Microelectronic Applications of Chemical Mechanical Planarization

An authoritative, systematic, and comprehensive description of current CMP technology Chemical Mechanical Planarization (CMP) provides the greatest degree of planarization of any known technique. The current standard for integrated circuit (IC) planarization, CMP is playing an increasingly important role in other related applications such as microelectromechanical systems (MEMS) and computer hard drive manufacturing. This reference focuses on the chemical aspects of the technology and includes contributions from the foremost experts on specific applications. After a detailed overview of the fundamentals and basic science of CMP, Microelectronic Applications of Chemical Mechanical Planarization: • Provides in-depth coverage of a wide range of state-of-the-art technologies and applications • Presents information on new designs, capabilities, and emerging technologies, including topics like CMP with nanomaterials and 3D chips • Discusses different types of CMP tools, pads for IC CMP, modeling, and the applicability of tribometrology to various aspects of CMP • Covers nanotopography, CMP performance and defect profiles, CMP waste treatment, and the chemistry and colloidal properties of the slurries used in CMP • Provides a perspective on the opportunities and challenges of the next fifteen years Complete with case studies, this is a valuable, hands-on resource for professionals, including process engineers, equipment engineers, formulation chemists, IC manufacturers, and others. With systematic organization and questions at the end of each chapter to facilitate learning, it is an ideal introduction to CMP and an excellent text for students in advanced graduate courses that cover CMP or related semiconductor manufacturing processes. MICROELECTRONIC APPLICATIONS OF CHEMICAL MECHANICAL PLANARIZATION......Page 3 CONTENTS......Page 7 Foreword......Page 21 Contributing Authors......Page 25 1.1 Introduction......Page 29 1.2.1 Multilevel Metallization and the Need for Planarization......Page 30 1.2.2 Degrees of Planarization......Page 32 1.2.3 Methods of Planarization......Page 33 1.2.4 Chemical and Mechanical Planarization of Dielectric Films......Page 35 1.2.5 Preparation of Planar Thin Films for Non-IC Applications Using CMP......Page 36 1.3.1 RC Delay and New Interconnect Materials......Page 37 1.3.2 Damascene and Dual Damascene......Page 40 1.3.3 Tungsten CMP......Page 43 1.3.4 STI......Page 44 1.4 CMP to Correct Defects......Page 47 1.5 Advantages and Disadvantages of CMP......Page 48 1.6 Conclusion......Page 49 2.1 Introduction......Page 53 2.2 Historic Prospective and Future Trends......Page 55 2.3 CMP Material Characterization......Page 60 2.3.1 Thermal Effects......Page 61 2.3.2 Slurry Rheology Studies......Page 63 2.3.3 Slurry–Pad Interactions......Page 66 2.3.4 Pad Groove Effects......Page 70 2.3.5 Pad–Wafer Contact and Slarry Transport: Dual Emission Laser Induced Fluorescence......Page 71 2.3.6 Dynamic Nuclear Magnetic Resonance......Page 73 2.3.7 CMP Slurry Stability and Correlation with Defectivity......Page 77 2.4 Conclusions......Page 79 3.1 CMP Operation and Characteristics......Page 85 3.2 Description of the CMP Process......Page 87 3.3.1 CMP System......Page 88 3.3.2 Brief History of CMP Systems......Page 89 3.3.4 Polisher......Page 90 3.3.5 Cleaning Module in a Dry-in/Dry-out System......Page 92 3.4.2 Carrier......Page 93 3.4.3 Profile Control by Carriers......Page 96 3.4.4 Dressers......Page 97 3.5.2 Representative Monitors......Page 100 3.5.4 Communication......Page 103 3.6 Conclusions......Page 106 4.1 Introduction......Page 109 4.2 Tribometrology of CMP......Page 110 4.3.1 Process Parameters During CMP......Page 113 4.3.2 Polishing Pad Characteristics......Page 116 4.3.3 Slurry Characteristics......Page 118 4.4.1 PadProbeTM......Page 120 4.4.2 Effect of Temperature......Page 128 4.5 Conditioner Design......Page 130 4.6.1 Slurry Testing......Page 133 4.6.2 Pad Testing......Page 136 4.6.3 Retaining Rings......Page 138 4.7.1 Coefficient of Friction and Acoustic Emission Signal......Page 141 4.7.2 Advanced Signal Processing......Page 142 4.8 Summary......Page 145 5.1 Introduction......Page 151 5.2.1 Pad Types......Page 152 5.2.2 Pad Microstructures and Macrostructures......Page 153 5.2.3.1 Hardness, Young’s Modulus, and Strength......Page 155 5.2.3.3 Pad Thickness......Page 156 5.2.4 Effects of Pad Property on Polishing Performance......Page 157 5.2.4.1 Pad Roughness Effects......Page 158 5.2.4.2 Pad Porosity/Density Effects......Page 159 5.2.4.3 Pad Hardness, Young’s Modulus, Stiffness, and Thickness Effects......Page 164 5.2.4.4 Pad Groove Effects......Page 166 5.3.2 Polyurethane Property Control by Chemical Components......Page 168 5.3.3 Chemical Effects on Polishing Performance......Page 169 5.4 Pad Conditioning and Its Effect on CMP Performance......Page 170 5.5.1 Review of Modeling of Pad Effects on Polishing Performance......Page 173 5.5.2.1 Pads and Pressure......Page 176 5.5.2.2 Pads and Abrasives......Page 178 5.5.2.3 Pads, Dishing, and Erosion......Page 182 5.6.1 Particle-Containing Pads......Page 187 5.6.2 Surface-Treated Pads......Page 190 5.6.3 Reactive Pad......Page 192 6.1 Introduction......Page 199 6.2 A Two-Step Chemical Mechanical Material Removal Model......Page 200 6.3 Pad Surfaces and Pad Surface Contact Modeling......Page 203 6.4 Reaction Temperature......Page 206 6.5 A Polishing Example......Page 213 6.6 Topography Planarization......Page 217 7.1 Introduction......Page 229 7.2.1 Nitric Acid......Page 230 7.2.2 Hydrogen Peroxide......Page 231 7.2.3 Ferric Nitrate......Page 238 7.2.4 Potassium Permanganate, Dichromates, and Iodate......Page 240 7.3 Chelating Agents......Page 242 7.3.1 Ammonia......Page 243 7.3.2 Amino Acids......Page 244 7.3.3 Organic Acids......Page 245 7.3.4 Thermodynamic Consideration and Quantitative Description......Page 246 7.4.1 Structures and Physical Properties of Surfactants......Page 247 7.4.2 Dispersion of Particles......Page 249 7.4.3 Surface Modification of Wafer Surface......Page 250 7.5.1 Hardness......Page 253 7.5.3 Particle Crystallinity and Shapes......Page 255 7.5.4 Particle Size and Oversized Particle Count......Page 256 7.5.5 Particle Preparation......Page 258 7.5.6 Surface Properties......Page 259 7.6 Particle Surface Modification......Page 261 7.7 Soft Particles......Page 262 7.8.2 Material Removal Rate and Selectivity......Page 263 7.9 Conclusions......Page 267 8 Corrosion Inhibitor for Cu CMP Slurry......Page 277 8.1 Thermodynamic Considerations of Copper Surface......Page 278 8.2 Types of Passivating Films on Copper Surface Under Oxdizing Conditions......Page 280 8.3 Effect of pH on BTA in Glycine-Hydrogen Peroxide Based Cu CMP Slurry......Page 285 8.4 Evaluation of Potential BTA Alternatives for Acidic Cu CMP Slurry......Page 287 8.5 Electrochemical Polarization Study of Corrosion Inhibitors in Cu CMP Slurry......Page 291 8.6 Hydrophobicity of the Surface Passivation Film......Page 293 8.7 Competitive Surface Adsorption Behavior of Corrosion Inhibitors......Page 294 8.8 Summary......Page 298 9.1 Introduction......Page 305 9.2.1 Basic Applications of Tungsten CMP......Page 306 9.2.2 Basic W CMP Requirements and Procedures......Page 309 9.3 W CMP Defects......Page 310 9.4.1 Basic Considerations......Page 313 9.4.3 Oxide Buffing......Page 317 9.5.1 W CMP Process Controls......Page 318 9.5.2 Platen Temperature Control......Page 319 9.6 Conclusions......Page 320 10.1 Introduction......Page 323 10.2.1 Electrode/Electrolyte Interface......Page 325 10.2.2 Electrochemical Reaction......Page 326 10.2.3 Mass Transport......Page 327 10.2.4 Anodic Polarization Curve and Conditions for Electrochemical Planarization......Page 328 10.3.1 Ohmic Leveling......Page 332 10.3.2 Diffusion Leveling......Page 333 10.3.3 Migration Leveling......Page 335 10.4.1 Impedance Measurement......Page 337 10.4.2 Electrochemical Impedance Spectroscopy......Page 338 10.4.3 Ellipsometry......Page 339 10.5 Modified Electrochemical Polishing Approaches......Page 340 11.1 Introduction......Page 347 11.2 CMP......Page 349 11.3 ECP......Page 350 11.4 ECMP......Page 354 11.5 Full Sequence Electrochemical–Mechanical Planarization......Page 362 11.6 Conclusions......Page 368 12.1 Introduction......Page 373 12.2 LOCOS to STI......Page 374 12.3 Shallow Trench Isolation......Page 377 12.4 The Planarization Step in Detail......Page 379 12.5 Optimization Techniques......Page 386 12.5.2 Patterned Oxide Etch Back......Page 387 12.5.3 Nitride Overcoat......Page 388 12.5.4 EXTIGATE......Page 389 12.5.6 Polysilicon-Filled Trenches......Page 391 12.6 Outlook......Page 392 13.1 Introduction......Page 397 13.2 Representative Testing Wafers for STI Process and Consumable Evaluations......Page 399 13.3 Effects of Abrasive Types on STI Slurry Performance......Page 401 13.4 Effects of Chemical Additives to Oxide: Nitride Selectivity......Page 407 13.5 Effect of Slurry pH......Page 413 13.6 Effect of Abrasive Particle Size on Removal Rate and Defectivity......Page 416 13.7 Conclusion......Page 423 14.1 Introduction......Page 429 14.2 Microfabrication Processes......Page 430 14.3 Microfabrication Products......Page 431 14.4 CMP Requirements in Comparison with IC Fabrication......Page 432 14.5 Examples of CMP Applications for Microfabrication......Page 440 14.5.1 Case Study I: Integrated Pressure Sensor......Page 444 14.5.2 Case Study II: Poly-Si Surface Micromachining and Angular Rate Sensor......Page 445 14.5.3 Case Study III: Infrared Digital Micromirror Array......Page 450 14.5.4 More Representative Applications......Page 453 14.6 Outlook......Page 454 15.1 Overview of 3D Technology......Page 459 15.2.1 Small Form Factor......Page 460 15.2.2 Heterogeneous Integration......Page 461 15.2.3 Performance Enhancement......Page 462 15.3.1 Singulated Die 3D......Page 463 15.3.2.1 Wafer-Level 3D Using Oxide–Oxide Bonding......Page 464 15.3.2.2 Wafer-Level 3D Using Copper–Copper Bonding......Page 466 15.3.2.3 Wafer-Level 3D Using Adhesive Bonding......Page 467 15.3.2.5 Summary of Wafer Level 3D Approaches......Page 468 15.4.1 Wafer-to-Wafer Alignment......Page 470 15.4.2.2 Copper–Copper Wafer Bonding......Page 472 15.4.2.3 Polymer Adhesive Wafer Bonding......Page 474 15.4.3 Wafer Thinning for 3D......Page 475 15.4.3.2 Thinning to Either an Etch or Polish Stop......Page 476 15.4.4 Through-Silicon Vias......Page 477 15.5 Planarity Issues in 3D Integration......Page 478 15.5.1.2 Wafer-Scale Planarity......Page 479 15.5.2.1 CMP for Via-Last Approach to 3D Using Oxide-to-Oxide Bonding......Page 480 15.5.2.2 CMP for Via-Last Approach to 3D Using Polymer Adhesive Bonding......Page 482 15.5.2.4 CMP for Via-First 3D Using Redistribution Layer Bonding......Page 483 15.6 Conclusions......Page 484 16.1 Introduction......Page 495 16.2.1 Wet Bath Type Cleaning......Page 496 16.2.2.2 Single-Wafer Spin Cleaner......Page 497 16.2.2.3 Brush Cleaning......Page 501 16.2.2.4 Drying......Page 503 16.3.1 Conventional Wet Cleanings......Page 505 16.3.2.2 HF......Page 506 16.3.2.4 Surfactants......Page 507 16.4.1 Post-Oxide CMP Cleaning......Page 508 16.4.3 Post-STI CMP Cleaning......Page 509 16.4.4 Post-Poly-Si CMP Cleaning......Page 510 16.4.5 Post-Cu/Low-k CMP Surface Cleaning......Page 512 16.4.5.1 Corrosion......Page 514 16.4.5.2 Organic Residue......Page 515 16.4.5.3 Low-k Materials......Page 517 16.4.5.4 Effect of Other Additives on Cleaning......Page 519 16.5 Adhesion Force, Friction Force, and Defects During Cu CMP......Page 520 16.5.1 Adhesion Force of Silica and Alumina on Cu......Page 521 16.5.3 Removal Rates of Cu Surface in Cu CMP......Page 522 16.5.4 Surface Quality of Cu After Cu CMP Process......Page 524 16.5.5 Correlation Among Friction, Adhesion Force, Removal Rate, and Surface Quality in Cu CMP......Page 526 16.6.1 Experimental Procedure......Page 527 16.6.2 The Effect of Megasonic Input Power......Page 528 16.6.4 The Effect of Etching on Cleaning......Page 531 16.7 Summary......Page 533 17.1 Introduction......Page 539 17.2.1 Introduction......Page 540 17.2.2 Scratches......Page 541 17.2.3 Color Variation—Oxide Thickness Variation......Page 544 17.2.4 Slurry Residues and Organic Residues......Page 546 17.2.8 Radioactive Contamination......Page 547 17.3.1 Introduction......Page 548 17.3.3 Polysilicon Residues......Page 549 17.3.6 Trace Elements......Page 550 17.3.9 Defects Existing Before and Revealed After Polysilicon CMP......Page 551 17.4.2 Corrosion, Pitting, and Void......Page 552 17.4.3 Tungsten Recess and Rough Tungsten Surface......Page 553 17.4.4 Scratches......Page 556 17.4.5 Discoloration—Edge Overerosion (EOE)......Page 557 17.4.6 Tungsten and Metal Liner Residues......Page 558 17.4.9 Preexisting Defects Revealed After Tungsten CMP......Page 559 17.5.1 Introduction and Summary on Copper CMP Defects......Page 560 17.5.2 Copper Corrosion......Page 561 17.5.3 Copper Pitting......Page 563 17.5.4 Trenching at the Copper Line Edge......Page 565 17.5.5 Rough Copper and Copper Recess......Page 567 17.5.6 Discoloration—Metals Thickness Variations and/or Dielectric Thickness Variation......Page 568 17.5.7 Copper Electromigration......Page 570 17.5.9 Metal Residues......Page 572 17.5.10 Particles, Residues, and Trace Metals......Page 575 17.5.11 Delamination......Page 576 17.6.1 Optical Microscope......Page 579 17.6.3 Energy Dispersive X-Ray Spectroscopy (EDX)......Page 580 17.6.5 Atomic Force Microscopy......Page 581 17.7.2 Optical Scan of Patterned Wafers......Page 582 17.8 Consideration for the Future......Page 583 18 CMP Slurry Metrology, Distribution, and Filtration......Page 591 18.1 Introduction......Page 592 18.2 CMP Slurry Metrology and Characterization......Page 595 18.2.1 Slurry Health Monitoring and Control......Page 596 18.2.2 CMP Slurry Blend Control......Page 597 18.2.2.1 Two-Component Blend Control......Page 598 18.2.2.2 Three-Component Blend Control......Page 600 18.2.3 CMP Slurry Characterization......Page 601 18.2.4 Summary......Page 604 18.3 CMP Slurry Blending and Distribution......Page 605 18.3.2 Continuous (On-Demand) Slurry Dispense and Metrology......Page 606 18.3.4.1 Slurry Settling Rate Quantification......Page 608 18.3.4.2 Settling Behavior of Different Abrasive CMP Slurries......Page 609 18.3.4.3 Required Minimum Flow Velocity for CMP Slurries......Page 612 18.3.5 Summary......Page 613 18.4 CMP Slurry Filtration......Page 614 18.4.1 Slurry Filtration Methodology......Page 615 18.4.2 Filter Design Consideration......Page 616 18.4.3 Slurry Filter Characterization......Page 619 18.4.4 CMP Process and Consumable Trends and Challenges......Page 620 18.4.5.1 Silica Dispersion Single-Pass High-Retention Filtration......Page 623 18.4.5.2 Silica Slurry POU and Recirculation......Page 624 18.4.5.3 Silica, Ceria, and Alumina Slurry Tighter Filtration......Page 627 18.4.6 Summary......Page 630 18.5 Pump Handling Effects on CMP Slurry Filtration—Case Studies......Page 631 18.5.1 Pump Technologies and Applications......Page 632 18.5.2 Pump Shearing Effects on Slurry Abrasives......Page 633 18.5.3 Pump Handling and Filtration Data......Page 634 18.5.4 Test Cases......Page 635 18.5.5 Summary......Page 648 19.1 Introduction......Page 655 19.2 Characterization of the CMP Waste Stream......Page 656 19.3 Materials of Compatibility......Page 657 19.4 Collection System Methodologies......Page 659 19.5.1 Collection Tank and pH Adjustment......Page 660 19.5.2 Oxidizer Removal......Page 661 19.5.4 Treatment of Suspended Solids......Page 663 19.5.5 Removal of Trace Metals......Page 666 19.6.1 Solids Treatment Before Metals Removal......Page 672 19.6.2 Solids Treatment After Metals Removal......Page 673 19.6.3 No Solids Removal......Page 674 19.7 Conclusions......Page 675 20.1 The Past 15 Years......Page 679 20.2 Challenges to Silicon IC Manufacturing......Page 683 20.3.1 The Two-Year Development Cycle......Page 689 20.3.2 Finfet Transistors......Page 692 20.3.3 High-k Gate Oxides......Page 693 20.3.4 Other Examples......Page 698 20.4.1 Development Time of New CMP Materials......Page 701 20.4.2 CMP Defect Reduction......Page 703 20.4.3 CMP Process Control......Page 705 20.4.3.1 CMP Film Thickness Control......Page 706 20.4.3.2 Process Control Systems, Consumables Material Control, and Excursion Prevention......Page 708 20.5 Summary......Page 711 21.1 Physical and Chemical Properties of Abrasive Particles......Page 715 21.3.1 Classification of Surfactants......Page 718 21.3.2 Critical Micellar Concentration......Page 720 21.3.3 Ternary Phase Diagrams Involving Surfactants......Page 721 21.4 Relevant Pourbaix Diagram......Page 724 21.5 Commonly Used Buffering Systems......Page 731 21.6 Useful Web Sites......Page 732 Index......Page 753 13 Consumables for Advanced Shallow Trench Isolation (STI)14 Fabrication of Microdevices Using CMP; 15 Three-Dimensional (3D) Integration; 16 Post-CMP Cleaning; 17 Defects Observed on the Wafer After the CMP Process; 18 CMP Slurry Metrology, Distribution, and Filtration; 19 The Facilities Side of CMP; 20 CMP--The Next Fifteen Years; 21 Utilitarian Information for CMP Scientists and Engineers; Index