基于金刚石钝化散热的GaN HEMT功率器件研究

Due to continued innovation in material epitaxial technology, device fabrication process and device structure design, GaN devices, especially high electron mobility transistor (HEMT), have made an extraordinary progress in terms of both large power and high integration applications. However, they are affected by self-heating and thermal transport in the near-junction region, and those lead to the rise of junction temperature which reduces performance and reliability of power devices. Thus, the high power advantage is not to play full, and the thermal management of chip level has been a critical limitation for practical applications of GaN HEMT. In views of the above question, the heat dissipation technology which diamond films with high thermal conductivities are applied to the passivation layer of GaN HEMT is intended in this project. The dependency relations between heat spreading capability and diamond films structure are thoroughly analyzed, and the heating mechanism of diamond films for passivation layer has been revealed. Meanwhile, the influence rule on electrical performances of device for passivation layer using diamond films is explored, and the key technologies of passivation layer are evolved. Finally the success of this GaN HEMT with diamond passivation layer can be an important for the development of thermal management in chip level of power devices.

得益于材料外延、器件工艺以及器件结构的不断创新，氮化镓（GaN）基电子器件，尤其是HEMT器件，近几年在大功率、高集成度应用方面都取得了巨大进步。然而，高功率密度的发展受限于其自生热和近结区散热能力引起器件结温升高问题，严重导致器件性能和可靠性的下降，使GaN器件的高功率性能优势远未发挥，芯片级散热问题是目前GaN基功率器件发展面临的最大挑战。针对上述问题，本项目拟提出基于GaN HEMT器件的高导热金刚石薄膜作钝化层的芯片级散热结构，深入研究各结构参数与器件散热能力的关系，揭示高导热薄膜钝化结构独特的散热机制，探索金刚石薄膜作钝化层的对器件电性能影响的规律，并突破其关键兼容工艺。成功研制出具备高散热能力的金刚石钝化的HEMT器件，为GaN器件芯片级热管理的发展奠定一定基础。

以氮化镓为代表的第三代半导体满足新一代电子产品对更大功率、更高频率、更小体积微波功率器件的要求，被广泛应用于雷达系统、通信系统、电子对抗系统和侦察探测系统等军民领域。然而高功能集成化的发展发展受限于其自生热和近结区散热能力引起器件结温升高问题，严重导致器件性能和可靠性的下降，使GaN器件的高功率性能优势远未发挥，芯片级散热问题是目前GaN基功率器件发展面临的最大挑战。针对上述问题，本项目开展了高热导率金刚石薄膜作钝化层的散热技术研究。完成了金刚石钝化GaN芯片散热机理和结构设计、金刚石钝化与传统的GaN器件兼容工艺、金刚石钝化层对器件电性能的影响及金刚石钝化GaN HEMT散热能力的评估等研究内容，突破了金刚石钝化散热结构设计、低温金刚石钝化生长控制、及高精度微纳尺度金刚石刻蚀等关键技术。建立了完备的基于GaN器件的金刚石钝化散热技术的工艺、结构与理论体系，研制出高散热性能GaN器件，金刚石钝化GaN HEMT器件热阻同比SiN钝化器件下降21.4%，器件输出特性提升27.9%，小信号增益提升36.7%，充分体现了金刚石钝化散热技术的潜能和优势，为GaN器件芯片级热管理的发展奠定一定基础。