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

Abstract

Electron cyclotron resonance (ECR) plasma etching of Si in Cl 2 has 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 SiCl x ( 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.