JPS59933A - Method for inspection of aluminum pattern on semiconductor wafer - Google Patents

Abstract

PURPOSE:To enable to perform an automatic discriminating inspection in an accurate and efficient manner by a method wherein the prescribed signal for each element to be inspected is obtained from the logical product image for binary and its inverted image relating to a wafer and an Al mask pattern. CONSTITUTION:A protruded part 7, a short-circuit part 9, a concaved part 6 and a discontinuous part 8, all of which are elements to be inspected, are picked out by finding the logical product images differing each other for the monotone image and the inverted monotone image of the semiconductor wafer 11 and the Al mask pattern 12. The transmission of the position, type and the like of respective element to be inspected are automatically discriminated by the signal obtained respectively from both image processing circuits 21 located on the two logistical product images.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for inspecting aluminum patterns during the manufacturing process of semiconductor chips.

In the manufacture of integrated circuit devices (ICs), a semiconductor wafer is produced by repeating etching and diffusion processes, and in order to electrically connect each element within the device, a full minilumn is deposited on the surface of the semiconductor wafer. After that, there is a step of etching into a predetermined pattern to obtain the desired aluminum pattern.

FIG. 1 is an enlarged image of the surface of the semiconductor square after the aluminum pattern has been formed. In this figure, the horizontally lined area 1 is the substrate of the semiconductor wafer, the diagonally lined area 2 is the semiconductor part where impurity atoms have been diffused, the white part 3 with black dots 4 is the evaporated aluminum part, and 5 is the etched evaporated aluminum part. 6 is a concave portion of the vapor-deposited aluminum portion 3, T is a protrusion of the vapor-deposited aluminum portion 3, and 8 is a discontinuous portion of the vapor-deposited aluminum portion 3. , 9 is the vapor-deposited aluminum part 3
Each of the detected elements of the so-called intended aluminum pattern, such as a short-circuit part, is shown.

Figure 2 shows a black and white image (binarized image) of the aluminum mask pattern 12 used during the inspection process.
Reference numeral 10 denotes a full minilumn pattern portion of this aluminum mask pattern 12.

In the above figure, the vapor-deposited aluminum part 3 is
It has a high reflectance and is observed to be the brightest, but the light is diffusely reflected due to the minute irregularities on the vapor deposition surface, and dark spots 4 appear here and there.

On the other hand, the substrate 1 and semiconductor part 2 of the semiconductor wafer are
Since the reflectance is lower than that of the aluminum surface, it appears slightly darker.

Further, in the stepped portion 5, light is scattered and appears in the shape of a black line.

According to the present invention, the recesses 6 . Projection 7
．． Discontinuity 8. This is to check whether there are any defects in each element to be detected, such as the short-circuit portion 9.

Conventionally, the presence or absence of defects in each element to be detected has been magnified using a magnifying device and then visually observed by an operator. This results in poor work efficiency and heavy worker fatigue, and therefore automation has been desired.

This invention was developed to meet these demands. The inspection method of the present invention will be explained below.

First, from the surface image of the semiconductor wafer shown in FIG. 1, in order to automatically determine the defective location of the aluminum pattern by computer, K is first shown in FIG. It is necessary to obtain a black and white image using infrared reflected illumination.Due to the difference in infrared reflectance between the vapor-deposited aluminum part 3, the substrate 1, and the semiconductor part 2, part of the semiconductor part 2 and the stepped part 5 are erased in this process. Only the binarized black and white image of the vapor-deposited aluminum portion 3 is taken out.

However, this image has the disadvantage that, as shown in the figure, a part of the black line-shaped stepped portion 5 and the black dots 4 still remain on the vapor-deposited aluminum portion 3, and these interfere with the final judgment. There is.

On the other hand, by utilizing the property of the semiconductor wafer to transmit infrared rays, infrared rays were irradiated from the surface having the vapor-deposited aluminum portion 3 and the opposite surface to the area 5 shown in FIG. A step is required to obtain the black-and-white image shown in FIG. 4, which is a binarized image of an infrared transmission image using infrared rays. Through this step, the vapor-deposited aluminum part reflects or absorbs infrared rays, so it appears dark as shown in the figure, and on the other hand, the substrate 1 and the semiconductor portion 2 are bright because they transmit infrared rays. Through this step, the vapor-deposited aluminum portion 3 can be separated from the substrate 1 and the semiconductor portion 2 as shown in FIG.

However, in this state, the transmitted infrared rays are refracted at the stepped portion 5, so this portion appears as a black line as shown in the figure.
Similarly, this has the disadvantage of interfering with the final determination.

Therefore, the present invention is designed to further eliminate the above-mentioned drawbacks that appear in the two images shown in FIGS. 3 and 4. This invention will be explained below.

That is, in the inspection process diagram of FIG. 5, 11 is a semiconductor wafer to be inspected, 12 is an aluminum mask pattern, 13 is an infrared illumination device that illuminates the semiconductor wafer 11, and 14 is a visible light beam that illuminates the aluminum mask pattern 12. a lighting device, 15 the semiconductor wafer 11;
and a magnifying lens provided on the back side of the aluminum mask pattern 12; 16 is a half mirror for illuminating infrared rays reflected from the back side of the semiconductor wafer 11; an infrared TV camera 18 for imaging the aluminum mask pattern 12; a visible light TV left camera 19 for imaging the aluminum mask pattern 12; 20 a shutter for transmitting or reflecting the irradiated infrared;
An image processing circuit 22 captures the video signals of the semiconductor wafer 11 and the aluminum mask pattern 12 obtained from the V-camera 17 and 18 into an image memory, performs necessary processing, and obtains respective predetermined signals; 22 is the obtained signal; This is a computer for determining the suitability of the position and type of each element to be detected, and for performing predetermined control of each of the shutters 19, 20, etc.

Next, the operation will be explained.

First, the aluminum mask pattern 12 and the semiconductor wafer 11 are installed at positions corresponding to the respective TV cameras 17 and 18. First, the shutter 19 is opened, the shutter 20 is closed, and the image by the reflected infrared illumination is captured by the infrared rays.
By capturing an image with the V left camera 7 and binarizing this video signal, a black and white image of the infrared reflected illumination image shown in FIG. 3 is obtained. On the other hand, from visible light TV left camera B, the second
By inputting the image of the aluminum mask pattern 12 shown in the figure and further reversing the black and white of this image, the inverted black and white image shown in FIG. 6 is obtained.

By taking the logical product of the thus obtained infrared reflected illumination image of the semiconductor Ueno 11 shown in FIG. 3 and the inverted monochrome image of the aluminum mask pattern 12 shown in FIG. 6, the logical product shown in FIG. From the image, the protrusion T and the short circuit 9, which are the elements to be detected, are taken out.

Next, open the shutter 20 in FIG.
9 is closed and an image obtained by infrared transmitted illumination is captured by the infrared TV left camera T, and this video signal is binarized to obtain a black and white image of the infrared transmitted illumination image shown in FIG.

On the other hand, from the other visible light TV left camera 8, an image of the aluminum mask pattern 12 shown in FIG. 2 is obtained.

The infrared transmitted image of the semiconductor wafer 11 obtained in step 5 and the aluminum mask pattern 1 of FIG.
By performing a logical product with the black and white image of 2, the concave portion 6 and the discontinuous portion 8, which are the detected elements left by the logical product image of FIG. 8, are extracted.

Thereafter, the computer 22 is used to automatically determine the position and type of each detected element based on the respective signals obtained by both image processing circuits 21 in these two-wheel embedded images.

Since the inspection method of the present invention is performed in the manner described above, it has the advantage of eliminating the conventional visual inspection, which is accompanied by fatigue, and enabling accurate and efficient automatic discrimination inspection.

[Brief explanation of the drawing]

Figure 1 shows the semiconductor wafer after aluminum pattern generation.
Figure 2 is a black and white image of an aluminum mask pattern, Figure 3 is a black and white image of an infrared reflection illumination image of a semiconductor wafer, and Figure 4 is a black and white image of an infrared light transmission of a semiconductor wafer. Figure 5 is a diagram showing a black and white image of an illumination image, Figure 5 is an inspection process diagram showing one embodiment of the present invention, Figure 6 is a diagram showing a reverse image of a black and white image of an aluminum mask pattern, Figure 7 is Figure 3. FIG. 8 is a diagram showing a logical product image of the black-and-white image of FIG. 4 and the black-and-white image of FIG. 2. In the figure, 6 is a concave portion, T is a protrusion, 8 is a discontinuous portion, 9 is a short circuit portion, 11 is a semiconductor wafer 1, 12 is an aluminum mask pattern, 21 is an image processing circuit, and 22 is a computer. Note that the same reference numerals in the figures indicate the same or similar parts. Agent Nobu Kuzuno - (1 other person) Figure 1 Figure 5 Figure 6 Mr. Commissioner of the Japan Patent Office 1, Indication of the case Patent Application No. 110108-1988 2
, Title of the invention Aluminum pattern inspection method for semiconductor sea urchin/\ 3, Person making the amendment 5, Detailed explanation of the invention column 6 of the specification subject to amendment, Contents of the amendment ``Transmission'' on page 8, line 16 of the specification be corrected to "appropriate". that's all

Claims (1)

[Claims] A step of obtaining a black and white image of an infrared reflected illumination image of the semiconductor sea urchin and a step of obtaining an inverted image of a black and white image of a predetermined aluminum mask pattern, and a step of obtaining a logical product image of both the steps, and a step of obtaining a logical product image of both the steps, and a step of obtaining a black and white image of the black and white image of the predetermined aluminum mask pattern. A step of obtaining an image, an infrared transmission illumination image of the semiconductor sea urchin, a step of obtaining a black and white image, a step of obtaining an AND image of both from which two steps, an image of obtaining a predetermined signal of each element to be detected in both of these AND images. A method for inspecting aluminum patterns on semiconductor sea urchins, comprising a processing step and a calculation step for determining suitability of the position and type of each detected element from each detection signal obtained in this step.