Giant magnetoresistive random-access memories based on current-in-plane devices
Giant magnetoresistive random-access memories based on current-in-plane devices
复制标题
基于面内电流器件的巨磁阻随机存取存储器
作者：
R. Katti
巨磁阻随机存取存储器（GMRAM）是一种非易失性存储器，由标准半导体电子器件集成的磁性存储器件组成。在GMRAM中，磁性多层器件，例如“伪自旋阀”（PSV）和“自旋阀”（SV）器件，由纳米厚的材料层制成，用于存储信息并允许读取数据。PSV和SV器件是巨磁阻（GMR）面内电流（CIP）器件，其是诸如磁性隧道结器件的电流垂直于平面器件的替代存储器器件。在本文中，GMR CIP磁性器件的操作和特性进行了描述，支持演示的GMRAM，已通过非易失性和复杂的写入和读取存储器模式的测试，在写入和读取周期时间下降到约50纳秒。这里描述的GMRAM技术实现基于1 R 0 T架构，其中单个GMR PSV器件定义位单元并提供写入和读取选择性，因此每个位单元不需要晶体管。通过设置存储层中的磁化方向来存储PSV位。通过使用当电流在磁性器件中流动时这种磁性多层产生的GMR效应确定感测层相对于存储层的取向来读取PSV位。GMR效应是磁阻可变电阻自旋效应，其中电阻取决于磁性多层中的存储层与感测层之间的相对磁化。在表现出GMR效应的磁性多层中，当存储层和感测层之间的相对磁化反向平行时，电阻最大化;当存储层和感测层之间的相对磁化平行时，电阻最小化。GMR效应产生电阻变化，当用读取电流激发时，该电阻变化感应出区分二进制“1”和“0”的信号。CIP PSV器件的写入和读取特性描述在写开关，读开关，电阻，和磁阻特性的个别PSV器件和统计集成的PSV器件上制作的体硅和CMOS底层。基于实验工作和建模，已经推断磁化反转是旋转的，包括对应于切换的不可逆旋转、预期切换的可逆旋转以及在相反方向上完成从切换到饱和的反转的可逆旋转。磁阻和磁开关特性沿着非易失性、非破坏性读出和潜在的无限循环能力使得PSV和SV器件成为GMRAM的非易失性存储器元件的潜在选择。
A giant magnetoresistive random-access memory (GMRAM) is a nonvolatile memory consisting of magnetic memory devices integrated with standard semiconductor electronics. In GMRAMs, magnetic multilayer devices, such as "pseudo-spin-valve" (PSV) and "spin-valve" (SV) devices, are made of layers of nanometer-thick materials, and are used to store information and to allow the data to be read. PSV and SV devices are giant magnetoresistive (GMR) current-in-plane (CIP) devices that are alternative memory devices to current-perpendicular-to-plane devices such as magnetic tunnel junction devices. In this paper, GMR CIP magnetic device operation and characteristics are described that have supported the demonstration of GMRAMs that have passed nonvolatility and complex write and read memory pattern tests at write and read cycle times down to approximately 50 ns. The GMRAM technology implementation described here is based on a 1R0T architecture in which a single GMR PSV device defines the bit cell and provides write and read selectivity so no transistors are needed per bit cell. A PSV bit is stored by setting the direction of magnetization in the storage layer. A PSV bit is read by determining the orientation of the sense layer with respect to the storage layer using the GMR effect that such magnetic multilayers produce when current flows in the magnetic device. The GMR effect is a magnetoresistive variable-resistance spin effect in which the resistance depends on the relative magnetization between storage and sense layers in the magnetic multilayer. In a magnetic multilayer that exhibits the GMR effect, resistance is maximized when the relative magnetization between the storage and sense layers is antiparallel; resistance is minimized when the relative magnetization between the storage and sense layers is parallel. The GMR effect produces a change in resistance that, when excited with a read current, induces a signal that distinguishes between a binary "1" and "0". Write and read characteristics of CIP PSV devices are described in terms of write switching, read switching, resistive, and magnetoresistive properties of individual PSV devices and statistical ensembles of PSV devices fabricated on bulk Si and CMOS underlayers. Based on experimental work and modeling, magnetization reversal has been inferred to be rotational, including irreversible rotations that correspond to switching, reversible rotations that anticipate switching, and reversible rotations that complete reversal from switching to saturation in the opposite direction. Magnetoresistive and magnetic switching properties along with nonvolatility, nondestructive readout, and potentially unlimited cyclability make PSV and SV devices potential options as nonvolatile memory elements for GMRAMs.