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.     

Nanoarchitectonics for Heterogeneous Integrated Nanosystems

Based on projections of the International Roadmap for Semiconductors (ITRS), the continued scaling of complementary metal-oxide semiconductor (CMOS) devices will face severe technical challenges. Among the most critical are power dissipation and device-level variabilities that will make circuit design very difficult. Potential device-level solutions that take advantage of new functional materials, self-assembly processes, low dissipation nanoscale devices, and architectures that aim in sustaining Moore's law beyond the ITRS are discussed in this paper. Two potential paths forward are clear at this point. One path is to continue increasing chip-scale functional throughput by looking at new functional materials at atomic and molecular levels for assembly into new low-power devices with different logic state variables that can better tolerate variabilities. Another distinct approach is to increase chip-scale functionality by exploiting the heterogeneous integration of materials, such as compound semiconductors on silicon as enabled by the unique features in nanoscale epitaxy and self-assembly on a common substrate. This paper will discuss some possible methods forward in maintaining scaled CMOS and going beyond the roadmap.     

Engineering Route for Stretchable, 3D Microarchitectures of Wide Bandgap Semiconductors for Biomedical Applications

Wide bandgap (WBG) semiconductors have attracted significant research interest for the development of a broad range of flexible electronic applications, including wearable sensors, soft logical circuits, and long-term implanted neuromodulators. Conventionally, these materials are grown on standard silicon substrates, and then transferred onto soft polymers using mechanical stamping processes. This technique can retain the excellent electrical properties of wide bandgap materials after transfer and enables flexibility; however, most devices are constrained by 2D configurations that exhibit limited mechanical stretchability and morphologies compared with 3D biological systems. Herein, a stamping-free micromachining process is presented to realize, for the first time, 3D flexible and stretchable wide bandgap electronics. The approach applies photolithography on both sides of free-standing nanomembranes, which enables the formation of flexible architectures directly on standard silicon wafers to tailor the optical transparency and mechanical properties of the material. Subsequent detachment of the flexible devices from the support substrate and controlled mechanical buckling transforms the 2D precursors of wide band gap semiconductors into complex 3D mesoscale structures. The ability to fabricate wide band gap materials with 3D architectures that offer device-level stretchability combined with their multi-modal sensing capability will greatly facilitate the establishment of advanced 3D bio-electronics interfaces.     

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.     

Some aspects on ruggedness of SiC power devices

This article is on effects that can destroy SiC power semiconductor devices. The failure physics in SiC devices are discussed based on the well understood effects in silicon devices. In some device properties, such as surge current, short circuit, static avalanche and dynamic avalanche, SiC has significant possible advantages compared to silicon. For cosmic ray stability, there are no unique results. Regarding thermal mechanical stress on interface materials, SiC is more challenging. The same may hold for electrical stress in passivation layers at the junction termination.     

Reliability considerations for recent Infineon SiC diode releases

Silicon carbide (SiC) has long been shown to be one of the most promising materials for high-voltage power semiconductor devices. New device technologies and products have lead to an ever increasing size and variety of the markets addressed by SiC. The specific material properties and the new applications served by SiC devices give rise to specific reliability requirements, reaching beyond the scope of standard tests established for silicon based devices. Here, we show details of Infineon’s strategy to ensure high device reliability even under extreme operating conditions encountered in the field. E.g., an especially tailored dynamic reverse bias test shows that Infineon’s new 1200 V SiC Schottky diodes can be continuously operated at high voltage slopes of 120 V/ns under the conditions specified in this paper.     

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。     

S波段连续波SiC功率MESFET

利用国产SiC外延材料和自主开发的SiC器件工艺加工技术,实现了SiC微波功率器件在S波段连续波功率输出大于10W、功率增益大于9dB、功率附加效率不低于35%的性能样管,初步显现了SiC器件在S波段连续波大功率、高增益方面的优势。与以往的硅微波功率器件相比,在同样的频率和输出功率下,SiC微波功率器件的体积不到Si器件的1/7,重量不到Si器件的20%,其功率增益较Si器件提高了3dB以上,器件效率也得到了相应的提高。同时由于SiC微波功率器件的输入、输出阻抗要明显高于Si微波功率器件,在一定程度上可以简化或不用内匹配网络来得到比较高的微波功率增益,这就为器件的小体积、低重量奠定了基础,也为器件的大功率输出创造了条件。     

Progress in projection and large-area displays

A new class of compact high-definition electronic projection systems has emerged that are based on microdisplays. Very large scale integration process technology is adapted to fabricate the three classes of microdisplays: (1) transmissive liquid crystal on high-temperature polysilicon/quartz; (2) microelectromechanical devices on silicon; (3) and reflective liquid crystal on silicon. A variety of system architectures are discussed. Key ancillary technologies include small arc lamps, color separation and recombination optics, and rear-projection screens     

Positive temperature coefficient of breakdown voltage in 4H-SiC pnjunction rectifiers

It has been suggested that once silicon carbide (SiC) technology overcomes some crystal growth obstacles, superior SiC semiconductor devices would supplant silicon in many high-power applications. However, the property of positive temperature coefficient of breakdown voltage, a behavior crucial to realizing excellent power device reliability, has not been observed in 4H-SiC, which is presently the best-suited SiC polytype for power device implementation. This paper reports the first experimental measurements of stable positive temperature coefficient behavior observed in 4H-SiC pn junction rectifiers. This research indicates that robust 4H-SiC power devices with high breakdown reliability should be achievable after SiC foundries reduce material defects such as micropipes, dislocations, and deep level impurities     

Some Critical Materials and Processing Issues in SiC Power Devices

There has been a rapid improvement in SiC materials and power devices during the last few years. However, the materials community has overlooked some critical issues, which may threaten the emergence of SiC power devices in the coming years. Some of these pressing materials and processing issues will be presented in this paper. The first issue deals with the possibility of process-induced bulk traps in SiC immediately under the SiC/SiO₂ interface, which may be involved in the reduction of effective inversion layer electron mobility in SiC metal–oxide–semiconductor field-effect transistor (MOSFETs). The second issue addresses the effect of recombination-induced stacking faults (SFs) in majority carrier devices such as MOSFETs, Schottky diodes, and junction field-effect transistors (JFETs). In the past it was assumed that the SFs only affect the bipolar devices such as PiN diodes and thyristors. However, most majority carrier devices have built-in p–n junction diodes, which can become forward biased during operation in a circuit. Thus, all high-voltage SiC devices are susceptible to this phenomenon.     

Characterization of SiC Schottky diodes at different temperatures

The emergence of silicon carbide (SiC) based power semiconductor switches, with their superior features compared with silicon (Si) based switches, has resulted in substantial improvement in the performance of power electronics converter systems. These systems with SiC power devices have the qualities of being more compact, lighter, and more efficient; thus, they are ideal for high-voltage power electronics applications. In this study, commercial Si pn and SiC Schottky diodes are tested and characterized, their behavioral static and loss models are derived at different temperatures, and they are compared with respect to each other.     

System on Wafer: A New Silicon Concept in SiP

System integration is clearly a driving force for innovation in packaging. The need for miniaturization has led to new architectures that combine disparate technologies and materials. Today several different approaches have been developed. These include technologies like system in package. In this way, a new concept for heterogeneous integration is currently being developed at CEA-LETI and is called system on wafer (SoW). This concept is based on a chip to wafer approach. Every component is achieved by using wafer-level technologies, and the final system is performed by single component mounting on a silicon substrate. The main strength of this approach is to use silicon as a substrate for components and for basic support. To perform the SoW, a generic technological toolbox is needed. This includes every standard packaging technology such as flip chip, signal rerouting, and passive component integration as well as new advanced technologies such as microelectromechanical systems packaging, advanced interconnections, energy source integration, integrated cooling, or silicon through vias. In this paper, the SoW concept will be presented and the generic toolbox for SoW achievement will be described.      

Investigations on high temperature polyimide potentialities for silicon carbide power device passivation

The operation of silicon carbide (SiC) power devices under severe conditions requires the development of thermally, electrically and chemically stable package. Passivation layer provides electrical insulation and environmental protection for the SiC die. As higher junction temperature and higher electric field can be reached within SiC component, consideration must be given to the thermal stability of the dielectric properties of the material in the die surrounding. Due to their supposed high operating temperature and dielectric strength, spin coated polyimide materials appear as a possible candidate for such passivation and insulation purposes. In this paper, we study the potentialities of a high temperature polyimide from HD Microsystems, for SiC power device passivation, at temperature up to 300 °C.     

Si–C multilayer quasi crystals preparation by DC magnetron sputtering

Silicon carbide (SiC) is becoming one of the most important electronic materials in recent years. Single crystalline SiC is a wide-bandgap semiconductor, which finds a wide range of applications in high temperature, power consuming, and fast-acting electron devices. Common methods applied for silicon carbide films deposition are: plasma-enhanced CVD under plasma decomposition of organic compounds such as CH₄, C₂H₂, C₃H₈. These methods are complicated and expensive.

In this work we grew silicon–carbon films as Si–C thin film multilayer system with successive layers of Si and C both of equal thicknesses. The Si–C systems grown in our experiments consisted of 40 sub-layers, deposited by DC magnetron sputtering on silicon, on glass, and on Au substrates in argon plasma environment. Sputtering was provided continuously from two targets: graphite and single-crystalline silicon. Optical and electro-physical properties of the deposited thin film systems were investigated. Relative permittivity of the grown thin film systems was found to be the main and most important parameter of the Si–C system.     

Integration of SiC-1D nanostructures into nano-field effect transistors

We report on the integration and the electrical transport properties of silicon carbide-based one-dimensional nanostructures into field effect transistors. Different kinds of SiC-based 1D nanostructures have been used: 3C– and 4H–SiC nanowires obtained by a plasma etching process, Si–SiC core–shell nanowires and SiC nanotubes both obtained by a carburization route of silicon nanowires.     

A Review of Acoustic Devices Based on Suspended 2D Materials and Their Composites

Acoustic devices play an increasingly important role in modern society for information technology and intelligent systems, and recently significant progress has been made in the development of communication, sensing, and energy transduction applications. However, conventional material systems, such as polymers, metals and silicon, show limitations to fulfill the evolving requirements for high-performance acoustic devices of small size, low power consumption, and multifunctional capabilities. 2D materials hold the promise in overcoming the development bottleneck of acoustic devices aforementioned, given their atomic-thin thickness, extensive surface area, superior physical properties, and remarkable layer-stacking tunability. By suspending the 2D materials, mechanical and thermal disruption from substrate will be eliminated, which will enable the development of new classes of acoustic devices with unprecedented sensitivity and accuracy. In this review, the recent progress of acoustic devices based on suspended 2D materials and their composites, especially applications in the audio frequency, static pressure, and ultrasonic frequency range, is briefly summarized, emphasizing the advantageous properties of suspended 2D materials and related outstanding device performance. Together with the development of 2D membrane synthesis, transfer, as well as microelectromechanical fabrication process, suspended 2D materials will shed light on the next-generation high-performance acoustic devices.     

β-SiC-on insulator waveguide structures for modulators and sensor systems

In this work waveguide structures using the cubic polytype of SiC are analyzed. The β-SiC-on-insulator wageguides were fabricated by two different methods. In the first case, a technological process similar to that used for SIMOX material was used, a buried SiO₂ layer being formed by high-energy (2 MeV) ion implantation of oxygen in SiC/Si wafers. For the second case, the heteroepitaxy of SiC on SOI (SIMOX) wafers was used. The losses of the waveguides have been measured at 0.633, 1.3 and 1.55 μm in both TE and TM polarization and a detailed analysis and interpretation of the different loss mechanisms is presented. Using these two types of waveguides we have designed waveguide modulators using the Pockels effect. A 2D semiconductor device simulator was used to determine the electric field configuration in a double-Schottky diode structure and the local modulation of the refractive index was used to determine the effective index modulation of the guided mode. Optical simulations were performed using the spectral index and the effective index methods. Different 2D geometries are analyzed and the material parameters needed for fabricating such a device are determined. Such devices have potential for high-speed Si-based photonic devices compatible with silicon technology.     

3D finite element modeling of 3D C2W (chip to wafer) drop test reliability: Optimization of internal architecture and materials

3D-WLSiP appears as a way to keep increasing density of microelectronic components. The C2W 3D integration use wafer-level processes to improve throughput. This technology gives a high yield and a good flexibility for the choice of internal architectures and assembling techniques. The reliability of 3D components has to be evaluated on mechanical demonstrator with daisy chain before real production. Modeling has proven to be a very efficient tool for design optimization. In this paper, 3D FEM modeling and submodeling techniques are employed to compare the dynamic response of several 3D C2W components under drop test loading conditions. The impacts of possible errors in thin layers elastic modulus estimation are studied. The behavior of the Face To Face (F2F) and the Back To Face (B2F) design for 3D integration are compared. The effects of TSVs repartition in silicon die and molding resin’s mechanical properties are discussed. The reliability evaluation criterion is chosen as maximum shear plastic strain of critical bump. The results have been used in choosing of the optimal design and materials properties for real production.