08 - • Main process groups are • Isotropic etching •...

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Wet Etching Himanshu J. Sant Fundamentals of Microfabrication Source: R.B. Darling, B. K. Gale and F. Solzbacher Overview • Etching profiles • Etching chemistry • Anisotropic – Masking – Etchants • Isotropic – Etchants – Masking materials • Electrochemical etching
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Bulk Micromachining • Microelectronic devices use planar structures/processes, etch depths are limited to a few micrometers • Microsystems devices (MEMS, sensors, actuators, channels) often require 3D structuring/etching of structure across the whole substrate (wafer)
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Unformatted text preview: • Main process groups are: • Isotropic etching • Anisotropic etching • Electrochemical etching Etch Profiles Etching Equipment Etch Fronts Etch Fronts Etch Fronts Etch Geometry [111] Convex corner undercutting Isotropic etching—Acidic media • Hole injection into the Si valence band – Oxidant – Electrical field – Photon • Nitric acid in HNA system works as oxidant • OH-groups lead to SiO 2 with H 2 as byproduct • HF dissolves SiO 2 by forming H 2 SiF 6 Utah Microelectrode Array...
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08 - • Main process groups are • Isotropic etching •...

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