Fabrication of a membrane type double cavity vacuum‐sealed micro sensor for absolute pressure based on front‐side lateral etching technology

Abstract

PurposeThe purpose of this paper is to describe the fabrication of a miniaturized membrane type double cavity vacuum‐sealed micro sensor for absolute pressure using front‐side lateral etching technology.Design/methodology/approachPotassium hydroxide‐based anisotropic etching of single crystal silicon is used to realize the cavities under the membrane type diaphragms through channels on the sides. The diaphragms consist of composite layers of plasma‐enhanced chemical vapour deposition (PECVD) of silicon nitride and silicon dioxide. PECVD of silicon dioxide is done for sealing the channels and the cavity in vacuum. Boron thermal diffusion in low‐pressure chemical vapour deposition of polysilicon layer over the membrane is done for realizing resistors. The fabricated device uses Wheatstone half bridge circuit to read the variation of resistance with respect to an applied pressure.FindingsA double cavity vacuum‐sealed absolute pressure micro sensor has been fabricated successfully using front‐side lateral etching technology and has been measured for pressure range of 0‐0.45 MPa. The measured pressure sensitivity of two pressure sensors is 9.28 and 10.44 mV/MPa.Originality/valueThe paper shows that front‐side lateral etching technology is feasible in the fabrication of small vacuum‐sealed cavities and absolute pressure sensors.