Toshie Suzuki

Using tetrakis-diethylamido-hafnium for HfO2 thin-film growth in low-pressure chemical vapor deposition

Abstract We synthesized very pure tetrakis-diethylamido-hafnium {Hf[N(C 2 H 5 ) 2 ] 4 :Hf(NEt 2 ) 4 } that can be used as a precursor for depositing Hf-related materials in chemical vapor deposition (CVD). Hf(NEt 2 ) 4 is liquid at room temperature and has a moderate vapor pressure (1 torr at 80 °C). It is stable, and not pyrophoric in the air. HfO 2 film was deposited by low-pressure CVD using the Hf(NEt 2 ) 4 /O 2 gas system. The amounts of residual N and C in the deposited film were decreased when the substrate temperature was increased. Increasing the temperature also improved the step coverage quality of the film deposited on the substrate with a trench. When the film was deposited with Hf(NEt 2 ) 4 and O 2 at 450 °C, the resulting stoichiometric HfO 2 film is polycrystalline with a low impurity concentration and has good step-coverage quality.

Hf1-xSixO2 deposition by metal organic chemical vapor deposition using the Hf(NEt2)4/SiH(NEt2)3/O2 gas system

Abstract Hf1−xSixO2 thin film was deposited on a Si substrate by low pressure chemical vapor deposition using the tetrakis-diethylamido-hafnium {Hf[N(C2H5)2]4}/Tris–diethylamino-silane {SiH[N(C2H5)2]3}/O2 gas system. During the HfO2 deposition, SiH[N(C2H5)]3 vapor was injected and Hf1−xSixO2 film was deposited. By increasing the amount of the supplied SiH[N(C2H5)2]3, the ratio of Si to Hf in the film increased and the refractive index of the film decreased. While the deposited HfO2 film was polycrystalline, Hf1−xSixO2 was amorphous. The step-coverage quality was slightly degraded as a result of the SiH[N(C2H5)2]3 injection. No residual C was detected in the film by XPS measurement indicating that the residual C amount was less than 1%. On the other hand, the amount of residual N increased with an increase in the supply of SiH[N(C2H5)2]3.

Effects of deposition conditions on step-coverage quality in low-pressure chemical vapor deposition of HfO2

Abstract Hafnium dioxide thin film is deposited on a Si substrate with trenches by LPCVD using the Hf(NEt2)4/O2 gas system. When the deposition temperature is 300°C, poor-quality step-coverage is obtained. The step-coverage quality improves as the deposition temperature increases, and the good-quality step coverage is achieved at 450°C. By analyzing the profile of the film thickness in the trench, it is suggested that there are at least two types of important reactants that contribute to the film deposition. One is an active reactant. The contribution of this adsorbate to the film deposition decreases as the substrate temperature increases. On the other hand, the other reactant is a slightly active reactant. When a film is deposited at 450°C, most of the film is deposited from this slightly active adsorbate and good-quality step coverage is obtained.

MOCVD precursors for Ta- and Hf-compound films

We synthesized diethylamido tantalum (EtN=Ta(NEt2)3+Ta(NEt2)4) and diethylamido hafnium (Hf(NEt2)4), using nearly identical methods, as precursors for Ta- and Hf-compound films. Both precursors were liquid at room temperature and had vapor pressure (Ta: 6 Torr at 601C, Hf: 7.5 Torr at 801C) moderate enough for chemical vapor deposition (CVD). We deposited TaN thin films from diethylamido Ta and HfO2 thin films from Hf(NEt2)4/O2 using metal-organic CVD. The TaN films were amorphous and the HfO2 films were polycrystalline. Both types had goodquality step coverage. r 2002 Elsevier Science B.V. All rights reserved.

Preparation of SrBi 2 Ta 2 O 9 Thin Films by Liquid-Delivery MOCVD Without Additional Solvents

SrBi 2 Ta 2 O 9 thin films were prepared by ECR plasma enhanced metalorganic chemical vapor deposition (ECR-MOCVD) with a liquid-delivery system using one cocktail source without an additional solvent. The strontium-tantalum double alkoxide, Sr{Ta[OC 2 H 4 H(CH 3 ) 2 ](OC 2 H 5 ) 5 } 2 , was dissolved in stabilized trimethyl bismuth, Bi(CH 3 ) 3 / dioxane. This source system has been used in a conventional bubbling system. Deposition rate and the composition of the films were strictly controlled by the concentration and the composition of the cocktail source. Therefore, high reproducibility was realized by using this system. The constituent phase of the stoichiometric SBT film as-deposited at 500 C on a (111)Pt/TiO 2 /SiO 2 /Si substrate was a fluorite phase and transformed to the single phase of SBT by the post annealing at 800 C. It showed almost the same ferroelectricity as the stoichiometric composition film.