Investigating Post CMP Cleaning Processes for STI Ceria Slurries

摘要

The STI (Shallow Trench Isolation) polishing process involves planarizing CVD silicon oxide films as part of the gate oxide structure. Both silica- and ceria-type slurries have been used for this process. Certain new ceria slurries appear to achieve STI pattern planarization with minimal oxide erosion. There has been some concern that cerium ions (besides other metal ions) will be absorbed onto the very sensitive STI structure. It is critical that an aggressive post CMP cleaning process be developed to remove trace metal and paniculate contamination. This paper will discuss initial results for the effect of hydrogen peroxide and buffer chelating solutions (BCS) used with single wafer post CMP cleaning equipment with either megasonic or brush or a combination of both to reduce metal ion and cerium particle contamination. Other chemistries with pH ranging from 1 to 10 are also discussed. Metal ion contamination can be reduced to 2E8 atoms/cm~2 and removing ～98% ceria oxide particles.