Department of Applied Physics, The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong, People's Republic of China.
ACS Nano. 2014 Dec 23;8(12):12601-11. doi: 10.1021/nn5054987. Epub 2014 Dec 1.
The interface between the metal and dielectric is an indispensable part in various electronic devices. The migration of metallic species into the dielectric can adversely affect the reliability of the insulating dielectric and can also form a functional solid-state electrolyte device. In this work, we insert graphene between Cu and SiO2 as a barrier layer and investigate the mass transport mechanism of Cu species through the graphene barrier using density functional theory calculations, second-ion mass spectroscopy (SIMS), capacitance-voltage measurement, and cyclic voltammetry. Our theoretical calculations suggest that the major migration path for Cu species to penetrate through the multiple-layered graphene is the overlapped defects larger than 0.25 nm2. The depth-profile SIMS characterizations indicate that the "critical" thickness of the graphene barrier for completely blocking the Cu migration is 5 times smaller than that of the conventional TaN barrier. Capacitance-voltage and cyclic voltammetry measurement reveal that the electrochemical reactions at the Cu/SiO2 interface become a rate-limiting factor during the bias-temperature stressing process with the use of a graphene barrier. These studies provide a distinct roadmap for designing controllable mass transport in solid-state electrolyte devices with the use of a graphene barrier.
金属和介质的界面是各种电子设备中不可或缺的一部分。金属物质向介质中的迁移会对绝缘介质的可靠性产生不利影响，并且还可以形成功能性的固态电解质器件。在这项工作中，我们在 Cu 和 SiO2 之间插入石墨烯作为阻挡层，并使用密度泛函理论计算、二次离子质谱 (SIMS)、电容-电压测量和循环伏安法研究 Cu 物质通过石墨烯阻挡层的质量传输机制。我们的理论计算表明，Cu 物质穿透多层石墨烯的主要迁移路径是大于 0.25nm2 的重叠缺陷。深度剖面 SIMS 特性表明，完全阻止 Cu 迁移的石墨烯阻挡层的“临界”厚度比传统的 TaN 阻挡层小 5 倍。电容-电压和循环伏安法测量表明，在使用石墨烯阻挡层的偏置温度应力过程中，Cu/SiO2 界面的电化学反应成为限制因素。这些研究为使用石墨烯阻挡层设计固态电解质器件中可控的质量传输提供了明确的路线图。
