Thermal Conductivity improvement of microbolometer leg materials

A major factor controlling the performance of Infrared imaging Focal Plane Arrays (FPAs) is the thermal isolation of the array pixels as quantified by the associated pixel thermal conductance. The thermal conductance of the legs depends on the thermal conductivity and the geometry of the leg material. For the currently used pixel leg materials the thermal conductivity is not low enough, and the leg thermal conductance is reduced by increasing the leg length and decreasing the cross sectional area. To optimize the pixel response, the leg thermal conductivity should be reduced while maintaining an appropriate electrical conductivity to communicate with the ROIC. The best choice to reduce the thermal conductivity of a leg material is by the reduction of the lattice term (?L) of the thermal conductivity due to phonons. The following strategies are proposed to reduce ?L: Reduce phonon mean free path through defect incorporation and introduction of stacking faults along the length of the structure, increase surface roughness, incorporate impurity atoms of different masses and defects.