基于沟槽型深漏端扩散区和场板技术的新型超结LDMOS的模型研究及研制

The integratable lateral power device is the key unit to realize miniwatt power system which requires high energy efficiency. Introducing the superjunction voltage-sustaining layer in the lateral MOS type power device (LDMOS: Lateral Double-diffusion MOSFET) is a hot research area in the power semiconductor and power integrated circuits on the bulk silicon. This project studies the physic mechanism about the low breakdown voltage in the bulk silicon superjunction LDMOS, starting from the curvature effect of the planar PN junction for the first time. It develops a new research direction for the bulk silicon lateral superjunction power device and belongs to the fundamental pioneering work. The novel superjunction LDMOS studied in this project employs a trench deep drain diffusion and the field plate technique to suppress the curvature effect of the drain diffusion, increase its the breakdown voltage, improve the trade-off relationship between the breakdown voltage and the specific on-resistance and enhance its ability to bear the charge imbalance condition. The breakdown voltage model and specific on-resistance model planned to be researched in this project offer significant guidance for optimizing the bulk silicon superjunction LDMOS. The new solution gives full play to the potential of the superjunction structure. Process technology used in this project is mature and the novel LDMOS has a good market application prospect.

可集成的横向功率器件是实现高能效小功率电源系统的关键单元，在横向MOS型功率器件（LDMOS：Lateral Double-diffusion MOSFET）中引入超结耐压层是目前体硅功率半导体和功率集成电路的研究热点。本项目首次从平面PN结的曲率效应出发，分析体硅超结LDMOS击穿电压低的物理机理，从而为体硅横向超结功率器件开辟一个新的研究方向，属于基础性开拓研究。项目研究的新型超结LDMOS结构采用沟槽型深漏端扩散区和场板技术，抑制漏端扩散区的曲率效应，提高器件的击穿电压，改善击穿电压和比导通电阻之间的折衷关系，增强器件抵抗电荷非平衡条件的能力。项目拟研究的击穿电压模型和比导通电阻模型对体硅超结LDMOS的优化设计具有重要的指导作用，新方案充分发挥超结结构的潜力，所用工艺技术成熟，市场应用前景广阔。

可集成的横向功率器件是实现高能效小功率电源系统的关键单元，超结横向MOS功率器件是目前体硅功率半导体和功率集成电路领域的研究热点，超结LDMOS器件面临的主要问题是击穿电压低。本项目从平面PN结的曲率效应出发，分析体硅超结LDMOS击穿电压受限的物理机理，建立了电场模型并优化设计击穿电压，建立了比导通电阻模型并分析比导通电阻与超结柱深宽比的关系，确定了超结LDMOS的加工工艺，优化了超结LDMOS的器件结构，并提出了一系列超结MOS器件新结构。. 研究发现，超结LDMOS的击穿电压除了受到由p型衬底引入的衬底辅助耗尽效应的影响外，还受到漏端n+扩散区曲率效应的影响。从建立的电场模型可以得出，增加漏端n+扩散区的结深、在超结柱中引入额外n型杂质和使用漏端场板可有效缓解曲率效应，提高器件的击穿电压；从建立的比导通电阻可以得出，随着超结柱深度的增加，比导通电阻的减小程度趋缓，最终饱和，减小超结柱的宽度比提高超结柱的深度更有效。. 本项目对超结LDMOS漏端扩散区曲率效应作用机理的研究成果为器件结构创新和优化设计提供了理论依据，比导通电阻与超结柱深度的关系给出了平面器件比导通电阻的理论极限。