Etching of Si and SiNx by Beams Emanating from Inductively Coupled CH3F/O2 and CH3F/CO2 Plasmas

In advanced microelectronic device fabrications, novel gate electrode designs for field effect transistors (FinFETs) require highly anisotropic and selective silicon nitride (SiNx) etching over Si and/or SiO2. SiNx substrates and p-Si on Ge substrates were etched with CH3F/O2 and CH3F/CO2 inductively coupled plasma beams. In addition, polymer films deposited on p-Si and SiNx were characterized and compared via x-ray photoelectron spectroscopy analyses. Optical emission species intensity and species number density of the hydro-fluorocarbon plasma, as a function of % O2 and CO2 addition were compared. Etch and deposition rates were measured on either side of abrupt transitions in gas-phase species concentration, detected at ~ 48 % O2 and ~ 74% CO2. These transition point compositions correspond to a switch from polymer-coated to polymer-free reactor walls.