三維微電子真空元件模擬

Abstract

近二十年來，真空微電子場放射元件( Vacuum Microelectronic Field Emission Devices) 由於具有一些優於傳統矽質金氧半場效電晶體( Silicon MOSFET )的特性，而引起廣泛的注意。為了深入了解此類元件的 特性並決定最佳之元件結構，適當的元件模擬器是迫切需要的。在本論文 中，我們發展了一套考量主要物理現象的三維場放射元件數值模擬器。此 物理模型包含三維波松方程式( 3D Poisson Equation )、修正的Fowler- Nordheim 公式、電子於真空的運動方程式、以及空間電荷效應。同時， 此數值模擬器也運用了自我一致 ( Self-Consistent)的模擬流程。本論 文模擬了場放射二極體及場放射三極體的電特性。而大部份的射極電流來 自射極的邊緣驗證了三維數值模擬器的必要性，因為這是典型的三維效應 。在較低電壓時，空間電荷效應並不顯注。溫度變化對元件的影響很小。 對微米尺寸的元件，電子傳輸時間約為0.1 ps至1 ps，其截止頻率在160 GHz以上。除此之外，元件的幾何結構對其特性影響頗大。 In the past twenty years, vacuum microelectronic emission devices (FED's) have attracted much attention due to their intrinsic performance advantages over the current silicon MOSFET's. In order to study the characteristics of the devices and to obtain optimal device structures, an approriate FED simulator becomes necessary. In this thesis,we develop a consistent 3D FED simulator which incorporates major physical phenomena in FED. The physical model includes the 3D Poisson equation, the modified Fowler-Nordheim field emission model,the electron motion in vacuum, and the space charge effect. The electrical performance of field emission diodes and triodes is evaluated in our study. The "must" of a 3D simulator is confirmed by that most of the emission current comes from the edges of emitters, which is a typical 3D effect. The space charge effect is trivial at lower voltages. Temperature vari- ation has little influence on the device performance. Electron transit time is about .1ps to 1ps for a device with micrometer- size dimensions.In addition,the FED geometrical structure plays a critical role on the device characteristics.