Influences of aluminum doping on the microstructures and electrical properties of tantalum nitride thin films before and after annealing

Ta-N-Al thin films were produced by reactive sputtering with two different TaAl alloys (Al 10 at.% and 20 at.%) for use as resistive materials for thin film chip resistors. Changing the N2 gas flow of the N2/Ar plasma and the Al ratio in TaAl alloy resulted in different microstructures and electrical properties of the Ta-N-Al thin film. The resistivity of the thin film sputtered by TaAl (Al 20 at.%) alloy was 1.23 times that sputtered by Ta under 20% N2/Ar. After deposition, rapid thermal processing was applied to anneal the thin films for 5 min at 600 degrees C, 650 degrees C, and 700 degrees C under N2 (99.995%) atmosphere, causing the Ta2N and TaN crystalline phase formation. Al in Ta-N-Al was observed to hinder Ta2N and TaN crystalline phase formation during annealing. It is crucial to dope Al ith Ta-N appropriately to obtain a near-zero temperature coefficient of resistance (TCR) after annealing. The TCR of Ta-N-Al thin film, sputtered by TaAl (Al 20 at.%) alloy, was substantially affected by the annealing temperature. However, the thin film sputtered by TaAl (Al 10 at.%) alloy under 16% N2/Ar can achieve a TCR of -1.8 ppm/degrees C and 1.4 ppm/degrees C after annealing at 600 degrees C and 650 degrees C, respectively.