Microelectronic Applications of Chemical Mechanical Planarization

Table of Contents:
Foreword xix Contributing Authors xxiii 1 Why CMP? 1 Yuzhuo Li 1.1 Introduction 1 1.2 Preparation of Planar Surface 2 1.2.1 Multilevel Metallization and the Need for Planarization 2 1.2.2 Degrees of Planarization 4 1.2.3 Methods of Planarization 5 1.2.4 Chemical and Mechanical Planarization of Dielectric Films 7 1.2.5 Preparation of Planar Thin Films for Non-IC Applications Using CMP 8 1.3 Formation of Functional Microstructures 9 1.3.1 RC Delay and New Interconnect Materials 9 1.3.2 Damascene and Dual Damascene 12 1.3.3 Tungsten CMP 15 1.3.4 STI 16 1.4 CMP to Correct Defects 19 1.5 Advantages and Disadvantages of CMP 20 1.6 Conclusion 21 2 Current and Future Challenges in CMP Materials 25 Mansour Moinpour 2.1 Introduction 25 2.2 Historic Prospective and Future Trends 27 2.3 CMP Material Characterization 32 2.3.1 Thermal Effects 33 2.3.2 Slurry Rheology Studies 35 2.3.3 Slurry–Pad Interactions 38 2.3.4 Pad Groove Effects 42 2.3.5 Pad–Wafer Contact and Slarry Transport: Dual Emission Laser Induced Fluorescence 43 2.3.6 Dynamic Nuclear Magnetic Resonance 45 2.3.7 CMP Slurry Stability and Correlation with Defectivity 49 2.4 Conclusions 51 3 Processing Tools for Manufacturing 57 Manabu Tsujimura 3.1 CMP Operation and Characteristics 57 3.2 Description of the CMP Process 59 3.3 Overview of Polishers 60 3.3.1 CMP System 60 3.3.2 Brief History of CMP Systems 61 3.3.3 Diversity in CMP Tools 62 3.3.4 Polisher 62 3.3.5 Cleaning Module in a Dry-in/Dry-out System 64 3.4 Carriers and Dressers 65 3.4.1 Functions of Carriers and Dressers 65 3.4.2 Carrier 65 3.4.3 Profile Control by Carriers 68 3.4.4 Dressers 69 3.5 In Situ and Ex Situ Metrologies 72 3.5.1 Application 72 3.5.2 Representative Monitors 72 3.5.3 Other Applications for the Monitors 75 3.5.4 Communication 75 3.6 Conclusions 78 4 Tribometrology of CMP Process 81 Norm Gitis and Raghu Mudhivarthi 4.1 Introduction 81 4.2 Tribometrology of CMP 82 4.3 Factors Influencing the Tribology During CMP 85 4.3.1 Process Parameters During CMP 85 4.3.2 Polishing Pad Characteristics 88 4.3.3 Slurry Characteristics 90 4.3.4 Water Contour Characterists 92 4.4 Optimizing Pad Conditioning Process 92 4.4.1 PadProbeTM 92 4.4.2 Effect of Temperature 100 4.5 Conditioner Design 102 4.6 CMP Consumable Testing 105 4.6.1 Slurry Testing 105 4.6.2 Pad Testing 108 4.6.3 Retaining Rings 110 4.7 Defect Analysis 113 4.7.1 Coefficient of Friction and Acoustic Emission Signal 113 4.7.2 Advanced Signal Processing 114 4.8 Summary 117 5 Pads for IC CMP 123 Changxue Wang, Ed Paul, Toshihiro Kobayashi and Yuzhuo Li 5.1 Introduction 123 5.2 Physical Properties of CMP Pads and Their Effects on Polishing Performance 124 5.2.1 Pad Types 124 5.2.2 Pad Microstructures and Macrostructures 125 5.2.3 Polyurethane Pad Properties and Control 127 5.2.3.1 Hardness Young’s Modulus, and Strength 127 5.2.3.2 Pad Porosity/Density 128 5.2.3.3 Pad Thickness 128 5.2.3.4 Pad Stiffness/Stacked Pads 129 5.2.3.5 Pad Grooves 129 5.2.4 Effects of Pad Property on Polishing Performance 129 5.2.4.1 Pad Roughness Effects 130 5.2.4.2 Pad Porosity/Density Effects 131 5.2.4.3 Pad Hardness, Young’s Modulus, Stiffness, and Thickness Effects 136 5.2.4.4 Pad Groove Effects 138 5.3 Chemical Properties of CMP Pads and Their Effects on Polishing Performances 140 5.3.1 Polyurethane Pad Components 140 5.3.2 Polyurethane Property Control by Chemical Components 140 5.3.3 Chemical Effects on Polishing Performance 141 5.4 Pad Conditioning and Its Effect on CMP Performance 142 5.5 Modeling of Pad Effects on Polishing Performance 145 5.5.1 Review of Modeling of Pad Effects on Polishing Performance 145 5.5.2 Modeling of Pad Effects on Polishing Performance 148 5.5.2.1 Pads and Pressure 148 5.5.2.2 Pads and Abrasives 150 5.5.2.3 Pads, Dishing, and Erosion 154 5.6 Novel Designs of CMP Pads 159 5.6.1 Particle-Containing Pads 159 5.6.2 Surface-Treated Pads 162 5.6.3 Reactive Pad 164 6 Modeling 171 Leonard Borucki and Ara Philipossian 6.1 Introduction 171 6.2 A Two-Step Chemical Mechanical Material Removal Model 172 6.3 Pad Surfaces and Pad Surface Contact Modeling 175 6.4 Reaction Temperature 178 6.5 A Polishing Example 185 6.6 Topography Planarization 189 7 Key Chemical Components in Metal CMP Slurries 201 Krishnayya Cheemalapati, Jason Keleher and Yuzhuo Li 7.1 Introduction 201 7.2 Oxidizers 202 7.2.1 Nitric Acid 202 7.2.2 Hydrogen Peroxide 203 7.2.3 Ferric Nitrate 210 7.2.4 Potassium Permanganate, Dichromates, and Iodate 212 7.3 Chelating Agents 214 7.3.1 Ammonia 215 7.3.2 Amino Acids 216 7.3.3 Organic Acids 217 7.3.4 Thermodynamic Consideration and Quantitative Description 218 7.4 Surfactants 219 7.4.1 Structures and Physical Properties of Surfactants 219 7.4.2 Dispersion of Particles 221 7.4.3 Surface Modification of Wafer Surface 222 7.5 Abrasive Particles 225 7.5.1 Hardness 225 7.5.2 Bulk Particle Density 227 7.5.3 Particle Crystallinity and Shapes 227 7.5.4 Particle Size and Oversized Particle Count 228 7.5.5 Particle Preparation 230 7.5.6 Surface Properties 231 7.6 Particle Surface Modification 233 7.7 Soft Particles 234 7.8 Case Study: Organic Particles as Abrasives in Cu CMP 235 7.8.1 Particle Characterization 235 7.8.2 Material Removal Rate and Selectivity 235 7.8.3 Step Height Reduction Efficiency and Overpolishing Window 239 7.8.4 Summary on the Organic Particles 239 7.9 Conclusions 239 8 Corrosion Inhibitor for Cu CMP Slurry 249 Suresh Kumar Govindaswamy and Yuzhuo Li 8.1 Thermodynamic Considerations of Copper Surface 250 8.2 Types of Passivating Films on Copper Surface Under Oxdizing Conditions 252 8.3 Effect of pH on BTA in Glycine-Hydrogen Peroxide Based Cu CMP Slurry 257 8.4 Evaluation of Potential BTA Alternatives for Acidic Cu CMP Slurry 259 8.5 Electrochemical Polarization Study of Corrosion Inhibitors in Cu CMP Slurry 263 8.6 Hydrophobicity of the Surface Passivation Film 265 8.7 Competitive Surface Adsorption Behavior of Corrosion Inhibitors 266 8.8 Summary 270 9 Tungsten CMP Applications 277 Jeff Visser 9.1 Introduction 277 9.2 Basic Tungsten Application, Requirements, and Process 278 9.2.1 Basic Applications of Tungsten CMP 278 9.2.2 Basic W CMP Requirements and Procedures 281 9.3 W CMP Defects 282 9.4 Various W CMP Processing Options 285 9.4.1 Basic Considerations 285 9.4.2 Barrier Polishing 289 9.4.3 Oxide Buffing 289 9.4.4 Post-W CMP Cleaning 290 9.5 Overall Tungsten Process (Various Processing Design Options and Suggestions) 290 9.5.1 W CMP Process Controls 290 9.5.2 Platen Temperature Control 291 9.5.3 Slurry Selectivity 292 9.6 Conclusions 292 10 Electrochemistry in ECMP 295 Jinshan (Jason) Huo 10.1 Introduction 295 10.2 Physical and Chemical Processes in Electrochemical Planarization 297 10.2.1 Electrode/Electrolyte Interface 297 10.2.2 Electrochemical Reaction 298 10.2.3 Mass Transport 299 10.2.4 Anodic Polarization Curve and Conditions for Electrochemical Planarization 300 10.3 Mechanisms and Limitation of Electrochemical Planarization 304 10.3.1 Ohmic Leveling 304 10.3.2 Diffusion Leveling 305 10.3.3 Migration Leveling 307 10.4 In Situ Analysis of Anodic/Passivation Films 309 10.4.1 Impedance Measurement 309 10.4.2 Electrochemical Impedance Spectroscopy 310 10.4.3 Ellipsometry 311 10.5 Modified Electrochemical Polishing Approaches 312 11 Planarization Technologies Involving Electrochemical Reactions 319 Laertis Economikos 11.1 Introduction 319 11.2 CMP 321 11.3 ECP 322 11.4 ECMP 326 11.5 Full Sequence Electrochemical–Mechanical Planarization 334 11.6 Conclusions 340 12 Shallow Trench Isolation Chemical Mechanical Planarization 345 Yordan Stefanov and Udo Schwalke 12.1 Introduction 345 12.2 LOCOS to STI 346 12.3 Shallow Trench Isolation 349 12.4 The Planarization Step in Detail 351 12.5 Optimization Techniques 358 12.5.1 Dummy Active Area Insertion 359 12.5.2 Patterned Oxide Etch Back 359 12.5.3 Nitride Overcoat 360 12.5.4 EXTIGATE 361 12.5.5 Selective Oxide Deposition 363 12.5.6 Polysilicon-Filled Trenches 363 12.6 Outlook 364 13 Consumables for Advanced Shallow Trench Isolation (STI) 369 Craig D. Burkhard 13.1 Introduction 369 13.2 Representative Testing Wafers for STI Process and Consumable Evaluations 371 13.3 Effects of Abrasive Types on STI Slurry Performance 373 13.4 Effects of Chemical Additives to Oxide: Nitride Selectivity 379 13.5 Effect of Slurry pH 385 13.6 Effect of Abrasive Particle Size on Removal Rate and Defectivity 388 13.7 Conclusion 395 14 Fabrication of Microdevices Using CMP 401 Gerfried Zwicker 14.1 Introduction 401 14.2 Microfabrication Processes 402 14.3 Microfabrication Products 403 14.4 CMP Requirements in Comparison with IC Fabrication 404 14.5 Examples of CMP Applications for Microfabrication 412 14.5.1 Case Study I: Integrated Pressure Sensor 416 14.5.2 Case Study II: Poly-Si Surface Micromachining and Angular Rate Sensor 417 14.5.3 Case Study III: Infrared Digital Micromirror Array 422 14.5.4 More Representative Applications 425 14.6 Outlook 426 15 Three-Dimensional (3D) Integration 431 J. Jay McMahon, Jian-Qiang Lu and Ronald J. Gutmann 15.1 Overview of 3D Technology 431 15.2 Factors Motivating Research in 3D 432 15.2.1 Small Form Factor 432 15.2.2 Heterogeneous Integration 433 15.2.3 Performance Enhancement 434 15.3 Approaches to 3D 435 15.3.1 Singulated Die 3D 435 15.3.2 Wafer-Level 3D 436 15.3.2.1 Wafer-Level 3D Using Oxide–Oxide Bonding 436 15.3.2.2 Wafer-Level 3D Using Copper–Copper Bonding 438 15.3.2.3 Wafer-Level 3D Using Adhesive Bonding 439 15.3.2.4 3D Integration Using Redistribution Layer Bonding 440 15.3.2.5 Summary of Wafer Level 3D Approaches 440 15.4 Wafer-Level 3D Unit Processes 442 15.4.1 Wafer-to-Wafer Alignment 442 15.4.2 Wafer-to-Wafer Bonding 444 15.4.2.1 Oxide–Oxide and Silicon–Oxide Wafer Bondings 444 15.4.2.2 Copper–Copper Wafer Bonding 444 15.4.2.3 Polymer Adhesive Wafer Bonding 446 15.4.3 Wafer Thinning for 3D 447 15.4.3.1 Timed Removal Thinning Approaches 448 15.4.3.2 Thinning to Either an Etch or Polish Stop 448 15.4.4 Through-Silicon Vias 449 15.5 Planarity Issues in 3D Integration 450 15.5.1 CMP Planarity Capabilities 451 15.5.1.1 Nano- and Microscale Planarization 451 15.5.1.2 Wafer-Scale Planarity 451 15.5.2 Planarity Issues for Various 3D Approaches 452 15.5.2.1 CMP for Via-Last Approach to 3D Using Oxide-to-Oxide Bonding 452 15.5.2.2 CMP for Via-Last Approach to 3D Using Polymer Adhesive Bonding 454 15.5.2.3 CMP for Via-First Approach to 3D Using Copper-to-Copper Bonding 455 15.5.2.4 CMP for Via-First 3D Using Redistribution Layer Bonding 455 15.6 Conclusions 456 16 Post-CMP Cleaning 467 Jin-Goo Park, Ahmed A. Busnaina and Yi-Koan Hong 16.1 Introduction 467 16.2 Types of Post-CMP Cleaning Processes 468 16.2.1 Wet Bath Type Cleaning 468 16.2.2 Single Wafer Cleanings 469 16.2.2.1 Immersion-Type Single-Wafer Post-CMP Cleaning System 469 16.2.2.2 Single-Wafer Spin Cleaner 469 16.2.2.3 Brush Cleaning 473 16.2.2.4 Drying 475 16.3 Post-CMP Cleaning Chemistry 477 16.3.1 Conventional Wet Cleanings 477 16.3.2 Chemicals Used in Post-CMP Cleaning and their Roles 478 16.3.2.1 NH4OH 478 16.3.2.2 HF 478 16.3.2.3 Organic Acids 479 16.3.2.4 Surfactants 479 16.4 Post-CMP Cleaning According to Applications 480 16.4.1 Post-Oxide CMP Cleaning 480 16.4.2 Post-W CMP Cleaning 481 16.4.3 Post-STI CMP Cleaning 481 16.4.4 Post-Poly-Si CMP Cleaning 482 16.4.5 Post-Cu/Low-k CMP Surface Cleaning 484 16.4.5.1 Corrosion 486 16.4.5.2 Organic Residue 487 16.4.5.3 Low-k Materials 489 16.4.5.4 Effect of Other Additives on Cleaning 491 16.5 Adhesion Force, Friction Force, and Defects During Cu CMP 492 16.5.1 Adhesion Force of Silica and Alumina on Cu 493 16.5.2 Friction Force in Cu CMP Process 494 16.5.3 Removal Rates of Cu Surface in Cu CMP 494 16.5.4 Surface Quality of Cu After Cu CMP Process 496 16.5.5 Correlation Among Friction, Adhesion Force, Removal Rate, and Surface Quality in Cu CMP 498 16.6 Case Study: Megasonic Post-CMP Cleaning of Thermal Oxide Wafers 499 16.6.1 Experimental Procedure 499 16.6.2 The Effect of Megasonic Input Power 500 16.6.3 The Effect of Temperature 503 16.6.4 The Effect of Etching on Cleaning 503 16.7 Summary 505 17 Defects Observed on the Wafer After the CMP Process 511 Paul Lefevre 17.1 Introduction 511 17.2 Defects After Oxide CMP 512 17.2.1 Introduction 512 17.2.2 Scratches 513 17.2.3 Color Variation—Oxide Thickness Variation 516 17.2.4 Slurry Residues and Organic Residues 518 17.2.5 Other Particles 519 17.2.6 Crystal Formation 519 17.2.7 Traces Elements 519 17.2.8 Radioactive Contamination 519 17.2.9 Defects Existing Before Oxide CMP 520 17.2.10 Source of Defect-Causing Large Particles 520 17.3 Defects After Polysilicon CMP 520 17.3.1 Introduction 520 17.3.2 Scratches 521 17.3.3 Polysilicon Residues 521 17.3.4 Particles 522 17.3.5 Residues 522 17.3.6 Trace Elements 522 17.3.7 Polysilicon Pitting and Voids 523 17.3.8 Discoloration at the Edge of the Structure or Edge of the Arrays 523 17.3.9 Defects Existing Before and Revealed After Polysilicon CMP 523 17.3.10 Influence of Processing Temperature 524 17.4 Defects After Tungsten CMP 524 17.4.1 Introduction 524 17.4.2 Corrosion, Pitting, and Void 524 17.4.3 Tungsten Recess and Rough Tungsten Surface 525 17.4.4 Scratches 528 17.4.5 Discoloration—Edge Overerosion (EOE) 529 17.4.6 Tungsten and Metal Liner Residues 530 17.4.7 Particles, Slurry Residues, and Trace Metal 531 17.4.8 Delamination 531 17.4.9 Preexisting Defects Revealed After Tungsten CMP 531 17.5 Defects After Copper CMP 532 17.5.1 Introduction and Summary on Copper CMP Defects 532 17.5.2 Copper Corrosion 533 17.5.3 Copper Pitting 535 17.5.4 Trenching at the Copper Line Edge 537 17.5.5 Rough Copper and Copper Recess 539 17.5.6 Discoloration—Metals Thickness Variations and/or Dielectric Thickness Variation 540 17.5.7 Copper Electromigration 542 17.5.8 Scratches 544 17.5.9 Metal Residues 544 17.5.10 Particles, Residues, and Trace Metals 547 17.5.11 Delamination 548 17.6 Defect Observation and Characterization Techniques 551 17.6.1 Optical Microscope 551 17.6.2 Scanning Electron Microscope 552 17.6.3 Energy Dispersive X-Ray Spectroscopy (EDX) 552 17.6.4 Scanning Auger Microscope (SAM) 553 17.6.5 Atomic Force Microscopy 553 17.7 Ensemble Defect Detection and Inspection Techniques 554 17.7.1 Optical Scan of Flat Film Blanket Wafers 554 17.7.2 Optical Scan of Patterned Wafers 554 17.7.3 Defect Classification 555 17.8 Consideration for the Future 555 18 CMP Slurry Metrology, Distribution, and Filtration 563 Rakesh K. Singh 18.1 Introduction 564 18.2 CMP Slurry Metrology and Characterization 567 18.2.1 Slurry Health Monitoring and Control 568 18.2.2 CMP Slurry Blend Control 569 18.2.2.1 Two-Component Blend Control 570 18.2.2.2 Three-Component Blend Control 572 18.2.3 CMP Slurry Characterization 573 18.2.4 Summary 576 18.3 CMP Slurry Blending and Distribution 577 18.3.1 Slurry Delivery Technologies 578 18.3.2 Continuous (On-Demand) Slurry Dispense and Metrology 578 18.3.3 Slurry Turnovers in Fab Distribution 580 18.3.4 Slurry Abrasive Settling and Dispersion 580 18.3.4.1 Slurry Settling Rate Quantification 580 18.3.4.2 Settling Behavior of Different Abrasive CMP Slurries 581 18.3.4.3 Required Minimum Flow Velocity for CMP Slurries 584 18.3.5 Summary 585 18.4 CMP Slurry Filtration 586 18.4.1 Slurry Filtration Methodology 587 18.4.2 Filter Design Consideration 588 18.4.3 Slurry Filter Characterization 591 18.4.4 CMP Process and Consumable Trends and Challenges 592 18.4.5 Slurry Filtration-Case Studies 595 18.4.5.1 Silica Dispersion Single-Pass High-Retention Filtration 595 18.4.5.2 Silica Slurry POU and Recirculation 596 18.4.5.3 Silica Ceria and Alumina Slurry Tighter Filtration 599 18.4.5.4 Polystyrene Latex (PSL) Bead Solution Filtration 602 18.4.6 Summary 602 18.5 Pump Handling Effects on CMP Slurry Filtration—Case Studies 603 18.5.1 Pump Technologies and Applications 604 18.5.2 Pump Shearing Effects on Slurry Abrasives 605 18.5.3 Pump Handling and Filtration Data 606 18.5.4 Test Cases 607 18.5.5 Summary 620 19 The Facilities Side of CMP 627 John H. Rydzewski 19.1 Introduction 627 19.2 Characterization of the CMP Waste Stream 628 19.3 Materials of Compatibility 629 19.4 Collection System Methodologies 631 19.5 Treatment System Components 632 19.5.1 Collection Tank and pH Adjustment 632 19.5.2 Oxidizer Removal 633 19.5.3 Organics Removal 635 19.5.4 Treatment of Suspended Solids 635 19.5.5 Removal of Trace Metals 638 19.6 Integration of Components—Putting It All Together 644 19.6.1 Solids Treatment Before Metals Removal 644 19.6.2 Solids Treatment After Metals Removal 645 19.6.3 No Solids Removal 646 19.7 Conclusions 647 20 CMP—The Next Fifteen Years 651 Joseph M. Steigerwald 20.1 The Past 15 Years 651 20.2 Challenges to Silicon IC Manufacturing 655 20.3 New CMP Processes 661 20.3.1 The Two-Year Development Cycle 661 20.3.2 Finfet Transistors 664 20.3.3 High-k Gate Oxides 665 20.3.4 Other Examples 670 20.4 CMP Challenges 673 20.4.1 Development Time of New CMP Materials 673 20.4.2 CMP Defect Reduction 675 20.4.3 CMP Process Control 677 20.4.3.1 CMP Film Thickness Control 678 20.4.3.2 Process Control Systems, Consumables Material Control, and Excursion Prevention 680 20.4.4 Cost of CMP 683 20.5 Summary 683 21 Utilitarian Information for CMP Scientists and Engineers 687 Yongqing Lan and Yuzhuo Li 21.1 Physical and Chemical Properties of Abrasive Particles 687 21.2 Physical and Chemical Properties on Oxidizers 690 21.3 Physical and Chemical Properties on Relevant Surfactants 690 21.3.1 Classification of Surfactants 690 21.3.2 Critical Micellar Concentration 692 21.3.3 Ternary Phase Diagrams Involving Surfactants 693 21.4 Relevant Pourbaix Diagram 696 21.5 Commonly Used Buffering Systems 703 21.6 Useful Web Sites 704 Index 725

About the Author :
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.