AC positive bias temperature instability (PBTI) of germanium nMOSFETs with GeO 2 /Ge and Si-cap/Ge gate stack was investigated in this brief. AC-DC-AC alternating PBTI stress tests were conducted on both types of devices, the experiment data shows the inserted DC stress phase has little impact on the following AC stress kinetics on GeO 2 /Ge nMOSFETs but introduce a significant “additional DC generation” on Si-cap/Ge devices. The “additional DC generation” is ascribed to the existence of energy alternating defects (EAD) according to previous studies. Energy distribution under DC and AC stress further demonstrate that EAD are significant on Si-cap/Ge but negligible on GeO 2 /Ge devices. Effective lifetime prediction is carried out and compared under DC stress after discharge (with a purposely introduced measurement delay) and AC stress on both GeO 2 /Ge and Si-cap nMOSFETs. The results show GeO 2 /Ge nMOSFETs' effective lifetime exhibits no difference under two stress modes, while Si-cap/Ge nMOSFETs' effective lifetime is underestimated using DC stress after discharge approximation without considering the EAD-induced “additional DC generation”. An extra 0.14V 10-year Vdd design margin can be obtained for Si-cap/Ge nMOSFETs to gain higher performance by taking “additional DC generation” into account. The conclusion is beneficial for process optimization and PBTI reliability improvement of Ge nMOSFETs.

中文翻译：

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GeO钪/Ge和Si-cap/Ge栅极堆叠锗nMOSFET交流正偏压温度不稳定性的比较研究


本简报研究了具有 GeO 2 /Ge 和 Si-cap/Ge 栅极堆叠的锗 nMOSFET 的交流正偏压温度不稳定性 (PBTI)。对两种类型的器件进行了 AC-DC-AC 交替 PBTI 应力测试，实验数据表明，插入的 DC 应力阶段对 GeO 2 /Ge nMOSFET 的后续 AC 应力动力学影响很小，但引入了显着的“额外 DC 生成”在 Si-cap/Ge 器件上。根据之前的研究，“额外的直流发电”归因于能量交替缺陷（EAD）的存在。直流和交流应力下的能量分布进一步表明，EAD 在 Si-cap/Ge 上很重要，但在 GeO 2 /Ge 器件上可以忽略不计。在放电后的直流应力（特意引入测量延迟）和交流应力下对 GeO 2 /Ge 和 Si-cap nMOSFET 进行有效的寿命预测并进行比较。结果表明，GeO 2 /Ge nMOSFET 的有效寿命在两种应力模式下没有表现出差异，而 Si-cap/Ge nMOSFET 的有效寿命在放电近似后使用直流应力而被低估，而不考虑 EAD 引起的“额外的直流生成”。通过考虑“额外的直流发电”，Si-cap/Ge nMOSFET 可以获得额外的 0.14V 10 年 Vdd 设计裕度，以获得更高的性能。该结论有利于Ge nMOSFET的工艺优化和PBTI可靠性的提高。