Atomic-Layer-Deposited Alumina $(\hbox {Al}_{2}\hbox {O}_{3})$ Coating on Thin-Film Cryoresistors

Metal-alloy (Ni-Cr-Cu-Al-Ge) thin-film resistors were coated with alumina (Al₂O₃) using the atomic layer deposition (ALD) technique. The electrical properties of the thin-film resistors were studied in the temperature range of 4.2-300 K. It was experimentally demonstrated that the protective dielectric alumina coating improves the long-term stability and repeatability of high-value, thin-film resistors (100-500 kOmega). The drift rate of the resistance due to the native oxidation at room temperature was reduced from -2.45 times10^-6 h^-1 for a nonaged uncoated resistor to 0.03 times10^-6 h^-1 for an alumina-coated resistor. It was shown that the additional 15-nm-thick alumina coating does not significantly change the thermoelectrical properties of the metal-alloy, thin-film resistors.