Patent ID: 7220678

Claim:
A silicon-substrate etching method comprising: a mask-forming step of forming an etching mask on a silicon substrate surface; an etching step, carried out in sequence following said mask-forming step, of dry-etching the silicon substrate through openings in the etching mask to form on the silicon substrate predetermined structural features defining an etching ground, using SF 6 gas as an etching gas and a fluorocarbon gas as a protective-film-forming gas, in a mixture of 5 to 12 volume parts fluorocarbon gas to 100 volume parts SF 6 gas, to advance dry-etching mainly of the etching ground, with the gas mixture being converted into plasma by high-frequency power a film-forming step of using the SF 6 gas and the fluorocarbon gas, in a mixture of 2 to 5 volume parts SF 6 gas to 100 volume parts fluorocarbon gas, to form a protective film on surfaces, among the structural features, that are perpendicular with respect to the etching ground surface, with the gas mixture being converted into plasma by high-frequency power; wherein said etching step and protective-film-forming step are sequentially repeated while power is continually applied to the silicon substrate to put a biasing potential on the substrate.