Doping effects in reactive plasma etching of heavily doped silicon

Abstract
Etch rates of heavily doped silicon films (n and p type) and undoped polycrystalline silicon film were studied during plasma etching and also during reaction ion etching in a CF4/O2 plasma. The etch rate of undoped Si was lower than the n+‐Si etch rate, but higher than the p+‐Si etch rate, when the rf inductive heating by the eddy current was minimized by using thermal backing to the water‐cooled electrode. This doping effect may be explained by the opposite polarity of the space charge present in the depletion layer of n+‐Si and p+‐Si during reactive plasma etching.

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