Silicon etching technologies

Acidic silicon etchants are mainly used for two purposes for the delineation of crystal defects, as discussed in Section 2.5, or to remove silicon in an isotropic manner. Isotropic etching adds another degree of freedom to the design of micromechanical structures, because all alkaline etches are anisotropic. Most isotropic etchants for silicon were developed in the early days of silicon crystal technology and exhaustive reviews on this topic are available [Tu3, Rul]. A brief summary is given below. 

H. Muraoka, T. Ohashi, and Y. Sumitomo, Controlled preferential etching technology, in Semiconductor Silicon, H. R. Huff and R. R. Burgess (eds.), p. 327, Electrochemical Society, Pennington, 1973. 

The deep reactive-ion etching technology, also called Bosch process, uses the concept of alternate etch and passivation steps to achieve high aspect ratio (depth to width ratio of microchannel) silicon deep micromachining. In this process, silicon can be deeply micromachined, even through the whole wafer of few hundred micrometers with aspect ratio as high as 30 to 1, without considering the wafer orientation. 

Schoisswohl M, Cantin JL, von Bardeleben HJ, Amato G (1995) Electron paramagnetic resonance study of luminescent stain etched porous silicon. Appl Phys Lett 66 3660-3662 Schwartz B, Robbins H (1976) Chemical etching of silicon IV. Etching technology. J Electrochem... 

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