Amorphous silicon and tungsten etching employing environmentally benign plasma process

A novel dry etching process for amorphous silicon (a-Si) and tungsten (W) for chemical vapor deposition (CVD) chamber cleaning has been performed by electron cyclotron resonance (ECR) O2 plasma employing a solid-material evaporation system where fluorocarbon species are produced from fluorinated ethylene propylene (FEP) by CO2 laser evaporation for preventing global warming. This process enables us to realize etching of materials without using any perfluorocompound (PFC) feed gases which have a high global warming potential (GWP). Etching characteristics together with diagnostics of the F atom density, CFx (x = 1-3) radical densities, electron density and temperature have been investigated as functions of pressure. As a result, it was found that etching rates of a-Si and W films were determined based on the F atom density, ion flux and ion bombardment energy. Furthermore, etching rates of a-Si and W films increased by heating the fluorocarbon species before introducing them into the plasma reactor. Thus, high rates of etching of a-Si and W films were successfully achieved by this novel etching process compared with conventional etching using ECR plasma with CF4/O2 feed gases.