A New Temperature Transducer for Local Temperature Compensation for Piezoresistive 3-D Stress Sensors

In this paper, a new temperature transducer using full-circular n-type piezoresistor over (111) silicon plane is proposed as an accurate solution for local temperature compensation for piezoresistive three-dimensional (3-D) stress sensors. Analytical study, in this paper, showed that the proposed n-type full-circular piezoresisor over (111) has near-zero response under 3-D state of stress. As an experimental verification, a test device with n-type piezoresistive stress sensing elements oriented over (111) plane at 0° and 90° to crystallographic direction [1̅10] was microfabricated to test the capability of the proposed temperature compensator. The test device was subjected to a uniaxial load up to 50 MPa using a loading rig with four-point bending fixture. The testing was performed over a temperature range of 0-50 °C. The results showed that the proposed temperature transducer has a linear response to temperature excitation. The fabricated transducer is capable of accurately capturing the local temperature changes with maximum absolute error of ±0.8 °C. This compensation system is advantageous for piezoresistive stress/strain sensors, since the temperature transducer has the same thermal environment with the stress/strain-sensing rosette. Moreover, this technique does not require additional circuitry on the sensing device itself.