基於微機電製程之閘極場發射元件製作與分析

Abstract

本論文目的為製作出應用於多電子束微影的冷場發射源陣列，並使冷場發射源陣列在施加低電壓的情況下即可產生場發射電流。 在冷場發射源陣列的設計上，整體結構包含了具有小半徑的矽針陣列，用來產生場發射電流的陰極、能夠增強矽針尖端處電場的鉻金屬閘極、與用來接收場發射電流的陽極。 由於冷場發射源陣列的加工尺度為微米等級，故透過微機電製程進行元件的製作。陰極與閘極製程的步驟包含：以電子束微影定義閘極外型、以濕蝕刻製作出閘極及最後以氫氧化鉀蝕刻與反應式離子蝕刻製作出具有微小針尖半徑的矽針。另一種方式是使用聚焦離子束蝕刻直接讓矽針與閘極成形，但運用此方法做出的冷場發射源陣列須解決材料濺鍍造成無法產生場發射放電的問題。 將冷場發射源陣列製作出來後，置於真空度 下的環境中進行場發射實驗，並以金屬場發射電流公式分析實驗結果，得到冷場發射源陣列的特性：每根針場發射面積 、電場增強因子 、場發射起始電場 。在陽極電壓施加 ，閘極電壓施加 的情況下，每根針平均的場發射電流可達 。

This thesis presents MEMS processes to fabricate cold field emission arrays (CFEA) which are capable of working at low voltages in multiple electron-beam lithography. The CFEA consists of three main parts: cathode, gate and anode. The cathode has a silicon needle array which has small radius tip used to emit current. The gate is used to enhance the electric field near the silicon needle, and the anode is used to collect the electrons emitted from the cathode. The process consists in using e-beam lithography to define the shape of the gate which is then obtained by wet-etching. By using KOH etching and reactive ion etching (RIE), the silicon needles are achieved. Focused ion beam etching can be also used in CFEA’s fabrication. However, this kind of etching technology damages the structure of the silicon needles due to material sputtering and, as a consequence, the CFEA cannot emit electrons. Finally, when the process is completed, the field emission experiments are proceeded at high vacuum ( ) environmental conditions. The CFEA’s properties can be observed from using the field emission theory to analyze the measured values of the emission current. The experimental results are as follows: effective emission area , electric field enhancement factor , turn-on electric field , field emission current can achieve to per tip when the supplied voltage is for the anode and for the cathode.