Design and fabrication of TaN bottom electrode thermal sensing resistor for MEMs based bolometer application

In this work, TaN bottom electrode thermal sensing resistor for MEMs based bolometer was fabricated by 200mm Cu-BEOL compatible process. Thermal sensing material was B-doped alpha-Si deposited by PECVD in-situ doping process. PVD TaN film was used as bottom electrode. Dedicated process on modified tool was introduced to achieve a good contact between TaN and sensing material. There are both CVD and ETCH chamber installed on this modified tool. Wafer with bottom electrode pattern was pre-cleaned firstly by low-power Ar/CF4 gas to remove oxide and possible surface residue on TaN in etch chamber. Then the wafer was transferred to CVD chamber through transfer chamber in vacuum condition. With vacuum transfer condition and tightly Q-time control, ohmic contact can be achieved for the TaN bottom electrode and B-doped alpha-Si. Through the IV curve and TCR data it can be seen that bottom electrode device can well meet the MEMs-based bolometer requirements.