Wafer slip detection during CMP processing
A wafer-slip detection apparatus used in association with a chemical mechanical polishing (CMP) apparatus may include an imaging device that generates images corresponding to at least an area of a rotation table of the CMP apparatus, and an image processing unit coupled to the imaging device for receiving and processing the generated images during a CMP process. The image processing unit includes a reference image that is compared with each of the generated images for detecting a wafer presence within the at least an area of the rotation table, whereby the detected wafer presence is indicative of a wafer-slip event.
1. A method of detecting wafer-slip in a chemical mechanical polishing (CMP) apparatus, the method comprising:
generating a reference image corresponding to at least an area of a rotation table of a CMP apparatus during a CMP process, the reference image generated during a non-wafer-slip event;
generating an infrared signal, via an infrared laser, of the at least an area of the rotation table during the CMP process;
generating images including infrared signal images, via an imaging device, corresponding to the at least an area of the rotation table during the CMP process;
comparing, during the CMP process, each of the generated images with the generated reference image for determining an image characteristic difference;
determining a wafer-slip event based on the determined image characteristic difference; and
shutting down the CMP process in response to the wafer-slip event being determined thereby preventing a broken wafer event.
2. The method of claim 1 , further comprising:
generating an interrupt control signal when the wafer-slip event is determined.
3. The method of claim 2 , further comprising:
transmitting the generated interrupt control signal to the CMP apparatus for stopping the CMP process.
4. The method of claim 1 , wherein the non-wafer-slip event comprises an event corresponding to the wafer remaining within a retaining means during the CMP process.
5. The method of claim 4 , wherein the wafer-slip event comprises an event corresponding to the wafer being prematurely released from the retaining means during the CMP process.
6. The method of claim 1 , wherein the wafer-slip event comprises the wafer being imaged within the at least an area of the rotation table during the CMP process, the wafer being imaged based on the wafer being projected onto the at least an area of the rotation table during the CMP process.
7. The method of claim 6 , wherein the non-wafer-slip event comprises the wafer not being imaged within the at least an area of the rotation table during the CMP process.
8. The method of claim 1 , wherein the generating of the reference image comprises generating a reference grayscale image.
9. The method of claim 8 , wherein the generating the images comprises generating grayscale images.
10. The method of claim 9 , wherein the comparing, during the CMP process, of each of the generated images with the generated reference image comprises correlating each of the grayscale images and the reference grayscale image for determining the image characteristic difference.
11. The method of claim 10 , wherein the image characteristic difference comprises a correlation factor corresponding to the correlating.
12. The method of claim 11 , further comprising:
comparing the correlation factor with a predetermined threshold correlation factor, wherein upon the predetermined threshold correlation factor exceeding the correlation factor, the wafer-slip event is determined.
13. A computer program product for determining wafer-slip during a CMP process, the computer program product comprising a non-transitory computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising:
generating a reference image corresponding to at least an area of a rotation table of a CMP apparatus during a CMP process, the reference image generated during a non-wafer-slip event;
generating an infrared signal, via an infrared laser, of the at least an area of the rotation table during the CMP process;
generating images including infrared signal images, via an imaging device, corresponding to the at least an area of the rotation table during the CMP process;
comparing, during the CMP process, each of the generated images with the generated reference image for determining an image characteristic difference;
determining a wafer-slip event based on the determined image characteristic difference;
generating an interrupt control signal when the wafer-slip event is determined;
transmitting the generated interrupt control signal to the CMP apparatus for stopping the CMP process; and
shutting down the CMP process in response to the wafer-slip event being determined thereby preventing a broken wafer event.