Scalable Three Terminal Memory Devices based on Silicon-Compatible Antiferromagnetic Materials

反铁磁性材料是没有净宏观磁化强度的磁性有序材料。它们提供的特性使其有望成为高密度、快速和低功耗的非易失性存储器件：首先，相邻比特之间没有位间偶极相互作用，使得可以将相邻比特放置在比铁磁器件更近的位置。其次，由于其交换主导的动力学，反铁磁体可能具有在皮秒范围内的超快写入时间。第三，基于这些材料的设备将不会受到磁场的篡改，使它们比基于铁磁的设备更安全。然而，到目前为止，这些器件的实现一直受到与反铁磁材料，特别是与工业相关的材料和纳米尺度的反铁磁材料电相互作用的困难的阻碍。该项目旨在开发具有全电读写能力的三端子反铁磁存储器件，该器件基于可集成到现有半导体制造工艺中的硅兼容反铁磁材料。该项目将使磁性存储器能够满足比目前可能的更广泛的市场，包括动态随机存取存储器和嵌入式静态随机存取存储器，从而产生重大的经济影响。除了其经济影响外，该项目还将通过纳入重要的外联和教育活动而产生更广泛的影响。这包括通过西北大学艺术工程跨学科外联项目，通过表演艺术(以科学为主题的戏剧和电影放映)向更广泛的公众进行宣传。研究成果还将被整合到西北大学PI正在教授的一门新课程中，该课程侧重于磁学和自旋电子学的基础和应用。这项建议的智力优势在于三端非易失性存储器件的器件设计、建模、制造和电气特性。这些设备将主要基于非共线导电反铁磁材料，这些材料可以溅射沉积在硅衬底上(例如SnMn3、GaMn3、IrMn3和相关化合物)。磁性状态将通过电流感应的来自邻近重金属的自旋轨道扭矩来电控制。该项目旨在演示该设备操作的规模缩小到与行业相关的钻头直径。该项目还将通过隧道磁阻结构将电子写入机制与电子读出集成在一起，将Néel矢量修改转换为电阻变化。读和写路径的分离允许更高的循环耐久性以及读和写步骤的材料参数的单独优化。本课程将研究热预算、器件变异性引起的统计差异以及制造工艺对器件特性的其他影响。所开发的存储器件将被充分表征，以在写入时间、写入能量、写入错误率(即，切换概率)、读取干扰率和循环耐久性方面将它们的性能与现有的基于铁磁的存储器件进行比较。将描述器件级别的折衷(例如，在速度和耐久性之间)，并将其与其他现有的和新兴的存储器技术进行比较。建模将在微磁水平上进行，以帮助器件设计，并在基于物理的紧凑模型水平上进行，以便在电路设计环境中实施。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Antiferromagnetic materials are magnetically ordered materials without a net macroscopic magnetization. They offer characteristics that make them promising for high-density, fast, and low-power nonvolatile memory devices: Firstly, there is no inter-bit dipole interaction between neighboring bits, making it possible to place adjacent bits closer together than with ferromagnetic devices. Secondly, antiferromagnets can potentially have ultrafast write times in the picosecond range, due to their exchange-dominated dynamics. Thirdly, devices based on these materials would be immune to tampering by magnetic fields, making them more secure than ferromagnet-based devices. However, to date, the realization of these devices has been hindered by the difficulty of electrically interacting with antiferromagnetic materials, particularly in industry-relevant materials and at nanoscale dimensions. This project aims to develop three-terminal antiferromagnetic memory devices with full electrical read and write capability, based on silicon-compatible antiferromagnetic materials that can be integrated in existing semiconductor manufacturing processes. This project will have a significant economic impact by enabling magnetic memories to address broader markets than currently possible, including dynamic random-access memory and embedded static random-access memory. In addition to its economic impact, this project will achieve broader impact through the incorporation of significant outreach and education activities. This includes outreach to the broader public through performance arts (science-themed plays and film screenings) through the Engineering Transdisciplinary Outreach Project in the Arts at Northwestern University. Research results will also be integrated into a newly developed course that the PI is teaching at Northwestern University, which focuses on the fundamentals and applications of magnetism and spintronics.The intellectual merit of this proposal is in the device design, modeling, fabrication, and electrical characterization of three-terminal nonvolatile memory devices. The devices will be primarily based on noncollinear conductive antiferromagnetic materials that can be sputter-deposited on silicon substrates (e.g., SnMn3, GaMn3, IrMn3 and related compounds). The magnetic state will be controlled electrically via current-induced spin-orbit torque from an adjacent heavy metal. The project aims to demonstrate scaling of this device operation down to industry-relevant bit diameters. The project will also integrate the electrical write mechanism with electrical readout via a tunneling magnetoresistance structure, translating the Néel vector modification into an electrical resistance change. The separation of read and write paths allows for higher cycling endurance and separate optimization of material parameters for the read and write steps. Thermal budgets, statistical variations induced by device variability, and other effects of the fabrication process on device characteristics will be investigated. The developed memory devices will be fully characterized to compare their performance to existing ferromagnet-based memory devices in terms of write time, write energy, write error rates (i.e., switching probability), read disturb rates, and cycling endurance. The device-level tradeoffs (e.g., between speed and endurance) will be characterized and compared to other existing and emerging memory technologies. Modeling will be performed both at the micromagnetic level to aid in device design, and at the physics-based compact model level, to allow for implementation into circuit design environments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.