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Abstract

A dry etch apparatus for micromachining a substrate having a first and a second layer of dissimilar materials joined together at a heterojunction includes a chuck for holding the substrate. The chuck has a first electrical contact positionable to contact the first layer, and second electrical contact positionable to contact the second layer, with the first and second electrical contacts being electrically isolated from each other. A voltage source is connected to the first electrical contact of the chuck to apply a voltage potential across the heterojunction of the substrate. When a plasma containing chemically reactive ions is directed against the second layer, etching of non-masked regions continues unless it is substantially stopped at the voltage biased substrate heterojunction. The substrate can be cooled or periodically recoated with erodable protective material to limit sidewall damage to the substrate while still allowing downward etching into the substrate. This dry etch process is well suited for construction of dimensionally accurate microdevices and microelectromechanical systems.

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First Claim