Hafnium Nitride(x): Phase Composition, Microstructure, and Physical Properties of Epitaxial and Polycrystalline Layers
The phase-compositions obtained in HfNx grown on SiO 2 at 350°C are alpha-Hf:N (x ≤ 0.6); multiphases (0.6 ≤ x ≤ 0.9); delta-HfN single-phase (0.9 ≤ x ≤ 1.3); and mixtures of delta-HfN and higher nitrides (x ≥ 1.3). HfNx layers with 0.9 ≤ x ≤ 1.2 grown under mild ion-irradiation are underdense with mixed orientation, low in-plane stress, and rough surfaces due to limited adatom mobilities resulting in kinetic roughening during film growth. However, the use of intense ion-irradiation leads to dense HfNx layers with 111 texture, compressive in-plane stress, and smooth surfaces due to enhanced adatom surface mobilities and thus, lower electrical resistivity and higher hardness are obtained. For HfNx layers with 1.2 ≤ x ≤ 1.6, the correspondingly higher steady state atomic N surface coverages during deposition alter growth kinetics in favor of 001 texture with a fully dense structure and compressive in-plane stress.
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