PIEZORESISTANCE CHARACTERIZATION OF COMMERCIAL CMOS GATE POLYSILICON AND ITS APPLICATION IN BIOMASS MICROSENSORS

This paper presents experimental results on the piezoresistance charac terization of gate polysilicon available from two commercial CMOS proc esses. It is shown that the gate polysilicon is very strain-sensitive, and a gauge factor of about 25 can be readily achieved. This value ca n allow standard gate polysilicon to be used as a strain-sensing eleme nt for integrated microsensor applications. As an example, a sub-nanog ram mass sensor was fabricated using commercially available CMOS techn ology and is presented. The device incorporates gate polysilicon of th e 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 a pplication for this sensor is to monitor the growth of biological cell cultures in a liquid environment.