Evaluation of CF₂ Radical as a Precursor for Fluorocarbon Film Formation in Highly Selective SiO₂ Etching Process Using Radical Injection Technique

Abstract

A radical injection technique (RIT) was developed to evaluate CF 2 radical as a precursor for fluorocarbon film formation in a highly selective SiO 2 etching process. Using RIT, the CF 2 radical was successfully injected into electron cyclotron resonance (ECR) downstream plasmas employing Ar and H 2 /Ar mixtures. The fluorocarbon films formed on the Si surfaces exposed to ECR downstream plasmas were investigated using X-ray photoelectron spectroscopy. The deposition rate of fluorocarbon films was measured by varying microwave power in the Ar and H 2 /Ar ECR plasmas while keeping CF 2 radical density constant using RIT. From the experimental results, it was found that the CF 2 radical was the important precursor for fluorocarbon film formation only with the assistance of the surface activation due to the plasma exposure and that H atoms and CF 2 radicals in the plasma played an important role in the formation of carbon-rich fluorocarbon film resulting in highly selective SiO 2 etching. Furthermore, the highly selective SiO 2 etching was demonstrated using the H 2 /Ar ECR downstream plasma with CF 2 radical injection.