The impact of linear correlation between lognormal distribution grain size mean and sigma along the polysilicon channel on threshold voltage (Vth) variability has been investigated in three dimensional (3D) NAND flash. The variety of grain size mean and sigma results in the unstable Vth variability. To obtain a stable Vth distribution with various grain size mean, the grain size mean dependent Vth variability sensitivity to the grain size sigma was used to optimize the linear correlation between grain size mean and sigma via TCAD simulation. The optimized linear correlation with stable Vth variability is obtained except for the “unbalance region” affected by the combination of grain boundaries and positions with these grain size mean and sigma values resulting in the slightly shrinking Vth variability. Our results strongly suggest that this approach could guide the direction of polysilicon crystallization optimization to obtain stable Vth distribution with the predicted linear correlation between grain size mean and sigma.

中文翻译：

---

通过多晶硅晶粒尺寸仿真分析和优化 3D NAND 闪存中的阈值电压可变性

已在三维 (3D) NAND 闪存中研究了沿多晶硅通道的对数正态分布晶粒尺寸平均值和西格玛之间的线性相关性对阈值电压 (Vth) 变异性的影响。晶粒尺寸平均值和西格玛的变化导致不稳定的 Vth 变异性。为了获得具有各种晶粒尺寸平均值的稳定 Vth 分布，通过 TCAD 模拟，使用晶粒尺寸平均值依赖 Vth 变异性对晶粒尺寸 sigma 的敏感性来优化晶粒尺寸平均值和 sigma 之间的线性相关性。除了受晶界和位置组合影响的“不平衡区域”外，获得了与稳定 Vth 变异性的优化线性相关性，这些晶粒尺寸平均值和 sigma 值导致 Vth 变异性略微缩小。