A high performance single-chip uncooled a-Si TFT infrared sensor

This paper reports the theory, fabrication and testing of a novel single-chip uncooled infrared (IR) sensor using amorphous silicon thin film transistors (a-Si TFT) as the active elements. The measured temperature coefficient of the channel current (TCC) of the TFT is about 6.5%/K at 300 K. A porous silicon (PS) surface micromachining technique is developed to fabricate the thermal isolation structures. The whole process is compatible with the standard IC process. In order to eliminate the self-heating effect of the TFT active element in focal plane array applications, a reference TFT element is fabricated on a 7.5 /spl mu/m thick PS layer. Preliminary experimental results show that a responsivity of over 52 kV/W, a detectivity of 8.5/spl times/10/sup 8/cm Hz/sup 1/2//W and a thermal response time of 7.5 ms are achieved at a chopping frequency of 30 Hz.