JPS6360432B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to pattern recognition, and is particularly applied to automatic wire bonding equipment for semiconductor devices, and detects the relative position and rotational deviation angle between a chip and a bonding pad on the chip. The present invention relates to a method and apparatus for figure (pattern) recognition.

One of the pattern recognition methods is the so-called pattern matching method, in which a target pattern is compared with a master pattern, and if they match, the two patterns are determined to have the same quality.
With this pattern matching method, it is difficult to correctly recognize when there is an angular shift in the target pattern.

As a way to solve this problem, it has been considered to set a large amount of deviation in the range that is considered a match, or to prepare several types of master patterns with angular deviations, but the former reduces recognition accuracy, and the latter This creates new problems such as larger equipment and longer determination times.

One of the more advanced solutions is to detect the angle of deviation by some method and correct the data of the master pattern accordingly, but in this case as well, the detection of the angle of deviation is highly accurate and simple. is required.

The purpose of the present invention is to focus on the fact that semiconductor chips generally have a rectangular external shape, and that a plurality of bonding pads on the chip are formed in a rectangular shape with each side parallel to each side of the chip. To do this, the corner of the chip and the corner of the bonding pad have the same shape, and by pattern matching by comparing the two, the relative position of the chip and the chip and each bonding pad on the chip can be rotated. To enable easy and accurate detection without being affected by deviation, and to easily calculate a rotational deviation angle if necessary.

The purpose of this is to recognize a rectangle in which the figure to be recognized is a rectangle that is the outer shape of a semiconductor chip and each rectangle of a plurality of bonding pads formed on the chip with each side parallel to each side of the chip. A pattern obtained by scanning a region including the outer corner of the recognition semiconductor chip is used as a master pattern, and a pattern of each bonding pad obtained by scanning the chip to be recognized is compared with the pattern of each bonding pad. Achieved by a figure recognition method characterized in that the relative position between the corner of each chip and the corresponding corner of each bonding pad is recognized by recognizing the corresponding corner of the chip. be done.

Furthermore, the present invention provides a signal with a good S/N ratio against the background, such as when recognizing a bonding pad (hereinafter simply referred to as a pad) formed on a semiconductor chip (hereinafter simply referred to as a chip). , that is,
This is particularly effective when a signal representing the external shape of the chip exists and the shape of the pattern represented by the signal (the external shape of the chip) is partially the same as the pattern to be recognized, that is, the shape of the pad. below,
The present invention will be explained according to the drawings.

FIG. 1 shows a system that automatically performs wire bonding of semiconductor devices. The semiconductor chip 1 is scanned and imaged by a video camera 2,
The obtained image signal is converted into a binarized pattern signal by the binarization circuit 3. Furthermore, pattern recognition processing is performed by the recognition processing and position detection section 4, and the pad position is detected. The movement of the stage 6 is adjusted based on the detected part position information, and bonding is performed. 5 is a control unit that controls the bonder based on position information.

Pattern matching is performed in the pattern recognition processing step, and in the present invention, a master pattern used at that time is obtained as follows.

Semiconductor chips and bonding pads are usually formed into squares or rectangles, as shown in FIG.
Moreover, the sides of the chip 8 and the sides of the pad 9 are parallel.
Therefore, these equivalent parts, for example the upper left corners, have the same shape.

In one embodiment of the invention, the location of a particular portion of the chip, such as the upper left corner, is first detected.
Since the approximate location of the chip is determined,
It is easy to place this part within the field of view of the video camera. Now, assume that there is a slight angular shift in the chip position and the chip is in the position shown in FIG. 3a. If the range of the figure is scanned from the bottom left to the top right (or vice versa), and the scanning line is moved from the top left to the bottom right, the pattern signal will be at the level of the background part of the edge (this is set to 0). ), but when the scan reaches the upper left corner of the chip, the level of the chip (which is assumed to be 1) appears in that area, and in subsequent scans, the area indicating the 1 level expands. The position of the upper left corner of the chip is determined from the situation of such changes in the pattern signal.

In this case, in the output of the video camera, there is a large difference between the signal level of the background part and the signal level of the chip part, and the S/N of the signal binarized by setting the slice level between the two is extremely high. The results are good, and the accuracy of pattern detection is high.

Next, as shown in FIG. 3a, a specific area is defined as indicated by the dotted line using the corner of the chip as a reference. Since this area is used as a master pattern, the larger the size, the higher the recognition accuracy, but not only will the matching process take more time, but if it is too large, it will be impossible to define the same pattern area in the pad area, and the master pattern will be larger. Since it cannot be used as a pattern, it is better to limit the size to the size required for recognition accuracy.

FIG. 3b shows the master pattern cut out in this way. Since this master pattern has the same conditions as the pad, which is the pattern to be recognized, with respect to angular deviation, all problems caused by angular deviation can be solved by performing matching processing using this master pattern.

After setting the master pattern in this way, a portion matching this pattern is searched from the chip area. As a result, as shown in FIG. 4, for example, there are three matching parts, namely points P ₁ (x ₁ , y ₁ ), P ₂ (x ₂ , y ₂ ), and P ₃ corresponding to vertex C of the master pattern. ( _x3 , _y3 )
Suppose that is detected. If these points represent each pad, the point closest to the corner C (xc, yc) of the chip
Since P ₁ is a pad located at the corner of the chip, the deviation angle of the chip is calculated from the coordinates of this point and another corner point of the pad, for example P ₂ .

The deviation angle can also be calculated from the coordinates of these three points. In particular, if the pads are arranged in a matrix and the triangle connecting the three points P ₁ , P ₂ , and P ₃ is a right triangle, the apex of _the right angle is It is determined that it is the apex of the pad formed at the corner, and the deviation angle is calculated by the above-mentioned means.

As described above, according to the method of the present invention, since the master pattern is extracted from the target pattern and the matching process is performed, there is no influence of angular deviation due to rotational deviation in this process, and the corners of the chip The position relative to the corner of the pad can be easily detected, and if necessary, the rotational deviation angle can also be calculated, so the wire holder can be controlled based on each detected position to perform wire bonding. It can be implemented.

The method of the present invention can be carried out as described above if there is a pattern that can be detected with a good S/N ratio and a part of the pattern has the same shape as a part of the pattern to be recognized.

Next, an apparatus for carrying out the method of the present invention will be explained.

As shown in FIG. 5, a pattern signal 101 corresponding to one scan 100 has three normal levels. That is, a background level 102, a chip level 103, and a pad level 104. As shown in FIG. 5, two slice levels C and P are set between these levels.

The configuration of the pattern recognition device is as shown in FIG. 6, which corresponds to parts 3 and 4 in FIG. The image signal is binarized using the slice level C, and the external shape of the chip is detected, and a master pattern is set by a predetermined operation. On the other hand, in parallel with this processing, the pattern signal binarized by the slice level P is stored in a shift register matrix and compared with the master pattern signal created by the above method. When a match is found, a matching address is sent out.

Based on the positional information obtained in this way, the stage control section (corresponding to 5 in FIG. 1) moves the stage so as to correct the positional deviation and performs bonding at the correct position.

According to the present invention, it is possible to obtain a device that quickly and reliably detects bonding pads without increasing the size of the processing device.

[Brief explanation of drawings]

Fig. 1 shows a system for automatically wire bonding semiconductor devices, Fig. 2 shows the shapes of a semiconductor chip and bonding pads, and Fig. 3 shows the definition of a master pattern, which is a requirement of the present invention. FIG. 4 is a diagram showing the portion that matches the master, FIG. 5 is a diagram showing the relationship between the pattern signal and the slice level, and FIG. 6 is a diagram schematically showing the present invention. 2 is a video camera; 3 is a binarization circuit; 4 is a device for pattern recognition processing and position detection; 5 is a bonder control unit; 6 is a movable stage; 7 is a bonder; 8 is a semiconductor chip;
9 is the bonding pad, 100 is the scanning line, 10
1 is the pattern signal; 102, 103, and 104 are the signal levels of the background, chip, and pad areas, respectively;
Pc is the corner point of the chip, and P ₁ , P ₂ , and P ₃ are the corner points of the pad.

Claims (1)

[Claims] 1. Figure recognition in which the figure to be recognized is a rectangle that is the outer shape of a semiconductor chip, and each rectangle of a plurality of bonding pads formed on the chip, each side of which is parallel to each side of the chip. In this step, a pattern obtained by scanning a region including the outer corner of the semiconductor chip to be recognized is used as a mask pattern, and a pattern of each bonding pad obtained by scanning the semiconductor chip to be recognized is compared with the pattern of each bonding pad. A figure recognition method characterized by recognizing corresponding corners of a bonding pad. 2. A scanning device for obtaining an image signal by scanning a semiconductor chip having a plurality of rectangular bonding pads having sides parallel to the sides of the chip on the rectangular chip, and a scanning device for obtaining an image signal from the image signal. A binary image signal representing a chip and a pad 2 representing only a portion of a bonding pad on the semiconductor chip.
a binarization circuit that outputs a value image signal; a binarization circuit that extracts a corner of the chip from the chip binary image signal to create a master pattern signal; A device for detecting corresponding corners of each of the bonding pads by comparison.