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.

Semiconductor device, and manufacturing method thereof

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.

https://iopscience.iop.org/article/10.7567/JJAP.54.040103/pdf

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

A comprehensive introduction and up-to-date reference to SiC power semiconductor devices covering topics from material properties to applications Based on a number of breakthroughs in SiC material science and fabrication technology in the 1980s and 1990s, the first SiC Schottky barrier diodes (SBDs) were released as commercial products in 2001. The SiC SBD market has grown significantly since that time, and SBDs are now used in a variety of power systems, particularly switch-mode power supplies and motor controls. SiC power MOSFETs entered commercial production in 2011, providing rugged, high-efficiency switches for high-frequency power systems. In this wide-ranging book, the authors draw on their considerable experience to present both an introduction to SiC materials, devices, and applications and an in-depth reference for scientists and engineers working in this fast-moving field . Fundamentals of Silicon Carbide Technology covers basic properties of SiC materials, processing technology, theory and analysis of practical devices, and an overview of the most important systems applications. Specifically included are:

Fundamentals of Silicon Carbide Technology: Growth, Characterization, Devices and Applications

SiC electronic device technology has made rapid progress during the past decade In this paper, we review the evolution of SiC power MOSFETs between 1992 and the present, discuss the current status of device development, identify the critical fabrication issues, and assess the prospects for continued progress and eventual commercialization

Status and prospects for SiC power MOSFETs

Silicon carbide (SiC) is a promising material for the development of high-temperature solid-state electronics and transducers, owing to its excellent electrical, mechanical, and chemical properties. This paper is a review of silicon carbide for microelectromechanical systems (SiC MEMS). Current efforts in developing SiC MEMS to extend the silicon-based MEMS technology to applications in harsh environments are discussed. A summary is presented of the material properties that make SiC an attractive material for use in such environments. Challenges faced in the development of processing techniques are also outlined. Last, a review of the current stare of SiC MEMS devices and issues facing future progress are presented.

Silicon carbide MEMS for harsh environments

A novel silicon carbide UMOSFET structure is reported. This device incorporates two new features: a self-aligned p-type implantation in the bottom of the trench that reduces the electric field in the trench oxide, and an n-type epilayer under the p-base to promote lateral current spreading into the drift region. This UMOS structure is capable of supporting the full blocking voltage of the pn junction while keeping the electric field in the gate oxide below 4 MV/cm. An accumulation channel is formed on the sidewalls of the trench by epigrowth, and the gate oxide is produced by a polysilicon oxidation process, resulting in a uniform oxide thickness over both the sidewalls and bottom of the trench. The fabricated 4H-SiC devices have a blocking voltage of 1400 V (10 /spl mu/m drift region), a specific on-resistance of 15.7 m/spl Omega/-cm/sup 2/ at room temperature, and a gate oxide field of 3 MV/cm.

High-voltage accumulation-layer UMOSFET's in 4H-SiC

A method to form SiO2/SiC metal–oxide–semiconductor structures by oxidation of a thin polycrystalline silicon (polysilicon) layer deposited on SiC is demonstrated. The oxidation time used is sufficient to oxidize all the polysilicon while short enough at 1050 °C to insure insignificant oxidation of the underlying SiC. Since the oxidation of SiC is highly anisotropic, this method allows uniform oxide formation on a nonplanar SiC surface. The SiO2/SiC interface quality is comparable to that obtained with thermal oxidation.

Metal-oxide-semiconductor capacitors formed by oxidation of polycrystalline silicon on sic

During the past year, the performance of SiC power MOSFETs exceeded the theoretical limits of silicon devices for the first time. This milestone was achieved by the introduction of the first SiC accumulation-layer UMOSFET (U-ACCUFET) in 1997. In this device, an accumulation-layer channel is formed under the MOS diode by an n-type epitaxial layer on the sidewalls of the UMOS trench. The high electron mobility in the accumulation channel reduced the specific on-resistance to 10.9 mΩ-cm/sup 2/, the lowest value yet reported for a SiC power MOSFET. Although the blocking voltage of the device is only 450 V, the figure-of-merit V/sub B//sup 2//R/sub ON/ is 18.6 MW/cm/sup 2/, the highest value reported at that time for a SiC power MOSFET and about 4× higher than the theoretical limit for silicon MOSFETs. In this paper, we report an improved UMOS ACCUFET incorporating structural innovations that increase the blocking voltage to 850 V while maintaining a low on-resistance of 27 mΩ-cm/sup 2/. The resulting V/sub B//sup 2//R/sub ON/ is 26.8 MW/cm/sup 2/, about 6× higher than the theoretical limit for silicon.

J. Tan

Papers

High-voltage accumulation-layer UMOSFET's in 4H-SiC

Metal-oxide-semiconductor capacitors formed by oxidation of polycrystalline silicon on sic

High-voltage accumulation-layer UMOSFETs in 4H-SiC