塑膠基板上薄膜應力對主動式元件特性之影響分析

Abstract

近年來，現代化家電用品的需求日增，使得大、小尺寸的液晶顯示器應用範圍越來越為廣泛。在所有液晶顯示器類型中，塑膠基板液晶顯示器正符合此產品演進的發展趨勢。塑膠基板有量輕、形薄、以及不易摔壞的優點。然而，在塑膠基板上沈積薄膜時，製程溫度變化使得塑膠基板產生形變及彎曲並引發很大的薄膜應力，最終將使得薄膜產生龜裂甚至剝離。 為了使塑膠基板上主動元件具高可靠性，並避免薄膜因應力過大而產生龜裂，我們在塑膠基板與主動元件間沈積緩衝層。藉著緩衝層可增加薄膜對塑膠基板的黏著性、緩和薄膜應力並增加主動元件的可靠性。 我們將評估各種緩衝層結構的可行性，並量測其產生之薄膜應力。進而對具可行性之緩衝層結構進行可靠性分析，並探討薄膜應力與可靠性分析結果之關係。最後，我們將於塑膠基板上製作金屬-絕緣層-金屬(MIM)二極體，並探討薄膜應力對金屬-絕緣層-金屬二極體特性之影響。

In recent years, increasing requirement of modern household appliances promote the application range of small or large size Liquid Crystal Displays (LCDs) extensively. Among all types of LCDs, polymer-film LCDs (PFLCDs) are adequate for the tendency of product improvement. Plastic substrates have the advantages of low cost, light-weighted, thin-shaped , and rugged characteristics. However, when a deposited film is formed on the plastic substrates, a deformation or a curl of the plastic substrates are caused and high thin film stresses are induced, resulting in peeling of a film. It is therefore an object to provide active devices with high reliability, which allows to reduce weight and production cost, and to avoid curl of the plastic substrate, a peeling and crack of a film. In order to attain the mentioned object, it is indispensable to form a buffer layer in order to obtain an adhesion, stress alleviation, and reliability of the plastic substrate and the active device. We estimate the feasibility of varied buffer layer structures, and the thin film stress is also measured. Further, reliability tests are carried out for varied feasible buffer layer structure, the relations between thin film stress and reliability will be discussed. Eventually, Metal-Insulator-Metal diodes (MIM diodes) on plastic substrates are fabricated and influences of thin film stress on characteristics of MIM are also discussed in the thesis. Abstract (Chinese) I Abstract (English) III Acknowledgements V Contents VI Table Captions IX Figure Captions X Chapter 1 Introduction 1 1.1 General Background and Motivation 1 1.2 Organization of Thesis 3 Chapter 2 Characterization of the Plastic Substrates 5 2.1 Introduction 5 2.2 Characterization of Plastic Substrates 6 2.2.1 Thermal Stability of Plastic Substrates 7 2.2.2 Thermal Expansion Coefficient of Plastic Substrates 8 2.2.3 Chemical Resistance of Plastic Substrates 9 2.2.4 Surface Roughness Conditions of Plastic Substrates 9 2.3 Summary 10 Chapter 3 Thin Film Stress Analysis and Reliability Tests of Varied Buffer Layer Structures 11 3.1 Introduction 11 3.2 Feasibility of Varied Buffer Layer Structures 12 3.2.1 Feasibility of Inorganic Buffer Layer Structures 13 3.2.1.1 Single Inorganic Buffer Layer Structure 13 3.2.1.2 Single Inorganic Buffer Layer with Adhesion Layer Structure 13 3.2.2 Feasibility of Organic Buffer Layer Structures 14 3.2.2.1 Single Organic Buffer Layer Structure 14 3.3 Thin Film Stress Analysis of Varied Feasible Buffer Layer Structures 15 3.3.1 Thin Film Stress Measurement Theory 15 3.3.2 Thin Film Stress of Varied Feasible Buffer Layer Structures 16 3.4 Reliability Tests of Varied Feasible Buffer Layer Structures 17 3.4.1 Peeling Test 18 3.4.2 Thermal Stability Test 19 3.5 Summary 20 Chapter 4 Influences of Thin Film Stress on Active Devices on Plastic Substrates 22 4.1 Introduction 22 4.2 Formation of Anodic Ta2O5 Insulator 23 4.2.1 Anodic Oxidation System Setup 23 4.2.1.1 Selection of Electrolyte 23 4.2.1.2 Constant Anodic Voltage and Constant Anodic Current Mode during Anodization 24 4.2.2 Experiment of Fabrication Anodic Ta2O5 Insulator 25 4.2.2.1 Growth Rate of Anodic Tantalum Oxide Film 25 4.2.2.2 I-V Characteristics of Anodic Tantalum Oxide Film 26 4.3 Fabrication of MIM Diodes on Plastic Substrates 28 4.3.1 Process Flows of MIM diodes on Plastic Substrates 28 4.4 I-V Characteristics of MIM Diodes on Plastic Substrates 29 4.4.1 Influences of Thin Film Stress on Current Symmetry 29 4.4.2 Influences of Thin Film Stress on Nonlinear Coefficient 30 4.5 Summary 31 Chapter 5 Conclusions and Future Works 32 5.1 Conclusions 32 5.2 Future Works 34 References 35 Publications 39