PHYSICS OF AGEING IN THIN FILM RESISTORS: OXIDATION OF CLEAN CHROMIUM FILMS
Final scientific rept. 1 Feb 1966-31 Jan 1967
STANDARD TELECOMMUNICATION LABS LTD HARLOW (UNITED KINGDOM)
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A study was made of the oxidation of thin film resistors and its impact on the electrical film properties as an isolated process. Polycrystalline and single crystal chromium films were deposited under extremely clean conditions thus leaving mainly the various gas-metal interactions as possible degradation processes. Simultaneous measurements of resistance and surface potential as functions of oxygen uptake from atomically clean polycrystalline films up to 20 A oxide thickness distinguished between the individual oxidation stages, and it was found that the kinetics of incorporation is consistent with the surface potential and the surface structure to be rate controlling. At oxides thicker than 6 A the oxidation is governed by the Mott- Cabrera mechanism over the temperature range from below -78 C to higher than 50 C. The oxidation appears to affect the resistance merely by the reduction of the cross section of the conductive path, the effective thickness being much less than the measured mass thickness. Single crystal chromium films without detectable grain boundaries over the substrate area have been prepared on vacuum cleaved rocksalt. A reliable contacting technique has been developed and the rocksalt surface fine structure found to be compatible with meaningful electrical measurements. Preliminary measurements showed the TCR to be equal to the bulk value above room temperature.
- Physical Chemistry
- Electrical and Electronic Equipment