JP2001313241A - Aligner and aligning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent focus shift due to flexure of a chuck at the time of aligning a large liquid crystal substrate. SOLUTION: A liquid crystal substrate, i.e., a plate W, is mounted on a large area chuck 4 and aligned while scanning in the direction of Y axis along with a mask M. Height position (Z position) of the holding face of the chuck 4 is previously measured at least four points by means of a Z sensor 6 and an elliptic paraboloid approximating the holding face of the chuck 4 is determined from three-dimensional coordinates thus obtained. Focus shift due to flexure of the chuck 4 is prevented by controlling the height position of the chuck 4 under scan alignment according to the proximate plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal exposure apparatus and method for exposing a substrate (plate) of a liquid crystal device such as a liquid crystal display panel.

[0002]

2. Description of the Related Art In a conventional liquid crystal exposure apparatus, when a chuck on a stage on which a plate as a substrate to be exposed is mounted is adjusted to a height of a focal position of an optical projection system, the plate is first placed on the chuck. Then, a test exposure in which the exposure is performed while changing the height of the chuck is performed.Based on the results of this test, the chuck height at which the image resolution is the highest is obtained, and this is used as a reference for the chuck height specific to the apparatus. Position.

At the time of actual exposure, the plate is placed on the chuck, and the chuck height reference position and
The XY stage is three-dimensionally moved to an arbitrary point position in the exposure area, autofocus is performed there, a difference amount from the chuck height reference position is calculated, and the chuck height is moved by the difference amount to perform optical focusing. Adjust to the focal position of the projection system.

During exposure of the exposure area, alignment processing and exposure are performed by fixing the chuck height at the chuck height position calculated by performing autofocus.

[0005]

However, according to the above prior art, there are the following unsolved problems. In recent years, the size of a plate used in a manufacturing process of a liquid crystal panel or the like has been increasing with the enlargement of a liquid crystal screen. In order to respond to this, the size of the chuck on which the plate is placed is also increasing in the liquid crystal exposure apparatus. However, if the chuck is made larger, the deflection of the chuck surface (holding surface) due to the own weight of the chuck itself, and the time of manufacture of the chuck, It is difficult to maintain the flatness of the chuck surface due to limitations in machining accuracy and the like. As a result, when the exposure process is performed with the plate placed on the bending chuck, a portion that is out of focus and a portion that is not in focus occur in the exposure area,
A reading defect of the alignment mark and an exposure defect occur (first problem).

In the case of multi-cavity manufacturing for manufacturing a plurality of liquid crystal screens from one plate, for example, four liquid crystal screens are manufactured from one plate.
When manufacturing liquid crystal screens for one sheet, there are four exposure areas on one plate. Therefore, in each exposure area, a reading error of the alignment mark and a deflection of the chuck are required so as not to cause an exposure defect. To correct for defocus, set auto focus to 4 per plate.
It has to be performed twice, and the throughput deteriorates (second problem).

The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and corrects a focus shift without deteriorating the throughput even when the chuck is enlarged and the chuck is bent. To avoid poor alignment mark reading and exposure.
An object of the present invention is to provide an exposure apparatus and an exposure method that can ensure high transfer accuracy and high productivity.

[0008]

To achieve the above object, an exposure apparatus according to the present invention comprises: an optical projection unit for projecting an original pattern onto a substrate; a holding surface for holding the substrate; and at least two holding surfaces. Substrate holding means having stage driving means for moving in a three-dimensional manner;
Measuring means for measuring the height position at each point; and at least four points of three points obtained based on the output of the measuring means.
It is characterized by having arithmetic means for calculating a three-dimensional geometric surface approximating the holding surface from the dimensional coordinates.

Preferably, the stage drive means is configured to control the height position of the holding surface with reference to a three-dimensional geometric surface approximating the holding surface.

The stage driving means may be configured to scan the holding surface in a predetermined direction in synchronization with the original.

[0011] The stage driving means may be configured to move the holding surface stepwise.

When the three-dimensional geometric surface is a spherical surface, a cylindrical surface, an elliptical surface,
It may be a one-lobe hyperboloid, a two-lobe hyperboloid, an elliptic paraboloid, a hyperboloid paraboloid or a toric surface.

An exposure method according to the present invention comprises the steps of measuring height positions of at least four points on a holding surface for holding a substrate to be exposed via optical projection means, and obtaining three-dimensional coordinates of each point. Obtaining a three-dimensional geometric surface approximating the holding surface from the obtained three-dimensional coordinates of at least four points, and changing a height position of the holding surface based on the obtained three-dimensional geometric surface. It is characterized by the following.

During the exposure of the substrate, the height position of the holding surface may be controlled based on the three-dimensional geometric surface while scanning the holding surface in a predetermined direction.

[0015]

In a substrate alignment and exposure process, a three-dimensional geometric surface approximating a holding surface of a chuck or the like bent by its own weight or the like is obtained, and the height position of the holding surface is controlled based on this. Thus, exposure can be performed with the substrate always positioned at the focus position of the optical projection unit.

Even when a holding surface such as a chuck is enlarged due to an increase in the size of a plate as a substrate to be exposed, as in the case of exposing a plurality of liquid crystal screens, defocus occurs due to deflection of the holding surface. Without this, it is possible to avoid poor reading and exposure of the alignment mark, so that high transfer accuracy can be ensured.

Further, the deflection of the holding surface is corrected by using a previously calculated three-dimensional geometric surface. Even in the case of multi-cavity, auto-focusing is required only once. There is an advantage that the focus shift can be prevented without deteriorating the throughput, as compared with the case where auto focus is performed twice.

As a result, the transfer performance and productivity of the liquid crystal exposure apparatus can be greatly improved, which can contribute to higher performance and lower cost of the liquid crystal device and the like.

[0019]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an exposure apparatus for a liquid crystal according to a first embodiment, which comprises an illumination optical system 1 for generating exposure light and a mask M which is an original on which a liquid crystal pixel pattern is formed. , A chuck 4 for holding a plate (liquid crystal substrate) W as a substrate on the XYZ stage 3, and an optical projection system as optical projection means disposed between the XYZ stage 3 and the mask stage 2. 5, the height position of the holding surface of the chuck 4, that is, the position in the Z-axis direction (chuck height position) is measured by a Z sensor 6 as a measuring means.

Illumination optical system 1, mask stage 2, XYZ
The stage 3, the alignment optical system (not shown), the autofocus optical system, various measurement systems, and the like are controlled by a controller 7 that controls the entire apparatus.

The XYZ stage 3 moves the chuck 4 holding the plate W in the X-axis direction perpendicular to the optical axis,
There is provided an XY drive system that moves two-dimensionally in the axial direction, and a stage drive unit that includes a Z drive system that moves the chuck 4 in the height direction, that is, the Z-axis direction. The controller 7 calculates three-dimensional coordinate data based on the XY position of the chuck 4 when the XYZ stage 3 is moved in the XY directions and the chuck height position (Z position) measured by the Z sensor 6. Processing means is provided for processing to obtain, for example, a three-dimensional geometric surface approximating the holding surface of the chuck 4 bent by its own weight.

Before the exposure cycle for exposing the actual plate is started, the chuck 4 on the XYZ stage 3 before placing the plate is adjusted to the height of the focal position of the optical projection system 5, and the XYZ stage 3 is adjusted. The controller 7 moves to an XY position arbitrarily determined by the controller 7 and measures the chuck height positions at at least four points using the Z sensor 6.

[0024] For example, as shown in FIG. 2, respectively at the point P ₁ to P _h on the chuck 4 to measure the chuck height position (Z position). An equation approximating a three-dimensional geometric surface with the three-dimensional coordinate data obtained from the XY position and the Z position of these points is derived, and the equation of the three-dimensional geometric surface is stored in the controller 7 in advance.

Thus, the chuck height position at any XY coordinates of the XYZ stage 3 can be obtained, and the three-dimensional geometric surface according to the above equation is used as the chuck height reference surface, and the XYZ stage is used during scan exposure or alignment. The Z drive system of the stage 3 is controlled, and the chuck 4
Height position (Z position) is controlled.

As a method of approximating a three-dimensional geometric surface, a spherical surface, a cylindrical surface, an elliptical surface, a one-lobe hyperboloid, a two-leaf hyperboloid, an ellipse paraboloid, a hyperboloid paraboloid, a toric surface, or the like can be adopted. . However, in the case of a chuck that is bent by its own weight, a method of approximation with an elliptic paraboloid is practical.

Coordinate data (x ₁ , y ₁ , z ₁ ) obtained from n measurement points on the chuck,..., (X _n , y _n ,
z _n ), the equation of the elliptic paraboloid for obtaining the approximate equation of the elliptic paraboloid by the least square method is f (x, y) = a ₀ x ² + a ₁ y ² + a ₂ x + a ₃ y + a ₄ (1) Height f of the approximate surface at each XY measurement coordinate
(X _i , y _i ) and height position coordinates z _i measured by the Z sensor
The residual between _{r i = f (x i,} y i) When -z _i (2), the residual sum of squares for all data (3)
It becomes an expression.

[0028]

(Equation 1)

To find an elliptic paraboloid by the least squares method
Is the parameter a such that Q is minimized.₀ , A₁ , A
_Two , A_Three , A_Four Ask for. To do so, the parameter a
₀ , A ₁ , A_Two , A_Three , A_Four Is considered as an independent variable.
It suffices that all partial derivatives become 0 at the same time.

[0030]

(Equation 2)

The above equation is converted to each parameter (a ₀ , a ₁ , a
₍₂ , a ₃ , a ₄ ) is calculated and summarized as equation (5).

[0032]

(Equation 3)

Further calculations are made as in equation (6).

[0034]

(Equation 4)

By solving this determinant, a ₀ , a
₁ , a ₂ , a ₃ and a ₄ are obtained, and an approximate equation of an elliptic paraboloid can be obtained.

By using this elliptical paraboloid as a chuck height reference plane unique to the apparatus, a focus shift (focus shift) due to the deflection of the chuck 4 is corrected.

At the time of actual exposure, first, the plate W is placed on the chuck 4 and the XYZ stage 3 is moved to a position in the exposure area arbitrarily set by the controller 7 to execute auto focus (not shown). Focus on W.

Next, XYZ in the actual exposure cycle
The operation of the stage 3 will be described. As shown in FIG. 3, in the case of scan exposure in which scanning is performed in the Y-axis direction, the Z position (high position) of the XYZ stage 3 during exposure is set so that the focal length with the plate W on the chuck 4 is always constant. Is controlled in accordance with the approximate surface.

That is, FIG. 3A is a diagram showing the XYZ stage 3 at the exposure start position. The chuck height position is determined by the above-described autofocus so that the plate W comes to the focal position of the optical projection system 5. Is controlled. FIG.
(B) shows the XYZ stage 3 during exposure, and the XYZ stage 3 is lowered from the Z position at the exposure start position shown in (a) of FIG. . FIG. 3C shows an XYZ stage 3 at the end of exposure.
The XYZ stage 3 is elevated from the Z position shown in FIG. 3B by an amount corrected by the approximate surface.

As described above, by driving the XYZ stage 3 in the Z-axis direction while exposing, and changing the chuck height position in accordance with the approximate surface, the plate W is always in the optical projection system 5 position.
Is kept at the focal position.

When a plurality of liquid crystal screens are manufactured from one plate, as shown in FIG. 4, the XYZ stage 3 moves stepwise in the X-axis direction to perform exposure. In the step processing performed when manufacturing three liquid crystal screens from one plate, two step movements are performed.

FIG. 4A shows the XYZ stage 3 when exposing the first liquid crystal screen. That is, the XYZ stage 3 is driven to the X position of the first sheet, and at this time, the correction amount of the Z position accompanying the movement in the X-axis direction is determined according to the approximate plane as in the Y-axis direction. FIG. 4B shows the XYZ stage 3 when exposing the second liquid crystal screen. The XYZ stage 3 exposes the first liquid crystal screen at the X step position shown in FIG. The XYZ stage 3 is lowered from the Z position by the amount corrected by the approximate surface. FIG. 4C shows the XYZ stage 3 at the exposure position of the third liquid crystal screen, and Z at the X step position for exposing the second liquid crystal screen shown in FIG. The XYZ stage 3 is elevated from the position by an amount corrected by the approximate surface.

As described above, even when the step movement in the X-axis direction is performed, the plate W is always kept at the focal position of the optical projection system 5 by driving the XYZ stage 3 up and down according to the approximate surface.

When the amount of deflection of the chuck 4 is large, the inclination in the X-axis direction and the Y-axis direction at the center position of the exposure area is calculated from the approximate surface, and the XYZ stage 3 is inclined as shown in FIG. Alternatively, the plate W may be controlled so as to be perpendicular to the optical projection system 5. As a result, it is possible to reduce the defocus in the same exposure area.

According to the embodiment of the present invention, by controlling the Z height position of the chuck based on the approximate surface obtained by the elliptic paraboloid, the defocus due to the deflection of the chuck at an arbitrary stage position is corrected. can do. In addition, since the reference surface of the chuck is determined in advance with an elliptic paraboloid, even when a plurality of liquid crystal screens are manufactured for one plate, defocus can be avoided by performing only one autofocus. .

FIG. 6 illustrates the second embodiment, which employs a method of measuring the chuck height position at four points on the chuck 4 and approximating the deflection of the chuck to a spherical surface. is there.

Four points P1 (x ₁ , y ₁ ) not on the same straight line
In _{~P4 (x 4, y 4)} , to measure the height position of the holding surface of the chuck 4 using Z sensors 6. Next, the four points (x, y, z) the center coordinates from the coordinate _{P0 (x 0, y 0,} z
₀ ) and the equation of a sphere of radius r is derived. By this, XY
The chuck height position at any XY coordinates of the Z stage 3 can be easily calculated, and the three-dimensional geometric surface calculated by the above equation is used as a chuck height reference surface,
Used during exposure and alignment.

Next, a method of calculating a spherical equation approximating the chuck surface will be described. When calculating the equation of a sphere, if four points near the same circumference are extracted as position coordinates, the approximate sphere may differ from the actual chuck shape because each point has a small difference in elevation in position coordinates. Therefore, as for the position to be measured, as shown in FIG. 6, the three points P1, P2 and P3 are preferably at the corners of the chuck 4, and the fourth point P4 is preferably near the center of the chuck 4. Here, the equation of the spherical surface is as shown in equation (7). ^{_{(X-x 0) 2 +}} (y-y 0) 2 + (z-z 0) 2 = r 2 (7)

The position coordinates of the four points measured by the Z sensor 6, P 1 (x ₁ , y ₁ ) to P ₄ (x ₄ , y ₄ ), are substituted into the equation (7), and the equations are summarized as follows. Equation (8) is obtained.

[0050]

(Equation 5)

[0051] determines that the radius r the center coordinates of the spherical be determined by solving the matrix equation _{P0 (x 0, y 0,} z 0). The equation is obtained by substituting the center coordinate P0 and the radius r into the equation (7), and using this as a chuck reference plane,
Exposure processing similar to that of the first embodiment is performed.

[0052]

Since the present invention is configured as described above, it has the following effects.

The chuck height position is controlled at the time of exposure or alignment by using a three-dimensional geometric surface approximating the previously calculated chuck surface as a reference surface of the chuck height position. For example, in scan exposure, by controlling the focus position of the pattern image so that the plate placed on the chuck always scans, even if the chuck is enlarged and the chuck is bent, it can cause a focus shift. Can be avoided.

As a result, extremely high transfer accuracy can be obtained without causing alignment mark reading defects or exposure defects.

Using a previously calculated solid geometric surface,
Since the deflection of the chuck is corrected, for example, in step-and-repeat exposure, auto-focus may be performed once for each plate, and deterioration of throughput can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an exposure apparatus according to a first embodiment.

FIG. 2 is a diagram illustrating an elliptic paraboloid approximation method according to the first embodiment.

FIG. 3 is a diagram illustrating scan exposure.

FIG. 4 is a diagram illustrating step-and-repeat exposure.

FIG. 5 is a diagram illustrating a case where an XYZ stage is tilted.

FIG. 6 is a diagram illustrating a spherical approximation method according to a second embodiment.

[Explanation of symbols]

 Reference Signs List 1 illumination optical system 2 mask stage 3 XYZ stage 4 chuck 5 optical projection system 6 Z sensor 7 controller

Claims (9)

[Claims] 1. An optical projection unit for projecting a pattern of an original onto a substrate, a substrate holding unit having a holding surface for holding the substrate, and a stage driving unit for moving the holding surface at least two-dimensionally, and the holding surface. Measuring means for measuring the height position at at least four points, and calculating means for calculating a three-dimensional geometric surface approximating the holding surface from the three-dimensional coordinates of at least four points obtained based on the output of the measuring means Exposure apparatus having: 2. The exposure apparatus according to claim 1, wherein the stage driving means is configured to control a height position of the holding surface with reference to a three-dimensional geometric surface approximating the holding surface. . 3. The exposure apparatus according to claim 1, wherein the stage driving means scans the holding surface in a predetermined direction in synchronization with the original. 4. The exposure apparatus according to claim 1, wherein the stage driving means is configured to move the holding surface stepwise. 5. The surface according to claim 1, wherein the three-dimensional geometric surface is a spherical surface, a cylindrical surface, an elliptical surface, a one-lobe hyperboloid, a two-leaf hyperboloid, an ellipse paraboloid, a hyperboloid paraboloid, or a toric surface. An exposure apparatus according to any one of claims 1 to 4. 6. A step of measuring height positions of at least four points on a holding surface for holding a substrate exposed through an optical projection means to obtain three-dimensional coordinates of each point;
Exposure having a step of obtaining a three-dimensional geometric surface approximating the holding surface from the obtained three-dimensional coordinates of at least four points, and a step of changing the height position of the holding surface based on the obtained three-dimensional geometric surface Method. 7. The exposure method according to claim 6, wherein a height position of the holding surface is controlled based on a three-dimensional geometric surface while scanning the holding surface in a predetermined direction during exposure of the substrate. . 8. The exposure method according to claim 6, wherein the holding surface is step-moved, and a height position of the holding surface is controlled based on a three-dimensional geometric surface. 9. The solid geometric surface is a spherical surface, a cylindrical surface, an elliptical surface, a one-lobe hyperboloid, a two-leaf hyperboloid, an elliptic paraboloid, a hyperboloid paraboloid, or a toric surface. 9. The exposure method according to any one of claims 8 to 8.