| |
| |
| Preface | |
| |
| |
| |
| Introduction to Semiconductor Lithography | |
| |
| |
| |
| Basics of IC Fabrication | |
| |
| |
| |
| Patterning | |
| |
| |
| |
| Etching | |
| |
| |
| |
| Ion Implantation | |
| |
| |
| |
| Process Integration | |
| |
| |
| |
| Moore's Law and the Semiconductor Industry | |
| |
| |
| |
| Lithography Processing | |
| |
| |
| |
| Substrate Preparation | |
| |
| |
| |
| Photoresist Coating | |
| |
| |
| |
| Post-Apply Bake | |
| |
| |
| |
| Alignment and Exposure | |
| |
| |
| |
| Post-exposure Bake | |
| |
| |
| |
| Development | |
| |
| |
| |
| Postbake | |
| |
| |
| |
| Measure and Inspect | |
| |
| |
| |
| Pattern Transfer | |
| |
| |
| |
| Strip | |
| |
| |
| Problems | |
| |
| |
| |
| Aerial Image Formation - The Basics | |
| |
| |
| |
| Mathematical Description of Light | |
| |
| |
| |
| Maxwell's Equations and the Wave Equation | |
| |
| |
| |
| General Harmonic Fields and the Plane Wave in a Nonabsorbing Medium | |
| |
| |
| |
| Phasors and Wave Propagation in an Absorbing Medium | |
| |
| |
| |
| Intensity and the Poynting Vector | |
| |
| |
| |
| Intensity and Absorbed Electromagnetic Energy | |
| |
| |
| |
| Basic Imaging Theory | |
| |
| |
| |
| Diffraction | |
| |
| |
| |
| Fourier Transform Pairs | |
| |
| |
| |
| Imaging Lens | |
| |
| |
| |
| Forming an Image | |
| |
| |
| |
| Imaging Example: Dense Array of Lines and Spaces | |
| |
| |
| |
| Imaging Example: Isolated Space | |
| |
| |
| |
| The Point Spread Function | |
| |
| |
| |
| Reduction Imaging | |
| |
| |
| |
| Partial Coherence | |
| |
| |
| |
| Oblique Illumination | |
| |
| |
| |
| Partially Coherent Illumination | |
| |
| |
| |
| Hopkins Approach to Partial Coherence | |
| |
| |
| |
| Sum of Coherent Sources Approach | |
| |
| |
| |
| Off-Axis Illumination | |
| |
| |
| |
| Imaging Example: Dense Array of Lines and Spaces Under Annular Illumination | |
| |
| |
| |
| Kohler Illumination | |
| |
| |
| |
| Incoherent Illumination | |
| |
| |
| |
| Some Imaging Examples | |
| |
| |
| Problems | |
| |
| |
| |
| Aerial Image Formation - The Details | |
| |
| |
| |
| Aberrations | |
| |
| |
| |
| The Causes of Aberrations | |
| |
| |
| |
| Describing Aberrations: the Zernike Polynomial | |
| |
| |
| |
| Aberration Example - Tilt | |
| |
| |
| |
| Aberration Example - Defocus, Spherical and Astigmatism | |
| |
| |
| |
| Aberration Example - Coma | |
| |
| |
| |
| Chromatic Aberrations | |
| |
| |
| |
| Strehl Ratio | |
| |
| |
| |
| Pupil Filters and Lens Apodization | |
| |
| |
| |
| Flare | |
| |
| |
| |
| Measuring Flare | |
| |
| |
| |
| Modeling Flare | |
| |
| |
| |
| Defocus | |
| |
| |
| |
| Defocus as an Aberration | |
| |
| |
| |
| Defocus Example: Dense Lines and Spaces and Three-Beam Imaging | |
| |
| |
| |
| Defocus Example: Dense Lines and Spaces and Two-Beam Imaging | |
| |
| |
| |
| Image Isofocal Point | |
| |
| |
| |
| Focus Averaging | |
| |
| |
| |
| Reticle Defocus | |
| |
| |
| |
| Rayleigh Depth of Focus | |
| |
| |
| |
| Imaging with Scanners Versus Steppers | |
| |
| |
| |
| Vector Nature of Light | |
| |
| |
| |
| Describing Polarization | |
| |
| |
| |
| Polarization Example: TE Versus TM Image of Lines and Spaces | |
| |
| |
| |
| Polarization Example: The Vector PSF | |
| |
| |
| |
| Polarization Aberrations and the Jones Pupil | |
| |
| |
| |
| Immersion Lithography | |
| |
| |
| |
| The Optical Invariant and Hyper-NA Lithography | |
| |
| |
| |
| Immersion Lithography and the Depth of Focus | |
| |
| |
| |
| Image Quality | |
| |
| |
| |
| Image CD | |
| |
| |
| |
| Image Placement Error (Distortion) | |
| |
| |
| |
| Normalized Image Log-Slope (NILS) | |
| |
| |
| |
| Focus Dependence of Image Quality | |
| |
| |
| Problems | |
| |
| |
| |
| Imaging in Resist: Standing Waves and Swing Curves | |
| |
| |
| |
| Standing Waves | |
| |
| |
| |
| The Nature of Standing Waves | |
| |
| |
| |
| Standing Waves for Normally Incident Light in a Single Film | |
| |
| |
| |
| Standing Waves in a Multiple-Layer Film Stack | |
| |
| |
| |
| Oblique Incidence and the Vector Nature of Light | |
| |
| |
| |
| Broadband Illumination | |
| |
| |
| |
| Swing Curves | |
| |
| |
| |
| Reflectivity Swing Curve | |
| |
| |
| |
| Dose-to-Clear and CD Swing Curves | |
| |
| |
| |
| Swing Curves for Partially Coherent Illumination | |
| |
| |
| |
| Swing Ratio | |
| |
| |
| |
| Effective Absorption | |
| |
| |
| |
| Bottom Antireflection Coatings | |
| |
| |
| |
| BARC on an Absorbing Substrate | |
| |
| |
| |
| BARCs at High Numerical Apertures | |
| |
| |
| |
| BARC on a Transparent Substrate | |
| |
| |
| |
| BARC Performance | |
| |
| |
| |
| Top Antireflection Coatings | |
| |
| |
| |
| Contrast Enhancement Layer | |
| |
| |
| |
| Impact of the Phase of the Substrate Reflectance | |
| |
| |
| |
| Imaging in Resist | |
| |
| |
| |
| Image in Resist Contrast | |
| |
| |
| |
| Calculating the Image in Resist | |
| |
| |
| |
| Resist-Induced Spherical Aberrations | |
| |
| |
| |
| Standing Wave Amplitude Ratio | |
| |
| |
| |
| Defining Intensity | |
| |
| |
| |
| Intensity at Oblique Incidence | |
| |
| |
| |
| Refraction into an Absorbing Material | |
| |
| |
| |
| Intensity and Absorbed Energy | |
| |
| |
| Problems | |
| |
| |
| |
| Conventional Resists: Exposure and Bake Chemistry | |
| |
| |
| |
| Exposure | |
| |
| |
| |
| Absorption | |
| |
| |
| |
| Exposure Kinetics | |
| |
| |
| |
| Post-Apply Bake | |
| |
| |
| |
| Sensitizer Decomposition | |
| |
| |
| |
| Solvent Diffusion and Evaporation | |
| |
| |
| |
| Solvent Effects in Lithography | |
| |
| |
| |
| Post-exposure Bake Diffusion | |
| |
| |
| |
| Detailed Bake Temperature Behavior | |
| |
| |
| |
| Measuring the ABC Parameters | |
| |
| |
| Problems | |
| |
| |
| |
| Chemically Amplified Resists: Exposure and Bake Chemistry | |
| |
| |
| |
| Exposure Reaction | |
| |
| |
| |
| Chemical Amplification | |
| |
| |
| |
| Amplification Reaction | |
| |
| |
| |
| Diffusion | |
| |
| |
| |
| Acid Loss | |
| |
| |
| |
| Base Quencher | |
| |
| |
| |
| Reaction-Diffusion Systems | |
| |
| |
| |
| Measuring Chemically Amplified Resist Parameters | |
| |
| |
| |
| Stochastic Modeling of Resist Chemistry | |
| |
| |
| |
| Photon Shot Noise | |
| |
| |
| |
| Chemical Concentration | |
| |
| |
| |
| Some Mathematics of Binary Random Variables | |
| |
| |
| |
| Photon Absorption and Exposure | |
| |
| |
| |
| Acid Diffusion, Conventional Resist | |
| |
| |
| |
| Acid-Catalyzed Reaction-Diffusion | |
| |
| |
| |
| Reaction-Diffusion and Polymer Deblocking | |
| |
| |
| |
| Acid-Base Quenching | |
| |
| |
| Problems | |
| |
| |
| |
| Photoresist Development | |
| |
| |
| |
| Kinetics of Development | |
| |
| |
| |
| A Simple Kinetic Development Model | |
| |
| |
| |
| Other Development Models | |
| |
| |
| |
| Molecular Weight Distributions and the Critical Ionization Model | |
| |
| |
| |
| Surface Inhibition | |
| |
| |
| |
| Extension to Negative Resists | |
| |
| |
| |
| Developer Temperature | |
| |
| |
| |
| Developer Normality | |
| |
| |
| |
| The Development Contrast | |
| |
| |
| |
| Defining Photoresist Contrast | |
| |
| |
| |
| Comparing Definitions of Contrast | |
| |
| |
| |
| The Practical Contrast | |
| |
| |
| |
| Relationship between [gamma] and r[subscript max]/r[subscript min] | |
| |
| |
| |
| The Development Path | |
| |
| |
| |
| The Euler-Lagrange Equation | |
| |
| |
| |
| The Case of No z-Dependence | |
| |
| |
| |
| The Case of a Separable Development Rate Function | |
| |
| |
| |
| Resist Sidewall Angle | |
| |
| |
| |
| The Case of Constant Development Gradients | |
| |
| |
| |
| Segmented Development and the Lumped Parameter Model (LPM) | |
| |
| |
| |
| LPM Example - Gaussian Image | |
| |
| |
| |
| Measuring Development Rates | |
| |
| |
| Problems | |
| |
| |
| |
| Lithographic Control in Semiconductor Manufacturing | |
| |
| |
| |
| Defining Lithographic Quality | |
| |
| |
| |
| Critical Dimension Control | |
| |
| |
| |
| Impact of CD Control | |
| |
| |
| |
| Improving CD Control | |
| |
| |
| |
| Sources of Focus and Dose Errors | |
| |
| |
| |
| Defining Critical Dimension | |
| |
| |
| |
| How to Characterize Critical Dimension Variations | |
| |
| |
| |
| Spatial Variations | |
| |
| |
| |
| Temporal Variations and Random Variations | |
| |
| |
| |
| Characterizing and Separating Sources of CD Variations | |
| |
| |
| |
| Overlay Control | |
| |
| |
| |
| Measuring and Expressing Overlay | |
| |
| |
| |
| Analysis and Modeling of Overlay Data | |
| |
| |
| |
| Improving Overlay Data Analysis | |
| |
| |
| |
| Using Overlay Data | |
| |
| |
| |
| Overlay Versus Pattern Placement Error | |
| |
| |
| |
| The Process Window | |
| |
| |
| |
| The Focus-Exposure Matrix | |
| |
| |
| |
| Defining the Process Window and DOF | |
| |
| |
| |
| The Isofocal Point | |
| |
| |
| |
| Overlapping Process Windows | |
| |
| |
| |
| Dose and Focus Control | |
| |
| |
| |
| H-V Bias | |
| |
| |
| |
| Astigmatism and H-V Bias | |
| |
| |
| |
| Source Shape Asymmetry | |
| |
| |
| |
| Mask Error Enhancement Factor (MEEF) | |
| |
| |
| |
| Linearity | |
| |
| |
| |
| Defining MEEF | |
| |
| |
| |
| Aerial Image MEEF | |
| |
| |
| |
| Contact Hole MEEF | |
| |
| |
| |
| Mask Errors as Effective Dose Errors | |
| |
| |
| |
| Resist Impact on MEEF | |
| |
| |
| |
| Line-End Shortening | |
| |
| |
| |
| Measuring LES | |
| |
| |
| |
| Characterizing LES Process Effects | |
| |
| |
| |
| Critical Shape and Edge Placement Errors | |
| |
| |
| |
| Pattern Collapse | |
| |
| |
| Problems | |
| |
| |
| |
| Gradient-Based Lithographic Optimization: Using the Normalized Image Log-Slope | |
| |
| |
| |
| Lithography as Information Transfer | |
| |
| |
| |
| Aerial Image | |
| |
| |
| |
| Image in Resist | |
| |
| |
| |
| Exposure | |
| |
| |
| |
| Post-exposure Bake | |
| |
| |
| |
| Diffusion in Conventional Resists | |
| |
| |
| |
| Chemically Amplified Resists - Reaction Only | |
| |
| |
| |
| Chemically Amplified Resists - Reaction-Diffusion | |
| |
| |
| |
| Chemically Amplified Resists - Reaction-Diffusion with Quencher | |
| |
| |
| |
| Develop | |
| |
| |
| |
| Conventional Resist | |
| |
| |
| |
| Chemically Amplified Resist | |
| |
| |
| |
| Resist Profile Formation | |
| |
| |
| |
| The Case of a Separable Development Rate Function | |
| |
| |
| |
| Lumped Parameter Model | |
| |
| |
| |
| Line Edge Roughness | |
| |
| |
| |
| Summary | |
| |
| |
| Problems | |
| |
| |
| |
| Resolution Enhancement Technologies | |
| |
| |
| |
| Resolution | |
| |
| |
| |
| Defining Resolution | |
| |
| |
| |
| Pitch Resolution | |
| |
| |
| |
| Natural Resolutions | |
| |
| |
| |
| Improving Resolution | |
| |
| |
| |
| Optical Proximity Correction (OPC) | |
| |
| |
| |
| Proximity Effects | |
| |
| |
| |
| Proximity Correction - Rule Based | |
| |
| |
| |
| Proximity Correction - Model Based | |
| |
| |
| |
| Subresolution Assist Features (SRAFs) | |
| |
| |
| |
| Off-Axis Illumination (OAI) | |
| |
| |
| |
| Phase-Shifting Masks (PSM) | |
| |
| |
| |
| Alternating PSM | |
| |
| |
| |
| Phase Conflicts | |
| |
| |
| |
| Phase and Intensity Imbalance | |
| |
| |
| |
| Attenuated PSM | |
| |
| |
| |
| Impact of Phase Errors | |
| |
| |
| |
| Natural Resolutions | |
| |
| |
| |
| Contact Holes and the Point Spread Function | |
| |
| |
| |
| The Coherent Line Spread Function (LSF) | |
| |
| |
| |
| The Isolated Phase Edge | |
| |
| |
| Problems | |
| |
| |
| |
| Glossary of Microlithographic Terms | |
| |
| |
| |
| Curl, Divergence, Gradient, Laplacian | |
| |
| |
| |
| The Dirac Delta Function | |
| |
| |
| Index | |