论文标题
超薄垂直层，用于降低STT-MRAM中的开关电流
Ultrathin perpendicular free layers for lowering the switching current in STT-MRAM
论文作者
论文摘要
在自旋转移扭矩磁随机访问记忆（STT-MRAM）中，切换自由层（FL）磁化所需的临界电流密度$ J_ {C0} $与抑制参数，饱和度磁化强度和自由层的厚度，$αm_st_f $成比例。常规FLS具有COFEB/非磁性垫片/COFEB结构。通过减小垫片厚度，W在我们的情况下W，并将单W层分成两层的子单层厚度，我们减少了$ t_f $，同时最小化$α$并最大化$ M_S $，最终导致较低的$ J_ {C0} $，同时维持高热稳定性。制造了底部的底部小细胞，具有装置直径在55-130 nm的范围内，$ J_ {C0} $对于最薄（1.2 nm）FLS的最低，低于65 nm设备的4 mA/cm $^2 $，$ \ sim $ \ sim $ 30％比1.7 nm fls低30％。最小设备尺寸的热稳定性因子$δ_{\ MathRM {dw}} $高达150，是使用域壁反转模型从现场开关概率测量中确定的。使用高$δ_ {\ mathrm {dw}} $和最低$ j_ {c0} $，最薄的FLS具有最高的自旋转移扭矩效率。
The critical current density $J_{c0}$ required for switching the magnetization of the free layer (FL) in a spin-transfer torque magnetic random access memory (STT-MRAM) cell is proportional to the product of the damping parameter, saturation magnetization and thickness of the free layer, $αM_S t_F$. Conventional FLs have the structure CoFeB/nonmagnetic spacer/CoFeB. By reducing the spacer thickness, W in our case, and also splitting the single W layer into two layers of sub-monolayer thickness, we have reduced $t_F$ while minimizing $α$ and maximizing $M_S$, ultimately leading to lower $J_{c0}$ while maintaining high thermal stability. Bottom-pinned MRAM cells with device diameter in the range of 55-130 nm were fabricated, and $J_{c0}$ is lowest for the thinnest (1.2 nm) FLs, down to 4 MA/cm$^2$ for 65 nm devices, $\sim$30% lower than 1.7 nm FLs. The thermal stability factor $Δ_{\mathrm{dw}}$, as high as 150 for the smallest device size, was determined using a domain wall reversal model from field switching probability measurements. With high $Δ_{\mathrm{dw}}$ and lowest $J_{c0}$, the thinnest FLs have the highest spin-transfer torque efficiency.
