Improved electrical and thermal properties of nickel silicides by using a NiCo interlayer

Abstract

We have investigated the effects of a NiCo interlayer on the electrical and thermal properties of nickel silicide as a function of the annealing temperature. For the interlayered samples, 3 nm-thick NiCo(10 at.% Co) films are electron-beam evaporated on Si substrates, on which 27 rim-thick Ni films are deposited without breaking the vacuum. it is shown that all the samples exhibit a distinctive increase in the sheet resistance at temperatures above 900 degrees C. However, the NiCo interlayer sample produces the lowest sheet resistance at 900 degrees C. X-ray diffraction results show that the Ni only and NiCo interlayer samples produce NiSi and NiSi2 phases, while NiCo full samples give NiSi and Ni1-xOxSi2 phases. Scanning electron microscopy results exhibit that for all the samples, the surfaces become degraded with numerous arbitrarily-shaped spots, corresponding to areas uncovered by the silicides. The areal fractions of the silicides for the Ni only, NiCo full, and NiCo interlayer samples are about 57%, 72%, and 81%, respectively. The temperature dependence of the electrical properties of the silicide samples is explained in terms of the formation of resistive phases and the agglomeration of the silicide. (C) 2009 Elsevier Ltd. All rights reserved.