Temperature coefficient of resistance related to amorphous silicon/metal contact design of microbolometers

This paper reports stacked nitride/amorphous silicon (a-Si)/ titanium films as the absorber and polyimide as the sacrificial layer of microbolometers. The films have low stress without residue after the structural layer is released. Measurements show that the devices with higher overlapped a-Si/metal supporting legs have a higher temperature coefficient of resistance (TCR) likely because of their high heat flux. Both resistivity of a-Si and a-Si/metal contact area are important to determine the electrical resistance and noise distribution at the interface during annealing because of metal-induced crystallization. An annealing temperature of a-Si at 550 °C and above can result in a decrease in TCR. Filtered infrared and red light radiation are used to verify resistance drop, which is also correlated with radiation intensity. The resistance change is also successfully converted to 8-bit digital output.