Piezoresistance characterization of commercial CMOS gate polysilicon and its application in biomass microsensors

Abstract

This paper presents experimental results on the piezoresistance characterization of gate polysilicon available from two commercial CMOS processes. It is shown that the gate polysilicon is very strain-sensitive, and a gauge factor of about 25 can be readily achieved. This value can allow standard gate polysilicon to be used as a strain-sensing element for integrated microsensor applications. As an example, a sub-nanogram mass sensor was fabricated using commercially available CMOS technology and is presented. The device incorporates gate polysilicon of the CMOS process as the sensing material, and is subjected to low levels of strain in order to measure small masses (< 10−9 g). A potential application for this sensor is to monitor the growth of biological cell cultures in a liquid environment.