Temperature Sensor in a Flexible Substrate

This paper presents the fabrication and measured performance of temperature sensors embedded in flexible polyimide substrates. The sensing material used for the temperature sensor was undoped amorphous silicon which was fabricated on a 35-m-thick layer of polyimide that serves as the flexible substrate. Another flexible polyimide superstrate layer of 35-40 m was spin-coated on top of the sensors to make sure the temperature sensors lie on a zero stress plane. The temperature coefficient of resistance was measured over the temperature range of 200- 360 K. The maximum temperature coefficient of resistance at 30 C was measured to be 0.0288 K^-1. The effect of the flicker noise and voltage dependence of the voltage noise power spectral density exhibited by the sensor was evaluated. The normalized flicker noise coefficient was found to be 1.2 × 10^-11.