignment reticle alignment mark provided on a reticle is directly detected at an opening of the light quantity detector via a projection optical system, and the substrate at that time is detected. The position of the stage is measured by a laser length measuring instrument, and then the substrate stage is moved, and the position of the opening of the light quantity detector is detected by a pattern position detecting device having an optical axis at a position different from the optical axis of the projection optical system. To measure the baseline.

[0007]

However, in the measurement of these conventional baselines, the baseline is obtained by moving the substrate stage and measuring the amount of movement with a laser interferometer. Therefore, the conventional method has a problem that a length measurement error of the laser interferometer for measuring the movement amount of the substrate stage with respect to the obtained baseline is included.

Further, in recent years, due to the demand for higher density and finer semiconductor devices, reticle manufacturing errors caused in the reticle manufacturing stage by an electron beam drawing apparatus or the like cannot be ignored. In the case of directly observing the reticle alignment mark as in the method disclosed in Japanese Patent No. 7823, there is also a problem that a position error of the reticle alignment mark due to a reticle manufacturing error is included as an error in a baseline. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a projection exposure apparatus capable of improving the accuracy of baseline measurement by reducing a length error of a laser length measuring device and a reticle manufacturing error due to a movement of a substrate stage. And an alignment method.

[0010]

An object of the present invention is to provide an illumination system for illuminating a reticle having a plurality of reticle alignment marks and an exposure pattern formed thereon, a projection optical system for projecting a reticle pattern onto a substrate, and a substrate. A substrate stage mounted and movable two-dimensionally within the projection plane of the projection optical system;
A substrate alignment optical system for observing a predetermined mark on the substrate, and an alignment reference plate provided on the substrate stage and formed with a reference mark used for measuring a relative position between the reticle and the substrate alignment optical system, A spatial image position measuring means provided on the substrate stage, for detecting a spatial image of the plurality of reticle alignment marks by the projection optical system and measuring each position of the spatial image, and a plurality of the spatial images measured by the spatial image position measuring means. Correction means for correcting the value of the relative position between the reticle and the substrate alignment optical system obtained using the reference mark of the alignment reference plate based on each projection position information of the aerial image, and illumination of the exposure pattern drawing area And a control system for controlling an illumination system so as to switch between illumination of a reticle alignment mark and a projection exposure apparatus. It is achieved by.

The above object is also achieved by providing an illumination system for illuminating a reticle having a plurality of reticle alignment marks and an exposure pattern formed thereon, a projection optical system for projecting a reticle pattern onto a substrate, and a substrate mounted thereon. A substrate stage movable two-dimensionally within a projection plane of the projection optical system, a substrate alignment optical system for observing a predetermined mark on the substrate, and a reticle and the substrate alignment optical system provided on the substrate stage. An alignment reference plate on which a reference mark to be used for measuring the relative position of the reticle is provided, and a plurality of reticle alignment marks provided on the alignment reference plate, which are detected by the projection optical system, and each position of the spatial image is detected. Aerial image position measuring means for measuring the position of each of the plurality of aerial images measured by the aerial image position measuring means. Correction means for correcting the value of the relative position between the reticle and the substrate alignment optical system obtained using the reference mark of the reference plate, illumination to switch between illumination of the exposure pattern drawing area and illumination of the reticle alignment mark And a control system for controlling the system. Here, the aerial image position measuring means is preferably provided substantially at the center of the alignment reference plate.

In these projection exposure apparatuses, the substrate alignment optical system may be arranged so as to detect the position of the substrate alignment reference mark without using the projection optical system. The illumination system includes a main illumination system that illuminates the exposure pattern drawing area, and a sub-illumination system that has the same light source as the main illumination system and illuminates an area other than the exposure pattern drawing area. May be switched between a main lighting system and a sub lighting system. Alternatively, the illumination system has an aperture that limits the size and shape of the illumination area of the reticle, and the control system controls the aperture so that illumination of the pattern drawing area for exposure and illumination of the reticle alignment mark area are controlled. The switching may be performed.
Further, the control system may switch the illumination by controlling the aperture so as to enlarge the illumination area from the exposure pattern writing area to an area other than the exposure pattern writing area.

The aerial image position measuring means has an opening which moves near each image forming position of the aerial image as the substrate stage moves, and a photoelectric conversion element provided below the opening. The opening is relatively scanned with respect to the aerial image by finely moving the stage at a constant speed, and each aerial image is photoelectrically detected by a photoelectric conversion element below the opening, and the position of each aerial image is measured based on a detection signal. You may make it. The opening may be formed so as to be wider in the scanning direction than the aerial image.

In the above-mentioned projection exposure apparatus, the illumination system may include a light amount adjusting means for adjusting the amount of light incident on the photoelectric conversion element. Further, the illumination system may include an incident angle adjusting unit that adjusts an incident angle of the illumination light to the photoelectric conversion element.

It is another object of the present invention to illuminate a reticle on which a plurality of reticle alignment marks and an exposure pattern are formed, and to project the reticle pattern on a substrate stage by a projection optical system, separately from the projection optical system. The relative position between the provided substrate alignment optical system and the reticle is determined based on the reference mark provided on the substrate stage, and the spatial images of the plurality of reticle alignment marks by the projection optical system are detected to obtain the spatial image. This is achieved by a positioning method characterized in that each position is measured and the value of the relative position is corrected based on each of the measured projection position information of the plurality of aerial images.

According to the present invention, a plurality of marks or patterns are actually measured with respect to the measured baseline, and a correction value for correcting a reticle manufacturing error is calculated based on the actually measured values. Is corrected, an extremely high-accuracy baseline with a small error can be obtained. Further, according to the present invention, the positions of the plurality of reticle alignment marks including the reticle alignment marks for baseline measurement are measured by the aerial image position measuring means, so that the aerial image position measuring means and the alignment reference plate are mounted on the substrate stage. Measurements that do not cause an error can be performed even at a remote position above. Further, if the aerial image position measuring means is provided on the alignment reference plate, the aerial image position measuring means does not have to measure the aerial image of the reticle alignment mark for baseline measurement.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A projection exposure apparatus and a positioning method according to a first embodiment of the present invention will be described with reference to FIGS. The projection exposure apparatus according to the present embodiment
This is a step-and-repeat type projection exposure apparatus that projects a pattern image on a reticle via a projection optical system in a reduced size and sequentially exposes the pattern image to each shot area on a photosensitive substrate.

First, a schematic configuration of the projection exposure apparatus according to the present embodiment will be described with reference to FIG. The illumination light IL from the illumination light source 2 for exposure is supplied to an ND filter 72 for adjusting the light amount.
Through. Illumination light IL includes, for example, i-line (wavelength λ = 365 nm) and g-line (λ
= 436 nm) or KrF excimer laser light (λ
= 248 nm), and ultraviolet light such as ArF excimer laser light and metal vapor laser light. Variable ND
The filter 72 has a configuration in which a plurality of ND filters of various different transmittances are arranged on a rotating plate, and can switch the transmittance for the illumination light IL in a plurality of stages, and usually controls the exposure amount at the time of exposure. In this embodiment, it is also used to adjust the amount of light incident on the light receiving units of the reticle alignment optical systems 48 and 50 or the photoelectric conversion element 32 of the stage sensor unit 26, which will be described later.

Illumination light I that has passed through the variable ND filter 72
L denotes a retractable mirror 54 provided between the variable ND filter 72 and an illumination optical system 4 including a collimator lens, a fly-eye lens (not shown), and the like.
The optical path can be changed depending on whether the optical path is inserted or retracted. When the retracting mirror 54 is retracted, the illumination light IL enters the illumination optical system 4 and is used as main illumination light IL toward the projection optical system PL. When the retracting mirror 54 is inserted into the optical path, the baseline measurement reference plate 10 is used. , Or as sub-illumination light IL ′ for measurement by the stage sensor 26. The retracting mirror 54 will be described later. Here, it is assumed that the retracting mirror 54 is in a retracted state (indicated by a broken line 54 'in FIG. 1), and that the light flux advances to the illumination optical system 4 as main illumination light IL.

The illumination light IL, which has been made substantially parallel by the illumination optical system 4, is bent substantially vertically downward by the dichroic mirror 6, and illuminates the reticle R with a uniform illuminance distribution. Here, the configuration of the light irradiation surface of the reticle R will be briefly described using the example of FIG. In FIG. 10, although not shown, a desired circuit pattern is drawn in the pattern drawing area 90 of the reticle R by an electron beam drawing apparatus or the like. A reticle alignment mark 9 for alignment, such as a cross-shaped alignment mark, formed by peeling off the chrome film is provided in a light-shielding region 92 which is shielded by a chrome film or the like outside the pattern drawing region 90.
4, 96 are arranged. The reticle alignment marks 94 and 96 are X
On a virtual straight line parallel to the axis,
Are provided at positions equidistant from the center.

The reticle R is mounted on a reticle stage (not shown). By moving the reticle stage in the X and Y directions while accurately controlling the amount of movement of the reticle stage by a laser interferometer (not shown), the reticle R
-It can be moved in the Y plane.
Note that, in FIG. 1, the Z axis is taken in a direction parallel to the optical axis AX of the projection optical system PL, and X in a plane perpendicular to the optical axis AX as shown in FIG.
The axis and the Y axis are set. In the following description,
Description will be made using this coordinate system.

The projection optical system PL focuses the light beam transmitted through the reticle R, and moves the reticle to a predetermined shot position on the photosensitive substrate W mounted on the substrate holder 8 on the substrate stage WST movable in the X and Y directions. An image of the R pattern is projected. This projection optical system PL is a telecentric optical system on both sides of the reticle R side (object side) and the photosensitive substrate W side (image side), and the projection magnification is, for example, 1/5. Further, the substrate holder 8 can hold the photosensitive substrate W by vacuum suction and move in the Z-axis direction to change the distance between the surface of the photosensitive substrate W and the projection optical system PL. The distance is measured by a focus sensor, and the surface of the photosensitive substrate W can be made to coincide with the image forming plane of the projection optical system PL.

The amount of movement of the substrate stage WST is measured by reflecting the laser light from the laser interferometer 42 on the reflecting mirror 40 fixed in the X and Y directions of the stage. The amount of movement of the substrate stage WST is
By performing the step-and-repeat operation of the substrate stage WST while accurately measuring in step 2, the circuit pattern of the reticle R is sequentially determined for a plurality of predetermined shot positions on the photosensitive substrate W placed on the substrate stage WST. Can be exposed.

When exposing the circuit pattern of the reticle R onto the photosensitive substrate W, the photosensitive substrate W
Therefore, the alignment mark 24 for alignment is formed on the photosensitive substrate W. Although a plurality of alignment marks are usually formed on the photosensitive substrate W, in the present embodiment, the alignment marks 24 are shown as representatives in the illustrated positions.

On the substrate stage WST, there is provided a baseline measurement reference plate 10 as an alignment reference plate for simultaneously performing reticle alignment and baseline measurement. The upper surface of the baseline measurement reference plate 10 can be adjusted in the Z-axis direction so as to coincide with the surface of the photosensitive substrate W. This baseline measurement reference plate 10
Will be described with reference to a plan view shown in FIG. 2 together with FIG. Above the baseline measurement reference plate 10, two reticle alignment reference marks 20 and 22 arranged in the X-axis direction used for alignment of the reticle R are provided. Further, a reticle alignment reference mark 2
A substrate alignment reference mark 12 for baseline measurement is formed at a position separated by a predetermined distance L in the vertical direction (that is, the Y direction) from the midpoint of the straight line connecting 0 and 22.

Reticle alignment reference mark 20,
Reference numeral 22 is formed as, for example, a frame-shaped light transmission pattern. The half mirror 16 is disposed below the reticle alignment reference mark 20, and the mirror 18 is disposed below the reticle alignment reference mark 22.
Is arranged. Then, from the light source 2, the projection optical system PL
Of the illumination light IL (main illumination light) toward the mirror 5
The sub-illumination light IL ′ obtained by reflection at 4 enters the half mirror 16 via the optical path A of the light guide system 56, which is not shown in detail, and is divided and divided. One of the lights is configured to enter the mirror 18. The sub-illumination light IL ′ reflected by the half mirror 16 and the mirror 18 illuminates the reticle alignment reference marks 20 and 22, respectively. The retracting mirror 54 used here, when illuminating the pattern drawing area of the reticle R with the illumination light IL, causes all of the illumination light IL from the light source 2 to enter the illumination optical system 4 as main illumination light.
The control device 5 retracts to the position indicated by the broken line 54 'in FIG.
2 is controlled.

In FIG. 1, the base stage measuring reference plate 10 is moved by a predetermined amount of the substrate stage WST so that the projection optical system P
In this state, the luminous flux of the sub-illumination light IL ′ transmitted through the reticle alignment reference mark 20 illuminates the reticle alignment mark 94 of the reticle R via the projection optical system PL. I can do it. The luminous flux of the sub-illumination light IL ′ transmitted through the reticle alignment reference mark 22 can illuminate the reticle alignment mark 96 of the reticle R via the projection optical system PL. The distance between the reticle alignment reference marks 20 and 22 is determined by the distance between the reticle alignment marks 94 and 96 and the projection optical system PL.
Is defined in advance from the projection magnification and the like.

The sub-illumination light IL ′ that illuminates the reticle alignment reference mark 20 and the reticle alignment mark 94 is vignetted above the reticle alignment mark 94 by the main illumination light IL that illuminates the pattern drawing area 90 of the reticle R. Is incident on the mirror 44 arranged at a position where no light is generated. The sub-illumination light IL ′ reflected by the mirror 44 enters the reticle alignment optical system 48. The reticle alignment optical system 48 detects the displacement of the superimposed image of the reticle alignment reference mark 20 and the reticle alignment mark 94.

On the other hand, the sub-illumination light IL ′ illuminating the reticle alignment reference mark 22 and the reticle alignment mark 96 is above the reticle alignment mark 96 and illuminates the pattern drawing area 90 of the reticle R with the main illumination light IL. Is incident on a mirror 46 arranged at a position where no vignetting occurs. The sub-illumination light IL ′ reflected by the mirror 46 enters the reticle alignment optical system 50. The reticle alignment optical system 50 detects a shift of a superimposed image of the reticle alignment reference mark 22 and the reticle alignment mark 96.

Based on the detected deviation of the superimposed images, the deviation of the center position of the reticle R from the center position between the reticle alignment reference marks 20 and 22 on the baseline measurement reference plate 10 is determined. Ends. In the reticle alignment, the retracting mirrors 58 and 60 for making the sub-illumination light used in the aerial image measurement described later enter from the output sides B and C of the light guide system 56 and reflect the sub-illumination light to the mirrors 44 and 46 include a mirror driving system
The dashed lines 58 ', 60' of FIG.
Is controlled by the control device 52 to evacuate from the position.

On the other hand, the substrate alignment reference mark 12
Are formed, for example, as a cross-shaped light reflection pattern. Baseline measurement reference plate 10 as shown in FIG.
Is located below the projection optical system PL and above the substrate alignment reference mark 12 and
A mirror 34 is arranged at a predetermined position outside the projection area L, and a mirror 36 is arranged outside the projection optical system PL. The substrate alignment optical system 14 is provided adjacent to the projection optical system PL, irradiates illumination light from an observation illumination system (not shown) to the substrate alignment reference mark 12 via mirrors 34 and 36, and reflects the reflected light. And the image of the substrate alignment reference mark 12 can be detected. The substrate alignment optical system 14 detects a deviation of the image of the substrate alignment reference mark 12 from an index in the substrate alignment optical system 14.

Then, the shift amount of the center position of the reticle R with respect to the center position between the reticle alignment reference marks 20 and 22 on the base line measurement reference plate 10 obtained by the reticle alignment, and the substrate alignment optical system 14 are used. Reference mark for substrate alignment 1
The reticle alignment reference marks 20 and 22 on the baseline measurement reference plate 10
From the center position between the reference marks 12 for substrate alignment.
The base line is obtained by adding the distance to the distance L to the base line.

The baseline measurement reference plate 1 described above
By using 0, the baseline measurement can be performed without moving the substrate stage WST,
Since no length measurement error occurs in the laser interferometer due to the movement of the substrate stage WST, it is possible to perform baseline measurement with higher accuracy than in the past. Further, in the present embodiment, in order to reduce a baseline error due to a shift in a reticle alignment mark forming position due to a reticle manufacturing error, a stage sensor unit 2 described below is used.
6 are provided. Details of the stage sensor section 26 will be described with reference to FIG. In FIG. 3, the substrate stage WST is moved by a predetermined amount and the stage sensor unit (photoelectric detecting unit) 26 is moved.
Is shown below the projection optical system PL.
In FIG. 3, components that are not related to the configuration and operation of the stage sensor unit 26, for example, the substrate alignment optical system 1
4 and mirrors 34 and 36 and retractable mirror drive system 10
Illustrations of 0, 102, etc. are omitted.

The stage sensor section 26 is used to acquire data for correcting the value of the baseline measured using the above-described baseline measurement reference plate 10. A reticle mark measuring substrate 28 above the stage sensor unit 26 is provided with a slit-shaped opening 30. The upper surface of the reticle mark measurement substrate 28 can be moved in the Z direction so as to coincide with the surface of the photosensitive substrate W. Below the stage sensor unit 26, a photoelectric conversion element 32 that receives light incident on the opening 30 is arranged.

The sub-illumination light IL 'obtained by reflecting the illumination light IL (main illumination light) from the light source 2 toward the projection optical system PL by the pull-in mirror 54 is shown as a block without detailed illustration. Through the optical path B of the light guiding system 56, the light enters the retracting mirror 60 moved between the reticle alignment optical system 50 and the mirror 46. Further, the sub-illumination light IL ′ is incident on the retracting mirror 58 moved between the reticle alignment optical system 48 and the mirror 44 via the optical path C of the light guide system 56. The two sub-illumination lights IL ′ reflected by the retracting mirrors 58 and 60 illuminate the reticle alignment marks 94 and 96 of the reticle R and enter the projection optical system PL, and the reticle marks of the stage sensor unit 26 on the substrate stage WST. An image is formed on the measurement substrate 28.

In FIG. 3, a spatial image of the reticle alignment mark 96 at the opening 30 is measured by the photoelectric conversion element 32 by the sub-illumination light IL ′ that illuminates the reticle alignment mark 96 by the retracting mirror 60 and the mirror 46. Is shown. The retracting mirrors 58 and 60 used here move between the reticle alignment optical systems 48 and 50 and the mirrors 44 and 46 as shown in FIG. 3 when the reticle alignment mark is detected by the stage sensor unit 26. At the time of baseline measurement using the baseline measurement reference plate 10, the sub-illumination light IL ′ transmitted through the reticle alignment reference marks 20, 22 and the reticle alignment marks 94, 96 is applied to the reticle alignment optical systems 48, 50. Is controlled by the control device 52 so as to retract to the position shown in FIG.

Here, the shape of the opening 30 of the stage sensor unit 26 and the stage sensor unit 2 will be described with reference to FIGS.
6 will be described. FIG. 5A is a plan view of the reticle mark measurement substrate 28 of the stage sensor unit 26 as viewed from the projection optical system PL side. FIG. 5A shows a configuration for describing the opening 30 on the upper surface of the reticle mark measurement substrate 28 and the spatial image 96 ′ in the X direction of the reticle alignment mark 96 of the reticle R. Accordingly, the shape of the opening 30 is composed of two slits extending in the Y and X directions for measuring the X direction and the Y direction, respectively. The display of the opening shape for aerial image measurement in the Y direction is performed. Is omitted.

The reticle alignment mark 96 of the reticle R is condensed by the projection optical system PL,
An image is formed on the surface of the reticle mark measuring substrate 28 near the opening 30 of the stage sensor unit 26 moved downward L. The width of the slit of the opening 30 is formed to be equal to or shorter than the width of the slit of the reticle alignment marks 94 and 96 of the reticle R in order to make the rising and falling of the output waveform of the photoelectric conversion element 32 steep. ing.

The substrate stage WST is finely moved in the X direction at a constant speed, and the opening 30 of the stage sensor 26 is scanned with respect to the spatial image 96 ′ of the reticle alignment mark 96 of the reticle R. 'Is received. The output waveform of the photoelectric conversion element 32 at this time is shown in FIG.
(B). In FIG. 5B, the horizontal axis represents the position of the substrate stage WST in the X direction, and the vertical axis represents the magnitude of the output of the photoelectric conversion element 32, and the light intensity in the width direction of the aerial image 96 ′. It is equivalent to the distribution. From the output waveform shown in FIG. 5B, the position of the reticle alignment mark including the imaging characteristics of the projection optical system PL can be obtained.

In FIG. 5B, the output signal I is compared with a predetermined reference level L1, and the output signal I and the reference level L are compared.
1, the position S1 of the substrate stage WST when it matches
S2 is measured by the laser interferometer 42. X of aerial image 96 '
The center position in the direction is obtained as a position c1 obtained by averaging S1 and S2.

From the waveform of FIG. 5B, for example, the contrast of the image can be obtained from the line width a1 cut at the predetermined reference level L1. Alternatively, the contrast may be obtained from the peak value b1. If the contrast is obtained while moving the stage sensor unit 26 in the direction of the optical axis of the projection optical system PL, it is also possible to know the focus position, the field curvature, and the like. Furthermore, astigmatism can be obtained by changing the direction of the pattern.

Next, referring to FIG.
Another configuration example will be described. The stage sensor unit 26 shown in FIG. 6A is characterized in that the magnifying optical system 70 is provided between the photoelectric conversion element 32 provided therebelow and the reticle mark measuring substrate 28 of the stage sensor unit 26. have.

In the example shown in FIG. 5, the width of the opening 30 is substantially equal to the width of the reticle alignment mark of the reticle R. In this case, the aerial image 96 ′ received by the photoelectric conversion element 32 becomes the width of the opening 30. Will be averaged.
Therefore, although the contrast can be compared from the obtained output waveform, the shape (profile) of the mark image of the reticle R can be obtained.
Is not sufficient to accurately obtain, and there is a possibility that a subtle difference in line width or image quality due to coma aberration or the like of the projection optical system PL cannot be known.

The stage sensor 26 shown in FIG.
Here, the magnifying optical system 70 is provided above the photoelectric conversion element 32. The image of the reticle alignment mark of the reticle R is formed on the opening 3 of the reticle mark measurement substrate 28.
After forming an image at the aperture plane of 0, the magnifying optical system 70
The light is enlarged by about 0 to 500 times and received by the photoelectric conversion element 32.

In this example, as shown in FIG. 6B, the shape of the reticle alignment mark is changed, and a reticle alignment mark having five slits in the X direction is used. FIG. 6C shows an output waveform obtained by the photoelectric conversion element 32. From this output waveform, the line width a2, the peak b2, and the center position c2 are obtained as in the case of FIG. In this example, by using the magnifying optical system 70 adjusted to a predetermined magnification, it is possible to obtain the output waveform of the received light image with high resolution, and to obtain the position of the mark image of the reticle R with higher accuracy. Become.

Next, still another configuration example of the stage sensor section 26 will be described with reference to FIGS. In the stage sensor section 26 shown in FIG. 6, the resolution of the light receiving system is improved by inserting the magnifying optical system 70 between the reticle mark measuring substrate 18 and the photoelectric conversion element 32. A problem arises when distortion or the like is included in 70. Further, when a heavy optical system such as the magnifying optical system 70 is mounted, the size of the substrate stage WST is reduced.
The weight increases and the controllability of the stage decreases. As a result, the size of the entire projection exposure apparatus increases.
In view of this point, in the present embodiment, a configuration in which good measurement can be performed without using a magnifying optical system will be described.

FIG. 7 is a plan view of the reticle mark measuring substrate 28 of the stage sensor section 26 of the present embodiment as viewed from the projection optical system PL side. An opening 30 having a rectangular opening surface is formed on the surface of the reticle mark measurement substrate 28. A mark image in the X direction is measured at an edge portion of the opening 30 extending in the Y direction, and a mark image in the Y direction is measured at an edge portion extending in the X direction. In this example, FIG.
A reticle alignment mark composed of five slits already shown in (b) is used, and FIG. 7 shows slits in both the X and Y directions of the reticle alignment mark.

The stage sensor 26 shown in FIG.
The width of the slit of the opening 30 in the stage sensor unit 26 shown in FIG. 7 is substantially equal to or smaller than the line width of the slit of the reticle alignment mark to be projected. Are formed sufficiently larger than the line width of the slits MX and MY of the reticle alignment mark of the reticle R. FIG. 7 shows the slits MX and MY of the reticle alignment mark of the reticle R.
Indicates a state where an image is formed in the vicinity of the opening 30.

When the substrate stage WST is finely moved at a constant speed, the aerial image of the mark MX enters the opening 30 from one edge of the opening 30 and exits from the edge at the other end. The distance (width) between both ends of the opening 30 is longer than the entire width of the slit MX in order to obtain a state in which all of the slit image at the front and the last of the slit MX are projected into the opening 30. . Similarly, the width of the opening 30 in the Y direction is longer than the entire width of the slit MY.

For example, when the spatial image of the slit MX is sequentially detected by the photoelectric conversion element 32 below the opening 30 by finely moving the substrate stage WST in the X direction at a constant speed, the output signal of the photoelectric conversion element 32 becomes as shown in FIG. The light intensity increases step by step,
Thereafter, the waveform becomes a waveform in which the light intensity gradually decreases. Since this output signal waveform is obtained by integrating the amount of light that has passed through the edge of the opening 30, if this waveform is differentiated, the slit M
The shape of the X image can be accurately reproduced. FIG. 9 shows the result of differentiating the waveform shown in FIG. Various information such as the position of the reticle alignment mark and the distortion of the projection optical system can be obtained from the differentiated waveform in the same manner as described with reference to FIGS. Similarly, the position of the image of the slit MY can be obtained in the Y direction.

The stage sensor unit 26 having the above configuration
The position information of the aerial images of the plurality of reticle alignment marks detected in the step (a) is sent to the baseline correction unit of the control device 52, and is used to correct the value of the baseline already measured using the baseline measurement reference plate 10. Can be In this embodiment and a second embodiment to be described later, the stage sensor 26 having the opening shape described with reference to FIGS. 7 to 9 is used.

The above is the outline of the configuration of the projection exposure apparatus according to the present embodiment. Next, a procedure for measuring a baseline using these configurations will be described. The procedure of the baseline measurement according to the present embodiment will be outlined. First, the baseline measurement using the baseline measurement reference plate 10 is performed. Next, a plurality of reticle alignment marks and information on the position of a predetermined reticle pattern are obtained using the stage sensor unit 26, and a correction value for a baseline correction is calculated from them to obtain a correction value for the baseline measurement from the reference plate 10 for baseline measurement. Correct the baseline value.

First, the procedure of the baseline measurement using the baseline measurement reference plate 10 will be described with reference to FIG. Substrate stage WST by laser interferometer 42
The control device 52 gives a command to a drive system (not shown) to move the substrate stage WST, and sets the baseline measurement reference plate 10 at a predetermined position in the projection area of the projection optical system PL while measuring the movement amount of the projection optical system PL.

On the other hand, a reticle stage (not shown) on which reticle R is mounted is also moved by a command from controller 52 while feeding back the amount of movement of the reticle stage from a laser interferometer (not shown). The reticle R is set at a predetermined position.

The illumination light IL from the illumination light source 2 for exposure is
The light passes through an ND filter 72 for adjusting the amount of light and is adjusted to a predetermined amount of light. The retracting mirror 54 is set in the optical path of the illumination light IL so that the light transmitted through the ND filter 72 is incident on the light guide system 56 in response to a drive command from the control device 52.

The sub-illumination light IL ′ incident on the light guide system 56
Travels along the optical path A, enters the half mirror 16 disposed inside the substrate stage WST, is split, the reflected light irradiates the reticle alignment reference mark 20 of the baseline measurement reference plate 10, and the transmitted light is the mirror. The reticle alignment reference mark 22 is radiated after being reflected at 18. 2
Each of the divided sub-illumination lights IL ′ enters the projection optical system PL and illuminates the reticle alignment marks 94 and 96 of the reticle R.

The light beam illuminating the reticle alignment reference mark 20 and the reticle alignment mark 94 is bent by the mirror 44 and enters the reticle alignment optical system 48. Reference mark 2 for reticle alignment
The light beam illuminating the reticle alignment mark 96 and the reticle alignment mark 96 is bent by the mirror 46 and enters the reticle alignment optical system 50. At this time, the retracting mirrors 58 and 60 are instructed by the control device 52 so that these light beams completely enter the reticle alignment optical systems 48 and 50.
Is evacuated from the optical path. At this time, ND
The filter 72 is reset by an instruction from the control device 52 so as to optimize the sensitivity of the light receiving elements provided in the reticle alignment optical systems 48 and 50 on which the sub illumination light IL ′ is incident.

The reticle alignment optical system 48 detects a pattern in which the reticle alignment reference mark 20 and the reticle alignment mark 94 overlap. The information of this pattern is sent to the control device 52, and the amount of displacement (X1, Y) of the reticle alignment mark 94 in the X and Y directions with respect to the reticle alignment reference mark 20 is determined.
1) is required. The reticle alignment optical system 50 also detects a pattern in which the reticle alignment reference mark 22 and the reticle alignment mark 96 overlap. The information of this pattern is sent to the control device 52, and the shift amount (X2, Y2) in the X and Y directions of the reticle alignment mark 96 with respect to the reticle alignment reference mark 22 is obtained.

On the other hand, the substrate alignment optical system 14 irradiates the substrate alignment apparatus reference mark 12 via the mirrors 36 and 34 and receives the reflected light. The received image of the pattern of the reference mark 12 for the substrate alignment apparatus is compared with the index scale built in the substrate alignment optical system 14 in the X and Y directions, and the position of the index scale of the substrate alignment optical system is determined from the origin. Are transmitted to the controller 52 in the X and Y directions (X3, Y3).

In the control device 52, the deviation amounts (X1, Y
1) and (X2, Y2), reticle alignment for determining the center position of reticle R with reference to the midpoint between reticle alignment reference marks 20 and 22 is performed. In addition, the control device 52 has reticle alignment reference marks 20 and 22 on the baseline measurement reference plate 10.
A predetermined distance L between the reference mark 12 and the substrate alignment apparatus reference mark 12 is stored, and a base line is calculated based on the distance L and the shift amounts (X1, Y1), (X2, Y2), and (X3, Y3). Desired.

As described above, in the measurement of the baseline according to the present embodiment, the alignment is performed using the mark provided on the baseline measurement reference plate 10 on the substrate stage WST. You will be able to measure the baseline without doing so. Therefore,
Baseline measurement that does not include any measurement error of the laser interferometer that measures the movement of the substrate stage WST can be performed.

Further, the light source of the sub-illumination light IL ′ used for the baseline measurement is the light source 2 of the main illumination light IL used for exposing the pattern of the reticle R on the photosensitive substrate W.
Therefore, there is an advantage that it is not necessary to consider the aberration of the projection optical system PL due to the difference in the wavelength of the illumination light.

Next, a procedure for correcting the measured baseline value will be described with reference to FIGS. First, in FIG. 3, the control device 52 gives a command to a drive system (not shown) to move the substrate stage WST, and sets the stage sensor unit 26 to a predetermined position in the projection area of the projection optical system. Further, the retracting mirrors 58 and 60 evacuated during the baseline measurement are moved by the command of the control device 52 to the reticle alignment optical systems 48 and 50 and the mirror 4.
4 and 46.

The illumination light IL from the illumination light source 2 for exposure is
The light passes through an ND filter 72 for adjusting the amount of light, is adjusted to a predetermined amount of light, and enters the retracting mirror 54. The retracting mirror 54 is set so that a light beam transmitted through the ND filter 72 is incident on the light guide system 56 in accordance with a drive command from the control device 52.

The sub-illumination light IL ′ incident on the light guide system 56
Travels along the optical path B and enters the retracting mirror 60 on the reticle alignment optical system 50 side. The light beam whose optical path is bent by the retracting mirror 60 is reflected by the mirror 46, illuminates the reticle alignment mark 96 of the reticle R, and enters the projection optical system PL. The pattern image of the reticle alignment mark 96 is formed on the surface of the reticle mark measurement substrate 28 of the stage sensor unit 26 by the projection optical system PL.

The control unit 52 measures the amount of movement from the laser interferometer 42 while controlling the reticle alignment mark 96.
The substrate stage WST is finely moved at a constant speed in the X direction until the aerial image enters from one edge of the opening 30 of the stage sensor unit 26 and exits from the other edge. In this way, the spatial image of the reticle alignment mark 96 is detected by the photoelectric conversion element 32 below the opening 30, and the output signal of the photoelectric conversion element 32 is taken into the control device 52, and is already shown in FIGS.
Reticle alignment mark 9 by the method described using
Find the position of 6. By performing the same operation in the Y direction, the X and Y positions of the reticle alignment mark 96 can be changed.
The position of the direction is determined. The ND filter 72 is
The control unit 52 optimizes the sensitivity of the photoelectric conversion element 32 of the stage sensor unit 26 that receives the sub illumination light IL ′.
Has been reset according to instructions from.

Next, the substrate stage WST is moved,
The reticle mark measurement substrate 28 is moved to a nearby area where the projected image of the reticle alignment mark 94 is formed.
Then, the position of the reticle alignment mark 94 is obtained by guiding the sub-illumination light IL ′ to the optical path C of the light guide system 56 and performing the same operation as described above.

As described above, the stage sensor 26
, The positions of the two reticle alignment marks 94 and 96 are obtained. As shown in FIG. 4, the positions of a plurality of predetermined patterns in the pattern drawing area of the reticle R are measured by the stage sensor unit 26. . In FIG. 4, components that are not related to the configuration and operation of the stage sensor unit 26, such as the substrate alignment optical system 14, the mirrors 34 and 36, and the retracting mirror drive systems 100 and 102 are omitted.

In FIG. 4, the retracting mirror 54 is retracted from the optical path of the illumination light from the illumination light source 2 for exposure in accordance with an instruction from the control device 52. The illumination light IL from the illumination light source 2 passes through an ND filter 72 for adjusting the amount of light, is adjusted to a predetermined amount of light, passes through the illumination optical system 4, is bent by the dichroic mirror 6, and draws a pattern on the reticle R. Illuminate the area. On the other hand, substrate stage WST moves so that a spatial image of a predetermined pattern in the pattern drawing area of reticle R is received by opening 30, and a reticle mark is positioned near a position where the spatial image of the predetermined pattern of reticle R is received. The measurement substrate 28 is moved.

The main illumination light IL for illuminating the pattern drawing area of the reticle R is incident on the projection optical system PL, and the pattern image of the reticle R is projected onto the reticle mark measurement substrate 28 of the stage sensor unit 26 by the projection optical system PL. Form an image.

The control device 52 measures the amount of movement from the laser interferometer 42 and
Substrate stage WST is finely moved at a constant speed in the X direction until an aerial image of a predetermined pattern enters from one edge of opening 30 of stage sensor section 26 and exits from the other edge. In this way, a spatial image of a predetermined pattern of the pattern image of the reticle R is detected by the photoelectric conversion element 32 below the opening 30, and an output signal of the photoelectric conversion element 32 is taken into the control device 52, and Find the position. By performing the same operation in the Y direction, the position of the predetermined pattern in the X and Y directions is obtained. ND
The filter 72 is reset by an instruction from the control device 52 so as to optimize the sensitivity of the photoelectric conversion element 32 of the stage sensor unit 26 that receives the main illumination light IL.

The above operation is repeated for a plurality of predetermined patterns in the pattern drawing area of the reticle R to obtain the pattern positions, whereby the measurement of the pattern positions using the stage sensor unit 26 is completed.

Next, the measurement by the stage sensor section 26 by the above-described operation and the storage of the 2
By correcting the center position of the reticle R already measured by the baseline measurement reference plate 10 based on the coordinate values of the positions of the two reticle alignment marks and the coordinate values of a plurality of predetermined pattern positions in the pattern drawing area. Perform baseline correction.

As a method of correcting the center position of the reticle R, for example, the least square method can be used. An error of the drawing position of each pattern based on the reticle manufacturing error is set as a parameter (including a magnification error due to aberration or the like of the projection optical system PL), and a design coordinate value (Xon) in a coordinate system having the center of the reticle R as an origin. , Yon) are actually measured coordinate values of (Xrn ′, Yr)
n ′). Here, n is the number of actually measured reticle alignment marks and predetermined patterns. The center of the reticle R is the reference plate 1 for baseline measurement.
Reticle alignment marks 94 and 9 already measured at 0
6 is the midpoint position.

Assuming that the position coordinates of the reticle alignment marks 94 and 96 and each pattern when the center position of the reticle R after correction is the origin is (Xrn, Yrn), the error component Exn in the X direction is Exn = Xrn'-X
rn, and the error component Eyn in the Y direction is Eyn = Yr
n'-Yrn. By obtaining the error parameter that minimizes the sum of squares E by the least squares method, it is possible to obtain the reticle alignment marks 94 and 96 and the position coordinates of each pattern determined using the center position of the corrected reticle R as the origin. it can. The difference between the center position of the reticle R after correction and the center position of the reticle R before correction among the obtained position coordinates is used as a correction value, and the value of the baseline already obtained by the baseline measurement reference plate 10 is used. , A corrected baseline value can be obtained.

As described above, in the measurement of the baseline according to the present embodiment, a plurality of marks or patterns are actually measured with respect to the measured baseline, and the center position of the reticle R due to a reticle manufacturing error is determined based on the measured values. Since the correction value for correcting the deviation is calculated and the value of the measured baseline is corrected, it is possible to obtain a very accurate baseline with few errors.

Further, in this embodiment, aerial images of a plurality of patterns including reticle alignment marks 94 and 96 for baseline measurement are formed on reticle mark measurement reference plate 2.
8 and accurately detect their positions, even if the reticle mark measurement reference plate 28 and the baseline measurement reference plate 10 are provided at distant positions on the substrate stage WST, measurement errors may occur. Corrections that do not occur can be made.

Next, a projection exposure apparatus and a positioning method according to a second embodiment of the present invention will be described with reference to FIGS. The projection exposure apparatus according to the present embodiment is characterized in that the illumination system has a stop 82 for limiting the size and shape of the illumination area of the reticle R.
Another feature is that the control device 52 controls the stop 82 to switch between illumination of the pattern drawing area of the reticle R and illumination of the reticle alignment mark. Further, it is characterized in that the control device 52 can switch the illumination by controlling the aperture 82 so as to enlarge the illumination area from the pattern drawing area of the reticle R to an area other than the pattern drawing area. doing.

A schematic configuration of the projection exposure apparatus according to the present embodiment will be described with reference to FIG. In FIG. 11, components having the same functions as those of the projection exposure apparatus according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. The characteristic configuration of the projection exposure apparatus according to the present embodiment will be described. I will mainly explain. First, in the projection exposure apparatus shown in FIG. 11, the retracting mirror 78 for changing the optical path of the illumination light from the illumination light source 2 is used to illuminate the reticle alignment reference marks 20 and 22 of the baseline measurement reference plate 10. It is set in the optical path of the illumination light only when light IL 'is obtained.

At the time of measurement by the stage sensor unit 26 for correcting the measured baseline, the sub-illumination light I
Instead of using L ′, a reticle blind 82 is provided between the reticle R and the dichroic mirror 6 and serves as an illumination field stop having, for example, four independently movable blades.

By enlarging the opening area of reticle blind 82 based on a command from control device 52,
The illumination area of the illumination light IL from the dichroic mirror 6 can be enlarged from the pattern drawing area of the reticle R to the area where the reticle alignment mark is formed. Further, reticle blind 82 having this configuration
Can shield the pattern drawing area of the reticle R so that only one of the four sides of the reticle R where the reticle alignment mark to be measured is formed is irradiated with illumination light. In this case, it is possible to reduce the incident energy on the projection optical system PL due to the illumination light, thereby reducing the fluctuation of the imaging characteristics that can occur in the projection optical system PL. Note that, even when the reticle blind 82 is fully opened, the incident energy can be reduced by selecting a filter having a low transmittance for the ND filter 72 in accordance with a command from the control device 52.

In the present embodiment, reticle blind 82 whose opening area can be changed so that the area where the reticle alignment mark is formed can be illuminated is used.
A reticle alignment optical system 48 from the reticle alignment reference marks 20 and 22 via the projection optical system PL;
The mirrors 74 and 76 that guide the sub-illumination light IL ′ to 50 can be retracted by driving the drive systems 104 and 106 according to a command from the control device 52. In FIG. 11, the state in which the mirrors 74 and 76 are retracted is shown by a solid line, and the sub-illumination light IL ′ is supplied to the reticle alignment optical system 4.
The positions at which the light is incident on 8, 50 are indicated by broken lines. Also in this figure, the illustration of the substrate alignment optical system 14 and the mirrors 34 and 36 is omitted.

Next, baseline measurement in the projection exposure apparatus according to the present embodiment will be described. First, reticle R used in the present embodiment will be described with reference to FIG. The reticle R shown in FIG. 12 has two reticle alignment marks 94 shown in FIG. 10 used in the first embodiment to correct a reticle manufacturing error.
In addition to 96, eight reticle alignment marks RM1 to RM8 are further formed. By using the reticle R, the reticle alignment marks 94 and 96 and RM1 to RM8 formed in advance can be measured without measuring a plurality of predetermined patterns in the pattern drawing area 90.
By simply measuring the position, the baseline can be corrected with high accuracy.

In the present embodiment, too, the measurement of the baseline using the baseline measurement reference plate 10 is the same as in the first embodiment. Therefore, a description thereof will be omitted, and a procedure for correcting the measured baseline will be described. In this example,
The case where the measurement is performed by enlarging the opening area of the reticle blind 82 will be described. First, in FIG. 11, the control device 52 gives a command to a drive system (not shown) to move the substrate stage WST, and sets the stage sensor unit 26 to a predetermined position in the projection area of the projection optical system. The control device 52
Drives the drive systems 104 and 106 to retract the mirrors 74 and 76 used for baseline measurement.

In FIG. 11, reticle blind 82
Is fully opened by the instruction of the control device 52, and the illumination light source 2
Is transmitted through the illumination optical system 4 after being adjusted to a predetermined light amount, is bent by the dichroic mirror 6, and is spread over the entire area of the reticle R, ie, the pattern drawing area. And illuminates an area including the reticle alignment marks 94 and 96 and RM1 to RM8. On the other hand, substrate stage WST moves so that one of the spatial images of the plurality of reticle alignment marks of reticle R is received at opening 30, and reticle mark measuring substrate 28 moves to a position near the position at which the spatial image is received. Let it.

Illumination light IL for illuminating a plurality of reticle alignment marks on reticle R is incident on projection optical system PL and projects a pattern image of the plurality of reticle alignment marks. The control device 52 measures the amount of movement from the laser interferometer 42 and moves the aerial image of the reticle alignment mark of the reticle R from one edge of the opening 30 of the stage sensor unit 26 until it exits from the other edge. Substrate stage WST is finely moved at a constant speed in the X direction. In this way, the spatial image of the reticle alignment mark is detected by the photoelectric conversion element 32 below the opening 30 and the photoelectric conversion element 3
2 is taken into the control device 52 to determine the position of the predetermined aerial image. By performing the same operation in the Y direction, the position of the predetermined pattern in the X and Y directions is obtained. The ND filter 72 includes a main illumination light I
The photoelectric conversion element 32 of the stage sensor unit 26 that receives L
Has been reset by an instruction from the control device 52 so as to optimize the sensitivity of.

By repeatedly performing the above operation on the plurality of reticle alignment marks on reticle R to determine their positions, the measurement of the positions of the plurality of reticle alignment marks using stage sensor unit 26 is completed.

Next, based on the coordinate values of the positions of the plurality of reticle alignment marks measured by the stage sensor unit 26 by the above-described operation and stored in the storage unit of the control unit 52, the reference plate 10 for baseline measurement is set. Is used to correct the baseline that has already been measured. As the method of calculating the correction value of the center position of the reticle R when correcting the baseline, for example, the least squares method can be used as described in the first embodiment. The processing in the correction is the same as that in the first embodiment, and the description is omitted.

In the above example, the reticle blind 8
2 was moved to enlarge the opening area and the measurement for baseline correction was performed. However, the blade was moved so that the pattern area of the reticle R was shielded from light, and the reticle alignment mark of the measurement target was Of course, it is also possible to perform measurement by switching the irradiation area of the illumination light for each existing side.

Also in the present embodiment, a plurality of marks or patterns are actually measured with respect to the measured baseline, and a correction value for correcting a shift of the center position of the reticle R due to a reticle manufacturing error is measured based on the measured values. Since the calculated and measured values of the baseline are corrected, an extremely high-accuracy baseline with few errors can be obtained. In addition, since aerial images of a plurality of reticle alignment marks including reticle alignment marks 94 and 96 for baseline measurement are measured by reticle mark measurement reference plate 28 and their positions are accurately detected, the reticle mark measurement Even if the reference plate 28 and the baseline measurement reference plate 10 are provided at positions separated from each other on the substrate stage WST, it is possible to perform correction without causing a measurement error.

Further, since the reticle blind is used, the light source used for measurement for baseline correction is the same as the light source 2 of the main illumination light IL used for exposing the pattern of the reticle R to the photosensitive substrate W. Therefore, there is an advantage that it is not necessary to consider the aberration of the projection optical system PL due to the difference in the wavelength of the illumination light.

Next, a projection exposure apparatus according to a third embodiment of the present invention and an alignment method thereof will be described with reference to FIGS.
This will be described with reference to FIG. The projection exposure apparatus according to the present embodiment integrates a reticle mark measurement reference plate with a baseline measurement reference plate to form an opening 30 for aerial image measurement.
Are provided together with the reticle alignment reference marks 20 and 22 and the substrate alignment reference mark 12 on the reference plate. FIG. 13 shows a schematic configuration of a projection exposure apparatus according to the present embodiment. The same as the projection exposure apparatus described in the second embodiment with reference to FIG. 11 except that the reticle mark measurement reference plate 10 and the baseline measurement reference plate 28 are integrated as described above. Configuration. Therefore, the same components are denoted by the same reference numerals, and description thereof will be omitted. Also in this figure, the substrate alignment optical system 14 and the mirrors 34, 3
The illustration of 6 is omitted.

In FIG. 13, in addition to the substrate alignment reference marks 12 and the reticle alignment reference marks 20 and 22, the base line measurement reference plate 10
A stage sensor unit 26 is provided at the center of the baseline measurement reference plate 10. The reference line 10 for baseline measurement also functions as a reference plate 28 for reticle mark measurement, and an opening 30 is formed in the center of the reticle mark measurement reference plate 28. A photoelectric conversion element 32 is provided below the opening 30. In FIG. 13, the area of the reticle mark measurement reference plate 28 is exaggerated for easy confirmation, but the entire surface of the baseline measurement reference plate 10 is finished to a predetermined flatness. It should be noted that in the display of FIG.
Are provided on the front side of the paper surface with respect to the substrate alignment reference plate 12, but are not shown.

FIG. 14 is a plan view of the baseline measurement reference plate 10 according to the present embodiment. Above the baseline measurement reference plate 10, two reticle alignment reference marks 20 and 22 arranged in the X-axis direction used for alignment of the reticle R, and a midpoint of a straight line connecting the reticle alignment reference marks 20 and 22. The opening 30 of the stage sensor unit 26 is formed around a position separated by a predetermined distance L in the vertical direction (that is, Y direction) from the center. Further, a substrate alignment reference mark 12 for baseline measurement is formed at a further distance L therefrom.

Next, baseline measurement in the projection exposure apparatus according to the present embodiment will be described. The reticle R used in the present embodiment has a configuration in which a plurality of reticle alignment marks used in the second embodiment as shown in FIG. 12 are formed in a light-shielding band around a circuit pattern area. That is, in addition to the two reticle alignment marks 94 and 96, eight more reticle alignment marks RM1 to RM8 are formed.

Also in this embodiment, the measurement of the baseline using the baseline measurement reference plate 10 is the same as in the first and second embodiments. Therefore, the description thereof is omitted, and the procedure of measuring the spatial image position of the reticle alignment mark for correcting the measured baseline will be described. Also in this example, a case will be described in which the opening area of the reticle blind 82 is measured while being enlarged. First, the control device 52
Drives the drive systems 104 and 106 to retract the mirrors 74 and 76 used for baseline measurement. Further, since the stage sensor unit 26 is integrated with the baseline measurement reference plate 10, the opening 30 of the stage sensor unit 26 is already positioned below the projection optical system PL when the measurement of the baseline is completed. Therefore, control device 52 can shift to the next processing without moving substrate stage WST.

In FIG. 13, reticle blind 82
Is fully opened, the illumination light IL from the illumination light source 2 is adjusted to a predetermined light amount, and the entire area of the reticle R, that is, the pattern drawing area and the reticle alignment marks 94, 96,
The area including RM1 to RM8 is illuminated. On the other hand, substrate stage WST moves so that one of the spatial images of the plurality of reticle alignment marks of reticle R is received by opening 30 and functions as reticle mark measuring substrate 28 near the position where the spatial image is received. The baseline measurement reference plate 10 to be moved is moved.

Illumination light IL for illuminating a plurality of reticle alignment marks on reticle R is incident on projection optical system PL and projects a pattern image of the plurality of reticle alignment marks. The control device 52 measures the amount of movement from the laser interferometer 42 and moves the substrate stage in the X direction until the spatial image of the reticle alignment mark of the reticle R enters from one edge of the opening 30 and exits from the other edge. W
ST is finely moved at a constant speed. In this way, the spatial image of the reticle alignment mark is detected by the photoelectric conversion element 32 below the opening 30, and the output signal of the photoelectric conversion element 32 is taken into the control device 52 to determine the position of the predetermined spatial image.
By performing the same operation in the Y direction, the position of the predetermined pattern in the X and Y directions is obtained.

When measuring the aerial image of the reticle pattern, in the present embodiment, among the plurality of reticle alignment marks of reticle R, the aerial image measurement of reticle alignment marks 94 and 96 is not performed, and other reticle alignment marks 94 and 96 are not measured. The above operation is sequentially repeated for the eight reticle alignment marks RM1 to RM8 to determine their positions. This point is significantly different from the aerial image measurement according to the above-described first and second embodiments.

In the first and second embodiments, when measuring a plurality of reticle alignment marks or patterns, the reticle alignment marks 94 and 96 are also measured by the stage sensor section 26 and the baseline measurement reference plate. 10 is arranged at a position distant from the substrate stage WST. In other words, as long as the two are arranged separately, the stage sensor unit 26 and the baseline measurement reference plate 10 have different coordinate systems. Considering the case where the reticle alignment marks 94 and 96 are included, the reticle alignment marks 94 and 96 measured by the reticle alignment reference marks 20 and 22 on the baseline measurement reference plate 10 and the reticle alignment marks 94 and 96 measured by the stage sensor unit 26 are considered. With reference to the aerial image position, it is necessary to match the aerial image positions of the other plurality of reticle alignment marks measured by the stage sensor unit 26 with the coordinate system of the baseline measurement reference plate 10.

However, since the stage sensor section 26 according to the present embodiment is provided integrally with the baseline measurement reference plate 10, the coordinate system in measurement is the same. Therefore, even if the reticle alignment marks 94 and 96 are not measured by the stage sensor section 26, the position of the aerial image of another reticle alignment mark can be measured with reference to the coordinate system of the baseline measurement reference plate 10.

In the present embodiment, the reason that the stage sensor section 26 does not measure the aerial images of the reticle alignment marks 94 and 96 is that the reticle alignment marks 94 and 96 as shown in FIG. The difference is the mark shape of the reticle alignment marks RM1 to RM8. The reticle alignment marks 94 and 96 are obtained by observing an image of superposition with the reticle alignment reference mark on the baseline measurement reference plate 10 using the image pickup devices of the reticle alignment optical systems 48 and 50, and displacing the superimposed images. The aim is to get the quantity. Therefore, reticle alignment marks 94, 9
The pattern No. 6 needs to have a relatively simple cross shape or the like so that the amount of displacement of the superimposed image can be easily observed.

On the other hand, marks or patterns used for position measurement as an aerial image are X and Y, like the reticle alignment marks RM1 to RM8 illustrated in FIG.
When a shape in which a plurality of slit-like patterns are formed in the directions is used, as described with reference to FIGS. 7 to 9, the output signal of the obtained aerial image is subjected to processing such as differential operation to improve measurement accuracy. This is advantageous in that it can be performed. However, in the case of reticle alignment marks 94 and 96 composed of about one or two slits in the X or Y direction, even if the aerial images are measured, the measurement accuracy of those aerial images is relatively low. That doesn't make much sense.
Rather, the increase in the number of unnecessary measurement points of the aerial image causes a decrease in throughput. Therefore, the reticle alignment marks 94 and 96 are not measured in the aerial image measurement of the reticle alignment mark according to the present embodiment.

Although not shown, reticle alignment marks 94 and 96 other than the projection exposure apparatus according to the present embodiment are illuminated with illumination light different from the exposure light.
A baseline measurement reference plate provided integrally with a projection exposure apparatus having an alignment mechanism configured so that the other reticle alignment marks are illuminated with the same illumination light as the exposure light, in the present embodiment. It is also effective to use 10. The stage sensor unit 26 on the substrate stage WST as described in the first and second embodiments
When the reticle alignment mark 9 and the reference line 10 for baseline measurement are arranged at a distance from each other,
Since it is essential to measure the aerial images of the reticle alignment marks 94 and 96, the wavelength of the illumination light and the wavelength of the exposure light differ from each other. As a result, the accuracy of the aerial image measurement decreases. On the other hand, when using the baseline measurement reference plate 10 integrally provided with the tage sensor unit,
Since the spatial images of the reticle alignment marks 94 and 96 are not measured, there is no problem even if the illumination light of the reticle alignment marks 94 and 96 is different from the exposure light.

Next, based on the positions of the plurality of reticle alignment marks measured and stored by the stage sensor unit 26 by the above-described operation, the baseline measurement reference plate 1 is used.
The baseline is corrected by correcting the center position of the reticle R already measured by 0. The correction value can be obtained by using, for example, the least squares method in the same manner as described in the first embodiment, and the processing is the same as in the first embodiment, and thus the description is omitted.

Note that the baseline measurement reference plate 10 is
Although formed of a material having a very small coefficient of thermal expansion, the stage sensor unit 26 measures the baseline measurement in consideration of the possibility of minute deformation due to the temperature change of the substrate stage WST and the length of exposure light irradiation time. Reticle alignment reference plates 20, 2
It is preferable that the center of the opening 30 of the stage sensor unit 26 be located at the center between the midpoint of the substrate 2 and the reference mark 12 for substrate alignment.

Also in the present embodiment, a plurality of marks or patterns are actually measured with respect to the measured baseline, and a correction value for correcting a shift of the center position of the reticle R due to a reticle manufacturing error is determined based on the measured values. Since the calculated and measured values of the baseline are corrected, an extremely high-accuracy baseline with few errors can be obtained. Also, without measuring the reticle alignment marks 94 and 96 for baseline measurement, the aerial images of the other plurality of reticle alignment marks can be measured by the reticle mark measurement reference plate 28 to accurately detect their positions. Therefore, more accurate baseline measurement can be performed.

The present invention is not limited to the above embodiment, but can be variously modified. For example, in the above embodiment, a variable ND filter is used as a mechanism for adjusting the amount of illumination light, but for example, a pupil plane (reticle R) of the projection optical system PL is used.
Of course, a pupil filter driven by the control device 52 may be arranged on the Fourier transform plane for the light source and the light amount may be adjusted so as to block a part of the illumination light passing through the pupil plane.

In the above-described embodiment, the present invention is applied to a so-called stepper type projection exposure apparatus for exposing the reticle R and the exposure substrate W while keeping the reticle R and the exposure substrate W stationary. The photosensitive substrate W through the system
The present invention is also applied to a so-called step-and-scan type scanning projection exposure apparatus in which the pattern of the reticle R is sequentially exposed on the photosensitive substrate W by projecting onto the reticle R and scanning the photosensitive substrate W in synchronization with each other. Can be applied.

Although the reticle blind in the second embodiment has four blades, it is of course possible to use a reticle blind in which the opening area is changed by, for example, two L-shaped blades. It is.

In the second embodiment, the reticle R having two conventional reticle alignment marks shown in FIG. 10 is used, and the same as the baseline measurement described in the first embodiment. Of course, it is also possible to correct a baseline value by measuring a plurality of predetermined patterns in the pattern drawing area.

[0112]

As described above, according to the present invention, a plurality of marks or patterns are actually measured with respect to a measured baseline, and a correction value for correcting a reticle manufacturing error is calculated based on the actually measured values. Since the measured baseline value is corrected, it is possible to obtain a very accurate baseline with few errors. Further, according to the present invention, the positions of a plurality of reticle alignment marks including a reticle alignment mark for baseline measurement are measured by a reticle mark measurement reference plate as aerial image position measurement means. Even when the reference plate and the baseline measurement reference plate are separated from each other on the substrate stage, measurement can be performed without error.

The reticle mark measurement reference plate is integrated with the baseline measurement reference plate so that the aerial image measurement opening 30 is provided on the reference plate together with the reticle alignment reference mark and the substrate alignment reference mark. This eliminates the need to measure the aerial image of the reticle alignment mark for baseline measurement in the aerial image position measurement, so that the measurement accuracy can be further improved.

[0114]

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a projection exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a plan view illustrating a configuration of a baseline measurement reference plate.

FIG. 3 is a diagram illustrating a state where a reticle alignment mark is observed by a stage sensor unit of the projection exposure apparatus according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a state where a mark in a circuit pattern drawing area of a reticle is observed by a stage sensor unit of the projection exposure apparatus according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating an opening shape of a stage sensor unit and an output signal from the stage sensor unit.

FIG. 6 is a diagram showing another opening shape and an output signal of the stage sensor unit.

FIG. 7 is a view showing still another opening shape of the stage sensor unit.

FIG. 8 is a diagram showing an output signal according to still another opening shape of the stage sensor unit.

FIG. 9 is a diagram showing an output signal according to still another opening shape of the stage sensor unit.

FIG. 10 is a plan view of a reticle used in the first embodiment of the present invention.

FIG. 11 is a view showing a schematic configuration of a projection exposure apparatus according to a second embodiment of the present invention.

FIG. 12 is a plan view of a reticle used in the second and third embodiments of the present invention.

FIG. 13 is a diagram showing a schematic configuration of a projection exposure apparatus according to a third embodiment of the present invention.

FIG. 14 is a plan view illustrating the configuration of a baseline measurement reference plate used in a projection exposure apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

2 illumination light source 4 illumination optical system 6 dichroic mirror 8 substrate holder 10 baseline measurement reference plate 12 substrate alignment reference mark 14 substrate alignment optical system 20, 22 reticle alignment reference mark 26 stage sensor unit 28 reticle mark measurement reference plate Reference Signs List 30 opening part 32 photoelectric conversion element 40 reflecting mirror 42 laser interferometer 44, 46 mirror 48, 50 reticle alignment optical system 52 controller 54, 58, 60, 78 retracting mirror 72 ND filter 82 reticle blind 90 pattern drawing area 92 light shielding area 94, 96, RM1 to RM8 Reticle alignment mark AX Optical axis of projection optical system PL IL illumination light (main illumination light) IL 'sub illumination light R reticle PL projection optical system W photosensitive substrate WST substrate stage

Claims (8)

[Claims] An illumination system for illuminating a reticle on which a plurality of reticle alignment marks and an exposure pattern are formed; a projection optical system for projecting the reticle pattern onto a substrate; A substrate stage movable two-dimensionally within a projection plane of the optical system; a substrate alignment optical system for observing a predetermined mark on the substrate; and a reticle provided on the substrate stage, the reticle and the substrate alignment An alignment reference plate on which a reference mark used for measurement of a relative position with respect to an optical system is formed; provided on the substrate stage; detecting a spatial image of the plurality of reticle alignment marks by the projection optical system; Spatial image position measuring means for measuring each position of the image; and projection position information of the plurality of aerial images measured by the spatial image position measuring means. Based on the correction means for correcting the value of the relative position of the reticle and the substrate alignment optical system obtained using the reference mark of the alignment reference plate, illumination of the exposure pattern drawing area, A control system for controlling the illumination system so as to switch the illumination of the reticle alignment mark. 2. An illumination system for illuminating a reticle on which a plurality of reticle alignment marks and an exposure pattern are formed; a projection optical system for projecting the reticle pattern onto a substrate; A substrate stage movable two-dimensionally within a projection plane of the optical system; a substrate alignment optical system for observing a predetermined mark on the substrate; and a reticle provided on the substrate stage, the reticle and the substrate alignment An alignment reference plate on which a reference mark used for measurement of a relative position with respect to an optical system is formed; provided on the alignment reference plate, detecting a spatial image of the plurality of reticle alignment marks by the projection optical system; A spatial image position measuring means for measuring each position of the aerial image; and each projection of the plurality of aerial images measured by the aerial image position measuring means. Correction means for correcting a value of a relative position between the reticle and the substrate alignment optical system obtained using the reference mark of the alignment reference plate based on position information; and illumination of the exposure pattern drawing area. And a control system for controlling the illumination system so as to switch illumination of the reticle alignment mark. 3. The projection exposure apparatus according to claim 2, wherein said spatial image position measuring means is provided substantially at the center of said alignment reference plate. 4. The projection exposure apparatus according to claim 1, wherein said substrate alignment optical system detects a position of said substrate alignment reference mark without passing through said projection optical system. Characteristic projection exposure apparatus. 5. The projection exposure apparatus according to claim 1, wherein the illumination system has a main illumination system for illuminating the exposure pattern drawing area, and a light source identical to the main illumination system. And a sub-illumination system for illuminating an area other than the exposure pattern drawing area, wherein the control system switches between the main illumination system and the sub-illumination system. 6. The projection exposure apparatus according to claim 1, wherein the illumination system has a stop for limiting a size and a shape of an illumination area of the reticle, and the control system includes the stop. Controlling the illumination of the exposure pattern drawing area and the illumination of the reticle alignment mark area. 7. The projection exposure apparatus according to claim 6, wherein the control system controls the stop so as to enlarge an illumination area from the exposure pattern writing area to an area other than the exposure pattern writing area. A projection exposure apparatus, wherein 8. A reticle having a plurality of reticle alignment marks and an exposure pattern formed thereon is illuminated, and a reticle pattern is projected onto a substrate stage by a projection optical system. The reticle is provided separately from the projection optical system. Determining a relative position between the substrate alignment optical system and the reticle based on a reference mark provided on the substrate stage, detecting a spatial image of the plurality of reticle alignment marks by the projection optical system, and A position alignment method comprising: measuring each position of an image; and correcting the value of the relative position based on information of each of the measured projection positions of the plurality of spatial images.