Development of Tera-bit class high speed nonvolatile magentic memories

实验和数值模拟研究了一种新的器件概念的共享功能已被执行，以实现一个磁非易失性存储器的太比特密度和高访问速度。在该单元结构中，用于比特信息载体的数据存储层和用于数据写入的开关层通过磁耦合垂直集成。1）通过数值模拟比较了偶极耦合和层间交换耦合两种不同的功能集成机制，发现交换耦合在细胞中具有优良的从开关到存储层的上级转矩传递。2）交叉点（CP）通过自对准工艺制造具有200 nm的最小图案尺寸的存储器单元，其中磁性多层带被构造成具有用作干蚀刻掩模的覆盖导体图案。通过对所制备的CP电池的磁阻测量，证实了良好的偶极耦合，这导致了CP电池的电阻率的急剧降低。 关于我们 3）对由软磁层CoFe和硬磁层TbFe组成的交换耦合双层电池进行了热辅助磁化反转。电流引起的局部焦耳加热降低了TbFe层的磁各向异性，从而导致双层的磁化反转场显著降低。采用新开发的程序对高温下的磁化过程进行了数值分析，并引入了宏观模型。阐明了交换耦合双层膜中热助磁化反转的详细机理。优化了磁性能、层结构和层间交换耦合刚度，实现了优异的上级功能共享性能。实际的数据稳定性和低功耗存储器操作已被证实为优化的垂直磁化的细胞与10 nm的横向尺寸的顺序。少

Experimental and numerical studies on a novel device concept of sharing function have been performed to realize a magnetic nonvolatile memory with terabit density and high access speed. In the proposed cell structure, data storage layer for bit information carrier and switching layer for data writing are vertically integrated through magnetic coupling.1)Two different functional integrating mechanism of dipole coupling and inter-layer exchange coupling have been compared by numerical simulation, and it was found that the exchange coupling exhibits superior torque transmitting from switching to storage layer in the fine cell.2)A cross-point (CP) memory cell with the minimum pattern size of 200 nm was fabricated by a self-aligned process, where a magnetic mulilayer strip was structured with an over-laid conductor pattern used as a mask for dry-etching. Well defined dipole coupling was confirmed from magnetoresistive measurements for the fabricated CP cell, which leads to the drastic reduc … More tion of the magnetization reversal field.3)Thermally assisted magnetization reversal was performed for an exchange coupled bi-layer cell, consisted of soft magnetic CoFe and hard magnetic TbFe layer. The current induced local Joule heating decreases the magnetic anisotropy in the TbFe layer, which results in the marked decrease of the magnetization reversal field of the bi-layer. A high speed operation was also confirmed with the pulsed laser heating.4)Numerical analysis for the magnetization process at high temperature was carried out with the newly developed program introducing a macro scale model. Detailed mechanism of thermally assisted magnetization reversal in the exchange coupled bi-layer has been clarified. Magnetic properties, the layer structure and the inter-layer exchange coupling stiffness have been optimized to realize the superior functional sharing performance. Practical data stability and low power memory operation have been confirmed for the optimized perpendicularly magnetized cell with an order of 10 nm lateral dimension. Less