Book Description
Editorial Review
Dr. Bakshi has compiled a thorough, clear reference text covering the important fields of EUV lithography for high-volume manufacturing. This book has resulted from his many years of experience in EUVL development and from teaching this subject to future specialists. The book proceeds from an historical perspective of EUV lithography, through source technology, optics, projection system design, mask, resist, and patterning performance, to cost of ownership. Each section contains worked examples, a comprehensive review of challenges, and relevant citations for those who wish to further investigate the subject matter. Dr. Bakshi succeeds in presenting sometimes unfamiliar material in a very clear manner. This book is also valuable as a teaching tool. It has become an instant classic and far surpasses others in the EUVL field. --Dr. Akira Endo, Chief Development Manager, Gigaphoton Inc.
Description
Extreme ultraviolet lithography (EUVL) is the principal lithography technology aiming to manufacture computer chips beyond the current 193-nm-based optical lithography, and recent progress has been made on several fronts: EUV light sources, optics, optics metrology, contamination control, masks and mask handling, and resists.
This comprehensive volume is comprised of contributions from the world's leading EUVL researchers and provides all of the critical information needed by practitioners and those wanting an introduction to the field.
Interest in EUVL technology continues to increase, and this volume provides the foundation required for understanding and applying this exciting technology.
About the editor of EUV Lithography
Dr. Vivek Bakshi previously served as a senior member of the technical staff at SEMATECH; he is now president of EUV Litho, Inc., in Austin, Texas.
Book Details
Date Published: 11 December 2008
Pages: 702
Volume: PM178
Pages: 702
Volume: PM178
Table of Contents
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Preface
Introduction
Chapter 1: EUV Lithography: A Historical Perspective
- 1.1 Introduction
- 1.2 The Early Stage of Development—1981 to 1992
- 1.3 The Second Stage of Development—1993 to 1996
- 1.3.1 Two-Mirror Imaging System Development
- 1.3.2 Three-Mirror Imaging System Development
- 1.3.3 MOS Device Demonstration Using EUVL
- 1.4 Other Developments in Japan and Europe
- 1.5 The Development of Individual Technologies
- 1.5.1 Selection of the Exposure Wavelength
- 1.5.2 Design of Reflective Imaging Systems
- 1.5.3 Fabrication and Evaluation of Aspherical Mirrors
- 1.5.4 Multilayer Coatings and Reflection Masks
- 1.5.5 EUV Resist Development
- 1.5.6 EUV Light Source Development
- 1.6 EUVL Conferences
- 1.7 Summary
- 1.8 Acknowledgements
- 1.9 References
Chapter 2: EUV LLC: A Historical Perspective
- 2.1 Introduction
- 2.1.1 Background
- 2.1.2 Need for a Revolutionary Approach
- 2.2 Formation of the LLC
- 2.2.1 Vision
- 2.2.2 Implementation
- 2.2.3 Organizational Structure
- 2.3 Program Structure 2
- 2.3.1 Organization
- 2.3.2 Risk Management
- 2.3.3 Reporting
- 2.3.4 Documentation
- 2.4 Program Results
- 2.4.1 Technical accomplishments
- 2.4.2 IP Portfolio
- 2.4.3 Program Statistics
- 2.4.4 Delays
- 2.5 Retrospective observations
- 2.5.1 Improvements
- 2.5.2 External Issues
- 2.5.3 Benefits
- 2.6 Status of EUV Development at the end of LLC 2
- 2.6.1 Risk Reduction
- 2.6.2 Industry involvement
- 2.7 Summary
- 2.8 Acknowledgements
- 2.9 Appendix A - Major Accomplishments
- 2.10 Appendix B - Patents
- 2.11 References
Chapter 3: EUV Source Technology
- 3.1 Introduction
- 3.2 EUV Source Requirements
- 3.2.1 Definition of EUV Source
- 3.2.2 Joint Specifications
- 3.2.3 Throughput Model
- 3.3 DPP and LPP Source Technologies
- 3.3.1 Discharge-Produced Plasma (DPP)
- 3.3.2 Laser-Produced Plasma (LPP)
- 3.4 EUV Source Performance
- 3.4.1 Conversion Efficiency of EUV Sources
- 3.4.2 EUV Source Performance Results
- 3.4.3 Source Components and Their Lifetimes
- 3.5 Summary and Future Outlook
- References
Chapter 4A: Optics and Multilayer Coatings for EUVL Systems
- 4A.1 Introduction
- 4A.2 Properties of EUVL Systems
Chapter 4B: Projection Systems for Extreme Ultraviolet Lithography
- 4B.1 General EUVL Optical Design Considerations
- 4B.2 EUV Microsteppers
- 4B.2.1 "10X" Microstepper
- 4B.2.2 Microexposure Tool (MET)
- 4B.3 Engineering Test Stand (ETS)
- 4B.4 Six-Mirror EUVL Projection Systems
- 4B.4.1 Feasibility
- 4B.4.2 Concepts with Concave/Primary Mirrors
- 4B.4.2 Concepts with Convex Primary Mirrors
- Acknowledgements
- References
Chapter 4C: Specification, Fabrication, Testing, and Mounting of EUVL Optical Substrates
- 4C.1 Introduction
- 4C.2 Specification
- 4C.3 Projection Optics
- 4C.4 Effect of Substrate Errors on Imaging Performance
- 4C.5 Low-Frequency (Figure) Errors
- 4C.7 High-Spatial-Frequency Errors
- 4C.8 Influence of Coatings on Roughness Specification
- 4C.9 Calculation of Surface Errors
- 4C.10 Uniformity
- 4C.11 Substrate Materials
- 4C.12 Fabrication
- 4C.13 Metrology
- 4C.14 Mounting and Assembly
- 4C.15 Alignment
- 4C.16 Condenser Optics
- Acknowledgements
- References
Chapter 4D: Multilayer Coatings for EUVL
- 4D.1 Overview and History of EUV Multilayer Coatings
- 4D.2 Choice of ML Materials and Wavelength Considerations
- 4D.3 Multilayer Deposition Technologies
- 4D.4 Theoretical Design
- 4D.5 High Reflectivity, Low Stress, and Thermal Stability Considerations
- 4D.6 Optical Constants
- 4D.7 Multilayer Thickness Specifications for Imaging and Condenser EUVL Mirrors
- Acknowledgements
- References
Chapter 5: EUV Optical Testing
- 5.1 Introduction
- 5.2 Target Accuracy
- 5.3 Techniques for Angstrom-scale EUV Wavefront Measurement Accuracy
- 5.3.1 Spherical-Wave Illumination
- 5.3.2 Basic Testing Requirements
- 5.3.3 Knife-Edge Test
- 5.3.4 Point-Diffraction Interferometer
- 5.3.5 Phase-Shifting Point-Diffraction Interferometer
- 5.3.6 Shearing Interferometery
- 5.3.7 Hartmann Wavefront Sensor
- 5.3.8 EUV Interferometry Examples
- 5.3.9 Aerial Image Monitors
- 5.3.10 Calibration Techniques
- 5.4 Intercomparison
- 5.4.1 Visible-Light and EUV Interferometry
- 5.5 Future Directions
- 5.5.1 At-Wavelength Optical Testing in Commercial Lithography Applications
- 5.5.2 EUV Optical Testing in Other Areas
- References
Chapter 6A: Optics Contamination
- 6A.1 Introduction
- 6A.1.2 Survey of Recent Lifetime Results
- 6A.2 Fundamentals of Optics Contamination
- 6A.2.1 Causes of Projection Optics Contamination
- 6A.2.2 Theoretical Models of Optics Contamination
- 6A.3 Optics Contamination Control
- 6A.3.1 Measurements of Optics Lifetime
- 6A.3.2 Measurement of Optics Contamination (In-Situ Metrology)
- 6A.3.3 Environmental Control Strategy
- 6A.3.4 Development of Contamination-Resistant Capping Layers
- 6A.3.5 Cleaning of Optics Contamination
- 6A.3.6 Novel Approaches to Contamination Control
- 6A.4 Summary and Future Outlook
- References
Chapter 6B: Grazing Angle Collector Contamination
- 6B.1 Introduction
- 6B.1.1 EUV Lithography Challenges
- 6B.1.2 EUV Sources
- 6B.1.3 EUV Collector Optics
- 6B.2 Collector Lifetime Status and Challenges
- 6B.2.1 Mechanism of Reflectivity Degradation
- 6B.2.2 Erosion and Deposition: A Binary Collision Approximation Study of Sn Interaction with Ru Surfaces
- 6B.2.3 Sn Chemical Removal
- 6B.3 Summary
- Acknowledgements
- References
Chapter 6C: Collector Contamination: Normal Incidence (Multilayer) Collectors
- 6C.1 Introduction
- 6C.2 Overview of Normal-Incidence Collector Mirrors
- 6C.3 Collector Performance
- 6C.3.1 Erosion by Fast Ions and Lifetime Calculation
- 6C.3.2 Contamination and Optics Cleaning
- 6C.3.3 Thermal Load and Layer Intermixing
- 6C.4 Summary
- Acknowledgements
- References
Chapter 7: EUV Mask and Mask Metrology
- 7.1 Introduction
- 7.2 EUV Mask Structure and Process Flow
- 7.3 Mask Substrate
- 7.3.1 Mechanical Property Requirements
- 7.3.2 Surface Figure Requirement
- 7.3.3 Defect Requirements
- 7.4 Mask Blank Fabrication
- 7.4.1 Multilayer Deposition Process
- 7.4.2 Multilayer Characterization
- 7.4.3 Multilayer Performance Improvement Techniques and Defect Mitigation
- 7.4.4 Multilayer Defect Inspection
- 7.4.5 Multilayer Defect Repair
- 7.4.6 Multilayer Defect Compensation
- 7.5 Absorber Stack and Backside Conductive Coating
- 7.5.1 Absorber Layer
- 7.5.2 Buffer Layer
- 7.5.3 Antireflection Coating
- 7.5.4 Shadowing Effect
- 7.5.5 Bossung Curve Assymetry and Focus Shift
- 7.5.6 Backside Conductive Coating and Mask Handling
- 7.6 Mask Patterning
- 7.6.1 E-Beam Writing
- 7.6.2 Absorber Stack Etch
- 7.6.3 Absorber Defect Inspection
- 7.6.4 Absorber Defect Repair
- 7.6.5 Buffer Layer Etch
- 7.6.6 Buffer Layer Defect Inspection and Repair
- 7.7 Mask Cleaning
- 7.8 Advanced Mask Structure
- 7.8.1 Etched Binary Mask
- 7.8.2 Attenuated Phase Shift Mask
- 7.8.3 Alternating Phase Shift Mask
- 7.8.4 Modified Alternating Phase Shift Mask
- 7.9 Summary and Future Outlook
- Acknowledgements
- References
Chapter 8: Photoresists for Extreme Ultraviolet Lithography
- 8.1 Introduction
- 8.2 Earliest EUV Resist Imaging
- 8.3 Absorption Coefficients of EUV Photoresists
- 8.3.1 Absorption Coefficient Definitions
- 8.3.2 Absorption Cross-Sections of the Elements
- 8.3.3 Methods for Determining EUV Absorbance
- 8.4 Multilayer Resists and Pattern Transfer
- 8.4.1 Multilayer Resist Approaches
- 8.4.2 Defects in Ultrathin Resist Films
- 8.4.3 Pattern Transfer of UTR into Hard Masks
- 8.4.4 Integration of UTRs into Integrated Circuit Manufacturing Processes
- 8.5 Resist Types
- 8.5.1 Environmentally Stable Chemically Amplified Photoresists (ESCAP)
- 8.5.2 KRS Photoresists
- 8.5.3 PMMA
- 8.5.4 Negative Resists
- 8.5.5 Resists with Silicon or Boron
- 8.6 PAGs and Acids
- 8.6.1 Acid Diffusion
- 8.6.2 New PAGs for EUV
- 8.6.3 Exposure Mechanisms
- 8.7 Line Edge Roughness
- 8.7.1 Added Base
- 8.7.2 Polymer Size
- 8.7.3 Shot Noise
- 8.7.4 Film Quantum Yield
- 8.8 Summary and Future Outlook
- Acknowledgements
- Notes and References
Chapter 9: High-Resolution EUV Imaging Tools for Resist Exposure and Aerial Image Monitoring
- 9.1 Introduction
- 9.2 EUV Tool Design Considerations
- 9.3 EUV Microstepper
- 9.3.1 MS-13 Tool Concept
- 9.3.2 EUV Source
- 9.3.3 EUV Optics
- 9.3.4 Tool Subsystems
- 9.3.5 Tool Subsystems testing
- 9.4 Reticle Imaging Microscope
- 9.4.1 RIM-13 Tool Architecture
- 9.4.2 EUV Source
- 9.4.3 EUV Illumination
- 9.4.4 Reticle Imaging
- 9.4.5 EUV Microscope
- 9.4.6 Visible Microscope
- 9.4.7 Tool Subsystems
- 9.4.8 EUV Reticle Aerial Image Capture Results
- 9.4.9 Software
- 9.5 Summary and Future Outlook
- Acknowledgments
- References
Chapter 10: Fundamentals of the EUVL Scanner
- 10.1 Introduction
- 10.2 Illumination Optics
- 10.2.1 Illumination Optics Design
- 10.2.2 Source Requirements
- 10.2.3 Thermal Loading of Illuminator
- 10.3 Projection Optics
- 10.3.1 Numerical Aperture
- 10.3.2 Magnification and Field Size
- 10.4 Stages
- 10.4.1 Reticle Stage and Wafer Stage
- 10.4.2 Reticle Chuck
- 10.4.3 Wafer Chuck
- 10.5 Sensors
- 10.5.1 Reticle Focus Sensor
- 10.5.2 Wafer Focus Sensor
- 10.5.3 Wafer Alignment Sensor
- 10.5.4 Aerial Image Sensor
- 10.5.5 Dose Sensor
- 10.6 Handling Systems
- 10.6.1 Reticle Handling System
- 10.6.2 Wafer Handling System
- 10.7 Vacuum and Environment System
- 10.8 Budgets
- 10.8.1 Overlay Budget
- 10.8.2 Focus Budget
- 10.8.3 Wafer Throughput Budget
- 10.9 Summary
- Acknowledgements
- References
Chapter 11: EUVL System Patterning Performance
- 11.1 Introduction: The Benefits of EUV Imaging
- 11.2 Imaging with the 0.1-NA ETS Optic
- 11.2.1 Static Imaging Characterization of the 0.1-NA ETS Optic
- 11.2.2 Low-k1 Printing With Modified Illumination
- 11.2.3 Determining the Impact of Limited Resist Resolution
- 11.2.4 Early Demonstration of Chromeless Phase-Shift-Mask Printing in the EUV Range
- 11.2.5 Buried Programmed Defect Printability Study
- 11.3 Imaging with the 0.3-NA MET Optic
- 11.3.1 Predicted Performance
- 11.3.2 Demonstrating Resist-Limited Performance
- 11.4 System Contributors to Line-Edge Roughness
- 11.4.1 LER Transfer from the Mask to the Wafer
- 11.4.2 Mask Roughness Effects on LER
- 11.4.3 Mask Roughness Effects on Printed Contact Size Variations
- 11.5 Flare in EUVL Systems
- 11.5.1 Sources of Flare and Estimating Flare from Surface Roughness
- 11.5.2 Flare Characterization of the Intel MET
- 11.5.3 Impact of Flare on Patterning Performance and Flare Variation Compensation
- 11.6 Summary
- Acknowledgments
- References
Chapter 12: Lithography Cost of Ownership (CoO)
- 12.1 CoO Overview
- 12.1.1 SEMATECH Lithography CoO Historical Activities
- 12.1.2 General CoO Equations and Input Relationships
- 12.1.3 Lithography Global CoO Input Assumptions
- 12.1.4 Lithography Specific Product Parameters
- 12.2 Lithography Historical Cost and Price Trends
- 12.2.1 Historical Completed Wafer, Die, and Function Costs to Manufacture
- 12.2.2 Historical Photolithography Exposure Tool Price Trends
- 12.2.3 Historical Reticle Costs and Mask Usage Trends
- 12.3 Major Lithography CoO Parameter and Productivity Drivers
- 12.3.1 Example of 100nm Litho Patterning Metal 1 Level CoO within a 90nm Half Pitch Logic Device Manufacturing
- 12.3.2 Exposure Tool Cell Throughput (TPT)
- 12.3.3 Exposure Level Product Requirements (Yield, Send Aheads, and Rework)
- 12.3.4 DUV Source Consumables and Running Costs
- 12.3.5 Photoresist Cost Drivers and Photoresist Process Complexity
- 12.3.6 Reticle Cost Drivers
- 12.3.7 Litho Cell Equipment Reliability, Availability, and Maintainability (RAM)
- 12.4 General Observations on Litho Cell and CoO Improvements (past decade)
- 12.4.1 Exposure Tool Supplier CoO Improvement Factors
- 12.4.2 Optical Laser Source Improvements
- 12.4.3 Photoresist and Photoresist Processing
- 12.4.4 Reticle Improvements
- 12.4.5 FAB Automation Processing and Yield Controls
- 12.5 Brief CoO Considerations for Near Future Lithography Technologies
- 12.5.1 193nm Immersion Lithography (193i)
- 12.5.2 Extreme Ultraviolet Lithography (EUVL)
- 12.5.3 Maskless Lithography (ML2)
- 12.5.4 Nano Imprint Lithography (NIL)
- 12.6 Summary
- 12.7 Example Case Studies of Litho CoO Calculations
- 12.7.1 Example Case 1: Improved Yield at Expense of System Cost and/or TPT Performance
- 12.7.2 Example Case 2: Slight Improved Laser Source Power at Expense of Specialty Gas Costs
- 12.7.3 Example Case 3: Product Lots Reroute To Different Tool vs. Lot Hold
- Acknowledgments
- References
Appendix: Reference Data for the EUV Spectral Region
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