JPH07311017A - Semiconductor pellet height measuring device and measuring method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] The surface height of a semiconductor pellet is measured by a stereoscopic method and automatically calculated with high accuracy, and the capacity of an image memory for registering a reference pattern image is reduced. [Structure] Two image pickup cameras 11 and 12 installed obliquely above a semiconductor pellet 10 placed on a plane at a constant angle to the pellet, an image memory 22, and an image picked up by a first camera. Included in the image captured by the second camera and the first processing unit 211 that searches the pattern image of the measurement point included in the reference pattern image by matching with the reference pattern image and updates and registers it in the image memory as a new reference pattern image. The pattern image of the measured point to be searched is searched by matching with a new reference pattern image.
And the third processing means 213 for calculating the height at the measurement point on the pellet surface based on the position information of the pattern image obtained by these processings.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pellet height measuring device used in a semiconductor device manufacturing process and a measuring method therefor, and more particularly, to a surface height of a pellet placed on a flat surface by an imaging camera. The present invention relates to an apparatus and method for measuring by a stereoscopic method.

[0002]

2. Description of the Related Art In the process of assembling a semiconductor device, it is necessary to measure the surface height of pellets before they are wire-bonded to the pellets die-bonded on a lead frame by a non-contact method. is there.

Conventionally, as one of the methods for measuring the surface height of an object by a non-contact method, there is a method using a laser displacement meter using laser light. However, a laser displacement meter is not standardly provided in a semiconductor device (integrated circuit device) assembling apparatus, and the laser displacement meter is expensive and thus cannot be easily introduced. Further, the higher the precision of the laser displacement meter, the larger the size thereof, and the shorter the work distance. Therefore, it was difficult to mount the laser displacement meter on the assembly device.

Further, as another conventional method for measuring the surface height of pellets in a non-contact manner, a pattern matching device, which is standardly equipped in a semiconductor device assembling apparatus, is used, and a stereoscopic method by a CCD camera is used. There is a method to measure.

Here, a conventional method for measuring the surface height of pellets by a stereoscopic method using a CCD camera will be described with reference to FIG. Semiconductor pellet 1
Two CCD cameras 11 and 12 are installed at a fixed angle with respect to the pellets diagonally above 0. Then, the two images A and B on the surface of the pellet respectively captured by the two CCD cameras are input to the processing unit 31 of the pattern matching device 30.

Then, the processing unit 31 searches the pattern images of the measurement points on the pellet surface included in each of the two images A and B by matching with a reference pattern image registered in advance. Then, the position of the pattern on the pellet surface is detected, and the height at the measurement point (pattern position) on the pellet surface is calculated based on this position information.

In this case, before the surface height of a certain pellet is measured, the above-mentioned reference pattern is pattern-matched between two reference pattern images obtained by respectively capturing the surface of another pellet serving as a reference with two CCD cameras. Device 30
The ones stored (registered) in the image memories 32 and 33 therein are used.

However, in the conventional measuring method as described above, the two pattern images respectively picked up by the two CCD cameras and the reference pattern image are pellets different from each other. Difference directly affects the pattern matching processing result (position information of the pattern) as a deviation, resulting in an error in the calculated pellet surface height.

Moreover, since the pattern matching processing is performed separately for the two pattern images respectively picked up by the two CCD cameras, a measurement error occurs when the processing results of the respective images are deviated. It will be even bigger.

In the pattern matching process,
Since a reference pattern is used for each CCD camera, at least two reference patterns are required to search for a pattern at one point, and the capacity of the image memory in the pattern matching device becomes large.

[0011]

As described above, the conventional pellet height measuring method for calculating the pellet surface height based on the positional information of the pattern image obtained by imaging the pellet surface by the stereoscopic method is known. However, there is a problem that a calculation error is likely to occur and the capacity of the image memory for pre-registering the image of the reference pattern becomes large.

The present invention has been made to solve the above problems, and when calculating the pellet surface height based on the positional information of the pattern image detected by imaging the pellet surface by the stereoscopic method, The pattern image can be detected with high accuracy and the surface height of the pellet can be calculated automatically with high accuracy.
An object of the present invention is to provide a semiconductor pellet height measuring device and a measuring method thereof, which require a small capacity of an image memory for registering an image of a reference pattern.

[0013]

SUMMARY OF THE INVENTION A semiconductor pellet height measuring apparatus according to the present invention is a first image pickup camera installed obliquely above a semiconductor pellet placed on a plane and at a constant angle with respect to the pellet. Device and a second imaging camera device, an image memory, and an image of a measurement point on the pellet surface included in the image captured by the first imaging camera device, and a reference pattern image registered in advance in the image memory. In the second image pickup camera device, there is provided a first processing means for performing a search process to detect the detected pattern image and updating and registering the detected pattern image in the image memory as a new reference pattern image. The pattern image of the measurement point on the pellet surface included in the captured image is to be matched with the above new reference pattern image. Ri second to detect by performing a search process
And a third processing means for calculating the height at the measurement point on the pellet surface based on the position information of the pattern image of the measurement point on the pellet surface obtained by these processing means. It is characterized by having.

Further, in the semiconductor pellet height measuring method of the present invention, the pattern image of the measurement point on the pellet surface included in the image obtained by picking up the semiconductor pellet placed on the plane with the first image pickup camera is previously set. A first step of performing a search process to detect by performing matching with a reference pattern image registered in the image memory, and updating and registering the detected pattern image in the image memory as a new reference pattern image; Second pellet
The second step of performing a search process to detect the pattern image of the measurement point on the pellet surface included in the image captured by the image capturing camera by matching with the new reference pattern image, and these processes. A third step of detecting the position of the measurement point on the pellet surface based on the position information of the detected pattern image, and calculating the height at the measurement point on the pellet surface based on this position information. It is characterized by doing.

[0015]

According to the measuring device, the pattern image taken by the second image pickup camera is searched by using the pattern image taken by the first image pickup camera as the reference pattern image. As a result, it is not necessary to register two reference pattern images in the image memory in advance, and only one reference pattern image needs to be registered. Therefore, the image memory capacity for registering the reference pattern images is small. Can be realized at low cost.

According to the above measuring method, the first (first
When performing the first step in the measurement of the (th) pellet, the reference pattern image registered in the image memory in advance is used. Then, when performing the first step for the second and subsequent pellets, the new reference pattern image registered in the image memory at the time of measuring another pellet at the previous time is used, but the same as at the time of the previous pellet measurement. Since the pattern image captured by the first camera is used as the reference pattern image, it can be considered that the detection deviation of the pattern image is eliminated. Further, in the second step, since the pattern image obtained at the time of executing the first step for the same pellet is used as the reference pattern image, the delicate influence of the pattern due to the difference in pellet is eliminated, and the detection deviation of the pattern image is small. Become.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows an embodiment of a semiconductor pellet height measuring device of the present invention. In FIG. 1, 10 is a semiconductor pellet to be measured, which is placed on a flat surface such as a lead frame. In order to measure the surface height of the pellets by the stereoscopic method, a plurality of imaging camera devices, for example, the first CCD camera 11 and the second CCD camera 12 are fixed diagonally above the pellets and fixed to the pellets. It is installed at an angle.

A computer system is used as the pattern matching device 20, and a pattern matching processing section 21 and an image memory 22 are provided. As shown in FIG. 2, the pattern matching processing section 21 includes a first processing unit 211, a second processing unit 212, and a third processing unit 213.

The first processing means 211 uses the pattern image of the measurement points on the pellet surface included in the image picked up by the first CCD camera 11 as the reference pattern image registered in the image memory 22 in advance. Search processing is performed by matching, and the pattern image detected by this search processing is updated and registered in the image memory 22 as a new reference pattern image.

The second processing means 212 performs a search process by matching the pattern image of the measurement point on the pellet surface included in the image captured by the second CCD camera 12 with the new reference pattern image. Is performed and the pattern image is detected.

The third processing means 213 on the pellet surface is based on the position information of the pattern image of the measurement points on the pellet surface obtained by the first processing means 211 and the second processing means 212, respectively. The height at the measurement point is calculated.

FIG. 3 is a flow chart showing an example of a method for measuring the surface height of a semiconductor pellet by using the semiconductor pellet height measuring device of FIG. In this measurement method, in the first step, a pattern image of a measurement point on the pellet surface included in an image obtained by capturing the semiconductor pellet 10 placed on a flat surface such as a lead frame with the first CCD camera 11, Search processing is performed by matching with a reference pattern image registered in the image memory 22 in advance, and the pattern image obtained by this search processing is updated and registered in the image memory 22 as a new reference pattern image.

In the second step, a search process is performed by matching the pattern image of the measurement point on the pellet surface included in the image of the pellet 10 captured by the second CCD camera 12 with the new reference pattern image. To do.

In the third step, the position of the measurement point on the pellet surface is detected based on the pattern images obtained by these search processes, and the height at the measurement point on the pellet surface is detected based on this position information. Calculate the

Then, the plurality of pellets to be measured are sequentially replaced and the first to third steps are executed. In this case, when performing the first step when measuring the first (first) pellet,
The reference pattern image registered in advance in the image memory 22 is used, but when the first step is executed for the second and subsequent pellets, the reference pattern image is updated in the image memory 22 at the time of measuring another pellet last time. The registered new reference pattern image is used.

Here, when measuring the surface height of the pellet by the stereoscopic method as described above, the third processing means 213 measures the surface height of the pellet based on the obtained positional information of the pattern on the pellet surface. The operating principle of calculating the height at a point (pattern position) will be briefly described with reference to FIG.

When the measurement target point P is imaged by the left and right cameras, the position on the imaging surface 11a of the left camera (for example, the first CCD camera 11) that the measurement target point P looks like is determined by the right camera (for example, the first camera). Image plane 1 of 2 CCD cameras 12)
The distance from the camera position to the measurement target point P can be calculated depending on which position on the 2a the image looks like.

That is, the position of the measurement point image P on the imaging surface 11a of the left camera approaches the right direction as the distance from the left camera position to the measurement target point P approaches, but on the imaging surface of the right camera. The position of the measurement point image P shifts to the left as the distance from the right camera position to the measurement target point P decreases.

Therefore, if the calibration data for which the relationship between the movement amount of each of the positions of the measurement point image P on the photographing surface and the actual movement amount of the measurement target point P is obtained in advance is prepared, If the position of the measurement point image P on the quadrant is known, the position of the measurement target point P is calculated by referring to the calibration data,
Based on this, the height of the measurement point P on the pellet surface can be calculated.

According to the measuring device of the above embodiment, the first C
The pattern image captured by the second CCD camera 12 is searched using the pattern image captured by the CD camera 11 as a reference pattern image. The pattern matching device 20 used in this case does not need to register two reference pattern images in the image memory 22 in advance, as compared with the existing inexpensive pattern matching device that is standardly equipped in the semiconductor device assembling device. Since only one reference pattern image needs to be registered, the capacity of the image memory 22 for registering the image of the reference pattern is small, and the cost can be further reduced.

Further, according to the measuring method of the above embodiment, the surface height of the pellet can be easily measured as in the conventional stereoscopic measuring method. Moreover, when measuring the second and subsequent pellets, the first step uses the new reference pattern image registered in the image memory at the time of measuring another pellet last time. Since the pattern image captured by the camera 11 is used as the reference pattern image, it can be considered that the detection deviation of the pattern image is eliminated. Further, in the second step, since the pattern image obtained at the time of executing the first step for the same pellet is used as the reference pattern image, the delicate influence of the pattern due to the difference in pellet is eliminated, and the detection deviation of the pattern image is small. Become.

The two CCD cameras 1 are used with the pattern of the pellets actually imaged as described above as a reference pattern.
Since the pattern images picked up by Nos. 1 and 12 are searched, the pattern image picked up by the second CCD camera 12 is not affected by the difference between the pattern to be searched and the reference pattern, and even if a detection deviation occurs. It is possible to detect the pattern position with a much higher accuracy than in the conventional case, and the surface height and error of the pellet calculated based on the pattern position information are reduced.

[0033]

As described above, according to the present invention, when the surface height of the pellet is measured by the stereoscopic method, the measured value can be automatically calculated with high accuracy and the image of the reference pattern is registered. Therefore, it is possible to realize a semiconductor pellet height measuring device and a measuring method thereof, which require a small image memory capacity.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a semiconductor pellet height measuring device of the present invention.

FIG. 2 is a block diagram showing an example of a pattern matching processing unit in FIG.

3 is a flowchart showing an example of a semiconductor pellet height measuring method using the measuring device of FIG.

FIG. 4 is a diagram for explaining the operating principle of calculating the height at a measurement point (pattern position) on the surface of the pellet by the third processing means in FIG. 1.

FIG. 5 is a block diagram showing a conventional semiconductor pellet height measuring device.

[Explanation of symbols]

10 ... Semiconductor pellet, 11 ... First CCD camera, 1
2 ... Second CCD camera, 20 ... Pattern matching device, 21 ... Pattern matching processing section, 211 ... First processing means, 212 ... Second processing means, 213 ... Third processing means, 22 ... Image memory.

Claims (2)

[Claims] 1. A first image pickup camera device and a second image pickup camera device, each of which is installed obliquely above a semiconductor pellet placed on a plane at a predetermined angle with respect to the pellet, an image memory, and The pattern image of the measurement point on the pellet surface included in the image captured by the first image capturing camera device is detected by performing a search process by matching with a reference pattern image registered in the image memory in advance, A first processing unit that updates and registers the detected pattern image as a new reference pattern image in the image memory, and a pattern image of a measurement point on the pellet surface included in the image captured by the second image capturing camera device. , Second processing means for performing a search process to detect by performing matching with the new reference pattern image, and Detecting the position of the measurement point on the pellet surface based on the position information of the pattern image obtained by the processing means, and calculating the height at the measurement point on the pellet surface based on this position information 3. A semiconductor pellet height measuring device comprising the processing means of 3. 2. A pattern image of a measurement point on the pellet surface included in an image obtained by picking up a semiconductor pellet placed on a plane by a first image pickup camera is used as a reference pattern image registered in an image memory in advance. A first step of performing a search process by performing matching and detecting the detected pattern image, and updating and registering the detected pattern image as a new reference pattern image in an image memory; and an image of the semiconductor pellet imaged by a second imaging camera. Second step of performing a search process to detect the pattern image of the measurement point on the surface of the pellet included in the above-mentioned new reference pattern image, and the position of the pattern image detected by these processes. The position of the measurement point on the pellet surface is detected based on the information, and based on this position information And a third step of calculating the height at the measurement point on the pellet surface based on the above.