Magnetron sputtering of TiAlN films for inkjet printhead resistors

Heat resistors in thermal inkjet printheads require a low temperature coefficient of resistance (TCR) and good oxidation resistance. Titanium aluminum nitride (TiAlN) films, which have a lower TCR and better oxidation resistance than the conventional TaN and TaAl films, were deposited on a Si(100) substrate at 400 °C by radio frequency (RF) magnetron cosputtering using TiN and AlN ceramic targets. This study investigates the effect of N ₂ flow rates on the TCR and the oxidation resistance of the TiAlN films. The best TCR value was -390.35 ppm/k and the lowest sheet resistivity change was 31%. These results were obtained with high a N2 flowing of 10%, and discussed from the microstructural and stoichiometric viewpoints. The grain-size and surface-roughness decreased with the increasing N ₂ flow rate, thus resulting in small grains. When the N2 flow rate was as high as 10%, the Ti 2p, Al 2p, and N 1s orbital electron binding energies from XPS analyses showed that the nitrogen content in the TiAlN films exceeded the stoichiometry. The small grains and excess nitrogen made the film's sheet resistance higher, within a relevant range, and provided low TCR and high oxidation resistance.