Gas pressure dependence of composition in Ta–Ti–N films prepared by pulsed high energy density plasma

Tantalum titanium nitride (Ta–Ti–N) films were deposited on silicon wafer substrates by pulsed high energy density plasma (PHEDP), under different intake gas pressures, ranging from 0.1 to 0.4 MPa. The films were investigated by X-ray photoelectron spectroscopy. Results were analyzed in detail, which reveals that the contents of the metallic elements (Ta and Ti) tend to decrease with pressure, while that of nitrogen increases as expected. With increasing pressure, the films can be denoted as TaTi3.9N2.8, TaTi4.7N6.0, TaTi2.2N8.4 and TaTi3.1N13.5, respectively. The bonding state of tantalum, titanium, as well as nitrogen was fitted and discussed. Our results demonstrate that almost all the titanium bonded with nitrogen. The Ta–N and Ti–N bonds have equal shares under low gas intake pressure, while the Ti–N bonds prevail under high pressure. The preferential sputtering between the coaxial electrodes should be responsible for this phenomenon. Under low nitrogen pressure, the preferential sputtering is quite significant; while it could be neglected under high pressure.