Date of Award
Master of Science in Electrical Engineering - (M.S.)
Roy H. Cornely
Robert Boris Marcus
This thesis describes the fabrication of micron-sized vertical mirrors at the end of horizontal cantilevers, that are electrostatically controlled. The mirrors, 40x 40 μm with thicknesses of 1.5-6 μm, were made by using the etch resistance to 40% KOH etchant of <111> planes and oxide stripes. The cantilever beams, 100 to 350 μm long and 0.44 to 0.81 μm thick, were fabricated using the etch resistance of heavily doped boron layers to 10% KOH at 50 °C. Two technologies to introduce the boron layers were investigated. The ion implantation approach was based on thick oxide/photoresist masking. A maximum doping of 2.5 x 1020 cm-3 was achieved in a layer of about 0.83 p.m. This doping level resulted in 0.44 μm thick cantilevers after 2 hours etching to remove 40 μm of silicon under the cantilevers. Using Spin On Doped Glass (SOG) technology, a higher doping concentration was achieved, 5 x 1020 cm-3 in a layer of 1.9 μm. After etching 2.06 hours to remove 26 μm of silicon, the etched cantilevers were 0.81 μm.
Two masking methods for the SOG technique were investigated. The thick (40 μm) positive photoresist method had a problem of chemical reaction between the photoresist and the spun on doped glass. The other method, which used thin negative photoresist, was more promising. Problems related to the partial etching of the mirrors due to the incomplete SOG wetting of the mirrors' sidewalls, and proximity photoresist exposure effects, can be overcome with additional experimental work.
Abdel-Aziez, Yasser A., "Fabrication of micron-sized mirror/cantilever silicon devices for crosspoint switching arrays" (1994). Theses. 1237.