高压4H-SiC BJT功率器件特性研究

发布时间：2018-08-27 20:00

【摘要】：碳化硅(Silicon Carbide, SiC)作为一种第三代半导体,具有禁带宽度大、临界击穿电场大、热导率大,使其特别适用于高温高压等领域中应用。在SiC的多种同质异型体中,4H-SiC具有较高的电子迁移率和较低的各向异性,使其更具有研究和商业价值。作为一种电流控制型器件,4H-SiC双极型晶体管(4H-SiC BJT)具有较低的导通电阻、较低的开态损耗以及不存在二次击穿的优点,但目前器件仍面临着电流增益低,长期工作下器件退化等问题,对4H-SiC BJT研究具有重要意义。本文基于二维数值分析的方法,对4H-SiC BJT进行了研究。为了得到较为准确的仿真结果,首先建立了器件仿真模型并给出了参数,其中包括杂质不完全电离模型、SRH及Auger复合模型等。其次,通过仿真分析了影响器件性能的参数,包括发射区、基区及漂移区参数对器件耐压、导通电阻及电流增益的影响；以1200V4H-SiC BJT为目标,优化了器件参数,最终得到了共发射极电流增益为39,比导通电阻为3.7mΩ·cm2,理想击穿电压为1580V的高压4H-SiC BJT功率器件。考虑边缘电场集中,设计场限环和结终端扩展两种结终端,成功降低了电场峰值,避免了边缘电场集中现象,两种结终端的击穿电压都达到了1470V左右,达到了理想平行平面结的93%。最后,针对外基区表面复合效应导致低电流增益的问题,本文从器件结构和工艺两个方向进行了探讨。在器件结构方面,提出了发射极金属延伸和P型钝化层两种新型器件结构；发射极金属延伸结构通过控制外基区表面电势调制表面载流子浓度分布,从而降低外基区表面复合速率。通过仿真发现外基区表面复合效应明显减弱,器件共发射极电流增益分别提高了63%。P型钝化层新型器件结构则是通过在外基区引入高浓度P型钝化层,使外基区电阻大大降低,通过仿真优化后的器件共发射极电流增益提高了117%。从工艺上,通过对比不同氧化退火实验条件下SiC/SiO2界面质量发现,NO退火确实能减小界面态密度,这与之前报道文献一致；另外适当提高退火温度能够提高界面质量。
[Abstract]:As a kind of third generation semiconductor, silicon carbide (Silicon Carbide, SiC) has large band gap, large critical breakdown electric field and large thermal conductivity, which makes it especially suitable for high temperature and high pressure applications. 4H-SiC has higher electron mobility and lower anisotropy in various homotropic SiC bodies, which makes it more valuable for research and commerce. As a current-controlled device, 4H-SiC bipolar transistor (4H-SiC BJT) has the advantages of low on-resistance, low on-state loss and no secondary breakdown, but the current gain is still low. The problem of device degradation in long-term operation is of great significance to the study of 4H-SiC BJT. Based on the method of two-dimensional numerical analysis, 4H-SiC BJT is studied in this paper. In order to obtain more accurate simulation results, the device simulation model is established and the parameters are given, including impurity incomplete ionization model and Auger composite model. Secondly, the influence of the parameters of the device, including the emission region, base region and drift region, on the voltage resistance, on-resistance and current gain of the device is analyzed by simulation, and the parameters of the device are optimized with 1200V4H-SiC BJT as the target. Finally, a high voltage 4H-SiC BJT power device with a common emitter current gain of 39 and an ideal breakdown voltage of 1580V with a specific on-resistance of 3.7 m 惟 cm2, is obtained. Considering the edge electric field concentration, two kinds of junction terminals are designed, which are field limiting loop and junction terminal expansion. The peak value of electric field is reduced successfully, and the phenomenon of edge electric field concentration is avoided. The breakdown voltage of both junction terminals is about 1470V. The ideal parallel plane junction is reached at 933. Finally, aiming at the problem of low current gain caused by the surface recombination effect in the outer base region, the structure and process of the device are discussed in this paper. In terms of device structure, two new device structures, emitter metal extension and P-type passivating layer, are proposed, which modulate the surface carrier concentration distribution by controlling the surface potential of the external base region. Thus, the surface recombination rate of the outer base region is reduced. The simulation results show that the surface recombination effect of the outer base region is obviously weakened, and the common emitter current gain of the device is increased by 63. P passivating layer. The new device structure is based on the introduction of high concentration P passivation layer in the outer base region, which greatly reduces the external base resistance. The emitter current gain is improved by simulation. From the process point of view, by comparing the interfacial quality of SiC/SiO2 under different oxidation annealing conditions, it is found that the interfacial state density can be reduced by annealing with no, which is consistent with the previous reports, and the interfacial quality can be improved by increasing annealing temperature appropriately.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN322.8

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