JPH09252043A - Positioning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new pre-alignment method which carries out alignment in a non-contact manner and is interchangeable with a conventional pre- alignment method where pins are used. SOLUTION: A wafer W1 is placed on the center-up of a wafer stage, the image of the periphery of the wafer 1 is picked up in observation visual fields 50a, 51a, and 52a and measured, and the position and posture of the wafer W1 placed on the center-up are obtained from the measurement result. Thereafter, the center-up is driven to rotate the wafer W1 to make a pre-alignment of it so as to make the position and posture of the wafer W1 equal to a pre- alignment result obtained by a conventional pre-alignment method where pre- alignment is carried out by making pins P1 , P2 , and P3 bear against the wafer W1 . Thereafter, the center-up is made to descend to place the wafer W1 in a substrate holder, and the wafer W1 is fixed by vacuum suction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for positioning a photosensitive substrate such as a semiconductor wafer or a glass plate on a substrate stage.

[0002]

2. Description of the Related Art A projection exposure apparatus such as a stepper is used for manufacturing semiconductor elements and liquid crystal display elements. In a projection exposure apparatus, a reticle or photomask coated with a photosensitive agent such as resist (hereinafter referred to as reticle)
In order to transfer the pattern formed above onto a predetermined area of a photosensitive substrate (hereinafter referred to as a wafer) such as a wafer or a glass plate with high accuracy, it is necessary to align the reticle and the wafer with high accuracy. .

Therefore, this type of projection exposure apparatus incorporates a fine alignment optical system for photoelectrically detecting an alignment mark formed on the wafer to align the reticle and the wafer. As the fine alignment method, an LSA (Laser Step Aligmnent) method in which a laser beam is applied to an alignment mark in a dot array on a wafer and the mark position is detected using light diffracted or scattered by the mark, a halogen lamp FIA (Field Image Alignment) method of image processing and measuring the image data of the alignment mark imaged by illuminating with light having a wide wavelength band such as a light source, or the frequency is set to the diffraction grating alignment mark on the wafer. 2 generated by irradiating slightly changed laser light from 2 directions
LIA (Laser Interferometric Alf) that measures the position of the alignment mark from the phase by interfering two diffracted lights
ingnment) method. Also, the alignment method is
TTL (Thr that measures the position of the wafer through the projection optical system
rough the lens) method, a projection optical system and a reticle are used to measure the positional relationship between the reticle and the wafer.
rough the leticle) method and the off-axis method that directly measures the position of the wafer without going through the projection optical system.

According to the fine alignment optical system, by detecting the positions of at least two points of the wafer placed on the wafer stage, the positions in the translational direction and the rotational direction can be detected with extremely high accuracy. However, since this fine alignment optical system has a narrow projection range of the spot light that illuminates the alignment mark, when there is no alignment mark near the projection optical axis of the spot light, the wafer is moved greatly to search a wide area. Therefore, it takes a lot of time to search the alignment mark. In order to reduce the search time, the alignment mark of the wafer must be within the field of view of the fine alignment optical system when the wafer is placed on the wafer stage. Therefore, a pre-alignment device having a rotary table is provided in the wafer transfer path, the position of the wafer including the rotation direction is regulated with respect to the wafer transfer device by the pre-alignment device, and a pre-alignment mechanism having pins on the wafer stage is provided. Is provided, and when the wafer is placed on the wafer stage, the wafer is brought into contact with the pins for pre-alignment.

FIG. 15 is an explanatory view of a conventional pre-alignment mechanism for a wafer having a linear notch, that is, an orientation flat, on a part of the outer circumference. On the wafer stage ST, three fixed pins 91, 92, 93 and one moving pin 94 are provided in a predetermined positional relationship. The moving pin 94 is movable in the one-dimensional direction indicated by the arrow.

The wafer W1 having the orientation flat portion FP has a fixing pin 91 having two FP portions.
The wafer is placed on the wafer holder WH of the wafer stage ST by a wafer transfer mechanism (not shown) so that it is located in the vicinity of 92 and its circumferential portion is located in the vicinity of the remaining one fixing pin 93. Subsequently, the wafer W1 is uniquely positioned on the wafer stage ST and pre-aligned by pressing the wafer W1 against the three fixed pins 91, 92, 93 in an oblique direction by the moving pin 94. After the pre-alignment, the wafer W1 is vacuum sucked and fixed to the wafer holder WH.

FIG. 16 is an explanatory view of a conventional pre-alignment mechanism for a notch wafer in which a V-shaped notch, that is, a notch is provided on a part of the outer circumference. Two fixing pins 9 are arranged on the wafer stage ST in a predetermined positional relationship.
6 and 97, and one movable pin 98 that is movable in one-dimensional direction with respect to the fixed pins 96 and 97 as shown by arrows.

The notch wafer W2 is moved by a wafer transfer mechanism (not shown) so that the notch portion NP is located near the moving pin 98 and the circumferential portion on the opposite side of the NP portion is located near the fixing pins 96 and 97. It is placed on the wafer stage ST. Subsequently, the moving pin 98 is set to the NP of the wafer W2.
The wafer W2 is moved to the wafer stage ST by engaging with the portion and pressing it toward the other two fixing pins 96 and 97.
It is uniquely positioned on top and pre-aligned. After pre-alignment, the wafer W2 is placed on the wafer holder W.
It is vacuum-adsorbed to H and fixed.

[0009]

In the conventional pre-alignment mechanism, with the wafer placed on the wafer holder of the wafer stage as described above, the outer peripheral portion of the pre-alignment mechanism is mechanically attached to the fixed pin and the movable pin provided on the stage. The pre-alignment was carried out by contacting with. However, the mechanical contact between the wafer and the pins causes a part of the resist applied on the wafer to peel off and become fine particles and scatter.
The scattered fine particles adhere to the wafer surface and reticle,
This has hindered the pattern formation on the wafer, and has been a cause of lowering the device manufacturing yield. Therefore, in order to prevent fine particles from being scattered from the wafer by the prealignment operation, it is desirable to perform the prealignment without contact.

By the way, the radius of the wafer is ± 0.1 mm.
There is some manufacturing error. According to the conventional pre-alignment mechanism using contact pins, even wafers having such individual differences in shape are uniquely positioned and pre-aligned for each wafer on the wafer stage.

When developing a new non-contact type pre-alignment mechanism, there is a possibility that the projection exposure apparatus equipped with the new mechanism will be used together with the projection exposure apparatus equipped with the conventional pre-alignment mechanism using contact pins. In consideration of the above, it is desirable that the new non-contact type pre-alignment mechanism is compatible with the conventional pre-alignment mechanism using the contact pin, and both can obtain the same pre-alignment result.

The present invention has been made in view of the above problems, and provides a novel prealignment method that can be performed in a non-contact manner and is compatible with a conventional prealignment method using a pin. The purpose is to do.

[0013]

In order to achieve the above object, according to the present invention, a photosensitive substrate such as a wafer or a glass plate is placed on the center-up of a substrate stage (wafer stage). An image of the outer peripheral portion of the substrate is picked up and an image is measured, and the position and orientation of the photosensitive substrate placed on the center-up is obtained from the result of the image measurement. Then, the center-up is driven to move the photosensitive substrate to perform pre-alignment so that the position and orientation of the photosensitive substrate are the same as the pre-alignment result obtained by the pre-alignment method performed by pressing the conventional pins. After that, lower the center up and place the photosensitive substrate on the substrate holder.
Vacuum adsorption and fixation.

That is, according to the present invention, the positioning for positioning the photosensitive substrate having a substantially circular shape and a linear notch (orientation flat) on a part of the outer circumference on the substrate stage movable in the two-dimensional direction. In the method, the photosensitive substrate is conveyed to a predetermined transfer point (center-up) above the substrate stage, the outer peripheral portion of the photosensitive substrate is imaged at the transfer point, and two of the three virtual pins in a predetermined relative positional relationship are taken. A first position of the three virtual pins when the virtual pins of the book contact the orientation flat portion and the remaining one virtual pin contacts the circular portion and simultaneously contacts the outer peripheral portion of the photosensitive substrate. And a step of obtaining a rotation angle and a translational displacement amount necessary to match the first position with the second position of the three virtual pins set on the substrate stage. And it is characterized in that it comprises a step of rotating only the rotation angle photosensitive substrate obtained.

The three virtual pins in the first method correspond to the three fixed pins in the conventional prealignment mechanism, and the relative positional relationship of the three virtual pins is used in the conventional prealignment mechanism. It is the same as the relative positional relationship of the three fixing pins. The second positions of the three virtual pins set on the substrate stage are the same as the positions of the three fixed pins on the substrate stage in the conventional pre-alignment mechanism. In other words, this first method is 3 for the photosensitive substrate placed on the center-up.
The position (first position) at which the fixed pin of the book can be brought into close contact with a predetermined portion of the photosensitive substrate while maintaining its relative positional relationship is obtained by image measurement, and is the first position and the position of the original fixed pin. From the positional relationship between the second position and the second position, the rotation angle and the translation amount of the photosensitive substrate necessary for prealignment are obtained. It is clear that the pre-alignment of the photosensitive substrate according to this first method gives the same result as the pre-alignment using the conventional pin.

Further, according to the present invention, a positioning for positioning a substantially circular photosensitive substrate having a linear notch (orientation flat portion) on a part of its outer periphery on a substrate stage movable in a two-dimensional direction. In the method, the photosensitive substrate is conveyed to a predetermined transfer point (center-up) above the substrate stage, the outer peripheral portion of the photosensitive substrate is imaged at the transfer point, and the rotation angle of the photosensitive substrate is obtained based on the orientation flat portion direction. The process and the position of one of the two intersections of the straight line parallel to the orientation flat portion and separated from the orientation flat portion by a predetermined distance and the outer periphery of the photosensitive substrate are obtained, and the position of the intersection point and the direction of the orientation flat portion Step of obtaining the translational displacement of the photosensitive substrate based on It is characterized in that comprising the step of rotating the optical substrate.

In the second method, the direction of the orientation flat portion is first obtained by measuring the image. Subsequently, the above-mentioned three virtual pins having the same relative positional relationship as the three fixed pins in the conventional pre-alignment mechanism are set on the center substrate while maintaining the relative positional relationship. Assuming that the virtual pin is in close contact with the given portion, the coordinates of the virtual pin that contacts the circumferential portion are obtained. Then, the rotation angle of the photosensitive substrate required for pre-alignment is obtained from the direction of the orientation flat portion, and the translation amount of the photosensitive substrate required for pre-alignment is calculated from the rotation angle of the photosensitive substrate and the coordinates of the virtual pin in contact with the circumferential portion. Ask. This second
It is clear that the pre-alignment of the photosensitive substrate by the method described in (1) gives the same result as the pre-alignment using the conventional pin.

Further, according to the present invention, a positioning for positioning a substantially circular photosensitive substrate having a V-shaped notch portion (notch portion) at a part of its outer periphery on a substrate stage movable in a two-dimensional direction. In the method, the photosensitive substrate is conveyed to a predetermined transfer point (center-up) above the substrate stage, the outer peripheral portion of the photosensitive substrate is imaged at the transfer point, and the position of the notch is determined, and two steps at predetermined intervals are performed. The virtual pin and one virtual movable pin that can move in the one-dimensional direction defined with respect to the two virtual pins position the virtual movable pin in the notch and contact the remaining two virtual pins with the circular portion. And a step of obtaining the positions of the three virtual pins when simultaneously contacting the outer peripheral portion of the photosensitive substrate, and a step of obtaining the rotation angle and the translational position deviation amount of the photosensitive substrate from the positions of the three virtual pins. It is characterized in that comprises a step of rotating only the photosensitive substrate rotation angle because obtained.

The third method relates to a pre-alignment method for a photosensitive substrate having a notch portion. The two virtual pins and the one virtual movable pin at predetermined intervals correspond to the two fixed pins and one moving pin in the conventional pre-alignment mechanism, respectively. The distance between the two virtual pins is the same as the distance between the two fixed pins used in the conventional pre-alignment mechanism, and the relationship between the one virtual movable pin and the two virtual pins is the same as in the conventional case. This is the same as the relationship between the movable pin and the two fixed pins in the pre-alignment mechanism. That is, in the third method, the two fixed pins and the one moving pin with respect to the photosensitive substrate placed on the center-up position of the photosensitive substrate while maintaining the relationship between the pins in the conventional pre-alignment mechanism. The position at which a predetermined portion can be brought into close contact is obtained by image measurement, and the rotation angle and translation amount of the photosensitive substrate necessary for prealignment are obtained based on the position information. It is clear that the pre-alignment of the photosensitive substrate according to the third method provides the same result as the pre-alignment using the conventional pin.

In any of the first, second, and third methods, the rotation of the photosensitive substrate required for prealignment is
This can be done by rotating the center up. In addition, pre-alignment can be performed by setting the translational position shift amount as an offset for the two-dimensional movement of the substrate stage.

According to the present invention, the pre-alignment for placing the photosensitive substrate on the substrate holder of the substrate stage with high precision can be performed in a non-contact manner. Therefore, it is possible to prevent the generation of fine particles due to the resist or the like of the photosensitive substrate coming into contact with the pins and peeling, which has been a problem in the past.
Moreover, compatibility with the conventional pre-alignment mechanism using pins can be maintained.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an example of a projection exposure apparatus according to the present invention. Under illumination light IL from an illumination system IA including a light source including a mercury lamp, an excimer laser, a fly-eye lens, a condenser lens, and the like,
The pattern on the reticle 1 is reduced to, for example, 1/4 or 1/5 via the projection optical system 3 and projected onto each shot area of the wafer 6 coated with the photoresist. In FIG. 1, Z is parallel to the optical axis AX of the projection optical system 3.
Take the axis and in the plane perpendicular to the Z-axis, parallel to the plane of the paper in Fig. 1, X
The axis is taken as the Y axis perpendicular to the plane of FIG.

The reticle 1 is held on a reticle stage 32 mounted on a reticle stand 31. The reticle stage 32 is configured to be capable of translational movement in the XY plane and rotation in the θ direction (rotational direction) by a reticle drive system (not shown). Reticle stage 3
A moving mirror 33 is installed at the upper end of 2 in both the X and Y directions. The moving mirror 33 and a laser interferometer 34 fixed on the reticle mount 31 cause the reticle stage 32 to move.
The positions in the X and Y directions are always detected with a resolution of, for example, about 0.01 μm, and at the same time, the rotation angle of the reticle stage 32 is also detected. The measurement value of the laser interferometer 34 is sent to the stage control system 16, and the stage control system 16 controls the reticle drive system on the reticle mount 31 based on the information. The stage control system 16 supplies information on the measurement value of the laser interferometer 34 to the central control system 18, and the central control system 18 controls the stage control system 16 based on the information.

On the other hand, the wafer 6 is vacuum-sucked and held on a wafer holder 30 fixed to a sample table 29 on the X stage 11. The sample table 29 is a Z tilt drive unit (three members that are moved in the Z direction in this example) for correcting the position and tilt of the wafer 6 in the optical axis AX direction (Z direction) of the projection optical system 3. Supported by 10),
The Z tilt drive unit 10 is fixed on the X stage 11. The X stage 11 is placed on the Y stage 12, and the Y stage 12 is placed on the wafer base 14.
Each of them can be moved in the X and Y directions via a wafer stage drive system (not shown). An L-shaped movable mirror 13 is fixed to the upper end of the sample table 29,
Coordinates and rotation angles of the sample table 29 in the X and Y directions are detected by the movable mirror 13 and the laser interferometer 17 arranged so as to face the movable mirror 13.

The measurement value of the laser interferometer 17 is sent to the stage control system 16, and the stage control system 16 controls the wafer stage drive system based on the information. Further, information on the measurement values of the laser interferometer 17 is supplied from the stage control system 16 to the central control system 18, and the central control system 18 controls the stage control system 16 based on the information. A wafer transfer device 39 (see FIG. 2) for transferring the wafer 6 is arranged near the wafer stage, and a wafer transfer mechanism is provided in the wafer stage as described later.

This projection exposure apparatus is provided with, for example, a TTL alignment sensor 4 and two off-axis alignment sensors 5a and 5b for aligning the reticle 1 and the wafer 6. At the time of alignment, these alignment sensors 4, 5a, 5
The position of the alignment mark or the position of a predetermined pattern formed on the wafer 6 is detected by either of the steps b), and the pattern and the reticle formed in the previous process are constantly formed in each shot area of the wafer 6 based on the detection result. Align it exactly with the pattern above. The detection signals from these alignment sensors 4, 5a, 5b are the alignment control system 1
5, the alignment control system 15 is controlled by the central control system 18. A reference mark member 43 having the same height as the surface of the wafer 6 is fixed on the sample table 29, and a mark serving as a reference for alignment is formed on the surface of the reference mark member 43.

As described above, the stage control system 16 and the alignment control system 15 are controlled by the central control system 18, and the central control system 18 comprehensively controls the entire projection exposure apparatus to perform the exposure operation in a fixed sequence. Is performed.

Near the wafer-side end of the projection optical system 3,
Three off-axis two-dimensional image processing devices 5
0, 51, 52 are arranged. These image processing devices 50, 51 and 52 respectively capture an image of the edge portion of the outer peripheral portion of the wafer when the wafer is carried to the loading position (delivery position) above the wafer holder 30 as described later. Is. Image processing device 5
The image pickup signals from 0, 51 and 52 are the alignment control system 1
5 is supplied. The alignment control system 15 calculates the lateral deviation error and the rotation error of the wafer at the transfer position from the supplied image pickup signal. Image processing device 50,
The arrangement of 51 and 52 and the method of calculating the error will be described later.

Next, the wafer transfer system and the wafer transfer mechanism on the wafer stage will be described with reference to FIG. The wafer stage is a general term for the wafer holder 30, the sample table 29, the Z tilt drive unit 10, the X stage 11, the Y stage 12, and the wafer base 14.

FIG. 2A is a plan view of the structure around the wafer transfer system and the wafer stage, and FIG. 2B is a side view thereof. In FIGS. 2A and 2B, a wafer transfer device 39 for transferring the wafer is arranged above the wafer stage in the −X direction. The wafer transfer device 39 includes the wafer arms 21 and 2 arranged in series in the X direction.
2, a slider 23 for sliding the wafer arms 21 and 22 to a predetermined position, and the wafer arm 2
It is composed of an arm drive system (not shown) that drives the motors 1 and 22. Further, the slider 23 is installed independently of the exposure apparatus main body, so that vibration when the slider 23 is driven is not transmitted to the exposure apparatus main body side. Each of the two wafer arms 21 and 22 has a U-shaped flat plate portion, and the wafer is placed on the upper surface thereof. With these two wafer arms 21 and 22, a wafer after exposure can be unloaded (carried out), and at the same time, the next wafer can be loaded.

That is, the wafer arms 21 and 22 are moved along the slider 23 to the loading position where the wafer is transferred to the wafer stage system based on a command from the loader controller 24, and the wafer 6 exposed by the wafer arm 22 is exposed. Carry out. After that, the wafer 6 to be exposed next is moved to the wafer stage by the wafer arm 21 and placed on the center-up 38. FIG.
(B) shows a state in which the exposed wafer 6 a is placed on the wafer arm 22 on the slider 23 and the wafer 6 is transferred from the wafer arm 21 to the tip of the center-up 38.

The center-up 38 is supported by a telescopic mechanism 35 provided on the X stage 11, has three spindle portions 38a to 38c which are loosely fitted in the openings of the sample table 29 and the wafer holder 30, and the telescopic mechanism 35. Of the three spindles 38a to 38c by moving the vertical direction (Z direction) of the
Moves the wafer up and down to transfer the wafer. 3
Vacuum suction holes are provided at the tips of the spindles 38a to 38c of the book, and these tips move to a height at which they can be delivered to and from the wafer arms 21 and 22 when the wafer is delivered to the wafer holder. When the wafer holder 30 is placed on the wafer 30, the wafer holder 30 is moved to a position lower than the surface of the wafer holder 30. Further, the spindle parts 38a to 38
Center up 3 by vacuuming the tip of c
The wafer is prevented from shifting when 8 is moved up and down.

The extension / contraction mechanism 35 is rotatably supported on the XY plane about the central axis 35z of the X stage 1.
The rotary drive system 36 provided on the drive shaft 1 engages with the drive shaft 37 that rotates and can be rotated to a desired angle by a command from the central control system 18 that controls the rotary drive system 36. The rotation system including the rotation control system 36, the drive shaft 37, and the expansion / contraction mechanism 35 has a sufficient angle setting resolution, and can rotate the wafer 6 with an accuracy of 20 μrad, for example.

The attitude control of the wafer in the wafer transfer system will be described with reference to FIG. FIG. 3A shows a turntable 60 provided in the wafer transfer system. FIG.
The wafer arm 21 shown in FIG.
The upper wafer 6 is transferred to the center-up 38 of the wafer stage. In the vicinity of the turntable 60, a light projecting portion 61 a for irradiating the outer peripheral portion of the wafer 6 with a slit-shaped light beam 63.
And an eccentric sensor 61 including a light receiving portion 61b that receives and photoelectrically converts the light beam that has passed through the outer peripheral portion of the wafer 6, and the detection signal S1 from the light receiving portion 61b is transmitted by the central control system 1.
8. When the turntable 60 is rotated while sucking and holding the wafer 6, the width of the wafer 6 passing through the eccentricity sensor 61 changes due to the eccentricity of the wafer 6 and the presence of the notch portion (orientation flat portion or notch portion). Light beam 6 received by the part 61b
The light quantity of 3 changes.

FIG. 3B shows the detection signal S1 output from the light receiving section 61b. The detection signal S1 is sinusoidal with respect to the rotation angle φ of the turntable 60, and changes so as to have a high level in the portion 62 corresponding to the cutout portion. The central control system 18 obtains the rotation angle φ ₀ when the notch is located at the center of the eccentricity sensor 61 and the eccentricity amount of the wafer 6 from the detection signal S1 and the rotation angle φ of the turntable 60, The turntable 60 is stopped so that the cutout portion is oriented in a predetermined direction. Further, the central control system 18 adjusts the position of the wafer sample table 29 when the wafer 6 is received at the loading position, based on the eccentricity information.

Next, the image processing apparatus 50 will be described with reference to FIG. In FIG. 4, illumination light in a wavelength band in which the photoresist coated on the wafer 6 is weakly sensitive is focused on one end of the light guide 57 from a light source 58 such as a lamp or a light emitting diode. Then, the illumination light emitted from the other end of the light guide 57 passes through the collimator lens 56, the half prism 54 and the objective lens 53, and the wafer 6 at the loading position on the tips of the three spindle portions 38a to 38c. Irradiation is applied to the outer edge portion. The reflected light from the edge portion is the objective lens 53,
Two-dimensional C through half prism 54 and imaging lens 55
The light enters the image pickup device 59 such as a CD, and an image of the edge portion of the wafer 6 is formed on the image pickup surface of the image pickup device 59.

Although only the image processing apparatus 50 has been described here, the other image processing apparatuses 51 and 52 have the same configuration. The image pickup signals from the respective image pickup devices 50, 51, 52 are supplied to the alignment control system 15, and the alignment control system 15 obtains the edge position of the detection target of the wafer 6 from the image pickup signal and performs the arithmetic processing described later to perform the preprocessing. The rotation angle and the translational movement amount of the wafer required for alignment are calculated.

FIG. 5 is a diagram showing another configuration example of the image processing apparatus. In FIG. 5, the illumination light emitted from a light source such as a lamp or a light emitting diode (not shown) in a wavelength band in which the photoresist has a weak sensitivity is focused on one end of the light guide 72. The illumination light emitted from the other end of the light guide 72 is bent by the deflection mirror 73, and the sample table 29
It is injected through the opening 75 on the upper surface of a. Sample table 29
The wafer holder 30a arranged on a is provided with a cutout portion 74 for passing the illumination light that has passed through the opening 75 thereof. Illumination light that has passed through the opening 75 and the cutout 74 is applied to the outer peripheral edge of the wafer 6 at the loading position on the tips of the three spindles 38a to 38c. Then, the illumination light passing near the edge portion passes through the objective lens 53a and the imaging lens 55a and forms an image of the edge portion on the image pickup surface of the image pickup device 59 such as a two-dimensional CCD. Instead of guiding the illumination light from the light source to the opening 75 of the sample table 29a by the light guide 72, a light source such as a light emitting diode may be directly arranged at the position of the opening 75 of the sample table 29a.

Subsequently, for each of the wafer having the orientation flat portion and the wafer having the notch portion, the rotation angle and the translational displacement of the wafer are obtained from the measurement results by the image processing devices 50, 51 and 52, and the pre-alignment processing is performed. The procedure will be described in detail.

[Processing Procedure 1] First, using the wafer layout diagrams shown in FIGS. 6 and 7 and the flow chart of FIG. 8,
A processing procedure for pre-aligning the wafer W1 having the orientation flat portion (FP) will be described.

FIG. 6 is a view for explaining the positional relationship between the three fixing pins 91, 92, 93 of the conventional pre-alignment mechanism shown in FIG. As shown, the pins 91 and 92 are in contact with the orientation flat portion FP of the wafer W1 at contact points 91a and 92a, and the pin 93 is in contact with the circumferential portion of the wafer W1 at contact point 93a. The straight line SL is a straight line which passes through the point 93a and is parallel to the straight line connecting the points 91a and 92a. The point CP is a point where a perpendicular line drawn from the point 92a toward the straight line SL intersects with the straight line SL. At this time, the distance between the point 92a and the point CP is a,
The distance between the point 93a and the point CP is b, and the points 91a and 92a are
Let the distance between them be c. These values a, b, c
Is a design value determined by the arrangement of the pins 91, 92, 93.

FIG. 7 shows the observation fields 50a, 51a, 52a on the wafer stage and the wafer W1 held on the center-up 38 by the three image processing devices 50, 51, 52 provided in the projection exposure apparatus shown in FIG. Shows the positional relationship of. As shown in FIG. 7, two observation visual fields 50 by the image processing devices 50 and 51 are provided on the FP portion of the wafer W1.
a and 51a are set, and the remaining one observation visual field 52a by the image processing device 52 is set on the circumference of the wafer W1. The positions of the observation fields of view 50a, 51a, 52a are predetermined as device constants.

In FIG. 7, P ₁ , P ₂ and P ₃ represent virtual pins. These virtual pins P ₁ , P ₂ , P ₃ have the same positional relationship as the fixing pins 91, 92, 93 of the conventional pre-alignment mechanism shown in FIGS. 6 and 15, but actually they are on the wafer stage. It does not exist.

First, a straight line expression representing the FP portion of the wafer W1 is obtained by an image processing apparatus having an observation visual field in the FP portion of the wafer W1 (S801). This is obtained by the following [equation 2] obtained from the measurement result by the image processing device 51 having the observation visual field 51a and the linear equation of the following [equation 1] obtained from the measurement result by the image processing device 50 having the observation visual field 50a.
By averaging the linear equations of, it can be obtained as in [Equation 3]. Of course, it is possible to use [Equation 1] or [Equation 2] instead of [Equation 3].

[0045]

[Equation 1] Y = A ₁ X + B ₁

[0046]

[Formula 2] Y = A ₂ X + B ₂

[0047]

## EQU3 ## Y = AX + B A = (A ₁ + A ₂ ) / 2, B = (B ₁ + B ₂ ) / 2 Next, the measurement result by the image processing device 52 having the observation visual field 52a in the circumferential portion of the wafer W1. From the above, the formula of the circle representing the circumference of the wafer W1 is calculated as in the following [Equation 4] (S).
802).

[0048]

Equation 4] ^{_{(X-X 0) 2 +}} (Y-Y 0) 2 = R 0 2 followed by a distance a towards the center of the wafer W1 parallel to the line represented by Formula 3 The straight line L ₃ is calculated as in [Equation 5] (S803).

[0049]

[Formula 5] Y = AX + B + a (1 + A ² ) ^1/2 Next, the intersection point P between the circumferential portion of the wafer represented by [Formula 4] and the straight line L ₃ represented by [Formula 5].
₃ (X ₃ , Y ₃ ) is calculated by the following equation (Equation 6) (S80
4).

[0050]

## EQU6 ## X ₃ = [X ₀ −AC + [(X ₀ −AC) ² − (1 + A ² )
(X ₀ ² + C ² −R ₀ ² )] ^1/2 ] / (1 + A ² ) Y ₃ = AX ₃ + B + a (1 + A ² ) ^1/2 However, C = B + a (1 + A ² ) ^1/2 −Y _0th order , the intersection point P distance from ₃ points on the straight line L ₃ in b P ₄ (X _4,
Y ₄₎ and the point P ₅ on the straight line L ₃ distance from the point P ₄ is in c (X _5,
Y ₅ ) is calculated by the following equation (Equation 7) (S805).

[0051]

Equation 7] _{X 4 = X 3 -b / (} 1 + A) Y 4 = AX 3 -Ab / (1 + A) + B + a (1 + A 2) 1/2 X 5 = X 3 - (b + c) / (1 + A) Y 5 = _{AX 3 -A (b + c)} / (1 + A) + B + a (1 + A 2)
^1/2 Next, an intersection point P ₂ (X ₂ , Y ₂ ) between the straight line L ₂ passing through P ₄ and perpendicular to the straight line L ₃ and the FP portion, and a straight line L ₁ passing through P ₅ and perpendicular to the straight line L ₃ The intersection point P ₁ (X ₁ , Y ₁ ) with the FP portion is obtained by the following equation (Equation 8) (S806).

[0052]

[Formula 8] X ₂ = X ₄ + aA / (1 + A ² ) ^1/2 Y ₂ = AX ₄ + aA ² / (1 + A ² ) ^1/2 + B X ₁ = X ₅ + aA / (1 + A ² ) ^1/2 Y ₁ = AX ₅ + aA ² / (1 + A ² ) ^1/2 + B The coordinates P ₁ (X ₁ , Y ₁ ), P ₂ (X ₂ , Y ₂ ), thus obtained,
P ₃ (X ₃ , Y ₃ ) is the pin 9 of the conventional pre-alignment mechanism.
1, 92, and 93 are coordinates of points that contact the wafer W1. Then, points P ₁ (X ₁ , Y ₁ ), P
The rotation angle θ at the positions of ₂ (X ₂ , Y ₂ ), P ₃ (X ₃ , Y ₃ ) and the coordinates P _C (X _C , Y _C ) of the virtual center of the wafer are obtained (S807).
Coordinates P ₁ (X ₁ , Y ₁ ), P ₂ (X ₂ ,
Y ₂ ), P ₃ (X ₃ , Y ₃ ), and the coordinates of the position of the fixed pin P ₁ '(x ₁ ,
y ₁ ), P ₂ ′ (x ₂ , y ₂ ), and P ₃ ′ (x ₃ , y ₃ ) have the following [Equation 9] relationship.

[0053]

X _j = X _j cos θ−Y _j sin θ + X _C y _j = X _j sin θ + Y _j cos θ + Y _C (j = 1,2,3) The rotation angle θ calculated by the above formula [Formula 9] and the imaginary wafer W1 Prealignment of the wafer W1, that is, rotation and position correction of the wafer W1 is performed based on the coordinate position P _C (X _C , Y _C ) of the center. The pre-alignment of the wafer W1 in the rotation direction is
The rotation system including the rotation control system 36, the drive shaft 37, and the expansion / contraction mechanism 35 rotationally drives the center-up 38 of the wafer stage by -θ (S808).

The pre-alignment in the translational direction is
This is done by offsetting the positions of the X and Y stages by the amount of the shift. That is, the position P _C ′ (X _C ′, Y _C ′) of the virtual center after the rotation of the wafer is defined as the following [X ₀ , Y ₀ ) with the coordinates of the center up rotation center in the pre-alignment coordinate system as Since it becomes like (Equation 10), this (X _C ',
The value of Y _C ') is used as an offset in the X and Y directions (S
809).

[0055]

X _C '= (X _C −X ₀ ) cos θ + (Y _C −Y ₀ ) sin θ + X ₀ Y _C ′ = − (X _C −X ₀ ) sin θ + (Y _C −Y ₀ ) cos θ + Y ₀

[Processing Procedure 2] Next, another processing procedure for pre-aligning the wafer W1 having the orientation flat (FP) portion will be described with reference to the wafer layout shown in FIG. 9 and the flowchart in FIG. An example will be described.

In FIG. 9, the wafer W1 drawn by a solid line
Represents a wafer before pre-alignment held on the center-up of the wafer stage, and a wafer drawn by an imaginary line represents a wafer that has been pre-aligned by a conventional pre-alignment mechanism using pins. The positional relationship between the fixed pins 91, 92, 93 and the virtual pins P ₁ , P ₂ , P ₃ is the same as that described with reference to FIGS. 6 and 7. In this example, the wafer W1 has an angle θ from the pre-alignment state.
Only rotated, virtual center of the wafer misaligned by X _C X direction, the coordinate misaligned only Y _C in the Y direction P _C (X _C,
Y _C ) and is held on the center up.

First, as an initial value, the wafer rotation angle θ =
0, X _C = 0 and Y _C = 0 are set as the position of the virtual center of the wafer, and the counter is set to n = 1 (S1001).
Next, after adding 1 to the counter n (S1002), the points P ₁ (X ₁ , Y ₁ ) and P ₂ (X ₂ , Y ₂ ) at which the virtual pins P ₁ and P ₂ contact the orientation flat portion FP. Is expressed by the following formula
1] is obtained (S1003). However, in [Equation 11], 2d ₀ = c and h = a.

[0059]

X ₁ = −d ₀ cos θ + h sin θ + X _C Y ₁ = −d ₀ sin θ−h cos θ + Y _C X ₂ = d ₀ cos θ + h sin θ + X _C Y ₂ = d ₀ sin θ−h cos θ + Y _C Next, from the Y axis through the point P ₁ , θ Inclined straight line L ₁ and point P ₂
A straight line L ₂ that passes through and is inclined by θ from the Y axis is obtained from the following equation (Equation 12) (S1004).

[0060]

## EQU12 ## Line L ₁ : (X-X ₁ ) =-tan θ (Y-Y ₁ ) Line L ₂ : (X-X ₂ ) =-tan θ (Y-Y ₂ ) Next, the observation visual fields 50a and 51a. By the straight lines L ₁ and F
An intersection P ₁ (X ₁ , Y ₁ ) with the P portion and an intersection P ₂ (X ₂ , Y ₂ ) with the straight line L ₂ and the FP portion are obtained by image processing (S1005),
Based on the coordinates of the intersection points P ₁ and P ₂ obtained by the image processing, the θ value is corrected by the following equation (Equation 13) (S1006).

[0061]

Θ = tan ⁻¹ [(Y ₂ −Y ₁ ) / (X ₂ −X ₁ )] Next, a straight line L ₃ parallel to the straight lines P ₁ P ₂ and a distance h from the wafer center is obtained ( S1007). This straight line L ₃ is represented by the following [Equation 14].

[0062]

Equation 14] straight _{L 3: (Y 2 -Y 1} ) X- (X 2 -X 1) Y-X 1
_{Y 2 + X 2 Y 1 +} h [(Y 2 -Y 1) 2 - (X 2 -X 1) 2] 1/2 = 0 Next, the line L ₃ and the wafer circumference of intersection P ₃ (X _3, Y ₃ ) is obtained by image processing (S1008), and the coordinate P of the virtual center of the wafer is obtained.
_C (X _C , Y _C ) is calculated by the following equation (Equation 15) (S100
9).

[0063]

X _C = X ₃ −R ₀ cos θ Y _C = Y ₃ −R ₀ sin θ Steps 1002 to 1009 are repeated again (S10
10), the rotation angle θ of the wafer W1 and the coordinate P of the virtual center
_{Find C} (X _C , Y _C ). Pre-alignment of the wafer W1 is performed based on the rotation angle θ and the coordinate P _C (X _C , Y _C ) of the virtual center thus obtained. The pre-alignment of the wafer W1 in the rotation direction is performed by the rotation control system 36, the drive shaft 37, and the extension / contraction mechanism 3.
The center-up unit 38 is rotationally driven by-[theta] by a rotating system composed of 5 (S1011).

The pre-alignment in the translation direction is
This is done by offsetting the positions of the X and Y stages by the amount of the shift. That is, the position P _C ′ (X _C ′, Y _C ′) of the virtual center after the rotation of the wafer is expressed by the following [Numbers] with the coordinates of the center-up rotation center in the pre-alignment coordinate system being (X ₀ , Y ₀ ). 16], so this (X _C ', Y _C ')
Is used as an offset in the X and Y directions (S101
2).

[0065]

X _C '= (X _C −X ₀ ) cos θ + (Y _C −Y ₀ ) sin θ + X ₀ Y _C ′ = − (X _C −X ₀ ) sin θ + (Y _C −Y ₀ ) cos θ + Y ₀

[Processing Procedure 3] Next, using the wafer layout diagrams shown in FIGS. 11 and 12, the flowchart of FIG. 13 and the notch position explanatory diagram shown in FIG. 14, a pre-process of the wafer W2 having a notch portion is performed. A processing procedure for alignment will be described.

FIG. 11 shows observation visual fields 50a, 51a, 52a on the wafer stage by the three image processing devices 50, 51, 52 provided in the projection exposure apparatus shown in FIG.
Shows the positional relationship of the wafer W2 held on the center-up 38. As shown in FIG. 11, the notch portion NP
The observation field of view 50a of the image processing device 50 is set on the
Observation fields 51a and 52a of the image processing devices 51 and 52 are set on the circumference of the wafer W2 opposite to the NP portion. The positions of the observation fields of view 50a, 51a, 52a are predetermined as device constants.

In FIG. 11, P ₁ and P ₂ represent virtual fixed pins, and P _N represents virtual moving pins. These virtual pins P ₁ , P ₂ , P _N have the same positional relationship as the fixed pins 96, 97 and the moving pin 98 of the conventional pre-alignment mechanism shown in FIG. 16, but actually exist on the wafer stage. It doesn't. The distance between the virtual pins P ₁ and P ₂ is 2d ₀ =
2 ^1/2 R ₀ .

FIG. 12 is an explanatory view showing a state in which the virtual pins P ₁ , P ₂ , P _N are in contact with the wafer W2 held on the center-up by rotating by an angle θ with respect to the pre-alignment coordinate system. Is. The vertices sandwiching a right angle of a right-angled isosceles triangle whose hypotenuse is a line segment connecting the virtual pins P ₁ and P ₂ are defined as a virtual center P _C of the wafer W2, and the position P _N between the virtual center P _C and the notch portion NP (notch portion) Let R be the distance between the positions of the virtual locating pin center O that contacts the two edges of the NP.

First, as initial values, θ = 0 is set for the rotation angle θ of the wafer, R = R ₀ is set for the radius R of the wafer, and the counter n is set to n = 1 (S1301). Next, the position P _N (X _N, Y _N ) of the notch portion NP is obtained from the measurement result of the image processing device 50 (S1302).

A method of detecting the position P _N (X _N, Y _N ) of the notch portion NP will be described with reference to FIG. FIG. 14 (a)
[FIG. 7] is an enlarged view of a notch portion NP of wafer W2. The conventional pre-alignment mechanism uses the wafer W2 on the wafer holder.
For positioning the notch NP with a predetermined diameter d.
The columnar positioning pin was pressed against. Therefore, the standard of the shape of the notch portion NP has been determined based on the shape of the positioning pin. Therefore, from the image data from the image processing device 50 that includes the notch portion NP in the observation visual field 50a, a virtual positioning pin 64 having a diameter d that contacts two edges of the notch portion NP is assumed, and the center of the virtual positioning pin 64 is assumed. The X and Y coordinates of O are detected. The position of the center O of the virtual positioning pin 64 is defined as the position P _N (X _N, Y _N ) of the notch portion NP.

As another method, as shown in FIG. 14B, the coordinates of the intersection P of the two edges 65a and 65b of the notch portion NP and one edge 65b are determined from the image data in the observation visual field 50a. There is also a method of obtaining the coordinates of the intersection point 65c with the outer circumference of the wafer. In this case, the intersection 65c is virtually provided on the edge 65a and the intersection 65d at the target position,
A triangle whose vertices are three intersections P, 65c, 65d is assumed. Then, by proportional distribution with respect to the distance between the intersection points 65c and 65d, which is the base, the position of the triangle whose distance between the bases is d is obtained, and the center of the base of the triangle is taken as the center O, and the X coordinate and Y of this center O The coordinates may be obtained and used as the position P _N (X _N, Y _N ) of the notch portion NP. Returning to the processing step, next, 1 is added to the counter n (S130
3) Then, the coordinate P _M (X _M , Y _M ) of P _M is obtained from the following [Equation 17] (S1304).

[0073]

Equation 17] _{X M = X N - (R} + d 0) sinθ Y M = Y N + (R + d 0) cosθ Next, as represented by the following [Equation 18], the vertical as the P _M P _M P _N Of the straight line L and the circumference of the wafer obtained by measurement by the image processing devices 51 and 52, P ₁ (X ₁ ,
Y ₁ ), P ₂ (X ₂ , Y ₂ ) are calculated (S1305).

[0074]

## EQU16 ## Straight line L: (Y−Y _M ) = A (X−X _M ) A = − (X _M −X _N ) / (Y _M −Y _N ). Then, according to the following [Formula 19], Midpoint P of intersection points P ₁ and P _2
M '(X _M ', Y _M ') is calculated (S1306).

[0075]

X _M '= (X ₁ + X ₂ ) / 2 Y _M ' = (Y ₁ + Y ₂ ) / 2 Then, using the coordinate values of the points P _M and P _M ', Two
0], the value of the rotation angle θ is changed (S1307).

[0076]

[Equation 20] θ → θ + (X _M −X _M ') / [R ₀ (1 + A ² ) ^1/2 ] Next, the distance D between the points P ₁ and P ₂ is calculated, and the following [Equation 21] is obtained.
In accordance with this, the value of R is changed from the value of design value D ₀ = 2d ₀ (S1308).

[0077]

[Formula 21] R → R + (D−D ₀ ) / 2 Next, the coordinate P _C (X _C , Y _C ) of the virtual center of the wafer W2 is obtained based on the following [Formula 22] (S1309).

[0078]

Equation 22] _{X C = X N -Rsinθ Y C} = Y N + Rcosθ Repeat step 1309 from step 1303 once again (S1310), the coordinates P _C (X _C of the rotation angle θ and virtual center,
Y _C ). Pre-alignment of the wafer W2 is performed based on this value. The pre-alignment of the wafer W2 in the rotation direction is performed by the rotation control system 36, the drive shaft 37, and the extension / contraction mechanism 35.
The center-up 38 is rotationally driven by -θ by the rotation system consisting of (S1311).

The pre-alignment in the translation direction is
This is done by offsetting the positions of the X and Y stages by the amount of the shift. That is, the position of the virtual center of the rotated wafer _{P C '(X C',} Y C ') , the following [Equation coordinates of the center-up rotation center of the pre-alignment coordinate system as (X _0, Y ₀₎ 23], so this (X _C ', Y _C ')
Is used as an offset in the X and Y directions (S131).
2).

[0080]

X _C '= (X _C -X ₀ ) cos θ + (Y _C -Y ₀ ) sin θ + X ₀ Y _C ' =-(X _C -X ₀ ) sin θ + (Y _C -Y ₀ ) cos θ + Y ₀

[0081]

According to the present invention, since pre-alignment can be performed without contacting the photosensitive substrate, it is possible to prevent the generation of dust due to the pins coming into contact with the photosensitive substrate. In addition, compatibility with the conventional pre-alignment method can be maintained.

[Brief description of drawings]

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

2A and 2B are explanatory views of a wafer transfer system and a wafer transfer mechanism on a wafer stage, FIG. 2A is a plan view of a configuration around a wafer transfer system and a wafer stage, and FIG.

3A and 3B are explanatory views of wafer attitude control in a wafer transfer system, in which FIG. 3A is a schematic view of a turntable;
(B) is a figure which shows a detection signal.

FIG. 4 is an explanatory diagram of an example of an image processing apparatus.

FIG. 5 is an explanatory diagram of another example of the image processing apparatus.

FIG. 6 is a diagram illustrating a positional relationship of three fixing pins of a conventional pre-alignment mechanism.

FIG. 7 is a diagram showing a positional relationship of an observation visual field of an image processing apparatus with respect to a wafer.

FIG. 8 is a flowchart showing an example of a processing procedure for pre-aligning a wafer.

FIG. 9 is a wafer layout diagram for explaining a processing procedure.

FIG. 10 is a flowchart showing another example of a processing procedure for pre-aligning a wafer.

FIG. 11 is a diagram showing a positional relationship of an observation visual field of the image processing apparatus with respect to the wafer.

FIG. 12 is a layout view of wafers for explaining a processing procedure.

FIG. 13 is a flowchart showing another example of a processing procedure for prealigning a wafer.

FIG. 14 is a diagram illustrating a method of detecting the position of a notch portion of a notch wafer.

FIG. 15 is an explanatory diagram of a conventional pre-alignment mechanism for a wafer provided with an orientation flat portion.

FIG. 16 is an explanatory diagram of a conventional pre-alignment mechanism for a wafer having a notch portion.

[Explanation of symbols]

1 ... Reticle, 3 ... Projection optical system, 6 ... Wafer, 10 ... Z
Tilt drive unit, 11 ... X stage, 12 ... Y stage,
14 ... Wafer base, 15 ... Alignment control system, 16
... Stage control system, 18 ... Central control system, 21,22 ... Wafer arm, 23 ... Slider, 29 ... Sample stage, 30 ...
Wafer holder, 35 ... Expansion / contraction mechanism, 36 ... Rotation control system, 3
7 ... Drive shaft, 38 ... Center up, 38a-38c ...
Spindle part, 39 ... Wafer transfer device, 50, 51, 5
2 ... Image processing device, 50a, 51a, 52a ... Observation field of view, 59 ... Imaging element, 60 ... Turntable, 61 ... Eccentricity sensor, 91, 92, 93 ... Fixed pin, 94 ... Moving pin, 96, 97 ... Fixed pin , 98 ... Moving pin, FP ... Orientation flat part, NP ... Notch part, P ₁ ,
P ₂ , P ₃ , P _N ... Virtual pins, W1, W2 ... Wafer

Claims (4)

[Claims] 1. A positioning method for positioning a photosensitive substrate, which is substantially circular and has a linear notch in a part of its outer periphery, on a substrate stage movable in a two-dimensional direction. It is conveyed to a predetermined transfer point above the stage, the outer peripheral portion of the photosensitive substrate is imaged at the transfer point, and two of the three virtual pins in a predetermined relative positional relationship are cut into the linear shape. Determining a first position of the three virtual pins when the remaining one virtual pin contacts the circular portion and simultaneously contacts the outer peripheral portion of the photosensitive substrate. A step of obtaining a rotation angle and a translational displacement amount necessary to match a first position with a second position of the three virtual pins set on the substrate stage; and only the obtained rotation angle. The photosensitivity And a step of rotating the substrate. 2. A positioning method for positioning a photosensitive substrate, which is substantially circular and has a linear notch in a part of its outer periphery, on a substrate stage that is movable in two dimensions. A step of conveying the photosensitive substrate to a predetermined transfer point above the stage, imaging the outer peripheral portion of the photosensitive substrate at the transfer point, and obtaining a rotation angle of the photosensitive substrate based on the direction of the linear cutout portion of the photosensitive substrate. A straight line parallel to the linear cutout portion and separated from the linear cutout portion by a predetermined distance, and the outer circumference of the photosensitive substrate.
Obtaining the position of one of the two intersections, determining the translational displacement of the photosensitive substrate based on the position of the intersection and the direction of the linear notch, and only the determined rotation angle And a step of rotating the photosensitive substrate. 3. A positioning method for positioning a photosensitive substrate, which is substantially circular and has a V-shaped notch in a part of its outer periphery, on a substrate stage movable in a two-dimensional direction. Transporting to a predetermined transfer point above the substrate stage, imaging the outer peripheral portion of the photosensitive substrate at the transfer point, and obtaining the position of the V-shaped notch; One virtual movable pin that is movable in a one-dimensional direction defined with respect to the two virtual pins positions the virtual movable pin in the V-shaped cutout portion, and the remaining two virtual pins are circular. Determining the positions of the three virtual pins when they are in contact with the outer peripheral portion of the photosensitive substrate at the same time, and the rotational angle and the translational position shift of the photosensitive substrate from the positions of the three virtual pins. A positioning method comprising: a step of obtaining an amount; and a step of rotating the photosensitive substrate by the obtained rotation angle. 4. The positioning method according to claim 1, wherein the translational positional deviation amount is used as an offset for two-dimensional movement of the substrate stage.