Fabrication of thin-film thermopile micro-bridge with XeF2 etching process

These days, MEMS-based thin-film thermopiles are mainly fabricated anisotropically by wet-etching process at the back of the wafer. Their backside etching process is, however, complex, expensive, and wastes a large amount of silicon real estate. On the other hand, the front-side etching has better reliability of photolithography and also makes it possible to fabricate smaller micro-thermopile, as compared to that obtained from backside etching. In this paper, a thin-film thermopile is fabricated on a micro-bridge structure created by using the front-side etching with XeF2 gas. The resulting device is about 50% smaller in size than that of the conventional chip. The output voltage of the device is found to increase by 2.13 times and the Seebeck coefficient to enhance by 0.17 μV/°C, due to less heat-flow from hot junction to cold junction and the increase in aluminum etching hole area.