Application of non-linear optical second harmonic generation and X-ray absorption and spectroscopies to defect related properties of Hf silicate and Hf Si oxynitride gate dielectrics

Three different Hf oxide based dielectrics have emerged as viable candidates for applications in advanced ULSI devices. This article focuses on two of these: (i) phase separated Hf silicates with (i) 70-85% nano-crystalline HfO₂ with a nano-grain size <2 nm, and 15-30% ∼2 nm non-crystalline SiO₂ inclusions, and (ii) Hf Si oxynitride alloys, the most promising of which has a composition, (HfO₂)_0.3(SiO₂)_0.3(Si₃N₄)_0.4 designated as 3/3/4 Hf SiON. X-ray absorption spectroscopy has been applied to identification of defect associated with vacancy structures in phase separated silicates, and network disruption defects in the Hf Si oxynitrides. Optical second harmonic generation is introduced in this article for the first time as a non-invasive approach for detecting macroscopic strain, that is shown to be absent in these low defect density dielectrics, the phase separated Hf silicates, and Hf Si oxynitrides, but present in HfO₂ films, and Hf silicates with lower HfO₂ content, e.g., the 40% HfO₂ film of this article.