JPH1187228A - Aligner and method of exposure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aligner and the exposure method, which can remove alignment errors, even if a substrate and a substrate holder shrink during the exposure and can realize highly accurate exposure. SOLUTION: An aligner has a substrate holder 14, wherein each of a plurality of regions Wi on a substrate W is exposed in a pattern and mounts the substrate W, a substrate stage 13 which supports the substrate holder 14, a stage- position measuring device 21 which measures the position of the substrate stage 13, and a relative position measuring device 24 which measures the deviation in relative posiation of the substrate stage 13 and the substrate holder 14. Since the relative position measuring device 24 is provided, the relative position deviation of the substrate stage 13 and the substrate holder 14 can be measured. The position of the substrate stage 13 measured with the stage-position measuring device can be corrected by just this amount of deviation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus and an exposure method for projecting and exposing a mask (reticle) pattern onto a photosensitive substrate, and more particularly, to an exposure apparatus and method used for manufacturing a semiconductor device or the like in a photolithography process. The present invention relates to an exposure apparatus and an exposure method.

[0002]

2. Description of the Related Art In a conventional apparatus of this type, the position of an XY stage on which a wafer holder is mounted is detected by an interferometer, and the XY control is performed by a main controller based on the information.
The position of the stage is controlled to align the wafer. Further, as disclosed in Japanese Patent Application Laid-Open No. 4-96315, the irradiation energy absorbed by the wafer or the wafer holder is measured while the reticle pattern is sequentially transferred onto the wafer by the step-and-repeat method. , Calculate the expansion and contraction of the wafer holder etc. due to the heat,
The shot position determined prior to the transfer is corrected.

[0003]

According to the above prior art, when a wafer holder mounted on an XY stage is deformed by irradiation of exposure light, the wafer held by the wafer is attracted to the wafer holder. Also affect. However, the pattern position (shot position) on the conventional wafer
Was measured by a reference mirror and an interferometer mounted on an XY stage. According to this method, the interferometer can measure the position of the XY stage,
No consideration is given to the deformation (expansion) of the wafer holder mounted on the XY stage, that is, the deformation of the wafer mounted thereon caused by the deformation. Therefore, an error occurs between the target stage position and the actually driven stage position, that is, the wafer position, by the deformation of the wafer holder. In other words, even if the stage is positioned at the target position based on the output of the interferometer, an error corresponding to the expansion of the wafer holder occurs,
The alignment accuracy of each area on the wafer (the area where the mask pattern is transferred) with respect to the pattern of the mask has been deteriorated. Even if the shot position is corrected by measuring the irradiation energy absorbed by the wafer holder and calculating the expansion and contraction of the wafer holder and the like due to the heat, the calculated value cannot avoid an error with respect to the actual expansion and contraction. There is a problem that the projected image of the image does not exactly overlap with the shot area on the wafer.

Accordingly, the present invention is directed to an exposure apparatus and an exposure apparatus capable of realizing high-precision exposure by removing an alignment error due to such expansion and contraction even when a substrate such as a wafer or a wafer (substrate) holder expands and contracts during exposure. It is intended to provide a way.

[0005]

In order to achieve the above-mentioned object, an exposure apparatus according to the first aspect of the present invention will be described with reference to FIGS.
As shown in FIG. 1, an exposure apparatus 10 for exposing each of a plurality of regions Wi on a substrate W in a pattern; a substrate holder 14 on which the substrate W is placed; a substrate stage 13 for supporting the substrate holder 14; A stage position measuring device 21 for measuring the position of the substrate stage 13; and a relative position measuring device 24 for measuring a relative displacement between the substrate stage 13 and the substrate holder 14.

With this configuration, since the relative position measuring device 24 is provided, the substrate stage 13 and the substrate holder 14 are provided.
Can be measured, and the position of the substrate stage 13 measured by the stage position measuring device 21 can be corrected by the amount of the deviation.

In the present invention, as described in claim 2,
It is preferable that the relative position measuring device is configured to measure at least three relative positional deviations.

In this case, since three relative displacements are measured, two-dimensional information on the substrate stage can be obtained.

In the above invention, the control for controlling the movement of the substrate stage based on the measurement values of the stage position measuring device and the relative position measuring device during the exposure of the substrate, according to a third aspect of the present invention. A device may be further provided.

In the exposure apparatus according to the first or second aspect, as in the fourth aspect, the alignment apparatus detects a plurality of marks on the substrate and measures each position of the plurality of marks. And detecting each position of the plurality of regions based on the measured position, and during exposure of the substrate, based on a measurement value of the relative position measurement device,
The apparatus may further include a control device that corrects the detected position and controls the movement of the substrate stage according to the corrected position.

With the above configuration, since the control device is provided, the movement of the substrate stage can be controlled based on the measured value.

In the exposure apparatus according to any one of the first to fourth aspects, as in the fifth aspect, a projection optical system for projecting the image of the pattern onto the substrate; And an adjusting device for adjusting at least one of magnification and distortion of the pattern image based on a measurement value of the relative position measuring device.

[0013] With this configuration, an error can be suppressed to a predetermined value or less by adjusting one of the magnification and distortion of the pattern image that is largely changed.

In the exposure method according to the present invention, as shown in FIGS. 1, 2 and 3, the substrate stage 13 on which the substrate holder 14 holding the substrate W is mounted is moved to Each of the plurality of regions Wi
A step of detecting each position of the plurality of regions Wi on the substrate W (S1); and measuring a relative displacement between the substrate stage 13 and the substrate holder 14 during the exposure. (S2) correcting the detected position based on the measured relative displacement (S3); and controlling the movement of the substrate stage 13 according to the corrected position (S4). ).

In this way, the relative position shift can be measured, and the detected position of the region Wi on the substrate W can be corrected based on the relative position shift.

The exposure method according to claim 7 is applied to the method shown in FIGS.
And a method of exposing each of a plurality of regions Wi on a substrate W mounted on a substrate holder 14 mounted on a substrate stage 13 with a pattern of a mask 11, as shown in FIG. Detecting each position of Wi; correcting the detected position based on the amount of deformation of the substrate holder 14 during the exposure; exposing at least one of the plurality of regions Wi with the pattern. Moving the substrate stage 13 based on the corrected position.

In this manner, the positions of the plurality of detected areas Wi can be corrected based on the amount of deformation of the substrate holder 14, so that the exposure area can be moved from the first exposure area to another area. When the substrate stage 13 is moved, the substrate stage 13 can be moved after correcting, for example, a thermal deformation error that occurs with time based on the corrected position.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic side view of an exposure apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged plan view taken along the line AA of FIG. 1 (as viewed from above the wafer W).

In the present embodiment, in the present embodiment, a substrate (for example, a wafer, hereinafter referred to as “wafer” as appropriate) holder 14 and a substrate stage (hereinafter also referred to as “XY stage” as appropriate) 13 to which the wafer holder 14 is attached are provided. A measurement system (gap sensor or strain gauge) 24 for measuring the relative displacement and feeding it back to the XY position control of the XY stage is provided.

For this reason, while the wafer W is exposed by the step-and-repeat method (or the step-and-scan method) using the mask (reticle) 11, the wafer W
The wafer holder 14, that is, the wafer W is deformed (expanded) by the transfer of the pattern of the reticle 11 to the wafer (irradiation of exposure light).
However, by using the output of the measurement system 24,
It is possible to correct the displacement of the wafer W on the XY stage 13 positioned according to the output of the interferometer 21 with respect to a predetermined target position.

More specifically, based on the output of the measurement system 24 (the amount of deformation or the deformation rate of the wafer holder 14), the wafer W is accurately aligned with the target position measured or calculated in advance. XY stage 1
The XY stage 13 is moved according to the corrected coordinate position (target value) and the output of the interferometer 21. Thus, even if the wafer W is deformed due to the thermal expansion of the wafer holder 14, the wafer W can be accurately aligned (aligned) with the target position.

In this embodiment, the gap between the wafer holder 14 on the XY stage 13 and a predetermined portion in the vicinity thereof is monitored by a gap sensor as a measuring system 24, and the output of the gap sensor 24 is sent to the main control system 25. The main control system 25 corrects the positioning information (the positioning target value of the XY stage 13).

As a result, while the position of the wafer W has been adjusted only by the position information of the XY stage 13 in the past, the position of the wafer W due to the deformation of the wafer holder 14 mounted on the XY stage 13 has been changed. By adopting a configuration that takes into account even the positional deviation, the wafer W
Can be improved.

Here, while the reticle 11 and the wafer W are kept still, the reticle 1 is exposed to exposure light (for example, a KrF excimer laser having a wavelength of 248 nm or an ArF excimer laser having a wavelength of 193 nm) emitted from the illumination optical system 15.
In a step-and-repeat type reduction projection exposure apparatus that irradiates the wafer W with a pattern image of the reticle 11 via the projection optical system 12, that is, a stepper, the above-described target position is the projection of the pattern image of the reticle 11. Position.

On the other hand, a reticle 11 and a wafer W are synchronously moved, and a step-and-scan type reduction projection type scanning exposure apparatus for exposing the wafer W with a pattern image of the reticle 11 via a projection optical system 12, a so-called scanning stepper. The target position is a scanning start position (acceleration start position) of the wafer W for scanning exposure or an exposure start position.

The scanning start position (acceleration start position)
It is set at a predetermined distance in the scanning direction of the wafer W from a part of the projection field (image field) of the projection optical system 12, for example, a rectangular area extending along the diameter and centered on the optical axis in a circular projection field. Is done. This predetermined distance is XY
It is determined according to the acceleration of the stage 13, the speed of the wafer W during scanning exposure (synchronous movement), and the like.

The rectangular area in the projection visual field is conjugated with respect to the projection optical system 12 to an illumination area (exposure light irradiation area) on the reticle 11 defined by a field stop (reticle blind) in the illumination optical system 15. And is an area in the illumination area where a part of the pattern on the reticle 11 is projected.

As described above, regardless of the stepper or the scanning stepper, when the pattern image of the reticle 11 of the first layer is sequentially transferred onto the wafer W,
The wafer W can be accurately aligned with the pattern image, thereby preventing a decrease in arrangement accuracy (for example, orthogonality) of a plurality of pattern images formed on the wafer W.
When transferring the pattern images of the second and subsequent layers of the reticle onto each of a plurality of patterns formed on the wafer W, the pattern images must be accurately superimposed on each pattern on the wafer W. Can be.

Referring to FIG. 1, the configuration of the present embodiment will be described more specifically. In FIG. 1, first, a three-dimensional X
Set the YZ coordinates. The X-axis and the Y-axis orthogonal to each other are set in a plane perpendicular to the Z axis and the Z axis in the vertical direction. In the figure, the Z axis is taken in the vertical direction in the paper plane, the X axis is taken in the horizontal direction in the paper plane, and the Y axis is taken in the direction perpendicular to the paper plane.

In FIG. 1, a projection optical system 12 having an optical axis in a direction parallel to the Z axis, and an illumination optical system 15 above the direction of the optical axis substantially aligns the optical axis with the optical axis of the projection optical system 12. Are located.

The illumination optical system 15 includes an optical integrator (such as a fly-eye lens), an aperture stop that defines the size and shape of the secondary light source, a field stop (reticle blind) that defines an illumination area on the reticle 11, a condenser lens, and the like. The reticle 11 is illuminated with illumination light in an ultraviolet wavelength range for exposing the photoresist on the wafer W, for example, a KrF excimer laser having a wavelength of 248 nm. The double-sided telecentric projection optical system 12 has a plurality of optical elements (for example, lens elements) arranged along the optical axis, and reduces and projects the image of the pattern of the reticle 11 irradiated with the illumination light onto the wafer W. .

Between the illumination optical system 15 and the projection optical system 12, a reticle stage (not shown) on which a mask (which may be a reticle, and is hereinafter appropriately referred to as a "reticle") 11 is placed. I have. Further, regarding the projection optical system 12,
A wafer holder 14 for adsorbing and holding a substrate (wafer) W is arranged at a position opposite to the reticle stage, and the wafer holder 14 is attached to a wafer stage 13 therebelow (the side opposite to the projection optical system with respect to the wafer W). ing. Here, the pattern surface of the reticle 11 and the exposure surface (for example, the surface of the photoresist) of the wafer W are configured to have a conjugate relationship with respect to the projection optical system 12.

In the X-axis and Y-axis directions of the XY stage 13,
A stage interferometer 21 that measures the position coordinates of the stage 13 in each direction is provided. On the other hand, a fixed mirror 22 attached to the inside of the exposure apparatus main body, for example, the projection optical system 12
And the movable mirror 2 attached to the end of the XY stage 13
3 are prepared. The movable mirror 23 has reflecting surfaces extending in the Y direction and the X direction for reflecting the laser beam from the interferometer 21, and is orthogonally defined by two sets of interferometers 21 for the X axis and the Y axis. X to coordinate system XY
Since it moves together with the Y stage 13, it is called a movable mirror.

At least two lens elements of the projection optical system 12 are each supported by three piezo elements (not shown), and are configured to be movable and tiltable along the optical axis of the projection optical system 12. . The drive unit 26 is connected to a plurality of piezo elements that support the at least two lens elements, and drives the at least two lens elements according to a command from the main control system 25. Thus, the projection magnification and distortion (distortion) of the projection optical system 12 can be independently adjusted.

Therefore, in the projection exposure apparatus (stepper) of this embodiment, at least one lens element of the projection optical system 12 is moved based on the size and shape (distortion) of the pattern formed on the wafer W. By adjusting at least one of the projection magnification and the distortion, the pattern image of the reticle 11 of the second layer or later on the pattern on the wafer W can be accurately superimposed over the entire surface.

When the pattern image of the reticle 11 for the first layer is transferred onto the wafer W, the thermal expansion of the wafer holder 14 caused by the transfer, that is, the deformation amount (or deformation rate) of the wafer W is measured in advance. Alternatively, the projection optical system 12 may be obtained by simulation and based on the data.
By adjusting at least one of the projection magnification and distortion of the wafer W, even if the wafer W is deformed during the exposure, the wafer W
It is possible to minimize the magnification error and the image distortion of the pattern of the first layer formed thereon.

It is to be noted that the distortion of the first layer pattern formed on the wafer W and the pattern formed on the wafer W and the pattern image of the reticle 11 can be obtained only by adjusting the magnification of the projection optical system 12 alone. Can be reduced respectively.

Here, the method of adjusting the magnification or distortion of the pattern image of the reticle 11 is not limited to the movement of the lens element of the projection optical system 12, but may be, for example, the projection optical system 1.
The magnification of the pattern image projected on the wafer W may be changed by sealing the space between the two lens elements in 2 and adjusting the pressure in the space.

Further, the optical distance (interval) between the reticle 11 and the projection optical system 12 is changed.
1 is slightly moved in the direction of the optical axis of the projection optical system 12, or the thickness of a parallel flat plate disposed between the reticle 11 and the projection optical system 12 is changed, so that a pattern image projected on the wafer W is formed. May be adjusted.

In the scanning stepper, during the scanning exposure, the reticle 11 and the wafer W are moved at a speed ratio corresponding to the projection magnification of the projection optical system. Therefore, the scanning stepper adjusts the speed ratio to correct a magnification error between the pattern on the wafer W and the pattern image of the reticle 11 in the scanning direction of the wafer W, and moves the lens element of the projection optical system 12. By doing so, a magnification error in a direction orthogonal to the scanning direction can be corrected.

Further, for example, during the scanning exposure, the magnification of the pattern image of the reticle 11 in the direction orthogonal to the scanning direction of the wafer W is changed continuously or stepwise, or the scanning direction of the reticle 11 and the scanning of the wafer W are changed. By shifting the direction, the distortion of the reticle pattern formed on the wafer W is adjusted, whereby the first layer pattern can be formed on the wafer W without being distorted. Can be accurately overlapped with the pattern on the wafer W over the entire surface.

The projection exposure apparatus (stepper) shown in FIG.
Has an off-axis alignment sensor 27. The alignment sensor 27 irradiates an alignment mark on the wafer W with broadband light (non-exposure light), and forms an image of the mark on an index plate. Further, an image of the alignment mark and an image of the mark on the index plate are formed on a light receiving surface of an image pickup device (CCD), and the amount of displacement between the two mark images is detected. The detected positional deviation amount is output to the main control system 25, and the main control system 25 also uses the output of the interferometer 21 to determine the position of the alignment mark on the rectangular coordinate system XY defined by the interferometer 21. To detect.

In this embodiment, the reticle 1 is used for a pattern formed in each of a plurality of rectangular areas on the wafer W.
Prior to superimposing and transferring the one pattern, a plurality of alignment marks on the wafer W are respectively detected using the alignment sensor 27, and the main control system 25 statistically calculates a plurality of mark positions. The positions of the upper plurality of rectangular areas on the orthogonal coordinate system XY are determined.

The main control system 25 is connected to a driving device (not shown) for driving the stage interferometer 21 and the XY stage 13 so that signals can be transmitted. It is configured so that movement can be controlled.

Further, on the XY stage 13, near the wafer holder 14, a gap sensor 24 as a relative position measuring device of the present invention is installed. Gap sensor 2
4 is a non-contact type sensor in which a coil is wound around an iron core called a capacitance sensor, an optical photo sensor, a proxy core, a main scale provided on one of the XY stage and the wafer holder, and a sub-scale provided on the other. An image processing device using a CCD (Vernier method), a strain gauge, or an interferometer similar to the stage interferometer 21 in a special case may be used.

The gap sensor 24 is connected to the main control system 25 by a lead wire (not shown), and can transmit a measured value of the measured relative displacement between the XY stage 13 and the wafer holder 14 to the main control system 25. It is configured as follows.
In the main control system 25, the measurement value of the stage interferometer 21 can be corrected based on the received relative displacement.

The operation of the exposure apparatus 10 having the above configuration will be described with reference to FIGS. XY stage 13
X and Y of the stage 13 are fixed by a fixed mirror 22 attached to the projection optical system 12 and a movable mirror 23 on the XY stage 13 by a position control interferometer 21 installed in the X-axis and Y-axis directions, respectively. The position in the Y direction is constantly controlled.

When it is desired to move the XY stage 13 to a desired target position, the main control system 25 operates the driving device of the XY stage 13 based on the output of the interferometer 21 to move the XY stage 13 to the target position. Position.

When exposing the wafer W, the irradiation energy of the exposure light causes the wafer holder 14 and the wafer W to expand. Therefore, the gap sensor 24 provided on the XY stage 13 measures how much the wafer holder 14 has expanded and displaced relative to the XY stage 13. That is, the relative positional relationship between the XY stage 13 and the wafer holder 14 is measured. The information is sent to the main control system 25, and the XY stage 1
By correcting the position (target value) where 3 should be positioned,
It is possible to prevent the wafer W from being shifted from the original position due to the expansion of the wafer holder 14.

A specific method of positioning the wafer W will be described. As shown in FIG. 2, an XY stage 13;
The expansion of the wafer holder 14 is monitored by a gap sensor 24 such as a capacitance sensor for measuring the positional relationship with the wafer holder 14 provided thereon.

The number of gap sensors 24 used for measurement is
It is desirable that a plurality of sensors be provided so as to surround the periphery of the wafer holder 14 because the positional shift of the wafer holder 14 can be grasped in detail (FIG. 2 shows four gap sensors arranged at 90 ° intervals with respect to the center of the wafer holder 14). Is). It is desirable to have at least three. If there are three, the two-dimensional displacement information of the wafer holder 14 with respect to the XY stage 13, for example, the offset of the center position of the wafer W in the X and Y directions, the expansion and contraction of the wafer W in the X and Y directions, the plurality of shot areas on the wafer W The degree of orthogonality of the array and the like can be known.

Further, if a larger number of gap sensors are provided, it is convenient to know the expansion and contraction of each part of the wafer W. This means that the wafer W is exposed in a step-and-repeat manner using the reticle 11, in other words, the transfer position of the pattern of the reticle 11 on the wafer W (that is, the irradiation position of the exposure light that has passed through the reticle 11 and the projection optical system 12). ) Are sequentially moved, so that expansion and contraction do not occur uniformly in the wafer holder 14 but occur locally and anisotropically.

The gap sensor 24 is connected to the XY stage 13
In order to ascertain the positional relationship between the wafer holder 14 and the wafer holder 14, it is desirable to set them around the wafer holder 14 at regular intervals. For simplicity, a total of four wafer holders 14 may be provided so as to sandwich the wafer holder 14 on the X axis and the Y axis, as shown in FIG.

Next, an exposure method according to a second embodiment of the present invention will be described. In FIG. 3, first, a wafer W as a substrate to be exposed is placed on a wafer holder 14 (refer to FIG. 1 or 2 for the element number, the same applies hereinafter) (this placing step is not shown), and is carried out by vacuum suction. Hold.

Further, it is assumed that reticle 11 having the pattern of the first layer is mounted on a reticle stage, and wafer W is exposed by using the reticle 11 in a step-and-repeat manner. Therefore, the main control system 25 sets shot map data, that is, each of a plurality of areas on the wafer W to which the reticle pattern is to be transferred, based on the shot size and the step pitch stored in the memory by the operator. Determine the position.

Next, the main control system 25 uses the interferometer 21.
The XY stage 13 is moved according to the determined position, and the first area on the wafer W is aligned with the reticle 11. Thereafter, the reticle 11 is irradiated with the exposure light from the illumination optical system 15, and the first area on the wafer W is exposed with the pattern image.

At this time, since the reticle pattern has not been transferred to the wafer W prior to the exposure of the first area, the thermal expansion of the wafer holder 14, ie, the XY stage 13
No relative displacement between the wafer and the wafer holder 14 has occurred. Therefore, in the first area where the reticle pattern is first transferred onto wafer W, it is only necessary to position XY stage 13 in accordance with only the previously determined position.

However, for example, when the temperature of the wafer W is different from the temperature of the wafer holder 14, the wafer holder 14 may be deformed (expanded or contracted) due to the temperature difference even before the reticle pattern is transferred. Therefore, even in the first area on the wafer W, the output of the gap sensor 24 is monitored, and when the relative displacement between the XY stage 13 and the wafer holder 14 exceeds a predetermined allowable value. The XY stage 13 is moved in accordance with the position determined previously based on the positional deviation amount, and the corrected position. Thereby, the first region on the wafer W is accurately aligned with the reticle 11.

After the exposure of the first area is completed, the main control system 25 measures the relative displacement between the XY stage 13 and the wafer holder 14 using the gap sensor 24, and determines the relative displacement based on the measured value. The position of the second area on the wafer W is corrected.

Further, using the interferometer 21, the XY stage 13 is moved in accordance with the corrected position, and the reticle 1
The second region on the wafer W is aligned with respect to 1 and the second region is exposed with the pattern image of the reticle 11. Hereinafter, the above operation is repeatedly performed, and the reticle 1
All the regions on the wafer W are exposed with the one pattern image.

As described above, in this example, while the wafer W is exposed by the step-and-repeat method, the determined position is corrected for each area on the wafer W using the output of the gap sensor 24. For this reason, even if the wafer holder 14 is deformed (thermal expansion) due to the transfer of the reticle pattern onto the wafer W (irradiation of exposure light), the transfer position of the reticle pattern on the wafer W is sequentially shifted according to this deformation. That is, it is possible to prevent a decrease in the arrangement accuracy of the plurality of first layer patterns formed on the wafer.

Further, a plurality of first semiconductor elements formed on the wafer W
The reticle 11 of the second and subsequent layers is provided on each of the patterns of the layer.
In order to transfer the patterns in an overlapping manner, the EG
In the case of performing alignment between the reticle 11 and the wafer W using the A method, in this example, an arrangement error of a plurality of first layer patterns on the wafer W, particularly, a non-linear component can be reduced. It is possible to improve the alignment accuracy between the pattern of the reticle 11 using the pattern and each of the patterns of the plurality of first layers on the wafer W.

Next, an exposure method according to a third embodiment of the present invention will be described. As in the previous embodiment, first, a wafer W, which is a substrate to be exposed, is placed on a wafer holder 14 and held by vacuum suction.

In this example, the reticle 11 having the pattern of the second layer is placed on the reticle stage, and the pattern of the first layer formed in each of the plurality of regions on the wafer W is subjected to the second pattern. In order to transfer the patterns of the layers in an overlapping manner, an alignment method disclosed in JP-A-61-44429 or JP-A-6-196384, so-called enhanced global alignment (E
It is assumed that the wafer W is exposed by the step-and-repeat method using the reticle 11 for the second layer using the GA) method.

Therefore, the main control system 25 uses the interferometer 21 and the alignment sensor 27 to select at least three regions on the wafer W as alignment shots, and is formed adjacent to each of the selected alignment shots. The positions of the two alignment marks in the X and Y directions are detected. Further, at least six measured mark positions are statistically calculated using the least squares method, and the wafer W
Six parameters of a model formula (function) representing the arrangement of the plurality of regions above are obtained. Then, based on the obtained model function having the six parameters and the design positions of the plurality of regions on the wafer W (the shot map data (positions) determined in the above-described second embodiment). , The position of each of the plurality of regions on the orthogonal coordinate system XY is calculated. The calculated position is stored in a memory in the main control system 25.

Further, the main control system 25 is disclosed in
As disclosed in Japanese Patent Publication No. 384, the X and Y of the wafer W among the six parameters obtained by the EGA method described above are used.
At least one lens element of the projection optical system 12 is moved via the drive unit 26 based on at least one of two parameters representing expansion and contraction in the direction.

Thus, the projection magnification of the projection optical system 12 is adjusted, and the magnification error between each of the plurality of regions on the wafer W and the pattern image of the second layer is corrected. In adjusting the magnification of the projection optical system 12, one of the two parameters representing the expansion and contraction or the average value of the two parameters may be used.

Next, the main control system 25 uses the interferometer 21 to move the XY stage 13 in accordance with the position calculated previously, and moves the reticle 11 for the second layer to the first area on the wafer W with respect to the reticle 11 for the second layer. Align. After that, the illumination optical system 15
The reticle 11 is irradiated with the exposure light from the substrate W, and the first area on the wafer W is exposed with the pattern image of the second layer. Thereby, the pattern image of the second layer is transferred while being superimposed on the pattern of the first layer formed in the first region.

At this time, since the transfer of the reticle pattern onto the wafer W has not been performed prior to the exposure of the first area, the XY stage is only used according to the previously calculated position, as in the second embodiment. 13 only needs to be positioned.

However, if the temperature of the wafer W is different from the temperature of the wafer holder 14, for example, the relative displacement between the XY stage 13 and the wafer holder 14 detected by the gap sensor 24 before the exposure of the first area. Is larger than a predetermined allowable value, the previously calculated position is corrected based on the positional deviation amount, and the XY stage 13 is moved according to the corrected position. Thereby, the first region on the wafer W is accurately aligned with the reticle 11.

Further, the wafer holder 14 is deformed (expanded or contracted) due to a temperature difference between the wafer W and the wafer holder 14.
That is, the size and shape of each region on the wafer W change. For this reason, even if the magnification of the projection optical system 12 is adjusted as described above, a magnification error or a shape error may occur between the first region (the pattern of the first layer) and the pattern image of the second layer. is there. Therefore, when the displacement amount detected by the gap sensor 24 before the exposure of the first region exceeds a predetermined allowable value, the size and shape of the first region are calculated based on the displacement amount, and Projection optical system 1 according to calculated values
2 move at least two lens elements. As a result, the projection magnification and distortion of the projection optical system 12 are adjusted, and the first layer pattern and the second layer pattern image formed in the first region are accurately superimposed over the entire surface. Will be.

The size and shape of the first area are obtained based on the output of the gap sensor 24 at each of a plurality of points (for example, four corners and the center) in the first area (by the EGA method described above). (Computed position), and can be obtained from the plurality of corrected positions.

After the exposure of the first area is completed, the main control system 25 measures the relative displacement between the XY stage 13 and the wafer holder 14 using the gap sensor 24, and calculates the relative displacement based on the measured value. The position of the second area on the wafer W is corrected, and the size and shape of the second area are calculated. Then, at least two lens elements of the projection optical system 12 are moved in accordance with the calculated size and shape, and the magnification and distortion of the second layer pattern image are adjusted.

Further, the XY stage 13 is moved using the interferometer 21 in accordance with the corrected position, and the reticle 1 is moved.
The second region on the wafer W is aligned with respect to 1 and the second region is exposed with the pattern image of the reticle 11. Hereinafter, the above operation is repeatedly performed, and the reticle 1
All the regions on the wafer W are exposed with the one pattern image.

As described above, in this example, while the wafer W is exposed by the step-and-repeat method, the determined position is corrected for each region on the wafer W using the output of the gap sensor 24, and The projection magnification and distortion of the projection optical system 12 are adjusted. Therefore, the wafer W
Even if the wafer holder 14 is deformed (thermal expansion) due to the transfer of the reticle pattern onto the wafer W (irradiation of exposure light), the transfer position of the reticle pattern on the wafer W is sequentially shifted in accordance with this deformation, and The magnification error and the shape error between each area of the reticle 11 and the pattern image of the reticle 11 are corrected, so that the pattern formed on the wafer W and the pattern image of the reticle can be accurately superimposed over the entire surface. it can.

In this example, the projection magnification and distortion of the projection optical system 12 are adjusted for each region on the wafer W. However, the amount of displacement detected by the gap sensor 24 is equal to or less than a predetermined allowable value. In this case, there is no need to adjust the projection magnification or distortion. Even when the positional deviation exceeds the allowable value, only the projection magnification of the projection optical system 12 is adjusted, and the magnification error and the shape error between the area (pattern) on the wafer W and the pattern image of the reticle 11 are adjusted. May be suppressed to a predetermined value or less.

Further, when only one of the size and the shape of the area on the wafer W is largely changed, only one of the projection magnification and the distortion of the projection optical system 12 is adjusted, and The magnification error and the shape error between the pattern and the pattern image of the reticle 11 may be respectively suppressed to a predetermined value or less.

In the above-described second embodiment, only the predetermined position of the XY stage 13 (and thus the wafer W) is corrected during the exposure of the wafer W. However, as in the third embodiment, At least one of the projection magnification and distortion of the projection optical system 12 is adjusted according to the output of the gap sensor 24, and the first layer formed on the wafer W, which is generated by the irradiation of the exposure light (the deformation of the wafer holder 14). Changes in the size and shape of the pattern may be minimized.

In the above-described second and third embodiments, the position of each region on the wafer W determined prior to exposure is corrected based on the output of the gap sensor 24, and the corrected position is determined. The XY stage 13 is moved according to the following. However, the XY stage 13 moves only in accordance with the determined position, and the alignment error between the pattern of the reticle 11 and the wafer W caused by the deformation (expansion or contraction) of the wafer holder 14 is caused by the gap sensor 24.
May be corrected by moving the reticle stage in accordance with the output of the reticle 11, that is, the amount of deformation of the wafer holder 14, and adjusting the position of the reticle 11 in a plane orthogonal to the optical axis of the projection optical system 12.

Further, in the above-described second and third embodiments, correction of the determined position is performed for each region on the wafer W,
The projection magnification and distortion of the projection optical system 12 are adjusted. However, the wafer holder 14
The position correction and the adjustment of the projection optical system 12 are performed for at least two regions depending on the deformation speed (difference between the heat input amount and the heat release amount of the exposure light in the wafer W or the wafer holder 14 and the heat capacity of the wafer holder 14). You may do so. For example, when the position correction is performed for each of two regions, the position of the first region is corrected from the output of the gap sensor 24 before the exposure of the first region, and the correction amount obtained in the first region is corrected in the next region. (Ie, the difference between the predetermined position of the first area and the corrected position) may be used as it is to correct the predetermined position. The adjustment of the projection magnification and the distortion is performed prior to the exposure of the first area, and it is not necessary to adjust the second area.

Further, since the plurality of regions on the wafer W are arranged in a matrix, the regions on the wafer W for which position correction and adjustment of the projection optical system 12 are performed with the same correction amount according to the arrangement. May be partially changed. That is, for a plurality of regions arranged in the same column (for example, the first column) on the wafer W, position correction and adjustment of the projection optical system 12 are performed for at least two regions. Position correction and projection optical system 1 in the last area of the row
2, the position correction and the adjustment of the projection optical system 12 are also performed in some areas from the beginning (or some areas from the second row) of the next row (second row). Each time, the position correction and the adjustment of the projection optical system 12 are performed. This is because the region on the wafer W where the reticle pattern is to be transferred includes the turning point of the stepping where the first row shifts from the second row to the second row.
This is because the exposure energy amount absorbed by the wafer (or the wafer W) is considered to be larger than that in other regions.

In the above-described second and third embodiments, the present invention is applied to a step-and-repeat type reduction projection exposure apparatus, that is, a so-called stepper. However, the present invention relates to, for example, JP-A-4-196513,
The present invention can be applied to a step-and-scan type reduced projection scanning exposure apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 4-277612 and the like, that is, a so-called scanning stepper, and similar effects can be obtained. In the scanning stepper, the target position at which the XY stage 13 (wafer W) should be positioned is the scan start position (acceleration start position) of the wafer W for scanning exposure, and the target position is determined based on the output of the gap sensor 24. By correcting the position, the exposure start position of the wafer W is adjusted. Thereby, the transfer position of the pattern formed on the wafer W by the scanning exposure is moved according to the deformation of the wafer holder 14 (wafer W).

Further, similarly to the above-described second and third embodiments, even in the case of the scanning stepper, an error caused by a change in the size or shape of the area on the wafer W and the pattern image of the reticle 11 ( Magnification error and shape error) can be corrected. That is, the reticle 11 and the wafer W are moved at a speed ratio according to the projection magnification of the projection optical system 12 during scanning exposure in the scanning stepper. Therefore, the scanning stepper adjusts the speed ratio according to the output of the gap sensor 24 to correct the magnification error between the pattern on the wafer W and the pattern image of the reticle 11 in the scanning direction of the wafer W, By moving at least one lens element of the projection optical system 12, a magnification error in a direction orthogonal to the scanning direction is corrected.

Also, like the stepper, the reticle 11,
Alternatively, the distortion of the pattern image may be adjusted by moving the lens element of the projection optical system 12. However, in the scanning stepper, during scanning exposure, the magnification of the pattern image of the reticle 11 in the direction orthogonal to the scanning direction of the wafer W is changed continuously or stepwise according to the shape of the region on the wafer W, or By shifting the scanning direction of the reticle 11 and the scanning direction of the wafer W, the distortion of the pattern image of the reticle 11 projected on the wafer W is adjusted.

Note that the scanning start position (acceleration start position) of the scanning stepper is centered on the optical axis within a part of the projection visual field (image field) of the projection optical system 12, for example, a circular projection visual field, and has a diameter thereof. Is set at a predetermined distance in the scanning direction of the wafer W from the rectangular area extending along the line. The predetermined distance is determined by the acceleration of the XY stage 13 (the maximum practical acceleration determined according to the vibration of the main body of the apparatus, the structure of the XY stage, and the like) and the scanning exposure (synchronization) determined according to the sensitivity of the photoresist. It is obtained by calculation or the like based on the speed of the wafer W during (moving).

The rectangular area in the projection field of view is conjugated with respect to the projection optical system 12 to the illumination area (illumination area of exposure light) on the reticle 11 defined by the field stop (reticle blind) in the illumination optical system 15. And is an area in the illumination area where a part of the pattern on the reticle 11 is projected.

Here, an EGA (Enhanced Global Alignment) method, which is an example of a method of detecting the exposure position of the wafer W, which can be used for detecting the position of the exposure region in the present invention, will be described.

In the EGA method, when exposing one wafer W, first, the positions of alignment marks associated with a plurality of shot areas on the wafer W are measured (sample alignment), and then the center position of the wafer W is measured. Of the X and Y directions, the expansion and contraction of the wafer W in the X and Y directions, the remaining rotation amount of the wafer W, and the orthogonality of the wafer stage (orthogonality of the arrangement of the shot areas), and the mark design position and This is determined by a statistical method based on the difference from the mark measurement position.

Then, based on the determined parameter values, the position of the shot area to be exposed is corrected from the design position, and the wafer stage is sequentially stepped.

In this EGA method, a small number (3 to 16) is compared with the total number of shots on the wafer W prior to wafer exposure.
After the position of the mark is measured, the detection and position measurement of the mark are not required thereafter, so that an improvement in throughput can be expected. Furthermore, if the number of samples of the mark to be measured is large, each mark detection error is statistically averaged,
Alignment accuracy increases.

In the present invention, since the error of the deformation of the wafer holder can be corrected for the position of the exposure area detected in this way, high-precision alignment can be performed.

Here, a correction method for printing a pattern on the wafer W will be described. When the wafer holder 14 and the wafer W are partially deformed by the irradiation energy by the exposure on the wafer W, the amount of the deformation is observed by the gap sensor 24 installed on the XY stage 13, and the result is obtained by the main control system 25. When the main control system 25 calculates the position control of the XY stage 13, the XY stage 13 is positioned by adding the deformation amount to the calculation as a correction amount.

Regarding the means for calculating the correction amount, when exposure is performed on the wafer W, the expansion due to irradiation does not occur isotropically from the center of the wafer W, but the exposure proceeds when the exposure is performed in one row. Therefore, the position of the previous shot and the correction amount are held for each shot, and the amount of deformation in the next printing position and the direction of the deformation from the shot position are mainly determined. The calculation is performed by the control system 25, and feedback is applied to the positioning of the XY stage 13.

At the time of normal printing, the exposure operation is performed by designating the step interval. Therefore, the position shift amount caused by the deformation of the wafer holder 14 is added to the step interval, and the XY stage 13 is aligned. In addition, it is possible to remove a factor of deterioration in overlay accuracy caused by deformation of the wafer holder 14.

As described above, according to the present invention, since the measurement system for measuring the relative positional relationship between the XY stage and the wafer holder is provided, XY which cannot be measured by the interferometer on the XY stage can be obtained. The relative positional deviation between the stage and the wafer holder is measured, and the positional information is given to the main control system and fed back to the position control system of the XY stage by the interferometer. In this way, it is possible to correct even the positional deviation of the wafer holder, which could not be measured only by the interferometer, and it is possible to prevent the overlay accuracy from being deteriorated due to the expansion of the wafer holder.

[0096]

As described above, according to the present invention, by performing the alignment taking into account the relative displacement between the substrate stage and the substrate holder, for example, the displacement due to the deformation of the substrate holder, the overlay accuracy can be reduced. Improvement can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic side view of an exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a plan view of the exposure apparatus shown in FIG.

FIG. 3 is a flowchart showing a flow of an exposure method according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Exposure apparatus 11 Reticle 12 Projection optical system 13 XY stage 14 Wafer holder 15 Illumination optical system 21 Stage interferometer 22 Fixed mirror 23 Moving mirror 24 Gap sensor 25 Main control system 26 Drive unit 27 Alignment sensor W Wafer

Claims (7)

[Claims] An exposure apparatus for exposing each of a plurality of regions on a substrate with a pattern; a substrate holder on which the substrate is mounted; a substrate stage supporting the substrate holder; An exposure apparatus, comprising: a stage position measuring device for measuring; and a relative position measuring device for measuring a relative displacement between the substrate stage and the substrate holder. 2. The apparatus according to claim 1, wherein the relative position measuring device has at least three
The exposure apparatus according to claim 1, wherein the exposure apparatus is configured to measure a relative positional shift between two places. 3. During exposure of the substrate, based on measurement values of the stage position measurement device and the relative position measurement device,
The exposure apparatus according to claim 1, further comprising a control device that controls movement of the substrate stage. 4. An alignment device for respectively detecting a plurality of marks on the substrate and measuring respective positions of the plurality of marks; and detecting each position of the plurality of regions based on the measured positions. A control device that corrects the detected position based on the measurement value of the relative position measurement device during the exposure of the substrate, and controls movement of the substrate stage according to the corrected position. The exposure apparatus according to claim 1. 5. A projection optical system for projecting an image of the pattern onto the substrate; and at least one of magnification and distortion of the pattern image based on a value measured by the relative position measuring device during exposure of the substrate. The exposure apparatus according to claim 1, further comprising: an adjustment device that adjusts the distance. 6. A method of exposing each of a plurality of regions on the substrate with a pattern of a mask by moving a substrate stage on which a substrate holder holding the substrate is mounted; each position of the plurality of regions on the substrate Detecting the relative position shift between the substrate stage and the substrate holder during the exposure, and correcting the detected position based on the measured relative position shift. An exposure method, wherein the movement of the substrate stage is controlled according to the corrected position. 7. A method of exposing each of a plurality of regions on a substrate mounted on a substrate holder attached to a substrate stage with a pattern of a mask; and detecting respective positions of the plurality of regions; Correcting the detected position based on the amount of deformation of the substrate holder during the exposure; and exposing at least one of the plurality of regions with the pattern based on the corrected position. Moving the substrate stage.
Exposure method.