JP2001092156A - Automatic alignment method for exposure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the alignment accuracy between a mask and a glass substrate of an exposure device until exposure. SOLUTION: In the alignment of the mask and the glass substrate, a target position forcibly offset with respect to a desired target position is set (S11) and first the mask and the glass substrate are aligned to the offset target position (S12, S13) and are then aligned to the desired target position (S14 to S18). The offset quantity of the target position is specified to the backlash of an alignment stage or above, by which the backlash is surely absorbed at the correction to the desired target position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic alignment method in an exposure apparatus, and more particularly, to a proximity exposure apparatus for transferring a mask pattern onto a substrate.
A method for aligning the mask and the substrate.

[0002]

2. Description of the Related Art Conventionally, for example, in a process of manufacturing a color liquid crystal panel, a proximity exposure method has been used in a process of forming a fine pattern on a glass substrate.
The proximity exposure method is a method in which a slight gap (proximity gap) is provided between a mask and a glass substrate, and the mask pattern is transferred onto the glass substrate by parallel light.

In the manufacturing process of the color liquid crystal panel, it is necessary to repeat the transfer of the mask pattern several times, and the alignment accuracy between the mask and the glass substrate occupies an important position in the exposure performance.

Therefore, after pre-alignment for preliminarily positioning the glass substrate conveyed to the exposure chuck with respect to a fixed mask, alignment for positioning the mask and the glass substrate with high accuracy has been performed.

In the alignment, alignment marks provided on both the mask and the glass substrate are simultaneously captured by the optical system, detected by the CCD sensor, and XY based on the displacement calculated from the detection result.
The alignment stage of θ is driven, and the above-described process is repeatedly performed until the deviation amount reaches an allowable value (see Japanese Patent Publication No. 2623366).

[0006]

However, since each of the XYθ alignment stages has a backlash, if the amount of correction is small and the alignment is completed before the backlash is removed, other alignment stages are completed after the alignment is completed. When vibration caused by the operation of a drive system (for example, a moving mechanism of an optical system for detecting an alignment mark) is transmitted, there is a possibility that a displacement occurs.

In particular, in an apparatus for exposing a large glass substrate, the backlash increases due to the increase in the size of the alignment stage, and the amount of displacement after the completion of the alignment tends to increase.

Accordingly, the present invention addresses such a problem, and even if another drive system operates after the alignment is completed,
It is an object of the present invention to provide an automatic alignment method in an exposure apparatus that can ensure position accuracy at the time of automatic alignment.

[0009]

To achieve the above object, an automatic alignment method in an exposure apparatus according to the present invention is directed to an automatic alignment method for aligning a mask and a substrate in an exposure apparatus for transferring a mask pattern onto a substrate. The method is configured to perform positioning toward a target position forcibly offset, and then perform positioning toward an intended target position.

Here, it is preferable that the forcible offset amount of the target position is equal to or larger than the backlash of the mask or substrate positioning drive system.

[0011]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows an alignment stage section in a proximity exposure type exposure apparatus according to the present embodiment, in which an exposure chuck 2 for sucking and holding a glass substrate 1 for a color liquid crystal panel and an exposure chuck 2 in an X direction. An alignment X stage 3 for driving, an alignment Y stage 4 for driving the exposure chuck 2 in the Y direction, an alignment θ stage 5 for driving the exposure chuck 2 in the θ direction, and raising the exposure chuck 2 Then, the glass substrate 1 is fixed to the mask 6.
, And optical detection systems 8 and 9 for detecting alignment marks provided at both ends of the glass substrate 1 and the mask 6, respectively.

As shown in FIG. 2A, the mask 6 is provided with # -shaped alignment marks 10 at both ends.
As shown in FIG. 2B, the glass substrate 1 is provided with X-shaped alignment marks 11 at both ends.

The exposure apparatus according to the present embodiment includes a loader section, a loader substrate transport robot, an exposure irradiator, a pre-alignment section, an unloader substrate transport robot, an unloader section, a mask holder section, etc., in addition to the alignment stage section. It consists of.

The basic operation of the exposure apparatus having the above configuration will be described with reference to the flowchart of FIG. First, the glass substrate 1
Is performed (S1). The loading / unloading refers to an operation of removing the glass substrate 1 from which exposure has been completed from the exposure chuck 2 and carrying it out, and an operation of transporting and mounting the glass substrate 1 to be exposed to the exposure chuck 2.

When the loading / unloading of the glass substrate 1 is completed, pre-alignment is performed (S
2). In the pre-alignment, the glass substrate 1 is preliminarily positioned on the exposure chuck 2 prior to an alignment operation described later.

For example, as shown in FIGS. 4 (a) and 4 (b), laser photoelectric switches 21a, 21b and 21 are provided at two positions on the leading edge of the glass substrate 1 in the transport direction and at one position on the side edge.
By scanning c, the edge of the glass substrate 1 on the exposure chuck 2 is detected at each of the three locations to calculate the transport shift amount, and the transport shift amount is corrected by the XYθ alignment stages 3 to 5.

In the pre-alignment, the alignment mark 11 of the glass substrate 1 may be positioned within the recognition field of view of the optical detection systems 8 and 9, and positional deviation within the recognition field is allowed. The quantity measurement and correction operations are each performed only once.

After the pre-alignment, the glass substrate 1 is brought closer to the mask 6 fixed above the exposure chuck 2 by raising the exposure chuck 2 (S3). Subsequently, control is performed such that a gap (proximity gap) between the mask 6 and the glass substrate 1 becomes a predetermined value (S
4). The proximity gap is controlled by detecting the gap amount between the mask 6 and the glass substrate 1 by using four gap detection sensors, and driving the tilt mechanisms arranged at three places in the plane according to the detected gap amount. It is done.

When the control of the proximity gap is completed, an alignment for positioning the mask 6 and the glass substrate 1 with high accuracy is performed (S5). The alignment is
The alignment mark 10 of the mask 6 and the glass substrate 1,
11 are superimposed at the same time by the optical detection systems 8 and 9, and the positions of the two parallel two lines of the # -type alignment mark 10 of the mask 6 and the respective lines of the X-type alignment mark 11 of the glass substrate 1 are obtained. This is a process of calculating the amount of displacement of the glass substrate 1 from the relationship, and correcting the amount of displacement using the XYθ alignment stages 3 to 5, and measuring and correcting the amount of displacement until the amount of displacement becomes an allowable value. repeat.

When the alignment is completed, the optical detection systems (detection microscopes) 8, 9 are retracted (S6), and exposure is performed (S7). When the exposure is completed, the exposure chuck 2 is lowered together with the glass substrate 1 (S8), and the process returns to the loading / unloading process (S1) of the glass substrate 1 so as to expose the next glass substrate 1.

Here, the alignment processing (S5) will be described in detail with reference to the flowchart of FIG. When the pre-alignment is completed, a forced offset target is set as the target position of the alignment, that is, the target of the relative position between the # -type alignment mark 10 and the X-type alignment mark 11 (S11).

The intended target position is the center of the # -shaped alignment mark 10, and the intersection of the X-shaped alignment mark 11 is corrected so as to overlap the center (see FIG. 6). A position that is separated from the center of the alignment mark 10 by a predetermined distance in a predetermined direction is set as a target at which the intersection of the X-shaped alignment marks 11 overlaps (see FIG. 7).

Here, the predetermined direction may be any direction, but it is preferable that the predetermined distance is equal to or larger than the backlash of the XYθ alignment stages 3 to 5 (positioning drive system). This is because if the correction is made to a position offset by more than the backlash from the intended target position, and if the correction is made from the offset position toward the intended target position, it is necessary to compensate for the backlash or more. This is because backlash can be reliably absorbed.

When the offset target position is set,
Next, from the detection results of the alignment marks 10 and 11, the amount of positional deviation from the offset target position is calculated (S12).

The optical detection systems 8 and 9 are configured such that an optical image on which the alignment marks 10 and 11 are superimposed is decomposed in two directions by a half mirror and then detected by a CCD linear image sensor. The sensor is
As shown in FIG. 8, the detection signals P and P 'of one pair of two parallel lines of the # -type alignment mark 10 and the detection signal Q of one line of the X-type alignment mark 11 are combined with each other. The alignment marks 10 and 11 are output based on the difference in reflectance.

Therefore, based on the detection signal from each CCD linear image sensor, the # -shaped alignment mark 10
X-shaped alignment mark 1 based on two parallel lines
1 is detected, and the X-shaped alignment mark 1 is detected.
The distance from each line to the target position is the amount of positional deviation, and correction to the target position is performed by causing each line of the X-shaped alignment mark 11 to pass through the target position by correction based on the amount of positional deviation. Will be

When the amount of displacement relative to the offset target position is calculated, XYθ is calculated according to the amount of displacement.
The alignment stages 3 to 5 are driven to correct to the offset target position (S13).

When the position of the glass substrate 1 after the pre-alignment is corrected to the offset target position by the above processing, the alignment target is returned to the center of the original # -shaped alignment mark 10 (S14). The amount of displacement of the glass substrate 1 with respect to the target is calculated (S15).

Then, XYθ is calculated based on the displacement amount.
The alignment stages 3 to 5 are driven to correct the displacement (S15). After the correction of the displacement, the calculation of the displacement is performed again (S16), and it is determined whether or not the calculated displacement is within the allowable range (S17).

Here, if the positional deviation is within the allowable range, the alignment processing is terminated. If the positional deviation is not within the allowable range, correction is performed again and the resulting positional deviation is reduced. Until the position shift amount falls within the allowable range, the shift amount detection → correction → shift amount detection is repeatedly performed.

At the time of alignment to the desired target position, the target is not passed by correction so that the target is not passed.
It is preferable that the correction amount for the detected positional deviation amount is limited in consideration of the drive variation, and the glass substrate 1 is driven in the same direction from the start to the end of the alignment with respect to the intended target position to drive in the target position.

As described above, in the alignment process, correction is first made to the offset target, and then correction is made from the offset position toward the original target, so that the alignment with respect to the target is always performed in a fixed direction. This is performed for a substantially constant distance, so that the backlash of the drive system can be reliably absorbed in the alignment processing. Therefore, even if an operation such as retreating the optical detection systems 8 and 9 is performed after the alignment process, it is possible to prevent the occurrence of a positional shift of the glass substrate due to the operation, thereby maintaining the accuracy at the time of completing the alignment. Exposure can be performed.

[0033]

As described above, according to the present invention, after the positioning is performed toward the target position forcibly offset,
With the configuration for performing alignment toward the intended target position, the direction and the amount of positional deviation can be made substantially constant when aligning with the intended target, regardless of positional variations in pre-alignment. Particularly, by setting the offset amount to be equal to or more than the backlash of the alignment drive system, the backlash can be absorbed in the alignment, and the exposure can be performed while maintaining the positional accuracy at the end of the alignment. is there.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an alignment stage of an exposure apparatus according to an embodiment.

FIG. 2 is a plan view showing an alignment mark provided on a mask and a glass substrate in the embodiment;
(A) is a diagram showing a # -shaped alignment mark of a mask,
(B) is a figure which shows the x-shaped alignment mark of a glass substrate.

FIG. 3 is a flowchart showing a basic operation of the exposure apparatus in the embodiment.

4A and 4B are diagrams showing the arrangement of laser photoelectric switches for performing edge detection in pre-alignment according to the embodiment, wherein FIG. 4A is a plan view and FIG. 4B is a side view taken along line AA ′ of FIG. It is.

FIG. 5 is a flowchart showing details of an alignment operation in the embodiment.

FIG. 6 is a plan view showing a state in which alignment marks are superimposed in a state corrected to an intended target in the embodiment.

FIG. 7 is a plan view showing a state in which an alignment mark is superimposed on an offset target and corrected in the embodiment.

FIG. 8 is a characteristic diagram showing a detection signal of an alignment mark in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Glass substrate 2 ... Exposure chuck 3 ... Alignment X stage 4 ... Alignment Y stage 5 ... Alignment θ stage 6 ... Mask 7 ... Tilt mechanism 8,9 ... Optical detection system 10,11 ... Alignment marks 21a-21c ... Laser photoelectric switch

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H097 GA45 KA03 KA12 KA20 KA29 LA12 5F046 BA02 DB05 FA11 FC04 FC05 FC08

Claims (2)

[Claims] 1. An exposure apparatus for transferring a mask pattern onto a substrate, comprising: an automatic alignment method for aligning the mask and the substrate, wherein the alignment is performed toward a target position forcibly offset. An automatic alignment method in an exposure apparatus, wherein the alignment is performed to a desired target position. 2. The auto-alignment method according to claim 1, wherein the forcible offset amount of the target position is equal to or more than a backlash of the mask or substrate alignment drive system.