Thin-Film Capacitors Made from TaN Films

Thin-film capacitors were prepared from sputtered tantalum nitride thin films (TaN capacitors). The dielectric was formed by anodic oxidation and the counterelectrode was deposited by evaporation of nichrome-gold. The TaN capacitors excelled the usual TM capacitors in various properties. The temperature coefficient of capacitance was 129 ppm/°C and the dissipation factor was 0.0014 at 1 kHz. In addition, TaN capacitors showed high endurance to heat treatment. The capacitance change was only -0.02 percent after 350°C heat treatment for 2 minutes. Reliability tests were performed which indicated a failure rate of 0.1 FIT at 40°C, 6 V. The capacitance change was within ±0.4 percent after 3000 hours at 125°C. The TaN capacitors were applied to make highly stable and highly precise filter circuits such as multifrequency receivers for touch tone telephones now in commercial use.