Piezoresistive temperature sensors fabricated by a surface micromachining CMOS MEMS process

Chunhua Cai,Junyan Tan,Di Hua,Ming Qin,Nianfang Zhu

doi:10.1038/s41598-018-35113-z

Abstract

This paper presents a micromachined monocrystalline silicon piezoresistive temperature sensor fabricated by a surface micromachining CMOS (Complementary Metal Oxide Semiconductor) MEMS (Micro-Electro-Mechanical System) process. The design of the temperature sensor is based on the structure of the multi-layer cantilever beam and the bimetallic effect. The temperature change of the cantilever beam is translated into the change of the piezoresistance’s value. The test results show that the sensitivities of the sensors are 27.9 mV/°C with 100 Ω/▯ piezoresistance between −40 °C to 60 °C and 7.4 mV/°C with 400 Ω/▯ piezoresistance between −90 °C to 60 °C. The temperature sensor proposed in this paper can be used in radiosondes for its low operating temperature (as low as −90 °C), small size (below 1 mm2) and low heat capacity.

Highlights

With the development of micro-fabrication process and monolithic integration technology[1], many types of miniature temperature sensors have been studied and applied widely
A modified miniature monocrystalline silicon piezoresistive temperature sensor is presented in this paper
It is fabricated by a commercial surface micromachining CMOS MEMS process

Summary

Introduction

With the development of micro-fabrication process and monolithic integration technology[1], many types of miniature temperature sensors have been studied and applied widely. There is almost no miniature temperature sensor compatible with CMOS manufacturing process that can operate in the range between −90 °C and 60 °C. The fabrication process needed wet etching on the backside of silicon substrate, which could lead to ion contamination on CMOS IC and is not compatible with CMOS process This fabrication process used by Dr Ma chose the SOI wafer as the substrate material[8], which was expensive and increased the cost of the sensor. A modified micromachined monocrystalline silicon piezoresistive temperature sensor is proposed to achieve miniaturization, high adaptability and low response time. This temperature sensor is constructed as four multilayer cantilevers and fabricated by a surface monocrystalline silicon CMOS MEMS process.

Methods

Results

Conclusion