SiC power-switching devices-the second electronics revolution?

Silicon carbide (SiC) offers significant advantages for power-switching devices because the critical field for avalanche breakdown is about ten times higher than in silicon. SiC power devices have made remarkable progress in the past five years, demonstrating currents in excess of 100 A and blocking voltages in excess of 19000 V. In this paper we describe the latest progress in three classes of SiC devices: diodes (p-i-n and Schottky), transistors (junction field-effect transistor, metal-oxide-semiconductor field-effect transistor, and bipolar junction transistor), and thyristors (gate turn-off).     

Edge breakdown in 4H-SiC avalanche photodiodes

We report suppression of edge breakdown in mesa-structure SiC avalanche photodiodes (APDs) by employing a 10/spl deg/ sidewall bevel. These devices exhibit low dark currents, <10 pA for a 160-/spl mu/m-diameter device, at the onset of avalanche gain. Two-dimensional raster scans of both beveled and nonbeveled devices, fabricated from the same wafer, show the photocurrent as a function of position and illustrate the spatial properties of avalanche gain in SiC APDs.     

SiC电力电子器件研究现状及新进展

由于硅材料本身的限制,传统硅电力电子器件性能已经接近其极限,碳化硅(SiC)器件的高功率、高效率、耐高温、抗辐照等优势逐渐突显,成为电力电子器件一个新的发展方向.综述了SiC材料、SiC电力电子器件、SiC模块及关键工艺的研究现状,重点从材料、器件结构、制备工艺等方面阐述了SiC二极管、金属氧化物半导体场效应晶体管(MOSFET)、结晶型场效应晶体管(JFET)、双极结型晶体管(BJT)、绝缘栅双极晶体管(IGBT)及模块的研究进展.概述了SiC材料、SiC电力电子器件及模块的商品化情况,最后对SiC材料及器件的发展趋势进行了展望.     

Study of avalanche breakdown and impact ionization in 4H silicon carbide

Epitaxial p-n diodes in 4H SiC are fabricated with uniform avalanche multiplication and breakdown. Photomultiplication measurements were performed to determine electron and hole ionization rates. Theoretical values of critical fields and breakdown voltages in 4H SiC are calculated using the ionization rates obtained. We discuss ionization mechanisms in 4H SiC and make a comparison between silicon carbide and gallium nitride.     

Small-signal gate-to-drain capacitance of MOSFET as a diagnostic tool for hot-carrier induced degradation

In this paper a method for the study of hot-carrier induced charge centers in MOSFETs based on a small-signal gate-to-drain capacitance measurement is described. Numerical modeling and simulation is used to provide an understanding of the effects of spatially localized trapped carriers and interface states on this capacitance. Experimental gate-to-drain capacitance results are presented and compared with charge pumping measurements. This method is used to investigate hot-carrier degradation of n- and p-channel MOSFETs after drain avalanche hot-carrier stress conditions. It is concluded that under this stress condition the degradation of both n- and p-channel devices is due to the trapping of majority carriers and the generation of acceptor type interface states in the top half of the silicon bandgap.     

Improved high-voltage lateral RESURF MOSFETs in 4H-SiC

High-voltage lateral RESURF metal oxide semiconductor field effect transistors (MOSFETs) in 4H-SiC have been experimentally demonstrated, that block 900 V with a specific on-resistance of 0.5 Ω-cm² . The RESURF dose in 4H-SiC to maximize the avalanche breakdown voltage is almost an order of magnitude higher than that of silicon; however this high RESURF dose leads to oxide breakdown and reliability concerns in thin (100-200 nm) gate oxide devices due to high electric field (>3-4 MV/cm) in the oxide. Lighter RESURF doses and/or thicker gate oxides are required in SiC lateral MOSFETs to achieve highest breakdown voltage capability     

Avalanche-induced effects in polysilicon thin-film transistors

A comparison of experimental data and two-dimensional numerical simulations of polysilicon thin-film transistors (TFTs) is presented. It is shown that avalanche multiplication causes both the kink effect in the output characteristics and the reduction of threshold voltage in short-channel device. It is shown that exactly the same physical model for avalanche multiplication gives very good agreement between simulations and experimental data for both these effects. It is demonstrated that it is the presence of grain boundaries or traps in the polysilicon that causes avalanche effects to be much greater than in comparable single-crystal silicon devices     

Development and characterisation of pressed packaging solutions for high-temperature high-reliability SiC power modules

SiC is a wide bandgap semiconductor with better electrothermal properties than silicon, including higher temperature of operation, higher breakdown voltage, lower losses and the ability to switch at higher frequencies. However, the power cycling performance of SiC devices in traditional silicon packaging systems is in need of further investigation since initial studies have shown reduced reliability. These traditional packaging systems have been developed for silicon, a semiconductor with different electrothermal and thermomechanical properties from SiC, hence the stresses on the different components of the package will change. Pressure packages, a packaging alternative where the weak elements of the traditional systems like wirebonds are removed, have demonstrated enhanced reliability for silicon devices however, there has not been much investigation on the performance of SiC devices in press-pack assemblies. This will be important for high power applications where reliability is critical. In this paper, SiC Schottky diodes in pressure packages have been evaluated, including the electrothermal characterisation for different clamping forces and contact materials, the thermal impedance evaluation and initial thermal cycling studies, focusing on the use of aluminium graphite as contact material.     

碳化硅薄膜制备影响因素分析

碳化硅薄膜因其具有一系列优异的特性,被视为制作电子元件的重要材料,性能好、用途广。高质量SiC薄膜的生长,不仅有利于解决自补偿问题,而且有利于解决薄膜中存在应力和杂质等问题,对SiC薄膜的应用,特别是在微电子器件上的应用尤为关键。因此如何制作高质量的碳化硅薄膜是亟待解决的问题。为此,文中从大量试验中,找出了其主要影响因素;从衬底负偏压、工作温度和衬底温度、工作介质、射频功率、工作气压、沉积时间、Gr几个方面进行分析,得出了制备碳化硅薄膜的影响规律。     

等平面化自对准硅雪崩击穿电子发射阵列器件的设计和研究

本文报道了等平面化自对准硅雪崩击穿电子发射阵列器件的结构设计和工艺过程。该器件的电子发射区域边缘的工艺台阶仅为10nm,其自对准的浅砷注入电流通道区宽度仅为3m。与已报道的其它结构硅雪崩击穿电子发射器件相比较,该器件的电流电压特性曲线有更宽的线性区域和更低的通导电阻。本文也对其电子发射特性作了部分介绍。     

SiC 器件在雷达电源中的应用

现代雷达的发展迫切需要电源提升功率密度和效率。基于第三代半导体碳化硅(SiC)材料的功率器件在耐压等级、高频工作、高温性能等方面有较大优势。文中详细阐述了SiC 器件的特性和各类型SiC 功率器件的发展现状,分析了SiC功率器件在雷达电源中的应用方向,并基于SiC 金属氧化物半导体场效应晶体管(MOSFET)设计了阵面电源样机,完成了高开关频率性能测试。实验结果表明:SiC MOSFET 的高频工作能降低系统损耗,并提升电源功率密度。     

Static and dynamic characterization of large-areahigh-current-density SiC Schottky diodes

The static and dynamic characteristics of large-area, high-voltage 4H-SiC Schottky barrier diodes are presented. With a breakdown voltage greater than 1200 V and a forward current in excess of 6 A at 2 V forward bias, these devices enable for the first time the evaluation of SiC Schottky diodes in practical switching circuits. These diodes were inserted into standard test circuits and compared to commercially available silicon devices, the results of which are reported here. Substituting SiC Schottky diodes in place of comparably rated silicon PIN diodes reduced the switching losses by a factor of four, and virtually eliminated the reverse recovery transient. These results are even more dramatic at elevated temperatures. While the switching loss in silicon diodes increases dramatically with temperature, the SiC devices remain essentially unchanged. The data presented here clearly demonstrates the distinct advantages offered by SiC Schottky rectifiers, and their emerging potential to replace silicon PIN diodes in power switching applications     

An optimized avalanche photodiode

The feasibility of a fast, high-gain photodetector based on the phenomenon of avalanche multiplication in semiconductors has been investigated. Based on the process of carrier multiplication in a high electric field, criteria for the design of an optimized avalanche photodiode and for the choice of the best semiconductor material are developed. The device theory of an optimized, realizable avalanche photodiode is presented. A practical silicon device optimized for the detection of light with a wavelength of 9000Å is suggested and design parameters are presented. Details of the fabrication process are given and the performance of experimental devices is compared to the device theory presented. The results of the study indicate that it is possible to achieve a silicon photomultiplier with a quantum efficiency-bandwidth product of the order of 100 GHz for the detection of light up to a wavelength of over 9000Å.     

Silicon carbide benefits and advantages for power electronics circuits and systems

Silicon offers multiple advantages to power circuit designers, but at the same time suffers from limitations that are inherent to silicon material properties, such as low bandgap energy, low thermal conductivity, and switching frequency limitations. Wide bandgap semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), provide larger bandgaps, higher breakdown electric field, and higher thermal conductivity. Power semiconductor devices made with SiC and GaN are capable of higher blocking voltages, higher switching frequencies, and higher junction temperatures than silicon devices. SiC is by far the most advanced material and, hence, is the subject of attention from power electronics and systems designers. This paper looks at the benefits of using SiC in power electronics applications, reviews the current state of the art, and shows how SiC can be a strong and viable candidate for future power electronics and systems applications.     

Design and research of quasi-planar self-aligned silicon avalanche electron emission array

The device structure and technical processings of quasi-planar self-aligned silicon avalanche electron emission array arc introduced. The processing step at the edge of electron emission region is about 10nm only and the width of self-aligned current channel of shallow As implantation is about 3μm. Its I-V characteristics show a larger linear region and lower series resistance than that of the previous silicon avalanche electron emission devices. Some of the electron emission characteristics are also discussed in this paper.     

Comparison of channel current and drain avalanche current-induced hot-carrier effects in MOSFET's

Hot-carrier effects induced by the channel current and the drain avalanche current in short-channel MOSFET's are investigated and compared by characterizing the substrate current at different stages of stress. Not only does the drain avalanche stress (DAS) degrade devices much faster than the triode region stress (TCS) does, but the substrate current versus the stress time shows a characteristic difference between the DAS mode and the TCS mode. The difference is that the DAS mode involves localized interface trap generation near the drain and more widely distributed hole trapping in the oxide, while in the TCS mode the mechanism is mainly localized electron trapping in the oxide.     

碳化硅器件发展概述

概要介绍了第三代半导体材料碳化硅(SiC)在高温、高频、大功率器件应用方面的优势,结合国际上SiC肖特基势垒二极管,PiN二极管和结势垒肖特基二极管的发展历史,介绍了SiC功率二极管的最新进展,同时对我国宽禁带半导体SiC器件的研究现状及发展方向做了概述及展望。     

The potential of diamond and SiC electronic devices for microwaveand millimeter-wave power applications

The potential of SiC and diamond for producing microwave and millimeter-wave electronic devices is reviewed. It is shown that both of these materials possess characteristics that may permit RF electronic devices with performance similar to or greater than what is available from devices fabricated from the commonly used semiconductors, Si, GaAs, and InP. Theoretical calculations of the RF performance potential of several candidate high-frequency device structures are presented: the metal semiconductor field-effect transistor (MESFET), the impact avalanche transit-time (IMPATT) diode, and the bipolar junction transistor (BJT). Diamond MESFETs are capable of producing over 200 W of X-band power as compared to about 8 W for GaAs MESFETs. Devices fabricated from SiC should perform between these limits. Diamond and SiC IMPATT diodes also are capable of producing improved RF power compared to Si, GaAs, and InP devices at microwave frequencies. RF performance degrades with frequency and only marginal improvements are indicated at millimeter-wave frequencies. Bipolar transistors fabricated from wide bandgap material probably offer improved RF performance only at UHF and low microwave frequencies     

Laser interferometric method for ns-time scale thermal mapping of Smart Power ESD protection devices during ESD stress

A backside heterodyne interferometric technique is presented to study thermal effects in smart-power electrostatic discharge (ESD) protection devices during the ESD stress. The temperature increase in the device active area causes an increase in the silicon refractive index (thermo-optical effect) which is monitored by the time-resolved measurements of optical phase changes. Thermal dynamics and spatial temperature distribution in different types of npn transistor structures biased in the avalanche multiplication or snapback regime are studied with nanosecond time and micrometer spatial resolution. The activity and inactivity of the bipolar transistor action is indicated by the dominant signal arising from the emitter or base region, respectively. Hot spots have been found at the edges of the structures and attributed to the current crowding effect in the emitter.     

6H-SiC单极功率器件性能的温度关系

基于碳化硅材料电离系数和迁移率的温度依赖性 ,利用有效电离系数的 Fulop近似 ,推出了 6 H- Si C单极性功率器件击穿电压和比导通电阻的温度依赖性解析表达式 .理论预言的击穿电压和临界电场与先前的实验结果基本一致 (误差小于 10 % ) ,验证了理论模型的适用性