Jin-Hyock Kim

Modified atomic layer deposition of RuO2 thin films for capacitor electrodes

The authors investigated the modified atomic layer deposition (ALD) of RuO2 films using bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp)2] at a deposition temperature of 265°C. Oxygen gas diluted with argon was supplied throughout all of the ALD steps. The growth rate of the modified ALD RuO2 was about 1.4A∕cycle, which is higher than that of conventional Ru ALD due to the increase in the amount of Ru(EtCp)2 adsorption per cycle, as well as the difference in the unit cell volumes of Ru and RuO2. The film thickness increased linearly with the number of cycles, and the incubation cycle in the initial stage was negligible.

Initial stages of ruthenium film growth in plasma-enhanced atomic layer deposition

The initial stages of ruthenium film growth in plasma-enhanced atomic layer deposition (PEALD) on titanium nitride (TiN) substrate were investigated in detail. During the initial stages of ruthenium film growth, the influence of the substrate surface was significant and controlling thickness by counting the number of deposition cycles is no longer valid. The time required for saturated adsorption of Ru(EtCp) 2 as well as the amount of deposited ruthenium atoms per cycle changed during the initial stage. The time required for saturated adsorption of Ru(EtCp) 2 on homogeneous ruthenium surfaces was 7 s. However, it increased up to 25 s during the initial stage of the ruthenium film growth where the film growth on heterogeneous TiN substrate is dominant. By considering these changes during the initial stages of ruthenium PEALD growth, the full coverage of PEALD ruthenium can be obtained at a minimum thickness of 2.7 nm.

Step coverage modeling of thin films in atomic layer deposition

A film growth model on microfeatures is proposed to evaluate step coverage depending on precursor injection time in atomic layer deposition. The proposed model is based on that the chemisorption rate of precursors at a certain position along the depth of a microfeature is determined by the total flux of precursors and the sticking probability. The total flux includes the flux coming from the entrance of a microfeature and the flux reflected from other positions inside a microfeature, and the sticking probability depends on the surface coverage of chemisorbed precursor, which is a function of precursor injection time. The proposed model was applied to the deposition of Al2O3 films on 0.3μm diameter holes with an aspect ratio of 10. It was confirmed that the experimental data for step coverage depending on precursor injection time follow the trend predicted by the proposed model.

Applicability of Step-Coverage Modeling to TiO2 Thin Films in Atomic Layer Deposition

The applicability of a step-coverage model in atomic layer deposition was extended to the deposition of TiO 2 films, focusing on the effect of a precursor partial pressure and a deposition temperature, as well as the number of cycles in step coverage. Using the extracted model parameters, step coverage depending on the number of cycles was predicted, which shows a nonlinear dependence of film thickness inside a hole on the number of cycles because the area of a hole entrance decreases as the deposition proceeds. The experimental data agreed well with the model predictions. To confirm the validity of the step-coverage model, the effect of a precursor partial pressure and a deposition temperature on step coverage was also investigated. The flux of precursors that strikes the flat surface is the model parameter related to a precursor partial pressure, and the initial sticking probability and the adsorption order are the model parameters related to a deposition temperature. For different experimental conditions, by obtaining the model parameters related to changed experimental conditions from the experimental data at the flat surface, film thickness per cycle at the bottom inside a hole depending on precursor injection time could be predicted within reasonable accuracy.

Increment of dielectric properties of SrTiO3 thin films by SrO interlayer on Ru bottom electrodes

SrTiO3 thin films were deposited on Ru using plasma-enhanced atomic layer deposition with and without a SrO interlayer. When the SrTiO3 films were deposited on Ru directly, the dielectric constants of the films decreased abruptly from 65 to 16 as the thickness fell below 20nm. This change was related to film crystallinity. Conversely, when a seed layer was prepared by depositing 2.7nm SrO and postannealing before SrTiO3 deposition, the crystallinity of the SrTiO3 films was enhanced and the thickness dependency of the dielectric constant was reduced. As a result, the dielectric constant of 10nm SrTiO3 films was improved from 16 to 50.

Development of New TiN/ZrO2/Al2O3/ZrO2/TiN Capacitors Extendable to 45nm Generation DRAMs Replacing HfO2 Based Dielectrics

New ZrO₂/Al₂O₃/ZrO₂ (ZAZ) dielectric film was theoretically designed and successfully demonstrated to be applicable to 45nm DRAM devices. ZAZ dielectric film is a combined structure from tetragonal ZrO₂ and amorphous Al ₂O₃. Thus prepared ZAZ TFT capacitors showed very small Tox.eq value of 6.3Aring and low leakage current less than 1fA/cell. It was also confirmed that ZAZ TFT capacitor was thermally robust during backend full thermal process by applying it to the final DRAM product in mass production

Effect of crystallinity and nonstoichiometric region on dielectric properties of SrTiO3 films formed on Ru

The dielectric constant depending on the film thickness for SrTiO3 films formed on Ru was investigated after an annealing step at 600°C, which shows that the dielectric constant increased abruptly with the film thickness up to 20nm and then increased slightly, remaining relatively constant at a value of about 65. The abrupt increase was due to the crystallinity of SrTiO3 films. On the other hand, the slight increase was related to the existence of nonstoichiometric region near the interface of SrTiO3 film and Ru, which was intermixed with SrTiO3 and Ti–O phases having an equivalent oxide thickness over 0.32nm.

Theoretical Simulation of Surface Evolution Using the Random Deposition and Surface Relaxation for Metal Oxide Film in Atomic Layer Deposition

Atomic layer deposition (ALD) has become an essential deposition method for forming nanometer scale thin films in the microelectronics industry, and its applications have been extended to multi-component thin films, as well as to single metal oxide films. In order to investigate the development of the surface structure of ultra-thin film qualitatively as well as quantitatively, ALD processes are simulated with a molecular scale. For this simulation, the film materials are deposited on a imaginary substrate that consists of small lattice. The deposition behaviors are described by using random deposition (RD) model or random deposition with surface relaxation (RDSR) model as the ALD growth mode, and the proposed model was applied to the deposition of SrO-TiO 2 thin films. Through this work, growth characteristics such as surface morphology, deposited film coverage can be predicted.

Change in the resistivity of Ge-doped Sb phase change thin films grown by chemical vapor deposition according to their microstructures

This study examined the effects of the composition and microstructure on the electric resistivity of Ge-doped Sb phase change thin films grown by cyclic plasma enhanced chemical vapor deposition. Ge and Sb layers were deposited sequentially to form either a GexSby mixture or Ge/Sb nanolaminated films. While the resistivity of the nanolaminated films was higher, the GexSby mixture showed a lower resistivity than the pure Sb film. This can be explained by the increase in carrier density of the alloy, as confirmed by first-principles calculations. An abrupt change in resistance accompanying a phase change was observed at ∼210 °C.