JPH06151564A - Wafer pattern device - Google Patents

Abstract

PURPOSE:To prevent the miss of a view when a wafer shifts to the next alignment pattern by detecting the angle of rotation, using the first alignment pattern, and shifting the wafer to the second pattern, based on this data, so as to perform alignment, and further, performing the final alignment at the third pattern. CONSTITUTION:A sample stage 4 is shifted to a first alignment pattern 7, and it is displayed on a CRT 5, and a reference point is determined thereon, and it is set on the center position of the cross cursor 12 on the CRT 5. The inclination of the cross cursor 12 corresponding to the shifting direction of a wafer to the alignment pattern is sought, and it is shifted to the second alignment pattern, with the relative position where the inclination theta is taken into consideration. The inclinations of the first, second, and third alignment patterns are sought, and those are used for the compensation of the shifting of the sample stage 4 in measurement of the pattern on a sample 3. Since the inclination is sought on the first alignment pattern, even if the second alignment pattern is set on a relatively distant position, it can be detected without going wide of the view.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection apparatus for measuring the dimensions of a pattern formed on a wafer.

[0002]

2. Description of the Related Art In order to measure a target pattern on a sample in a wafer pattern length measuring apparatus, an error in the horizontal direction and the rotation direction between the pattern on the sample and the moving direction of the sample table is obtained in advance, and the error of the sample table is measured. When moving, it is necessary to make a correction in consideration of the angle. This sample moving method is described in JP-A-62-122226.

Conventionally, in such an error correction, an alignment pattern is usually set at two positions as far as possible from each other on a wafer. Next, the sample stage is moved so that the first alignment pattern is within the field of view, the center position of the alignment pattern is obtained, and at that time, the error in the horizontal direction and the rotation direction between the first alignment pattern and the sample stage is obtained. . Next, the position of the second alignment pattern was moved to the position of the second alignment pattern at a known value of the relative position in consideration of the error angle, and the center of the second alignment pattern was obtained again here. However, in this method, the positional accuracy is poor, and the more the two alignment pattern positions are apart, the larger the deviation becomes. In an apparatus that cannot obtain a large field of view, there is a problem that the alignment pattern may go out of the field of view.

[0004]

In an apparatus that cannot take a large field of view when moving to the second alignment pattern, the alignment pattern may go out of the field of view. In that case, the surrounding area may be manually operated. There was a problem that I had to search for it. Further, in this case, the alignment accuracy is poor.

It is an object of the present invention to prevent the field of view from falling out when moving to the next alignment pattern position and to improve the alignment accuracy.

[0006]

In order to achieve the above object, the present invention uses the following means.

1. Use another alignment pattern near the first alignment pattern and move there to the second alignment pattern.
Is performed, the rotation angle is detected at this angle, and the final alignment operation is performed on the third alignment pattern at the distant position based on this data.

2. The rotation angle is detected using the first alignment pattern, the alignment pattern is moved to the second pattern based on this data, alignment is performed, and the final alignment operation is performed on the third pattern located further away.

3. The same pattern of different dies is used for the first, second, and third alignments to solve the problems.
The alignment operation is performed using the means described in.

As described above, the feature is that the alignment operation is performed three times by using the patterns at three locations.

[0011]

According to the above method, 1. Usually, the alignment operation is performed twice, so that the pattern is less likely to be out of the field of view when moved to a distant pattern, and the alignment is facilitated. Also, the accuracy is improved.

2. In addition to the action described in action 1, since the rough inclination is detected in the first alignment and the next alignment position is moved based on it, it can be detected even if the second alignment pattern is set to a distant position. It is also possible to increase the accuracy of movement to the third alignment pattern.

3. In addition to the actions described in action 1, each 3
Since the same pattern of different dies is used for one-time alignment, it is not necessary to create a special pattern.

[0014]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 is a schematic configuration diagram of a wafer pattern length measuring apparatus embodying the present invention. In FIG. 1, 1 is an electron optical system, 2 is a sample chamber, 3 is a wafer which is a sample, 4 is a sample stage which is movable in X and Y directions, 5 is a CRT which displays an image on the wafer, and 6 is on the sample. It is a computer that confirms the image position, calculates the sample movement amount, and displays the cross cursor. The pattern image on the wafer mounted on the sample table 4 is displayed on the CRT 5.

FIG. 2 is a plan view of the sample 3 and the sample table 4
Shows the coordinate system of. Alignment patterns 7, 8 and 9 were set on the sample 3 at three positions apart from each other.

FIG. 3 shows enlarged images 10 and 11 of the alignment pattern displayed on the CRT 5. A cross cursor 12 is displayed on the CRT 5, which coincides with the horizontal direction of the coordinate system of the sample table 4.

An embodiment of claim 1 having the above structure will be described.

First, the sample table 4 is moved to the first alignment pattern 7 and displayed on the CRT 5. First displayed
Establish a reference point on the alignment pattern 10 and
The center position of the upper cross cursor 12 is set. Next, the sample stage 4 is moved from the alignment patterns 7 to 8 at a known relative position value, and the second alignment pattern 8 is moved to the CRT.
5 is displayed. C of this second alignment pattern
Moving distance Δ in the Y direction between the reference point of the RT image 11 and the reference point of the first alignment pattern enlarged view 10 obtained above
The shift amounts ΔX in the Y and X directions are sent to the computer 6, and the inclination θ of the CRT images 10 and 11 of the first and second alignment patterns is calculated by the computer 6 by the calculation formula tan θ = ΔX / ΔY. .

In consideration of the inclination θ obtained by the above equation, the sample stage 4 is further moved to the third alignment pattern 9, and C of the second and third alignment patterns is set in the same manner as above.
The inclination θ of the RT images 11 and 12 is obtained. The more accurate inclination thus obtained is used for correcting the movement of the sample table in the pattern measurement on the sample 3.

As described above, according to the present invention, it is possible to reduce the deviation of the alignment pattern by increasing the number of the alignment patterns from the conventional two to three and shortening the moving distance between the alignment patterns. Improved accuracy. Here, a case where the alignment pattern is set to two places as in the conventional case will be described as an example.

It is assumed that the inclination θ between the sample table 4 and the sample 3 is obtained using the first alignment pattern 7 and the third alignment pattern 9. FIG. 4 is an enlarged image of the first and third alignment patterns on the CRT 5 from the left. First, it is assumed that the coordinate A of the first alignment pattern position is adjusted to (0, 0) and the position is moved to the third alignment pattern position at a known relative position. The larger the moving distance is, the larger the deviation amount ΔL becomes. Therefore, when the field of view of the CRT 5 is small, the alignment pattern may be out of the field of view as shown in FIG. 4, resulting in poor operability and accuracy. become worse.

Next, an embodiment of claim 2 will be described.

First, the sample table 4 is moved to the first alignment pattern 7 and displayed on the CRT 5. First displayed
Establish a reference point on the alignment pattern 10 and
The center position of the upper cross cursor 12 is set. Here, the inclination θ of the cross cursor corresponding to the alignment pattern and the wafer moving direction was obtained, and the cross cursor was moved to the second alignment pattern at a relative position in consideration of the inclination θ. After that, the first and second, second and third
The inclination of the alignment pattern was obtained and used to correct the movement of the sample table in the pattern measurement on the sample 3. The advantage of this method is that since the tilt is obtained on the first alignment pattern, even if the second alignment pattern is set at a relatively distant position, it can be detected without being out of the field of view, and the accuracy of the movement of the third alignment pattern can be improved. It is also possible to raise.

Next, an embodiment of claim 3 will be described.

The method is the same as in the first and second embodiments, but the first, second and third alignment patterns are replaced by the same pattern written in different dies. The advantage of this method is that no special patterns have to be created. In the embodiment, a CRT
Although the cross cursor is used for designating or instructing the position of interest on the screen, it is not necessary to limit to the cross cursor, and the same effect can be obtained by using another method such as a mouse.

In the embodiment, the sample stage was moved along the Y direction, but when moving in the X direction, the calculation formula tan θ
The same effect can be obtained by calculating the inclination θ by the formula: = ΔY / ΔX.

[0028]

EFFECTS OF THE INVENTION According to the present invention, in the wafer pattern length measuring device which cannot obtain a large field of view, the distance between the alignment patterns can be shortened by installing the alignment patterns, which were conventionally two places, at three places. The alignment pattern can be easily detected. Further, the accuracy is improved by performing the alignment operation three times.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an inspection apparatus for measuring dimensions of a wafer pattern according to the present invention.

FIG. 2 is a view showing a coordinate system of a sample wafer and a sample stage.

FIG. 3 is a diagram showing enlarged images of first and second alignment patterns displayed on a CRT and inclinations of both alignment patterns.

FIG. 4 is a diagram in which an alignment pattern is out of the visual field when an example is performed by a conventional method.

[Explanation of symbols]

1 ... Electro-optical system, 2 ... Sample chamber, 3 ... Sample, 4 ... Sample stand,
5 ... Image display CRT, 6 ... Computer, 7, 8, 9 ...
Alignment pattern 10, 11, A, C ... Alignment pattern enlarged image, 12, B ... Cross cursor.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location H01L 21/027 21/66 J 7377-4M (72) Inventor Hiroyoshi Mori 882 Ichige, Katsuta, Ibaraki Prefecture Address Hitachi, Ltd. Measuring Instruments Division

Claims (3)

[Claims] 1. An optical or electron beam apparatus for inspecting a pattern formed on a wafer, comprising: mechanical coordinates of a wafer moving table; and coordinates of a pattern on the wafer mounted on the wafer moving table. An image of a pattern on a wafer in a system in which multiple position images formed at specific positions on the wafer are used to associate and move to the target inspection pattern based on the coordinate values of the pattern on the wafer. Means for displaying on the display screen, means for designating an arbitrary position in the image displayed on the display screen, and a difference between a predetermined position on the display screen and the designated position on a horizontal plane. And means for detecting the tilt angle of the stage on which the wafer is placed, and X or Y
At least one of the moving mechanisms is mounted on the tilting mechanism, and the apparatus has a stage whose moving direction moves along the tilting direction, and uses a first alignment pattern for wafer alignment to coordinate a reference point. The second alignment pattern near the first alignment pattern is used to detect the inclination of the pattern on the wafer with respect to the stage movement with respect to the horizontal direction, and based on the inclination, the movable table is moved to the third alignment pattern position. A wafer pattern device characterized by being moved. 2. The wafer pattern device according to claim 1, wherein the first alignment pattern is used for wafer alignment, a general inclination is detected, and the wafer is moved to a second alignment pattern. 3. The wafer pattern device according to claim 1, wherein the same pattern is used for different dies for the first, second, and third alignments for the wafer alignment.