Formation and investigation of characteristics of thermoresistive structures based on vanadium oxide films

Abstract

The processes of reactive magnetron sputtering of a V target in Ar/O2 gas mixture are investigated. It was found that when using a pulsed current for sputtering and a pressure in the chamber less than 0.06 Pa, the intensities of the emission lines of vanadium at 437.922 nm, argon at 750.386 nm, and oxygen at 777.417 nm with a change in the oxygen concentration in Ar/O2 gas mixtures (ГO2) have no hysteresis and unambiguously depend on the parameters of the sputtering process, which makes it possible to stabilize the process without using feedback systems. By monitoring the sputtering process by optical emission spectroscopy and depositing films on a rotating substrate of diameter 100 mm, vanadium oxide (VOx) films with nonuniformity thickness less than ±2.4 % and surface resistance less than ±2.5 % were obtained. Studies by transmission line method of the influence of the parameters of the reactive magnetron sputtering and subsequent annealing at O2 pressure of 0.04 Pa on the characteristics of thermoresistive structures based on VOx films showed that when the contacts are deposited without ion cleaning, the current-voltage characteristics (IV) and the dependence of the resistance on the length of resistors R(L) are nonlinear, which indicates the presence of a potential barrier in the contacts. Preliminary ion cleaning can significantly improve the linearity of the IV characteristic. The most linear IV characteristics were obtained for Ti contacts. However, the specific contact resistance of the VOx/Ti contact increases with an increase in the oxidation state of the VOx films and reaches ρc = 0.1 Ohm·m2 at the specific resistance of vanadium oxide ρ = 0.1 Ohm·m. The analysis of the dependences of the temperature coefficient of resistance (TCR) and ρ of VOx films on the annealing temperature showed that, upon annealing, ρ and TCR slightly decrease, i. e. there occurs a partial deoxidation of the films. However, unlike annealing at atmospheric pressure, there are no temperature regions at which a sharp decrease in the resistivity and TCR occurs.

Keywords

• vanadium oxide
• microbolometer
• thermoresistive structure
• reactive magnetron sputtering
• annealing
• contact resistance