| 摘要 |
Silicon multi-layer etching comprises anisotropic plasma etching of trenches (21') down to a buried separation layer (12,14,14',16), etching the exposed separation layer and then etching an underlying silicon layer (17, 17'). Etching of a layered silicon body, having a first silicon layer (15) provided with an etch mask (10), comprises: (a) a first anisotropic plasma etching operation which produces trenches (21') in the region of the mask openings (21) and which terminates at a separation layer (12,14,14',16) buried between the first silicon layer (15) and a further silicon layer (17,17'); (b) a second etching operation for etching through the exposed portions (23,23') of the separation layer; and (c) a third etching operation to etch the further silicon layer (17,17'). Preferred Features: The third etching operation produced complete isotropic under-etching between two or more trenches so that a free standing structure (32) is created. The first etching operation is a dry etching operation comprising alternate deposition and isotropic etching steps, the deposition steps being carried out using a high density plasma (especially a PIE (propagation ion etching) plasma or an ICP (inductively coupled plasma)) of a polymer-forming monomer source gas which forms a Teflon (RTM) like film (20) on the trench side walls, while the etching steps employ a fluorine radical source gas, especially SF6 with added oxygen. The separation layer comprises a first section (12) of silicon dioxide, silicon oxide, silicon nitride, glass and/or ceramic, especially thermally grown silicon dioxide, and a second section (16) of silicon dioxide deposited by CVD especially from silanes. The separation layer sections (12, 16) are 500 nm to 50 mu m (especially 1-10 mu m) thick. The second etching operation is a dry chemical, especially plasma, etching operation or possibly a wet chemical etching operation using dilute hydrofluoric acid. All the etching operations are carried out in a single etching chamber and the etched body is post-treated in an oxygen plasma stripper for ashing of the mask and the residual Teflon (RTM) like film.
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