Chemical downstream etching of Ge, Si, and SiNx films

Abstract

This work reports on selective isotropic dry etching of chemically vapor deposited Ge thin film, release layers using a Shibaura chemical downstream etcher with NF3 and Ar based plasma chemistry. Relative etch rates between Ge, Si, and SiNx are described with etch rate reductions achieved by adjusting plasma chemistry with O2. Formation of oxides reducing etch rates was measured for both Ge and Si, but nitrides or oxy-nitrides created using direct injection of NO into the process chamber were measured to increase Si and SiNx etch rates while retarding Ge etching. Observation of preferential etching of Ge in the presence of Si and SiNx is also observed with lateral etch rates reaching 19.2 μm/min for the Ge layers. Results presented here demonstrate the use of Ge as a microelectromechanical systems device dry release layer in the presence of Si and SiNx making it a highly advantageous technology, especially for optical devices.