JP3076178B2 - Wafer positioning direction calculator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer positioning direction calculating device, and more particularly to a wafer positioning direction calculating device suitable for non-contact measurement of the position of an orientation flat portion.

[0002]

2. Description of the Related Art A semiconductor wafer is obtained by diagonally slicing a rod-like single crystal of silicon or the like into a predetermined thickness. Further, the peripheral edge is polished to make the shape of the cut single crystal plate a perfect circle, and a linear cut portion (notch portion), ie, an orientation flat portion ( (Hereinafter, abbreviated as “ori-flat”) is usually provided. This orientation flat is
It becomes a straight line connecting two points on the circumference.
147444).

[0003] A plurality of polished wafers are stored in a magazine, and the orientation of the orientation flat is random in the stored state, but when the wafer is taken out and transferred to the next step, the wafer is removed. Since the directions need to be aligned,
It is important to position the wafer in the orientation flat direction.

The initial positioning method in the orientation flat direction was a contact method in which the orientation flat portion was mechanically probed, and thus had problems such as scratching the wafer and abrasion of the contact portion.

[0005] Therefore, various methods have been proposed for positioning in the orientation flat direction without contact.

For example, in Japanese Patent Application Laid-Open No. 63-196057, a photosensor for detecting the position of the wafer on the xyθ table in the xy directions and both ends of the orientation flat is provided, and a moving means and a rotating means for the xy directions are provided. In addition, a technique for performing high-speed and high-accuracy positioning is described.

In Japanese Patent Application Laid-Open No. 63-184351, an image of a wafer is temporarily stored in a memory, and a rotational operation or a parallel shift operation of the image is performed in the memory. Detection is described (particularly, see FIG. 2). Further, in Japanese Patent Application Laid-Open No. 63-184351, it is naturally assumed that a wafer portion and a background portion can be separated by a binary image.

[0008]

SUMMARY OF THE INVENTION However,
In the conventional example described in Japanese Patent Application Laid-Open No. 63-196057, since the photosensor is used for detecting the position of the xyθ table, there is a problem in the mounting accuracy and the detection accuracy of the photosensor, and the external environment such as temperature is disadvantageous. There is a problem that the detection characteristics change depending on the conditions.

Further, in the conventional example described in Japanese Patent Application Laid-Open No. 63-184351, the point that measurement can be performed in a non-contact manner is improved. Since processing such as image rotation is performed, such image processing for all pixels requires enormous computations, and there is a disadvantage that it is not possible to detect a wafer position shift or a rotational shift at a high speed. there were.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a wafer positioning direction calculating apparatus which can solve the above-mentioned disadvantages of the prior art, and in particular, can position a wafer by high precision and quick processing.

[0011]

Therefore, in the present invention, a direct
For circular wafers with cutout lines
One of the pixels forming the outline of the outer periphery of the wafer from the value image
Tracking start point determination means (step S:
20) and determined by the tracking start point determining means.
Sequentially to the pixels of the wafer outline adjacent to the tracking start point
Attention is paid and the image is determined from the connection status between the pixel of interest and neighboring pixels.
The unit direction code (for example, 0 to 7 shown in FIG. 3, FIG. 4)
Direction code calculating means for obtaining the code of 0 to 16 shown in FIG.
And (Step S22), depending on the direction code computation means
Pixels of the wafer outline portion of the calculated direction code
Histogram generation means for creating a body histogram
Steps S23 and S26) and the histogram generating means
(For example, in the histogram created in S26).
Peak detecting means (Step S3) for detecting the
And the peak data detected by this peak detection means.
The direction of the peak based on the notch portion
The direction of the notch and the direction of the notch
And the orientation flat positioning means (step S4) for calculating
Equipped with a configuration. This aims to achieve the above-mentioned object.

[0012]

The direction code calculation means calculates the pixel of the wafer contour part.
Each time, a direction code that is the traveling direction of the pixel is obtained.
Further, the histogram generating means is configured to perform the
Is calculated for each pixel. Through
Normally, when such a direction code is calculated for a circle,
No stogram peak appears. On the other hand, have a notch
The histogram of this direction code for the circle
And the straight line part travels in the same direction,
There are many pixels to go, so according to the number of pixels in the straight line part
A histogram peak appears.

Further, the peak detecting means includes a histogram
Detect the ram peak. This peak is
The direction is the direction of the straight line of the pixel forming the straight line. Soshi
The orientation flat positioning means
Is calculated from the direction of.

(Delete)

(Delete)

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

In the embodiment shown in FIG. 1, a histogram 1 generating means 1 for generating a histogram for each trace direction based on a target binary image, and an appropriate distance by using the histogram generated by the histogram 1 generating means 1 Histogram 2 generating means 2 for generating a histogram for each direction between distant pixels, and peak detecting means 3 for detecting a peak in the histogram generated by the histogram 2 generating means 2
And an orientation flat positioning means 4 for calculating a directional inclination of the orientation flat based on the peak data detected by the peak detection means 3.

Next, the operation of this embodiment will be described.
In this embodiment, a histogram is generated for each direction between pixels located at an appropriate distance apart from each other at an appropriate norm while using a chain code or performing an outer tracing on a wafer, and a peak thereof is detected to determine an orientation flat. Is calculated.

(1). Hereinafter, this will be described in detail. First, an operation process for calculating the directional inclination of the orientation flat from the outer peripheral trace of the wafer will be described with reference to the flowchart of FIG.

[0020] The histogram 1 generating means 1 determines a tracking start point by raster scan for the target binary image (step 20 in FIG. 2 , a tracking start point determination step).
Stage ). Here, as shown in FIG. 5 as an example, the upper left position “1” is set as the tracking start point. This tracking start point is one point of the wafer contour.

In the trace, a combination of direction codes in pixel units is considered. In other words, even if the run-length code is traced, the direction code for each pixel is considered at the same time.

As shown in FIG. 5, the order of the outer peripheral trace using the run-length code is “1” → “2”. However, considering the pixel unit, as shown in FIG.
Proceed in the order of “B” → “C”.

Therefore, the pixel of interest is first set to "B".

[0024] The histogram 1 generating means 1 checks the connection status with the vicinity of the pixel of interest (step 21 in FIG. 2),
A direction code is obtained from the moving direction of the pixel of interest (step 22 in FIG. 2 , direction code calculating means ).

Here, as shown in FIG. 3, the direction code is obtained based on an eight-way code table. That is, the direction code when the moving direction is right is “0”, the upper right is “1”, the upper right is “2”, the upper left is “3”, the left upper is “4”, the lower left is “4”. The case is defined as “5”, the lower case as “6”, and the lower right case as “7”.

As shown in FIG. 6, the pixel of interest is "B"
In the case of, the 8-way code of “A” → “B” is “5”,
Since the eight-direction code of “B” → “C” is “4”, the direction code of the pixel “B” is (front, rear) = (5, 4)
Indicated by

[0027] The histogram 1 generating means 1 generates a direction-specific histogram (hereinafter abbreviated as “histogram 1”) using an eight-direction code based on a combination of direction codes of the target pixel before and after movement.

Therefore, in order to make the direction code before movement and the direction code after movement for the pixel of interest one-dimensional,
It is converted into a code number using the following equation (1). The converted code number is 64 from 0 to 63 as shown in FIG.
It has one of the types (= 8 × 8). The frequency corresponding to each code number is represented by hist [code number].

Code number = “backward direction code” + 8 × “previous direction code” (1)

As for the pixel "B" in FIG. 6, the "previous direction code" is "5" as determined by the above processing.
Since the “later direction code” is “4”, the code number is calculated as “44” by the equation (1). Therefore,
The frequency of the code number 44 in the histogram 1, that is, the value of hist [44] is counted up.

[0031] The histogram 1 generating means 1 moves the pixel of interest (step 25 in FIG. 2) until the outer peripheral tracing is completed, and repeats the above processing to generate the histogram 1 as shown in FIG.

[0032] When the outer peripheral trace is completed (Step 24 in FIG. 2), the histogram 2 generating means 2 considers all the possibilities of moving from the pixel of interest twice and reaching the next two pixels, A histogram (hereinafter, abbreviated as “direction-specific histogram 2”) is generated (step 26 in FIG. 2, histogram generating means ).

Here, as shown in FIG. 4, when the coordinates of the pixel X of interest are (0, 0) as shown in FIG. The direction code is "0", the direction code when the coordinate after movement is (2, -1) is "1", and the direction code when the coordinate after movement is (2, -2) is "2". The direction code when the subsequent coordinate is (1, -2) is "3", the direction code when the moved coordinate is (0, -2) is "4", and the coordinate after the movement is (-1, -2). −
In the case of 2), the direction code is “5”, and the coordinates after the movement are (−).
When the direction code in the case of (2, -2) is "6", the direction code in the case where the coordinate after the movement is (-2, -1) is "7", and the coordinate after the movement is (-2, 0) Is "8", the direction code after the movement is (-2, 1) is "9", and the direction code after the movement is (-2, 2) is "10". The direction code when the coordinate after the movement is (−1, 2) is “11”, the direction code when the coordinate after the movement is (0, 2) is “12”, and the coordinate after the movement is (1, 2). ), The direction code is “13”, and the coordinates after movement are (2, 3).
The direction code in the case of 2) is defined as “14”. The frequency corresponding to each direction code is hist2 [direction code].
It shall be represented by

For example, as shown in FIG. 8, the coordinates (2, 2) are moved twice from the coordinates (0, 0) of the pixel of interest.
-1), that is, code "1" in the 16-way code
There are two types of patterns that arrive at the coordinates (1, 0) and the coordinates (1, -1). That is, it can be considered as a combination of the code “0” and the code “1” in the eight-way code.

Therefore, the histogram 2 of the 16-direction code
, The frequency of code “1”, ie, hist2
The value of [1] can be obtained using the following equation (2).

Hist2 [1] = hist [1] + hist [0] (2)

Similarly, for only one side of the orientation flat, the histogram 1 of the combination of the eight-direction codes before and after the movement is obtained.
Then, as shown in FIG. 9, a histogram 2 of a combination of 16-directional codes is created.

[0038] The peak detecting means 3 detects a peak of the histogram 2 generated for only one side of the orientation flat.

[0039] The orientation flat positioning means 4 obtains vector coordinates (x, y) of a side whose direction is to be obtained based on the peak of the histogram 2.

For example, as shown in FIG. 9, it is assumed that peaks are detected at frequencies of code "6", code "7" and code "8" in the histogram 2 generated for only one side of the orientation flat. .

The direction vectors of code "6", code "7", and code "8" in the 16-way code are a, b, c
Then, from the definition of the 16-way code, the following can be written.

A = (− 2, −2)

B = (− 2, −1)

C = (− 2,0)

The frequencies of the code “6”, the code “7”, and the code “8” in the histogram 2 generated for only one side of the orientation flat are represented by “hist2”.
If [6], hist2 [7], and hist2 [8] are described, the vector coordinates (x, y) of one side of the orientation flat can be obtained from the following equation (3).

(X, y) = a × hist2 [6] + b ×
hist2 [7]

+ C × hist 2 [8] (3)

[0048] Further, the orientation flat positioning means 4 calculates the direction angle θ of the orientation flat vector from the vector coordinates of one side of the orientation flat (step 27 in FIG. 2).

Here, assuming that the vector coordinate of one side of the orientation flat is (x, y), the direction angle θ can be obtained from the following equation (4).

Θ = tan ⁻¹ (y / x) (4)

(2). Next, the operation of calculating the directional inclination of the orientation flat from the chain code will be described with reference to the flowchart of FIG.

[0052] The histogram 1 generating means 1 generates a chain code (Step 10 in FIG. 10).

[0053] The histogram 1 generating means 1 creates the histogram 1 in the same manner as described above (step 11 in FIG. 10).

[0054] The histogram 2 generating means 2 uses the histogram 1 generated by the histogram 1 generating means 1,
The histogram 2 is generated in the same manner as described above (Step 11 in FIG. 10).

[0055] The peak detecting means 3 calculates the histogram 2
A peak point is detected from the histogram 2 created by the generation means 2 (step 12 in FIG. 10).

[0056] The orientation flat positioning means 4 determines the vector coordinates (x, y) of the side for which the direction is to be determined based on the peak of the histogram 2 in the same manner as described above, and further calculates the orientation angle θ of the orientation flat vector, thereby obtaining the orientation flat. (Step 1 in FIG. 10)
3).

As described above, by using a chain code or by directly tracing the outer periphery, a histogram is generated for each direction between pixels separated by an appropriate distance from an appropriate distance to an orientation flat, and peaks are detected to detect orientation flats. Is calculated, the direction of an object having a notch of a disk-like object such as a wafer can be obtained in a non-contact manner at high speed with high accuracy.

[0058]

Since the present invention is constructed and functions as described above, according to the first aspect of the present invention, the present invention is based on a binary image for a circular wafer having a straight cutout portion. When the histogram of the direction code in units of the pixels of the line forming the wafer contour is obtained, the value of the histogram in the direction of the straight line portion that becomes the notch of the wafer contour becomes large, so that the wafer contour is tracked. The portion where the histogram of the line direction is large is the orientation flat portion, that is, the direction of the straight line of the orientation flat portion can be measured based on the peak of the histogram of the direction code. , The inclination of the wafer can be measured. According to the second aspect of the present invention, a histogram of a direction code is obtained by using a chain code starting from one point on the outer periphery of the wafer or by tracing the outer periphery of the wafer portion to trace the contour of the wafer in the target image. For,
These measurements can be performed by a simple image processing such as a chain code or an outer peripheral trace and a histogram calculation processing with a small number of elements. It is possible to provide an unprecedented and excellent wafer positioning direction calculation device that can calculate the directional inclination of the orientation flat.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart for explaining an operation in a case where outer peripheral tracing is performed in the embodiment of FIG. 1;

FIG. 3 is an eight-way code table for explaining the operation of the histogram 1 generating means of FIG. 1;

FIG. 4 is a 16-way code table for explaining the operation of the histogram 2 generating means of FIG. 1;

FIG. 5 is an explanatory diagram for explaining outer peripheral tracing using a run-length code.

FIG. 6 is an explanatory diagram for explaining a moving direction in the example of FIG. 5;

FIG. 7 is an explanatory diagram showing an example of a histogram 1 created by a histogram 1 generating means in FIG. 1;

FIG. 8 is an explanatory diagram for explaining the operation of the histogram 2 generating means of FIG. 1;

FIG. 9 is an explanatory diagram showing an example of a histogram 2 created by the histogram 2 generating means of FIG. 1;

FIG. 10 is a flowchart for explaining an operation when a chain code is used in the embodiment of FIG. 1;

[Explanation of symbols]

 Reference Signs List 1 histogram 1 generating means 2 histogram 2 generating means 3 peak detecting means 4 orientation flat positioning means

Claims (2)

(57) [Claims] 1. A tracking start point is determined from a binary image of a circular wafer having a straight cutout portion with a pixel forming an outline of the outer periphery of the wafer as a tracking start point.
Means and, in pixel units from the connection status with the wafer outline of the paying attention pixel and the neighboring pixel co When sequentially focused to a pixel adjacent to add <br/> trace starting point determined by the tracking start point determination means A direction code calculating means for obtaining a direction code;
Before the direction code calculated by the direction code calculation means
A histogram generating means for generating a histogram of the entire pixels of the serial wafer contour portion, provided with a peak detecting means for detecting a peak direction in the histogram created by the histogram generation means, the peak data detected by the peak detecting means An orientation flat positioning means for calculating the direction of the peak based on the linear direction of the cutout portion based on the orientation and calculating a directional inclination of the cutout portion. 2. A histogram calculating the histogram generation means, a histogram of a combination of two direction codes before and after the movement based on the eight directions direction code before and after the movement of the target pixel by the use or the outer peripheral tracing the chain code A generation unit for generating a histogram in a direction from the pixel of interest to two adjacent pixels based on the histogram data generated by the histogram generation unit; according to claim 1, further comprising a means for calculating a direction angle of the vector coordinates and the vector of the cutout side min based on the peak of the histogram of the detected notch side min by said peak detecting means Wafer positioning direction calculation device.