用於微波可調式相位移位器的鈦酸鍶鋇薄膜製備與電性

Abstract

本篇論文主要探討應用於動態隨機存取記憶體(DRAM)以及高頻微波元件之鈦酸鍶鋇(BST)薄膜的製程與性質。鈦酸鍶鋇為非常適合應用在高密度動態隨機存取記憶體電容器的高介電係數材料，因為其具有較高的介電係數、低漏電流、低損耗率和長使用壽命的特性。本論文首先比較不同成長溫度與不同氧偏壓比例對於鈦酸鍶鋇薄膜電性的影響，接著配合不同的後續退火處理方法，包括在氧氣氛及一氧化二氮中以不同的溫度做快速退火處理，氧氣及一氧化二氮的電漿做低溫退火處理或是結合快速退火以及電漿處理的方法，以期改善薄膜的電性與探討其差異原因。 其次，近幾年來高介電係數與在高電場下可調整介電係數的鐵電材料廣被注意，以這類鐵電材料製作的微波電路可以採用製程技術，將微波微帶(microstrip)的電路結構以高機集化的方式整合在一體積小的晶片上，以低的直流電壓來做調節(tunning)，比較下此類微波元件顯然有製作容易，價格低廉，使用方便的優勢。所以本論文重點為製作高介電係數及低微波損耗的鈦酸鍶鋇膜，並應用微波微帶線結構，測量鈦酸鍶鋇膜於微波頻段的介電係數及損耗。

BST (BaxSr1-xTiO3) thin films have been demonstrated to be highly promising storage dielectrics in DRAM applications and microwave device at high frequency. The BST is one of the most promising materials due to its high dielectric constant, low leakage current, low dissipation factor and a TDDB over 10 years for high density DRAM capacitor. In this work, the electrical properties of BST film deposited at different substrate temperatures and their correlation with various OMR are studied. In addition, we present the effect of different annealing treatments, including rapid thermal annealing in O2 and N2O ambient at various temperatures, O2 and N2O plasma annealing at low temperature and two-step annealing, on the electrical and dielectric properties of BST films. In the last few years, there has been considerable progress in the deposition of high quality BST thin films for microwave device applications due to its large electric field dependent dielectric constant and composition dependent Curie temperature. The dielectric constant of BaxSr1-xTiO3 (BST) thin films can be varied (tunning) by an applied direct current (dc) electric field, and in the connection the microstrip/ ferroelectrics combination looks very promising for a realization of microwave devices. Therefore, in this study, we report not only on the fabrication of BST films and test the performance of BST films, but also extract the dielectric parameters at microwave frequencies with network analyzer and conformal mapping technique. ABSTRACT (ENGLISH)……………………………………………………………...ii ACKNOWLEDGEMENTS…………………………………………………………...iii CONTENT……………………………………………………………………………..iv TABLE LISTS…………………………………………………………………………vi FIGURE CAPTIONS………………………………………………………………...vii CHAPTER 1 Introduction……..……………………………………………………...1 1-1 Future Directions For DRAM Memory Cell Technology…..……………….………1 1-2 General Background of BST thin films ……………………………………………..3 1-3 The New Application for microwave tunable phase-shifter………….……………..7 1-4 Motivation…………………………………………………………………………...9 1-5 Thesis Organization…………………………………………………………………9 CHAPTER 2 Experimental Details……….……………………..………....11 2-1 Sputtering System…………………….……………………………………………11 2-2 Preparation of Sputtering Target…………….. ……………………………………12 2-3 Rapid Thermal Process System…….…………….………………………………...12 2-4 Film Preparation……………………………………….…………………………...13 2-5 Measurements ……………..……………………………….……………………...14 2-5.1 Ellipsometry……………….……………………………….………………..14 2-5.2 X-Ray Diffraction Analysis (XRD)………………..………………………..14 2-5.3 Atomic force microscopy (AFM)…...………………………………….…...14 2-5.4 Scanning Electron Microscopy(SEM)……………………………………....14 2-5.5 n&k analyzer…………………………………………………….…………..15 2-5.6 Current-voltage (I-V) measurements……………………………………......15 2-5.7 Capacitance-voltage (C-V) measurements……………………………….…15 CHAPTER 3 Properties of BST Films with various Annealing Treatments……....17 3-1 Introduction……………………..…………………………………………….…..17 3-2 Results and Discussion……..………………………………………………….…19 3-2.1 Effect of Substrate Temperature and Ar/O2 Flow Ratio……………....19 3-2.1.1 Experimental Procedures…………………………………….….19 3-2.1.2 Physical Characterizations………………….…………………20 3-2.1.3 Electrical Characterizations………..…………….……………22 3-2.2 Rapid Thermal Annealing with Various Annealing Temperatures……24 3-2.2.1 Experimental Procedures……………………………………....24 3-2.2.2 Physical Characterizations……………….……………….……24 3-2.2.3 Electrical Characterizations……………………….… ………..26 3-2.3 Plasma Annealing …………………………………………………….28 3-2.3.1 Experimental Procedures………………………………….…...28 3-2.3.2 Physical Characterizations……………………………….…….28 3-2.3.3 Electrical Characterizations……………………………………29 3-2.4 Two-Step Annealing…………………………………….…………….30 3-2.4.1 Experimental Procedures……………………………….……...30 3-2.4.2 Physical Characterizations……………………………….…….31 3-2.4.3 Electrical Characterizations……………………………………32 3-3 Summary………………….……………………………………………….…….32 CHAPTER 4 Microwave properties of BST Films…………………………….….35 4-1 Introduction……….………………………………………………………….…...35 4-2 Theory……….………………………………………………………….……..…36 4-3 Experimental Procedures………………………………………………….……...37 4-4 Results and Discussion….……………………………………………….……….41 4-5 Summary………..…………………………………………………………..……..43 CHAPTER 5 CONCLUSIONS……………………………………………………..44 5-1 CONCLUSIONS…………………………………………………………….44 REFERENCES………………………………..……………………………………….…..46