Three-Dimensional Magnetic Memory Device

本提案的目标是探索三维磁记录，以生产未来的高性能存储设备。对数据的需求不断增加，这种需求将继续呈指数级增长。然而，今年研究人员首次发现，当面密度超过大约100 Gbit/in2时，传统纵向磁性介质中记录的数据变得非常不稳定。这些已知的替代技术大多是二维性质的，并承诺将超顺磁极限推迟到1太比特/in2以上。然而，为了将超顺磁极限大大推迟到1太比特/in2以上，有必要在第三（垂直）维度上堆叠记录层。垂直堆叠是三维磁记忆概念的基础，也是本方案的主要主题。提出了几种三维存储器件的实现方法。我们将从理论和实验两方面比较研究这两种实现方式背后的物理原理。通过这些实验，提出了使用聚焦离子束（FIB）来制作亚100纳米尺寸的测试结构。重点将放在三个组成部分的研究上：1)媒介，2)写和3)读过程。其中一种访问数据的机制利用了早期开发的（用于垂直记录）方法，该方法使用3d记录介质下的“软”磁底层（SUL）来控制强磁场。在写入过程中，使用SUL可以大大增加整个3d介质厚度的记录场。在回读过程中，SUL的“柔软性”强烈影响灵敏度场（对于互易原理），因此将用作识别单场平面（2-D层）的机制。为了减少符号间的干扰并提高稳定性，提出了在所有三个维度上对记录介质进行图形化。三维磁记录的物理特性也将通过landau - lifshits - gilbert微磁建模和蒙特卡罗温度模拟进行理论研究。磁力显微镜（MFM）和光学克尔显微镜将用于研究记录介质中的晶间相互作用。最后，为了学习如何有效地从大量三维介质中分析和读取信息，建议利用“约束反卷积”等信号处理技术。本研究所需的基本的基于Co/ pt的三维介质薄膜将使用共溅射沉积在室内制造。通过光学光刻和随后的FIB修整，纳米级的位单元将被测试。为了进行3-D磁记录的对比研究，希捷科技承诺提供额外的记录换能器（用于FIU的进一步FIB修剪）和各种形式的记录介质（通过基于电子束的光刻图纹），并帮助提供额外的表征方法。此外，为了支持这项工作，希捷还提出捐赠巴尔查斯公司的13室溅射系统。这个项目的最终目标是制定设计一个适当的3-D介质的指导方针，并理解写和读过程的物理原理。本项目属跨学科性质。它的成功取决于数据存储的工程经验与对磁记录设备基本物理的理解和先进数据识别方法的知识的充分整合。该联合项目位于最大的少数族裔研究机构之一，也是最年轻的研究机构之一（FIU），具有强大的工业联系，有望推动FIU的研究计划，并大力促进代表性不足的群体参与高级研究。在这些研究工作中，私人学院已经建立了邀请顶尖研究人员在国际金融大学举办座谈会的传统。由于目前的共同努力，国际金融大学对纳米级信息系统的研究兴趣显著增加。仅在一年的时间里，参与纳米级磁性器件研究的学生（主要是少数民族）就从1人增加到12人。至于技术影响，由于该项目的性质，它将有助于推动数十亿美元的数据存储行业的发展。从短期来看，类似于现在流行的闪存，3d磁存储器可以作为usb兼容设备使用，具有更高的数据容量。从长远来看，3d磁存储器可能会取代传统的磁性硬盘驱动器和其他存储技术，在适当的情况下甚至可能转变为单芯片计算。最后，3-D存储器很好地符合垂直集成的预期总体趋势。

Intellectual Merit The objective of this proposal is to explore 3-D magnetic recording in order to produce future high-performance memory devices. There is increasing demand for data and this demand will continue to exponentially grow. However, this year for the first time, researchers witnessed that the recorded data in conventional longitudinal magnetic media becomes highly unstable as the areal density increases beyond approximately 100 Gbit/in2. Most of these known alternative technologies are of 2-D nature and promise to defer the superparamagnetic limit beyond one terabit/in2. However, to defer the superparamagnetic limit substantially beyond the one terabit/in2 mark, it will be necessary to stack recording layers in the third (vertical) dimension. The vertical stacking underlies the concept of 3-D magnetic memory - the primary subject of this proposal. Several implementations of a 3-D memory device are proposed. The physics underlying the alternative implementations will be comparatively studied from both theoretical and experimental perspectives. Through these experiments, it is proposed to use focused ion beam (FIB) to fabricate test structures with sub-100-nm dimensions. The focus will be on the study of three components: 1) medium, 2) write and 3) read processes. One of the proposed mechanisms to access data takes advantage of an earlier developed (for perpendicular recording) method to control strong magnetic fields using a "soft" magnetic underlayer (SUL) under the 3-D recording medium. During the write process, the use of the SUL allows to considerably increase the recording field across the entire thickness of the 3-D medium. During the readback process, the "softness" of the SUL strongly influences the sensitivity field (for the Reciprocity Principle) and thus will be used as a mechanism to identify a uni-field plane (2-D layer). To minimize the inter-symbol interference and improve stability, it is proposed to pattern the recording medium in all three dimensions. The physics of 3-D magnetic recording will be also investigated theoretically with Landau-Lifshits-Gilbert-based micromagnetic modeling and Monte-Carlo-based temperature simulations. Magnetic force microscopy (MFM) and optical Kerr Microscopy will be used to study the intergranular interactions in the recording medium. Finally, to learn how to efficiently analyze and read back information from the bulk of the 3-D medium, it is proposed to take advantage of a signal processing technique such as "constrained deconvolution". Basic Co/Pt-based 3-D medium thin-films necessary for this study will be fabricated inhouse using co-sputter deposition. With optical lithography and following FIB trimming, nanoscale bit cells will be tested. To conduct a comparative study of 3-D magnetic recording, Seagate Technology commits to provide additional recording transducers (for further FIB trimming at FIU) and various forms of recording media (patterned via E-beam-based lithography), and help with additional characterization methods. In addition, to support this work, Seagate has offered to donate a 13-chamber sputtering system by Balzers Corporation. The ultimate goal of this project is to develop guidelines to design an adequate 3-D medium and understand the physics of write and read processes.Broader Impacts This project is interdisciplinary in nature. Its success depends on the adequate integration of the engineering experience in data storage with the understanding of the basic physics of magnetic recording devices and knowledge of advanced data recognition methods. Based at one of the largest minority-serving and one of the youngest research institutions (FIU), this joint project with strong industrial ties promises to boost the research initiatives at FIU and strongly promote the involvement of underrepresented groups in advanced research. Throughout these research efforts, PIs have established a tradition of inviting leading researchers to offer colloquia at FIU. The interest in research on Nanoscale information systems at FIU has significantly grown due current joint efforts. In one year alone, the number of students (mostly minority) involved in the study of nanoscale magnetic devices has grown from one to twelve. As for the technological impact, due to the nature of this project, it will contribute to the advancement of the multi-billion-dollar data storage industry. From a short-term perspective, similar to popular flash memory today, 3-D magnetic memory could be used as a USB-compatible device with significantly higher data capacity. In the long-term perspective, 3-D magnetic memory may replace conventional magnetic hard-drives and other memory technologies, and under the right circumstances may even transform into single-chip computing. Finally, 3-D memory goes well along the expected general future trend of vertical integration.