EXTREMELY HIGH-SELECTIVE ELECTRON-CYCLOTRON RESONANCE PLASMA-ETCHING FOR PHOSPHORUS-DOPED POLYCRYSTALLINE SILICON

Extremely high-selective etching for phosphorus-doped polycrystalline silicon is achieved at the electron cyclotron resonance (ECR) position in a newly developed ECR plasma etching system. The selectivity ratio (phosphorus-doped polycrystalline silicon etching rate/SiO2 etching rate) is around 100 at 5×10-4 Torr and 260 at 3×10 -3 Torr. Furthermore, the polycrystalline silicon etching rate is more than 3000 Å/min in pure Cl2 etching gas with no rf bias under the above selectivity ratio conditions. The high etching selectivity ratio is generated by low ion energy due to no rf bias power and small magnetic field divergence. The high etching rate is achieved by high ion current density at the ECR position in the plasma chamber.