Micromachined thermally based CMOS microsensors

TLDR

CMOS materials and physical effects relevant to thermal sensors, including microheater, thermistor, thermocouple, isolation, and heat sink structures, are reviewed, along with examples of thermal‑actuation sensors (flow, pressure, resonators) and the importance of characterizing CMOS thermal properties such as conductivity, Seebeck coefficient, and heat capacity for sensor design. The study presents an integrated circuit approach to thermal microsensors. The approach uses on‑chip bias and signal conditioning circuits fabricated with industrial CMOS IC technology combined with post‑CMOS micromachining or deposition techniques. The authors demonstrate micromachined CMOS radiation sensors, thermal converters, and two packaged microsystems—a thermoelectric air‑flow sensor and a thermoelectric infrared intrusion detector.

Abstract

An integrated circuit (IC) approach to thermal microsensors is presented. The focus is on thermal sensors with on-chip bias and signal conditioning circuits made by industrial complementary metal-oxide-semiconductor (CMOS) IC technology in combination with post-CMOS micromachining or deposition techniques. CMOS materials and physical effects pertinent to thermal sensors are summarized together with basic structures used for microheaters, thermistors, thermocouples, thermal isolation, and heat sinks. As examples of sensors using temperature measurement, we present micromachined CMOS radiation sensors and thermal converters. Examples for sensors based on thermal actuation include thermal flow and pressure sensors, as well as thermally excited microresonators for position and chemical sensing. We also address sensors for the characterization of process-dependent thermal properties of CMOS materials, such as thermal conductivity, Seebeck coefficient, and heat capacity, whose knowledge is indispensable for thermal sensor design. Last, two complete packaged microsystems-a thermoelectric air-flow sensor and a thermoelectric infrared intrusion detector-are reported as demonstrators.