Effect of Substrate Temperature on Temperature Sensitivity and Magnetoresistance of CrOxNy Thin Film Cryogenic Sensor

The demand for high-precision temperature measurement is expanding into the fields of deep low-temperature and strong magnetic field, and CrOxNy thin film sensor has shown good prospects in these fields for its high sensitivities, high thermal cycling stability, and low magnetoresistance. The substrate temperature, as an important parameter in the thin film growth process, plays an important regulatory role in sensor performance, which has not been systematically studied in the preparation process of CrOxNy thin film cryogenic sensor. Here, CrOxNy thin films were deposited on polished and oxidized silicon wafers at different substrate temperatures (100 ° C ~ 400 °C) by dc magnetron reactive sputtering. The crystal structure and composition of the thin film were characterized by X-ray Diffractometer and X-ray Photon-electron Spectroscopy. Then, CrOxNy thin film temperature sensors were fabricated using micro-electromechanical system (MEMS) micromachining process. The performance tests show that the sensor with higher substrate temperature has lower temperature sensitivity, smaller magnetoresistance effect under 0\sim 9 T magnetic field in 4\sim 300 K, and relatively smaller temperature measurement deviation in the low temperature region (below ~100 K), whereas the sensor with lower substrate temperature has the opposite trend. CrOxNy thin film sensors prepared at 400 ° C substrate temperature exhibit more accurate deep cryogenic measurement capabilities under strong magnetic field. This study will provide guidance for the preparation of high-precision cryogenic temperature sensors applied to deep low-temperature and strong magnetic field.