Room-Temperature TiO2 Gas Sensor with Conical-TSV Using a Thermal Oxidation Process

Through-silicon via (TSV) technology is used to produce a TiO2 gas sensor. The conical TSV structure is constructed using a laser with a wavelength of 1064 nm, and the depth-to-diameter ratio is 20:13 (200 mu m: 130 mu m). The sensing layer TiO2 is fabricated by using a thermal oxidation (TO) process and covers the TSV structure. X-ray diffraction and energy-dispersive X-ray spectroscopy analysis show that the main plane of the TiO2 film is (110), and there is a uniformly covered TSV structure. For the TiO2 gas sensor operating at room temperature (RT) of 25 degrees C, the recorded sensor responses are 12.08, 15, 18.5, 23.9, 31, and 38.9%, corresponding to NO2 concentrations of 0.25, 0.5, 1, 2, 5, and 10 ppm. In assessing the stability, the sensing result registers 18.5% over three cycles at 1 ppm of NO2, with a deviation under +/- 0.2%. The TiO2 material exhibits better selectivity for NO2 than for other gases (NH3, CO2, CO, H-2, H2S, and SO2). The results of this study show that the RT TiO2 gas sensor with a TSV structure is stable, reversible, and exhibits good selectivity for NO2 gas.