高压快速软恢复二极管研究

发布时间：2018-11-01 20:20

【摘要】：随着功率器件向着大容量、高频率方向的发展,对续流二极管也提出了更严格的要求,硅作为自然界最丰富的材料之一,以硅为基础的功率器件仍将是一个相当长时间范围内的主流器件。因此,研究硅基功率二极管的快速软恢复技术,进一步优化或改进器件结构,获得在应用中满意的反向恢复特性具有很现实的实际意义和应用价值。本文首先简要分析了硅基功率二极管的反向恢复特性原理,指出了要想获得软关断特性,关键在于实现器件内部载流子的反转分布;在此基础上,提出了一种场电荷抽取二极管结构,该结构对阴极进行改进,在阴极部分引入P+层,在关断末期,通过器件内部电场的作用,使得阴极的P+部分注入空穴,减缓了反向恢复电流的变化率,从而获得软关断特性;并简要介绍了表征功率二极管反向恢复特性的参数。接着,详细讨论了场电荷抽取二极管的结构设计,从理论上探讨了器件反向恢复特性与结构之间的关系,并给出它们之间的数学计算式;在此基础上,设计了一个150A/1200V的场电荷抽取二极管结构,采用数值模拟的方法验证了器件的正向导通特性、反向阻断特性和动态开关特性。结果表明:场电荷抽取二极管结构能够实现快速软关断,相比少子寿命技术二极管其关断损耗更小。然后,对场电荷抽取二极管结构的反向恢复特性作了进一步的探讨,讨论了在低温、高换向率dtdi下,器件反向恢复特性的变化情况。结果发现:场电荷抽取二极管在上述条件下,仍能够实现软关断,具有较强的耐动态雪崩的能力。最后,优化了器件结构参数,使得器件反向特性到达最佳。在结构研究的基础上,更进一步的研究了场电荷抽取二极管器件的制作工艺,由于器件结构阴极比较复杂,提出了采用两步扩散法的工艺方案,设计了场电荷抽取二极管的工艺流程,采用数值模拟技术,模拟了整个工艺方案,并验证了工艺制作完成后,器件的各种特性参数。结果表明:器件各种特性参数符合预期设计,表明该工艺方案可行。最后,本论文的研究成果对于高压快速软关断二极管的开发和设计有一定的参考价值和实际意义。
[Abstract]:With the development of power devices in the direction of large capacity and high frequency, more stringent requirements have been put forward for the continuous current diodes. Silicon is one of the most abundant materials in nature. Silicon-based power devices will remain a mainstream device for a long time. Therefore, it is of practical significance and practical value to study the fast soft recovery technology of silicon based power diode, to further optimize or improve the device structure, and to obtain satisfactory reverse recovery characteristics in application. In this paper, the principle of reverse recovery characteristics of silicon based power diode is briefly analyzed, and the key to obtain soft turn-off characteristic is to realize the reverse distribution of carriers in the device. On this basis, a structure of field charge extraction diode is proposed. The structure improves the cathode and introduces P layer into the cathode. At the end of turn-off, the P part of the cathode is injected into the hole through the action of the electric field inside the device. The change rate of reverse recovery current is slowed down and the soft turn-off characteristic is obtained. The parameters that characterize the reverse recovery characteristics of power diodes are briefly introduced. Then, the structure design of the field charge extraction diode is discussed in detail, and the relationship between the reverse recovery characteristic and the structure of the device is discussed theoretically, and the mathematical formula between them is given. Based on this, a field charge decimation diode structure of 150A/1200V is designed, and the forward, reverse blocking and dynamic switching characteristics of the device are verified by numerical simulation. The results show that the structure of field charge decimation diode can realize fast soft turn-off, and its turn-off loss is smaller than that of minority carrier diode. Then, the reverse recovery characteristics of the field charge decimation diode structure are further discussed, and the change of the reverse recovery characteristics of the device at low temperature and high commutation rate dtdi is discussed. The results show that the field charge decimation diode can still achieve soft turn-off under the above conditions and has a strong ability to resist dynamic avalanche. Finally, the structure parameters of the device are optimized to optimize the reverse characteristics of the device. On the basis of the structure research, the fabrication process of the field charge extraction diode device is further studied. Because the structure cathode of the device is relatively complex, a two-step diffusion method is proposed. The process flow of field charge extraction diode is designed and the whole process scheme is simulated by numerical simulation technology. The various characteristic parameters of the device are verified after the fabrication of the process. The results show that the various characteristic parameters of the device are in line with the expected design, which indicates that the process scheme is feasible. Finally, the research results of this paper have certain reference value and practical significance for the development and design of high voltage fast soft turn off diode.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN313.4

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