Ni/4H-SiC肖特基势垒二极管研制

采用微电子平面工艺,高真空电子束热蒸发金属Ni分别作肖特基接触和欧姆接触,二级场限环终端表面保护,研制出Ni/4H-SiC肖特基势垒二极管(SBD)。I-V特性测量说明,Ni/4H-SiCSBD有较好的整流特性,热电子发射是其主要的运输机理。反向击穿电压达1500V,理想因子为1.2,肖特基势垒高度为0.92eV。     

一种高压4H-SiC二极管改进场限环结终端结构

设计了一种用于3.3 kV4H-SiC肖特基二极管的场限环(FLR)结终端保护结构。该结终端保护结构是通过在高能离子注入形成二极管p+有源区的同时在结边缘形成多个不同间距的p+场限环来实现的,以避免多次离子注入。借助半导体数值仿真软件Silvaco,对制备二极管所用的4H-SiC材料外延层耐压特性进行了仿真验证;对场限环的环间距和场限环宽度进行了优化,形成由34个宽度5μm的场限环构成的场限环结终端结构。以此为基础,采用4英寸(1英寸=2.54 cm)n型4H-SiC外延片成功制备了3.3 kV4H-SiC二极管器件。简述了制备工艺流程,给出了部分关键工艺参数。对二极管芯片进行了在片测试和分析,反向漏电流密度1 mA/cm2时的击穿电压约为3.9 kV,且70%以上的二极管耐压可达到3.6 kV以上,验证了这一场限环结终端的可行性。     

Mo/4H-SiC肖特基势垒二极管的研制

采用微电子平面工艺,射频溅射Mo作肖特基接触,电子束热蒸发金属Ni作欧姆接触,三级场限环终端表面保护.并通过对Mo接触进行合理的高温退火,不降低理想因子和反向耐压特性情况下,有效控制肖特基势垒高度在1.2～1.3 eV范围内,成功研制出高耐压低损耗Mo/4H-SiC肖特基势垒二极管.其特性测试结果为:击穿电压Vb为3000V,串联导通电阻Ron为9.2mΩ·cm2,Vb2/Ron为978MW/cm2.     

Mo/4H-SiC肖特基势垒二极管的研制

采用微电子平面工艺,射频溅射Mo作肖特基接触,电子束热蒸发金属Ni作欧姆接触,三级场限环终端表面保护.并通过对Mo接触进行合理的高温退火,不降低理想因子和反向耐压特性情况下,有效控制肖特基势垒高度在1.2～1.3 eV范围内,成功研制出高耐压低损耗Mo/4H-SiC肖特基势垒二极管.其特性测试结果为:击穿电压Vb为3000V,串联导通电阻Ron为9.2mΩ·cm2,Vb2/Ron为978MW/cm2.     

Ni，Ti/4H-SiC肖特基势垒二极管

采用本实验室生长的4H-SiC外延片,分别用高真空电子束蒸Ni和Ti做肖特基接触金属,Ni合金作欧姆接触,SiO_2绝缘环隔离减小高压电场集边效应等技术,制作出4H-SiC肖特基势垒二极管(SBD)。该器件在室温下反向击穿电压大于600 V,对应的漏电流为2.00×10~(-6)A。对实验结果分析显示,采用Ni和Ti作肖特基势垒的器件的理想因子分别为1.18和1.52,肖特基势垒高度为1.54 eV和1.00 eV。实验表明,该器件具有较好的正向整流特性。     

具有场限环终端的6500 V 4H-SiC结势垒肖特基二极管的研制

阐述了6 500 V4H-SiC结势垒肖特基(JBS)二极管的设计、仿真和制备过程,并对流片结果进行了测试,分析了测试结果与仿真结果差异的原因。通过仿真对比分析了漂移区厚度、掺杂浓度、有源区p+区和场限环终端参数对器件电学特性的影响,数值模拟优化了器件元胞和终端结构的漂移区、有源区和场限环的结构参数。根据模拟结果,4H-SiC漂移区掺杂浓度为1.08×1015 cm-3、厚度为60μm,采用经过优化的70个场限环终端结构,通过完整的工艺流程,完成6 500 V4H-SiC JBS的制备。测试结果显示,室温下当6 500 V4H-SiC JBS正向导通电流密度达到3.53×105 A/m2时,正向压降为4 V,器件的反向击穿电压约为8 000 V。     

3300 V-10 A SiC肖特基二极管北大核心CSCD

利用一次离子注入同时形成有源区和结终端结构,实现3 300 V 4H-SiC肖特基二极管。器件的正向电压为1.7 V时,电流达到10.3 A,相应电流密度为100 A/cm2,比导通电阻为7.77 mΩ·cm2。在3 300 V反向偏置电压下反向漏电流为226μA。测试同一晶圆上的pn二极管显示,设计的场限环结终端击穿电压可以达到4 000 V,达到仿真结果的95%。分析发现肖特基二极管的漏电流主要由肖特基接触的热场电子发射产生,有源区的肖特基接触线宽直接影响器件的正向电流密度和反向漏电流。设计合适的肖特基接触宽度是实现高性能器件的关键。     

3300 V-10 A SiC肖特基二极管

利用一次离子注入同时形成有源区和结终端结构,实现3 300 V 4H-SiC肖特基二极管。器件的正向电压为1.7 V时,电流达到10.3 A,相应电流密度为100 A/cm2,比导通电阻为7.77 mΩ·cm2。在3 300 V反向偏置电压下反向漏电流为226μA。测试同一晶圆上的pn二极管显示,设计的场限环结终端击穿电压可以达到4 000 V,达到仿真结果的95%。分析发现肖特基二极管的漏电流主要由肖特基接触的热场电子发射产生,有源区的肖特基接触线宽直接影响器件的正向电流密度和反向漏电流。设计合适的肖特基接触宽度是实现高性能器件的关键。     

2700V4H-SiC结势垒肖特基二极管

在76.2 mm 4H-SiC晶圆上采用厚外延技术和器件制作工艺研制的结势垒肖特基二极管(JBS).在室温下,器件反向耐压达到2700 V.正向开启电压为0.8V,在VF=2V时正向电流密度122 A/cm2,比导通电阻Ron=8.8 mΩ·cm2.得到肖特基接触势垒qφв=1.24 eV,理想因子n=1.     

基于结终端扩展的4H-SiC肖特基势垒二极管研制

采用高真空电子束热蒸发金属Ni分别作肖特基接触和欧姆接触,离子注入形成结终端扩展表面保护,研制出Ni/4H-SiC肖特基势垒二极管(SBD)。I-V特性测量说明,Ni/4H-SiCSBD有较好的整流特性,热电子发射是其主要的运输机理。实验测量其反向击穿电压达1800V,且反向恢复特性为32ns。     

Fabrication and characteristics of a 4H-SiC junction barrier Schottky diode

4H-SiC junction barrier Schottky(JBS)diodes with four kinds of design have been fabricated and characterized using two different processes in which one is fabricated by making the P-type ohmic contact of the anode independently,and the other is processed by depositing a Schottky metal multi-layer on the whole anode.The reverse performances are compared to find the influences of these factors.The results show that JBS diodes with field guard rings have a lower reverse current density and a higher breakdown voltage,and with independent P-type ohmic contact manufacturing,the reverse performance of 4H-SiC JBS diodes can be improved effectively. Furthermore,the P-type ohmic contact is studied in this work.     

Experimental 4<Emphasis Type="Italic">H</Emphasis>-SiC junction-barrier Schottky (JBS) diodes

4H-SiC junction-barrier Schottky (JBS) diodes have been fabricated with local p–n junctions under the Schottky contact formed by nonequilibrium diffusion of boron. Static and dynamic characteristics of the JBS diodes are compared with those of similar 4H-SiC Schottky diodes. It is shown that, compared with ordinary Schottky diodes, the JBS diodes have leakage currents that are, on average, a factor of 200 lower at the same reverse bias. The reverse recovery charge is the same for both types of diodes and equal to the charge of majority carriers removed from the n-type base region in switching.     

Study of 4H-SiC JBS Diodes Fabricated with Tungsten Schottky Barrier

Tungsten is a suitable metal contact for high-temperature applications. We fabricated 1.7-kV and 6-kV 4H-SiC junction barrier Schottky (JBS) diodes with a tungsten Schottky contact with different geometries, and their forward characteristics were measured up to 300°C. The 1.7-kV diodes exhibited unipolar conduction up to 6 V at 275°C, whereas 6-kV diodes showed ideal on-resistance, R _on. An optimized JBS design permits a higher breakdown voltage to be obtained than for the pure Schottky diode, with a reasonable increase (10%) of the on-resistance. Results demonstrate the feasibility of tungsten JBS diodes for fast-switching, high-voltage, and high-temperature applications.     

Effect of crystallographic defects on the reverse performance of 4H-SiC JBS diodes

A quantitative analysis of the effect of crystallographic defects on the performance of 4H-SiC junction barrier Schottky (JBS) diodes was performed. It has been shown that higher leakage current in diodes is associated with a greater number of elementary screw dislocations. Further, threading dislocation pair arrays were observed in some of the fabricated devices and, for the first time, the role of such defects on JBS reverse leakage currents is investigated.     

高性能SiC整流二极管研究

在n型4H-SiC单晶导电衬底上制备了具有MPS(merged p-i-n Schottky diode)结构和JTE(junction termination extension)结构的肖特基势垒二极管。通过高温离子注入及相应的退火工艺,进行了区域性p型掺杂,形成了高真空电子束蒸发Ni/Pt/Au复合金属制备肖特基接触,衬底溅射Ti W/Au并合金做欧姆接触,采用场板和JTE技术减小高压电场集边效应。该器件具有良好的正向整流特性和较高的反向击穿电压。反向击穿电压可以达到1300V,开启电压约为0.7V,理想因子为1.15,肖特基势垒高度为0.93eV,正向电压3.0V时,电流密度可以达到700A/cm2。     

A 2-dimensional fully analytical model for design of high voltage junction barrier Schottky (JBS) diodes

A physics-based closed form analytical model for the reverse leakage current of a high voltage junction barrier Schottky (JBS) diode is developed and shown to agree with experimental results. Maximum electric field “seen” by the Schottky contact is calculated from first principles by a 2-dimensional method as a function of JBS diode design parameters and confirmed by numerical simulations. Considering thermionic emission under image force barrier lowering and quantum mechanical tunneling, electric field at the Schottky contact is then related to reverse current. In combination with previously reported forward current and resistance models, this gives a complete I-V relationship for the JBS diode. A layout of interdigitated stripes of P-N and Schottky contacts at the anode is compared theoretically with a honeycomb layout and the 2-D model is extended to the 3-D honeycomb structure. Although simulation and experimental results from 4H-Silicon Carbide (SiC) diodes are used to validate it, the model itself is applicable to all JBS diodes.     

Analytical Modeling of High-Voltage 4H-SiC Junction Barrier Schottky (JBS) Rectifiers

We develop a new analytical model for the junction barrier Schottky (JBS) rectifier and apply it to high-voltage 4H-SiC JBS rectifiers. This model uses a novel method to approximate the electric field at the Schottky contact, which is together with the Fowler–Nordheim tunneling equation to accurately calculate the reverse leakage current of a high-voltage 4H-SiC JBS rectifier. The forward on-resistance of a high-voltage 4H-SiC JBS rectifier consists of several components, which are dominated by the spreading resistances in the drift layer. Moreover, this model has been verified by comparing the simulation and experimental results, and they are shown to be in good agreement.      

Advanced High-Voltage 4H-SiC Schottky Rectifiers

This paper presents advanced 4H-SiC high-voltage Schottky rectifiers with improved performance when compared to conventional 4H-SiC Schottky rectifiers. Two types of 4H-SiC junction barrier Schottky (JBS) rectifiers have been explored. These rectifiers offer Schottky-like ON-state and fast switching characteristics, while their OFF-state characteristics have a low leakage current similar to that of the PiN junction rectifier. Planar 4H-SiC JBS rectifiers, with more than 1-kV blocking capability and orders of magnitude lower reverse leakage current than that of conventional SiC Schottky rectifiers, have been demonstrated. In addition, a novel device structure, called lateral channel JBS rectifier, was designed and experimentally demonstrated in 4H-SiC with up to 1.5-kV blocking capability and pinlike reverse characteristics.      

4H-SiC SBD和JBS退火研究

在4H-SiC外延材料上制备了SBD和JBS器件,研究并分析了退火温度对这两种器件正反向特性的影响。结果表明,低于350℃退火可同时提高SBD和JBS的正反向特性。当退火温度高于350℃时,二者的正向特性都出现退化,SBD退化较JBS更为严重。JBS阻断电压随退火温度升高而增大,在退火温度高于450℃时增加趋势变缓。SBD阻断电压随退火温度升高先升后降,在500℃退火时达到一个最大值。可见一定程度的退火有助于提高4H-SiCSBD和JBS器件的正反向特性,但须考虑其对正反向特性的不同影响。综合而言,退火优化后JBS优于SBD器件性能。