A versatile and modularizable micromachining process for the fabricationof thermal microsensors and microactuators

Abstract

We present a fabrication process for a family of thermalmicrosensors and microactuators based on a porous silicon sacrificiallayer technology. In contrast to previous work on porous-silicon-basedmicromachining processes, our process is modularized into a complementarymetal-oxide semiconductor (CMOS) compatible front-end and a sensor- oractuator-specific back-end module. The front-end module yields siliconhotplate structures which can be fabricated in typical CMOS foundries.Such hotplates are characterized by high mechanical strength and goodthermal insulation. High levels of thermal insulation are attained byemploying extremely deep sacrificial layers approaching the waferthickness. We show that different kinds of thermal microsensors andmicroactuators can be produced using identical front-end modules. Theadaptation of the microstructures to different application needs can beperformed in a small number of sensor- or actuator-specific back-endprocesses. We propose that such modularization schemes allow small- andmedium-sized companies, with specialized application know-how and accessto limited-size markets, to benefit from the mass fabrication capabilitiesof modern silicon foundries.