Effect of substrate bias on the protective properties of TiN films grown by reactive magnetron sputtering onto Cu substrates

Abstract

Films of TiN with a thickness of 120 nm were deposited onto Cu substrates by reactive magnetron sputtering. In order to vary the structure of the as-deposited films they were grown without and with an applied negative substrate bias V s. In the latter case a negative bias of 400 V was used giving an ion current density of 0.4 mA cm −2. The as-deposited films were stoichiometric for both growth conditions as determined by quantitative Auger electron spectroscopy (AES). Transmission electron microscopy showed that the unbiased films had an open columnar structure with voids present at the column boundaries whereas the biased films showed a completely dense structure although columnar. Also the protective properties of the two types of films were drastically different. AES depth profiles showed that during annealing experiments at 600 and 700°C an extensive Cu diffusion occurred in the unbiased films giving rise to a Cu covered surface after 2 h at 600°C. For the films grown with a substrate bias only a very limited amount of Cu diffusion into the TiN films occurred under the same annealing conditions.