JPS5851416B2 - Manufacturing method of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a structure of an electrode pattern for facilitating the recognition of the bonding position of a semiconductor pellet of thin metal wire.

Generally, when drawing a thin metal wire from a semiconductor pellet placed on a stem, a bonding tool that vibrates with ultrasonic waves is used to press the gold or aluminum wire against the electrode on the semiconductor pellet, and the frictional heat is used to draw out the metal wire. The thin wire and the electrode surface are welded together.

In this case, the bonding tool must be positioned with respect to the electrode of the semiconductor pellet, so conventionally, each semiconductor pellet was inspected and aligned by operating a manipulator.

However, since this method has poor workability, an automatic bonding method has been used to improve the efficiency of this method.

This allows the semiconductor pellet placed on the stem to be
The image is captured with a camera, pattern recognition is performed, the position of the semiconductor pellet and its electrode position are detected, and the bonding apparatus is controlled by a computer to automatically perform the bonding work.

By the way, this pattern recognition is specifically performed in the following steps.

First, as shown in FIG. 1, a semiconductor pellet 2 fixed on a stem with solder 1 is imaged with a CCD camera or the like.

The screen information obtained in this way is horizontal and vertical, for example 19
It is divided into picture elements of 0x244 bits.

This is determined using an appropriate reference value and binarized to obtain screen information divided into white or black for each picture element.

As shown in FIG. 2, the binarized screen information shows that the aluminum vapor-deposited electrode 3 on the semiconductor pellet 2 is white, the oxide film 4 as an insulating film, and the solder layer 1 spreading from the bottom of the semiconductor pellet 2 to the surrounding area are white. Identified by black.

In addition, the corner 2' of the semiconductor pellet 2 and the part 1 of the solder layer 1
′ is also irregularly identified as white depending on the light reflection conditions.

In order to detect the bonding position of the specified thin metal wire on the electrode from the screen information of the semiconductor pellet 2 that has been binarized in this way, it is necessary to In addition to removing erroneous information from other sources, the peripheral part of the white pattern obtained from the electrode 3 must be removed.

For this reason, conventionally, as shown in FIG.
The screen information is scanned with a certain mask 6 for judgment, and it is checked whether the picture element seen from each seat is black or white. When all the windows 5 are white, the picture element corresponding to the central window 5s is detected. is white, and if there is even one window 5 where black can be seen, the central window 5s
The operation of forcibly turning the picture elements corresponding to black to black is performed on the entire screen area.

Then, as shown in FIG. 4, the small-area white pattern disappears, and the large-area white pattern also has its periphery cut off and its area becomes smaller.

By repeating this scanning while changing the judgment mask 6 to a smaller one or a different shape, as shown in FIG. The white pattern of false information due to discontinuous reflection disappears, and a white pattern 3' remains only at the bonding position at the center of the electrode.

Then, as shown in Figure 6, measure the rectangular frame in which the remaining white pattern 3' will fit, and
The bonding position 8 was detected by calculating the coordinates of the center from the rotor of the direction.

However, the electrode 3 of the semiconductor pellet 2 is specified in relation to its characteristics and has a complicated shape.

For this reason, accurate positioning may not be possible even if a sequential scanning method is used using the determination mask 6 having a window.

For example, in a semiconductor pellet 2 having an electrode pattern as shown in FIG. 1, the final white pattern 3' left is vertically long, making it difficult to achieve accuracy in the vertical direction.

Therefore, as shown in FIG. 1, there is a method of correcting this using a vertically long mask 7.

However, the thin oxide film 4 around the electrodes may not be photographed properly using a CCD camera or the like, and the thin oxide film 4 may appear white.
Screen information after scanning with the determination mask 6 tends to be long in the vertical direction.

Then, when the bonding position is finally detected, a positional deviation of about half of the length extending in the vertical direction occurs.

As described above, when the photographic image is distorted, the screen information cannot be corrected even if the types of the determination masks 6 and 7 are changed and used in combination, resulting in a detection error.

Therefore, in view of the above-mentioned drawbacks, this invention improves this, and
By providing a dotted or linear pattern in the electrode that has a contrast with the electrode surface, the bonding position in the electrode can be easily detected by mask processing.

The dotted or linear pattern provided in the electrode of the present invention may be provided at a position where a white pattern is likely to extend in the longitudinal direction when the electrode is binarized and scanned with a determination mask.

For example, in the semiconductor pellet 2 as shown in FIG.
The electrode 3 is elongated by a thin oxide film 4 that partitions the electrodes 3, 3.

When the electrode portion 3'' on the tapered side is binarized and scanned with the determination mask 6, a white pattern tends to extend unstably in the longitudinal direction.

Therefore, in this case, as shown in FIG. 8, a dot-like pattern 9 having contrast with the electrode is provided between the bonding position 8 of the electrode 3 and the tapered part 3'' of the electrode 3.

This dotted pattern 9 may be formed simultaneously with the oxide film 4 when forming the electrode.

Further, the dotted pattern 9 may be formed by applying ink that does not affect the characteristics after the electrode is formed.

In this way, when the dotted pattern 9 is formed, CC
After binarizing the image taken with a D camera etc., if it is scanned with the determination mask 6, a black pattern will spread around the dotted pattern 9, as shown in FIGS. 9 and 10.
Each time the determination mask 6 is changed to a smaller one and scanned, the white pattern 3' is reduced from 3a to 3b.
A nearly circular white pattern 3b is left at the regular bonding position 8.

On the other hand, by measuring the distribution in the X and Y directions and calculating the center position, accurate bonding position detection is possible.

Note that the dot pattern having contrast with the electrode can be provided at one or more appropriate locations depending on the shape of the electrode of the semiconductor pellet 2.

For example, they may be provided at several locations surrounding the bonding position of the electrode.

However, if a large number of electrodes are provided using an oxide film, the electrode area will decrease and the current capacity will become smaller, which is not preferable.

If there is a risk that the electrode may extend in the longitudinal direction due to the poor visibility of the electrode shape or pattern on the camera, it is effective to form it to act as a stopper.

As explained above, according to the present invention, when recognizing the bonding position on the electrode from the binarized image of the semiconductor pellet, the recognition accuracy is poor due to the irregularly spread shape of the electrode. It is also possible to eliminate recognition errors when images cannot be accurately captured due to thin electrode boundaries.

In addition, the pattern recognition of this invention uses a dotted or linear pattern, and detects the bonding position by gradually reducing the area set to have almost the same width and width. It is no longer necessary to use a determination mask 7 having an irregular shape as shown in FIG. 7 in order to reduce the size by a large amount, and reliability is also improved.

[Brief explanation of drawings]

Figure 1 shows a conventional semiconductor pellet placed on a stem, Figure 2 shows a binarized image of the semiconductor pellet, and Figures 3 and 7 show the bonding position. Figures 4 and 5, which are diagrams showing examples of the shape of the determination mask, are explanatory diagrams of the procedure for pattern recognition of bonding positions using the determination mask from the binarized image shown in Figure 2. FIG. 6 is an explanatory diagram of a method for detecting a bonding position from a reduced electrode pattern, FIG. 8 is a diagram showing a semiconductor pellet of the present invention placed on a stem, and FIGS. FIG. 3 is an explanatory diagram of a procedure for pattern recognition using a determination mask from an image obtained by imaging the semiconductor pellet shown in the figure. 1... Solder layer, 1'... Part that appears white due to reflection in the solder layer, 2... Semiconductor pellet, 3... Electrode, 4... ...Oxide film, 5,
5s... Window of judgment mask, 6,7...
・Determination mask, 8...Bonding position, 9
・・・・・・Dot pattern.

Claims (1)

[Claims] 1 Prior to determining the bonding position of the thin metal wire by masking the electrode part in the recognized image of the semiconductor pellet, a dotted or linear pattern having contrast with the electrode surface is appropriately formed on the electrode surface of the semiconductor pellet. A method for manufacturing a semiconductor device, characterized in that the range of mask processing is reduced by: