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 μm: 130 μm). 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 °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, H2, 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.