三維真空微電子場放射元件模擬器

Abstract

近年來,真空微電子場放射元件(Vacuum Microelectronic Field Emission Devices)由於具有一些較現行矽質金氧半場效電晶體元件(Si MOSFET Devices)更為優異的工作特性,而引起極大的注意.為了研究此一 元件之特性並獲致最佳之元件結構,一個合適的元件模擬器是不可或缺的. 在本論文中,我們發展了一個三維場放射元件模擬器,其中涵蓋了在此元件 中最主要之物理機制.我們考慮了:三維波松方程式(3D Poisson equation ),一個修正的場放射公式,電子在真空中的運動情形,及空間電 荷效應,此四項模型在本模擬器中.同時,我們亦提出了一個自我一致的 (self-consistent)模擬流程來完成此模擬器的發展.場放射二極體及場放 射三極體的電性在本論文中均被模擬.我們發現在一般情形中,約有50%的 放射電流來自射極的邊緣,此證據顯示了一個三維模擬器的必要性.當放射 的電流密度達5x10^7A/cm^2時,空間電荷效應將逐漸顯著.溫度變化對元件 的影響很小.對微米大小的元件而言,電子由射極至集極的時間約為0.1ps 到1ps.此外,元件的幾何結構對元件特性有極大的影響.在本論文中,我們 亦探討元件幾何參數對元件特性的效應.這些幾何參數包含了:射極至集極 的距離,射極之斜角,閘極和射極尖端的相對位置,及閘極開口之大小. Vacuum Microelectronic field emission devices (FEDs) have acted much attention in recent years due to their intrinsicormance advantages over the current siliconl-oxide-semiconductor field effect transtor devices (MOSFET)ces. To study the characteristics of these devices and to obtainoptimal device structures, an appropriate FED simulator becomesssary. In this thesis, we develop a three-dimensional FEDlator which incorporates the major physical phenomena in the. Physical models include the three-dimensional Poisson equation,modified Fowler-Nordhein field emission model, the electronon in vacuum space and the space charge effect. A self-consistentulation flow is proposed. Electrical performance od field emission diodes and fielddes is evaluated in our study. The "must" of a three-dimensionallator is confirmed by that about 50% emission current is the-indiced current, which is a typical three- dimensional effect.space charge effect is significant only if the current densityigher than 5x10^7 A/cm^2 with the simulated FED structure.erature has littele influence on the device performance.tron transient time is about 0.1ps to 1ps for a device withometer-size dimension, which corresponds to a cut- off frequencye 160GHz. The geometry of FEDs plays a critical role on thece characteristics. For FEDs with a pyramid-type emitter, thect of the device geometric parameters, which include theter-to-collector distance, the pyramid angle, the relativetion of gate to emitter tip and the gate opening size, on thece performance are also studied in this thesis.