Abstract
The crystallization behavior and electrical resistivity of WSix films (coevaporated on poly-Si on Si02) with x ranging from 1.0 to 2.4 were examined in a high-resolution TEM before and after annealing at 1000 °C. The amorphous as-deposited films with high resistivities (up to 650/jfl cm) become crystalline WSi2 after annealing accompanied by a precipitous drop in resistivity to values below 30/xfl cm. The as-deposited Si-rich films showed a reduction in thickness, up to — 15% for x = 2.4, while metal-rich films showed an increased thickness, up to 13% for x = 1.0. The minimum resistivity of 28 μΩ cm was found in a sample with as-deposited composition of WSij 4which also had the largest thickness. The difficult problem of determining the thicknesses before and after the interaction of WSix with the CVD poly-Si was solved by first measuring the thin Si02thickness (220 A) using the Si lattice fringes, and then comparing the thicknesses of poly-Si and WSix with that of Si02. Annealed WSix films with thickness ranging from 1200 to 2500 A showed one to two grains per film thickness for an as-deposited x — 2.4 to 1.4. The grain size appeared smaller (three to four grains per thickness) for x < 1.4. For a film with x = 1.0, W5Si3and WSi2were identified by electron diffraction. The density of annealed films was determined by counting the number of atoms per cm2 by Rutherford backscattering spectrometry, and it ranged from 11 to 12.5 g/cm3. © 1985, American Vacuum Society. All rights reserved.