STRUCTURAL AND ELECTRICAL-PROPERTIES OF NI FILMS GROWN ON SI(100) AND SIO2 BY DC BIAS SPUTTERING

Ni films are deposited on both pure and SiO2-covered Si(100) substrates at 190-degrees-C by d.c. diode sputtering at 2.5 kV in pure Ar. A d.c. bias voltage 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-degrees-C. Film-substrate interdiffusion is observed in Ni/Si but not in Ni/SiO2. Ni adatoms diffuse preferentially along Si(111) with the formation of Ni2Si 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/SiO2. Thick columns grow at V(s) = - 80 V in both systems. The temperature coefficient of resistance, eta, is positive for both Ni/Si and Ni/SiO2. The dependences of eta on V(s) can be understood in terms of the above-mentioned structural changes with V(s).