W. J. Maeng

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°C. The results were comparatively discussed focusing on the differences in growth mechanism depending on reactants.

Flat band voltage (VFB) modulation by controlling compositional depth profile in La2O3/HfO2 nanolaminate gate oxide

We investigated the flat band voltage (VFB) modulation by insertion of lanthanum oxide (La2O3) into hafnium oxide (HfO2) gate dielectrics. The properties of La2O3/HfO2 nanolaminates were precisely modulated by controlling the position of La2O3 layer at bottom, middle, or top using atomic layer deposition. When the La2O3 layer was positioned closer to the interface (bottom), the reduction in VFB shift was more effective than the other two cases (middle and top). From our experimental results, we propose that the main mechanism of VFB modulation using La2O3 layer is dipole moment formation at an interfacial layer between high k gate dielectric and Si substrate.

Electrical Properties of Atomic Layer Deposition HfO2 and HfO x N y 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) HfO 2 and HfO x N y gate oxides on Si substrates with three different crystal orientations, (001), (011), and (111), were comparatively studied. While PE-ALD HfO 2 films were prepared using oxygen plasma as a reactant, PE-ALD HfO x N y 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 HfO 2 and HfOxN y 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.

Dendron-modified polystyrene microtiter plate: surface characterization with picoforce AFM and influence of spacing between immobilized amyloid beta proteins.

A polystyrene microtiter plate was coated with a molecular layer of a cone-shaped dendron as a means of providing proper spacing between immobilized biomolecules. For the coating preparation, di(ethylene glycol) vinyl ether was grafted onto the surface of the microtiter plate by a plasma process followed by self-assembly of a second-generation dendron (9-acid) or a third-generation dendron (27-acid). Contact angle analysis revealed a pronounced increase in the hydrophilicity upon plasma grafting, while the hydrophilicity reverted/decreased after dendron immobilization. For analysis by force-based atomic force microscopy (AFM), oligonucleotides were immobilized onto the AFM tip and the plate. The DNA-DNA interaction was observed at all spots examined, which implied that coating of the dendrons was uniform over the entire surface. The effectiveness for biomolecular assays of the spacing on dendron-modified microtiter plates was examined by carrying out an enzyme-linked immunosorbent assay (ELISA), where enhanced detection of different fragments of amyloid beta protein (A beta) was observed when compared with other conventional plates, such as untreated polystyrene or maleic anhydride activated plates. The positive influence of the mesospacing between biomolecules on the microtiter plates for this assay was confirmed.

Comparative Studies of Atomic Layer Deposition and Plasma-Enhanced Atomic Layer Deposition Ta2O5 and the Effects on Electrical Properties of In situ Nitridation

Ta2O5 and TaOxNy thin films were deposited by atomic layer deposition (ALD) from Ta(NMe2)5 (PDMAT) with water, oxygen plasma, and nitrogen added oxygen plasma. The film properties were comparatively investigated focusing on the electrical properties from metal oxide semiconductor capacitor structure with 10 nm Ta2O5 or TaOxNy. The results show that plasma-enhanced ALD (PE-ALD) Ta2O5 film has better electrical properties including lower interface state density and leakage current than thermal ALD. Moreover, PE-ALD TaOxNy shows the best properties, indicating the beneficial effects of in situ nitridation. Especially, time dependent dielectric breakdown was significantly improved up to 4000 times of thermal ALD Ta2O5. These results show that, intentional in situ nitrogen incorporation with good electrical properties was successfully achieved by PE-ALD using nitrogen–oxygen mixture.

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.

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 (VFB) 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 (Dit), and flatband voltage (VFB) shift were achieved by PE-ALD TiO2 capping layer.

HfO2 / HfO x N y / HfO2 Gate Dielectric Fabricated by In Situ Oxidation of Plasma-Enhanced Atomic Layer Deposition HfN Middle Layer

By using H 2 plasma as a reactant with tetrakis(dimethylamino)hafnium precursor during plasma-enhanced atomic layer deposition, we deposited the HfO x N y layer between HfO 2 layers. The 5 nm thick HfO 2 /HfO x N y /HfO 2 (HfONO) trilayer gate oxide shows reduced capacitance equivalent oxide thickness (≅1.25 nm) than that (≅1.40 nm) of the HfO 2 film with the same thickness due to the contribution of nitrogen incorporation to the high dielectric constant. The HfONO film utilizing H 2 plasma shows lower values of interface trap density (D it ), trapped positive charge density (ΔN p ), and gate leakage currents than the HfO 2 layer with the same thickness while maintaining comparable hysteresis (≤30 mV). The results can be attributed to the presence of N-H bonds, which can reduce localized states below the conduction band and prevent the conduction-band lowering, and decrement of N-N and N-O bonds, which contribute to trap density, confirmed by the combination of X-ray photoelectron spectroscopy and near-edge X-ray absorption fine-structure analyses.

Atomic layer deposition of B2O3/SiO2 thin films and their application in an efficient diffusion doping process

We investigated atomic layer deposition (ALD) of B2O3 and SiO2 thin films using trimethylborate (TMB) and bis-(diethylamino)silane (SAM-24) precursors, focusing on growth characteristics and film properties. For both cases, ALD processes using O3 and O2 plasma as reactants exhibited well-defined growth saturation and linear growth behavior without any incubation cycles, and produced highly pure, stoichiometric films. In the case of B2O3 films, however, SiO2 layer passivation is required onto the B2O3 due to a spontaneous decomposition caused by moisture in air. On the basis of electrical characterization, the detailed dielectric properties of SiO2 and B2O3/passivation SiO2 films were extensively discussed including the k-value, flat band voltage, and leakage currents. Then, boron-doped SiO2 films with different B/(B + Si) compositions were prepared by controlling B2O3 and SiO2 growth cycles, followed by drive-in annealing and a subsequent wet removal process. Based on both theoretical estimation and SIMS depth profile results, we demonstrated that the surface doping concentration is effectively modulated with controllable B doping contents in the B-doped SiO2 films.

Effects of Post-Annealing on Properties of HfO 2 Films Grown by ALD

The effects of post-annealing of high-k thin films grown by atomic layer deposition method were investigated by the annealing treatments of . capacitor structures were fabricated, and then the capacitance-voltage and current-voltage characteristics were measured to analyze the electrical characteristics of dielectric layers. The X-ray diffraction analyses revealed that the film remained to be amorphous, and the film was crystallized. The annealing treatment at resulted in the highest capacitance and the lowest leakage current due to the reduction of defects in the films and non-crystallization. Our results suggest that post-annealing treatments are a critical factor in improving the characteristics of gate dielectric layer.