MTJ MRAM的特性分析与设计

对 MTJ(磁隧道结 )的 GMR(巨磁阻 )效应进行了分析。 MTJ的结构、形态和工作条件会对 GMR效应产生不同的影响。提出了一种 4× 1位 MTJMRAM(磁存储器 )的电路结构 ,每个 MRAM的存储单元由一个MTJ和一个 MOSFET构成 ,用 MTJ两磁极磁化方向的相对取向表示所存储的数据 ,数字线和位线电流产生磁场的共同作用可完成 MRAM数据的写入。     

Ar/CO/NH3等离子体刻蚀多种磁性金属叠层

基于磁性合金的等离子体刻蚀工艺,在中国科学院微电子研究所自主研发的刻蚀设备中,使用Ar,CO和NH3的混合气体对用于形成磁随机存储器(MRAM)的多种磁性金属叠层进行刻蚀.采用两步刻蚀的方法刻蚀了多层磁性金属叠层,每一步的刻蚀气体组分不同,研究了Ar气在混合气体中的体积分数对材料刻蚀速率和侧壁形貌的影响.结果表明,刻蚀速率随着Ar气体积分数的增加而增加,而侧壁倾角则随着Ar气体积分数的增加而减小.两步刻蚀的方法可以根据材料的结构特点来控制Ar离子轰击的作用,可以得到大于21.4 nm/min的刻蚀速率和约90°的侧壁倾角.     

最新MM存储能力提升到16Mb

磁性随机存储器(MRAM)和集成磁(Integrated Magnetic)产品供应商Everspin科技公司,近日推出了高容量16Mb MRAM产品.     

A novel magnetic random access memory design using square ring elements for the hard layer

The behavior of narrow permalloy square rings under the influence of a magnetic field was studied using magnetic force microscopy (MFM). Two stable states of opposite polarity at remanence and simple switching were observed. We propose a design for the hard layer of magnetic random access memory (MRAM) that uses these states in square rings for data storage.     

一种新型存储器件——磁电存储器

磁电存储器不仅存取速度快、功耗小，而且集动态RAM、磁盘存储和高速缓冲存储器功能于一身，因而已成为动态存储器研究领域的一个热点。文章总结了磁电存储器的工作原理和特性，分析了它们的发展现状及存在的问题，并对其应用前景进行了展望。     

Etch characteristics of CoFeB magnetic thin films using high density plasma of a H2O/CH4/Ar gas mixture

Etch characteristics of CoFeB magnetic thin films patterned with TiN hard masks were investigated using inductively coupled plasma reactive ion etching in H₂O/Ar and H₂O/CH₄ gas mixes. As the H₂O concentration in the H₂O/Ar gas increased, the etch rates of CoFeB and TiN films decreased simultaneously, while the etch selectivity increased and etch profiles improved slightly without any redeposition. The addition of CH₄ to the H₂O gas resulted in an increase in etch selectivity and a higher degree of anisotropy in the etch profile. X-ray photoelectron spectroscopy was performed to understand the etch mechanism in H₂O/CH₄ plasma. A good pattern transfer of CoFeB films masked with TiN films was successfully achieved using the H₂O/CH₄ gas mix.     

Reversal modes and reversal times in submicron sized elements for MRAM applications

The switching behavior of submicron sized NiFe nanoelements was calculated using a hybrid finite element/boundary element method. The numerical integration of the Gilbert equation of motion reveals the transient states during magnetization reversal under the influence of a constant applied field. The reversal mode and the reversal time sensitively depend on the size and the shape of the elements. The 200 × 100 × 10 nm³ elements switch well below 1 ns for an applied field of 80 kA/m and a Gilbert damping constant =0.1. The elements reverse by non-uniform rotation. If an external field is applied the magnetization starts to rotate near the ends, followed by the reversal of the center. This process requires only about 0.1 ns. In what follows, the magnetization component parallel to the field direction shows oscillations, which decay within a time of 0.4 ns. The excitation of spin waves is caused by the precession of the magnetization around the local effective field. A rapid decay of the oscillations is obtained in elements with slanted ends, where surface charges cause a transverse demagnetizing field.     

TMR at 4.2 K for Amorphous Magnetic-Tunnel-Junctions with Co60Fe20B20 as Free and Pinned Layers

Single barrier magnetic-tunnel-junctions (MTJs) with the layer structure of Ta(5)/Cu(30)/Ta(5)/Ni79Fe21(5)/Ir22Mn78(12)/Co60Fe20B20(4)/Al(0.8)-oxide/Co60Fe20B20(4)/Cu(30)/Ta(5) [thickness unit: nm] using the amorphous Co60Fe20B20 alloy as free and pinned layers were micro-fabricated. The experimental investigations showed that the tunnel magnetoresistance (TMR) ratio and the resistance decrease with increasing dc bias voltage from 0 to 500~mV or with increasing temperature from 4.2 K to RT. A high TMR ratio of 86.2% at 4.2 K, which corresponds to the high spin polarization of Co60Fe20B20 55%, was observed in the MTJs after annealing at 270℃ for 1 h. High TMR ratio of 53.1%, low junction resistance-area product RS of 3.56 kΩμm2, small coercivity Hc of ≤4 Oe, and relatively large bias-voltage-at-half-maximum TMR with the value V1/2 of greater than 570 mV at RT have been achieved in such Co-Fe-B MTJs.     

磁电阻材料及其应用的研究进展

本文综述了磁电阻 (MR)材料的研究进展 ,并对目前研究热点的四类巨磁电阻 (GMR)材料进行了概括评述 ,侧重论述MR材料在信息存储等领域的应用 ,明确指出开发和应用MR材料的关键问题是提高各类GMR材料的室温MR值和降低其工作磁场