The electrical resistance versus temperature dependence of single amorphous CrNi (40:60) thin films r.f.-sputtered in high argon pressure

Abstract

The application of thin CrNi films as resistor networks in microelectronics has generated a spate of studies designated to promote a better understanding of the relationships among the deposition conditions, film structure and resulting electrical properties [1-29]. Among the papers that had a particular significance was Campbell and Hendry's study [1] of how the electrical properties depended on CrNi alloy composition, which led to mainly restricting the choice of the thin-film resistor composition in the range from 40 to 60at% Cr. They also tried to explain the electrical properties by a macroscopic two-phase model characterized by the mixture of an oxygenfree CrNi metal phase and the Cr203 oxide phase. Most of the earlier papers dealing with CrNi thin-film resistors [2-5, 8, 9, 12, 14, 15, 22] also adopted this model to explain the electrical behaviour of asdeposited and also annealed thin films. Mooij and De Jong [6], summarizing their experimental results on triode-sputtered CrNi thin films on glass substrates at temperatures below 80 °C, noticed that: (i) in CrNi thin films the electrical resistivity is constant and the temperature coefficient of electrical resistivity (TCR) is low in the composition range 20-80% Cr, as in bulk CrNi alloys; and (ii) the electrical resistivity appears to be insensitive to changes in the crystallographic structure (£c.c., b.c.c., X phase or amorphous). In a tentative explanation of these electrical conduction properties, they have assumed that the disorder in these alloys leads to a minimum mean free path of the conduction electrons which is close to the interatomic distance. Recently, Dintner et al. [23,24] carried out measurements of the d.c. conductivity at low temperatures of NiCr-O thin films reactively sputtered under various deposition conditions. They concluded that the disorder was mainly chemical as a result of oxygen incorporation, and the d.c. conductivity at low temperatures could be interpreted in terms of weakly localized electrons and their interaction in a highly disordered metallic system. Our recent [25, 26,28] TED and TEM structural investigations performed on r.f.-sputtered CrNi (65:35, 50:50 and 20:80) thin films revealed a complex dependence of the resulting phases (single amorphous phase, two amorphous phases, nanocrystalline multiphase stable solid solutions, nanocrystalline multiphase segregated solid solutions, etc.) on the chosen deposition parameters (substrate tempera