Seok-Jun Won

Plasma-Enhanced Atomic Layer Deposition of TiO2 and Al-Doped TiO2 Films Using N2O and O2 Reactants

Rutile-structured TiO 2 and Al-doped TiO 2 dielectric thin films were grown on a sputtered Ru electrode by atomic layer deposition (ALD) using O 2 - or N 2 O-plasma oxidants. The O 2 -plasma-based ALD process produced films with a similar growth rate and electrical performance to those deposited using the 0 3 -oxidant-based ALD process, which has been reported previously [S.K. Kim et al., Appl. Phys. Lett., 85, 4112 (2004); S. K. Kim et a]., Chem. Mater., 20, 3723 (2008)]. In contrast, the N 2 O-plasma-based ALD process resulted in a 1.8 times higher growth rate than that of the 0 3 -oxidant-based ALD process with identical electrical performance. Denser and uniform oxidation of Ru is essential for achieving pure rutile TiO 2 films with a higher dielectric constant (up to 100) on Ru electrodes.

High-Quality Low-Temperature Silicon Oxide by Plasma-Enhanced Atomic Layer Deposition Using a Metal–Organic Silicon Precursor and Oxygen Radical

Recently, SiO2 grown at low temperatures has been highlighted for a range of applications. In this letter, SiO2 films were deposited at 280°C by plasma-enhanced atomic layer deposition (ALD) using bis-diethylamino-silane and O2 plasma. The electrical conduction mechanisms of a 38-nm-thick SiO2 film were found to be ohmic and Fowler-Nordheim tunneling in the low- and high-voltage ranges, respectively. The electrical breakdown field of the silicon oxide films was measured at ~10 MV/cm. The excellent breakdown field was well explained by the fact that ALD SiO2 has very low carbon content (<; 0.5%) and does not have any oxygen deficiency and nonbridging oxygen. Compared to wet SiO2, the increase in etch rates was attributed to the existence of strained bonds.

Improving the Morphological and Optical Properties of Sputtered Indium Tin Oxide Thin Films by Adopting Ultralow-Pressure Sputtering

cm were also achieved using a continuous two-step depositionprocess, in which the initial layer was deposited using ULPS and then the final layer was deposited with a SP of 6.7 −110 Pa,without the use of any other additional steps. Both the ULPS and continuous two-step deposition methods were found to beeffective for producing ITO thin films with enhanced morphologies that make them suitable for use in display devices.© 2008 The Electrochemical Society. DOI: 10.1149/1.3005562 All rights reserved.Manuscript submitted June 26, 2008; revised manuscript received September 3, 2008. Published November 5, 2008.

The Role of the Methyl and Hydroxyl Groups of Low-k Dielectric Films on the Nucleation of Ruthenium by ALD

Nucleation of the ruthenium (Ru) precursor on low-k film surfaces during atomic layer deposition (ALD) of Ru was investigated. The adsorption tendency of the precursor decreased with increasing concentration of methyl groups on the low-k film surface, resulting in poor nucleation of Ru. The electron-deficient hydroxyl groups act as preferential adsorption sites for the electron-rich ligands of the aromatic Ru precursor through the formation of π-bonds. This leads to the enhanced nucleation of Ru. The roles of the functional groups were corroborated by silylation experiments.

Growth and electrical properties of silicon oxide grown by atomic layer deposition using Bis(ethyl-methyl-amino)silane and ozone

Silicon oxide thin film grown at low temperatures (<300–500 °C) is essential for a range of applications in semiconductor devices. In this study, silicon oxide films were deposited at a substrate temperature of ∼300 °C by an atomic layer deposition (ALD) process using Bis(ethyl-methyl-amino)silane (BEMAS). BEMAS precursors adsorbed on the growing surface reacted with ozone but not with H2O. This suggests that the Si–H bonds in the BEMAS precursors adsorbed on the surface are robust and could be cleaved only by ozone. The reaction using BEMAS and ozone exhibited ALD saturation behavior. The dielectric constant of the ALD-SiO2 was measured to be ∼9, which is 2.3 times higher than that (∼3.9) of normal amorphous SiO2. This was attributed to the existence of the ∼10% OH species in the film.

Effect of Catalyst Layer Density and Growth Temperature in Rapid Atomic Layer Deposition of Silica Using Tris(tert-pentoxy)silanol

Rapid atomic layer deposition (RALD) of SiO₂ thin films was achieved using trimethyl-aluminum and tris(tert-pentoxy)silanol (TPS) as the catalyst and Si precursor, respectively. A maximum growth rate as high as ∼28 nm/cycle was obtained by optimizing the catalyst layer density, whereas the previous reports showed lower values of 12 to 17 nm/cycle [Hausmann et al. Science2002, 298, 402-406; Burton et al. Chem. Mater. 2008, 20, 7031-7043]. When the growth temperature was increased from 140 to 230 °C, the growth rate was not much reduced and the TPS pulse time showing a saturated growth rate became rather longer. Si-CH₃, Si-OH, and Si-H bonds were not detected in infrared spectra from the RALD SiO₂ film grown at 230 °C. The film quality could be enhanced substantially by applying a higher growth temperature and an in situ post plasma treatment process.

Capacitance and Interface Analysis of Transparent Analog Capacitor Using Indium Tin Oxide Electrodes and High-k Dielectrics

Transparent analog capacitors using indium tin oxide (ITO) electrodes and HfO 2 (and Al 2 O 3 ) high-k dielectrics were examined for optical device applications. The adoption of ITO bottom and top electrodes for the capacitors did not degrade the electrical properties of the capacitors compared to titanium nitride (TiN) and Pt electrodes. Compared to conventional analog capacitors using TiN electrodes, capacitors using ITO electrodes show a larger capacitance at the negative voltages in the capacitance-voltage (C-V) curve. This suggests the presence of a thicker depletion layer at the top electrode, which is probably due to the high resistivity of the Sn-rich top ITO initial layer on the dielectric film. Before and after a subsequent thermal annealing, the C-V curve of ITO/Al 2 O 3 /ITO was barely changed, while that of ITO/HfO 2 /ITO showed significant variations. This was attributed to the change in the composition at the interface (i.e., Hf diffusion and oxygen deficiency) rather than to the change in the crystallinity of ITO and HfO 2 .

Investigation on spatially separated atomic layer deposition by gas flow simulation and depositing Al2O3 films

Al2O3 thin films were deposited using tri-methyl aluminum and ozone by spatially separated atomic layer deposition (SALD). A large gap was kept between the reactor and substrates in an attempt to enhance the process gas flow. According to simulation data and deposition results, strong edge pumping for the dominantly lateral flow improved the gas isolation and deposition was very effective, with a resulting gap height of 5 mm. To compare this SALD process with conventional atomic layer deposition (ALD), the authors examined how the amount of source supplied, the deposition temperature, and the number of rotations affected the growth rate. The growth rate per rotation was saturated at ∼0.12 nm/rotation at a deposition temperature of 250 °C, which is comparable to the saturated growth rate of the same film using conventional ALD. The dielectric constant of the films was ∼8 and the film with a capacitance equivalent thickness of 3.2 nm had a leakage level of 9.8 × 10−8 A/cm2 (at −1 V). X-ray photoelectron spe...

The Bias Temperature Instability Characteristics of In Situ Nitrogen Incorporated ZrO x N y Gate Dielectrics

The dielectric properties and bias temperature instability characteristics of in situ nitrogen incorporated ZrO x N y gate dielectrics were compared with those of ZrO 2 , HfO 2 , and HfO x N y . ZrO x N y showed a much smaller capacitance equivalent oxide thickness (1.43 nm) than ZrO 2 (2.13 nm) and exhibited a turn-around effect under a positive gate stress bias in n-type metal oxide semiconductor field-effect transistor, which is consistent with HfO x N y . However, compared to HfO x N y , ZrO x N y showed a significantly lower initial V th shift under a positive gate stress bias due to the lower number of shallow bulk traps related to oxygen vacancies.

Improvement in the performance of ZnO thin film transistors by using ultralow-pressure sputtering

Thin film transistors (TFTs) were fabricated with a zinc oxide (ZnO) channel deposited by ultralow-pressure sputtering (ULPS) at a pressure less than 1.3×10−3 Pa. The field-effect mobility (μFE) and the subthreshold gate swing (SS) of the ULPS-ZnO TFTs were dramatically improved up to 8.5 cm2/V s and 0.31 V/decade, respectively, compared to 1.6 cm2/V s and 1.31 V/decade for the ZnO TFTs fabricated by a conventional sputtering pressure (CSP) of 6.7×10−1 Pa. The improved characteristics of the ULPS-ZnO TFTs compared to the CSP-ZnO one can be attributed to the greater densification of the ZnO semiconductor film at the lower deposition pressure.