MEMS FABRICATION BY LITHOGRAPHY AND REACTIVE ION ETCHING (LIRIE)

This paper reports on the development of a technology which will offer the potential to manufacture micro-engines, micro-turbines, micro-sensors, micro-actuators, and electronic circuits onto a single silicon chip. Axes or stators (nonmoving parts) are etched into the initial Si-wafer. The movable parts (rotors, beams, etc.) are prepared from electro-chemically etched Si-membranes with defined thicknesses. Both sides of the Si-membrane are covered with a 1.5 mum SiN(x)O(y) layer by a low stress (< 70 MP) PECVD-process. After that, all movable parts are created lithographically on the SiN(x)O(y) surface. This is followed by dry etching the mono-crystalline Si-membrane down to the SiN(x)O(y) sacrificial layer on the back side of the membrane by an RIE-process. This fixes the movable parts to the SiN(x)O(y)-layer. The wafer with the movable parts is flipped onto the wafer with the already etched axis and then positioned and centred. The SiN(x)O(y)-sacrificial layer is then dissolved by a chemical wet or vapour etch process. Subsequent bonding with a Pyrex glass wafer seals the parts.