Chemical Kinetics of Chlorine in Electron Cyclotron Resonance Plasma Etching of Si

Electron cyclotron resonance (ECR) plasma etching of Si in Cl2has been studied from the viewpoint of plasma chemistry. Experiments were performed over a wide pressure range (0.2-10 mTorr), using a divergent magnetic-field ECR plasma reactor supplied with 2.45-GHz microwaves; a floating electrode or substrate holder was located ?30 cm downstream (B?150 G) of the 875-G ECR resonance region, and samples of polycrystalline Si were etched with no additional wafer biasing. Several diagnostics were employed to characterize the plasma around the wafer position, including two-photon laser-induced fluorescence (LIF) for detection of Cl atoms and Fourier transform infrared (FTIR) absorption spectroscopy for etch products or SiClx(x=1-4) molecules. The Si etch rate behavior obtained is interpreted in terms of a modified adsorption-reaction-ion-stimulated desorption process model based on these diagnostics.