Shigetoshi Hosaka

Formation of a manganese oxide barrier layer with thermal chemical vapor deposition for advanced large-scale integrated interconnect structure

Advanced large-scale integrated interconnect structure faces a major challenge in forming a thin and conformal diffusion barrier layer. We deposited a Mn oxide layer by thermal chemical vapor deposition (CVD) on SiO2 substrates and investigated deposition behavior and diffusion barrier property. A thin Mn oxide layer was formed with a uniform thickness of 2.6–10nm depending on deposition temperature between 100 and 400°C. Heat-treated samples of Cu/CVD-Mn oxide/SiO2 indicated no interdiffusion at 400°C for 100h. The CVD of the Mn oxide layer was found to be an excellent barrier formation process.

Chemical Vapor Deposition of Mn and Mn Oxide and their Step Coverage and Diffusion Barrier Properties on Patterned Interconnect Structures

Chemical vapor deposition of bis(ethylcyclopentadienyl)manganese, (EtCp)2Mn, was performed on a patterned interconnect structure to obtain a thin conformal layer with a good diffusion barrier property for advanced Si devices. Deposition of (EtCp)2Mn on SiO2 formed a conformal layer of Mn oxide within a contact hole with a uniform thickness of 3 to 4 nm. Similar conformal formation of Mn oxide was obtained on SiO2 in the vias and trenches of a dual-damascene structure. The deposition of (EtCp)2Mn on Cu, however, formed a solid solution with Cu. The solute Mn migrated toward the interface of Cu/SiO2 to form Mn oxide.

Influence of Crystal Orientation of Ru Under-Layer on Initial Growth of Copper Chemical Vapor Deposition

The effect of Ru crystal orientation on the deposition behavior of chemical vapor deposition (CVD) Cu was investigated. The crystal orientation of Ru films was modulated by adjusting sputtering temperature. Ru(001) and random orientation films were obtained by sputtering at 300 °C and room temperature, respectively. CVD Cu on Ru with the (001) crystal orientation had a smooth morphology and a strong (111) peak. However, CVD Cu on the Ru film with the random orientation had a rough surface and a random orientation. A low lattice misfit between Cu(111) and Ru(001) realized a good morphology and a strong (111) orientation of CVD Cu films, which coincide with our lattice misfit concept.

Performance and reliability improvement in SiC power MOSFETs by implementing AlON high-k gate dielectrics

We have developed AlON high-k gate dielectric technology that can be easily implemented into both planar and trench SiC-based MOSFETs. On the basis of electrical characterization and numerical simulation, the thickness ratio of the AlON layer to the SiO2 interlayer and nitrogen content in AlON film were carefully optimized to enhance device performance and reliability.

Effects of Water Desorption from SiO2 Substrates on the Thickness of Manganese Oxide Diffusion Barrier Layer Formed by Chemical Vapor Deposition

A manganese oxide (MnOx) diffusion barrier layer was formed by chemical vapor deposition (CVD) on SiO2 substrates with or without preannealing. The thickness dependence of the MnOx layer was investigated in relation to the desorption behavior of water vapor from the substrates. A good correlation was found between MnOx thickness and the amount of desorbed water vapor. It is necessary to control the amount of absorbed water in the substrate to form a thin MnOx barrier layer with good thickness reproducibility.

Investigation of Morphology and Crystallinity of ZnO Crystal Formed by Side-Flow-Type MOCVD

ZnO crystals formed on sapphire (1120) substrates by means of side-flow-type metallorganic chemical vapor deposition (MOCVD) are controlled to various shapes by adjusting process parameters. The relationship between the morphology and the crystallinity of ZnO crystals is investigated. It is found that the crystallinity of a ZnO film structure with nanostructures is better than that of only a ZnO nanorod structure although they are fabricated under the same growth temperature condition. In the case of a ZnO nanorod structure, a high growth temperature (at or over 1073 K) plays a significant role in improving ZnO crystallinity. It is also confirmed by X-ray diffraction rocking curves and transmission electron microscopy observations that ZnO crystals with a microcone morphology formed at 1073 K have high crystal quality.

Halide Vapor Phase Epitaxy of MgxZn1-xO Layers on Zn-Polar ZnO Substrates

High quality MgxZn1-xO layers (0≤x≤0.16) on Zn-polar ZnO substrates were successfully grown by halide vapor phase epitaxy (HVPE) at a high temperature of 1000 °C. The MgxZn1-xO layers exhibited atomically flat surfaces, and were free from impurities. The near-band-edge emission of photoluminescence (PL) at room temperature could be varied from 3.26 to 3.56 eV with increase of the Mg concentration. PL measurements at 12 K revealed that a Mg0.16Zn0.84O layer grown by HVPE exhibited excellent optical properties.

Controlled Structure of Zinc Oxide by Means of Side Flow Type MOCVD

We have demonstrated that the ZnO deposited on sapphire (11-20) substrate is controlled to various structures by side flow type MOCVD at high temperature (above 973 K). We found that the crystal quality of ZnO having film structure is better than that of ZnO nanorod although they are fabricated under the same temperature condition. Also, in the case of ZnO nanorod, it is found that its crystal quality improves dramatically at higher temperature (1073 K). Metal-oxide materials are known to have interesting optical, electrical, and magnetic properties. Among them, zinc oxide (ZnO)-based materials have been investigated for many years due to its wide-direct band gap of 3.37 eV at room temperature and its large exciton binding energy of 60 meV. Recently, much attention has been paid to ZnO nano/micorostructres 1-3 , such as nanowire, nanorod, nanoneedle, and nano/microcone, which are regarded as promising material for new devices, for example ultraviolet (UV) laser, gas sensors. Various kinds of ZnO nanostructures are prepared by chemical vapor deposition (CVD) 4, 5 , sputtering 6 , electrochemical decomposition 7 , thermal evaporation 8 , vapor-liquid-solid (VLS) processes 9 , which are operated at low temperature less than 973 K or with gold (Au) seeds on a substrate so that ZnO nanostructures can be obtained. Among their techniques, CVD, especially metal organic chemical deposition (MOCVD) is thought to be appropriate for commercial production because it has turned out to be excellent growth technique for nitride semiconductors. In the case of ZnO, however, MOCVD technique for ZnO has a problem that metal organic precursors as Zn are highly reactive with O precursors, such as oxygen and water. When the pre-reaction of these sources occurs ZnO powders produce on the substrate, which gives rise to deteriorating the ZnO structure controllability and declining the ZnO crystal quality. Therefore, we have designed the unique side flow type MOCVD system so as to overcome these problems by optimizing the reactor structure and growth condition. In this report, we have demonstrated that the ZnO deposited on sapphire (11-20) substrate is controlled to various structures by side flow type MOCVD at high temperature (above 973 K). In addition, we have investigated the relationship between ZnO structures and their crystal quality.

Reliability-aware design of metal/high-k gate stack for high-performance SiC power MOSFET

Advanced metal/high-k gate stack technology for SiC-based power MOSFET was demonstrated. We found that the Hf incorporation into aluminum oxynitride (HfAlON gate insulator) combined with TIN electrode effectively improves the stability of threshold voltage under both negative and positive bias temperature stresses. Since the relative permittivity of HfAlON increases with increasing Hf content, peak transconductance enhancement up to 3.4 times with acceptable reliability margin was achieved in the state-of-the-art trench MOSFET by implementing TiN/HfA10N(Hf50%) gate stack.

Flatband Voltage Shift Depending on SiO2/SiC Interface Charges in 4H-SiC MOS Capacitors with AlON/SiO2 Stacked Gate Dielectrics

The mechanism of flatband voltage shift in SiC metal-oxide-semiconductor (MOS) capacitors with stacked gate dielectrics consisting of aluminum oxynitride (AlON) layers and SiO2 underlayers was investigated by varying the AlON and SiO2 thicknesses. The flatband voltages of the fabricated capacitors with fixed SiO2 underlayer thicknesses were almost independent of the AlON thickness, indicating the negligible charges in AlON layer. On the other hand, when varying SiO2 underlayer thickness, the flatband voltage decreased with an increase in capacitance equivalent thickness (CET), and the slope of their linear fit was comparable to that for SiC MOS capacitors without AlON layer. These observations can be well explained by assuming interface charges at AlON/SiO2 interface with an amount comparable, but a polarity opposite to, those at SiO2/SiC interface.