Morphology and crystallization kinetics in HfO2 thin films grown by atomic layer deposition

Abstract

We report the effects of annealing on the morphology and crystallization kinetics for the high-gate dielectric replacement candidate hafnium oxide (HfO 2 ). HfO 2 films were grown by atomic layer deposition ͑ALD͒ on thermal and chemical SiO 2 underlayers. High-sensitivity x-ray diffractometry shows that the as-deposited ALD HfO 2 films on thermal oxide are polycrystalline, containing both monoclinic and either tetragonal or orthorhombic phases with an average grain size of ϳ8.0 nm. Transmission electron microscopy shows a columnar grain structure. The monoclinic phase predominates as the annealing temperature and time increase, with the grain size reaching ϳ11.0 nm after annealing at 900°C for 24 h. The crystallized fraction of the film has a strong dependence on annealing temperature but not annealing time, indicating thermally activated grain growth. As-deposited ALD HfO 2 films on chemical oxide underlayers are amorphous, but show strong signatures of ordering at a subnanometer level in Z-contrast scanning transmission electron microscopy and fluctuation electron microscopy. These films show the same crystallization kinetics as the films on thermal oxide upon annealing.

Applications of high throughput (combinatorial) methodologies to electronic, magnetic, optical, and energy-related materials

“…Non-combinatorial studies of HfO 2 (Ref. 45) and the HfO 2 -Al 2 O 3 (Ref. 46) system are in agreement with the basic finding of cubic and monoclinic phases, and the fact that Al 2 O 3 addition stabilizes the amorphous phase.…”

“…They found that the conductivities of a series of ternary alloys along the line Mn 0. 45 Further research used PLD to deposit CCS libraries of Nb-Sn-Ti-O. 214 Their results showed that films with Sn levels less than 20 at% maintained low resistivity and high transparency, while reducing the refractivity of the coating (a reduction in the refractivity reduces the effective path length of light through a material, thus reducing the probability of absorption).…”

Preparation of hafnium oxide thin films by sol–gel method

“…As can be seen, distinct diffraction peaks can be observed, and these diffraction peaks are ascribed to the monoclinic phase of HfO 2 [12]. A peak ascribed to either tetragonal or orthorhombic HfO 2 , often appearing at 2θ=30.3°in HfO 2 films deposited by atomic layer deposition and sputtering [13][14][15][16], was not detected in this study. The HfO 2 films, therefore, mainly crystallized in the monoclinic phase without the tetragonal or orthorhombic phase.…”

Crystalline phases, microstructures and electrical properties of hafnium oxide films deposited by sol–gel method

“…As can be seen, distinct diffraction peaks can be observed, and these diffraction peaks are ascribed to the monoclinic phase of HfO 2 [13]. A peak ascribed to either tetragonal or orthorhombic HfO 2 , often appearing at 2y ¼ 30:31 in HfO 2 films deposited by ALD and sputtering [14][15][16][17], was not detected in this study. The HfO 2 films, therefore, mainly crystallized in the monoclinic phase without the tetragonal or orthorhombic phase.…”