The Pressure Sensor Fabrication Process

Abstract

This chapter describes in detail the pressure sensor fabrication process. the maximum processing temperature of the complete sensor, including the poly-SiGe piezoresistors, is kept below 460 \(^{\circ }\text{ C }\) to enable above-CMOS integration. The developed process allows for the simultaneous fabrication of both piezoresistive and capacitive pressure sensors. It can also be used to fabricate sensors of different size and with different requirements (i.e, sensitivity, nonlinearity, sealed-in pressure, etc). Many of the process steps used in the fabrication of the pressure sensor are borrowed from the thin-film packaging flow, part of the SiGe-MEMS platform in imec. Section 4.1 presents a generic cross-section of a combined piezoresistive/capacitive pressure sensor. Section 4.2 describes the different steps of the developed process flow for the fabrication of the pressure sensor. In Sect. 4.3 a more detailed description of the different process developments performed at imec specifically for the pressure sensor is given. The chapter ends with a summary of the developed fabrication process.