JPH06224293A - Method and apparatus for detecting cutting line position of semiconductor wafer - Google Patents

Abstract

PURPOSE:To automatically detect a position of a cutting line, and to input detected position information directly to a controller of a dicing unit by imaging a semiconductor wafer, fetching its image information and processing the information thereby to detect the position of the line. CONSTITUTION:A method for detecting a position of a cutting line to detect the position of the line when a semiconductor wafer 11 is diced comprises the steps of imaging the wafer 11, fetching its image information, and processing the information to detect the position of the line. For example, a wafer fixing table 13 is moved to a position directly under a CCD camera 3, a surface of the wafer 11 disposed directly under the camera 3 is imaged by the camera 3, its image information is digitized by an A/D converter 5, and input to a computer 2. The computer 2 processes the information according to a suitable algorithm to detect the position of the line.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to semiconductor wafer dicing, and more particularly to a method and apparatus for detecting the position of a cutting line on a semiconductor wafer.

[0002]

2. Description of the Related Art Many devices are mounted on a semiconductor wafer.
For example, electronic devices such as integrated circuits, optical devices such as laser diodes and photodiodes, or optoelectronic integrated circuits (OEI) in which electronic devices and optical devices are combined.
When C) etc. are formed and this semiconductor wafer is divided into individual devices, a dicing apparatus is usually used.

A general dicing apparatus is provided with a horizontally movable wafer fixing table and a high-speed rotatable dicing blade which is vertically moved with respect to a semiconductor wafer fixed on the wafer fixing table. Under the control of the controller, the dicing blade cuts the center line of the scribe line formed between the devices to divide the semiconductor wafer.

[0004]

However, in the conventional dicing apparatus, since the operator manually inputs the position information of the cutting line, that is, the center line of the scribe line to the controller, an input error may occur. There was a little. In such a case, the semiconductor wafer cannot be cut along a desired cutting line, and there is a risk of defective division. The dicing process of the semiconductor wafer is the final process of the wafer process, and the cost damage due to the division failure is very large. In particular, in recent years, semiconductor manufacturing is shifting from small-quantity mass-production with Si-DRAM at the forefront to multi-product small-quantity production centered on integrated circuits (ASICs) for specific applications, which solves this problem. That is an important issue. That is, when various types of devices are formed on the same semiconductor wafer, the scribe line intervals are not constant because the dimensions of the devices are different, and as a result, input errors are likely to occur.

Further, the position of the cutting line can be detected by using a microscope device or the like provided in the dicing device, but since the labor is great, the detection of the position of the cutting line is automated. Is desired.

Therefore, a cutting line position detecting method and device capable of automatically detecting the position of the cutting line of the semiconductor wafer to be actually cut and directly inputting the detected position information to the controller of the dicing device have been provided. It has been demanded. It is an object of the present invention to provide such a method and device.

[0007]

In order to achieve the above object, the present invention according to claim 1 provides a semiconductor wafer cutting line position detecting method for detecting the position of a cutting line when dicing a semiconductor wafer. It is characterized in that the position of the cutting line is detected by picking up an image of the semiconductor wafer, capturing the image information thereof, and subjecting this image information to image processing.

When the cutting line is the center line of the scribe line formed between the devices on the semiconductor wafer, the scribe line information is extracted from the image information of the semiconductor wafer, and the scribe line center line is extracted from the scribe line information. Is preferably detected.

Further, the scribe line information is extracted by forming a template in advance from the known information of the width of the scribe line and taking the correlation between the template and the image information of the semiconductor wafer, that is, by performing the pattern matching. can do.

Further, in the case of extracting the scribe line information, when a region having substantially the same characteristic points extracted from the image information of the semiconductor wafer exists in a predetermined direction by a set amount or more, the region is referred to as a scribe line. It is effective to recognize.

On the other hand, since the scribe line exists between the bonding pad row of the device and the bonding pad row of the device adjacent thereto, the information of the bonding pad of the device on the semiconductor wafer can be obtained from the image information of the semiconductor wafer. It is also possible to extract and detect the position of the center line of the scribe line from the bonding pad information.

Further, it is possible to extract the bonding pad information by forming a template from the known information of the dimensions of the bonding pad and taking the correlation between the template and the image information.

A cutting line position detecting device for carrying out such a cutting line position detecting method is, as described in claim 8, an image pickup means for picking up an image of a semiconductor wafer and taking in image information thereof, and the image pickup means. Image processing means for performing image processing on the input image information to detect the position of the cutting line.

[0014]

In the cutting line position detecting method and apparatus according to the present invention, since the image information of the semiconductor wafer to be diced is fetched and image processed, the position of the cutting line to be actually cut is accurately detected.

When the cutting line is the center line of the scribe line, as described above, the position detection is facilitated by extracting the information of the scribe line itself and the information of the bonding pad from the image information. In such cases,
The detection accuracy is further improved by applying the pattern matching method using the template.

When a test pattern (TEG) or the like is formed on the scribe line, it is difficult to recognize the scribe line. However, since the ratio of TEG or the like on the scribe line is generally known, if it is found that a region having substantially the same feature points extracted from the image information exceeds the set amount, that region is called the scribe line. Can be recognized.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 schematically shows a dicing apparatus 10 having a cutting line position detecting device 1 according to the present invention. As shown in the figure, the dicing device 10 has a dicing blade 12 as a cutting means for cutting the semiconductor wafer 11, and also has a wafer fixing table 13 for fixing the semiconductor wafer 11.

The dicing blade 12 is a support column 1
It is attached to a spindle 16 of a spindle head 15 which is supported by 4. The support column 14 is fixed to a bed 17 which is a fixed structure so as to be oriented vertically, and the spindle head 15 is vertically moved along the support column 14. The main shaft 16 extends in the horizontal direction and is rotated at high speed.

On the other hand, the wafer fixing table 13 is attached to the upper surface of the bed 17 and can move linearly along two horizontal axes which are orthogonal to each other. Also,
The upper surface of the wafer fixing table 13 is a horizontal wafer fixing surface 18, and this surface 18 is rotatable in both forward and backward directions about a vertical axis. The semiconductor wafer 11 is fixed on the wafer fixing surface 18 by vacuum suction, preferably in a state of being attached to the dicing tape 19.

In such a structure, while the dicing blade 12 is rotated, the spindle head 15 is lowered from the initial position by a predetermined amount, and then the wafer fixing table 13 is moved.
Drive the semiconductor wafer 11 to the dicing blade 1
When moving along the direction of the surface of rotation 2, the cutting for one row is performed. Thereafter, in order to move to the next row of cutting, the spindle head 15 is raised to the initial position, and the semiconductor wafer 11 is moved by a predetermined distance in a direction perpendicular to the cutting direction.
By repeating this, the semiconductor wafer 11 is cut into strips. Next, the semiconductor wafer 11 cut into strips is rotated by 90 degrees, and the above steps are repeated to form a large number of chips from one semiconductor wafer 11. The controller 2 controls such operations.
It is performed by 0.

The position information of the cutting line of the semiconductor wafer 11 is input to the controller 20 in advance, and under the control of the controller 20, the semiconductor wafer 11 is cut at the input position. In the present embodiment, the cutting position information is input to the controller 20 automatically from the cutting line position detecting device 1 of the present invention.

The cutting line position detecting device 1 according to the present invention uses an image processing technique. Basically, a computer 2 as an image processing means and a semiconductor wafer 11 are used.
And a CCD camera 3 which is an image pickup means for inputting the image information to the computer 2 on the surface of the. The CCD camera 3 is fixed to the bed 17 via the arm 4 at a position horizontally spaced from the dicing blade 12, and the wafer fixing table 13 can be moved to a position directly below the CCD camera 3. Has become.

According to the cutting line position detecting method of the present invention, the CCD camera 3 captures an image of the surface of the semiconductor wafer 11 arranged immediately below it, digitizes the image information by the A / D converter 5, and computer. Enter 2.
The computer 2 performs image processing on the input image information according to an appropriate algorithm and detects the position of the cutting line.

Here, FIG. 2 is a plan view schematically showing the surface of the semiconductor wafer 11 to be cut, and solid lines drawn in a lattice pattern on the semiconductor wafer 11 are scribe lines S. Normally, the cutting line is generally the center line of the scribe line S. Hereinafter, the computer 2 processes the position detecting method according to the present invention when detecting the position of the center line of the scribe line S in the above configuration. The algorithm will be described in more detail with reference to FIG. In the following description, the direction parallel to the horizontal scribe line S shown in FIG. 2 will be referred to as the X-axis direction, and the direction parallel to the vertical scribe line S will be referred to as the Y-axis direction.

First, the operation of the wafer fixing table 13 is controlled so that the wafer fixing table 13 is moved to the CCD camera 3.
The position of the semiconductor wafer 11 fixed to the wafer fixing table 13 to be imaged is arranged immediately below the CCD camera 3 (step 100). Then, image the imaging area,
The obtained image information is taken in through the A / D converter 5,
Store in memory of computer 2 (step 10)
1). The dotted line in FIG. 2 shows an example of the image pickup area of the semiconductor wafer 11, but the image pickup area does not have to be divided into nine sections as in this figure, and can be variously changed depending on the resolution of the CCD camera 3.

Next, in step 102, the input image information is corrected so as to match the X-axis direction and the Y-axis direction in FIG. 2, and then in step 103, a density histogram is created from the density level of each pixel. To do. In step 104, the suitability of the created grayscale histogram is judged. For example, as shown in (a) of FIG. 4, when the peaks and valleys of the grayscale histogram do not appear clearly, it is not suitable for the subsequent processing, so the process proceeds to step 105 and the dynamic range is adjusted. Then, steps 101 to 104 are repeated again.

On the other hand, if a grayscale histogram with good separability is created as shown in FIG.
Then, the gray level considered to correspond to the area of the scribe line S is selected.

Thereafter, with reference to the gray level selected in step 106, the information of the scribe line S is extracted from the gray level of each pixel of the image information stored in the memory by taking various conditions into consideration (step). 107). As a condition for extracting the scribe line information, pixels having the selected gray level are continuous in the X-axis direction or the Y-axis direction, and the continuous pixel group has a region orthogonal to each other. And so on.

Further, in order to improve the extraction accuracy of the scribe line information, the pattern matching method can be applied. That is, although the semiconductor wafer 11 is manufactured based on the design data, a template is formed in advance from the width information of the scribe line S in the design data, and the correlation between the template and the input image information is taken. , It is possible to facilitate the extraction of the scribe line information. In this case, the input image information is binarized,
It is effective to narrow down the extraction target.

Next, in step 108, the suitability of the extraction result in step 107 is judged, and if the result is negative, it is determined that the gray level selected in step 106 is incorrect, and another gray level is selected. (Step 10
9). Then, step 107 is executed again.

If the extraction result of the scribe line information is valid, the center line of the scribe line S is extracted using a technique such as a thinning process (step 110). Next, in step 111, pattern measurement is performed based on the image information stored in the memory to obtain the position of the center line of the scribe line S, and the information is stored in the memory.

The processing of one imaging area is completed as described above, but if there is an area to be processed, the imaging area is changed (steps 112 and 113), and steps 100 to 100 are executed.
Repeat 111. Then, when the processing of all the imaging regions is completed, the positional information of the center line of the collected scribe line S is output to the controller 20 (step 11).
4).

As described above, the controller 20 controls the rotation of the dicing blade 12, the vertical movement of the spindle head 15, and the horizontal movement of the wafer fixing table 13 based on the input position information to cut the semiconductor wafer 11. I do. Therefore, when the position information of the center line of the scribe line S is input from the computer 2 to the controller 20, the semiconductor wafer 11 is accurately cut along the center line of the scribe line S and divided into a plurality of chips 21. (See FIG. 2).

In the above embodiment, the information of the scribe line S itself is extracted and the position of the center line thereof is detected, but the center line of the scribe line S can be detected from other characteristic points. . For example, as shown in FIG. 5, which is an enlarged view of the semiconductor wafer 11, the fact that the bonding pads 23 of the device 22 such as an electronic device are formed in rows at positions separated from the scribe line S by a predetermined distance is used. It is also possible to detect the center line of the scribe line S. That is, when the pad row of the bonding pads 23 is detected and the pad rows facing each other at a relatively narrow interval are detected, the central position between the pad rows is the position on the center line of the scribe line S. In particular, since the bonding pad 23 is made of metal, the density level of image information is high, and the information of the bonding pad 23 can be easily extracted even by a very simple binarization process, and this method is effective. is there.

Further, as shown in FIG. 6, when the pattern 24 such as TEG is formed on the scribe line S, the pixel having the selected gray level is in the X axis direction or Y direction.
Scribe line S by the method of being continuous in the axial direction
Is difficult to detect. In this case, device 22
Although it is possible to detect the scribe line S by the above method using the information of the bonding pad 23, the scribe line S can also be detected by the following method.

First, when substantially identical feature points which are discontinuous but extend in the X-axis direction or the Y-axis direction are extracted from the image information, the search is continued in the direction in which the feature points extend. Then, even if there is a pattern 24 such as TEG in the middle, if the feature points exist beyond the set amount, the entire region where the feature points extend is recognized as the scribe line S. Since the ratio of the pattern 24 such as TEG to the area of the scribe line S can be known from the design data, the set amount can be easily calculated.

In the above embodiment, one gray scale histogram is formed from the gray level of all the pixels of the input image information, but for each pixel row continuous in the X-axis direction, and
A grayscale histogram is formed for each pixel row that is continuous in the Y-axis direction, and a scribe line S is created from the grayscale histogram.
Information can be extracted.

For example, since the scribe line S is a flat and uniform surface, the gray scale histogram of the pixel row for a certain scribe line S has a constant gray level width as shown in FIG. 7A. Draw a narrow unimodal waveform.
In addition to the scribe line S, as shown in FIG. 7B, a grayscale histogram having a plurality of peaks is obtained. Therefore, when the level difference between the darkest point and the darkest point in the grayscale histogram is defined as the dynamic range,
If there is a grayscale histogram having a dynamic range smaller than the set value, the pixel row forming the histogram is related to the scribe line S.

In this way, the information of the scribe line S can be extracted by individually judging the dynamic range of the grayscale histogram of each pixel column.

Furthermore, for each pixel row in the X-axis direction or the Y-axis direction, a histogram representing the position of each pixel on the horizontal axis and the density level of the pixel at that position is formed on the vertical axis, and the scribe line S is formed from the histogram. It is also possible to detect the information of. For example, the histogram of the pixel row for the scribe line S is as shown in FIG. 8A because the gray level of each pixel is almost constant. Further, since the gray level of the semiconductor device, the bonding pad, etc. is also included in the portion other than the scribe line S, the histogram is as shown in FIG. 8B. When Fourier distribution is performed by regarding these distributions as one-dimensional waveforms, only the extremely low frequency components in FIG. 8A are obtained. Therefore, the scribe line information can be extracted by performing a Fourier transform on the histogram of each pixel row and searching for a frequency component lower than the set value.

The present invention has been described above with reference to the preferred embodiments, but the present invention is not limited to the above-mentioned embodiments, and there are various modifications.

For example, in the configuration shown in FIG. 1, the computer 2 is connected to the controller 20 and the detection result is automatically input to the controller 20.
The detection result may be output from the computer 2 to a display device such as a printer or CRT, and the detection result may be manually input by the operator. In case of manual input, an input error may occur, but there is an advantage that a desired cutting line position can be selectively input.

The cutting line does not have to be the center line of the scribe line S, and may be another line. In such a case, since the characteristic points of the line are extracted by image processing, an image processing algorithm different from the above will be applied.

[0045]

As described above, according to the present invention, since the semiconductor wafer to be diced is directly imaged and image-processed, the position of the desired cutting line can be accurately detected. Therefore, since the semiconductor wafer can be accurately divided, the incidence of division defects is drastically reduced.

Further, since the image processing is automatically performed by a computer or the like, there is almost no labor required for detecting the position of the cutting line.

Further, since it is possible to directly input the detection result from the image processing means to the controller of the dicing device, it is possible to prevent an input error due to manual input. This is effective in the case of a semiconductor wafer including various sized devices such as an ASIC.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing a dicing device provided with a cutting line position detecting device according to the present invention.

FIG. 2 is a plan view showing a scribe line and an imaging region of a semiconductor wafer.

FIG. 3 is a flowchart showing an embodiment of a cutting line position detecting method according to the present invention.

4A and 4B are gray scale histograms obtained by image processing in the cutting line position detection method of FIG. 3, in which FIG. 4A is a diagram before dynamic range adjustment and FIG. 4B is a diagram after dynamic range adjustment.

FIG. 5 is an enlarged plan view of a semiconductor wafer.

FIG. 6 is an enlarged plan view of a semiconductor wafer having a pattern such as TEG formed on a scribe line.

7A is a grayscale histogram of a pixel row on a scribe line, and FIG. 7B is a grayscale histogram of a pixel row in a portion other than the scribe line.

8A and 8B are histograms of a position of each pixel on the horizontal axis and a pixel row indicating the density level of the pixel at the position on the vertical axis, where FIG. 8A is on a scribe line and FIG. 8B is a portion other than the scribe line. Is a histogram of.

[Explanation of symbols]

1 ... Cutting line position detection device, 2 ... Computer (image processing means), 3 ... CCD camera (imaging means), 5 ... A /
D converter, 10 ... Dicing device, 11 ... Semiconductor wafer, 12 ... Dicing blade, 13 ... Wafer fixing table, 15 ... Spindle head, 20 ... Controller, 21
… Chips, 22… Devices, 23… Bonding pads,
24 ... Patterns such as TEG.

Claims (8)

[Claims] 1. A cutting line position detecting method for detecting a position of a cutting line when dicing a semiconductor wafer, wherein a semiconductor wafer is imaged, image information of the semiconductor wafer is captured, and the image information is subjected to image processing to detect the cutting line. A method for detecting the position of a cutting line of a semiconductor wafer, characterized by detecting the position. 2. The method of detecting a cutting line position of a semiconductor wafer according to claim 1, wherein the cutting line is a scribe line formed between devices on the semiconductor wafer. 3. The method for detecting a cutting line position of a semiconductor wafer according to claim 2, wherein information on a scribe line is extracted from the image information, and a position of a center line of the scribe line is detected from the scribe line information. . 4. The semiconductor wafer according to claim 3, wherein the scribe line information is extracted by forming a template from known information about the width of the scribe line and taking a correlation between the template and the image information. Cutting line position detection method. 5. The area is recognized as a scribe line when an area having substantially the same characteristic points extracted from the image information exists in a predetermined direction exceeding a set amount. Item 5. A method of detecting a cutting line position of a semiconductor wafer according to item 3 or 4. 6. The semiconductor wafer according to claim 2, wherein information on a bonding pad of a device on the semiconductor wafer is extracted from the image information, and the position of the center line of the scribe line is detected from the bonding pad information. Cutting line position detection method. 7. The semiconductor wafer according to claim 6, wherein a template is formed from known information of the dimensions of the bonding pad, and the bonding pad information is extracted by taking a correlation between the template and the image information. Cutting line position detection method. 8. A cutting line position detecting device for detecting the position of a cutting line when dicing a semiconductor wafer, and an image pickup means for picking up an image of the semiconductor wafer and taking in image information of the semiconductor wafer; An image processing means for image-processing image information to detect the position of a cutting line.