ELECTRON-CYCLOTRON-RESONANCE PLASMA-ETCHING OF SI WITH CL2 - PLASMA CHEMISTRY AND MECHANISMS

Electron cyclotron resonance (ECR) plasma etching of Si with Cl2 has b een investigated from the viewpoint of plasma chemistry. Experiments w ere performed over a wide pressure range (0.2-10 mTorr), using a diver gent magnetic-field ECR plasma reactor supplied with 2.45-GHz microwav e input powers; a floating electrode or substrate holder was located a pproximately 30 cm downstream (B almost-equal-to 150 G) from the 875-G ECR resonance region, and samples of polycrystalline Si were etched w ith no additional wafer biasing. Several diagnostics were employed to characterize the plasma around the wafer position: two-photon laser-in duced fluorescence (LIF), optical emission spectroscopy, microwave int erferometry, and electrical measurements with Langmuir probes and a re tarding grid analyzer. Moreover, chemical kinetics in Cl2 plasmas were modeled to gain an insight into the LIF and optical emission measurem ents, and to know chemical compositions in ECR Cl2 plasmas. Attention was then focused on neutral Cl atom fluxes and ion energies and fluxes onto the substrate, and on their correlations with the etching charac teristics such as etch rates and profiles. The etch rate behavior is i nterpreted in terms of a modified adsorption-reaction-ion stimulated d esorption process, and some lateral etching after an overetch step in terms of the incoming ion trajectories.