Microelectronic Applications of Chemical Mechanical Planarization

YUZHUO LI is a tenured professor in the Department of Chemistry and a member of the Center for Advanced Materials Processing (CAMP) at Clarkson University in Potsdam, New York. He is a member of the American Chemical Society, Chinese American Chemical Society, Materials Research Society, and The Electrochemical Society. He also holds guest professorships at several Chinese universities, including Yangzhou University and Sun Yat-Sen University.

• Foreword xixContributing Authors xxiii1 Why CMP? 1Yuzhuo Li1.1 Introduction 11.2 Preparation of Planar Surface 21.2.1 Multilevel Metallization and the Need for Planarization 21.2.2 Degrees of Planarization 41.2.3 Methods of Planarization 51.2.4 Chemical and Mechanical Planarization of Dielectric Films 71.2.5 Preparation of Planar Thin Films for Non-IC Applications Using CMP 81.3 Formation of Functional Microstructures 91.3.1 RC Delay and New Interconnect Materials 91.3.2 Damascene and Dual Damascene 121.3.3 Tungsten CMP 151.3.4 STI 161.4 CMP to Correct Defects 191.5 Advantages and Disadvantages of CMP 201.6 Conclusion 212 Current and Future Challenges in CMP Materials 25Mansour Moinpour2.1 Introduction 252.2 Historic Prospective and Future Trends 272.3 CMP Material Characterization 322.3.1 Thermal Effects 332.3.2 Slurry Rheology Studies 352.3.3 Slurry–Pad Interactions 382.3.4 Pad Groove Effects 422.3.5 Pad–Wafer Contact and Slarry Transport: Dual Emission Laser Induced Fluorescence 432.3.6 Dynamic Nuclear Magnetic Resonance 452.3.7 CMP Slurry Stability and Correlation with Defectivity 492.4 Conclusions 513 Processing Tools for Manufacturing 57Manabu Tsujimura3.1 CMP Operation and Characteristics 573.2 Description of the CMP Process 593.3 Overview of Polishers 603.3.1 CMP System 603.3.2 Brief History of CMP Systems 613.3.3 Diversity in CMP Tools 623.3.4 Polisher 623.3.5 Cleaning Module in a Dry-in/Dry-out System 643.4 Carriers and Dressers 653.4.1 Functions of Carriers and Dressers 653.4.2 Carrier 653.4.3 Profile Control by Carriers 683.4.4 Dressers 693.5 In Situ and Ex Situ Metrologies 723.5.1 Application 723.5.2 Representative Monitors 723.5.3 Other Applications for the Monitors 753.5.4 Communication 753.6 Conclusions 784 Tribometrology of CMP Process 81Norm Gitis and Raghu Mudhivarthi4.1 Introduction 814.2 Tribometrology of CMP 824.3 Factors Influencing the Tribology During CMP 854.3.1 Process Parameters During CMP 854.3.2 Polishing Pad Characteristics 884.3.3 Slurry Characteristics 904.3.4 Water Contour Characterists 924.4 Optimizing Pad Conditioning Process 924.4.1 PadProbeTM 924.4.2 Effect of Temperature 1004.5 Conditioner Design 1024.6 CMP Consumable Testing 1054.6.1 Slurry Testing 1054.6.2 Pad Testing 1084.6.3 Retaining Rings 1104.7 Defect Analysis 1134.7.1 Coefficient of Friction and Acoustic Emission Signal 1134.7.2 Advanced Signal Processing 1144.8 Summary 1175 Pads for IC CMP 123Changxue Wang, Ed Paul, Toshihiro Kobayashi and Yuzhuo Li5.1 Introduction 1235.2 Physical Properties of CMP Pads and Their Effects on Polishing Performance 1245.2.1 Pad Types 1245.2.2 Pad Microstructures and Macrostructures 1255.2.3 Polyurethane Pad Properties and Control 1275.2.3.1 Hardness Young’s Modulus, and Strength 1275.2.3.2 Pad Porosity/Density 1285.2.3.3 Pad Thickness 1285.2.3.4 Pad Stiffness/Stacked Pads 1295.2.3.5 Pad Grooves 1295.2.4 Effects of Pad Property on Polishing Performance 1295.2.4.1 Pad Roughness Effects 1305.2.4.2 Pad Porosity/Density Effects 1315.2.4.3 Pad Hardness, Young’s Modulus, Stiffness, and Thickness Effects 1365.2.4.4 Pad Groove Effects 1385.3 Chemical Properties of CMP Pads and Their Effects on Polishing Performances 1405.3.1 Polyurethane Pad Components 1405.3.2 Polyurethane Property Control by Chemical Components 1405.3.3 Chemical Effects on Polishing Performance 1415.4 Pad Conditioning and Its Effect on CMP Performance 1425.5 Modeling of Pad Effects on Polishing Performance 1455.5.1 Review of Modeling of Pad Effects on Polishing Performance 1455.5.2 Modeling of Pad Effects on Polishing Performance 1485.5.2.1 Pads and Pressure 1485.5.2.2 Pads and Abrasives 1505.5.2.3 Pads, Dishing, and Erosion 1545.6 Novel Designs of CMP Pads 1595.6.1 Particle-Containing Pads 1595.6.2 Surface-Treated Pads 1625.6.3 Reactive Pad 1646 Modeling 171Leonard Borucki and Ara Philipossian6.1 Introduction 1716.2 A Two-Step Chemical Mechanical Material Removal Model 1726.3 Pad Surfaces and Pad Surface Contact Modeling 1756.4 Reaction Temperature 1786.5 A Polishing Example 1856.6 Topography Planarization 1897 Key Chemical Components in Metal CMP Slurries 201Krishnayya Cheemalapati, Jason Keleher and Yuzhuo Li7.1 Introduction 2017.2 Oxidizers 2027.2.1 Nitric Acid 2027.2.2 Hydrogen Peroxide 2037.2.3 Ferric Nitrate 2107.2.4 Potassium Permanganate, Dichromates, and Iodate 2127.3 Chelating Agents 2147.3.1 Ammonia 2157.3.2 Amino Acids 2167.3.3 Organic Acids 2177.3.4 Thermodynamic Consideration and Quantitative Description 2187.4 Surfactants 2197.4.1 Structures and Physical Properties of Surfactants 2197.4.2 Dispersion of Particles 2217.4.3 Surface Modification of Wafer Surface 2227.5 Abrasive Particles 2257.5.1 Hardness 2257.5.2 Bulk Particle Density 2277.5.3 Particle Crystallinity and Shapes 2277.5.4 Particle Size and Oversized Particle Count 2287.5.5 Particle Preparation 2307.5.6 Surface Properties 2317.6 Particle Surface Modification 2337.7 Soft Particles 2347.8 Case Study: Organic Particles as Abrasives in Cu CMP 2357.8.1 Particle Characterization 2357.8.2 Material Removal Rate and Selectivity 2357.8.3 Step Height Reduction Efficiency and Overpolishing Window 2397.8.4 Summary on the Organic Particles 2397.9 Conclusions 2398 Corrosion Inhibitor for Cu CMP Slurry 249Suresh Kumar Govindaswamy and Yuzhuo Li8.1 Thermodynamic Considerations of Copper Surface 2508.2 Types of Passivating Films on Copper Surface Under Oxdizing Conditions 2528.3 Effect of pH on BTA in Glycine-Hydrogen Peroxide Based Cu CMP Slurry 2578.4 Evaluation of Potential BTA Alternatives for Acidic Cu CMP Slurry 2598.5 Electrochemical Polarization Study of Corrosion Inhibitors in Cu CMP Slurry 2638.6 Hydrophobicity of the Surface Passivation Film 2658.7 Competitive Surface Adsorption Behavior of Corrosion Inhibitors 2668.8 Summary 2709 Tungsten CMP Applications 277Jeff Visser9.1 Introduction 2779.2 Basic Tungsten Application, Requirements, and Process 2789.2.1 Basic Applications of Tungsten CMP 2789.2.2 Basic W CMP Requirements and Procedures 2819.3 W CMP Defects 2829.4 Various W CMP Processing Options 2859.4.1 Basic Considerations 2859.4.2 Barrier Polishing 2899.4.3 Oxide Buffing 2899.4.4 Post-W CMP Cleaning 2909.5 Overall Tungsten Process (Various Processing Design Options and Suggestions) 2909.5.1 W CMP Process Controls 2909.5.2 Platen Temperature Control 2919.5.3 Slurry Selectivity 2929.6 Conclusions 29210 Electrochemistry in ECMP 295Jinshan (Jason) Huo10.1 Introduction 29510.2 Physical and Chemical Processes in Electrochemical Planarization 29710.2.1 Electrode/Electrolyte Interface 29710.2.2 Electrochemical Reaction 29810.2.3 Mass Transport 29910.2.4 Anodic Polarization Curve and Conditions for Electrochemical Planarization 30010.3 Mechanisms and Limitation of Electrochemical Planarization 30410.3.1 Ohmic Leveling 30410.3.2 Diffusion Leveling 30510.3.3 Migration Leveling 30710.4 In Situ Analysis of Anodic/Passivation Films 30910.4.1 Impedance Measurement 30910.4.2 Electrochemical Impedance Spectroscopy 31010.4.3 Ellipsometry 31110.5 Modified Electrochemical Polishing Approaches 31211 Planarization Technologies Involving Electrochemical Reactions 319Laertis Economikos11.1 Introduction 31911.2 CMP 32111.3 ECP 32211.4 ECMP 32611.5 Full Sequence Electrochemical–Mechanical Planarization 33411.6 Conclusions 34012 Shallow Trench Isolation Chemical Mechanical Planarization 345Yordan Stefanov and Udo Schwalke12.1 Introduction 34512.2 LOCOS to STI 34612.3 Shallow Trench Isolation 34912.4 The Planarization Step in Detail 35112.5 Optimization Techniques 35812.5.1 Dummy Active Area Insertion 35912.5.2 Patterned Oxide Etch Back 35912.5.3 Nitride Overcoat 36012.5.4 EXTIGATE 36112.5.5 Selective Oxide Deposition 36312.5.6 Polysilicon-Filled Trenches 36312.6 Outlook 36413 Consumables for Advanced Shallow Trench Isolation (STI) 369Craig D. Burkhard13.1 Introduction 36913.2 Representative Testing Wafers for STI Process and Consumable Evaluations 37113.3 Effects of Abrasive Types on STI Slurry Performance 37313.4 Effects of Chemical Additives to Oxide: Nitride Selectivity 37913.5 Effect of Slurry pH 38513.6 Effect of Abrasive Particle Size on Removal Rate and Defectivity 38813.7 Conclusion 39514 Fabrication of Microdevices Using CMP 401Gerfried Zwicker14.1 Introduction 40114.2 Microfabrication Processes 40214.3 Microfabrication Products 40314.4 CMP Requirements in Comparison with IC Fabrication 40414.5 Examples of CMP Applications for Microfabrication 41214.5.1 Case Study I: Integrated Pressure Sensor 41614.5.2 Case Study II: Poly-Si Surface Micromachining and Angular Rate Sensor 41714.5.3 Case Study III: Infrared Digital Micromirror Array 42214.5.4 More Representative Applications 42514.6 Outlook 42615 Three-Dimensional (3D) Integration 431J. Jay McMahon, Jian-Qiang Lu and Ronald J. Gutmann15.1 Overview of 3D Technology 43115.2 Factors Motivating Research in 3D 43215.2.1 Small Form Factor 43215.2.2 Heterogeneous Integration 43315.2.3 Performance Enhancement 43415.3 Approaches to 3D 43515.3.1 Singulated Die 3D 43515.3.2 Wafer-Level 3D 43615.3.2.1 Wafer-Level 3D Using Oxide–Oxide Bonding 43615.3.2.2 Wafer-Level 3D Using Copper–Copper Bonding 43815.3.2.3 Wafer-Level 3D Using Adhesive Bonding 43915.3.2.4 3D Integration Using Redistribution Layer Bonding 44015.3.2.5 Summary of Wafer Level 3D Approaches 44015.4 Wafer-Level 3D Unit Processes 44215.4.1 Wafer-to-Wafer Alignment 44215.4.2 Wafer-to-Wafer Bonding 44415.4.2.1 Oxide–Oxide and Silicon–Oxide Wafer Bondings 44415.4.2.2 Copper–Copper Wafer Bonding 44415.4.2.3 Polymer Adhesive Wafer Bonding 44615.4.3 Wafer Thinning for 3D 44715.4.3.1 Timed Removal Thinning Approaches 44815.4.3.2 Thinning to Either an Etch or Polish Stop 44815.4.4 Through-Silicon Vias 44915.5 Planarity Issues in 3D Integration 45015.5.1 CMP Planarity Capabilities 45115.5.1.1 Nano- and Microscale Planarization 45115.5.1.2 Wafer-Scale Planarity 45115.5.2 Planarity Issues for Various 3D Approaches 45215.5.2.1 CMP for Via-Last Approach to 3D Using Oxide-to-Oxide Bonding 45215.5.2.2 CMP for Via-Last Approach to 3D Using Polymer Adhesive Bonding 45415.5.2.3 CMP for Via-First Approach to 3D Using Copper-to-Copper Bonding 45515.5.2.4 CMP for Via-First 3D Using Redistribution Layer Bonding 45515.6 Conclusions 45616 Post-CMP Cleaning 467Jin-Goo Park, Ahmed A. Busnaina and Yi-Koan Hong16.1 Introduction 46716.2 Types of Post-CMP Cleaning Processes 46816.2.1 Wet Bath Type Cleaning 46816.2.2 Single Wafer Cleanings 46916.2.2.1 Immersion-Type Single-Wafer Post-CMP Cleaning System 46916.2.2.2 Single-Wafer Spin Cleaner 46916.2.2.3 Brush Cleaning 47316.2.2.4 Drying 47516.3 Post-CMP Cleaning Chemistry 47716.3.1 Conventional Wet Cleanings 47716.3.2 Chemicals Used in Post-CMP Cleaning and their Roles 47816.3.2.1 NH4OH 47816.3.2.2 HF 47816.3.2.3 Organic Acids 47916.3.2.4 Surfactants 47916.4 Post-CMP Cleaning According to Applications 48016.4.1 Post-Oxide CMP Cleaning 48016.4.2 Post-W CMP Cleaning 48116.4.3 Post-STI CMP Cleaning 48116.4.4 Post-Poly-Si CMP Cleaning 48216.4.5 Post-Cu/Low-k CMP Surface Cleaning 48416.4.5.1 Corrosion 48616.4.5.2 Organic Residue 48716.4.5.3 Low-k Materials 48916.4.5.4 Effect of Other Additives on Cleaning 49116.5 Adhesion Force, Friction Force, and Defects During Cu CMP 49216.5.1 Adhesion Force of Silica and Alumina on Cu 49316.5.2 Friction Force in Cu CMP Process 49416.5.3 Removal Rates of Cu Surface in Cu CMP 49416.5.4 Surface Quality of Cu After Cu CMP Process 49616.5.5 Correlation Among Friction, Adhesion Force, Removal Rate, and Surface Quality in Cu CMP 49816.6 Case Study: Megasonic Post-CMP Cleaning of Thermal Oxide Wafers 49916.6.1 Experimental Procedure 49916.6.2 The Effect of Megasonic Input Power 50016.6.3 The Effect of Temperature 50316.6.4 The Effect of Etching on Cleaning 50316.7 Summary 50517 Defects Observed on the Wafer After the CMP Process 511Paul Lefevre17.1 Introduction 51117.2 Defects After Oxide CMP 51217.2.1 Introduction 51217.2.2 Scratches 51317.2.3 Color Variation—Oxide Thickness Variation 51617.2.4 Slurry Residues and Organic Residues 51817.2.5 Other Particles 51917.2.6 Crystal Formation 51917.2.7 Traces Elements 51917.2.8 Radioactive Contamination 51917.2.9 Defects Existing Before Oxide CMP 52017.2.10 Source of Defect-Causing Large Particles 52017.3 Defects After Polysilicon CMP 52017.3.1 Introduction 52017.3.2 Scratches 52117.3.3 Polysilicon Residues 52117.3.4 Particles 52217.3.5 Residues 52217.3.6 Trace Elements 52217.3.7 Polysilicon Pitting and Voids 52317.3.8 Discoloration at the Edge of the Structure or Edge of the Arrays 52317.3.9 Defects Existing Before and Revealed After Polysilicon CMP 52317.3.10 Influence of Processing Temperature 52417.4 Defects After Tungsten CMP 52417.4.1 Introduction 52417.4.2 Corrosion, Pitting, and Void 52417.4.3 Tungsten Recess and Rough Tungsten Surface 52517.4.4 Scratches 52817.4.5 Discoloration—Edge Overerosion (EOE) 52917.4.6 Tungsten and Metal Liner Residues 53017.4.7 Particles, Slurry Residues, and Trace Metal 53117.4.8 Delamination 53117.4.9 Preexisting Defects Revealed After Tungsten CMP 53117.5 Defects After Copper CMP 53217.5.1 Introduction and Summary on Copper CMP Defects 53217.5.2 Copper Corrosion 53317.5.3 Copper Pitting 53517.5.4 Trenching at the Copper Line Edge 53717.5.5 Rough Copper and Copper Recess 53917.5.6 Discoloration—Metals Thickness Variations and/or Dielectric Thickness Variation 54017.5.7 Copper Electromigration 54217.5.8 Scratches 54417.5.9 Metal Residues 54417.5.10 Particles, Residues, and Trace Metals 54717.5.11 Delamination 54817.6 Defect Observation and Characterization Techniques 55117.6.1 Optical Microscope 55117.6.2 Scanning Electron Microscope 55217.6.3 Energy Dispersive X-Ray Spectroscopy (EDX) 55217.6.4 Scanning Auger Microscope (SAM) 55317.6.5 Atomic Force Microscopy 55317.7 Ensemble Defect Detection and Inspection Techniques 55417.7.1 Optical Scan of Flat Film Blanket Wafers 55417.7.2 Optical Scan of Patterned Wafers 55417.7.3 Defect Classification 55517.8 Consideration for the Future 55518 CMP Slurry Metrology, Distribution, and Filtration 563Rakesh K. Singh18.1 Introduction 56418.2 CMP Slurry Metrology and Characterization 56718.2.1 Slurry Health Monitoring and Control 56818.2.2 CMP Slurry Blend Control 56918.2.2.1 Two-Component Blend Control 57018.2.2.2 Three-Component Blend Control 57218.2.3 CMP Slurry Characterization 57318.2.4 Summary 57618.3 CMP Slurry Blending and Distribution 57718.3.1 Slurry Delivery Technologies 57818.3.2 Continuous (On-Demand) Slurry Dispense and Metrology 57818.3.3 Slurry Turnovers in Fab Distribution 58018.3.4 Slurry Abrasive Settling and Dispersion 58018.3.4.1 Slurry Settling Rate Quantification 58018.3.4.2 Settling Behavior of Different Abrasive CMP Slurries 58118.3.4.3 Required Minimum Flow Velocity for CMP Slurries 58418.3.5 Summary 58518.4 CMP Slurry Filtration 58618.4.1 Slurry Filtration Methodology 58718.4.2 Filter Design Consideration 58818.4.3 Slurry Filter Characterization 59118.4.4 CMP Process and Consumable Trends and Challenges 59218.4.5 Slurry Filtration-Case Studies 59518.4.5.1 Silica Dispersion Single-Pass High-Retention Filtration 59518.4.5.2 Silica Slurry POU and Recirculation 59618.4.5.3 Silica Ceria and Alumina Slurry Tighter Filtration 59918.4.5.4 Polystyrene Latex (PSL) Bead Solution Filtration 60218.4.6 Summary 60218.5 Pump Handling Effects on CMP Slurry Filtration—Case Studies 60318.5.1 Pump Technologies and Applications 60418.5.2 Pump Shearing Effects on Slurry Abrasives 60518.5.3 Pump Handling and Filtration Data 60618.5.4 Test Cases 60718.5.5 Summary 62019 The Facilities Side of CMP 627John H. Rydzewski19.1 Introduction 62719.2 Characterization of the CMP Waste Stream 62819.3 Materials of Compatibility 62919.4 Collection System Methodologies 63119.5 Treatment System Components 63219.5.1 Collection Tank and pH Adjustment 63219.5.2 Oxidizer Removal 63319.5.3 Organics Removal 63519.5.4 Treatment of Suspended Solids 63519.5.5 Removal of Trace Metals 63819.6 Integration of Components—Putting It All Together 64419.6.1 Solids Treatment Before Metals Removal 64419.6.2 Solids Treatment After Metals Removal 64519.6.3 No Solids Removal 64619.7 Conclusions 64720 CMP—The Next Fifteen Years 651Joseph M. Steigerwald20.1 The Past 15 Years 65120.2 Challenges to Silicon IC Manufacturing 65520.3 New CMP Processes 66120.3.1 The Two-Year Development Cycle 66120.3.2 Finfet Transistors 66420.3.3 High-k Gate Oxides 66520.3.4 Other Examples 67020.4 CMP Challenges 67320.4.1 Development Time of New CMP Materials 67320.4.2 CMP Defect Reduction 67520.4.3 CMP Process Control 67720.4.3.1 CMP Film Thickness Control 67820.4.3.2 Process Control Systems, Consumables Material Control, and Excursion Prevention 68020.4.4 Cost of CMP 68320.5 Summary 68321 Utilitarian Information for CMP Scientists and Engineers 687Yongqing Lan and Yuzhuo Li21.1 Physical and Chemical Properties of Abrasive Particles 68721.2 Physical and Chemical Properties on Oxidizers 69021.3 Physical and Chemical Properties on Relevant Surfactants 69021.3.1 Classification of Surfactants 69021.3.2 Critical Micellar Concentration 69221.3.3 Ternary Phase Diagrams Involving Surfactants 69321.4 Relevant Pourbaix Diagram 69621.5 Commonly Used Buffering Systems 70321.6 Useful Web Sites 704Index 725