Influence of Substrates on Structure Development and Concentration of Residual Impurities in Hafnium–Titanium-Oxide Films Grown by Atomic Layer Deposition

Abstract

Atomic layer deposition of hafnium−titanium-oxide (Hf x Ti 1−x O y ) films on silicon substrates and Ru, RuO 2 , and Pt seed layers was investigated. The films were grown using HfCl 4 and TiCl 4 as the metal precursors and H 2 O and O 3 as the oxygen precursors. At a temperature of 350 °C and x ≤ 0.12, tetragonal phases isomorphous with anatase-and rutile-phase TiO 2 grew on silicon and on Ru and RuO 2 , respectively. The films with 0.3 ≤ x ≤ 0.65 grown on silicon and Pt were amorphous, while those deposited on Ru and RuO 2 contained the crystal structure isomorphous with orthorhombic HfTiO 4 . Independently of substrates, the phase isomorphous with monoclinic HfO 2 was formed in the films with 0.73 ≤ x ≤ 1.0. The crystal structure influenced the concentration of chlorine impurities that was lower in crystalline films grown on Ru and RuO 2 at 350−400 °C than that in amorphous films simultaneously deposited on Si. No significant effect of substrates on the chlorine concentrations was revealed for amorphous films deposited on Si, Ru, and RuO 2 at 250 °C. The relative permittivity measured at 10 kHz for Hf x Ti 1−x O y grown on RuO 2 ranged from 21 to 90 and monotonically increased with decreasing Hf content.

Atomic Layer Deposition of Ga2O3 from GaI3 and O3: Growth of High-Density Phases

“…The most significant differences in the iodine concentrations as well as densities of the films grown on uncoated Si and on α-Cr 2 O 3 seed layers occurred at T G = 350 °C. This result was in line with earlier data showing that the substrate-controlled growth of films with higher densities led to the reduction of residual impurity concentration in the films grown by ALD. , …”

“…This result was in line with earlier data showing that the substrate-controlled growth of films with higher densities led to the reduction of residual impurity concentration in the films grown by ALD. 40,47 To understand the reasons for the differences in the growth rates obtained on α-Cr 2 O 3 seed layers and uncoated Si substrates, the dependence of Ga mass thickness (Figure 4a) and film thickness (Figure 4b) on the number of ALD cycles was studied. The films for these studies were deposited at 450 °C; as at this T G , Ga MGPC (Figure 3a) and GPC (Figure 3c) markedly depended on the presence of α-Cr 2 O 3 seed layers on the substrates as well as on the position of substrates in the reactor.…”

“…In this context, reduction of the growth temperature (T G ) leading to the in situ formation of crystalline phases seems to be a more attractive approach because the concentration of residual impurities related to the precursor ligands tends to be lower in crystalline films obtained in the deposition process than that in the films with a similar structure formed during the high-temperature annealing of amorphous films. 40 As the properties of thin films can markedly depend on the precursor combination used for ALD, one of the solutions to deposit crystalline films could be the choice of the appropriate precursors. The precursors suitable for the deposition of crystalline films should enable the self-limited ALD-type growth at sufficiently high temperatures and deposition of films with low concentrations of residual impurities.…”

“…Therefore, the investigation of the possibilities to reduce the temperature, allowing crystallization in the deposition or annealing process, should be of significant practical interest. In this context, reduction of the growth temperature ( T G ) leading to the in situ formation of crystalline phases seems to be a more attractive approach because the concentration of residual impurities related to the precursor ligands tends to be lower in crystalline films obtained in the deposition process than that in the films with a similar structure formed during the high-temperature annealing of amorphous films …”