Abstract Heterogeneous SiNx based charge trap flash (CTF) which has varying N/Si ratio ( x ) along the thickness of the charge-trapping layer (CTL) shows improved program/erase (P/E) transients. In this work, we present the P/E model invoking different nature of traps in N-rich and Si-rich CTL and investigate the physical processes behind the P/E improvement observed in heterogeneous CTF. A set of coupled equations that include Poisson's and rate equations for electrons and holes are solved considering the variation of CTL physical parameters along the thickness. The electron/hole injection current is accurately computed by including quantum effects at Si/SiO2 interface and taking into account the field-dependent relaxation of the energetic injected carriers. The simulation results of our model are in close agreement with the experimentally observed characteristics for five different sets of CTF devices with standard, Si-rich and N-rich homogeneous, and discretely and linearly graded heterogeneous CTF. Our study points out that the improvement in program transient for the heterogeneous CTF devices is attributed to the variation of trap density and trap energy along the CTL thickness and not due to lateral tunneling between the traps. The improvement in erase saturation and speed is due to high electron emission from the traps in Si-rich layer near bottom oxide of heterogeneous CTL.

中文翻译：

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异构 SiNx 电荷陷阱闪存中的编程/擦除瞬态建模

摘要 基于异质 SiNx 的电荷陷阱闪存 (CTF) 具有沿电荷俘获层 (CTL) 厚度变化的 N/Si 比 (x)，显示出改进的编程/擦除 (P/E) 瞬态。在这项工作中，我们提出了 P/E 模型，该模型调用了富 N 和富硅 CTL 中不同性质的陷阱，并研究了在异质 CTF 中观察到的 P/E 改进背后的物理过程。考虑到 CTL 物理参数随厚度的变化，求解了一组耦合方程，其中包括电子和空穴的泊松方程和速率方程。通过在 Si/SiO2 界面包含量子效应并考虑高能注入载流子的场相关弛豫，可以准确计算电子/空穴注入电流。我们模型的模拟结果与五组不同的 CTF 装置的实验观察特性非常一致，这些 CTF 装置具有标准、富硅和富氮同质、离散和线性渐变的异质 CTF。我们的研究指出，异质 CTF 器件程序瞬态的改进归因于陷阱密度和陷阱能量沿 CTL 厚度的变化，而不是由于陷阱之间的横向隧道效应。擦除饱和度和速度的提高是由于来自异质 CTL 底部氧化物附近的富硅层中的陷阱的高电子发射。我们的研究指出，异质 CTF 器件程序瞬态的改进归因于陷阱密度和陷阱能量沿 CTL 厚度的变化，而不是由于陷阱之间的横向隧道效应。擦除饱和度和速度的提高是由于来自异质 CTL 底部氧化物附近的富硅层中的陷阱的高电子发射。我们的研究指出，异质 CTF 器件程序瞬态的改进归因于陷阱密度和陷阱能量沿 CTL 厚度的变化，而不是由于陷阱之间的横向隧道效应。擦除饱和度和速度的提高是由于来自异质 CTL 底部氧化物附近的富硅层中的陷阱的高电子发射。