Shinsuke Harada

Bio: Shinsuke Harada is an academic researcher from National Institute of Advanced Industrial Science and Technology. The author has contributed to research in topics: MOSFET & Gate oxide. The author has an hindex of 22, co-authored 169 publications receiving 1709 citations.

Excellent effects of hydrogen postoxidation annealing on inversion channel mobility of 4H-SiC MOSFET fabricated on (11 2 0) face

Abstract: Effects of hydrogen postoxidation annealing (H/sub 2/ POA) on 4H-silicon carbide (SiC) MOSFETs with wet gate oxide on the (112~0) face have been investigated. As a result, an inversion channel mobility of 110 cm/sup 2//Vs was successfully achieved using H/sub 2/ POA at 800/spl deg/C for 30 min. H/sub 2/ POA reduces the interface trap density by about one order of magnitude compared with that without H/sub 2/ POA, resulting in considerable improvement of the inversion channel mobility to 3.5 times higher than that without H/sub 2/ POA. In addition, 4H-SiC MOSFET with H/sub 2/ POA has a lower threshold voltage of 3.1 V and a wide gate voltage operation range in which the inversion channel mobility is more than 100 cm/sup 2//Vs.

Improved Channel Mobility in 4H-SiC MOSFETs by Boron Passivation

Abstract: We propose another process for fabricating 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) with high channel mobility. The B atoms were introduced into a SiO 2 /4H-SiC interface by thermal annealing with a BN planar diffusion source. The interface state density near the conduction band edge of 4H-SiC was effectively reduced by the B diffusion and the fabricated 4H-SiC MOSFETs showed a peak field-effect mobility of 102 cm 2 /Vs. The obtained high channel mobility cannot be explained by counter doping because B atoms act as acceptors in 4H-SiC. We suggest that the interfacial structural change of SiO 2 may be responsible for the reduced trap density and enhanced channel mobility.

Development of Ultrahigh-Voltage SiC Devices

Abstract: Ultrahigh-voltage silicon carbide (SiC) devices [p-i-n diodes and insulated-gate bipolar transistors (IGBTs)] and switching test have been investigated. As a result, we have succeeded in developing a 13-kV p-i-n diode, 15-kV p-channel IGBT, and 16-kV flip-type n-channel implantation and epitaxial IGBT with a low differential specific on-resistance ( R $_{\rm diff,on}$ ). It was revealed that a power module fabricated using a nanotech resin, Si3N4 ceramic substrate, and W base plate was suitable for ultrahigh voltage and high temperature. A switching test was carried out using a clamped inductive load circuit, which indicated that the energy loss of a circuit with ultrahigh-voltage SiC devices is lower than that of Si devices.

Relationship between channel mobility and interface state density in SiC metal–oxide–semiconductor field-effect transistor

Abstract: Temperature dependence of threshold voltage in n-channel SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) was studied. Linear relation was observed between the threshold voltage shift when the temperature varies from −150 to 150 °C and the number of the interface states present within the energy range of 0.2–0.4 eV from the conduction band edge energy Ec. This relationship revealed that the interface state profile near Ec in n-channel SiC MOSFETs can be represented by that in n-type SiC MOS capacitors. The relationship between the channel mobility and the interface state profile also suggested that the interface states within the energy range of 0.2–0.4 eV from Ec have little influence on the channel mobility.

Characterization of Traps at Nitrided SiO 2 / SiC Interfaces near the Conduction Band Edge by using Hall Effect Measurements

Abstract: The effects of nitridation on the density of traps at SiO2/SiC interfaces near the conduction band edge were qualitatively examined using a simple, newly developed characterization method that utilizes Hall effect measurements and split capacitance–voltage measurements. The results showed a significant reduction in the density of interface traps near the conduction band edge as a result of nitridation, but the interface traps were not completely eliminated by nitridation.

Thin-Film Transistor Fabricated in Single-Crystalline Transparent Oxide Semiconductor

Abstract: We report the fabrication of transparent field-effect transistors using a single-crystalline thin-film transparent oxide semiconductor, InGaO 3 (ZnO) 5 , as an electron channel and amorphous hafnium oxide as a gate insulator. The device exhibits an on-to-off current ratio of ∼10 6 and a field-effect mobility of ∼80 square centimeters per volt per second at room temperature, with operation insensitive to visible light irradiation. The result provides a step toward the realization of transparent electronics for next-generation optoelectronics.

Semiconductor device, and manufacturing method thereof

Abstract: An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Review of Silicon Carbide Power Devices and Their Applications

Abstract: Silicon carbide (SiC) power devices have been investigated extensively in the past two decades, and there are many devices commercially available now. Owing to the intrinsic material advantages of SiC over silicon (Si), SiC power devices can operate at higher voltage, higher switching frequency, and higher temperature. This paper reviews the technology progress of SiC power devices and their emerging applications. The design challenges and future trends are summarized at the end of the paper.

Material science and device physics in SiC technology for high-voltage power devices

Abstract: Power semiconductor devices are key components in power conversion systems. Silicon carbide (SiC) has received increasing attention as a wide-bandgap semiconductor suitable for high-voltage and low-loss power devices. Through recent progress in the crystal growth and process technology of SiC, the production of medium-voltage (600?1700 V) SiC Schottky barrier diodes (SBDs) and power metal?oxide?semiconductor field-effect transistors (MOSFETs) has started. However, basic understanding of the material properties, defect electronics, and the reliability of SiC devices is still poor. In this review paper, the features and present status of SiC power devices are briefly described. Then, several important aspects of the material science and device physics of SiC, such as impurity doping, extended and point defects, and the impact of such defects on device performance and reliability, are reviewed. Fundamental issues regarding SiC SBDs and power MOSFETs are also discussed.