基于晶态high-k层对非铁电相的抑制机理改善HfO2基FeFET的耐久性

Complementary-metal-oxide-semiconductor (CMOS) compatible HfO2 based ferroelectric field-effect transistor (FeFET) has a great potential application in information storage devices for both civilian and military uses. However, the endurance degradation in HfO2 based FeFETs has become the technical bottleneck for the application of this technology. The use of crystalline high-k insulator layer is expected to suppress the formation of nonferroelectric phase and reduce the electric field in the insulator layer, thus improving the endurance of the HfO2 based FeFET. However, the mechanisms of suppressing the formation of nonferroelectric phase with crystalline high-k gate dielectrics, and the endurance degradation in the HfO2 based FeFET are still not clear. Based on these issues, this project will focus on the HfO2 based FeFET with crystalline high-k layer, and investigate the mechanism of suppressing the formation of nonferroelectric phase with crystalline high-k gate dielectrics, by studying the effects of heat treatment on the microstructures of the ferroelectric films. Furthermore, using domain evolution as a bridge, this project aims to establish a relationship among microstructures, domain evolution and endurance in the HfO2 based FeFETs, and therefore reveal the degradation mechanism of the FeFET, which could provide guidelines for optimizations on the HfO2 based FeFET with improved endurance.

与CMOS工艺兼容的HfO2基铁电场效应晶体管(FeFET)在民用和军用领域都具有广阔的应用前景。然而，耐久性退化是阻碍其应用的瓶颈。采用晶态high-k绝缘层有望抑制HfO2基薄膜中非铁电相的形成和降低FeFET中绝缘膜上的电场强度，从而提高HfO2基FeFET的耐久性。然而，如何在晶态high-k层上抑制非铁电相的生成以及HfO2基FeFET耐久性退化的微观机理还不清楚。基于此，本申请项目以采用晶态high-k绝缘层的HfO2基FeFET为研究对象，通过研究热处理对晶态high-k层上HfO2基薄膜微观结构的影响，揭示晶态high-k层对HfO2非铁电相的抑制机理。同时，通过对HfO2基FeFET中电畴结构及其演变进行研究，建立微观结构、电畴演变和耐久性之间的关联，阐明FeFET耐久性退化的微观机制，从而优化工艺制备出性能良好的HfO2基FeFET。

HfO2基铁电薄膜具有与先进CMOS工艺兼容、可微型化潜力大等优点，为我国实现大容量铁电存储器的自主可控提供了机会。然而，耐久性差是阻碍HfO2基FeFET应用的瓶颈。因此，研究FeFET的耐久性退化微观机理对于改善FeFET的具有重要意义。本项目研究了晶态high-k种子层上HfO2基FeFET的器件性能，研究发现：1)ZrO2种子层可以改善HfO2基薄膜的结晶质量和抑制HfO2基薄膜中单斜相的形成，从而提高HfO2基薄膜的铁电性能。采用ZrO2种子层的HfO2基FeFET也展示了优异的抗疲劳特性。其脉冲存储窗口、保持性能和疲劳性能的优化主要与HfO2基铁电薄膜层晶体质量的改善，以及与获得饱和极化态所需的电场减少和进而界面陷阱的产生受到抑制有关。2)通过分析疲劳测试过程中ID-VG曲线的演变规律可知，HfO2基FeFET疲劳性能的退化主要是电荷注入/俘获以及界面陷阱的产生引起的。与未含HfO2种子层器件相比，含HfO2种子层的HfO2基FeFET的阈值电压和存储窗口变化量较小、辐照后的初始存储窗口仍更大。1 Mrad(Si)总辐照后，仍展现了优异的保持性能。3)基于第一性原理的计算方法，研究了ZrO2种子层对HfO2薄膜的相稳定性和极化性能的影响和调控机理。结果分析表明，通过引入[111]取向ZrO2种子层可以在有效提升HfO2铁电相相稳定性的同时不会降低其极化强度，并且不会增加铁电相的翻转势垒。本项目为理解HfO2基FeFET耐久性退化的微观机制，改善HfO2基FeFET耐久性提供了理论依据和实验指导。