Sungin Suh

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.

Substrate Dependent Growth Rate of Plasma-Enhanced Atomic Layer Deposition of Titanium Oxide Using N2O Gas

TiO 2 thin films were grown on Ru, Pt, Al 2 O 3 -passivated Ru, and Si substrates by plasma-enhanced atomic layer deposition at 280°C. The Ru-substrate-enhanced growth (∼3 times higher than that on Si at <100 cycles) was attributed to the electron donation and the diffusion of previously contained oxygen from Ru onto the growing surface. When the Al 2 O 3 layer was interposed between the Ru substrate and TiO 2 film, even as thin as 0.4 nm, the electron donation was largely suppressed. Above 16―20 nm, the growth rates of rutile TiO 2 (on Ru) and anatase TiO 2 (on Si) were 0.055 and 0.04 nm/cycle, respectively.

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 .

Low-temperature SiON films deposited by plasma-enhanced atomic layer deposition method using activated silicon precursor

It has not been an easy task to deposit SiN at low temperature by conventional plasma-enhanced atomic layer deposition (PE-ALD) since Si organic precursors generally have high activation energy for adsorption of the Si atoms on the Si-N networks. In this work, in order to achieve successful deposition of SiN film at low temperature, the plasma processing steps in the PE-ALD have been modified for easier activation of Si precursors. In this modification, the efficiency of chemisorption of Si precursor has been improved by additional plasma steps after purging of the Si precursor. As the result, the SiN films prepared by the modified PE-ALD processes demonstrated higher purity of Si and N atoms with unwanted impurities such as C and O having below 10 at. % and Si-rich films could be formed consequently. Also, a very high step coverage ratio of 97% was obtained. Furthermore, the process-optimized SiN film showed a permissible charge-trapping capability with a wide memory window of 3.1 V when a capacitor structure was fabricated and measured with an insertion of the SiN film as the charge-trap layer. The modified PE-ALD process using the activated Si precursor would be one of the most practical and promising solutions for SiN deposition with lower thermal budget and higher cost-effectiveness.

Improving the electrical properties of lanthanum silicate films on ge metal oxide semiconductor capacitors by adopting interfacial barrier and capping layers.

The electrical properties of La-silicate films grown by atomic layer deposition (ALD) on Ge substrates with different film configurations, such as various Si concentrations, Al2O3 interfacial passivation layers, and SiO2 capping layers, were examined. La-silicate thin films were deposited using alternating injections of the La[N{Si(CH3)3}2]3 precursor with O3 as the La and O precursors, respectively, at a substrate temperature of 310 °C. The Si concentration in the La-silicate films was further controlled by adding ALD cycles of SiO2. For comparison, La2O3 films were also grown using [La((i)PrCp)3] and O3 as the La precursor and oxygen source, respectively, at the identical substrate temperature. The capacitance-voltage (C-V) hysteresis decreased with an increasing Si concentration in the La-silicate films, although the films showed a slight increase in the capacitance equivalent oxide thickness. The adoption of Al2O3 at the interface as a passivation layer resulted in lower C-V hysteresis and a low leakage current density. The C-V hysteresis voltages of the La-silicate films with Al2O3 passivation and SiO2 capping layers was significantly decreased to ∼0.1 V, whereas the single layer La-silicate film showed a hysteresis voltage as large as ∼1.0 V.

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...