Investigations of reactively sputtered TiO2-δ films for microbolometer applications

Heat-sensitive material is one of the most essential parts of microbolometer fabrication. Vanadium oxide (VOx) and amorphous silicon (a-Si) are widely accepted materials for commercialized focal plane arrays. Meanwhile, there are a lot of efforts for finding alternative materials having better performance, lower process cost and higher yield. In this study, reactively sputtered titanium oxide (TiO2-δ) films were investigated for heat sensitive material. Microbolometer device was also fabricated by using the TiO2-δ film as a heat sensitive material. It is well known that the TiO2-δ can have several phases according to film deposition condition. Properties of TiO2-δ film could be largely varied by controlling the deposition condition. Resistivity of the fabricated TiO2-δ film was ranged from 10-2 Ω•cm to 10 Ω•cm. Negative TCR(temperature coefficient of resistance) value up to 2.8 %/K was obtained. 1/f noise of the TiO2-δ film was comparable to that of VOx film. From the fabrication result of microbolometer device, feasibility of the reactively sputtered TiO2-δ film was demonstrated. NETD(Noise equivalent temperature difference) of the 50μm-pitch simple single-level membrane structure microbolometer was 34mK with conditions of 1V bias and 30Hz operation frequency.