The Real Impact of Selectivity on CMP Performance

摘要

Slurry selectivity has become increasingly more important in the minds of CMP engineers over the last ten to fifteen years. In many ways, the improved natural selectivity properties of ceria drove the recent, and ongoing, conversion of oxide slurries from silica to ceria. However, selectivity is often defined as the ratio of oxide removal to nitride removal based on polishing blanket wafers for sixty seconds. This can be deceiving in many ways since blanket wafers are not always reliable models of pattern wafers that contain both topography and multiple materials in contact with the slurry at the same time. By better characterizing both the blanket and pattern behavior of a slurry, it is possible to reveal critical characteristics of slurries hitherto unknown - or at least uncharacterized - in the larger CMP world. It is the purpose of this paper to summarize the experimental results that have led to this understanding and to discuss the impact that such knowledge has on slurry design and performance.