Thermal and plasma-enhanced ALD of Ta and Ti oxide thin films from alkylamide precursors

We investigated the thermal and plasma-enhanced atomic layer deposition (PE-ALD) of tantalum and titanium oxides from representative alkylamide precursors, Ta(NMe2)(5) (pentakis(dimethylamino)Ta, PDMAT) and Ti(NMe2)(4) [tetrakis(dimethylamido)Ti, TDMAT]. ALD of Ta2O5 by PDMAT with water or oxygen plasma produced pure Ta2O5 films with good self-saturation growth characteristics. However, incomplete self-saturation was observed for TiO2 ALD from TDMAT. The film properties including microstructure, chemical composition, and electrical properties are discussed focusing on the comparative studies between thermal and PE-ALD processes for both oxides. The results indicate that the PDMAT is a promising precursor for both thermal and PE-ALD of Ta2O5.open117474sciescopu

The effects of nitrogen profile and concentration on negative bias temperature instability of plasma enhanced atomic layer deposition HfOxNy prepared by in situ nitridation

We have prepared plasma enhanced-atomic layer deposition HfOxNy thin films by in situ nitridation using nitrogen/oxygen mixture plasma and studied the effects of nitrogen contents and profiles on the negative bias temperature instability (NBTI). The nitrogen depth profiles and concentrations were controlled by changing the exposure sequences and the nitrogen to oxygen flow ratio, respectively. The best immunity to NBTI degradations was obtained for the nitrogen to oxygen ratio of 2:1 when nitrogen atoms are incorporated away from the high k/Si interface. We propose a dielectric degradation mechanism based on the reaction-diffusion model in which nitrogen plays a role of hydrogen generator at the interface and diffusion barrier in the bulk film. (c) 2008 American Institute of Physics. [DOI: 10.1063/1.2978360]open111012sciescopu

Electrical properties of atomic layer deposition HfO2 and HfOxNy on si substrates with various crystal orientations

The use of high-k gate oxide on Si substrates with alternative orientations is expected to contribute for the fabrication of high mobility devices. In this paper, the interfacial and electrical properties of the plasma enhanced atomic layer deposition (PE-ALD) HfO2 and HfOxNy gate oxides on Si substrates with three different crystal orientations, (001), (011), and (111),were comparatively studied. While PE-ALD HfO2 films were prepared using oxygen plasma as a reactant, PE-ALD HfOxNy films were prepared by in situ nitridation using oxygen/nitrogen mixture plasma. For all crystal orientations, in situ nitridation using oxygen/nitrogen mixture plasma improved electrical properties producing lower leakage currents and smaller equivalent oxide thickness values. Both HfO2 and HfOxNy films have shown the lowest leakage current and interface state density on Si (001), whereas the poorest electrical properties were obtained on Si (111). The results are discussed based on the experimental results obtained from various analytical techniques, including I-V, C-V, conductance methods, and X-ray photoelectron spectroscopy. (C) 2008 The Electrochemical Society.open111818sciescopu

Atomic scale nitrogen depth profile control during plasma enhanced atomic layer deposition of high k dielectrics

Nitrogen incorporation produces several benefits in the performance of high k gate oxides. However, since too much nitrogen incorporation at the interface of gate dielectric can result in device degradation, the atomic scale control of nitrogen depth profile is desirable. In this study, the authors have improved electrical properties and interface properties by depth profile control of in situ nitrogen incorporation during plasma enhanced atomic layer deposition. The best electrical properties in terms of hysteresis, equivalent oxide thickness, and interface states were obtained when the nitrogen is incorporated in the middle of the thin film, which has not been achievable by other techniques.open111719sciescopu

Atomic layer deposition of Ta-based thin films: Reactions of alkylamide precursor with various reactants

The growth mechanisms and film properties of atomic layer deposition (ALD) Ta-based thin films were investigated from alkylamide precursor [Ta(NMe2)(5), (PDMAT)]. The reactions of PDMAT with various reactants including water, NH3, Oxygen, and hydrogen plasma were studied and the resulting film properties were investigated by various analysis techniques. For TaN ALD from NH3 and H plasma, the films were contaminated by considerable amount of carbon, while the Ta2O5 deposited from water and O plasma were quite pure. Also, nitrogen was incorporated for ALD from PDMAT and H plasma, while no nitrogen incorporation was observed for O-plasma based plasma enhanced-ALD of Ta2O5 except at high deposition temperature over 300 degrees C. The results were comparatively discussed focusing on the differences in growth mechanism depending on reactants. (c) 2006 American Vacuum Society.open113639sciescopu

Electrical property improvements of high-k gate oxide by in situ nitrogen incorporation during atomic layer deposition

Atomic layer deposition (ALD) process for oxynitrides of high-k gate dielectrics employing NH4OH as a single source for reactants, water and NH3, was studied. By this method, nitrogen was incorporated up to 1-3 at. % for ALD Al2O3 and Ta2O5 films from metal organic precursors. A comparative study with water based ALD showed that the electrical properties were improved. The leakage current of oxide films from NH4OH based ALD had been reduced and, more importantly, the dielectric strength was found to be enhanced by more than two orders of magnitude from a time dependent dielectric breakdown measurement. (c) 2007 American Institute of Physics.X119sciescopu

Effects of Fluorine Plasma Treatment on the Electronic Structure of Plasma-Enhanced Atomic Layer Deposition HfO2

We investigated the effects of fluorine treatments on the electrical properties and electronic structures of plasma-enhanced atomic layer deposition HfO2 gate oxides, depending on the treatment process. Pre- and postoxide-deposition fluorine treatments were carried out using CF4 plasma. Improved dielectric properties were achieved by predeposition treatment, while degradation of electrical properties was observed for postdeposition treatment. Based on the electronic structure analysis using X-ray photoemission spectroscopy and near-edge X-ray absorption fine structures, we found that the enhanced dielectric properties of the pretreated HfO2 are induced by the defect passivation and conduction-band offset increase. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3089976] All rights reserved.open111010sciescopu

Plasma-Enhanced ALD of TiO2 Thin Films on SUS 304 Stainless Steel for Photocatalytic Application

Plasma-enhanced atomic layer deposition (PE-ALD) of TiO2 thin films using Ti(NMe2)(4) [tetrakis(dimethylamido) Ti] and O-2 plasma were prepared on stainless steel to show the self-cleaning effect. The TiO2 thin films deposited on stainless steel have high growth rate, large surface roughness, and low impurities. The film deposited below 200 degrees C was amorphous, while the films deposited at 300 and 400 degrees C showed anatase and rutile phases, respectively. The contact angle measurements on crystalline PE-ALD TiO2 thin films exhibited superhydrophilicity after UV irradiation. The TiO2 thin film with anatase phase deposited at 300 degrees C showed the highest photocatalytic efficiency, which is higher than on Activ glass or thermal ALD TiO2 films. We suggest that anatase structure and large surface area of TiO2 thin film on stainless steel are the main factors for the high photocatalytic efficiency. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3095515] All rights reserved.X117sciescopu

Flatband voltage control in p-metal gate metal-oxide-semiconductor field effect transistor by insertion of TiO2 layer

Titanium oxide (TiO2) layer was used to control the flatband voltage (V-FB) of p-type metal-oxide-semiconductor field effect transistors. TiO2 was deposited by plasma enhanced atomic layer deposition (PE-ALD) on hafnium oxide (HfO2) gate dielectrics. Comparative studies between TiO2 and Al2O3 as capping layer have shown that improved device properties with lower capacitance equivalent thickness (CET), interface state density (D-it), and flatband voltage (V-FB) shift were achieved by PE-ALD TiO2 capping layer.open111210sciescopu

Hybrid nanofabrication processes utilizing diblock copolymer nanotemplate prepared by self-assembled monolayer based surface neutralization

Nanostructures including nanohole and metal dot arrays were fabricated by hybrid processes combing self-assembled diblock copolymer and conventional semiconductor processes. The interfacial energy between polystyrene-b-polymethylmetacrylate (PS-b-PMMA) diblock copolymer and substrate surface was controlled by employing a self-assembled monolayer (SAM), resulting in a polymer template with well-ordered cylindrical nanohole array. The nanohole sizes were controlled within 10 to 22 nm in diameter using block copolymers with different molecular weights. The PS nanotemplates were fabricated on various substrates, including oxides, nitrides, and poly-Si. Nanohole pattern was transferred by dry etching process, producing inorganic nanohole templates. Also, gold nanodot arrays with diameter smaller than 10 nm were fabricated through lift off process. (c) 2008 American Vacuum Society.open112020sciescopu