化學氣相沉積低介電常數介電層與銅金屬整合之電性可靠度分析

Abstract

本論文主要探討兩種氧化矽系化學氣相沉積之低介電常數材料FSG (介電常數3.5-3.7)和OSG (介電常數2.9-3.0) 的基本物性和以及與銅金屬整合之電性可靠度。從紅外線吸收頻譜、薄膜厚度和折射率以及介電常數之量測分析結果顯示， FSG薄膜在氮氣中的熱穩定可達600℃，而OSG薄膜的熱穩定溫度也可達500℃。吾人利用加溫偏壓法來研究介電層與銅金屬整合之電性可靠度，發現Cu/USG/FSG/TOX/Si結構在250℃以0.8 MV/cm的電場加壓30分鐘，可使銅離子擴散進入FSG膜內。另一方面，Cu/USG/OSG/TOX/Si結構在 150℃以上述同樣的電場加壓30分鐘也可使銅離子擴散進入OSG膜內。由於OSG薄膜具有多孔性及低密度的結構，使得銅離子在OSG膜內比較容易漂移。此外，吾人在FSG的電容結構中觀察到負電場偏壓加熱時的一種獨特不穩定現象，可能與本研究之FSG薄膜係以高密度電漿化學氣相沉積法(HDPCVD)所成長者有關。

This thesis mainly investigates the thermal stability as well as the electrical reliability associated with the integration of Cu and two species of SiO2-based low-K CVD dielectric materials：fluorinated silicate glass (FSG, K=3.5-3.7) and organosilicate glass (OSG, K=2.9-3.0). It is found that the FSG dielectric films are thermally stable in N2 ambient at temperatures up to 600℃, while the thermal stability temperature of the OSG dielectric films is about 500℃. For the Cu-gated and USG-capped Cu/USG/FSG/TOX/Si MIS capacitor structure, bias-temperature stress (BTS) with an effective applied of 0.8 MV/cm for 30 minutes at 250℃ resulted in the presence of Cu ions in the FSG film. The same bias stress applied on the Cu/USG/OSG/TOS/Si MIS capacitor at 150℃ also resulted in Cu permeation into the OSG film. It turned out that copper ions drift faster in OSG than in FSG, presumably due to more porous and less dense structure in the OSG film. In addition, the negative bias-temperature instability was observed in the FSG film deposited with HDPCVD process. Abstract (English) Acknowledge Contents Table Captions Figure Captions Chapter 1. Introduction 1.1 General Background 1.2 Motivation 1.3 Thesis Organization Chapter 2. Basic Physical Properties of CVD Dielectric Films 2.1 Introduction 2.2 Experimental Procedures 2.3 Results and Discussion 2.3.1 FTIR Spectra 2.3.2 Thickness and Refractive Index 2.3.3 Dielectric Constant 2.4 Summary Chapter 3. Thermal stability of Cu/Low-K/Si system 3.1 Introduction 3.2 Experimental Procedures 3.2.1 Sample Preparation for I-V Measurements 3.2.2 Sample Preparation for C-V Measurements 3.2.3 Bias-Temperature Stress (BTS) Measurement 3.3 Results and Discussion 3.3.1 Current-Voltage (I-V) Measurement 3.3.2 The Bias-Temperature Stress (BTS) Results 3.3.3 The Static Igate-Vgate Characteristics 3.3.4 Material Analyses 3.3.5 Negative bias-temperature instability 3.4 Summary Chapter 4. Conclusion Reference