JPS6181640A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain an image having a constant contrast independently from inclination of a semiconductor pellet, by providing the pellet with a vapor- deposited aliminium surface having a constant diffuse reflection component so as to inhibit any regularly reflected light from entering into a microscope. CONSTITUTION:Aluminium is vapor deposited on a semiconductor pellet under a sufficient residual air pressure (3X10<-6>Torr or higher) to provide the deposited aluminium film with a satin-like surface having a reflection luminance higher than a predetermined value for all the radiation angles. Further, in order to observe the pellet, a tube 5 receiving a light source 3 and a condenser lens 4 therein is provided separately from a microscope lens barrel 1 and an object lens 2 so as to apply light obliquely to a semiconductor pellet 6 which is present within the visual field of the microscope and has the reflectivity of aluminium.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a system for producing semiconductor devices, particularly for improving the efficiency of visual detection or for replacing it with an artificial visual system. This paper relates to a method for producing an aluminum film.

In the production process of semiconductor devices such as transistors and circuit elements, especially in the assembly process after the semi-11T single pellet is completed and cut, inspection and positioning are often performed using an optical pattern on its surface. For example, the arrangement a from a semiconductor electrode to a terminal for external connection.
Gold-rimmed? In the wire bonding process performed by thermocompression bonding, the displacement of the semiconductor pellet on the pedestal is visually detected and the crimp position of the gold wire is adjusted. Is there a defect in the maji bellet? Visual detection is also performed. Since the target semiconductor pellet is a minute object, it is necessary to use a stereoscopic microscope or a metallurgical microscope to enlarge this object section.

Conventionally, visual detection of semiconductor pellets was carried out by the visual sense of the operator, but for example, as disclosed in Japanese Patent Application No. 48-21636 by the present inventor, imaging equipment such as an industrial television camera has been developed. , devices such as light-grain conversion devices that use sound to capture the drift and automatically detect it by processing stones are being developed. Attempts have also been made to reproduce it on maintenance television monitors to make it easier for workers to see.

It is advantageous if the pattern on the semiconductor pellet can be seen with high contrast, both by an operator and by an automatic detection device. What is the detection accuracy of Toguni automatic detection equipment? In order to improve the image quality, it is essential to obtain high contrast. The surface of a typical semiconductor pellet (C1) is formed of silicon oxide, aluminum, and silicon, with the former two occupying a particularly large area. Therefore, it is sufficient to deal with the problem of contrast between the silicon oxide part and the aluminum part.

These may be covered with a protective film made of organic resin or silicon oxide, but since the film is thin, it is safe to assume that as far as light reflection is concerned, the properties of the underlying material appear almost as they are.

The optical reflection properties of a substance are expressed, for example, by a reflection brightness curve as shown in FIG. This curve varies depending on the nature of the surface of the object and the angle of incidence of the light. - In the metallurgical microscope used, vertical epi-illumination as shown in Fig. 2 is performed, so the illumination is applied near the incident angle O0, and the reflected light flux near the reflection angle 0°? I'm getting it. In the graph of FIG. 1, the incident angle of illumination is 0°, the horizontal axis represents the reflection angle, and the vertical axis represents the reflectance. At a reflection angle of 0°, the reflection angle of aluminum (A), which has a surface condition close to a mirror surface, is larger than that of silicon oxide on a silicon layer, and both have a high load resistance. However, in the case of aluminum (ω), which has a different surface condition, the aluminum reflection is almost the same as that of silicon oxide, and the contrast between the two is low. Therefore, although it is sufficient to maintain the aluminum surface in a mirror-like pattern using a general vapor deposition method, there is a problem in that it is actually greatly affected by the inclination of the semiconductor pellet.

This can be explained as follows. It is difficult to maintain accurate levelness when bonding the semiconductor pellet to its base. If horizontality cannot be maintained and the vertical line on the surface of the semiconductor pellet has a certain angle to the tapered part of the microscope, the incident angle of illumination will not be 0°, and the reflected brightness will be 1. The curve will look like Figure 3. In other words, is the direction of specular reflection that gives the maximum reflection the direction perpendicular to the surface of the pellet? Move in the direction opposite to the optical axis direction. If this is observed using a microscope with vertical epi-illumination as shown in FIG. 2, the entire reflective layer at the reflection angle P shown in the graph of FIG. 3 will be observed.

this? Compared to the case in Figure 2, the reflected cold is considerably attenuated for both aluminum (5) and silicon oxide. For example, numerical aperture 0
．． When using an objective lens of 1, since the object is 3°
Detection is possible if humans are visible.

When using automatic detection equipment, this reflex: change? must be compensated. Normally, not only the semiconductor pellet but also parts of the pedestal with different inclinations are captured in the imaging field of view. Therefore, the reflected cold does not change uniformly in the entire field of view, but only the part of the objective pellet is attenuated. Complement iX with a simple method
It's not easy to do. As a further supplement, it is often possible to greatly reduce the size of the video signal by processing it as two images (white or black) for automatic recognition. It is normal to determine whether it is white or black, but if there is a large change in the reflecting star such as a fortune, it is not possible to determine whether it is black or white with a certain threshold.Also, if the reflecting star changes only in the pellet part It is not easy to follow this threshold value.

On the other hand, considering that it is impossible to maintain the horizontality ti of the pellet, for example, in the case of a pellet with a minus side of 0.4 strokes, a 1 degree inclination results in a height difference of 0.007a++n at both ends of the minus side. When the pellets are bonded to the entire base pressure, the boundary surface dissolves, so it is not easy to suppress the difference in height to about 0.007 am or less.

The purpose of the present invention is to detect semiconductor pellets using a stable contrast between aluminum and silicon oxide, and in particular to eliminate the above-mentioned drawbacks of conventional illumination methods, such as being affected by the tilt of the pellet. .

In order to achieve the above object, in the semiconductor pellet of the present invention, the diffuse reflection component is increased on the aluminum surface. For example, as with aluminum CB in FIG. 1, the reflection brightness is made to have a certain level of intensity over all angles. A surface like this? In contrast to a mirror surface, it is sometimes called a diffuse reflection surface or a bundled surface.

The angle of incidence of illumination is carefully determined for pellets with such a surface. FIG. 4 shows the reflected luminance curve at that time.

Near O0, where the optical axis of the microscope is located, the specular reflection direction is not -, and the reflection brightness of silicon oxide is approximately O, so a high contrast with aluminum can be obtained. Further, when the target surface is tilted, the curve is the same as this graph moved in the horizontal axis direction, but the reflection curve in the 0° direction hardly changes. Therefore, a constant contrast is maintained regardless of the slight inclination of the pellet, and stable t-operation can be obtained in various automatic detection devices.

That is, the main points of the present invention are that the aluminum-deposited surface of the semiconductor pellet has a certain diffuse reflection component, and that the illumination direction is selected so that specularly reflected light does not enter the microscope.

Hereinafter, the present invention will be explained based on all embodiments.

First, there is no need to fundamentally change the manufacturing process of semiconductor pellets up to the wafer. The silicon oxide film may be formed by a conventional oxidation method, and no particular changes are required. Aluminum films are created by vapor deposition as in the past, but in order to maintain a diffusely reflective surface, it is necessary to appropriately set the conditions during vapor deposition. If the residual pressure during vapor deposition is increased, it will become a diffusely reflecting surface, but the surface will not be suitable for crimping gold wire, so the residual pressure will be about 10-torr.
Must be kept below. To create a diffuse reflection surface suitable for crimping gold wire, there are several methods: slowing down the deposition rate, increasing the film thickness, increasing the substrate temperature, and combinations thereof.The method should be selected depending on the @position used. Bye. For example, if you raise the specific value, the temperature will be 180°C to 25°C.
0°C & residual pressure 3X 10-"-8X I G"'
torr, and the film thickness is 1.5 to 2.5 arn.

Next, we will show how to provide illumination when observing pellets.

Fig. 5 shows a single shot of this.In addition to the microscope Jf cylinder 1 and the objective lens 2, a cylinder 5 containing a light source 3 and a condensing lens 4 is provided, which is in the field of view of the microscope and the above-mentioned aluminum reflector. Nature of rate? Illumination is applied to the semiconductor pellet 6 from an oblique direction. The image of the pellet thus illuminated is suitable for detection with the naked eye, and is captured by a fixed TV camera 7 to provide a stable and high-contrast image for automatic detection @ 8 for positioning, defect inspection, etc. be able to.

As shown in FIG. 6, light source 3. The same effect can also be obtained by guiding light from the condensing lens 4 through the optical fiber 9 and irradiating the light obliquely.

FIG. 7 shows an arrangement in which the microscope light fence is not perpendicular to the surface of the object. At this time, the illumination may be ordinary epi-illumination of a metal microscope, or another illumination tube may be used. In the latter case, illumination may be performed from any direction as long as the regular reflection of the illumination does not overlap with the optical axis of the microscope.

In the Okushiba example shown in FIG. 8, the microscope barrel 11 is double-layered, the light from the light source 3 is converted into parallel rays by the lens 12, guided to the outer barrel by the reflector 13, and a parabolic beam is formed from around the objective lens 20. The light is focused on the object by the reflected light 14. In this case, illumination is provided from a direction 360'c around the optical axis that forms a constant angle with the optical axis of the lacrimal microscope. Some commercially available metal microscopes have this kind of structure,
You can obtain the effect of night vision.

As explained above, according to the present invention, in automatic or visual detection of the position and defects of semiconductor pellets,
Images with constant contrast can be obtained regardless of the inclination of the beret, allowing stable operation or work.

[Brief explanation of drawings]

1 to 3 are explanatory diagrams of the conventional example, and FIGS. 4 to 8 are explanatory diagrams of the present invention. ＋S (Contents) of drawing (No change) yo' Guta diagram
qt,, 4th figure, 7th figure Fraud 89 Procedural amendment (method) % formula % Indication of the case 1985 Patent application No. 36335 Title of the invention Relationship with the person who amends the manufacturing method of semiconductor devices Case Patent Permission applicant name (510)
Manufactured by Hitachi Co., Ltd. Shinshiki Ri Resident address: 100 Marunouchi-cho, Chiyoda-ku, Tokyo [1l]
I5 No. 1 Hitachi Manufacturing Co., Ltd. Telephone Tokyo 212-1111 (Major Representative) Subject of amendment The claims section, detailed description of the invention section, and drawings of Book R4.

Claims (1)

[Claims] 1. When depositing aluminum on semiconductor pellets, the surface of the deposited aluminum film has a pear-like surface with a reflection brightness of a certain value or more over the entire irradiation angle. A method for manufacturing a semiconductor device, characterized by depositing aluminum under residual pressure. 2. The method for manufacturing a semiconductor device according to item 1, wherein the residual pressure is an atmospheric pressure of 3×10^-^6 Torr or more.