Design, fabrication and characterization of a high-sensitivity pressure sensor based on nano-polysilicon thin film transistors

Xiaofeng Zhao,Dandan Li,Yang Yu,Dianzhong Wen

doi:10.1063/1.4938517

Abstract

Based on the nano-polysilicon thin film transistors (TFTs), a high-sensitivity pressure sensor was designed and fabricated in this paper. The pressure sensing element is composed of a Wheatstone bridge with four nano-polysilicon TFTs designed on different positions of the square silicon diaphragm. Via taking the four channel resistors of the TFTs as piezoresistors, the measurement to the external pressure can be realized according to the piezoresistive effects of channel layer. Through adopting complementary metal oxide semiconductor (CMOS) technology and micro-electromechanical system (MEMS) technology, the chips of sensor were fabricated on &lt;100 &gt; orientation silicon wafer with a high resistivity. At room temperature, when applying a voltage 5.0 V to the Wheatstone bridge, the full scale (100 kPa) output voltage and the sensitivity of the sensor with 35 μm-thick silicon diaphragm are 267 mV and 2.58 mV/kPa, respectively. The experimental results show that the pressure sensors can achieve a much higher sensitivity.

Highlights

In 1954, Smith found the piezoresistive properties of silicon and germanium in experiment, and derived piezoresistive coefficients on the change of resistance with stress
Through adopting complementary metal oxide semiconductor (CMOS) technology and microelectromechanical system (MEMS) technology, the chips of sensor were fabricated on < 100 > orientation silicon wafer with a high resistivity
The basic structure of the nano-polysilicon thin film transistors (TFTs) designed on a high resistivity < 100 > orientation silicon wafer is shown in Fig. 1(a), in which L and W are the channel length and width of the TFT, respectively

Summary

INTRODUCTION

In 1954, Smith found the piezoresistive properties of silicon and germanium in experiment, and derived piezoresistive coefficients on the change of resistance with stress. Many of studies for piezoresistive pressure sensors have been carried out via piezoresistive effects of silicon.[1,2,3] In recent years, with the development of nano-technology, many new types of pressure sensing materials have been studied to significantly improve the sensitivity for piezoresistive pressure sensors, such as nanowires,[4] nanotubes,[5] nano thin films,[6,7] MOSFET channel layers,[8,9,10,11,12,13,14,15] etc. Comparing with the diffusing silicon pressure sensor, the impact of the structure parameters on the proposed sensor are investigated in the paper

Basic structure

Operating principle

Nano-polysilicon thin films

CONCLUSION