Wafer slip detection during cmp processing

Abstract

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.

What is claimed is: 
     
         1 . A wafer-slip detection apparatus used in association with a chemical mechanical polishing (CMP) apparatus, the wafer-slip detection apparatus comprising:
 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 including 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,   wherein the detected wafer presence is indicative of a wafer-slip event.   
     
     
         2 . The apparatus of  claim 1 , wherein the imaging device comprises an infrared camera. 
     
     
         3 . The apparatus of  claim 1 , wherein the generated images comprise grayscale images. 
     
     
         4 . The apparatus of  claim 1 , wherein the image processing unit comprises:
 a memory unit that stores the reference image;   a correlation unit coupled to the memory unit, the correlation unit correlating each of the received images with the stored reference image to generate a correlation factor;   a determination unit coupled to the correlation unit, the determination unit comparing the correlation factor with a threshold correlation factor, wherein, based on the correlation factor falling below the threshold correlation factor, a wafer-slip indication signal is generated; and   a control signal generation unit coupled to the determination unit, the control signal generation unit generating an interrupt signal based on receiving the wafer-slip indication signal, wherein the interrupt signal is transmitted to CMP apparatus for stopping the CMP process.   
     
     
         5 . The apparatus of  claim 4 , wherein the received images each comprise grayscale values associated with each pixel of the received images. 
     
     
         6 . The apparatus of  claim 5 , wherein the stored reference images each comprise grayscale values associated with each pixel of the reference image, wherein the correlation unit correlates the grayscale values associated with each pixel of the reference image pixel with the grayscale values associated with each pixel of the received images to generate the correlation factor. 
     
     
         7 . The apparatus of  claim 1 , further comprising:
 an infrared laser that generates an infrared signal within the at least an area of the rotation table, the imaging device generating infrared signal images of the infrared signal within the at least an area of the rotation table for detecting the wafer-slip event.