Perfect selective and highly anisotropic electron cyclotron resonance plasma etching for WSix/poly-Si at electron cyclotron resonance position

Abstract

Perfect selective and highly anisotropic etching for tungsten polycide (WSix/poly-Si) structure without sidewall protection is achieved at the electron cyclotron resonance (ECR) position in a newly developed ECR plasma etching system. The etching selectivity ratio of WSix/poly-Si structure etching to SiO2 etching is infinite by using Cl2/SF6/O2 gas mixture under 5×10−4 Torr. The etching rate is more than 2000 Å/min with no radio frequency bias above selectivity conditions. The addition of a small amount of SF6 is efficient for removing tungsten residue. The perfect etching selectivity is caused by low ion energy at the ECR position and the effect of O2 gas addition. The high etching rate is achieved by high ion current density at the ECR position. Furthermore, a highly anisotropic etching profile is realized at the substrate temperature of 60 °C.