Structural and electrical properties of Ni films grown on Si(100) and SiO 2 by d.c. bias sputtering

Abstract

Ni films are deposited on both pure and SiO 2-covered Si(100) substrates at 190 °C by d.c. diode sputtering at 2.5 kV in pure Ar. A d.c. bias volatage V s (0 to – 80 V) is applied on the substrates during the deposition. A study is made mainly of the effect of V s on the structural and electrical properties of the films by reflection high energy electron diffraction, transmission electron microscopy and resistance measurements from 30 to 135 °C. Film-substrate interdiffusion is observed in Ni/Si but not in Ni/SiO 2. Ni adatoms diffuse preferentially along Si(111) with the formation of Ni 2Si in the Si crystal. The grain size and diffusion depth of the Ni film increase with V s. A non-columnar structure with voids along the interface is induced by Ni diffusion into Si as V s ranges from 0 to – 20 V in Ni/Si whereas a slightly inclined columnar structure is induced at V s = −20 V in Ni/SiO 2. Thick columns grow at V s = −80 V in both systems. The temperature coefficient of resistance, η, is positive for both Ni/Si and Ni/SiO 2. The dependences of η on V s can be understood in terms of the above-mentioned structural changes with V s.