JPS62115737A - Inspection device for external appearance of semiconductor substrate - Google Patents

Abstract

PURPOSE:To discriminate defectives and nondefectives automatically by comparing the quantity of deviation of a post-process to a pre-process and tolerance on a design, to decrease man- hours and to improve the precision of decision by detecting a positioning mark put in the pre-process and a positioning mark put in the post-process by using a sensor and recognizing the quantity of deviation of the post-process to the pre-process on the basis of an output signal from the sensor. CONSTITUTION:A developed wafer 1 is mounted onto a Y stage 9. A positioning X mark 2 in a pre-process at a first measuring point on the wafer 1 is carried just under laser beams 6 for positioning, and positioning operation is conducted. A positioning signal 7 is acquired at that time. X-stage coordinates at a point where the peak value of the positioning signal is formed are represented by (a). An X stage 10 is moved in the direction of the view B, a positioning mark 3 in a post-process is conveyed just under laser beams 6 for positioning, and positioning operation is performed. Coordinates at a point where the peak value of a positioning signal 8 obtained is shaped are represented by (b). The signal is inputted to a processing section 20, and the processing section 20 divides a distance between the positioning marks in the pre-process and the post-process and recognizes the quantity of deviation between the divided distance and a distance (c) on a design.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a visual inspection method used to confirm the appearance, etc. of a semiconductor substrate (hereinafter referred to as a wafer) after photoresist development during a semiconductor manufacturing process. It is related to the device.

[Conventional technology]

Conventionally, this type of equipment only automatically takes the wafer in and out of the cassette, transports it, and positions the wafer.
The quality of the developed pattern was mainly judged by humans through visual inspection using a microscope built into the device.

[Problem that the invention seeks to solve]

In general, there is a probability that the wafer after the photoresist failure will have pattern deviations, sharpness, and other defects that occur during the resist coating process, alignment exposure process, and development process. It is common practice to conduct a visual inspection by sampling all or part of the product.

However, conventional devices rely on the human eye to judge the quality of patterns, which requires a large amount of man-hours.
Furthermore, there were many problems in terms of determination accuracy.

In particular, the allowable range of deviation in the subsequent process from the pattern in the previous process is becoming smaller year by year as the pattern becomes finer), and the current method is to visually read the shibania, which is determined intuitively based on the 9 conditions in which the patterns overlap. I have to say that this has reached its limit.

The present invention provides an appearance inspection device that can mechanize pattern quality determination.

[Failure to solve the problem]

The present invention provides a sensor for detecting an alignment mark placed in at least one arbitrary position in a pre-process and an alignment mark in a post-process placed in a place that is designed to be a certain distance away from the alignment mark; This distance is determined by determining the distance between two alignment marks based on the output signal of the sensor.

A semiconductor substrate appearance inspection apparatus is characterized in that it has a processing section that recognizes the amount of deviation between the distance and the designed distance.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, 10 is an X drive motor 12 and an X.

An X stage 9 is fed in the X direction by a motion axis 11, and a Y stage 9 is fed in the Y direction on the X stage 10 by a Y drive motor 14 and a Y drive shaft 13. A wafer is placed on top.

In this embodiment, the alignment laser beam 6 is focused by a lens 15 and irradiated onto the wafer 1 to perform pre-process alignment
A sensor detects the X marks 2 and 3 and the post-process alignment marks 4 and 5, and the distance between the alignment marks 2 and 3.4 and 5 of 2 is calculated based on the output signal of the sensor. It has a processing unit 20 that recognizes the amount of deviation between the calculated distance and the designed distance C. 16 is an X interferometer laser beam, 17 is an X interferometer mirror, 19 is a Y interferometer radar beam, and 18 is a Y interferometer mirror.

Here, the X-direction deviation will be explained as a representative example.

First, the developed wafer 1 is placed on the Y stage 9 (FIG. 1). Next, the positioning X mark 2 from the previous process at the first measurement point on the wafer 1 is brought directly under the positioning laser beam 6, and a positioning operation is performed (FIGS. 2 and 3). At this time, the positioning signal 7 shown in FIG. 4 is obtained.

The X steno coordinate of the point where the peak value of the positioning signal appears is a
shall be. Furthermore, the X stage 10 is moved in the direction of arrow B to carry the positioning X mark 3 in the subsequent process directly under the positioning laser beam 6 and perform a positioning operation. Let b be the coordinates of the point where the peak value of the obtained positioning signal 8 appears. This signal is input to the processing unit 20, which calculates the distance between the alignment marks in the previous process and the subsequent process, and recognizes the amount of deviation between the calculated distance and the designed distance C.

Pre-process alignment mark 2 and post-process alignment mark 3
are separated by C in design, so the amount of deviation in the subsequent process from the previous process is given by a-b-c.

The deviation in the Y direction can also be measured in the same manner.

Furthermore, the second...nth measurement points on the wafer can be measured in exactly the same manner.

The amount of deviation obtained by the method described above is compared with the allowable design deviation width (denoted as d) stored in advance inside the device, and 1a
-b-CI≦ldl then good, l a-b-e l
>I d l, it is also possible to automatically determine no.

In one embodiment of the present invention, a laser beam fixed stage moving type positioning system is used as a method for measuring the distance between marks, and an X-Y system equipped with a laser interferometer is used to obtain a highly accurate X-Y coordinate thread. Although a stage was used, the shape and method do not matter as long as the method of measuring the pre-process mark and post-process mark with a laser source etc. and recognizing the distance is used, which is a feature of the present invention. It is something.

[Effects of the Invention] As explained above, the present invention uses a sensor to detect the alignment mark entered in the previous process and the alignment mark entered in the post process, and based on the output signal, the alignment mark is detected in the post process relative to the previous process. Since the amount of deviation is recognized, it is possible to automatically make a pass/fail judgment by comparing the amount of deviation with the design tolerance, reducing human labor and improving judgment accuracy. It has the effect of being effective against.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a perspective view showing alignment marks printed on a wafer, FIG. 3 is a sectional view taken along line AA' in FIG. FIG. 4 is a diagram showing the waveform of the positioning signal. 1... Wafer, 2... Front process alignment X mark, 3... Back process alignment X mark, 4... Front process alignment Y mark, 5... Back process alignment Y mark, 6...Laser beam for alignment, 7...Pre-process mark positioning signal, 8...Post-process mark positioning signal, 9...Y stage, 10...X stem, 11
...X drive shaft, 12...X drive motor, 13...
Y drive, driving axis, 14...Y drive motor, 15...Lens, 16...X interferometer laser source, 17...X interferometer mirror, 18...Y interferometer mirror, 19. ...Y interferometer laser light. Figure 2

Claims (1)

[Claims] (1) In a device that inspects the appearance of a post-process with respect to a pre-process after photoresist development on a semiconductor substrate, etc., a design is made from the alignment mark placed at an arbitrary location on the semiconductor substrate in the pre-process and the alignment mark. A sensor detects an alignment mark for post-processing placed at a location a certain distance away from the top, and calculates the distance between the two alignment marks based on the output signal of the sensor. 1. A semiconductor substrate appearance inspection apparatus, comprising: a processing section that recognizes the amount of deviation from the distance.