Atomic Layer Deposition of Praseodymium Aluminum Oxide for Electrical Applications

Praseodymium aluminum oxide (PAO) thin films were grown by atomic layer deposition (ALD) from a new precursor, tris(N,N′-diisopropylacetamidinato) praseodymium, (Pr(amd)3), trimethylaluminum (TMA), and water. Smooth, amorphous films having varying compositions of the general formula PrxAl2–xO3 were deposited on HF-last silicon and analyzed for physical and electrical characteristics. The films were pure according to Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS). The permittivity of the thin film with the stoichiometry of Pr1.15Al0.85O3 was 18, and all annealed films displayed very low leakage currents compared to other high-k oxide films deposited using ALD. A leakage current density of 1.1 × 10 A cm was achieved for a PAO film with an equivalent oxide thickness of 1.46 nm. Annealed films also displayed nearly zero flat-band voltage shifts and low hysteresis (< 10 mV). The optimal growth parameters and electrical properties were achieved with Pr1.15Al0.85O3. Atomic force microscopy (AFM) determined that high temperature annealing (850 °C) had no effect on the smoothness of the films (rms of 0.17 nm).