JPH10223528A - Projection exposure apparatus and alignment method - Google Patents

Abstract

(57) [Summary] [Problem] To reduce measurement time for alignment,
Improve throughput. SOLUTION: One of the two measurement optical systems 26 and 28 can be moved in the XY two-dimensional direction within a plane orthogonal to the optical axis of the projection optical system PL, so that this movable measurement can be performed. Adjusting the position of the optical system 28 to adjust the interval (or positional relationship) between the measuring optical systems 26 and 28 corresponding to the positional relationship of the alignment marks arranged at predetermined intervals on the photosensitive substrate W. Thereby, two alignment marks can be measured simultaneously. Therefore, it is possible to reduce the time required for mark measurement as compared with the conventional case where alignment marks are measured one by one.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus and a positioning method, and more particularly, to a projection exposure apparatus used for manufacturing a semiconductor device (integrated circuit), a liquid crystal display device, etc. The present invention relates to an interlayer alignment method.

[0002]

2. Description of the Related Art Conventionally, various exposure apparatuses have been used in a photolithography process for manufacturing an integrated circuit, a liquid crystal display substrate, and the like.・ Repeat type reduction projection type exposure equipment (so-called stepper)
Etc. are the mainstream.

In this stepper, when a mask on which a pattern to be projected is drawn by exposure light, that is, a reticle is illuminated, a photosensitive material is applied to the pattern on the reticle via a reduction projection optical system. The image is projected onto a substrate such as a silicon wafer or a glass plate (hereinafter collectively referred to as “wafer”), whereby the photosensitive material on the wafer is exposed to form a reduced image of the pattern. Then, while holding the wafer, the above-described exposure is repeated while the movable stage (wafer stage) whose position is controlled via position measuring means such as a laser interferometer is sequentially moved, so that The pattern is sequentially transferred (projection exposure) to a predetermined area.

In the manufacture of an integrated circuit such as a semiconductor device, the device pattern is currently divided into several layers, and a metal layer for electrodes and the like is formed and patterned, and a metal layer is formed for insulation. Generally, a so-called planar technique of repeatedly forming a dielectric layer to form a laminate is used. That is, a plurality of layers are required to manufacture a semiconductor device,
For example, since it is necessary to accurately form circuit patterns covering over a dozen layers, the relative position of the pattern on the reticle to be formed in the manufacturing process must be determined relative to the pattern already formed on the wafer. It is necessary to expose after securing. For this reason, upon reticle pattern projection exposure, it is necessary to accurately perform alignment with the pattern of the previously formed layer (hereinafter, appropriately referred to as “alignment”), and the pattern line width is required to be highly integrated. Accordingly, high alignment accuracy has been required due to the miniaturization.

A typical method for detecting the position of a wafer is an off-axis method in which the position of a wafer mounted on a reduction projection exposure apparatus is determined by detecting a typical mark position on the wafer prior to exposure. There is. As an off-axis measuring microscope (alignment microscope) used for the mark position detection, one having an image capturing and image processing function as disclosed in, for example, JP-A-2-54103 is known. I have. FIG. 16 schematically shows the positional relationship between the projection optical system PL constituting the projection exposure apparatus and the off-axis type measuring microscope 200 as described above. In FIG. 16, the distance Ba (more precisely, the distance between the center (optical axis) of the projection optical system PL representing the center of the reticle and the center of the measurement axis of the measuring microscope 200) is the distance between the projection optical system PL and the measuring microscope. It shows the relative distance to 200 and is called the baseline length.

In the alignment process using such a measuring microscope 200, for example, Japanese Patent Application Laid-Open No. 61-44429
As disclosed in Japanese Patent Application Laid-Open Publication No. H11-157, the positions of some (usually several to about ten) reference marks formed in advance on the wafer are monitored by the image processing signal of the measurement microscope and the position of the wafer stage. Based on the measured values of the interferometer to be performed, and using this detection result and the design data of the shot array on the wafer, perform a statistical operation such as a least square method, and perform a statistical operation on the wafer for positioning during exposure. A so-called enhanced global alignment (hereinafter, appropriately referred to as “EGA”) for determining a coordinate position of each shot is used. In this case, since it is necessary to change the position of the wafer to be measured and exposed during the position measurement and the projection exposure, it is important to accurately measure the above-described baseline length Ba and to maintain it stably. is there.

FIG. 17 is a schematic diagram showing an arrangement of shot areas (unit exposure patterns) S (having the size of horizontal Px and vertical Py) on the wafer W, for example, hatched (hatched). Exposure pattern S is denoted by EG
It is assumed that the shot area is an A measurement target, that is, an EGA shot. In the drawing, Mx and My are position measurement marks (alignment reference marks) formed in advance in the shot area, and a pair of x and y constitutes a set of position coordinate information. Therefore, in the example of FIG. 17, since there are eight EGA shots, each of which has two marks, a total of 16 locations, that is, 16 measurements are performed.

In recent years, as the degree of integration of integrated circuits has increased, the alignment accuracy required for a projection exposure apparatus has become stricter. In particular, alignment reference marks (M
(x, My) position deviation and the position deviation of the alignment reference mark due to the distortion (so-called distortion) of the projection optical system are also hindering the improvement of the accuracy of the alignment measurement. Therefore, a plurality of reference marks for position measurement are prepared in a unit sequential exposure pattern (a so-called shot area), and a plurality of marks are measured even in an exposure shot at the time of alignment measurement, and are used as correction values at the time of alignment. A method of using the method is proposed in, for example, Japanese Patent Application Laid-Open No. 6-275496.

FIG. 18 shows that each exposure shot S contains X-Y
Reference marks (Mx1 / My1, Mx2 / My)
A schematic diagram of an arrangement of shot areas on a wafer where 2) is arranged is shown. In this case, the number of EGA measurement points is the number of exposure shots N to be measured and the number of measurement points n in the shot.
N × n. In the example of FIG.
= 32 points, and the measurement is performed 32 times.

[0010]

In general, a projection exposure apparatus has at least three requirements: high imaging performance capable of exposing a sufficiently fine line width, high interlayer alignment accuracy, and high wafer processing capability (so-called throughput). Two important requests have been made. However, in order to improve the alignment accuracy, for example, the number of measurement shots of the EGA measurement is increased, and the measurement time is increased,
There is a disadvantage that the throughput is reduced. Especially,
When a larger number of measurement points are arranged in each shot area as in the example of FIG. 18, there is a disadvantage that this tendency is further promoted.

The present invention has been made under such circumstances, and an object of the present invention is to provide a projection exposure apparatus capable of shortening the measurement time for alignment and improving the throughput. Another object of the present invention is to provide a positioning method usable in a projection exposure apparatus, which can improve alignment accuracy without sacrificing the throughput of the projection exposure apparatus.

[0012]

According to a first aspect of the present invention, there is provided a projection exposure apparatus for transferring a pattern formed on a mask onto a photosensitive substrate on which a plurality of alignment marks are formed, A projection optical system; and two or more measurement optical systems for measuring alignment marks formed on the photosensitive substrate without the intervention of the projection optical system, at least one of which is provided with the projection optical system. It is characterized by being movable in at least one axial direction within a plane perpendicular to the optical axis.

According to this, at least one of the two or more measurement optical systems is movable in at least one axial direction in a plane orthogonal to the optical axis of the projection optical system. By adjusting the position of the system, it is possible to adjust the interval (or positional relationship) between the measuring microscopes in accordance with the positional relationship of the alignment marks arranged along the predetermined uniaxial direction on the photosensitive substrate. This makes it possible to measure at least two alignment marks at the same time. As a result, the time required for mark measurement can be reduced as compared with the conventional case where alignment marks are measured one by one.

According to a second aspect of the present invention, in the projection exposure apparatus according to the first aspect, the at least one movable measurement optical system is arranged in the projection exposure apparatus in association with the plurality of measurement optical systems. The system further includes a relative position measurement system that measures a relative position of the system with respect to the projection optical system or a fixed measurement optical system. According to this, even when the arrangement of the alignment marks on the photosensitive substrate is different between the layers, for example, the movable measurement optical system can be moved to an accurate position in accordance with the arrangement of these marks. it can.

According to a third aspect of the present invention, in the projection exposure apparatus according to the second aspect, the plurality of measurement optical systems are connected to the plurality of measurement optical systems and arranged in the projection exposure apparatus. An arithmetic processing unit is further provided for sequentially determining positions of alignment marks formed in a plurality of predetermined shot areas according to measurement data obtained from the optical system, and calculating array coordinates of each shot area. According to this, each shot area can be accurately positioned at the exposure position based on the calculated array coordinates. Here, when measuring the position of the alignment mark formed in the predetermined plurality of shot areas, the arithmetic processing unit can simultaneously measure at least two alignment marks.

According to a fourth aspect of the present invention, there is provided a movable projection exposure apparatus for sequentially positioning a plurality of shot areas on a photosensitive substrate on which a plurality of alignment marks are formed at a transfer position, wherein the plurality of shot areas are formed on a mask. A projection optical system for projecting the set pattern onto the shot area; and a plurality of measurement optical systems for measuring the number of alignment marks corresponding to the number of the measurement optical systems, at least one of which is provided. One is movable in at least one axial direction within a plane perpendicular to the optical axis of the projection optical system.

According to this, at least one of the two or more measurement optical systems is movable in at least one axis direction in a plane orthogonal to the optical axis of the projection optical system. By adjusting the position of the system, a plurality of measurement marks are arranged in each shot area on the photosensitive substrate or in the same shot area, in accordance with the positional relationship of the alignment marks arranged along a predetermined uniaxial direction. The interval (or positional relationship) can be adjusted. This makes it possible to simultaneously measure at least two alignment marks existing between different shot areas or within the same shot area. As a result, the time required for mark measurement can be reduced as compared with the conventional case where alignment marks are measured one by one.

According to a fifth aspect of the present invention, in the projection exposure apparatus according to the fourth aspect, the at least one movable measurement optical system is disposed in the projection exposure device in association with the plurality of measurement optical systems. A relative position measurement system that measures a relative position of the system with respect to the projection optical system or a fixed measurement optical system and generates relative position measurement data indicating the relative position. According to this, even when the arrangement of the alignment marks on the photosensitive substrate is different between the layers, for example, the movable measurement optical system can be moved to an accurate position in accordance with the arrangement of these marks. it can.

According to a sixth aspect of the present invention, in the projection exposure apparatus according to the fifth aspect, the plurality of measurement optical systems are operatively connected to each other and arranged in the projection exposure apparatus, and the relative position measurement data is stored in the projection exposure apparatus. Accordingly, the apparatus further includes a control device that controls a position of the at least one movable measurement optical system and controls the relative positional relationship with the projection optical system to be constant. According to this, since there is further provided control means for controlling the movable measurement optical system so as to keep the relative positional relationship with the projection optical system constant, any external force during measurement of the alignment mark, such as vibration Even in the case where the control is performed, the relative positional relationship of the movable measurement optical system with respect to the projection optical system during the measurement of the alignment mark is kept constant. As a result, a reduction in the measurement accuracy of the alignment mark due to disturbance is prevented.

According to a seventh aspect of the present invention, in the projection exposure apparatus according to the fifth aspect, the plurality of measurement optical systems are connected to the plurality of measurement optical systems, and the plurality of measurement optical systems are arranged in the projection exposure apparatus. The image processing apparatus further includes an arithmetic processing unit that sequentially determines positions of alignment marks formed in a plurality of predetermined shot areas based on measurement data obtained from the optical system, and calculates array coordinates of each shot area. According to this, each shot area can be accurately positioned at the exposure position based on the calculated array coordinates. Here, when measuring the position of the alignment mark formed in the predetermined plurality of shot areas, the arithmetic processing unit can simultaneously measure at least two alignment marks.

In this case, the arithmetic processing means includes:
As in the invention according to claim 8, when measuring the position of the alignment mark, a plurality of marks in the same shot area may be simultaneously measured for at least one shot. The invention according to claim 9 is the invention according to claim 3 or 7.
The projection exposure apparatus according to the above, the arithmetic processing unit,
An arrangement of each shot area is calculated by statistical processing based on the measurement result and reference shot arrangement data. According to this, since the arithmetic processing device calculates at least the array coordinates of each shot area by performing statistical processing,
It is not necessary to measure all the alignment marks, and the throughput is improved.

According to a ninth aspect of the present invention, there is provided the first or fourth aspect.
Wherein the movable measurement optical system is movable in two orthogonal axial directions. According to this, it is possible to measure at least two alignment marks at the same time by adjusting the position of the movable measurement optical system regardless of the arrangement of the alignment marks on the photosensitive substrate. become.

According to a tenth aspect of the present invention, there is provided a projection exposure apparatus for transferring a pattern formed on a mask onto a photosensitive substrate on which a plurality of alignment marks are formed, wherein the conjugate plane with respect to the photosensitive substrate is provided. A measurement optical system of an image processing method having at least two index marks whose relative positional relationship can be adjusted above, and measuring the alignment mark formed on the photosensitive substrate; A projection optical system for projecting the pattern formed on the mask onto the photosensitive substrate according to the measurement result.

According to this, by adjusting the relative positional relationship of each index mark to the position of at least two alignment marks formed on the photosensitive substrate, the index marks and the alignment marks are one-to-one. For example, an image in which the alignment mark is positioned within each index mark can be obtained as an output image of the measurement optical system. Therefore, it is possible to simultaneously measure the positions of at least two alignment marks from the relative positional relationship between each index mark and the corresponding alignment mark.

According to an eleventh aspect of the present invention, there is provided an alignment method for aligning a plurality of shot areas arranged on a substrate and onto which a pattern formed on a mask is transferred, wherein at least one shot area is selected in advance. A first step of simultaneously measuring the positions of a plurality of alignment marks in one shot area; according to the measurement result in the first step,
A second step of calculating a coordinate position on the stationary coordinate system of each of the plurality of shot regions arranged on the substrate; controlling a movement position of the substrate according to a calculation result in the second step; A third step of aligning each of the shot areas with a predetermined transfer position of the pattern. According to this, when measuring the coordinate positions of a plurality of shot areas selected in advance on the stationary coordinate system, the positions of a plurality of alignment marks having substantially the same positional relationship of the plurality of shot areas are simultaneously measured. Time can be reduced.

According to a thirteenth aspect of the present invention, in the alignment method according to the twelfth aspect, in the first step, the positions of the plurality of alignment marks of the plurality of shot areas having substantially the same positional relationship are simultaneously determined. The measurement is performed at least twice. According to this, when measuring the coordinate positions of a plurality of shot areas selected in advance on the stationary coordinate system, at least measuring the positions of a plurality of alignment marks in substantially the same positional relationship of the plurality of shot areas is at least performed. Do twice. Also, since the alignment marks are usually formed by exposure, a plurality of alignment marks having substantially the same positional relationship of a plurality of shot areas measured simultaneously in the present invention have the same shape, so that alignment marks of the same shape are used. Since the position measurement using the mark is repeated a plurality of times, mechanical or electrical random errors of the detection system are reduced.

According to a fourteenth aspect of the present invention, in the alignment method according to the thirteenth aspect, in the second step, the positions of the plurality of alignment marks measured in the first step are statistically calculated. Thereby, the coordinate position of each of the plurality of shot areas is determined. Since at least the array coordinates of each shot area are calculated by statistical processing, it is not necessary to measure all the alignment marks, and the throughput is improved.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION

<< 1st Embodiment >> Hereinafter, 1st Embodiment of this invention is described based on FIG. 1 thru | or FIG. FIG. 1 shows a schematic configuration of a projection exposure apparatus 10 according to the first embodiment. The projection exposure apparatus 10 includes a step
This is a reduction projection type exposure apparatus (stepper) that reduces and projects a pattern of a reticle R as a mask onto each shot area on a wafer W as a photosensitive substrate by an and repeat method.

The projection exposure apparatus 10 includes an illumination system 12 including a light source for irradiating exposure light, a reticle stage 14 on which a reticle R as a mask is mounted, and a reticle stage 1.
4, a driving device 16, a projection optical system PL for projecting an image of a pattern formed on the reticle R onto the wafer W, an imaging characteristic control device 20 for correcting imaging characteristics such as projection magnification and distortion, and holding the wafer W. Stage 22 that moves in a two-dimensional plane, and drive device 2 for wafer stage 22
4, two off-axis type measuring microscopes (alignment microscopes) 26 and 28, a coordinate measuring circuit 30, and a main control system 32 for controlling the entire apparatus as a whole.

The illumination system 12 generates irradiation light IL for irradiating the reticle R. Although not shown in detail, the illumination system 12 opens and closes a light source and an optical path of light, such as an ultra-high pressure mercury lamp (i-line, g-line) or an excimer laser (KrF, ArF, F ₂ ). Illumination optical system including shutter, optical integrator (fly-eye lens), etc.
It includes an illumination system aperture stop, a variable blind that determines an illumination field of illumination light, and the like. Such illumination systems are well known in the field of lithography technology. In the illumination optical system, illumination light is made uniform and speckle is reduced. A reticle R mounted on a reticle stage 14 described below is illuminated under uniform and predetermined illumination conditions by light from an illumination light source such as a mercury lamp or an excimer laser in the illumination system 12.

A reticle R on which a predetermined pattern is formed is mounted on reticle stage 14, and reticle R is held by a reticle holder (not shown). The reticle stage 14 is configured to be movable and minutely rotated in a two-dimensional plane on the base 34. After the reticle R is mounted on the reticle stage 14, the drive unit 16 is controlled by the main control system 32, and the reticle R
The reticle R is positioned so that the center point (reticle center) of the pattern area coincides with the optical axis AX of the projection optical system PL (this step is called a reticle alignment step).

The projection optical system PL is composed of a plurality of lens elements having a common optical axis AX in the Z-axis direction, for example, so as to have a telecentric optical arrangement on both sides. The projection optical system PL has a predetermined reduction magnification (for example, 1
/ 5). For this reason, when the reticle R is illuminated with substantially uniform illuminance by the exposure light IL emitted from the illumination system 12, a reduced image of the pattern of the reticle R is projected onto each shot area on the wafer W via the projection optical system PL. Projected.

In the present embodiment, as described above, the imaging characteristic control device 20 is provided in addition to the projection optical system PL. The imaging characteristic control device 20 includes, for example, a projection optical system P
The projection magnification and the distortion of the projection optical system PL are adjusted by adjusting the distance between predetermined lens elements of the lens elements constituting L or by adjusting the pressure of gas in the lens chamber between the predetermined lens elements. Adjust the aberration. The imaging characteristic control device 20 performs the above adjustment under the control of the main control system 32.

On the wafer stage 22, a wafer W having a surface coated with a photoresist is loaded with a wafer holder 36.
Is placed via. Although not shown in detail, the wafer stage 22 is used to position the wafer W two-dimensionally in an XY plane orthogonal to the optical axis of the projection optical system PL.
It comprises a Y stage, a Z stage for positioning the wafer W in the optical axis direction (Z direction) of the projection optical system PL, a θ stage for slightly rotating the wafer W about the Z axis, and the like. Such a wafer stage is well known in the field of lithography technology.

A movable mirror 38 is provided on the upper surface of the wafer stage 22.
Is fixed, and a laser interferometer 40 is arranged so as to face the movable mirror 38. Note that, as shown in FIG. 2, actually, as a movable mirror, a rectangular coordinate system in a plane orthogonal to the optical axis of the projection optical system PL is defined as an X axis and a Y axis.
There is a plane mirror 38X having a reflection surface perpendicular to the X axis and a plane mirror 38Y having a reflection surface perpendicular to the Y axis.
Here, these are representatively shown as movable mirrors 38.
Here, the X axis and the Y axis are defined as axes expressing a rectangular coordinate system in a plane orthogonal to the optical axis of the projection optical system PL. The laser interferometer corresponding to these two movable mirrors 38X and 38Y is a laser interferometer 40X for two X axes that irradiates the movable mirror 38X with a laser beam along the X axis.
_1, and 40X _2, although there is a laser interferometer 40Y for Y-axis for irradiating a laser beam to the moving mirror 38Y along the Y axis, FIG. 1 these typically laser interferometer 40
It is shown as Then, by a laser interferometer 40Y for one laser interferometers 40X ₁ and Y axes of the X-axis, X-coordinate and Y-coordinate of the wafer stage 22 is measured. The stationary coordinate system (X, Y) composed of the X coordinate and the Y coordinate measured in this way is hereinafter referred to as a stage coordinate system.

Further, two laser interferometers 40 for the X axis are used.
From the difference between the measured values of X ₁ and 40X ₂ , the wafer stage 22
Is measured. Information on the X coordinate, the Y coordinate, and the rotation angle measured by the laser interferometer 40 is supplied to the coordinate measuring circuit 30 and the main control system 32. The main control system 32 controls the driving device 24 while monitoring the supplied coordinates. Through,
The positioning operation of the wafer stage 22 is controlled.

Further, near the one end of the upper surface of the wafer stage 22, there is provided a reference plate FP on which various reference marks including a reference mark used for baseline measurement of measurement microscopes 26 and 28 described later are formed. This reference plate FP
Is selected such that its surface is located at substantially the same height position as the surface of the wafer W.

Although not shown, the reticle side is provided with the same interferometer system as the wafer side.

In the projection exposure apparatus 10 of this embodiment, as shown in FIG. 1 and FIG.
Off-axis alignment type measurement microscope 2
6, 28 are arranged. One of the measurement microscopes 26 is fixed at a predetermined position (the position in FIGS. 2 and 7), and the other measurement microscope 28 is configured to be movable within a predetermined stroke range in the XY two-dimensional directions. I have.

FIG. 3 shows an example of a moving mechanism of the measuring microscope 28. As shown in FIG. 3, the measuring microscope 28 is held by an X moving mechanism 72 movable along an X-axis guide 70, and its optical axis is parallel to the Z-axis direction. Further, a pair of Ys arranged on the same XY plane at predetermined intervals in the X-axis direction are provided at both ends of the X-axis guide 70.
A pair of Y moving mechanisms 76A and 76B movable along the guides 74A and 74B are provided. That is, the X moving mechanism 72 and the pair of Y moving mechanisms 76A and 76B constitute a moving mechanism that drives the measuring microscope 28 in the XY two-dimensional directions. As a driving source of the X moving mechanism 72 and the pair of Y moving mechanisms 76A and 76B, for example, a linear motor is used. Note that these X moving mechanism 72 and a pair of Y moving mechanisms 76A and 76B also
2 is controlled.

A moving mirror 78 having a reflecting surface orthogonal to the X axis is fixed on the upper surface of the X moving mechanism 72, and a reflecting surface orthogonal to the Y axis is mounted on the upper surface of one Y moving mechanism 76A. The movable mirror 80 is fixed. A reflection mirror 82 is fixed on the upper surface of the other Y moving mechanism 76B so that its reflection surface forms an angle of 45 degrees with the ZY plane. The reflection mirror 82 is located at a predetermined distance from the mirror 82 along the Y axis. A reflection mirror 84 is arranged in parallel with the mirror 82 and with its reflection surface facing the reflection surface of the mirror 82. The moving distance of the movable mirror 80 from the reference point in the Y-axis direction is measured by a laser interferometer 86Y provided opposite thereto, and the moving distance of the movable mirror 78 from the reference point is determined by the reflection mirror 84, It is measured by a laser interferometer 86X that irradiates a laser beam vertically to the movable mirror 78 via 82. The measured values of these laser interferometers 86X and 86Y are also supplied to the coordinate measuring circuit 30. In the coordinate measuring circuit 30, the displacement of the movable mirror 80, that is, Y from the reference point of the measuring microscope 28, is determined based on the output of the laser interferometer 86Y.
Calculate the displacement. Further, the coordinate measuring circuit 30 calculates the moving distance of the moving mirror 78 from the reference point based on the output of the laser interferometer 86X, and subtracts the Y displacement from the moving distance, that is, the displacement of the moving mirror 78, that is, the measuring microscope. The X displacement from the 28 reference points is calculated. Here, as described above, in the coordinate measuring circuit 30, based on the outputs of the laser interferometers 86X and 86Y, the X displacement of the measuring microscope 28 from the reference point and the Y
Only the displacement can be detected, and the relative position of the measuring microscope 28 with respect to the projection optical system PL (or the fixed-side measuring microscope 26) cannot be directly detected. However, the projection optical system PL of the measurement microscope 28 at the reference point
Since the relative position with respect to (or the fixed-side measurement microscope 26) can be measured in advance at the time of baseline measurement using the reference plate FP, as a result, the laser interferometer 86
The relative position of the measuring microscope 28 with respect to the projection optical system PL (or the fixed-side measuring microscope 26) can be detected based on the outputs of X and 86Y.

As described above, in the present embodiment, the movable mirror 8
0, laser interferometer 86Y, moving mirror 78, reflecting mirror 8
2, 84, the laser interferometer 86X and the coordinate measurement circuit 30 constitute a measurement system for measuring the relative position of the measurement microscope 28 with respect to the projection optical system PL (or the fixed-side measurement microscope 26). Note that the position of the measuring microscope 28 may be detected by another sensor such as an encoder, but it is desirable to use a laser interferometer as in the present embodiment from the viewpoint of measurement accuracy.

Next, a specific configuration of the measuring microscopes 26 and 28 will be described. FIG. 4 shows the configuration of the fixed measurement microscope 26.

The measuring microscope 26 includes a light source 41, a collimator lens 42, a beam splitter 44, a mirror 46,
Condenser lens 50, index plate 52, first relay lens 54,
Beam splitter 56, X-axis second relay lens 58
It is configured to include an X-axis image pickup device 60X composed of X and two-dimensional CCDs, a Y-axis second relay lens 58Y, and a Y-axis image pickup device 60Y composed of a two-dimensional CCD. here,
Each component of the measuring microscope 26 will be described together with its operation.

The light source 41 is a non-photosensitive light that does not expose the photoresist on the wafer, and emits light having a broad bandwidth (for example, about 200 nm) having a broad wavelength distribution. In particular, a halogen lamp can be suitably used as the light source 41. In order to prevent a decrease in mark detection accuracy due to thin-film interference in the resist layer, it is desirable to use illumination light having a sufficiently broad wavelength width. This is particularly important when an image processing type measurement microscope such as the measurement microscope 26 is used.

Illumination light from the light source 41 is transmitted through the collimator lens 42, the beam splitter 44, the mirror 46, and the objective lens 48 to the alignment mark MA or MB on the wafer W (see FIG. 6;
A "). Then, the reflected light from the alignment mark MA reaches the index plate 52 via the objective lens 48, the mirror 46, the beam splitter 44, and the condenser lens 50, and the image of the alignment mark MA is formed on the index plate 52. Is done.

The light transmitted through the index plate 52 is directed to the beam splitter 56 via the first relay lens 54, and the light transmitted through the beam splitter 56 is transmitted to the X-axis image sensor 60X by the second X-axis relay lens 58X. The light focused on the imaging surface and reflected by the beam splitter 56 is focused on the imaging surface of the Y-axis imaging element 60Y by the second Y-axis relay lens 58Y. On the imaging surfaces of the imaging elements 60X and 60Y, an image of the alignment mark MA and an image of the index mark on the index plate 52 are formed so as to overlap each other. The imaging signals obtained by the imaging devices 60X and 60Y are both supplied to the coordinate position measurement circuit 30.

The movable measuring microscope 28 is constructed similarly to the measuring microscope 26, and has an X-axis image pickup device and a Y-axis image pickup device. The imaging signals obtained by these imaging elements are also supplied to the coordinate position measurement circuit 30 together.

FIG. 5 shows an example of a pattern on the index plate 52 of FIG. In FIG. 5, an image MAP of a cross-shaped alignment mark MA is formed at the center. The XP direction and the YP direction perpendicular to the linear pattern images MAXP and MAYP orthogonal to this image MAP, respectively,
Each is conjugate to the X and Y directions of the stage coordinate system of the wafer stage 22. Then, two index marks 90A and 90B are formed so as to sandwich the alignment mark image MAP in the XP direction, and similarly, two index marks 92A and 92B are sandwiched so as to sandwich the alignment mark image MAP in the YP direction. Is formed.

In this case, in the XP direction, the index marks 90A,
90B and a detection area 94 surrounding the linear pattern image MAXP
The image in X is picked up by the X-axis image sensor 60X in FIG.
An image in the detection area 94Y surrounding the index marks 92A and 92B and the linear pattern image MAYP in the P direction is picked up by the Y-axis image sensor 60Y in FIG. Image sensors 60X and 60Y
In, the pixels are scanned in the XP direction and the YP direction, and an electrical imaging signal corresponding to the optical image is obtained. By processing these imaging signals output from the imaging elements 60X and 60Y, the alignment mark image MAP and the index mark 9 are processed.
0A and 90B in the XP direction, and the alignment mark image MAP and the index marks 92A and 92A.
The amount of misregistration in the YP direction from 92B is obtained. Therefore, the coordinate measuring circuit 30 obtains the positional relationship between the image of the alignment mark MA on the wafer W and the index mark on the index plate 52 and the measurement result of the laser interferometer 40 at that time.
The coordinates (X, Y) of the alignment mark MA formed on the wafer W in the stage coordinate system are obtained.

Next, the first book constructed as described above is used.
The alignment operation and the exposure operation in the projection exposure apparatus 10 according to the embodiment will be described by taking as an example the second layer exposure of the wafer W having the shot arrangement as shown in FIG.

First, a wafer W is transferred from a wafer loader (not shown) to the wafer holder 36 shown in FIGS. In each shot area of the wafer W, a circuit pattern has already been formed by exposing the previous layer. Furthermore, as shown in FIG. 6, each shot area on the wafer _{W S n (n = 1,2,3,} ......, 26) are each 2
Cross-shaped alignment marks MA _n , MB _n (n =
1, 2, 3,..., 26) are formed. Here, it is assumed that the alignment of the reticle R has been completed, and the amounts of displacement of the reticle R in the X, Y, and rotational directions with respect to the orthogonal coordinates defined by an interferometer (not shown) are substantially zero.

[0053] Alignment marks MA _n, MB _n is formed at a position which becomes point symmetry with respect to the center (reference point) of each shot area, in design, X-direction length of each shot area S _n is Px, the Y-direction The length is assumed to be Py. Also, the distance in the X direction between the mark centers in the same shot is p
x, and the interval in the Y direction is py.

Next, the main control system 32 performs the origin adjustment (pre-alignment) of the wafer W. Then, Japanese Patent Laid-Open No. 6-27
As described in detail in Japanese Patent No. 5496, EGA (Enhanced Global Alignment) measurement is performed.
In the present embodiment, prior to this, the main control system 32 adjusts the position of the movable measurement microscope 28.

More specifically, in the case of the wafer W shown in FIG. 6, eight shot areas (S ₁ , S ₄ , S ₅ , S ₈ , S ₁₉ , S ₂₂ , S ₂₂ ) which are hatched as sample shots.
_23, it is assumed to select the S _26), the alignment mark M
At the same time measures the A ₁ and MA _4, then measures the MB ₁ and MB ₄ simultaneously, it is assumed that sequentially measured two by two marks so that measuring the subsequent MA ₅ and MA ₈ simultaneously. In this case, since these sets of alignment marks measured at the same time are located on substantially the same X axis, when the two microscopes 26 and 28 are in a positional relationship as shown in the plan view of FIG. In the control system 32, the Y moving mechanism 7 shown in FIG.
6A and 76B are fixed at the positions, the measuring microscope 28 is driven in the + X direction from this state, and the measuring microscope 28 is moved via the X moving mechanism 72 so that the distance d = 3Px shown in the plan view of FIG. Adjust the position of. Here, when the measuring microscope 28 is located at the reference position shown in FIG.
Using P, the detection center of the measuring microscope 28 and the projection optical system PL
The measurement of the baseline length Ba2 ₀ is the distance between the optical axis, in advance baseline length of the fixed side of the measuring microscope 26 B
if it performed with measurement of a1 _0, both the microscope 2 in FIG. 7
Since the interval D between 6 and 28 is known, the baseline length Ba2 after the movement is used as the measurement value of the interferometers 86X and 86Y for managing the position of the measurement microscope 28 without measuring the baseline length Ba2 again. Can be determined based on the

When the position adjustment of the measuring microscope 28 is completed, the main control system 32 drives the wafer stage 22 in the XY two-dimensional manner while servo-controlling the position of the measuring microscope 28 so that the base line length Ba2 does not fluctuate. Then 8
Alignment marks MA _m and MB _m (m = 1, 4, 5, 5) in one EGA shot area (sample shot area)
8, 19, 22, 23, 26) stage coordinate system (X,
Y) The coordinate values (FM _NXn , FM _NYn ) are actually measured.
Here, in the present embodiment, as described above, two alignment marks MA (or MB) separated by 3Px can be simultaneously measured using the measurement microscopes 26 and 28, so that the alignment marks are sequentially measured one by one. Measurement time is about 1 compared to the conventional case that had to be performed.
/ 2 can be shortened.

When the measurement of the alignment mark position of the sample shot is completed, the main control system 32 compares the measurement result with the wafer at the reference point (shot center) of the known eight selected shot areas. An array coordinate value (C _Xn , design) on the coordinate system (α, β) on W
C _Yn ) and the design coordinate value (relative coordinate value) (S _NXn, S _NYn ) of the measured alignment mark on each shot area Sn in the coordinate system (x, y) are expressed by the following equation. coordinate transformation stage coordinate system of the shot area S _n of the wafer W based on the equation (X, Y) coordinates of the calculation of the above, and each error of shot areas (magnification error of shot areas themselves, rotation error, etc.) Ask for.

F _Nn = AC _n + BS _Nn + O (1) where each transformation matrix of the equation (1) is defined as follows.

[0059]

(Equation 1)

Here, Γx = Rx−1 is a parameter obtained by replacing the wafer scaling Rx in the α direction to facilitate application of the method of least squares, and Γy = Ry−1 is β
Is a parameter obtained by replacing the wafer scaling Ry in the direction to facilitate the application of the least squares method, and Θ is a coordinate system (α, β) of the wafer with respect to the stage coordinate system (X, Y).
W is a parameter indicating the orthogonality error of the stage coordinate system (X, Y), and γx is a shot area in the x direction on the coordinate system (x, y) of the shot area. Is a parameter indicating the linear expansion and contraction of
γy is a parameter indicating the linear expansion and contraction of the shot area in the y direction on the coordinate system (x, y) of the shot area, and θ is the rotation of the circuit pattern on each shot area of the wafer, that is, the coordinate system (x , Y), a parameter indicating the rotation error of the circuit pattern on each shot area of the wafer, and w
_x and _Oy are parameters indicating the offset amount of the coordinate system on the wafer with respect to the stage coordinate system.

In equation (1), a matrix F _Nn of 2 rows × 1 column is represented by
It is represented by the sum of a matrix AC _n , a matrix BS _Nn, and a matrix O. The conversion matrices A, B,
The 10 error parameters (Θ, W, Γx
(= Rx-1), Γy , O x, O y, θ, w, γx (=
rx-1), γy) can be obtained by, for example, the least square method. For how to find this error parameter,
Since it is disclosed in detail in JP-A-6-275496, further description is omitted here.

Thereafter, the main control system 32 rotates the reticle R through the reticle stage 14 appropriately so as to correct the remaining rotation error θ of the circuit pattern on each shot area in the conversion matrix B of the equation (1). subjected to, suppress stage coordinate system (X, Y) of rotation of the circuit pattern on the shot area S _n for small.

Next, the orthogonality error w of the coordinate system on the wafer W
Can not be corrected in a strict sense, but by rotating the reticle R appropriately, the error can be kept small. Therefore, in the main control system 32, the rotation error Θ and the rotation error θ
It is also possible to optimize the rotation amount of the reticle R or the wafer W such that the sum of the absolute values of the orthogonality error w and the orthogonality error w becomes minimum.

Next, the main control system 32 corrects linear expansion and contraction (scaling error) in two orthogonal directions of the circuit pattern on each shot area Sn in the conversion matrix B of the equation (1). The projection magnification of the projection optical system PL is adjusted via the first imaging characteristic control device 20. That is, in this correction processing, the projection magnification of the projection optical system PL is adjusted in accordance with the shot scalings rx and ry constituting the elements of the transformation matrix B.

Next, the main control system 32 uses the transformation matrices A and O including the elements composed of the error parameters obtained above to calculate the reference point of each shot area Sn on the wafer W in the following equation. By substituting the array coordinate values (C _Xn , C _Yn ), the calculated array coordinate values (G _Xn , G _Yn ) of the reference point on the stage coordinate system (X, Y) are obtained.

[0066]

(Equation 2)

In the main control system 32, each shot area Sn on the wafer W is determined based on the array coordinates (G _Xn , G _Yn ) obtained by calculation and the base line lengths Ba1 and Ba2 obtained in advance. The reference point is positioned at a predetermined position in the exposure field of the projection optical system PL, and the pattern image of the reticle R is projected and exposed on the shot area. Such alignment and projection exposure are sequentially performed for each shot area. After the exposure of all the shot areas on the wafer W is completed, the development of the wafer W is performed.

In this case, as shown in the equation (1), not only the transformation matrices A and O but also the transformation matrix B including shot area rotation, shot area orthogonality error, and shot scaling parameters are taken into consideration. Therefore, the influence of the expansion / contraction or rotation of the circuit pattern itself transferred to each shot area is reduced, and the circuit pattern of each shot area on the wafer W and the projected image of the pattern of the reticle R are superimposed with higher accuracy. be able to.

As is clear from the above description, the apparatus 10 according to the first embodiment employs the movable measurement microscope 2.
8, control means for controlling the relative positional relationship with respect to the projection optical system PL to be kept constant, and a predetermined plurality of shot areas using the measurement optical systems 26 and 28 while moving the wafer W prior to the start of exposure. Arithmetic processing means for sequentially measuring the positions of the alignment marks formed on the shot area, and calculating at least the array coordinates of each shot area by statistical processing based on the measurement results and the shot array data in design,
It is provided by the function of the main control system 32.

Next, an example of an alignment mark that can be actually used will be described with reference to FIG. First, as an alignment mark (two-dimensional mark) indicating two-dimensional coordinates, in addition to the cross-shaped alignment mark MA used in the above embodiment (this is also shown in FIG. 9A), an L-shaped , T-shaped, or C-shaped marks. Further, FIG.
A two-dimensional lattice mark as shown in FIG.
As shown in (C), a line-and-
An alignment mark MD in which the space pattern MDX and the line and space pattern MDY in the Y direction are arranged in parallel also becomes a two-dimensional mark.

Selecting one such two-dimensional mark is equivalent to 10 (or less) in equation (1).
X that can be adopted when the parameters of
Two pieces of data, that is, coordinate data and Y coordinate data are obtained. This means that the use of one cross-shaped alignment mark (for example, MA ₁ ) adopted in the above embodiment is equivalent to the use of an alignment mark (one-dimensional mark) indicating two one-dimensional coordinates. Means. However, even when a two-dimensional mark is selected, only one coordinate data of the X coordinate or the Y coordinate may be used.

The mark indicating the coordinate in the X direction of the one-dimensional mark is the same as MDX in FIG. 9C.
There is a line-and-space pattern arranged at a predetermined pitch in the direction, and a mark indicating the coordinates in the Y-direction is a line-and-space pattern arranged at a predetermined pitch in the Y-direction like MDY in FIG. 9C.・ There is a space pattern.

As described above, according to the projection exposure apparatus 10 of the first embodiment, the reference positions of a plurality of shot areas on the wafer W (substrate to be processed) are
At the same time as the average alignment error is reduced, the average overlay error with the reticle pattern image is reduced for all the circuit patterns on the shot areas. As a result, the influence of the expansion, contraction, and rotation of the circuit pattern itself transferred to each shot area is reduced, and the chip pattern of each shot area on the wafer and the projected image of the mask pattern can be superimposed with higher accuracy. it can. Therefore, the number of good chips that can be obtained from one wafer increases, and the productivity of chips such as semiconductor elements can be improved.

Further, since the positions of alignment marks (alignment marks) of the same shape arranged in a plurality of shot areas on the wafer are repeatedly measured a plurality of times, the mechanical or electrical There is also an advantage that random errors are reduced. In addition, in EGA measurement,
Since two alignment marks in different shot areas (sample shots) are measured at the same time, the alignment mark measurement time can be significantly reduced (up to about half), and the throughput is improved accordingly. Can be achieved.

In the above description, two alignment marks (for example, MA ₁ and MA ₄ ) arranged at a substantially constant interval along the X-axis direction are used for the measurement microscope 2.
Has been described a case where measured simultaneously by 6, 28, but not limited thereto, for example MA ₁ and MA _5, MB ₁ and M
It is also possible to simultaneously measure by the measuring microscope 26 the two alignment marks located substantially in the same positional relationship between the two shot areas ₅ such as B. Even in this case, the measurement time of the alignment mark in the EGA measurement can be reduced to about half of the conventional case in the same manner as described above, so that the throughput can be improved accordingly.

In the first embodiment, the case where two alignment marks in different shot areas are measured at the same time is exemplified. However, if the distance between the tips of the two measurement microscopes is reduced, the same shot area is simultaneously measured. It is also possible to measure another alignment mark (for example, MA ₁ , MB ₁ ). As a method for selecting a sample shot, it is not preferable that the position of the measurement microscope 28 fluctuates during measurement. Therefore, for efficient operation of simultaneous measurement, as shown in FIG. It is desirable to select a sample shot such that a shot region including the two alignment marks is selected as a pair.

In the above description, the case where two two-dimensional alignment marks are arranged in each shot has been exemplified. However, when it is not necessary to correct the remaining rotation error of the circuit pattern in the shot, each shot may be used. One two-dimensional alignment mark may be arranged in each of the two. In such a case, one one-dimensional mark for use in the X-direction measurement and another one-dimensional mark for use in the Y-direction measurement may be arranged. Further, in the above-described embodiment, a case has been described in which only the movable measurement microscope 28 is movable in the XY two-dimensional directions. However, both of the measurement microscopes 26 and 28 may be movable. 28 may be movable only in one of the X-axis direction and the Y-axis direction, or may be movable only in the other one direction.

In the alignment measurement, since there is generally an allowable value of the measurement position (so-called cap range), it is not necessary to strictly set the distance d between the two microscopes 26 and 28 to an integer multiple of the pitch. However, a change in the position of the microscope 28 causes a change in the baseline length.
After adjusting the position of 8 as described above, accurately measure the baseline length and keep it constant, or continue to monitor the position of the microscope 28 during the alignment operation, and subtract the position error from the measurement result to correct it. It is desirable to do.

The number of measuring microscopes is not limited to two, but may be three, for example, as shown in FIG. In the case of FIG. 10, the central measuring microscope 2
6 is fixed, and the measurement microscopes 28A and 28B on both sides are movable in the X-axis direction. In this case, since the distances d1 and d2 can be adjusted, for example, three out of a plurality of shot areas arranged along the X-axis direction are selected as sample shots, and three alignment marks can be measured simultaneously. As a result, the measurement time can be further reduced. However, in this case, at the time of baseline measurement using the reference plate FP, three measurement microscopes 28A,
Baseline length Ba for each of 26 and 28B
It is necessary to measure 1, Ba2 and Ba3.

When three measuring microscopes are provided, the microscopes do not necessarily have to be arranged in a line. For example, the microscopes may be arranged so as to be located at the apexes of a triangle. In this case, it goes without saying that there is a degree of freedom in how to select a sample shot and how to select an alignment mark to be subjected to simultaneous measurement.

<< Second Embodiment >> Next, a second embodiment of the present invention will be described with reference to FIGS. Here, the same reference numerals are used for the same components as those in the first embodiment, and the description thereof will be simplified or omitted.

FIG. 11 is a schematic perspective view showing the vicinity of the projection optical system PL and the wafer stage 22 of the projection exposure apparatus 100 according to the second embodiment. As shown in FIG. 11, the projection exposure apparatus 100 is different from the projection exposure apparatus 10 of the first embodiment in that only one measurement microscope 128 is provided.
The measuring microscope 128 is fixed as a whole and mainly has two alignment marks arranged in close proximity to each other, for example, alignment marks MA in the same shot area on the wafer W as shown in FIG. Detect MB simultaneously.

FIG. 12 shows the configuration of the measuring microscope 128. The measuring microscope 128 has a configuration in which the beam splitter 102 is disposed on the optical path between the beam splitter 44 and the condenser lens 50 in the configuration of the measuring microscope 26 shown in FIG.
The light condensing lens 104, the index plate 106, the first relay lens 108, the beam splitter 110, An X-axis second relay lens 112X, an X-axis imaging element 114X composed of a two-dimensional CCD, a Y-axis second relay lens 112Y, a Y-axis imaging element 114Y composed of a two-dimensional CCD, and the like are added.

Here, each component of the measuring microscope 128 will be described together with its operation.

The illumination light from the light source 41 passes through a collimator lens 42, a beam splitter 44, a mirror 46, and an objective lens 48 to an area including the alignment marks MA and MB on the wafer W (hereinafter, referred to as “mark area M”). Irradiated. Then, the reflected light from the mark area M reaches the beam splitter 102 via the objective lens 48, the mirror 46, and the beam splitter 44. The reflected light from the mark area M reflected by the beam splitter 102 is irradiated onto the index plate 106 via the condenser lens 104, and an image of the mark area M is formed on the index plate 106.

Further, the light transmitted through the index plate 106 becomes the first light.
The light reaches the beam splitter 110 via the relay lens 108. Then, the light transmitted through the beam splitter 110 is focused on the imaging surface of the X-axis image sensor 112X by the second X-axis relay lens 112X, and the light reflected by the beam splitter 110 is converted into the second Y-axis relay. Lens 11
The image is focused on the imaging surface of the Y-axis imaging element 114Y by 2Y. An image of the mark area M and an image of the index mark on the index plate 106 are formed on the imaging surfaces of the imaging elements 114X and 114Y, respectively. Image sensors 114X and 11
The imaging signals obtained by 4Y are both supplied to the coordinate position measurement circuit 30.

On the other hand, the reflected light from the mark area M transmitted through the index plate 102 is irradiated onto the index plate 52 via the condenser lens 50, and thereafter, as described above, the image sensor 60X
The image of the mark area M and the image of the index mark on the index plate 52 are formed on the imaging planes of 60Y and 60Y, respectively.
The imaging signals obtained by the imaging devices 60X and 60Y are both supplied to the coordinate position measurement circuit 30.

Here, in the present embodiment, the objective lens 48
The one having a wider image field than that of the first embodiment is preferably used. Further, as the index plate 106, an index mark (9) as shown in FIG.
0A, 90B, 92A, 92B)
2 are used, and these index plates 52 and 106 are arranged on a surface conjugate with the wafer W surface. The directions XP and YP of the index marks on the index plate 52 are conjugate with the X and Y directions of the stage coordinate system of the wafer stage 22. Similarly, the directions of the index marks on the index plate 106 (for convenience, XQ and YQ) are also conjugate to the X and Y directions of the stage coordinate system of the wafer stage 22. In the following description, the index mark on the index plate 52 is PM1, and the index mark on the index plate 106 is PM1.
Call it 2.

The magnifications of the condenser lenses 50 and 104, the magnifications of the first relay lenses 54 and 108, the magnifications of the X-axis second relay lenses 58X and 112X, and the magnifications of the Y-axis second relay lenses 58Y and 112Y are as follows. Are set identically. The newly provided index plate 106 is configured to be movable in a two-dimensional direction in a horizontal plane (a plane conjugate to the XY plane) (see arrow B in FIG. 12).
Can be driven by a piezo element or the like (not shown).

Accordingly, the magnification of each lens is appropriately adjusted under the above conditions, and the mark area including the alignment marks MA ₁ and MB ₁ (hereinafter referred to as “mark area M”) in the shot area S ₁ in FIG. As a result of the measurement, for example, the image sensors 60X and 60Y (hereinafter, “image sensor 6
0 ”), an image as shown in FIG. 14A is output, and the image sensors 114X and 1
When an image as shown in FIG. 14B is output by an image pickup signal from the image pickup device 14Y (hereinafter, referred to as “image pickup device 114”), FIG. Is output.

Therefore, by appropriately moving the index plate 106 two-dimensionally in the horizontal plane from the state shown in FIG.
As shown by the dotted arrow in FIG.
There moved, the index mark PM2 reaches the position where the image surrounding the alignment mark MB ₁ is obtained. When this position is the index plate 106, the positional relationship between the index marks PM1 and the alignment mark MA ₁ being captured signal of the imaging device 60, the index mark P in the imaging signal of the imaging element 114
Based on the positional relationship between M2 and the alignment mark MB _1, it is possible to position measurement of the alignment mark MA ₁ and MB ₁ at the same time.

Therefore, in the second embodiment, the first
Instead of adjusting the position of the measuring microscope 28 after pre-alignment of the wafer W in the embodiment, the positional relationship between the index marks is substantially as shown in FIG. 15 based on the design data of the alignment mark position. Before the alignment mark measurement of the EGA sample shot, the position of the index plate 106 is adjusted so that

The subsequent alignment operation including the alignment mark measurement operation of the sample shot and the exposure operation are the same as those in the first embodiment. However, in the case of the present embodiment, the alignment marks MA _m and MB _m (m = 1, 4, 5, 8, 19, 2) in the same shot area S _m
2,23,26) successively simultaneous measurement points to measure the alignment marks in the sample shots S _m shown in FIG. 13 differs from the description in the first embodiment by. Also in the present embodiment, the positional relationship between the index marks (or the relative positional relationship of each index mark with respect to the projection optical system PL) is important in aligning the actual shot area on the wafer W with the exposure position. The reference plate F
It is necessary to grasp the above positional relationship by baseline measurement using P.

As described above, according to the second embodiment, it is possible to achieve an improvement in throughput equivalent to that of the first embodiment and high-accuracy superposition. The number of the indicator plates is not limited to two, but may be three or more.
In this case, it is possible to simultaneously detect three or more alignment marks in the same shot area using each index mark of each index plate.

Further, in the second embodiment, the 2
Although the two alignment marks irradiate the irradiation light to the region including MA and MB, for example, the light source 41 and the wafer W
A field stop having two openings respectively corresponding to the two alignment marks MA and MB is arranged in a plane conjugate with the wafer W, and includes a first area including the alignment mark MA and the alignment mark MB. The illumination light may be separately applied to the second region. In addition, 2
When the arrangement (position, interval, etc.) of the two alignment marks is changed, the opening position of the field stop may be changed correspondingly. This opening position can be changed by, for example, preparing a plurality of field stops having different opening positions from each other, selecting a field stop corresponding to the alignment mark arrangement, and arranging the selected field stop on the illumination optical path. It should be noted that at least two field stops having different positions and shapes of apertures are combined and arranged in the illumination optical path, whereby the first
Alternatively, the illumination light may be separately applied to the second region. Further, for example, if the field stop is constituted by a liquid crystal display element, the number, position, shape, size, and the like of the openings can be easily adjusted according to the number and arrangement of the alignment marks on the wafer.

In the first embodiment, at least one measurement optical system is moved. However, instead of moving the measurement optical system, a plurality of measurement optical systems are irradiated on the wafer through the same measurement optical system. It may be configured to change at least one position of the illumination light. For example, the second
When a plurality of alignment marks on the wafer W are separately irradiated with illumination light by the measurement microscope 128 according to the embodiment and a field stop having a plurality of apertures, and when the position or arrangement of the alignment mark is changed, The position of at least one opening of the field stop may be changed to change the position of the illumination light on the wafer.

In the first and second embodiments, the case where the present invention is applied to a so-called step-and-repeat type exposure apparatus (stepper) has been described. However, the present invention is not limited to this. For example, JP-A-4-196
No. 513, JP-A-4-277612, JP-A-2-22
No. 9423 and the like, a so-called step-and-scan type (type in which a reticle and a wafer are exposed while moving in synchronization with each other) (scanning / scanning type).
It can be suitably applied to a stepper.

Further, the present invention provides a projection exposure apparatus (mirror projection aligner, stepper, etc.) used in a photolithography process for manufacturing a micro device such as a semiconductor device, a liquid crystal display device, an image pickup device (CCD), or a thin film magnetic head. Scanning stepper etc.), but also other manufacturing equipment used in the photolithography process, for example, by irradiating a laser beam to the fuse of the circuit pattern formed on the semiconductor wafer, the fuse It can also be applied to a laser repair device that cuts a laser beam.

For example, 5 to 15 nm (soft X-ray region)
EUV (Extreme Ultra Viol
et) light is used as exposure illumination light, the illumination area on the reflection mask is defined in an arc slit shape, and a reduction projection optical system including only a plurality of reflection optical elements (mirrors) is provided. The present invention can also be applied to an EUV exposure apparatus or the like that transfers the pattern of the reflection mask onto the wafer by synchronously moving the reflection mask and the wafer at a speed ratio according to the magnification.

[0100]

As described above, according to the present invention,
Since a plurality of alignment marks can be measured at the same time, the measurement time for alignment can be reduced to 1 / the number of the maximum measurement optical systems (or index marks), and the throughput of the entire system can be improved. Can be.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a configuration of a projection exposure apparatus according to a first embodiment.

FIG. 2 is a schematic perspective view showing the vicinity of a wafer stage and a projection optical system of the apparatus of FIG.

FIG. 3 is a perspective view showing a configuration example of a moving mechanism of a movable measurement optical system.

FIG. 4 is a diagram showing a configuration of a measurement optical system.

FIG. 5 is an enlarged view showing the arrangement of an alignment mark image and index marks on the index plate of FIG. 4;

FIG. 6 is a view for explaining the operation of the apparatus according to the first embodiment, and is a view showing an example of a wafer on which a circuit pattern has already been transferred.

FIG. 7 is a diagram for explaining the operation of the apparatus according to the first embodiment, and is a plan view showing the arrangement of the projection optical system and the measurement optical system at reference points.

FIG. 8 is a diagram for explaining the operation of the apparatus according to the first embodiment, and is a plan view showing the arrangement of the projection optical system and the measurement optical system.

FIG. 9 is a diagram illustrating an example of an alignment mark indicating two-dimensional coordinates ((A) to (C)).

FIG. 10 is a plan view showing an arrangement of a projection optical system and a measurement optical system at a reference point when three measurement microscopes are provided.

FIG. 11 is a schematic perspective view showing the vicinity of a wafer stage and a projection optical system of a projection exposure apparatus according to a second embodiment.

FIG. 12 is a diagram illustrating a configuration of a measurement microscope in FIG. 11;

FIG. 13 is a view for explaining the operation of the apparatus according to the second embodiment, showing an example of a wafer on which a circuit pattern has already been transferred.

14A is a diagram illustrating an image obtained by an image pickup signal from an image sensor 60, FIG. 14B is a diagram illustrating an image obtained by an image pickup signal from an image sensor 114, and FIG. FIG. 3 is a diagram illustrating a composite image obtained from an image pickup signal of an image pickup device.

FIG. 15 is a diagram for explaining the position adjustment of the index plate, and is a diagram illustrating an example of a composite image after the index mark has moved.

FIG. 16 is a plan view showing an arrangement of a projection optical system and an off-axis measurement microscope in a conventional projection exposure apparatus.

FIG. 17 is a schematic diagram showing an arrangement of shot areas on a wafer.

FIG. 18 is a schematic diagram showing an arrangement of shot areas on a wafer in which two sets of XY reference marks are arranged in each shot area.

[Explanation of symbols]

Reference Signs List 10 projection exposure apparatus 26 fixed measurement microscope (measurement optical system) 28 movable measurement microscope (measurement optical system) 30 coordinate measurement circuit (part of relative position measurement system) 32 control system (control device, arithmetic processing device) 52 index Plates 78, 80 Moving mirror (part of relative position measurement system) 82, 84 Reflection mirror (part of relative position measurement system) 86X, 86Y Laser interferometer (part of relative position measurement system) 100 Projection exposure apparatus 106 Index Plate 128 Measurement microscope (measurement optical system) R Reticle (mask) PL Projection optical system W Wafer (photosensitive substrate) MA, MB Alignment mark (positioning mark) PM1, PM2 Index mark

Claims (14)

[Claims] 1. A projection exposure apparatus for transferring a pattern formed on a mask onto a photosensitive substrate having a plurality of alignment marks formed thereon, comprising: a projection optical system; A plurality of measurement optical systems for measuring the plurality of alignment marks, at least one of which is movable in at least one axial direction in a plane orthogonal to the optical axis of the projection optical system. Projection exposure equipment. 2. The measurement optical system according to claim 1, wherein said at least one movable measurement optical system is located in said projection exposure apparatus in relation to said plurality of measurement optical systems, and said at least one movable measurement optical system is positioned relative to said projection optical system. 2. The projection exposure apparatus according to claim 1, further comprising a relative position measurement system for measuring a relative position with respect to the system. 3. A projection exposure apparatus connected to the plurality of measurement optical systems and arranged in a predetermined plurality of shot areas according to measurement data obtained from the plurality of measurement optical systems prior to the start of exposure. The projection exposure apparatus according to claim 2, further comprising an arithmetic processing unit that sequentially determines the positions of the alignment marks thus calculated, and calculates array coordinates of each shot area. 4. A movable projection exposure apparatus for sequentially positioning a plurality of shot areas on a photosensitive substrate, on which a plurality of alignment marks are formed, at a transfer position, wherein the pattern formed on a mask is transferred to the shot area. A plurality of measurement optical systems for measuring the number of alignment marks corresponding to the number of the plurality of measurement optical systems, at least one of which is the projection optical system. A projection exposure apparatus which is movable in at least one axis direction within a plane orthogonal to the optical axis of the projection exposure apparatus. 5. The relative position of the at least one movable measurement optical system with respect to the projection optical system, or a fixed measurement optical system, which is disposed in the projection exposure apparatus in association with the plurality of measurement optical systems. The projection exposure apparatus according to claim 4, further comprising a relative position measurement system that measures a relative position with respect to the system and generates relative position measurement data indicating the relative position. 6. The apparatus according to claim 1, further comprising a plurality of measurement optical systems that are operatively connected to the plurality of measurement optical systems and arranged in the projection exposure apparatus, and control a position of the at least one movable measurement optical system according to the relative position measurement data. 6. The projection exposure apparatus according to claim 5, further comprising a control device for controlling a relative positional relationship with respect to the projection optical system to be kept constant. 7. A projection exposure apparatus connected to the plurality of measurement optical systems and arranged in a predetermined plurality of shot areas based on measurement data obtained from the plurality of measurement optical systems prior to the start of exposure. 6. The projection exposure apparatus according to claim 5, further comprising an arithmetic processing unit that sequentially determines the positions of the alignment marks thus calculated, and calculates array coordinates of each shot area. 8. The projection exposure according to claim 7, wherein the arithmetic processing unit simultaneously measures a plurality of marks in the same shot area for at least one shot when measuring the position of the alignment mark. apparatus. 9. The apparatus according to claim 3, wherein the arithmetic processing unit calculates an array of each shot area by statistical processing based on the measurement result and reference shot array data.
Or the projection exposure apparatus according to 7. 10. The movable measurement optical system includes:
5. The projection exposure apparatus according to claim 1, wherein the projection exposure apparatus is movable in an axial direction. 11. A projection exposure apparatus for transferring a pattern formed on a mask onto a photosensitive substrate on which a plurality of alignment marks have been formed, wherein a relative positional relationship on the conjugate plane with respect to the photosensitive substrate is provided. Has at least two index marks that can be adjusted, and a measurement optical system of an image processing method for measuring the alignment mark formed on the photosensitive substrate; and on the mask according to a measurement result by the measurement optical system. A projection optical system for projecting the pattern formed on the photosensitive substrate onto the photosensitive substrate. 12. A positioning method for positioning a plurality of shot areas arranged on a substrate and onto which a pattern formed on a mask is transferred, comprising: a plurality of positions in at least one shot area selected in advance. A first step of simultaneously measuring the position of the alignment mark; and a second step of calculating a coordinate position on the stationary coordinate system of each of the plurality of shot areas arranged on the substrate according to the measurement result in the first step. And a third step of controlling the moving position of the substrate according to the calculation result in the second step, and positioning each of the plurality of shot areas to a predetermined transfer position of the pattern. 13. The method according to claim 12, wherein in the first step, the positions of a plurality of alignment marks having substantially the same positional relationship of the plurality of shot areas are simultaneously measured at least twice. Alignment method. 14. In the second step, the coordinate positions of the plurality of shot areas are determined by statistically calculating the positions of the plurality of alignment marks measured in the first step. The alignment method according to claim 13, wherein: