Hydrogenation-assisted lateral micro-machining of (111) Silicon Wafers

Micromachining of (111) silicon wafers by means of a plasma hydrogenation and chemical etching sequence is achieved. Vertical etching is used to define the depth of the craters as well as the thickness of the final suspended silicon body. After protecting the three-dimensional structure by a thermally-grown oxide, a hydrogenation step is used to remove the oxide layer from the bottom of the crater, allowing a lateral under-etching. Final exposure of processed silicon to a KOH solution laterally etches the silicon in the exposed places. A lateral aspect ratio of 4 to 6 has been achieved. The evolution of suspended structures on (111) wafers, suitable for sensor fabrication, is feasible without a need to a three-dimensional lithography.

Keywords:

Micromachining , (111) wafers , hydrogenation , chemical etching.