Optical lithography : here is why Chapter 8. Outlook and successors to optical lithography. 8.1. Outlook of optical lithography. 8.1.1. Optical lithography galaxy for logic gates; 8.1.2. Optical lithography galaxy for contact holes; 8.1.3. Optical lithography galaxy for equal lines and spaces 8.2. EUV lithography. 8.2.1. Introduction; 8.2.2. EUV sources; 8.2.3. EUV masks; 8.2.4. EUV projection optics; 8.2.5. Wall power consumption; 8.2.6. EUV resist; 8.2.7. EUV OPC; 8.2.8. Summary of EUVL 8.3. Massively parallel E beam maskless imaging. 8.3.1. Introduction to e beam imaging; 8.3.2. MEB ML2 systems proposed; 8.3.3. Comparison of the different systems; 8.3.4. Data volume and the rate of DW systems; 8.3.5. Power consumption of MEB ML2; 8.3.6. Extendibility of MEB ML2 systems; 8.3.7. Comparison of 4X mask writing to 1X wafer writing; 8.3.8. Applications for MEB ML2; 8.3.9. Summary of MEB ML2 8.4. Outlook of lithography. 8.4.1. Double patterning; 8.4.2. EUV lithography; 8.4.3. MEB ML2; 8.4.4. Nanoimprint lithography 8.5. Conclusions References Index Chapter 7. Immersion lithography. 7.1. Introduction 7.2. Resolution and DOF. 7.2.1. Wavelength reduction and spatial frequencies; 7.2.2. Resolution and DOF scaling equations; 7.2.3. Improving resolution and DOF with an immersion system 7.3. DOF in multilayered media. 7.3.1. Transmission and reflection in multilayered media; 7.3.2. Effects of wafer defocus movements; 7.3.3. Diffraction DOF; 7.3.4. Required DOF; 7.3.5. Available DOF; 7.3.6. Preferred refractive index in the coupling medium; 7.3.7. Tradeoff between resolution and DOFdiffrac 7.4. Polarization dependent stray light. 7.4.1. Imaging at different polarizations; 7.4.2. Stray light 7.5. Immersion systems and components. 7.5.1. Configuration of an immersion system; 7.5.2. The immersion medium; 7.5.3. The immersion lens; 7.5.4. Bubbles in the immersion medium; 7.5.5. The mask; 7.5.6. Subwavelength 3D masks; 7.5.7. The photoresist 7.6. Impact on technology. 7.6.1. Simulation for an immersion system; 7.6.2. Polylayer; 7.6.3. Contact layer; 7.6.4. Metal layer; 7.6.5. Recommendation for the three technology nodes 7.7. Practicing immersion lithography. 7.7.1. Printing results; 7.7.2. Defect reduction; 7.7.3. Monitoring the immersion hood and special routing; 7.7.4. Other defect reduction schemes; 7.7.5. Results 7.8. Extension of immersion lithography. 7.8.1. High index materials; 7.8.2. Solid immersion mask; 7.8.3. Polarized illumination; 7.8.4. Double exposures and pitch splitting; 7.8.5. Pack unpack; 7.8.6. Overcoming the throughput penalty with double imaging 7.9. Conclusion on immersion lithography References Preface Chapter 1. Introducing optical lithography. 1.1. The role of lithography in integrated circuit fabrication 1.2. The goal of lithography 1.3. The metrics of lithography 1.4. The contents of this book Chapter 2 Exposure systems. 2.1. Proximity printing 2.2. Projection printing and a comparison to proximity printing 2.3. Full wafer field 2.4. Step and repeat 2.5. Step and scan 2.6. Reduction and 1X systems 2.7. 1X mask fabricated with a reduction system 2.8. Summary References This book is aimed at new and experienced engineers technology managers and senior technicians who want to enrich their understanding of the image formation physics of a lithographic system. Readers will gain knowledge of the basic equations and constants that drive optical lithography learn the basics of exposure systems and image formation and come away with a full understanding of system components processing and optimization. Readers will also get a primer on the outlook of optical lithography and the many next generation technologies that may greatly enhance semiconductor manufacturing in the near future Chapter 6. Processing and optimization. 6.1. Optimization of the exposure tool. 6.1.1. Optimization of NA; 6.1.2. Optimization of illumination; 6.1.3. Exposure and focus; 6.1.4. DOF budget; 6.1.5. Exposure tool throughput management 6.2. Resist processing. 6.2.1. Resist coating; 6.2.2. Resist baking; 6.2.3. Resist developing; 6.2.4. Aspect ratio of resist image; 6.2.5. Environmental contamination 6.3. k1 Reduction. 6.3.1. Phase shifting masks; 6.3.2. Off axis illumination; 6.3.3. Scattering bars; 6.3.4. Optical proximity correction 6.4. CD uniformity. 6.4.1. CDNU analysis; 6.4.2. CDU improvement References Chapter 3. Image formation. 3.1. The aerial image. 3.1.1. Effects of a spherical wavefront and deviations from it; 3.1.2. Spherical wavefront; 3.1.3. The effect of a finite numerical aperture on the spherical wavefront; 3.1.4. Deviation from a spherical wavefront; 3.1.5. Imaging from a mask pattern; 3.1.6. Spatial frequencies; 3.1.7. Imaging results 3.2. Reflected and refracted images. 3.2.1. Methods to evaluate the reflected and refracted image from a mask; 3.2.2. Impact of multiple reflections on DOF 3.3. The latent image 3.4. The resist image. 3.4.1. The A B C coefficients; 3.4.2. The lumped parameters; 3.4.3. [Beta] and [eta] 3.5. From aerial image to resist image 3.6. The transferred image. 3.6.1. Isotropic etching; 3.6.2. Anisotropic etching; 3.6.3. Lift off; 3.6.4. Ion implantation; 3.6.5. Electroplating References Chapter 4. The metrics of lithography. 4.1. The resolution and DOF scaling equations 4.2. Determination of k1 and k3 based on microscopy 4.3. Determination of k1 k2 and k3 based on lithography. 4.3.1. E D branches trees and regions; 4.3.2. E D window DOF and exposure latitude; 4.3.3. Determination of k1 k2 and k3 using E D windows 4.4. k1 k2 and k3 as normalized lateral and longitudinal units of dimension 4.5. The E D tools.4.5.1. Construction of E D trees; 4.5.2. Importance of log scale in the exposure axis; 4.5.3. Elliptical E D window; 4.5.4. EL versus DOF tradeoff; 4.5.5. Incorrect elliptical E D window; 4.5.6. CD centered versus full CD range E D windows; 4.5.7. E D window and CD control; 4.5.8. Application of E D tools References Chapter 5. Components in optical lithography. 5.1. Light source. 5.1.1. Mercury arc lamp; 5.1.2. Excimer laser 5.2. Illuminator. 5.2.1. Köhler illumination system; 5.2.2. Off axis illumination 5.3. Masks. 5.3.1. Mask substrate and absorber; 5.3.2. Pellicles; 5.3.3. Critical parameters for masks; 5.3.4. Phase shifting masks 5.4. Imaging lens. 5.4.1. Typical lens parameters; 5.4.2. Lens configurations; 5.4.3. Lens aberrations; 5.4.4. Lens fabrication 5.5. Lens maintenance 5.6. Photoresists. 5.6.1. Classifications; 5.6.2. Light interactions with a photoresist; 5.6.3. Profile of resist images 5.7. Antireflection coatings 5.8. Wafer 5.9. Wafer stage 5.10. Alignment system. 5.10.1. Off axis alignment and through the lens alignment; 5.10.2. Field by field global and enhanced global alignment; 5.10.3. Bright field and dark field alignments References