Bulk and surface micromachining of GaAs structures

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Abstract
Two separate schemes for bulk micromachining are presented together with experimental results on microfabricated cantilever beam structures indicating that conventional lithography and wet etching techniques can be used to produce geometrically well-defined, high-strength GaAs elements (fracture limits<or=4 GPa). A process scheme of surface micromachining is presented. The scheme is basically the same as for surface micromachining of polysilicon structures, but in a different materials system. It is realized by a combination of the multisequential epitaxy and the sacrificial layer technique used in the lift-off technique for epitaxial GaAs films. Some characteristics of surface micromachined GaAs structures are: single crystalline structures, wet etching may be used throughout, deposited layers are conformal to underlaying layers, low built-in stresses, and thick structures are possible.