Effects of annealing conditions on temperature coefficient of resistance of Pt/AlOx thin-film thermistors

• Published in: Applied physics. A, Materials science & processing Materials science & processing, 2023-02, Vol.129 (2), Article 133
• Main Authors: Dan, Atasi, Antunes, Erica F., Yung, Christopher, Tomlin, Nathan, Stephens, Michelle, Lehman, John
• Format: Article
• Language: English
• Subjects: Absorbers; Annealing; Applied physics; Blistering; Carbon; Carbon nanotubes; Characterization and Evaluation of Materials; Condensed Matter Physics; Grain size; High temperature; Interlayers; Machines; Magnetron sputtering; Manufacturing; Materials science; Nanotechnology; Optical and Electronic Materials; Physics; Physics and Astronomy; Processes; Recrystallization; Silicon dioxide; Silicon substrates; Surfaces and Interfaces; Thermistors; Thin Films
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-022-06306-1

Uncooled microbolometer arrays incorporating vertically aligned carbon nanotube absorbers are increasingly being adopted in satellite instrumentation for monitoring the Earth’s radiation budget. A key requirement for such microbolometers is a thermistor having high-temperature coefficient of resistance (TCR), low 1/ f noise while surviving high-temperature carbon nanotube growth at 800 °C. In the present work, Pt thin-film thermistors are fabricated on SiN x /SiO 2 /Si substrates using DC magnetron sputtering. To achieve enhanced adhesion of the Pt thin film, an interlayer of AlO x is deposited on the substrate via reactive high-power impulse magnetron sputtering. To maximize the positive TCR, the Pt/AlO x is subjected to different annealing conditions by varying temperature, time, and gaseous environment. With an increase in the annealing temperature and duration, Pt/AlO x thin film exhibits an improvement in TCR. Microstructural and morphological investigations suggest that improvement in TCR is related to the recrystallization of Pt and the resulting increase in grain size. A relatively high TCR of 0.308%/°C (TCR of bulk Pt = 0.359%/°C) was obtained at an operational range of 20–50 °C when Pt was annealed at 800 °C for 1 h and 3 h in air and Ar, respectively. Deposition of Pt without an AlO x interlayer resulted in thin film blistering and delamination when annealed at 800 °C for 1 h in air. A Pt/AlO x thermistor with a TCR of 0.308%/°C, annealed at 800 °C for 3 h in Ar has the potential for use in microbolometers that must undergo high-temperature growth of vertically aligned carbon nanotube absorbers.