Capacitor Characteristics of Anodized Thin-Film Hafnium

摘要

Capacitors were fabricated from anodized hafnium films previously sputtered onto glass slides. The sputtering rate was 108 A/min. Anodization was accomplished at 46 volts, the electrolyte being 0.5 N. aqueous ammonium sulphate and the anodization rate 57 A/V. The counter electrode was vacuum-deposited gold. Variations in the anodic technique caused little or no improvement in capacitor characteristics. Characteristics found were: K = 50, capacitance = 1.1 microfarads/sq in, dissipation factor = 1.3%, TCC = 200 ppm/C, voltage breakdown = 75% of fermation voltage, and current leakage = 3.0 to 4.5 x 10 to the minus 8th power amps/sq in at the knee formed at 18 V. The insulation resistance at 18 V was 2.0 to 3.0 x 10 to the 10th power ohms (1.0 to 1.5 x 10 to the 8th power ohms/sq in). There are indications that the films are relatively non-polar. There is a 'wicking' of electrolyte during the anodization process.