The fact that wide bandgap semiconductors are capable of electronic functionality at much higher temperatures than silicon has partially fueled their development, particularly in the case of SiC. It appears unlikely that wide bandgap semiconductor devices will find much use in low-power transistor applications until the ambient temperature exceeds approximately 300/spl deg/C, as commercially available silicon and silicon-on-insulator technologies are already satisfying requirements for digital and analog VLSI in this temperature range. However practical operation of silicon power devices at ambient temperatures above 200/spl deg/C appears problematic, as self-heating at higher power levels results in high internal junction temperatures and leakages. Thus, most electronic subsystems that simultaneously require high-temperature and high-power operation will necessarily be realized using wide bandgap devices, once they become widely available. Technological challenges impeding the realization of beneficial wide bandgap high ambient temperature electronics, including material growth, contacts, and packaging, are briefly discussed.

High-temperature electronics - a role for wide bandgap semiconductors?

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

The outstanding properties of SiO2, which include high resistivity, excellent dielectric strength, a large band gap, a high melting point, and a native, low defect density interface with Si, are in large part responsible for enabling the microelectronics revolution. The Si/SiO2 interface, which forms the heart of the modern metal–oxide–semiconductor field effect transistor, the building block of the integrated circuit, is arguably the worlds most economically and technologically important materials interface. This article summarizes recent progress and current scientific understanding of ultrathin (<4 nm) SiO2 and Si–O–N (silicon oxynitride) gate dielectrics on Si based devices. We will emphasize an understanding of the limits of these gate dielectrics, i.e., how their continuously shrinking thickness, dictated by integrated circuit device scaling, results in physical and electrical property changes that impose limits on their usefulness. We observe, in conclusion, that although Si microelectronic devices...

Ultrathin (<4 nm) SiO2 and Si-O-N gate dielectric layers for silicon microelectronics: Understanding the processing, structure, and physical and electrical limits

A monolithic current-mode CMOS DC-DC converter with integrated power switches and a novel on-chip current sensor for feedback control is presented in this paper. With the proposed accurate on-chip current sensor, the sensed inductor current, combined with the internal ramp signal, can be used for current-mode DC-DC converter feedback control. In addition, no external components and no extra I/O pins are needed for the current-mode controller. The DC-DC converter has been fabricated with a standard 0.6-/spl mu/m CMOS process. The measured absolute error between the sensed signal and the inductor current is less than 4%. Experimental results show that this converter with on-chip current sensor can operate from 300 kHz to 1 MHz with supply voltage from 3 to 5.2 V, which is suitable for single-cell lithium-ion battery supply applications. The output ripple voltage is about 20 mV with a 10-/spl mu/F off-chip capacitor and 4.7-/spl mu/H off-chip inductor. The power efficiency is over 80% for load current from 50 to 450 mA.

A monolithic current-mode CMOS DC-DC converter with on-chip current-sensing technique

Interfacial characteristics of Al/SiO2/n-type 6H–SiC metal–oxide–semiconductor capacitors fabricated by rapid thermal processing (RTP) with N2O and NO annealing are investigated. Interface state density was measured by a conductance technique at room temperature. RTP oxidation in pure O2 leads to an excellent SiO2/n-type 6H–SiC interface with interface state density in the order of 1010–1011 eV−1 cm−2. NO annealing improves the SiO2/n-type 6H–SiC interface, while N2O annealing increases the interface state density.

Interfacial characteristics of n2o and no nitrided sio2 grown on sic by rapid thermal processing

This letter addresses the question of why it is possible to grow high-quality oxide films on N-type but not on P-type SiC. It provides results which indicate that the oxide/SiC interface would be inferior to the oxide/Si interface for both N-type and P-type SiC, if it were not for the beneficial effects of nitrogen incorporation. The letter presents, for the first time, results on nitridation of thermally grown oxides in NO and N/sub 2/O. The results demonstrate that the oxides grown on P-type can be improved by NO annealing, but not by N/sub 2/O annealing.

/pdf/nitridation-of-silicon-dioxide-films-grown-on-6h-silicon-53m1qeli7r.pdf

Nitridation of silicon-dioxide films grown on 6H silicon carbide

High quality ultrathin silicon oxynitride films (3.5 nm) have been grown in a nitric oxide ambient using rapid thermal processing. The physical and electrical properties of these films are compared with those formed in a nitrous oxide environment. X‐ray photoelectron spectroscopy (XPS) results show that the nitric oxide (NO) grown films have a significantly different nitrogen distribution compared to the nitrious oxide (N2O) grown films. The capacitance‐voltage and current‐voltage characteristics of the NO grown and NO‐modified films are, in general, better than those of the same thickness grown in either N2O or O2.

/pdf/high-quality-ultrathin-dielectric-films-grown-on-silicon-in-f00skdpyqt.pdf

High quality ultrathin dielectric films grown on silicon in a nitric oxide ambient

Most converter designs assume that a closed power switch has zero volts across it. In general, this is a valid assumption that reduces the design complexity. However the fact that a power switch does have a finite resistance means that there will be a nonzero voltage across it during its on time. This voltage can be taken advantage of. This paper proposes a simple control technique that utilizes the variable resistance of the power MOSFET in a dc-dc converter. This is the first switched mode power supply that uses the power switch in more than two states or operating points. It is also the first switched mode power supply that uses the power switch as a variable control device as well as a power device. A 48-5-V 20-W forward converter is implemented to confirm the theory and demonstrate its practicality. The proposed technique provides self oscillation, self overload protection, zero voltage switching (ZVS), input voltage feedforward, and a reduced component count and cost.

/pdf/controlling-a-dc-dc-converter-by-using-the-power-mosfet-as-a-7souknqy3x.pdf

Controlling a DC-DC converter by using the power MOSFET as a voltage controlled resistor

This letter demonstrates that the reliability of oxides grown on p-type 4H-SiC can be dramatically improved by NO nitridation. High field (-8 Mv/cm) room-temperature stressing and high-temperature negative-bias (250/spl deg/C, -4 MV/cm) testing were used to investigate the reliability of NO nitrided oxides. Relatively small changes in the flat-band voltage, interface-trap density and leakage current were observed after 5000 s in the case of NO nitrided oxides, while shorter stressing shifted these parameters dramatically in the case of N annealed control samples.

/pdf/improved-reliability-of-no-nitrided-sio-2-grown-on-p-type-4h-30j9nda3xx.pdf

Improved reliability of NO-nitrided SiO 2 grown on p-type 4H-SiC

The effects of nitric oxide (NO) annealing on conventional thermal oxides are reported in this letter. The oxide thickness increase, resulting from NO annealing, is found to be only a few angstroms ( >

/pdf/effects-of-nitric-oxide-annealing-of-thermally-grown-silicon-8lwopi91cr.pdf

Herbert Barry Harrison

Papers

Nitridation of silicon-dioxide films grown on 6H silicon carbide

High quality ultrathin dielectric films grown on silicon in a nitric oxide ambient

Controlling a DC-DC converter by using the power MOSFET as a voltage controlled resistor

Improved reliability of NO-nitrided SiO 2 grown on p-type 4H-SiC

Effects of nitric oxide annealing of thermally grown silicon dioxide characteristics