硅基GaN HEMTs超级结器件及其模型研究

This project is focused on the fabricaton of super-junction GaN power transistor and the model of devices' charge sharing, which is combined with the process of silicon power devices and circuit. Using the methods of numerical algorithm self consistent solution,a AlGaN/GaN HEMT material structure based on silicon substrate with excellent positive electrical properties has been designed. The epilayer of device structure is grown by MOCVD. The super-junction is formed at a region between gate and drain using the technique of self aligned fluoride ion treatment, which is based on the transverse super-junction struture of silicon substrate/GaN epilayer. The charges are shared between the resurf of Si/GaN epilayer and super-junction of drift region, which will modulate the surface electric field into the bulk of epilayer. This technique will eliminate the surface electric field nearby Schottlay gate and finally take place the breakdown in the bulk of epilayer, which will improve the breakdown voltage. The model of charge sharing in the drift region will be built by optimizing the struture of voltage sustain layer. Also, the dynamics lattice model of fluoride ion bond is built to verificate the stability of super junction P-column. The damage machanism which is introduced by fluoride ion implant into epilayer and recovery technique will be further investigated.

本申请提出一种宽禁带GaN半导体材料结构与主流硅基功率器件制作工艺相结合的GaN基超级结功率新结构器件并建立电荷共享模型。采用数值算法自洽求解设计具有良好正向电学特性的硅基AlGaN/GaN HEMT外延材料结构，采用MOCVD设备外延生长。该新器件结构采用自对准氟离子处理技术，在肖特基栅极和漏极之间形成复合耐压新结构- - -基于硅基/GaN外延层的横向超级结结构（Super-Jucntion）。通过硅基/GaN外延层的Resurf结构和漂移区Super-Junction结构实现电荷共享，将表面电场峰值调制至体内，消除肖特基栅附近的表面电场，最终实现体内击穿，进而提高器件的击穿电压；通过优化器件漂移区的耐压结构设计，建立其漂移区电荷共享模型。研究氟离子键的动力学晶格模型验证氟负离子作为超级结P型柱的稳定性，以及研究氟离子注入GaN外延层引入的损伤机理和修复技术。

本项目对GaN基HEMT超级结器件和器件模型的建立开展了相关的研究，分别研究了GaN基HEMT器件外延材料结构的设计、外延生长、器件关键工艺技术、氟离子处理技术、器件模型建立等。采用MOCVD设备外延生长了高质量的GaN HEMT器件材料，常温2DEG迁移率大于1500cm2/V.s，方块电阻270ohm/squ.。采用自对准氟离子处理技术，在肖特基栅极和漏极之间形成复合耐压新结构---基于硅基/GaN外延层的横向超级结结构（Super-Jucntion）的新技术，实现了栅长1.0um的GaN基HEMT超级结器件，在漂移区长度为15um时，击穿电压接近硅基GaN高压器件的理想击穿电压，约为657V，相比sapphire衬底HEMT器件结构的击穿电压提高了约182V。开发出栅长小于100-nm的肖特基金属栅工艺；优化低欧姆接触工艺，欧姆接触电阻低至0.08ohm.mm。研究结合硅基F-离子的负电荷特性，完成了硅基GaN超级结器件复合耐压模型的研究。研究了器件在宽温度变化下（25℃-250℃），器件的直流参数、击穿和功率特性以及高频参数等测试结果，提取了器件测试结果中的寄生电容Cgs和Cgd、寄生电阻RDS等参数，研究了器件耐压性能与氟离子分布之间的关系，建立漂移区电荷共享模型。