Dynamic behavior and application of micro sensors with negative temperature coefficient

Abstract

In our experiments a differential (high pass) frequency response of a thermal sensor was observed. The theoretical analyses have been developed to characterize the new phenomena of the micro thermal sensor. The thermal sensor is made of low level doped poly-silicon with a negative TCR (temperature coefficient of resistivity) of about -0.2%//spl deg/C. It has dimensions of 2/spl times/80/spl times/0.5 /spl mu/m/sup 3/ and it is operated under constant current. This high pass characteristic has been applied to the frequency compensation of conventional thermal sensors with positive TCR. On the same silicon chip, one sensor is doped to a high level so that it has a positive TCR while the other has negative TCR by being doped to a low level. The integration (low pass) characteristic in the former sensor can be compensated for by the differential (high pass) characteristic in the latter sensor. A cut-off frequency of about 100 kHz for the former sensor has been reached by using this compensation (called self-compensation).