WO2013163791A1

WO2013163791A1 - Apparatus and method for detecting position of wafer

Info

Publication number: WO2013163791A1
Application number: PCT/CN2012/074966
Authority: WO
Inventors: Jian Wang; Yu Zhao; Yufeng Huang; Fufa Chen; Hui Wang
Original assignee: Acm Research (Shanghai) Inc.
Priority date: 2012-05-02
Filing date: 2012-05-02
Publication date: 2013-11-07
Also published as: CN104396003A; KR20150005616A; CN104396003B

Abstract

An apparatus and method for detecting position of a wafer on a chuck are disclosed. The apparatus includes a camera (6) and an image processor (100) which includes a transforming unit (101), a comparing unit (103) and a determining unit (104). The method includes the following steps: taking an image of edge of the wafer and send image data to the image processor (S23); transforming the image data into image pixels and comparing the image pixels with reference pixels (S25'), and determining whether the wafer is in position on the chuck (S26).

Description

APPARATUS AND METHOD FOR DETECTING POSITION

OF WAFER

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention generally relates to a semiconductor device fabrication, and more particularly to an apparatus and method for detecting a position of a wafer held on a wafer chuck.

2. The Related Art

[0002] During a semiconductor device fabrication process, a wafer needs to be transferred into various chambers such as a deposition chamber, an etch chamber, a cleaning chamber and so on to undergo corresponding processes. In order to improve the process efficiency, robots are employed to transfer the wafer. The wafer is commonly disposed on a wafer chuck in the chambers to carry out the processes. Thus, whether the wafer is accurately positioned on a predetermined position of the wafer chuck will bring a big impact on the quality of the semiconductor device. For example, in the deposition process, if the wafer is not disposed on the center of the wafer chuck or the wafer is slant on the wafer chuck, the thickness of metal deposited on the wafer will not be uniform, which will increase the difficulty of the subsequent process or even damage the wafer. Therefore, the right position of the wafer on the wafer chuck is very important. So an apparatus and method for detecting the position of the wafer on the wafer chuck are desired.

[0003] Refer to US. patent publication No. 2005/0012938. An apparatus and method for detecting wafer position are disclosed that include a first sensor group and a second sensor group, both of which include at least one light emitter and at least one light receiver. When the apparatus is used for detecting wafer position, the apparatus determines whether a wafer position is normal by the relative position between the wafer and the sensors. Once the wafer position is abnormal and the time interval between the trigger of the first sensor group and the trigger of the second sensor group deviates the predetermined time interval, the apparatus reports the abnormal event to stop the process of the wafer.

[0004] However, although the apparatus described above can detect the wafer position, the structure of the apparatus is relatively complex. A simple structure of an apparatus and method for detecting the position of the wafer is strongly expected.

SUMMARY OF THE INVENTION

[0005] In accordance with one aspect of the present invention, the present invention provides an apparatus for detecting position of a wafer on a chuck. The apparatus includes a camera for taking an image of edge of the wafer on the chuck during rotation of the wafer to generate image data and an image processor. The image processor further includes a transforming unit for receiving the image data from the camera and transforming the received image data into image pixels, a comparing unit for comparing the image pixels transformed by the transforming unit with predefined reference pixels to obtain a comparison result; and a determining unit for determining whether the wafer is in position based on the comparison result.

[0006] In accordance with another aspect of the present invention, the present invention provides a method for detecting position of a wafer on a chuck. The method includes the following steps: taking an image of edge of the wafer during rotation of the wafer to generate image data; transforming the image data into image pixels; comparing the image pixels with predefined reference pixels to obtain a comparison result; and determining whether the wafer is in position based on the comparison result.

[0007] As described above, the present invention detects the position of the wafer on the chuck by means of the camera and the image processor. Relatively, the structure and the method of the present invention are simple.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present invention will be apparent to those skilled in the art by reading the following description of preferred embodiments thereof, with reference to the attached drawings, in which:

[0009] FIG. 1 is a schematic view illustrating an apparatus for detecting position of wafer in accordance with the present invention;

[0010] FIG. 2 is a block diagram illustrating the apparatus for detecting position of wafer of the present invention;

[0011] FIG. 3 is a schematic view illustrating an image of a wafer taken by a camera of the apparatus of the present invention;

[0012] FIG. 4 is a flowchart illustrating a first embodiment of obtaining reference pixels for detecting position of wafer;

[0013] FIG. 5 is a flowchart illustrating a second embodiment of obtaining reference pixels for detecting position of wafer;

[0014] FIG. 6 is a flowchart illustrating a first embodiment of detecting position of wafer of the present invention;

[0015] FIG. 7 illustrates an image taken by the camera (a subsection (a)), in contrast with another image taken by the camera configured for comparison (a subsection (b)); and

[0016] FIG. 8 is a flowchart illustrating a second embodiment of detecting position of wafer of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Referring to FIG. 1, an apparatus for detecting position of wafer in accordance with the present invention is illustrated. The apparatus includes a chamber 1, a support pedestal 2 disposed in the chamber 1, a chuck 3 disposed on the support pedestal 2. The chuck 3 has a plurality of pins 4. A wafer 5 is placed on the chuck 3 and is fixed by the pins 4 when the chuck 3 rotates. A camera 6 is disposed at a corner of the chamber 1 and above the wafer 5 for taking an image of edge of the wafer 5 on the chuck 3 during rotation of the wafer 5 to generate image data. A portion of chamber wall opposite to the camera 6 is made of semi-transparent material. A light emitter 7 is disposed at outside of the portion of chamber wall for lightening inside of the chamber 1.

[0018] Referring to FIG. 2, the apparatus for detecting position of wafer further includes an image processor 100 for processing the image data from the camera 6. The image processor 100 includes a transforming unit 101 for receiving the image data from the camera 6 and transforming the image data into image pixels, a storage unit 102 for storing predefined reference pixels, a comparing unit 103 for comparing the image pixels transformed by the transforming unit 101 with the predefined reference pixels stored in the storage unit 102 to obtain a comparison result, and a determining unit 104 for determining whether the wafer 5 is in position on the chuck 3 based on the comparison result. [0019] Referring to FIG. 3 and FIG. 4, a first embodiment of obtaining the reference pixels for detecting position of wafer is introduced. The wafer 5 used as a reference wafer is manually placed at the center of the chuck 3, and the wafer 5 is confirmed to be in position on the chuck 3 (Step Sl l). Then rotate the wafer 5 at a speed of 50rpm (Step S12). The speed is adjustable according to the process requirements. The camera 6 takes an image of edge of the wafer 5 to generate image data and sends the image data to the image processor 100 (Step SI 3). Set a rectangular marquee to select a proper edge of the wafer 5 in the field of the image as shown in FIG. 3 (Step SI 4). Typically, the marquee length is 200 pixels and the marquee width is 50 pixels. The transforming unit 101 of the image processor 100 transforms the selected edge into a plurality of pixels such as pixel 20, 19, 14, ... as shown in FIG. 7 (b). The current position of the wafer 5 on the chuck 3 is defined as a reference position and the pixels representing the selected edge are defined as the reference pixels, the reference position and the reference pixels are stored in the storage unit 102 of the image processor 100 (Step S15).

[0020] Referring to FIG. 5, a second embodiment of obtaining the reference pixels for detecting position of wafer is introduced. The wafer 5 used as a reference wafer is manually placed at the center of the chuck 3, and the wafer 5 is confirmed to be in position on the chuck 3 (Step Sl l). Then rotate the wafer 5 at a speed of 50rpm (Step S12). The speed is adjustable according to the process requirements. The camera 6 takes an image of edge of the wafer 5 to generate image data and sends the image data to the image processor 100 (Step SI 3). The transforming unit 101 of the image processor 100 receives the image date and transforms the image date into a plurality of pixels which are defined as the reference pixels stored in the storage unit 102 of the image processor 100 (Step SI 5'). The reference pixels are illustrated in Fig 7(b), such as pixel 20, pixel 19, ... , pixel 4, ...

[0021] Please refer to FIGS. 6-7. Corresponding to the first embodiment of obtaining the reference pixels, a first embodiment of detecting position of wafer is introduced. After obtaining the reference pixels, the wafer 5 is taken out of the chamber 1 and another wafer 5 is put on the chuck 3 by a robot hand (Step S21). Rotate the wafer 5 at the speed of 50rpm (Step S22). The camera 6 takes an image of edge of the wafer 5 to generate image data and sends the image data to the image processor 100 (Step S23). Set the same rectangular marquee as in Step S14 to select the same area edge of the wafer 5 in the field of the image (Step S24). The transforming unit 101 of the image processor 100 transforms the selected edge into a plurality of image pixels such as pixel 20, pixel 18, pixel 15, ... as shown in FIG. 7 (a). The comparing unit 103 of the image processor 100 respectively compares each image pixel of selected edge of the wafer 5 at the current position with the stored corresponding reference pixel at the reference position and then calculates the total error and the average error between them (Step S25). The determining unit 104 of the image processor 100 determines whether the wafer 5 is in position on the chuck 3 based on the calculation result (Step S26). The computational formulas of the total error and the average error are described as follow:

Total error=∑ abs(each current pixel data -each corresponding reference pixel data)

Average error=Total error / (marquee length χ marquee width)

[0022] The average error is defined as e_c. If e_c is less than a set value, it indicates that the wafer 5 is in position on the chuck 3 and the wafer 5 can be processed (Step S27). If e_c is greater than or equal to the set value, it indicates that the wafer 5 is not in position on the chuck 3 and the wafer 5 cannot be processed (Step S28).

[0023] Please refer to FIG. 8. Corresponding to the second embodiment of obtaining the reference pixels, a second embodiment of detecting position of wafer is introduced. After obtaining the reference pixels, the wafer 5 is taken out of the chamber 1 and another wafer 5 is put on the chuck 3 by a robot hand (Step S21). Rotate the wafer 5 at the speed of 50rpm (Step S22). The camera 6 takes an image of edge of the wafer 5 to generate image data and sends the image data to the image processor 100 (Step S23). The transforming unit 101 of the image processor 100 receives the image data and transforms the image data into a plurality of image pixels. The comparing unit 103 of the image processor 100 respectively compares each image pixel of edge of the wafer 5 at the current position with the stored corresponding reference pixel to obtain a comparing result (Step S25'). The determining unit 104 of the image processor 100 determines whether the wafer 5 is in position on the chuck 3 based on the comparing result (Step S26). If the comparing result e_c is less than a set value, it indicates that the wafer 5 is in position on the chuck 3 and the wafer 5 can be processed (Step S27). If the comparing result e_c is greater than or equal to the set value, it indicates that the wafer 5 is not in position on the chuck 3 and the wafer 5 cannot be processed (Step S28).

[0024] As described above, the present invention detects the position of the wafer 5 on the chuck 3 by means of the camera 6 and the image processor 100. Relatively, the structure and the method of the present invention are simple.

[0025] The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. Such modifications and variations that may be apparent to those skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.

Claims

WHAT IS CLAIMED IS :

1. An apparatus for detecting position of a wafer on a chuck, comprising: a camera for taking an image of edge of the wafer on the chuck during rotation of the wafer to generate image data;

a transforming unit for receiving the image data from the camera and transforming the received image data into image pixels;

a comparing unit for comparing the image pixels transformed by the transforming unit with predefined reference pixels to obtain a comparison result; and

a determining unit for determining whether the wafer is in position based on the comparison result.

2. The apparatus as claimed in claim 1, wherein the rotation of the wafer is at a specific speed, and the reference pixels are obtained at the time that a reference wafer that is in position rotates at the specific speed.

3. The apparatus as claimed in claim 1 , wherein the chuck has a plurality of pins for fixing the wafer on the chuck when the chuck rotates.

4. The apparatus as claimed in claim 1, wherein the chuck is disposed in a chamber, a portion of chamber wall opposite to the camera is made of semi-transparent material.

5. The apparatus as claimed in claim 4, further comprising a light emitter disposed at outside of the portion of chamber wall for lightening inside of the chamber.

6. A method for detecting position of a wafer on a chuck, comprising:

taking an image of edge of the wafer during rotation of the wafer to generate image data;

transforming the image data into image pixels;

comparing the image pixels with predefined reference pixels to obtain a comparison result; and determining whether the wafer is in position based on the comparison result.

7. The method as claimed in claim 6, wherein the rotation of the wafer is at a specific speed, and the reference pixels are obtained at the time that a reference wafer that is in position rotates at the specific speed.

8. The method as claimed in claim 6, wherein the step of comparing the image pixels with predefined reference pixels to obtain a comparison result further comprises: calculating average error between the image pixels and the predefined reference pixels.

9. The method as claimed in claim 8, wherein the step of determining whether the wafer is in position based on the comparison result further comprises: if the average error is less than a predefined set value, then determining that the wafer is in position; and if the average error is greater than or equal to the predefined set value, then determining that the wafer is not in position.