Properties of Low Anodization Voltage Thin-Film Capacitors Based onalpha-Ta with Nitrogen Concentrations Between 14 and 30 Atomic Percent

Tantalum oxide thin-film capacitors have been made with capacitance densities up to about a factor of three greater than those currently used for the fabrication of precision resistor-capacitor (RC) filters based on nitrogen-doped Ta films. This is accomplished by decreasing the dielectric thickness via reduction of the anodization voltage from 190 V to as low as 70 V. The dissipation factor, temperature coefficient of capacitance, and dc leakage current, after appropriate heat treatment, are only slightly higher than those of capacitors anodized at 190 V; however, the effects of nitrogen concentration in the alpha-Ta films become more significant. In addition, the expected long-term aging (20 years, 65°C) of capacitors anodized to either 90 V or 190 V is about equivalent.