A single-mask thermal displacement sensor in MEMS

TLDR

The study introduces a MEMS displacement sensor that uses conductive heat transfer from a resistively heated silicon structure to a parallel actuated stage, aiming to optimize sensitivity through a lumped capacitance model. The sensor is a differential design fabricated on a silicon‑on‑insulator platform within a single mask alongside electrostatic actuators and flexure stages, with sensitivity tuned by adjusting doping, temperature, heater dimensions, and a lumped capacitance model. Experimental results show the sensor achieves a 2 nm resolution over a 25 Hz bandwidth with a full‑scale range of 110 µm.

Abstract

This work presents a MEMS displacement sensor based on the conductive heat transfer of a resistively heated silicon structure towards an actuated stage parallel to the structure. This differential sensor can be easily incorporated into a silicon-on-insulator-based process, and fabricated within the same mask as electrostatic actuators and flexure-based stages. We discuss a lumped capacitance model to optimize the sensor sensitivity as a function of the doping concentration, the operating temperature, the heater length and width. We demonstrate various sensor designs. The typical sensor resolution is 2 nm within a bandwidth of 25 Hz at a full scale range of 110 µm.