Nondestructive characterization of CMP pads using statistical design analysis

Chemical-mechanical planarization is a critical abrasive process in the production of semiconductor devices used for polishing the surface of wafers. The characterization of an IC wafer-polishing pad, in terms of its density, is crucial for planarization efficiency. Most of the currently available procedures for pad characterization are typically destructive in nature. This paper, however, demonstrates through statistical design of experiments the effectiveness of ultrasound technology to analyze the underlying pad structure in a nondestructive regime. Moreover, the impact that physical factors such as temperature and humidity could have on the structure and the ultrasonic characterization of the pad are studied. The results from a single factor and a multifactor analysis of the different sections of the pad are discussed.