Reactive Ion Etching in VHF Diode Reactors

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Abstract Murnick CTS-9419440 The primary objective of the proposed work is to determine the effectiveness of a VHF diode reactor for reactive ion etching of silicon in CF4 plasmas. The PI's point out that operation at VHF ( 30-300 MHz) frequencies rather than at the standard 13.56 MHz, at least in the case of amorphous silicon deposition, can result in increased deposition rates, reduced damage, and increased film uniformity. The PI's expect the discharge physics to be quite different in the VHF regime as compared to the standard 100 KHz-13.56 MHz range and provide some evidence for this from results of their previous work. They point out that VHF operation has not as yet been applied to etching, and propose to determine etch rates, uniformity, anisotropy and damage for the etching of silicon in CF4 plasmas. Frequencies from 13.56 to 135 MHz, pressures from 1 to 50 mTorr, and a wide range of applied voltages will be employed. If possible, plasma conditions which optimize certain aspects of the etch process will be identified. Diagnostics on the etched materials will be carried out in collaboration with the Army Research Laboratory conveniently located at Fort Monmouth, using standard surface techniques including SEM, profilometry, and TEM. Use will also be made of ARL's microwave interferometer, currently on loan to Rutgers, to measure absolute, spatially averaged plasma densities. Meta-stable argon populations will also be measured using a line-of sight self-absorption technique. The PI's also propose to collaborate with Dr. Meya Meyyappan of Scientific Research Associates in the modeling of the experimental plasmas. He hopes to provide the PI's with a 2-D version of his current 1-D plasma simulation code and will assist in the modeling effort in order to provide support for the interpretation of the etching results.