Microstructure modification of TiN by ion bombardment during reactive sputter deposition

Abstract

Cross-sectional transmission electron microscopy has been used to investigate the effects of low energy (400 eV or less) ion irradiation during the growth of reactively sputtered TiN at temperatures between 300 and 900 °C. The films were deposited on high speed steel substrates in mixed ArN 2 discharges using an applied negative substrate bias voltage V s to vary the energy of impinging ions. The arrival rate ratio between ions and titanium atoms increased from 0.3 to 0.4 as V s was increased from 40 to 400 V. Films grown with V s ⩽ 200 V exhibited a columnar-like microstructure with a mixed (200)–(220) preferred orientation and the average column size increased with increasing T s . Both the width of the columns and the defect number density within each column were also influenced by ion bombardment. Raising V s above about 200 V resulted in a loss of preferred orientation together with an increasing dissolution of the columnar boundaries due to continuous renucleation during growth. Defect number densities in multilayer films were observed to vary abruptly and reversibly with changes in V s atall growth temperatures.