Influence of the nitrogen partial pressure on the properties of d.c.-sputtered titanium and titanium nitride films

The properties of titanium and titanium nitride films deposited onto biased substrates in a d.c. sputtering system were studied as a function of the partial nitrogen pressure. The deposition rate was deduced from film thickness measurements. The film composition was determined by Rutherford backscattering analysis and the structure was studied using X-ray diffraction. The resistivity was measured by the four-probe method and the temperature coefficient of resistivity (TCR) was determined in the temperature range from −196 to 25 °C. Around a critical nitrogen pressure p c of 4 × 10 -2 Pa the deposition rate decreases rapidly, the film structure changes from h.c.p. titanium to nearly stoichiometric f.c.c. TiN. At the same pressure, the film resistivity and the TCR present minimum values. A general sputtering model which takes into account the gettering action of the deposited material is proposed. This model allows the calculation of the surface coverage of the target by the reactive gas or the metallic compound and the determination of the deposition rate as a function of the reactive partial pressure. A good agreement is found with the deposition rates measured experimentally.