Preparation of Silicon-on-Insulator Wafer Using Spin Etching and a Subsequent Selective Etching Process

Abstract

A novel thinning process was proposed for the preparation of bonded and etched silicon-on-insulator (BE-SOI) wafers with high quality and good thickness uniformity by adopting a spin etching and subsequent selective etching as a thinning process. A solution comprising HNO3, HF, H3PO4 and H2SO4 was used for the spin etching process. The spin etching process removed the damaged layer originating from a back-grinding process, which simultaneously yielded SOI wafers with better thickness uniformity than usual back-ground ones. Selective etching adopting a layer with high boron concentration as an etch stop layer was subsequently carried out to achieve better thickness uniformity than that obtained after the spin etching process. The solution for the selective etching process was prepared by diluting NH4OH and H2O2 with de-ionized water. BESOI wafer with excellent surface roughness equivalent to that of a polished Si wafer could be prepared by removing the surface layer of high boron concentration during a chemical mechanical polishing (CMP) process.