Quantitative study of chemical mechanical planarization process affected by bare silicon wafer front surface topography

Chemical mechanical planarization (CMP) is an enabling technology in the fa brication of advanced semiconductor devices. The surface topography of the starting bare silicon substrate before CMP can have a significant impact on the results of the CMP process, specifically on the uniformity of the oxid e film final thickness. The quantitative studies of this phenomenon an just beginning. In this article, a laser based optical scanning measurement was used to determine the front surface topography of the bare silicon substra tes prior to thermal oxide growth. Fast two-dimensional mapping of the surf ace height variation is obtained with very high spatial and height resoluti on. The one-dimensional cross-section profile extracted from the measuremen t is demonstrated to have good correlation with the stylus based profiler m easurement. A thermal oxide layer was grown and then polished in a high eff iciency planarization process on a group of substrates, which had difficult levels of surface topography variations on the starting surface. A signatu re match between the oxide thickness variation and the silicon substrate fr ont surface topography was identified. The resultant correlation reveals th e potential impact on CMP process window from the starting material due to the degradation of within-die and die-to-die uniformity. Consequently, the product yield could be threatened. The optical topographical measurement us ing this laser scanning measurement is demonstrated here to be capable of p roviding fast, vital and unique information critical to achieving satisfact ory results in the oxide CMP process. (C) 1999 American Society .