JPS6348425B2 - - Google Patents

Description

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

In the manufacture of integrated circuit devices (ICs), aluminum is deposited on the surface of the semiconductor wafer to electrically connect each element within the device to a semiconductor wafer that is produced by repeating etching and diffusion steps. There is a step of obtaining the desired aluminum pattern by etching into a predetermined pattern.

FIG. 1 is an enlarged image of the semiconductor wafer surface after the aluminum pattern is formed. In this diagram,
The horizontally lined area 1 is the substrate of a semiconductor wafer, the diagonally lined area 2 is the semiconductor part treated with diffusion of impurity atoms, the white part 3 with black dots 4 is the evaporated aluminum part, and 5 is the layer formed by repeated etching and vapor deposition. step portions of each layer on the surface of the semiconductor wafer formed in 6
7 is a concave portion of the vapor deposited aluminum portion 3, 7 is a protrusion of the vapor deposited aluminum portion 3, 8 is a discontinuous portion of the vapor deposited aluminum portion 3, and 9 is a short circuit portion of the vapor deposited aluminum portion 3. Each detected element of the aluminum pattern is shown.

FIG. 2 shows a black and white image (binarized image) of the aluminum mask pattern 12 used during the inspection process, and 10 is the aluminum pattern portion of this aluminum mask pattern 12.

In the one shown in FIG. 1 above, the vapor-deposited aluminum part 3 has a high reflectance and is observed as the brightest, but
Light is diffusely reflected due to the fine irregularities on the vapor deposition surface, and black specks 4 appear here and there. On the other hand, since the substrate 1 and the semiconductor portion 2 of the semiconductor wafer have a lower reflectance than the aluminum surface, they appear somewhat darker. Further, in the stepped portion 5, light is scattered and appears in the shape of a black line.

This invention examines whether there are any defects in the detected elements such as the concave portion 6, the protrusion 7, the discontinuous portion 8, the short circuit portion 9, etc. in the vapor-deposited aluminum portion 3 after the formation of the semiconductor wafer surface that appears in the above state. This is to inspect.

Conventionally, the presence or absence of a defect 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, in order to automatically determine the defective location of the aluminum pattern using a computer from the surface image of the semiconductor wafer shown in FIG. 1, first, the image shown in FIG. It is necessary to obtain a black and white image using infrared reflected illumination.
Due to this step, due to the difference in infrared reflectance between the vapor-deposited aluminum part 3 and the substrate 1 and semiconductor part 2,
Only a monochrome image of the vapor-deposited aluminum part 3 in which the semiconductor part 2 and a part of the stepped part 5 are erased and binarized 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 a semiconductor wafer to transmit infrared rays, a surface having a vapor-deposited aluminum portion 3;
It is necessary to irradiate infrared rays from the opposite side as shown in FIG. 5 described later, and to obtain a black and white image of FIG. 4, which is a binarized infrared transmitted image of the infrared rays transmitted through this semiconductor wafer 11. Through this process, the vapor-deposited aluminum part reflects or absorbs infrared rays, so it appears dark as shown in the figure, whereas the substrate 1 and semiconductor part 2 transmit infrared rays, so they appear bright. It can be separated from the semiconductor portion 2 as shown in FIG.

However, in this state, since the transmitted infrared rays are refracted at the stepped portion 5, this portion appears as a black line as shown in the figure, which also has the drawback 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.
12 is an aluminum mask pattern; 13 is the semiconductor wafer 11 to be inspected;
14 is a visible light illumination device that illuminates the aluminum mask pattern 12; 15 is a magnifying lens provided on the back of the semiconductor wafer 11 and the aluminum mask pattern 12; 16 is an infrared light that illuminates the aluminum mask pattern 12; Half mirror for reflective illumination of infrared rays, 1
Reference numeral 7 denotes an infrared TV camera for imaging each surface by reflected and transmitted infrared illumination from the semiconductor wafer 11, 18 a visible light TV camera for imaging the aluminum mask pattern 12, and 19 and 20 for transmitting or transmitting infrared irradiation. A shutter 21 for obtaining reflected light captures the video signals of the semiconductor wafer 11 and the aluminum mask pattern 12 obtained from the respective TV cameras 17 and 18 into an image memory, and performs necessary processing to obtain respective predetermined signals. An image processing circuit 22 for determining the suitability of the position and type of each detected element from the obtained signal, and also
This is a computer for performing predetermined control such as.

Next, the operation will be explained.

First, the aluminum mask pattern 12 and the semiconductor wafer 11 are attached to each TV camera 17,
Installed in 18 corresponding positions. First, the shutter 19 is opened, the shutter 20 is closed, an image of reflected infrared illumination is captured by the infrared TV camera 17, and this video signal is binarized.
A black and white image of the infrared reflected illumination image shown in FIG. 3 is obtained. On the other hand, from the visible light TV camera 18, 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 wafer 11 shown in FIG. 3 and the inverted monochrome image of the aluminum mask pattern 12 shown in FIG. 6, the logical product image shown in FIG. The protrusion 7 and the short circuit 9, which are the elements to be detected, are taken out.

Next, the shutter 20 shown in FIG. 5 is opened, the shutter 19 is closed, an image by infrared transmitted illumination is captured by the infrared TV camera 17, and this video signal is binarized, as shown in FIG. Obtain a black and white image of the infrared transillumination image shown.

On the other hand, from the other visible light TV camera 18,
The aluminum mask pattern 1 shown in FIG.
Obtain the second image.

The above semiconductor wafer 1 thus obtained
By taking the logical product of the infrared transmitted image of 1 and the black and white image of the aluminum mask pattern 12 of FIG. Take out section 8. After that, the computer 22 is used to automatically determine whether or not the position and type of each detected element are appropriate based on the respective signals obtained by both image processing circuits 21 in these AND 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]

FIG. 1 is a diagram showing a surface image of a semiconductor wafer after aluminum pattern generation, FIG. 2 is a diagram showing a black-and-white image of an aluminum mask pattern, and FIG. 3 is a diagram showing a black-and-white image of an infrared reflective illumination image of a semiconductor wafer. FIG. 4 is a diagram showing a black and white image of an infrared transmitted illumination image of a semiconductor wafer, FIG. 5 is an inspection process diagram showing an embodiment of the present invention, and FIG. 6 is a diagram showing an inverted image of the black and white image of an aluminum mask pattern. ,
Figure 7 is a diagram showing a logical product image of the black and white image in Figure 3 and the black and white image in Figure 6, and Figure 8 is a diagram showing a logical product image of the black and white image in Figure 4 and the black and white image in Figure 2. be. In the figure, 6 is a concave portion, 7 is a protrusion, 8 is a discontinuous portion, 9 is a short circuit portion, 11 is a semiconductor wafer, 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 corresponding parts.

Claims (1)

[Claims] 1 Obtaining a logical product image of both of the steps of obtaining a black and white image of an infrared reflected illumination image of a semiconductor wafer and a step of obtaining a reverse image of a black and white image of a predetermined aluminum mask pattern, as well as a step of obtaining a black and white image of the aluminum mask pattern. A step of obtaining an AND image of both of the steps of obtaining an image and a step of obtaining a monochrome image of an infrared transmitted illumination image of the semiconductor wafer, and an image of obtaining a predetermined signal of each detected element in both of these AND images. A method for inspecting aluminum patterns on semiconductor wafers, comprising a processing step and a calculation step for determining suitability of the position and type of each element to be detected from each detection signal obtained in this step.