Hydrodynamic Modeling of Impact Ionization Based on High- Energy Electron Subpopulation

冲击电离是限制当今先进半导体器件性能的最重要因素之一。冲击电离是热电子致器件退化的根源，是造成晶体管雪崩击穿的主要原因。碰撞电离的主要问题是碰撞电离系数（）的建模。通常，（）是电场或总电子居数平均能量的函数。不幸的是，这些模型不能恰当地描述非局部的碰撞电离。在这项研究中，我们提出了一种创新的方法来模型（作为一个独特的函数）的平均能量，只有那些高能超过冲击电离阈值的能量。这个平均宏观变量比电场或总电子居数的平均能量更准确地描述了电子的行为。本研究的目的是找到一个流体动力输运方程系统，当解出时，将提供关于这个宏观变量的信息。初步研究表明，高能电子亚居的输运方程系统可以由三个输运方程简化为一个输运方程。这使我们能够轻松地求解输运方程，并将我们新开发的新型撞击电离模型用作任何现有的没有撞击电离模型的设备模拟器的后处理器。可以预见，本研究将对半导体器件的计算机辅助设计产生重大影响。该模型可以很容易地整合到现有的器件仿真工具中，以更准确地预测晶体管中发生的撞击电离相关现象，包括雪崩击穿电压的预测。额外的计算成本非常小。

ECS-9710463 Ting -wei Tang Impact ionization is one of the most important factors limiting the performance of today's advanced semiconductor devices. The impact ionization is the source of hot-electron-induced device degradation and is responsible for avalanche breakdown of transistors. The main issue of impact ionization is the modeling of the impact ionization coefficient, (. Conventionally ( is modeled as a function of electric field or the average energy of total electron population. Unfortunately, these models do not properly describe the non-local of impact ionization. In this research, we propose an innovative approach to model ( as a unique function of the average energy of only those high-energy exceed the impact ionization threshold energy. This average macroscopic variable describes the behavior of ( more accurately than the electric field or the average energy of total electron population. The objective of this research is then to find a system of hydrodynamic transport equations, when solved, will provide information about this macroscopic variable. A preliminary investigation indicates that the system of transport equations for the high-energy electron subpopulation can be reduced from three to a single transport equation. This enables us to solve the transport equation easily and use our newly developed novel impact ionization model as a post processor to any existing device simulator which does not have an impact ionization model. A great impact of this research on the computer-aided design of semiconductor devices can be anticipated. The model can be readily incorporated in existing device simulation tools for more accurate prediction of impact ionization related phenomena occurring in the transistors, including the prediction of the avalanche breakdown voltage. The additional computational cost is very minimal.