Handbook of Silicon Based MEMS Materials and Technologies

28.1. Polycrystalline Silicon-Based Micromachining

28.1.1. Overview

For the fabrication of a surface micromachined device, a sequence of thin layers must be subsequently deposited and structured on the front surface of a silicon wafer. Schematically, the cross-section in Figure 28.1 illustrates the process flow and the layer sequence. First, a silicon dioxide layer serves to electrically insulate a highly conductive polysilicon that is used as buried wiring layer for the interconnection of the functional layer parts. Alternatively or in addition to this, the buried polysilicon material can be applied as a counter electrode in some sensor types. The deposition of a subsequent silicon dioxide supplies the insulation of the buried wiring layer ...