Silicon-compatible waveguides used for an integrated opto-mechanical pressure sensor

We present the investigation of different types of silicon-compatible optical waveguides and the possibility to use them in an opto-mechanical pressure sensor. Silicon-based integrated optics appears as an attractive domain of applications for micromachining and allows the development of micro-opto-mechanical systems (MOEMS). Optical systems integrated on silicon are of special interest because of their process compatibility with CMOS technology. The work is focused on the fabrication of an opto-mechanical pressure sensor based on a Mach-Zehnder interferometer, integrated with photodiodes and diaphragms. Micromechanical, optical and microelectronic structures are fabricated on the same silicon substrate. The mechanical part is a cascade of three diaphragms, made by wet anisotropic etching of the substrate. For optical waveguides we experimented with different materials: Si3N4, SiON, polyimides, SiC, and amorphous silicon. We investigated the optical properties of these materials, technological processes and the possibility to integrate them in a microsystem. (C) 2001 Elsevier Science B.V. All rights reserved.