JPH09120986A - Pre-alignment method and pre-alignment apparatus - Google Patents

Abstract

(57) Abstract: Pre-alignment method and pre-alignment apparatus capable of accurately correcting the placement position of a circular sample on which a pattern is formed and also accurately correcting the placement angle of the pattern of the sample. I will provide a. A positional deviation between a stage 2C and a sample 1 is absorbed by shifting a standby position of a sample support member 8, and the sample 1 is placed on a regular position of the sample support member 8. Further, the shift angle between the direction of the stage 2C and the direction of the sample 1 is absorbed by shifting the standby direction of the sample support member 8, and the sample 1 is placed on the sample support member 8 in the regular direction. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prealignment method and a prealignment apparatus used when a sample such as a semiconductor photomask is transported to a sample stage.

[0002]

2. Description of the Related Art Conventionally, when a semiconductor wafer or a semiconductor photomask is transported to a sample stage of a manufacturing apparatus or an inspection apparatus, the positioning of the sample is performed based on either the outer shape of the sample or the pattern formed on the sample. I am doing it. In FIG. 8, 101 is a semiconductor photomask on which the pattern 101A is formed, 8 is a sample support member provided on the sample stage of the coordinate measuring machine, and FIG. 8 shows the semiconductor photomask 101 placed on the sample stage. It shows the state. The sample support member 8 has three protrusions and supports the photomask 101 at three points. When positioning the photomask 101 having a rectangular outer shape in this way, the center of the photomask 101 and the direction of the photomask 101 can be calculated from the outer shape of the photomask 101, so that the center of the photomask 101 and the sample support member 8 can be calculated. Match the center and pattern 101A
The photomask 101 can be placed on the sample support member 8 so that the photomask 101 faces a predetermined direction.

[0003]

However, as shown in FIG. 9, when the sample 201 has a circular shape, the center position of the sample 201 can be calculated by detecting the outer circumference of the sample 201. You can't find the direction. Therefore, as shown in FIG.
Cannot be corrected, and the pattern 201A on the sample is placed on the sample support member 8 while being inclined. When detecting the pattern 201A on the sample, the pattern 2
Although the direction and center position of 01A are calculated, the center of the sample itself is not accurately detected. Therefore, as shown in FIG. 11, the sample 201 is mounted with the center of the sample 201 and the center of the sample support member 8 displaced from each other by the amount of the displacement between the center of the pattern 201A and the center of the sample 201. Will be placed.

However, when the coordinates of the pattern 201A of the sample 201 placed on the sample support member 8 are measured in such a state, there are the following problems. That is, if there is variation in the direction of the pattern 201A with respect to the sample support member 8, the measurement point will differ for each individual sample, and the measurement accuracy will deteriorate. In addition, when the contact position of the sample support member 8 that supports the sample 201 changes, the way in which the sample 201 bends changes for each individual sample, resulting in a difference in measured values, which also deteriorates the measurement accuracy.

An object of the present invention is to provide a pre-alignment method and a pre-alignment apparatus which can accurately correct the placement position of a circular sample on which a pattern is formed and also accurately correct the placement angle of the pattern of the sample. To provide.

[0006]

FIG. 1 shows an embodiment of the present invention.
When the invention is described in association with claim 6, the invention according to claim 1 makes the sample table reference point provided on the sample table 5 coincide with the sample table reference point provided on the sample 1, and the sample table 5 is oriented in the sample table direction. On the sample table 5 so that the sample direction of
It is applied to the pre-alignment method for handing over. Then, the sample 1 is placed on the carrier 2C, and the positional deviation (δX, between the carrier reference point provided on the carrier 2C and the sample reference point
δY) is measured based on the outer peripheral shape of the sample 1, and the deviation angle δθ between the carrier direction of the carrier 2C and the sample direction is measured based on the pattern 1A on the sample 1, and the sample stand 5 is on standby. The sample base reference point is aligned with the correction points (LX-δX, LY-δY) corrected by the positional deviation from the standby reference point that is the position reference, and the sample table 5 is displaced from the standby direction Lθ that is the reference in the standby direction. With the sample stage 5 in the correction direction Lθ-δθ corrected by the angle δθ, with the sample stage direction aligned, the carrier reference point is aligned with the standby reference point, and the carrier direction is aligned with the standby direction. The above object is achieved by transferring the sample 1 from the carrier 2C to the sample table 5. In the invention according to claim 2, the sample table reference point provided on the sample table 5 and the sample table reference point provided on the sample 1 are matched, and the sample table direction of the sample table 5 and the sample direction of the sample 1 are matched. It is applied to the pre-alignment apparatus that transfers the sample 1 from the carrier 2C to the sample table 5 so as to perform the above.
Then, based on the outer peripheral shape of the sample 1, the carrier 2C that conveys the sample 1 to the sample table 5 and the positional deviation (δX, δY) between the carrier reference point provided on the carrier 2C and the sample reference point are determined. Measuring means 11, 12, 13, 14 for measuring the displacement angle δθ between the carrier direction of the carrier 2C and the sample direction based on the pattern on the sample, and a reference for the standby position of the sample table 5. The sample base reference point is aligned with a correction point (LX-δX, LY-δY) that is corrected by the positional deviation from the standby reference point that is The sample 1 is received from the carrier 2C to the sample table 5 with the sample table direction aligned with the corrected direction Lθ-δθ, and with the carrier reference point as the standby reference point and the carrier direction as the standby direction. Conveyor 2C and try to pass Control means for controlling the table 5 1
The above-mentioned object is achieved by including 4 and 4.

According to the first and second aspects of the invention, the positional deviation (δX, δY) between the carrier reference point and the sample reference point.
Is absorbed by the correction of the standby position of the sample table, and the sample is placed on the sample table with the sample reference point and the sample table reference point aligned. Further, the deviation angle δθ between the carrier direction and the sample direction is absorbed by the correction of the standby direction of the sample stage, and the sample is placed on the sample stage in a state where the sample direction and the sample stage direction match.

[0008] In the means and means for solving the above-mentioned problems which explain the constitution of the present invention, the drawings of the embodiments are used to make the present invention easy to understand. It is not limited to.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a pre-alignment apparatus according to the present invention will be described below with reference to FIGS.
As shown in FIGS. 1 and 2, a sample loader 2 that conveys a circular sample 1 on which a pattern 1A is formed has a rotation shaft 2B rotatably erected and a base end on the rotation shaft 2B. The fixed arm 2A and the sample 1 provided at the tip of the arm 2A
And a stage 2C on which is mounted, and the rotation and extension / contraction of the arm 2A are controlled by the loader control circuit 4.

The sample support 5 on which the sample 1 is placed is a base 6
An XY stage 6 provided so as to be movable in the xy directions with respect to A, and a rotary stage 7 rotatably attached to the XY stage 6 with the center of the XY stage 6 as a rotation axis.
And three sample support members 8 projectingly provided on the rotary stage 7 and mounted slidably in the Z direction. The movement of the XY stage 6 and the rotation of the rotary stage 7 are controlled by the stage control circuit 10. Controlled.

A television camera 11 provided close to the sample loader 2 photographs the sample 1 conveyed by the sample loader 2 from above. The television camera 11 is a field frame 1 shown in FIG.
1A, the X axis of the coordinates (X, Y) in the field frame 11A is provided in parallel with the x axis, and the Y axis is provided in parallel with the y axis.
The image in the visual field frame 11A is converted into a digital signal by the A / D converter 12 and taken into the frame memory 13. The information in the frame memory 13 is output to the CPU 14, and the CPU
14 controls the loader control circuit 4 and the stage control circuit 10 based on this information.

The procedure for transporting the sample 1 to the sample support 5 using the pre-alignment apparatus of this embodiment will be described below. First, as shown in FIG.
The arm 2A of the sample loader 2 on which is mounted is driven from the state of FIG. 1 to stop the stage 2C. The direction and length of the arm 2A when the stage 2C is stopped are the first direction and the first length that are determined in advance. At this time, the outer periphery of the sample 1 is projected in the frame 11A of the television camera 11, and the image is captured in the frame memory 13. FIG.
Indicates the luminance signal of the three horizontal scanning lines (Y = Y1, Y2 and Y3) stored in the frame memory 13, and the position where the luminance signal changes is recognized as the outer periphery of the sample 1.
As shown in FIG. 4, three points (X,
Y) = (X1, Y1), (X2, Y2), (X3, Y
Since 3) is on the outer circumference of the sample 1, the center coordinates (X, Y) = (X0, Y0) of the sample 1 with respect to the frame memory coordinate system can be obtained by the equation of the circle. Assuming that the center coordinates of the sample loader 2 with respect to the frame memory coordinate system of the stage 2C are (X, Y) = (XS, YS), the position between the center of the sample 1 on the sample loader 2 and the center of the stage 2C. The deviation (δX, δY) is calculated by δX = (XS−X0) × K δY = (YS−X0) × K (where K is the actual size per pixel of the frame memory).

Next, the arm 2A of the sample loader 2 is driven again, and the arm 2A is stopped in the direction in which the pattern 1A on the sample enters the field frame 11A as shown in FIG. The direction and the length of the arm 2A at this time are the predetermined second direction and the second length. In this state, the pattern 1A is photographed by the camera 11, and its image is recorded in the frame memory 1
Incorporated in 3. FIG. 6 shows the luminance signals of the two horizontal scanning lines (Y = Y4 and Y5) of the television camera 11, and the position where the luminance signal changes is recognized as the edge of the pattern 1A. As shown in FIG. 6, (X4, Y4), (X5,
Since Y5) is on the same straight edge, the inclination θ0 between one side 16 of the pattern 1A and the Y axis on the screen of the television camera 11 is θ0 = tan ⁻¹ ((X5-X4) / (Y5-Y4)). When the normal angle of the pattern 1A on the screen is θS, the shift angle δθ of the sample 1 with respect to the sample loader 2 is calculated by δθ = θS−θ0. Here, as shown in FIG.
In this state, the angle formed by the straight line 15 connecting the rotation axis of the arm 2A and the center of the stage 2C and the Y axis (y axis) is defined as the normal angle θS.

Next, the arm 2A of the sample loader 2 is rotated clockwise from FIG. 7A so that the center of the stage 2C is at a predetermined position (x, y) = (LX, LY). The arm 2A is extended to attach the sample 1 to the sample support member 8
And the arm 2A is stopped. At this time, the angle formed by the y-axis and the straight line connecting the rotation axis of the arm 2A and the center of the stage 2C is set to Lθ.

Next, the XY stage 6 is driven to stop the XY stage 6 at the position where the coordinates of the center of the XY stage 6 are (x, y) = (LX-δX, LY-δY).

Next, the rotary stage 7 is driven to rotate, and the rotary stage 7 is stopped at an angle of the sample support member 8 such that θ = Lθ−δθ. Here, the angle of the sample support member 8 is 3 as shown in FIG.
An angle formed by a vertical line 18 drawn from a predetermined one vertex 17 of a triangle having the two sample support members 8 as its vertex to the opposite side and the y-axis.

Next, the sample support member 8 is projected in the -Z direction to receive the sample 1 from the stage 2. X as above
Since the Y stage 6 is on standby at the position where the positional deviation (δX, δY) of the sample 1 is absorbed, the center of the mounted sample 1 is the center of the XY stage 6 (the rotation axis of the rotation stage 7). Matches Further, since the rotation stage 7 stands by at an angle that absorbs the displacement angle δθ of the sample 1, the direction of the mounted sample 1 (direction of the side 16 of the pattern 1A) and the direction of the sample support member 8 (perpendicular line). 18)). The sample 1 thus placed on the sample support member 8 is
The Y stage 6 and the rotating stage 7 are driven to convey them to a predetermined position and angle.
The coordinate measurement of A and the like are performed.

In the pre-alignment apparatus of this embodiment, the standby position and standby angle of the sample support member 8 are corrected so as to cancel out the positional deviation and the angular deviation between the center of the stage 2C and the center of the sample 1. Therefore, the mounting position and the mounting angle of the sample 1 with respect to the sample supporting member 8 are adjusted to the regular position and angle, respectively.

When the prealignment apparatus of this embodiment is used, the positional relationship between the sample support member 8 and the sample 1 is made constant, so that the deflection of the sample 1 becomes constant, and as a post-process, for example, on the sample support base 5. The measurement accuracy is improved when the coordinates of the pattern 1A are measured. Further, since the relative angle between the pattern 1A and the sample support member 8 becomes constant,
For example, the measurement point of the coordinate measurement of the pattern 1A of each sample is almost a fixed position with respect to the coordinate of the measuring machine, and the measurement accuracy is improved.

In the present embodiment, one TV camera photographs both the outer periphery of the sample and the pattern edge. However, even if two TV cameras are prepared and each is photographed by another camera. Good. A laser beam may be used to detect the outer circumference of the sample and the pattern edge. For example, the same purpose can be achieved by operating a laser beam on the sample and detecting scattered light with a detector.

Regarding the description of the embodiments and claims,
The sample support base 5 is the sample base, the stage 2C is the carrier, and X
The center of the Y stage 6 is the sample stage reference point, the direction of the perpendicular 18 is the sample stage direction, the center of the sample 1 is the sample reference point, the direction of one side 16 of the pattern 1A is the sample 1 direction, and the stage 2
The center of C is the carrier reference point, the direction of the straight line 15 is the carrier direction, the coordinates (LX, LY) are the standby reference points, and the direction between the direction of the perpendicular 18 and the y axis is Lθ. "Standard waiting direction".

[0022]

According to the present invention, the positional deviation and the deviation angle between the sample and the carrier are obtained from the outer shape of the sample, and the positional deviation is absorbed by correcting the standby position of the sample table. Therefore, the positional relationship between the sample and the sample table is kept constant. Further, since the deviation angle between the sample and the carrier is found from the pattern of the sample and the waiting angle of the sample stand is corrected to absorb the deviation angle, even if the sample has a circular outer peripheral shape, Is placed on the sample table at a regular angle. Therefore, when measuring the coordinates of the pattern, the deflection of the sample placed on the sample table becomes constant and the measurement points of the pattern become substantially constant, which improves the measurement accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a pre-alignment apparatus according to the present invention.

FIG. 2 is a side view showing a sample loader and a sample table of the apparatus shown in FIG.

FIG. 3 is a view showing a state where the stage of the sample loader is at a first predetermined position and a first predetermined angle.

FIG. 4 is a diagram showing an image of the television camera in the state of FIG.

FIG. 5 is a view showing a state in which the stage of the sample loader is at a second predetermined position and a second predetermined angle.

6 is a diagram showing an image of the television camera in the state of FIG.

7A and 7B show directions of a sample, a stage of a sample loader, and a sample support member during pre-alignment, FIG. 7A is a diagram showing a relationship between an angle of the sample and an angle of the sample loader, and FIG. 7B is a standby state of the sample support member. The figure which shows an angle.

FIG. 8 is a diagram showing a state where a conventional pre-alignment method is applied to a rectangular sample.

FIG. 9 is a diagram showing a state of a circular sample and a pattern on the sample.

FIG. 10 is a diagram showing a state in which a conventional pre-alignment method of detecting the outer circumference of a sample and performing pre-alignment is applied to a circular sample.

FIG. 11 is a view showing a state in which a conventional pre-alignment method of detecting a pattern on a sample and performing pre-alignment is applied to a circular sample.

[Explanation of symbols]

 1 sample 1A pattern 2 sample loader 2C stage 5 sample support 11 TV camera 12 A / D converter 13 frame memory 14 CPU

Claims (2)

[Claims] 1. A sample on the sample table so that a sample table reference point provided on the sample table and a sample table reference point provided on the sample are matched, and the sample table direction of the sample table and the sample direction of the sample are matched. In the pre-alignment method of delivering the sample, the sample is placed on the carrier, and the positional deviation between the carrier reference point provided on the carrier and the sample reference point is measured based on the outer peripheral shape of the sample. Along with, the displacement angle between the transporter direction of the transporter and the sample direction is measured based on the pattern on the sample, and only the position shift amount from the standby reference point serving as a reference of the standby position of the sample table is measured. The sample table reference point is aligned with the corrected correction point, and the sample table is aligned with the sample table direction in the correction direction corrected by the deviation angle from the standby direction that is the reference of the standby direction of the sample table. Let it wait, A pre-alignment method, characterized in that the transporter reference point is aligned with the standby reference point, and the sample is transferred from the transporter to the sample stage while the transporter direction is aligned with the standby direction. 2. The sample from the carrier so that the sample table reference point provided on the sample table and the sample table reference point provided on the sample are aligned, and the sample platform direction of the sample platform and the sample direction of the sample are aligned. In a pre-alignment device for delivering a sample to a table, a carrier for transferring the sample to the sample table, and a positional deviation between a carrier reference point provided on the carrier and the sample reference point are measured on the outer circumference of the sample. Measuring means based on the shape and measuring the deviation angle between the carrier direction of the carrier and the sample direction based on the pattern on the sample, and a reference for the standby position of the sample table. The sample table reference point is aligned with the correction point that is corrected by the positional deviation from the standby reference point, and the sample table direction is corrected from the standby direction, which is the reference in the standby direction of the sample table, by the correction angle. And further, the carrier and the carrier so that the sample is transferred from the carrier to the sample stage in a state where the carrier reference point is the standby reference point and the carrier direction is aligned with the standby direction. A pre-alignment apparatus comprising: a control unit that controls the sample stage.