Influence of temperature on the formation of SiF2 molecules

Abstract

Chemical etching of silicon in SF6 plasma is considered. Dependences of Si etching rate on pressure of reactive species are measured at two different temperatures. Atomic layer etching of silicon with F atoms is analyzed using theoretical results obtained by fitting the experimental data. It is found that at high pressure, the formation of SiF2 molecules is the etching-rate limiting process. As a result, dependences of Si etching rate on pressure of reactive species have pronounced maxima. The increase in temperature during Si etching in SF6 plasma shifts maximum etching rate to lower pressure. This phenomenon is caused by an increased chemisorption of F atoms on the surface.