Structural and surface properties of NiCr thin films prepared by DC magnetron sputtering under variation of annealing conditions

NiCr thin films are widely used in several applications in microelectronics such as thin film resistors, filaments, and humidity sensors because of their relatively large resistivity, more resistant to oxidation and a low temperature coefficient of resistance (TCR). These interesting properties of NiCr thin films are dependent upon the preparation conditions including the deposition environment and subsequent annealing treatments. NiCr thin films were deposited by DC magnetron sputtering on Al2O3/Si substrate using 2-inch Ni/Cr (80/20) alloy. Annealing treatments were performed at 400, 500, and 600 °C for 6 h in air and H2 ambient, respectively. The clear crystal boundaries without crystal growth and the densification were accomplished when the pores disappeared in air ambient. Most of surfaces are oxidic including NiO, Ni2O3 and CrxOy (x = 1,2, y = 2,3) after annealing in air ambient. The crystal growth in H2 ambient was formed and stabilized by combination with each other due to the suppression of oxidized substance on the film surface. Most Ni-oxides were reduced when the Cr-oxides were present due to their stability in high-temperature H2 ambient.