There are few plasma etching processes, if any, that meet all the basic requirements for pattern transfer: anisotropic profile, good photoresist integrity, high selectivity to the underlayer, and lack of polymer formation. Chlorine plasma is commonly employed to anisotropically etch polysilicon with good selectivity to gate oxide, but it erodes photoresist and results in a narrower etched polysilicon line. This paper discloses a new plasma etching gas for silicon, hydrogen bromide neat, that etches polysilicon anisotropically at low power with extremely high selectivity to both gate oxide (100/1) and photoresist (60/1). As a result of the low erosion rate of the photoresist, a ten micrometer deep trench in silicon is accomplished with a photoresist mask as opposed to an oxide mask. Preliminary result on silicide etching with hydrogen bromide plasma is also reported.

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