Polycrystalline TiN films deposited by reactive bias magnetron sputtering: Effects of ion bombardment on resputtering rates, film composition, and microstructure

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Abstract
Transmission electron microscopy, x‐ray diffraction, and Rutherford backscattering have been used to investigate the effects of ion irradiation during growth on the deposition rate, composition, and microstructure of single‐phase polycrystalline NaCl‐structure TiN x filmsdeposited by reactive magnetron sputtering with a negative substrate bias voltage V s . The layers were deposited on thermally oxidized Si(001) substrates in mixed Ar+4% N2 discharges at a total pressure of 4.2 mTorr. Varying V s between 0 and 1800 V resulted in incident ion‐to‐Ti atom flux ratios of 0.3 to 0.6 at the filmgrowth surface and increases in the substrate temperature T s (initially T s =300 °C) of 40 to 200 °C. The Ti resputtering yield increased from ≤0.02 (V s ≤100 V) to 0.30 (V s =1800 V) Ti atoms per incident ion (primarily Ar+), while the N/Ti ratio in as‐deposited films increased from 1.03 for V s =0 V to 1.12 for 100 V≤V s ≤400 V and then decreased to ≂0.95 as V s was raised to 1800 V. Trapped Ar concentrations ranged from ≤0.5 at.% (V s =0) to ≂5.5 at.% (V s =1800 V). However, the Ar was not randomly dispersed in filmsgrown with V s ≳1000 V and gas bubbles were observed. Film lattice parameters a 0 were found to vary from the bulk value of 0.4240 nm at V s =0 to a maximum of 0.4295 nm at V s =800 V and then decrease to 0.4265 nm at V s =1800 V. Voided grain boundaries were observed in filmsgrown with V s ≤120 V. The use of higher substrate biases initially resulted densification of grain boundaries with a corresponding decrease in average grain size. However, with V s ≥800 V, the films again became less dense and increased intragranular defect densities were observed.

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