Characteristics of residual products in HF gas-phase etching of sacrificial oxides for silicon micromachining

Abstract

We employed a newly developed HF gas-phase etching (GPE) process for the removal of sacrificial oxides. The structural layers are P-doped multi-stacked polysilicon and silicon epi-layer of SOI substrates and sacrificial layers are TEOS, LTO, PSG, and thermal oxides on silicon nitride or polysilicon substrates. The characteristics of residual products on polysilicon or silicon nitride were scrutinized by using SEM and AES. After GPE of TEOS, LTO, and PSG on the silicon nitride substrate, the polysilicon microstructures are stuck to the underlying substrate because neither the SiO<SUB>x</SUB>N<SUB>y</SUB> layers nor the H<SUB>3</SUB>PO<SUB>4</SUB>(H<SUB>2</SUB>O) layer vaporize. We found that the etching of TEOS, LTO, and thermal oxide on a polysilicon substrate shows no residual product and no stiction.