A versatile and modularizable micromachining process for the fabrication of thermal microsensors and microactuators

We present a fabrication process for a family of thermal microsensors and microactuators based on a porous silicon sacrificial layer technology. In contrast to previous work on porous-silicon-based micromachining processes, our process is modularized into a complementary metal-oxide semiconductor (CMOS) compatible front-end and a sensor- or actuator-specific back-end module. The front-end module yields silicon hotplate structures which can be fabricated in typical CMOS foundries. Such hotplates are characterized by high mechanical strength and good thermal insulation. High levels of thermal insulation are attained by employing extremely deep sacrificial layers approaching the wafer thickness. We show that different kinds of thermal microsensors and microactuators can be produced using identical front-end modules. The adaptation of the microstructures to different application needs can be performed in a small number of sensor- or actuator-specific back-end processes. We propose that such modularization schemes allow small- and medium-sized companies, with specialized application know-how and access to limited-size markets, to benefit from the mass fabrication capabilities of modern silicon foundries.