JP4029182B2 - Exposure method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exposure method and an exposure apparatus. More specifically, the present invention relates to an exposure method in which a mask pattern used when manufacturing a semiconductor element, a liquid crystal display element or the like in a lithography process is exposed on a sensitive substrate via a projection optical system. Further, the present invention relates to an exposure apparatus such as a drawing apparatus that directly draws a pattern on a sensitive substrate with a laser beam, an electron beam, or other charged particle beam for manufacturing a semiconductor element, a mask for manufacturing a semiconductor element, and the like. The present invention is characterized by having a plurality of substrate stages for holding a sensitive substrate.
[0002]
[Prior art]
Conventionally, various exposure apparatuses have been used for manufacturing a semiconductor element or a liquid crystal display element in a photolithography process. Currently, a pattern of a photomask or a reticle (hereinafter, collectively referred to as “reticle”) is used. A projection exposure apparatus for transferring an image onto a substrate such as a wafer or a glass plate (hereinafter referred to as “sensitive substrate” or “wafer” as appropriate) having a surface coated with a photosensitive material such as a photoresist via a projection optical system. Is commonly used. In recent years, as this projection exposure apparatus, a sensitive substrate is placed on a two-dimensionally movable substrate stage, and the sensitive substrate is stepped (stepped) by this substrate stage, so that the pattern image of the reticle is placed on the sensitive substrate. The so-called step-and-repeat type reduction projection exposure apparatus (so-called stepper), which repeats the operation of sequentially exposing each shot area, is the mainstream.
[0003]
Recently, a step-and-scan type projection exposure apparatus (for example, a scanning exposure apparatus as described in Japanese Patent Application Laid-Open No. 7-176468), which is an improvement on a static exposure apparatus such as a stepper, has also been developed. It has come to be used relatively frequently. This step-and-scan type projection exposure apparatus can expose a large field with a smaller optical system as compared with (1) a stepper. Therefore, the projection optical system can be easily manufactured and the number of shots by large field exposure can be reduced. High throughput can be expected due to the decrease, and (2) there are advantages such as an effect of averaging by relatively scanning the reticle and wafer with respect to the projection optical system, and an improvement in distortion and depth of focus.
[0004]
In this type of projection exposure apparatus, it is necessary to align the reticle and wafer with high accuracy prior to exposure. In order to perform this alignment, a position detection mark (alignment mark) formed (exposure transfer) formed in the previous photolithography process is provided on the wafer. By detecting the position of this alignment mark, the wafer The exact position of (or the circuit pattern on the wafer) can be detected.
[0005]
There are two types of alignment microscopes that detect alignment marks: an on-axis method that detects marks through a projection lens and an off-axis method that detects marks without using a projection lens. In an exposure apparatus that uses an excimer laser light source, an off-axis alignment microscope is optimal. This is because the projection lens is corrected for chromatic aberration with respect to the exposure light, so in the case of on-axis, the alignment light cannot be collected or even if it can be collected, the error due to chromatic aberration becomes very large. On the other hand, since the off-axis alignment microscope is provided separately from the projection lens, free optical design is possible without considering such chromatic aberration, and various alignment systems are used. Because it can. For example, a phase contrast microscope or a differential interference microscope can be used.
[0006]
By the way, the flow of processing in this type of projection exposure apparatus is roughly as follows.
[0007]
(1) First, a wafer loading process of loading a wafer onto a wafer table using a wafer loader is performed, and so-called search alignment is performed by using the wafer outer shape as a reference.
[0008]
{Circle around (2)} Next, a fine alignment process for accurately determining the position of each shot area on the wafer is performed. In this fine alignment process, an EGA (Enhanced Global Alignment) method is generally used. In this method, a plurality of sample shots in a wafer are selected, and an alignment mark (wafer mark) attached to the sample shot is selected. Are sequentially measured, and based on the measurement result and the design value of the shot arrangement, a statistical calculation is performed by a so-called least square method or the like to obtain all shot arrangement data on the wafer (Japanese Patent Laid-Open No. 61). -44429, etc.), the coordinate position of each shot area can be obtained with relatively high accuracy with high throughput.
[0009]
(3) Next, based on the coordinate position of each shot area obtained by the above-described EGA method or the like and the baseline amount measured in advance, each shot area on the wafer is sequentially positioned at the exposure position, and the projection optical system is An exposure process for transferring the pattern image of the reticle onto the wafer is performed.
[0010]
(4) Next, a wafer unloading step is performed in which the wafer on the wafer table subjected to the exposure process is unloaded using a wafer unloader. This wafer unloading step is performed simultaneously with the wafer loading step (1). That is, (1) and (4) constitute a wafer exchange process.
[0011]
As described above, in the conventional projection exposure apparatus, three major operations are repeatedly performed using one wafer stage, such as wafer exchange (including search alignment) → fine alignment → exposure → wafer exchange. .
[0012]
[Problems to be solved by the invention]
Since the projection exposure apparatus described above is mainly used as a mass production machine for semiconductor elements and the like, it is possible to improve the processing capability, ie, throughput, of how many wafers can be exposed within a certain time. Necessarily requested.
[0013]
In this regard, in the current projection exposure apparatus, since the three operations described above are performed sequentially, it is necessary to reduce the time required for each operation in order to improve the throughput. The effect of improvement is relatively small because only one operation is performed on one wafer. Further, the time required for fine alignment can be shortened by reducing the number of shots when using the above-described EGA method or by shortening the measurement time of a single shot. Since the alignment accuracy is degraded, the time required for fine alignment cannot be easily reduced.
[0014]
Therefore, it can be concluded that shortening the exposure time is the most effective for improving the throughput, but in this exposure operation, in the case of a stepper, a pure wafer exposure time is used. In order to shorten the wafer exposure time, a large amount of light from the light source is essential to shorten the wafer exposure time. However, in this type of projection exposure apparatus, in addition to the above throughput, as an important condition, ▲ (1) Resolution, (2) Depth of Forcus (DOF), (3) Linewidth control accuracy, etc. The resolution R is the exposure wavelength is λ and the numerical aperture of the projection lens is N.P. A. (Numerical Aperture), λ / N. A. And the depth of focus DOF is λ / (NA) ² Is proportional to For this reason, it is also necessary for the light source to have a short wavelength, both of which have a large power and a short wavelength compared to the bright lines (g-line, i-line) etc. of the ultra-high pressure mercury lamps conventionally used. The excimer laser described above as satisfying the requirements is said to become the mainstream in the future, and a light source having a shorter wavelength and a larger amount of light and suitable as a light source for an exposure apparatus has not been considered at this stage. Accordingly, the improvement in throughput beyond the case where an excimer laser is used as the light source cannot be expected so much, and there is a limit to the improvement in throughput by devising the light source.
[0015]
On the other hand, in order to shorten the stepping time between shots, it is necessary to improve the maximum speed and maximum acceleration of the stage holding the wafer. However, the improvement in the maximum speed and maximum acceleration tends to cause deterioration of the positioning accuracy of the stage. There was an inconvenience. In addition, in the case of a scanning projection exposure apparatus such as the step-and-scan method, the exposure time of the wafer can be shortened by increasing the relative scanning speed of the reticle and the wafer. Since the synchronization accuracy is likely to deteriorate, the scanning speed cannot be easily increased. Therefore, it is necessary to improve the controllability of the stage.
[0016]
However, it is not easy to improve the controllability of the stage in an apparatus using an off-axis alignment microscope, such as a projection exposure apparatus using an excimer laser light source that will become the mainstream in the future. In other words, this type of projection exposure system accurately manages the position of the wafer stage, both during exposure of the mask pattern via the projection optical system and during alignment, without Abbe error, and achieves high-precision overlay. In order to achieve this, it is necessary to set the measurement axis of the laser interferometer so that it passes through the projection center of the projection optical system and the detection center of the alignment microscope, and within the stage moving range during exposure and during alignment. The stage is inevitably necessary because the length measurement axis passing through the projection center of the projection optical system and the length measurement axis passing through the detection center of the alignment microscope must not be cut off both within the range of movement of the stage. This is because the size is increased.
[0017]
From the above, it is difficult to improve the throughput without any demerit by the method of shortening the time required for each of the three operations described above, and a new technique for improving the throughput by a method different from this. The appearance was long-awaited.
[0018]
The present invention has been made under such circumstances, and the object of the present invention is to improve the throughput and to determine the size of the substrate stage regardless of the baseline amount. It is to provide an exposure method.
[0020]
[Means for Solving the Problems]
If the above-mentioned three operations, that is, wafer exchange (including search alignment), fine alignment, and exposure operations, can be processed partially or simultaneously in parallel, these operations are performed sequentially. Thus, it is considered that the throughput can be improved. The present invention has been made paying attention to such a viewpoint, and employs the following method and configuration. That is,
The present invention is an exposure method in which an image of a pattern formed on a mask (R) is exposed on a sensitive substrate (W) via a projection optical system (PL), each holding the sensitive substrate (W). Two substrate stages (WS1, WS2) that can be moved independently within the same plane are prepared; the sensitivity held by one of the two substrate stages (WS1, WS2) (WS1 or WS2) Exposing the pattern image of the mask (R) onto the substrate (W) via the projection optical system (PL); during the exposure of the sensitive substrate (W) held on the one substrate stage (WS1 or WS2) Further, the position of the alignment mark on the sensitive substrate (W) held on the other substrate stage (WS2 or WS1) of the two substrate stages and the reference point on the other stage (WS2 or WS1) Measure the relationship After the exposure of the sensitive substrate held on the one substrate stage, the reference point on the other substrate stage is positioned in the projection region of the projection optical system (PL), and a predetermined point in the projection region is set. Detecting a positional deviation of the reference point on the other substrate stage and a coordinate position of the other substrate stage with respect to a reference point; based on the measured positional relationship, the detected positional deviation and the detected coordinate position The movement of the other substrate stage is controlled to align the sensitive substrate held on the other stage with the pattern image of the mask. Each substrate stage has a stage main body and a substrate holding member that is detachably mounted on the main body and holds the substrate, and a reflection surface for an interferometer is provided on a side surface of the substrate holding member, In addition, a reference mark is formed as the reference point on the upper surface of the substrate holding member, and after the exposure of the sensitive substrate held on the one substrate stage, the substrate holding member on the one and the other stage is replaced. Be called An exposure method characterized by the above.
[0021]
According to this, on the sensitive substrate (W) held on one substrate stage (WS1 or WS2) of the two substrate stages (WS1, WS2), the mask (via the projection optical system (PL)). While exposure of the pattern image of R) is performed, (1) The positional relationship between the alignment mark on the sensitive substrate (W) held on the other substrate stage (WS2 or WS1) of the two substrate stages and the reference point on the other stage (WS2 or WS1) is measured. The In this way, the exposure operation on one substrate stage side and the alignment operation on the other substrate stage side (the positional relationship between the alignment mark on the sensitive substrate held on the other substrate stage and the reference point on the other stage) Measurement) can be performed in parallel, so that it is possible to improve the throughput as compared with the prior art in which these operations are performed sequentially.
[0022]
After the exposure of the sensitive substrate held on the one substrate stage, the other substrate stage (WS2 or WS1) Board holding member With the upper reference point (reference mark) positioned in the projection area of the projection optical system (PL), (2) the other substrate stage with respect to a predetermined reference point in the projection area Board holding member The positional deviation of the upper reference point (reference mark) and (3) the coordinate position of the other substrate stage when the positional deviation is detected are detected. Thereafter, the movement of the other substrate stage (WS2 or WS1) is controlled based on (1) the measured positional relationship, (2) the detected positional deviation, and (3) the detected coordinate position, and the other stage The sensitive substrate held on the mask and the pattern image of the mask are aligned.
[0023]
For this reason, (1) Relationship between a predetermined reference point on the other substrate stage and an alignment mark on the sensitive substrate Measurement An interferometer (or coordinate system) that sometimes manages the position of the substrate stage, (2) , (3) Even if the interferometer (or coordinate system) that manages the position of the stage at the time of detecting the displacement of the substrate and the coordinate position of the substrate stage is the same or different, there is no inconvenience, and the pattern image of the mask and the other substrate Positioning with the sensitive substrate mounted on the stage can be performed with high accuracy.
[0024]
Therefore, for example, when an off-axis alignment system is used as a mark detection system for detecting an alignment mark, a predetermined reference point (projection center of the mask pattern image) in the projection area of the projection optical system and a detection center of the alignment system Therefore, there is no need to measure the positional relationship, that is, the baseline amount. As a result, there is no inconvenience even if the projection optical system and the alignment system are far apart, so the size of the substrate stage is set regardless of the baseline amount. Even if the substrate stage is reduced in size and weight, it is possible to perform mark position measurement and pattern exposure via the projection optical system on the entire surface of the sensitive substrate without any inconvenience. In this case, it is not affected by fluctuations in the baseline amount.
[0040]
DETAILED DESCRIPTION OF THE INVENTION
<< First Embodiment >>
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
[0041]
FIG. 1 shows a configuration of an exposure apparatus 100 according to the first embodiment. The exposure apparatus 100 is a step-and-repeat reduction projection exposure apparatus (so-called stepper).
[0042]
The projection exposure apparatus 100 includes an illumination system IOP, a reticle stage RST that holds a reticle R as a mask, a projection optical system PL that projects an image of a pattern formed on the reticle R onto a wafer W as a sensitive substrate, and a wafer. A wafer stage WS1 as a first substrate stage capable of moving W on the base 12 while holding W, and a wafer stage WS1 holding the wafer W and movable on the base 12 in the XY two-dimensional direction independently of the wafer stage WS1. A minicomputer (including a interferometer system 26 for measuring the positions of the wafer stage WS2 as the second substrate stage, the two wafer stages WS1 and WS2, and a CPU, ROM, RAM, I / O interface, etc. Or as a control means for overall control of the entire device. It is equipped with a control device 28, and the like.
[0043]
The illumination system IOP includes a light source (such as a mercury lamp or excimer laser) and an illumination optical system including a fly-eye lens, a relay lens, a condenser lens, and the like. The illumination system IOP illuminates the pattern on the lower surface (pattern formation surface) of the reticle R with a uniform illuminance distribution by illumination light IL for exposure from a light source. Here, as the illumination light IL for exposure, a bright line such as i-line of a mercury lamp, or excimer laser light such as KrF or ArF is used.
[0044]
A reticle R is fixed on the reticle stage RST via a fixing means (not shown). This reticle stage RST is driven by a driving system (not shown) in the X-axis direction (perpendicular to the paper surface in FIG. 1) and Y-axis direction ( It can be finely driven in the left and right direction in FIG. 1 and in the θ direction (rotation direction in the XY plane). Thus, the reticle stage RST can position the reticle R (reticle alignment) in a state where the center of the pattern of the reticle R (reticle center) substantially coincides with the optical axis Ae of the projection optical system PL. FIG. 1 shows a state in which this reticle alignment is performed.
[0045]
The projection optical system PL has an optical axis Ae that is in the Z-axis direction orthogonal to the moving surface of the reticle stage RST. Here, the projection optical system PL is bilaterally telecentric and has a predetermined reduction magnification β (β is, for example, 1/5). Has been. For this reason, when the reticle R is illuminated with uniform illuminance by the illumination light IL in a state where the pattern of the reticle R and the shot area on the wafer W are aligned, the pattern on the pattern forming surface is changed. The image is reduced by the projection optical system PL at the reduction magnification β and projected onto the wafer W coated with the photoresist, and a reduced image of the pattern is formed in each shot area on the wafer W.
[0046]
In the present embodiment, the X fixed mirror 14X, which serves as a reference for managing the position in the X-axis direction during exposure of the wafer stages WS1 and WS2, is provided on the side surface on the X-axis direction side (left side in FIG. 1) of the projection optical system PL. Similarly, on the side surface of the projection optical system PL on one side in the Y-axis direction (the back side in FIG. 1), a Y-fixed mirror serving as a reference for Y-axis direction position management during exposure of the wafer stages WS1 and WS2 14Y is fixed (see FIG. 3).
[0047]
Gas-static pressure bearings (not shown) are provided on the bottom surfaces of the wafer stages WS1 and WS2, respectively, and the wafer stages WS1 and WS2 are several microns (μm) between the upper surface of the base 12 and these gas-static pressure bearings. Each is supported to float above the base 12 with a certain degree of clearance. The wafer stage WS1, WS2 has a mirror-finished surface on one side in the X-axis direction (left side in FIG. 1) and one side in the Y-axis direction (back side in FIG. 1). Reflective surfaces that function as moving mirrors for reflecting the length measurement beam from 26 are formed.
[0048]
Further, magnets are respectively fixed to the bottom surfaces of the wafer stages WS1 and WS2, and a predetermined range in the base (specifically, a predetermined region near the projection optical system PL and a predetermined region near the alignment microscope WA). The wafer stages WS1 and WS2 move in the XY two-dimensional direction on the base 12 by electromagnetic force generated by a drive coil (not shown) embedded in the wafer. That is, a so-called moving magnet type linear motor as drive means for the wafer stages WS1 and WS2 is configured by the magnets on the bottom surfaces of the wafer stages WS1 and WS2 and the drive coil embedded in the base 12. The drive current of the drive coil of this linear motor is controlled by the main controller 28.
[0049]
Wafers W are held on wafer stages WS1 and WS2 by vacuum suction or the like via a wafer holder (not shown). Further, fiducial mark plates FM1 and FM2 are fixed on the wafer stages WS1 and WS2, respectively, so that the surfaces thereof are the same height as the surface of the wafer W. On the surface of one fiducial mark plate FM1, as shown in the plan view of FIG. 2, a mark WM for measurement with a wafer alignment microscope WA described later is formed at the center in the longitudinal direction. A pair of marks RM used for relative position measurement with the reticle R is formed on both sides in the direction through the projection optical system PL. The same marks WM and RM are also formed on the other reference mark plate FM2.
[0050]
Further, in the present embodiment, an alignment system that detects a position detection mark (alignment mark) formed on the wafer W at a predetermined distance, for example, 3000 mm away from the projection optical system PL in a direction approximately 45 degrees with respect to the XY axis. An off-axis alignment microscope WA is provided. The wafer W has a level difference due to exposure and process processing up to the previous layer, and includes a position detection mark (alignment mark) for measuring the position of each shot area on the wafer. The alignment mark is measured by the alignment microscope WA.
[0051]
As the alignment microscope WA, here, a so-called FIA (field image alignment) type alignment microscope of an image processing system is used. According to this, illumination light emitted from a light source (not shown) that emits broadband illumination light such as a halogen lamp passes through an objective lens (not shown) and then is irradiated onto the wafer W (or the reference mark plate FM). Reflected light from a wafer mark area (not shown) on the surface of the wafer W is sequentially transmitted through an objective lens and an index plate (not shown), and an image of the wafer mark and an index on the index plate are displayed on an imaging surface such as a CCD (not shown). An image is formed. The photoelectric conversion signals of these images are processed by a signal processing circuit (not shown) in the signal processing unit 16, and a relative position between the wafer mark and the index is calculated by an arithmetic circuit (not shown), and this relative position is determined by the main controller 28. To be told. Main controller 28 calculates the position of the alignment mark on wafer W based on this relative position and the measurement value of interferometer system 26.
[0052]
Further, an X-fixing mirror 18X serving as a reference for X-axis direction position management during the alignment operation of the wafer stages WS1 and WS2 is fixed to the side surface of the alignment microscope WA on one side in the X-axis direction (left side in FIG. 1). In addition, a Y-fixing mirror 18Y, which serves as a reference for Y-axis direction position management during the exposure operation of the wafer stages WS1 and WS2, is fixed to the side surface of the alignment microscope WA on one side in the Y-axis direction (the back side in FIG. 1). Yes.
[0053]
The alignment microscope is not limited to the FIA system, but other optical devices such as a phase contrast microscope and a differential interference microscope as well as other optical alignment systems such as a LIA (Laser Interferometric Alignment) system and an LSA (Laser Step Alignment) system. Also, atomic level irregularities on the sample surface using STM (Scanning Tunnel Microscope) that detects the atomic level irregularities on the sample surface using the tunnel effect and atomic force (attraction and repulsive force) It is also possible to use a non-optical device such as an AFM (Atomic Force Microscope) that detects the above.
[0054]
Further, in the projection exposure apparatus 100 of this embodiment, an image of the reference mark RM on the reference mark plate FM and a reticle alignment mark (not shown) on the reticle R are provided above the reticle R via the projection optical system PL. Reticle alignment microscopes 52A and 52B are provided as mark position detection means for simultaneous observation. The detection signals S1 and S2 of the reticle alignment microscopes 52A and 52B are supplied to the main controller 28. In this case, deflection mirrors 54A and 54B for guiding the detection light from the reticle R to the reticle alignment microscopes 52A and 52B are unitized with the reticle alignment microscopes 52A and 52B, respectively, so that a pair of microscope units 56A, 56B is configured. When the exposure sequence is started, these microscope units 56A and 56B are retracted to a position that does not cover the reticle pattern surface by a mirror driving device (not shown) in response to a command from the main controller 28.
[0055]
Next, the interferometer system 26 shown in FIG. 1 for managing the positions of the wafer stages WS1 and WS2 will be described in detail.
[0056]
As shown in FIG. 3, the interferometer system 26 actually includes a first laser interferometer 26Xe for measuring the position in the X-axis direction and a second laser interferometer 26Ye for measuring the position in the Y-axis direction. The third laser interferometer 26Xa for measuring the position in the X-axis direction and the fourth laser interferometer 26Ya for measuring the position in the Y-axis direction are configured. In FIG. Illustrated as metering system 26.
[0057]
The first laser interferometer 26Xe is a reference beam X in the X-axis direction passing through the projection center of the projection optical system PL with respect to the X fixed mirror 14X. _e1 And a measurement beam X against the reflecting surface of the wafer stage (WS1 or WS2) _e2 , And the displacement of the wafer stage reflecting surface with respect to the fixed mirror 14X is measured based on the interference state in which the reflected lights of these two beams are overlapped and interfered with each other.
[0058]
Further, the second laser interferometer 26Ye has a reference beam Y in the Y-axis direction passing through the projection center of the projection optical system PL with respect to the Y fixed mirror 14Y. _e1 And a measurement beam Y against the reflecting surface of the wafer stage (WS1 or WS2). _e2 , And the displacement of the wafer stage reflecting surface with respect to the fixed mirror 14Y is measured based on the interference state in which the reflected lights of these two beams are overlapped and interfered with each other.
[0059]
Further, the third laser interferometer 26Xa has a reference beam X in the X-axis direction passing through the detection center of the alignment microscope WA with respect to the X fixed mirror 18X. _a1 And a measurement beam X against the reflecting surface of the wafer stage (WS1 or WS2) _a2 , And the displacement of the wafer stage reflecting surface with respect to the fixed mirror 18X is measured based on the interference state in which the reflected lights of these two beams are overlapped and interfered with each other.
[0060]
Further, the fourth laser interferometer 26Ya has a reference beam Y in the Y-axis direction passing through the detection center of the alignment microscope WA with respect to the Y fixed mirror 18Y. _a1 And a measurement beam Y against the reflecting surface of the wafer stage (WS1 or WS2). _a2 , And the displacement of the wafer stage reflecting surface with respect to the fixed mirror 18Y is measured based on the interference state in which the reflected lights of these two beams are overlapped and interfered with each other.
[0061]
Where reference beam X _e1 And measuring beam X _e2 The measurement axis of the first laser interferometer 26Xe comprising the first measurement axis Xe and the reference beam Y _e1 And measuring beam Y _e2 The measurement axis of the second laser interferometer 26Ye comprising the second measurement axis Ye and the reference beam X _a1 And measuring beam X _a2 The measurement axis of the third laser interferometer 26Xa comprising the third measurement axis Xa and the reference beam Y _a1 And measuring beam Y _a2 If the length measuring axis of the fourth laser interferometer 26Ya is called the fourth length measuring axis Ya, the first length measuring axis Xe and the second length measuring axis Ye are the projection center of the projection optical system PL ( The third measurement axis Xa and the fourth measurement axis Ya intersect perpendicularly at the detection center of the alignment microscope WA. As a result, as described later, the position detection mark (alignment mark) on the wafer W is not affected by the Abbe error due to the yawing of the wafer stage or the like when the pattern is exposed on the wafer W. The position of the wafer stage can be accurately measured in each measurement axis direction. In order to improve the measurement accuracy, it is more desirable to use a two-frequency heterodyne interferometer as the first to fourth laser interferometers.
[0062]
Returning to FIG. 1, the measurement value of the interferometer system 26 is supplied to the main controller 28. The main controller 28 monitors the measurement value of the interferometer system 26, and the wafer stage WS1, via the linear motor described above. The position of WS2 is controlled.
[0063]
As is apparent from FIG. 3, in the case of the first embodiment, while the reticle pattern is exposed to the wafer W on the wafer stage WS1 or WS2 via the projection optical system PL, the first, While the position of the wafer stage is managed by the second laser interferometers 26Xe and 26Ye and the position detection mark (alignment mark) on the wafer W is measured by the alignment microscope WA, the third and fourth laser interferences are performed. The position of the wafer stage is managed by the total 26Xa and 26Ya. However, after the exposure is finished or after the alignment mark measurement is finished, each measuring axis does not come into contact with the reflecting surface of the respective wafer stage, so that the position management of the wafer stage by the interferometer system 26 becomes difficult. .
[0064]
For this reason, in the projection exposure apparatus 100 of this embodiment, the wafer stage WS1 is moved to the third position indicated by the phantom line in FIG. 3, the second position indicated by the solid line in FIG. 3, and the wafer stage in FIG. The first robot arm 20 as a moving means that freely moves between three positions with respect to the first position where WS2 is located, and similarly, the wafer stage WS2 is moved to the first position, the second position, and the third position. And a second robot arm 22 as moving means for freely moving between the three points. The first and second robot arms 20 and 22 are also controlled by the main controller 28, and the position control accuracy of the wafer stage of the first and second robot arms 20 and 22 is about ± 1 μm. . As these robot arms 20 and 22, articulated robot arms having a known configuration are used, and detailed description thereof is omitted. In order to reliably realize the above-described position control accuracy, FIG. Vertical movement pins as indicated by reference numerals 24A and 24B may be provided together as a stopper.
[0065]
Here, the third position, the second position, and the first position will be briefly described. The third position refers to the relationship between the transfer arm 50 and the wafer stage (WS1, WS2) that constitute a part of the external substrate transfer mechanism. This means a wafer exchange position where the wafer W is transferred between them, and the second position is a position where the wafer W on the wafer stage is aligned after the loading of the wafer W is completed. Both the long axis Xa and the fourth measuring axis Ya mean an arbitrary position that hits the reflecting surface of the wafer stage. The first position means that the wafer W on the wafer stage is exposed after the wafer alignment is completed. It means an arbitrary position where both the first measuring axis Xe and the second measuring axis Ye hit the reflecting surface of the wafer stage.
[0066]
In the present embodiment, as described above, the positions shown in FIG. 3 are defined as the first position, the second position, and the third position, respectively. If satisfied, any position may be determined. For example, the position where the mark WM on the reference mark plate FM is within the detection region of the alignment microscope WA may be set as the second position. Similarly, the first position may be any position as long as the above definition is satisfied. For example, the position where the mark RM on the reference mark plate FM is within the projection area of the projection optical system PL is determined. One position may be used.
[0067]
Next, an overall operation flow of the projection exposure apparatus 100 of the present embodiment configured as described above will be described.
[0068]
(1) As a premise, it is assumed that wafer stage WS1 is in the third position and wafer stage WS2 is in the first position.
[0069]
First, the wafer is exchanged between wafer stage WS1 and transfer arm 50. This wafer exchange is performed in the same manner as in the prior art by the center up (wafer up mechanism) on the wafer stage WS1 and the transfer arm 50. Therefore, although detailed description is omitted here, as described above, the robot Since the arm positioning accuracy is approximately ± 1 μm or less, it is assumed that the positioning accuracy of the transfer arm 50 is substantially the same. Prior to this wafer exchange, the wafer W is roughly positioned in the X, Y, and θ directions by a pre-alignment apparatus (not shown), and the load position on the wafer stage is not greatly shifted. The load position of the wafer W is also within the error range of ± 1 μm or less.
[0070]
During the wafer exchange, the position of the wafer stage WS1 is not managed by the laser interferometer, but the first robot arm 20 catches the wafer stage WS1, so that the wafer stage WS1 goes to an arbitrary place. Does not occur. It is assumed that the linear motor that drives the wafer stage WS1 is stopped while being captured by the first robot arm 20 (the same applies hereinafter).
[0071]
When the wafer exchange (loading of wafer W onto wafer stage WS1) is completed, main controller 28 controls first robot arm 20 to move wafer stage WS1 to the second position indicated by the solid line in FIG. At this position, the third and fourth laser interferometers 26Xa and 26Ya are reset simultaneously. When this reset is finished, the first robot arm 20 finishes its role here, so that the first robot arm 20 leaves the wafer stage WS1 by a drive system (not shown) in response to an instruction from the main controller 28. Evacuated to a position where it does not get in the way.
[0072]
After the resetting of the third and fourth laser interferometers 26Xa and 26Ya, the main controller 28 monitors the measurement values of the interferometers 26Xa and 26Ya, and marks WM on the reference mark plate FM1 on the wafer stage WS1. Is positioned within the detection region of the alignment microscope WA by controlling the position of the wafer stage WS1 via the linear motor described above. Here, the positioning accuracy to the second position by the first robot arm 20 can be approximately ± 1 μm or less as described above, and the interference measurement major axis is reset at this second position. Position control is possible based on the design value (relative design relationship between the reflecting surface of wafer stage WS1 and the mark WM on the reference mark plate) with a resolution of about 0.01 μm. As a result, alignment microscope WA The wafer stage WS1 is positioned with sufficient accuracy for the mark WM measurement. When the second position is set to a position at which the mark WM on the reference mark plate FM1 on the wafer stage WS1 is positioned in the detection area of the alignment microscope WA, the wafer stage WS1 after the interferometer reset is performed. This movement is more desirable in terms of throughput.
[0073]
Next, the position (ΔW) of the mark WM on the reference mark plate FM1 with reference to the detection center (index center) of the alignment microscope WA by the alignment microscope WA. _X , ΔW _Y ) Is measured, and the main controller 28 determines the average value (X of the measured values of the third and fourth laser interferometers 26Xa and 26Ya during the measurement). ₀ , Y ₀ ) As a result, the measured values of the laser interferometers 26Xa and 26Ya become (X ₀ -ΔW _X , Y ₀ -ΔW _Y ) Indicates that the mark WM on the reference mark plate FM1 is directly below the detection center (index center) of the alignment microscope WA. A series of operations after resetting the third and fourth laser interferometers 26Xa and 26Ya will be referred to as W-SET in the following.
[0074]
In this way, while a series of operations of wafer exchange, interferometer reset and W-SET are performed on one wafer stage WS1, the following operations are performed on the other wafer stage WS2.
[0075]
That is, the wafer stage WS2 is moved to the first position by the second robot arm 22 as described above, and the positioning control to the first position is also performed with an accuracy of ± 1 μm or less. At the same time as the movement of wafer stage WS2 to the first position is completed, main controller 28 resets first and second laser interferometers 26Xe and 26Ye.
[0076]
When the resetting of the first and second laser interferometers 26Xe and 26Ye is finished, the second robot arm 22 finishes its role here, so that the second robot arm responds to an instruction from the main controller 28. Then, the wafer stage WS2 is moved away from the wafer stage WS2 by a drive system (not shown).
[0077]
Next, the main controller 28 monitors the measurement values of the laser interferometers 26Xe and 26Ye, and the reticle alignment in which the mark RM on the reference mark plate FM2 is formed on the reticle R within the projection area of the projection optical system PL. The position of wafer stage WS2 is controlled via a linear motor so as to be positioned at a position overlapping a mark (not shown) via a projection optical system. In this case, the positioning accuracy to the first position by the second robot arm 22 can be approximately ± 1 μm or less as described above, and the interference measurement major axis is reset at this first position. Position control is possible based on design values (relative design relationship between the reflecting surface of wafer stage WS2 and mark RM on fiducial mark plate FM2) with a resolution of about 0.01 μm, resulting in reticle alignment. The wafer stage WS2 is positioned with sufficient accuracy to simultaneously observe the reticle alignment mark and the mark RM on the reference mark plate FM with the microscopes 52A and 52B.
[0078]
Next, the relative intervals (ΔRX, ΔRY) between the reticle alignment mark on the reticle R and the mark RM on the reference mark plate FM2 by the reticle alignment microscopes 52A and 52B, that is, as a predetermined reference point in the projection area of the projection optical system PL. Position difference (ΔR) from the center of the reference mark RM, which is the reference point on the wafer stage WS2, with respect to the projection center of the pattern image of the reticle R _X , ΔR _Y ) Is measured, and the main controller 28 takes in the measurement values of the reticle alignment microscopes 52A and 52B, and at the same time the measurement values (X of the laser interferometers 26Xe and 26Ye at that time) ₁ , Y ₁ ). As a result, the measured values of the laser interferometers 26Xe and 26Ye are (X ₁ -ΔR _X , Y ₁ -ΔR _Y ) Is a position where the reticle alignment mark and the mark RM on the reference mark plate FM2 are exactly overlapped via the projection optical system PL. A series of operations after the reset of the first and second laser interferometers 26Xe and 26Ye will be referred to as R-SET below.
[0079]
(2) Next, wafer alignment on the wafer stage WS1 side and exposure on the wafer stage WS2 side are performed in parallel.
[0080]
That is, after the above-described reset of the third and fourth laser interferometers 26Xa and 26Ya, the position of the wafer stage WS1 is managed based on the measurement values of the laser interferometers 26Xa and 26Ya. Measurement of the position detection mark (alignment mark) position of a predetermined specific sample shot among a plurality of shot areas on the wafer W is performed via a linear motor while monitoring the measurement values of the interferometers 26Ya and 26Xa. The wafer stage WS1 is sequentially moved and performed on the (Xa, Ya) coordinate system based on the output of the alignment microscope WA. In this case, the measured value (X of the interferometer when the mark WM on the reference mark plate FM1 is directly below the detection center of the alignment microscope WA. ₀ -Δ _X , Y ₀ -Δ _Y In order to position each alignment mark on the wafer W within the detection area of the wafer alignment microscope WA based on this value and the design value of the relative position of the reference mark WA and each alignment mark. The position at which the measured values of the laser interferometers 26Ya and 26Xa should be moved is determined by calculation, and the wafer stage WS1 is sequentially moved based on the calculation result.
[0081]
In order to align X, Y, and θ of the wafer W, it is sufficient to measure at least two X measurement marks and one Y measurement mark (or one X measurement mark and two Y measurement marks). Here, as an EGA sample shot, it is assumed that three or more X measurement marks that are not on a straight line and three or more Y measurement marks that are not on a straight line are measured.
[0082]
Then, using the measured alignment mark (wafer mark) position of each sample shot and the design shot area arrangement data, the least square method disclosed in, for example, Japanese Patent Application Laid-Open No. 61-44429 is used. Statistical calculation is performed to obtain all array data of the plurality of shot areas on the wafer W. However, the calculation result is based on the interferometer value (X) when the mark WM on the reference mark plate FM1 obtained earlier is just below the detection center of the alignment microscope WA. ₀ -Δ _X , Y ₀ -Δ _Y It is desirable to convert the data into data based on the reference mark WA on the reference mark plate FM1. Thus, the relative positional relationship between the mark WM on the reference mark plate FM1 and the reference point of each shot area on the wafer W is necessary and sufficiently understood.
[0083]
In this way, in parallel with the fine alignment (EGA) being performed on the wafer stage WS1 side, on the wafer stage WS2 side, the pattern image of the reticle R and the existing shot area on the wafer W are formed as follows. Overlay exposure with the pattern is performed.
[0084]
That is, in the main controller 28, the measurement result of the positional deviation error, the coordinate position (Xe, Ye) of the wafer stage WS2 at that time, and the reference mark plate FM2 calculated in advance in the same manner as described above by the alignment operation. While observing the measurement values of the interferometers 26Ye and 26Xe on the basis of the array coordinate data of each shot with the upper reference mark WA as a reference, each shot area on the wafer W is positioned at the exposure position, and the illumination optical system The reticle pattern is sequentially exposed on the wafer W by the step-and-repeat method while controlling the opening and closing of the inner shutter. Here, prior to exposure of the wafer W on the wafer stage WS2, the interferometers 26Xe and 26Ye are reset (the length measurement axis of the interferometer is temporarily cut), but high-precision overlaying is performed. The reason why it is possible will be described in detail. The distance between the mark WM and the mark RM on the reference mark plate FM2 is known, and the reference mark plate FM2 is subjected to fine alignment (EGA) performed prior to this in the same manner as described above. The relative positional relationship between the upper mark WM and the reference point of each shot area on the wafer W is calculated, and where the reticle alignment mark on the reticle R is present on the reticle R (that is, the projection optical system). The projection center of the reticle pattern image, which is a predetermined reference point in the projection area of PL (substantially coincident with the projection center of projection optical system PL), and wafer stage W (Relative positional relationship with the mark RM, which is the reference point on 2) is also measured, and based on these measurement results, what value the measured values of the first and second laser interferometers 26Xe and 26Ye will be? This is because it is clear whether the pattern image of the reticle R and each shot area on the wafer W exactly overlap.
[0085]
(3) As described above, fine alignment (EGA) is completed on the wafer stage WS1 side, and when exposure of the reticle pattern to all shot areas on the wafer W is completed on the wafer stage WS2 side, the wafer stage WS1 is projected. The wafer stage WS2 is moved to a first position below the optical system PL, and the wafer stage WS2 is moved to a third position which is a wafer exchange position.
[0086]
That is, the wafer stage WS1 is captured by the first robot arm 20 in accordance with an instruction from the main controller 28 and moved to the first position. The positioning control to the first position is also performed with an accuracy of ± 1 μm or less. At the same time as the movement of wafer stage WS1 to the first position is completed, main controller 28 resets first and second laser interferometers 26Xe and 26Ye.
[0087]
When this reset is finished, the first robot arm 20 finishes its role here, so that the first robot arm 20 leaves the wafer stage WS1 by a drive system (not shown) in response to an instruction from the main controller 28. Evacuated to a position where it does not get in the way.
[0088]
Next, main controller 28 performs R-SET in the same manner as wafer stage WS2 described above. As a result, the relative distance (ΔR) between the reticle alignment mark and the mark RM on the reference mark plate FM1. _X , ΔR _Y ), That is, a positional deviation (ΔR) from the center of the reference mark RM which is the reference point on the wafer stage WS2 with respect to the projection center of the pattern image of the reticle R as a predetermined reference point in the projection area of the projection optical system PL. _X , ΔR _Y ) And the stage coordinate position (X ₁ , Y ₁ ) Is measured.
[0089]
As described above, while the interferometer reset and R-SET are performed on the wafer stage WS1 side, the second robot arm 22 performs the wafer stage WS2 in which the exposure operation has been completed in response to an instruction from the main controller 28. The wafer stage WS2 is moved to the wafer transfer position (third position) for wafer replacement and the wafer is exchanged, and the wafer exchange, interferometer reset, and W-SET are performed in the same manner as the wafer stage WS1 described above.
[0090]
(4) Next, in the main controller 28, in the same manner as described above, on the wafer stage WS2 side, the reticle pattern is sequentially exposed on the wafer W by the step-and-repeat method on the wafer stage WS1 side. The operations of both stages are controlled so that fine alignment (EGA) is performed.
[0091]
(5) After that, the operations of the stages WS1 and WS2 and the operations of the first and second robot arms are performed by the main controller 28 so that the operations (1) to (4) described so far are sequentially repeated. Operation is controlled.
[0092]
FIG. 4 shows the flow of the parallel operation performed on both stages WS1 and WS2 described above.
[0093]
As described above, according to the projection exposure apparatus 100 according to the first embodiment, the exposure operation on one stage side of the wafer stage WS1 and the wafer stage WS2 and the fine alignment operation on the other stage side are performed in parallel. Therefore, a significant improvement in throughput can be expected as compared with the conventional technique in which wafer exchange (including search alignment), fine alignment, and exposure are performed sequentially. This is because the ratio of time required for the fine alignment operation and the exposure operation is usually large in the exposure processing sequence.
[0094]
Further, according to the above embodiment, since the length measurement axis of the interferometer system 26 is assumed to be cut, the length of the reflecting surface of each wafer stage (the moving mirror when a moving mirror is used) is determined from the wafer diameter. Since the slightly longer length is sufficient, the wafer stage can be made smaller and lighter than the conventional technology that presupposes that the length measurement axis must not be cut, which improves stage control performance. Be expected.
[0095]
Furthermore, in the above-described embodiment, it is assumed that the measurement axis of the interferometer system is cut, and the mark position on the reference mark plate FM on the stage is measured before alignment and before exposure, so the projection of the projection optical system PL There is no particular inconvenience no matter how long the distance between the center and the detection center of the alignment microscope WA (baseline amount) increases. The distance between the projection optical system PL and the alignment microscope WA is sufficiently separated to a certain extent. Wafer alignment and exposure can be performed in parallel in time without causing interference with wafer stage WS2.
[0096]
In the above-described embodiment, the first measurement axis Xe and the second measurement axis Ye that intersect perpendicularly at the projection center of the projection optical system PL, and the third measurement axis that intersects perpendicularly at the detection center of the alignment microscope WA. Since the interferometer system 26 includes Xa and the fourth measurement axis Ya, the two-dimensional position of the wafer stage can be accurately managed during both the alignment operation and the exposure.
[0097]
In addition, since the fixed mirrors 14X, 14Y, 18X, and 18Y for interferometers are fixed to the side surface of the projection optical system PL and the side surface of the alignment microscope WA, unless the fixed mirror position varies during alignment measurement and exposure. Even if the position of the fixed mirror fluctuates due to a change with time, vibration of the apparatus, or the like, there is no inconvenience such as a decrease in the position control accuracy of the wafer stage due to this fluctuation. Therefore, for example, even if the alignment microscope WA is configured to be movable up and down, no inconvenience occurs.
[0098]
In the first embodiment, the first and second robot arms 20 and 22 are used to move the wafer stage WS1 and the wafer stage WS2 between the first position, the second position, and the third position. However, the present invention is not limited to this. For example, when the wafer is exchanged at the second position, the first and second robot arms 20 and 22 are used to change the wafer stage WS1 and the wafer. The stage WS2 may be moved between the first position and the second position. In this case, in main controller 28, the exposure operation of wafer W on one of wafer stage WS1 and wafer stage WS2 and the alignment operation of wafer W on the other stage are performed in parallel. Thus, after controlling the operation of both stages, the positions of both stages are switched by the first and second robot arms 20 and 22.
[0099]
In the first embodiment, the case where the exposure of the step-and-repeat method is performed on the wafer W on the stage based on the EGA measurement has been described. Thus, the pattern image of the reticle may be projected and exposed to each shot area on the wafer W while repeating alignment and exposure. Even in this case, since the relative position of each alignment mark with respect to the mark WM formed on the reference mark plate FM on the stage is measured during alignment, each shot area is similarly determined based on this relative position. A reticle pattern image can be superimposed on the surface. Such a die-by-die method is desirably employed when the number of shot areas on the wafer W is small. When the number of shot areas is large, it is preferable to use the EGA described above from the viewpoint of preventing a reduction in throughput.
[0100]
In the first embodiment, the first robot arm 20 moves one stage WS1 between the first position, the second position, and the third position, and the second robot arm 22 moves to the other position. Although the case where the stage WS2 is moved between the three positions of the first position, the second position, and the third position has been described, the present invention is not limited to this. For example, one of the robot arms 20 is moved to the stage WS1 (or WS2) is transported from the first position to the third position and released to a certain position other than the first position, the second position, and the third position, and the other robot arm 22 releases the stage WS1 (or WS2) to this position. By adopting a method such as moving from the first to the third position, one robot arm 20 is dedicated to transfer between the second position and the first position of both stages, and the other robot arm 2 is moved to the third position. It is also possible to transport only the third position and the second position of the stage.
[0101]
Further, as each laser interferometer constituting the interferometer system 26, a multi-axis interferometer may be used to measure not only the X and Y translational positions of the wafer stage but also yawing and pitching.
[0102]
<< Second Embodiment >>
Next, a second embodiment of the present invention will be described with reference to FIG. Here, the same reference numerals are used for the same or equivalent components as those in the first embodiment described above, and descriptions thereof are omitted.
[0103]
In the second embodiment, the wafer stage WS1 is configured to be separable into two parts: a stage main body WS1a and a substrate holding member WS1b having the same shape that can be attached to and detached from the stage main body WS1a. Similarly, the wafer stage WS2 However, it is characterized in that it is configured to be separable into two parts: a stage main body WS2a and a substrate holding member WS2b of the same shape that can be attached to and detached from the stage main body WS2a.
[0104]
On the substrate holding members WS1b and WS2b, a wafer W is sucked and held via a wafer holder (not shown), and a reflecting surface functioning as an interferometer moving mirror is formed on each side surface. The substrate holding members WS1b and WS2b are provided with reference mark plates FM1 and FM2 on the upper surfaces thereof.
[0105]
In the second embodiment, parallel processing is performed on the wafer stages WS1 and WS2 in substantially the same manner as the first embodiment described above, but the alignment operation is completed on one stage side, and the other stage side is finished. When the exposure operation is completed, the first and second robot arms 20 and 22 are controlled by the main controller 28, and the stage-side substrate holding member WS1b (or WS2b) after the alignment operation is stopped at the first position. Concurrently with transporting (moving) onto the stage main body WS2a, the stage-side substrate holding member WS2b (or WS1b) after exposure is transported onto the stage main body WS1a stopped at the second position. In this manner, the substrate holding members WS1b and WS2b are exchanged. When the substrate holding members WS1b and WS2b are replaced, the length measurement axis of the interferometer system 26 is cut, so that the position management of the wafer stages WS1 and WS2 becomes impossible. During this time, the stage stoppers 30a and 30b come out and both stages The main bodies WS1a and WS2a are held in their positions. In this case, the wafer exchange is performed at the second position by a transfer arm (not shown).
[0106]
Here, in the second embodiment, as can be easily imagined from FIG. 5, as the second position, for example, the position where the mark WM on the reference mark plate FM is in the detection region of the alignment microscope WA is the first position. As positions, the positions at which the marks RM on the reference mark plate FM are within the projection area of the projection optical system PL are respectively determined. Accordingly, the main controller 28 causes the substrate holding members WS1b and WS2b to be placed on the stage body. Along with the movement, the measurement axis of the interferometer system 26 is reset and R-SET or W-SET is performed.
[0107]
According to the second embodiment, the same effect as that of the first embodiment can be obtained.
[0108]
In the second embodiment, the case where the first and second robot arms 20 and 22 move the substrate holding member between the first position and the second position has been described. However, the first and second robots are described. The arms 20 and 22 may move the substrate holding member between three points of the first position, the second position, and the third position, as in the first embodiment. In this case, the wafer exchange can be performed at a place unrelated to the projection optical system PL and the alignment microscope WA. There are no inconveniences such as obstacles.
[0109]
In the first and second embodiments, the case where a robot arm or a stage stopper is used is described as a countermeasure when the measuring axis of the interferometer system 26 is temporarily cut. However, the present invention is not limited to this. For example, a two-dimensional grating may be engraved on the lower surface of the wafer stage, and the position may be read with an optical encoder from below the stage running surface, and the stage can be accurately moved to the next position with the interference measurement long axis once broken. Any means may be used as long as it can be moved or can hold the stage main body at a predetermined position.
[0110]
In the first and second embodiments, the case where two wafer stages that move independently are provided, but three or more wafer stages that move independently may be provided. When three wafer stages are provided, for example, an exposure operation, an alignment operation, and a wafer flatness measurement operation can be performed in parallel. A plurality of projection optical systems PL and alignment microscopes WA may be provided. When there are a plurality of projection optical systems, an alignment operation and an exposure operation of two types of patterns different from each other can be performed in parallel, which is suitable for so-called double exposure.
[0111]
Furthermore, in the above-described embodiment, the case where the present invention is applied to a step-and-repeat type projection exposure apparatus is illustrated, but the scope of the present invention is not limited to this, and the present invention is a so-called step. Of course, the present invention can be applied to other exposure apparatuses such as an electron beam direct writing apparatus as well as an AND-scan type projection exposure apparatus.
[0112]
【The invention's effect】
As explained above, The present invention According to the invention, it is possible to improve the throughput and to provide an unprecedented excellent exposure method capable of determining the size of the substrate stage regardless of the baseline amount.
[0113]
Also, Book According to the invention, there is an effect that the throughput can be improved by performing the exposure operation on one substrate stage and the alignment operation on the other stage in parallel.
[Brief description of the drawings]
FIG. 1 is a drawing schematically showing an overall configuration of an exposure apparatus according to a first embodiment.
2 is a schematic plan view of one wafer stage of FIG. 1. FIG.
FIG. 3 is a schematic plan view of the apparatus of FIG.
FIG. 4 is a diagram showing an operation flow in the apparatus of FIG. 1;
FIG. 5 is a schematic plan view showing a configuration of a main part of an exposure apparatus according to a second embodiment.
[Explanation of symbols]
14X, 18X X fixed mirror (fixed mirror)
14Y, 18Y Y fixed mirror (fixed mirror)
20 First robot arm (moving means)
22 Second robot arm (moving means)
26 Interferometer system
28 Main controller (control means)
50 Transfer arm (part of substrate transfer mechanism)
52A, 52B reticle alignment microscope (mark position detection means)
100 exposure equipment
WS1a, WS2a Stage body
WS1b, WS2b Substrate holding member
FM1, FM2 Reference mark plate
WM, RM reference mark
R reticle (mask)
W wafer (sensitive substrate)
PL projection optical system
WS1 Wafer stage (first substrate stage)
WS2 wafer stage (second substrate stage)
WA alignment microscope (alignment system)
Xe First measuring axis
Ye Second measuring axis
Xa 3rd measuring axis
Ya 4th measuring axis

Claims (4)

An exposure method in which an image of a pattern formed on a mask is exposed on a sensitive substrate via a projection optical system,
Prepare two substrate stages that can hold the sensitive substrate and move independently in the same plane,
Exposing the pattern image of the mask on the sensitive substrate held on one of the two substrate stages via the projection optical system;
During exposure of the sensitive substrate held on the one substrate stage, an alignment mark on the sensitive substrate held on the other of the two substrate stages and a reference point on the other stage Measure the positional relationship,
After the exposure of the sensitive substrate held on the one substrate stage, the reference point on the other substrate stage is positioned in the projection area of the projection optical system, and the predetermined reference point in the projection area is set. Detecting a positional shift of a reference point on the other substrate stage and a coordinate position of the other substrate stage;
Based on the measured positional relationship, the detected displacement and the detected coordinate position, the movement of the other substrate stage is controlled, and the pattern image of the sensitive substrate and the mask held on the other stage There line alignment with,
Each of the substrate stages has a stage main body and a substrate holding member that is detachably mounted on the main body and holds the substrate, a reflection surface for an interferometer is provided on a side surface of the substrate holding member, and A reference mark is formed as the reference point on the upper surface of the substrate holding member,
Exposure method characterized by after completion of exposure of the sensitive substrate held on the one substrate stage, the replacement of the substrate holding member of the one and the other stage is performed. The position information of the two substrate stages is measured by an interferometer system,
The alignment mark on the sensitive substrate is detected by an alignment system at a position away from the projection optical system,
The interferometer system includes a first measurement axis and a second measurement axis that intersect perpendicularly at the projection center of the projection optical system, and a third measurement that intersects perpendicularly at the detection center of the alignment system. An axis and a fourth measuring axis,
2. The exposure method according to claim 1, wherein the length measuring axis of the interferometer system is reset when the positions of the substrate holding members of the one stage and the other stage are switched. The replacement The exposure method according to claim 1 or 2 carried out by the robot arm. 4. The exposure method according to claim 2 , wherein each of the projection optical system and the alignment system is provided with a fixed mirror serving as a reference for length measurement by an interferometer. 5.

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