SBIR Phase II: Acoustic Microcavitation Assisted Fine Cleaning of Post-Chemical Mechanical Planarizing (CMP) Wafers

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This SBIR Phase II project is to continue the investigation in the removal of particulates from silicon wafers. It is a problem which can only become more important as the evolving circuit complexity demands greater miniaturization and multi-storied 'architectural' chip designs. Miniaturization poses a increasing challenge because any particulate which is one-third to one-half the size of the smallest chip circuit feature (i.e. the line width) is deemed a killer defect. As the line width gets thinner, the particle-intolerance because correspondingly greater. Up to 40% of all silicon wafer rejections are due to unremoved particulates. The challenge of maintaining ultra-clean wafer surfaces is further exacerbated by the more complex, multi-storied chip designs. Each new 'floor' of circuitry requires that a high degree of wafer flatness and smoothness be restored using the chemical mechanical planarizing or polishing (CMP) process. Each CMP procedure involves a fine, fumed silica slurry and therefore introduces new particulates. Several CMP operations are typically necessary in wafer processing and each wafer must be perfectly cleaned after each operation. This project is to develop a precision cleaning unit to rapidly clean post-CMP silicon wafers using only 'Silent Sound and Clean Water'. Based on Acoustic Coaxing Induced Microcavitation (ACIM), the process requires no chemicals--only silent sound and clean water. The Silent Sound and Clean Water (SSCW) wafer cleaner to be developed through this SBIR Phase-II grant will face none of the conventional limitations with regard to particle size and it will be wholly environmentally friendly.