Influence of Reaction Products on Si Gate Etching with a Photoresist Mask in HBr/O2 and Cl2/O2 Electron Cyclotron Resonance Plasma

Abstract

Highly directional and highly selective (Si/SiO2 and Si/photoresist) dry etching of Si metal-oxide-semiconductor (MOS) gates with a photoresist mask is achieved using electron cyclotron resonance (ECR) HBr/O2 etching reactions. In this process, the photoresist mask is coated with SiO2 in HBr/O2 plasma, and highly selective etching in Cl2/O2 plasma is combined with this SiO2 coating process. In the Cl2/O2 plasma, oxygen reacts with Si etching products such as SiClx on the surface of both the Si and the coated SiO2, generating SiO2 which is deposited as a film on the coated SiO2. However, no deposition occurs on the etching surface of Si, and the Si etching rate increases. This result proves that the SiO2 coating protects the photoresist during Cl2/O2 plasma etching.