JPH07169812A - Wafer rotation angle calculation method - Google Patents

Abstract

(57) [Summary] [Object] To provide a method capable of accurately calculating a rotation angle of a wafer even when a semiconductor element becomes small. [Structure] First, an image is captured so that a boundary line 11 to be subjected to position detection is projected in a fixed direction in a rectangular window 2, and scanning lines in a direction substantially orthogonal to the direction of the boundary line 11 are spaced at regular intervals. 3 or more are set to detect the position of the boundary line 11 in each scanning line direction, and the average value is obtained by excluding the maximum value or the minimum value among the respective detection positions on the scanning line. Calculate the position of line 11. It is also a method for calculating the rotation angle in which the interval between the scanning lines is smaller than half the pitch of the semiconductor elements 10 and is a value other than an integer fraction of the pitch of the semiconductor elements 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calculating a rotation angle of a wafer on which a plurality of semiconductor elements are formed with respect to a reference position.

[0002]

2. Description of the Related Art In a die-bonding process in manufacturing a semiconductor device, a chip-shaped semiconductor element is taken out from a wafer divided into a plurality of semiconductor elements, and then the semiconductor element is mounted on a predetermined base. The die bonder used at this time mounts the divided wafers on a table, calculates the rotational angle deviation of the wafer, corrects the angular deviation, and then takes out the semiconductor element.

FIGS. 6A and 6B are views for explaining a conventional method for calculating a rotation angle of a wafer. FIG. 6A shows an image capture and FIG. 6B shows a window in signal processing of the captured image. In order to calculate the rotation angle of the wafer 1, images are captured in the capture area A and the capture area B, the position of the boundary line 11 on each window 2 is detected from the image of the boundary line 11 of the semiconductor element 10, The rotation angle of the wafer 1 is calculated based on the detection result.

In order to detect the position of the boundary line 11 from the captured image, first, scanning lines (for example, .about.) Are set in the window 2 at regular intervals, and the level of the video signal on each scanning line is set by using the image processing device. The position of each boundary line 11 is detected based on the change. In order to detect the boundary line 11 from the level change of the video signal, for example, the magnitude of the signal in each pixel is sequentially examined from the right end to the left end of the window 2, and the boundary line 11 is used when the signal level exceeds a predetermined level. Judge that there is. Then, by averaging the positions of the boundary lines 11 detected on the respective scanning lines (-), the positions of the boundary lines 11 on the window 2 (coordinate values with respect to the reference position)
Is calculated. The position of the boundary line 11 is calculated in the loading area A and the loading area B of the wafer 1, and the rotation angle of the wafer 1 is calculated using these coordinate values. The die bonding apparatus calculates such a rotation angle deviation of the wafer 1 and moves the table so as to correct this angle deviation.

[0005]

However, such a wafer rotation angle calculation method has the following problems. That is, when the size of the semiconductor element formed on the wafer becomes small, the images of the plurality of semiconductor elements 10 are displayed in the window 2 as shown in FIG. 6B. Therefore, the image of the boundary line 11a other than the boundary line 11 to be detected is also captured, and for example, in the scanning line, the boundary to be detected is detected when scanning is performed from the right end to the left end of the window 2. Before detecting the line 11, another boundary line 11a is detected. Further, even if there is signal noise on the scanning line, the location other than the boundary line 11 will be detected.

If such an erroneous detection occurs, a large error will occur even if the average is obtained from the positions of the boundary lines 11 detected on each scanning line, and the position of the boundary lines 11 on the window 2 will be inaccurate. If the position of the boundary line 11 on the window 2 becomes inaccurate, it becomes difficult to accurately calculate the rotation angle of the wafer 1. In particular, the smaller the semiconductor element 10 is, the more other boundary lines 11a are projected in the window 2, and the scan lines and other boundary lines 11a are often overlapped with each other. The calculated value of is inaccurate. Therefore, it is an object of the present invention to provide a method capable of accurately calculating the rotation angle of a wafer even when the size of the semiconductor device is reduced.

[0007]

The present invention is a method for calculating a rotation angle of a wafer, which has been made to solve such a problem. That is, according to this method, the image of the boundary line of the semiconductor element is captured from above the wafer on which a plurality of semiconductor elements are formed at two positions in the wafer, and the level of the image signal on the scanning line set in the rectangular window of each image is captured. This is a method of detecting the position of the boundary line on the rectangular window based on the change, and calculating the rotation angle of the wafer based on each detection result.First, the boundary line for position detection is within the rectangular window. The image of the boundary line is captured so that it is projected in a certain direction, and three or more scanning lines in a direction substantially orthogonal to the direction of the boundary line are set at regular intervals to set the position of the boundary line in each scanning line direction. The position of the boundary line on the rectangular window is calculated by detecting and obtaining the average value by removing the maximum value or the minimum value from the respective detection positions on the scanning line. Further, it is also a method for calculating the rotation angle of the wafer in which the interval between the scanning lines is smaller than half the pitch of the plurality of semiconductor elements arranged in the direction of the boundary line of the detection target, and is set to a value other than an integer fraction of this pitch. .

[0008]

By setting three or more scanning lines on the rectangular window in the captured image and obtaining the average value by removing the maximum value or the minimum value among the detection positions of the boundary lines on these scanning lines, each detection position is obtained. The singular points can be removed from the inside, and an accurate average value can be obtained. Further, as the interval between the respective scanning lines to be set, it is smaller than half the pitch of the plurality of semiconductor elements arranged in the direction of the boundary line to be detected,
Moreover, by setting the value to a value other than an integer fraction of the pitch, the number of scanning lines that overlap other boundary lines is reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wafer rotation angle calculating method of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram (1) for explaining the rotation angle calculation method of the present invention, FIG. 2 is a diagram (2) for explaining the rotation angle calculation method of the present invention, and FIG. 3 is a diagram for explaining a wafer rotation angle calculation system. It is a figure.

First, before explaining the wafer rotation angle calculation method of the present invention, a wafer rotation angle calculation system will be described. As shown in FIG. 3, this system includes a table 3 on which a wafer 1 is placed, a CCD camera 4 that captures an image of the wafer 1, an image processing device 5 that performs predetermined signal processing on the captured image, and a host controller. 6,
It is composed of a manufacturing apparatus main body 7 and a data processing unit 8.

The system is equipped with, for example, a die bonder as the manufacturing apparatus main body 7, reads information of the wafer 1 or the like into the data processing unit 8 via a network or a floppy disk, and in accordance with an instruction from the host controller 6, the wafer 1 The calculation of the rotation angle with respect to the reference position, the angle correction, and the pickup of the semiconductor element based on various data are performed.

In the method of calculating the rotation angle of the wafer 1, first, an image of the boundary line 11 of the semiconductor element 10 (see FIG. 1A) formed on the wafer 1 using the CCD camera 4 is imaged in the wafer 1. The boundary line 1 is captured in a window 2 (see FIG. 1B) on the signal processing of the respective images captured at two points.
The position of 1 is detected, and the rotation angle of the wafer 1 with respect to the reference position is calculated based on the detection result using, for example, a trigonometric function. The invention is particularly applicable to a borderline 1 on a window 2.
The method of detecting the position of 1 is characterized. Hereinafter, a method of calculating the rotation angle of the wafer 1 will be sequentially described.

First, as shown in FIG. 1A, an image of the boundary line 11 of the semiconductor element 10 formed on the wafer 1 is captured. The capturing positions are a capturing region A and a capturing region B in the figure, and are positions where the boundary line 11 of the semiconductor element 10 is projected on the window 2 in a certain direction (for example, the vertical direction). When the manufacturing apparatus body 7 shown in FIG. 3 is a die bonding apparatus, the cutting line (dicing line) of the wafer 1 becomes the boundary line 11 to be detected.

As shown in FIG. 1B, an image of a boundary line 11 to be detected and an image of another boundary line 11a are displayed on the window 2 of the captured image. When the wafer 1 is rotated with respect to the reference position, the boundary line 11 is projected in a state of being inclined with respect to the vertical and horizontal directions of the window 2.
That is, the reference position of the wafer 1 and the CCD shown in FIG.
The relative position with respect to the camera 4 is accurately aligned, and the length and width of the rectangular window 2 coincides with the reference position.

Next, in each of the windows 2 in the capture area A and the capture area B, the position of the boundary line 11 on the window 2 is detected. When detecting the position of the boundary line 11 on the window 2, three or more scanning lines in a direction substantially orthogonal to the direction of the projected boundary line 11 are set at regular intervals. As shown in FIG. 1B, for example, when the boundary line 11 is projected in the vertical direction of the window 2, the scanning line for scanning the signal in the horizontal direction, that is, the horizontal direction is set. In this embodiment, a case will be described as an example where nine scanning lines (-) are set at regular intervals.

Next, the level change of the video signal on each scanning line (-) is examined. That is, the captured image has been transferred to the image processing device 5 shown in FIG. 3, and a predetermined signal processing is performed to detect a position where the signal level exceeds a certain value. For example, the level change of the video signal is checked from the right end of the window 2 to the left end of the scanning line, and a in the drawing is set as the detection position. Similarly, the level change of the video signal is checked for each of the scanning lines (-), and b-i in the drawing are set as the detection positions.

It is judged that these detection positions are the positions of the boundary line 11. Here, the scanning line is positioned before the boundary line 11 to be detected (closer to the right end of the window 2) than the other boundary line 11a. The position is detected (see f in the figure),
Only this value is unique. Therefore, the coordinate values (coordinate values in the scanning line direction) of the detection positions a to i on each scanning line on the window 2 are compared with each other, and the average value thereof is obtained except for the maximum value or the minimum value. For example, when the lower left of the window 2 is the origin, the average value is calculated using the values of a to e and g to i, except for the value of f having the largest coordinate value in the scanning line direction among the detection positions a to i. Ask for. This makes it possible to obtain an average value with a small error. Further, when a peculiar value is detected due to signal noise or the like on the scanning line, that value is excluded, and in this case as well, an average value with a small error can be obtained.

This average value is set as the position of the boundary line 11 on the window 2. The position of the boundary line 11 on the window 2 is shown as x and y coordinate values with the obtained average value as the x coordinate and the vertical center value of the window 2 as the y coordinate. The position (coordinate value) of the boundary line 11 on the window 2 is obtained at two locations, the capture area A and the capture area B shown in FIG.

Next, a boundary line 1 on each window 2
The rotation angle of the wafer 1 with respect to the reference position is calculated based on the position 1. As shown in FIG. 2, the coordinate values of the detection position (x ₁ , y ₁ ) and the detection position (x ₂ , y ₂ ) of the boundary line 11 obtained in the capture area A and the capture area B are used to form a triangle. The rotation angle θ of the wafer 1 is obtained by a function. To obtain the rotation angle θ from these coordinate values, for example, θ = tan ⁻¹ (y ₁ −y ₂ ) / (x ₁
-X ₂ ) is used. As described above, the detection position (x ₁ , y ₁ ) of the boundary line 11 and the detection position (x ₂ ,
Since y ₂ ) is an average value with a small error in each window 2, an accurate rotation angle θ can be calculated by using these values.

Next, a specific example of the present invention will be described with reference to FIGS. As shown in FIG. 4A, the specific example described here is a semiconductor device 10 arranged in the direction of the boundary line 11.
Is 400 μm (that is, the pitch of the other boundary line 11a is also 400 μm), and the width of the other boundary line 11a is 20 μm.
This is the case of m. Further, when the wafer 1 is placed on the table 3 shown in FIG. 3, it is set by a predetermined positioning mechanism so as to be contained within a certain rotation angle, and this angle is set to 1 °.

FIG. 4B is a diagram showing the projected width of another boundary line 11a in such a case. That is, the wafer 1 is set to 1 with reference to the window center indicated by the arrow A in the figure.
When rotated, the end of the other boundary line 11 is lifted up by the distance d at the right end of the window indicated by the arrow a in the figure, which is 2200 μm away from the center of the window. This distance d is calculated by d = 2200 μm × tan1 ° and becomes about 38.4 μm. In addition, at this distance d, another boundary line 1
The projected width of the other boundary line 11a can be obtained by adding the width of 1a of 20 μm, which is about 60 μm.

That is, when the other boundary line 11a is inclined by 1 ° in the window 2 shown in FIG. 1B, the right end of the window 2 has a projection width of about 60 μm.
Further, the projection of the other boundary line 11a in the window 2 is repeated every 400 μm which is the pitch of the semiconductor element 10, and if the scanning line exists within the range of this projection width, the boundary line 11 to be detected is detected. Other border line 1 in front
1a will be detected. Therefore, the interval between the scanning lines is set so that the number of scanning lines existing within the range of the projection width is as small as possible.

FIG. 5 shows the window 2 in the example shown above.
It is a figure which shows typically the repetition of the projection in the right side of. That is, for example, 320 from the lower end of the window 2 to the upper end.
When it is 0 μm, a plurality of projection widths of 60 μm are arranged at a pitch of 400 μm (hatched portion in the figure). In order to reduce the number of scanning lines existing in such a range of the projection width as much as possible, for example, the value should be smaller than half of the pitch of the semiconductor element 10 and a value other than an integer fraction of the pitch. Set the scan line spacing.

That is, the pitch of the semiconductor elements 10 is 400
In the case of μm, the interval between the scanning lines is set to, for example, 170 μm, which is smaller than the half of 200 μm and is a value other than an integer fraction of 400 μm. The arrows shown in FIG. 5 indicate the positions of the scanning lines on the window 2 when the pitch is 170 μm. In this case, the first scanning line is set at a position of 160 μm from the lower end of the window 2, a position of 330 μm is set next, a position of 500 μm is set next, and a total of 18 lines are set up to a position of 3050 μm at a pitch of 170 μm.

Of these 18 scanning lines, two of 840 μm and 2030 μm from the lower end of the window 2 are within the projection width range. Therefore, the detection position of the boundary line 11 on these two scanning lines (see FIG. 1B)
The reference value is excluded, and the average value is obtained using the detection positions of the boundary line 11 on the other scanning lines. This allows
It becomes possible to obtain an accurate detection position of the boundary line 11 excluding a peculiar detection position.

The projection width and position on the window 2 as shown in FIG. 5 vary depending on the rotation angle of the wafer 1 and the mounting position, and in some cases, two or more (for example, about four) scanning lines. May exist within the range of the projection width. However, by setting the scanning lines at the pitches as described above, the positions where the other boundary lines 11a are detected are different among the scanning lines existing within the range of the projection width. Therefore, there is a case where the detection position of the other boundary line 11a has a value extremely close to the position of the boundary line 11 to be detected.

In the present invention, the average value is obtained by removing the maximum value or the minimum value among the detection positions on each scanning line, so that the position of the other boundary line 11a detected is the boundary line 11 to be detected. If it is very close to the position, it is not excluded, and only the other peculiar values are excluded. Therefore, even when the number of scanning lines existing within the range of the projection width is about four, if the average value excluding, for example, the maximum value or the next value is excluded, it is settled with a minute error. Therefore, there is no adverse effect on the calculation of the rotation angle of the wafer 1. It should be noted that, in any of the examples, an example is shown in which one of the maximum value and the minimum value is excluded when obtaining the average value, but the maximum value and the minimum value of the maximum value and the minimum value are taken into consideration in consideration of the balance when calculating the average value. Both may be excluded.

Further, in the wafer rotation angle calculation system shown in FIG. 3, the case where the manufacturing apparatus main body 7 is composed of a die bonding apparatus is shown, but the present invention is not limited to this, and the same applies to other semiconductor manufacturing apparatuses. Is. For example, in the semiconductor manufacturing equipment used before the die bonding process,
The rotation angle when the wafer 1 before division is placed on the table 3 is calculated, and in this case, the streets provided between the semiconductor elements 10 are regarded as the boundary lines 11. It should be detected.

[0029]

As described above, the method of calculating the rotation angle of a wafer according to the present invention has the following effects. In other words, the image of the boundary line other than the boundary line of the detection target is displayed in the window of the captured image, and even if the other boundary line overlaps the set scanning line, the accurate boundary line detection position is detected. Will be able to get. Further, even if an erroneous detection occurs due to a signal noise on the scanning line, an accurate boundary line detection position can be obtained. This makes it possible to accurately calculate the rotation angle of the wafer even if the semiconductor element becomes small and a plurality of semiconductor elements and other boundary lines are projected in the window.

[Brief description of drawings]

FIG. 1 is a diagram (No. 1) for explaining the present invention, in which (a) is an image capture and (b) is a window.

FIG. 2 is a diagram (No. 2) for explaining the present invention.

FIG. 3 is a diagram illustrating a wafer rotation angle calculation system.

FIG. 4 is a diagram (part 1) illustrating a specific example, in which (a) shows a pitch and a width, and (b) shows a projection width.

FIG. 5 is a diagram (part 2) explaining a specific example.

6A and 6B are views for explaining a conventional example, where FIG. 6A shows an image capture and FIG. 6B shows a window.

[Explanation of symbols]

 1 Wafer 2 Window 3 Table 4 CCD Camera 5 Image Processing Device 10 Semiconductor Element 11 Boundary Line 11a Other Boundary Line

Claims (2)

[Claims] 1. An image of a boundary line of the semiconductor element is displayed from above the wafer on which a plurality of semiconductor elements are formed.
The position of the boundary line on the rectangular window is detected based on the level change of the image signal on the scanning line set in the rectangular window of each image, and the rotation angle of the wafer is determined based on each detection result. In the calculation method, first, the image of the boundary line is captured so that the boundary line of the position detection is projected in a certain direction in the rectangular window, and the image of the boundary line in a direction substantially orthogonal to the direction of the boundary line is acquired. The scanning lines are set at three or more at regular intervals to detect the position of the boundary line in each scanning line direction, and the average value is obtained by excluding the maximum value or the minimum value among the respective detection positions on the scanning line. A method for calculating a rotation angle of a wafer, wherein the position of the boundary line on the rectangular window is calculated by the above. 2. The interval between the scanning lines is smaller than half the pitch of a plurality of semiconductor elements arranged in the direction of the boundary line,
The method for calculating a rotation angle of a wafer according to claim 1, wherein the pitch is a value other than an integer fraction of the pitch.