EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Optical Projection Printing and Modeling Purpose Explain 8 of the top 10 phenomena and concepts key to understanding optical projection printing Basic Parameters Resolution and Depth of Focus Optical Proximity Effects Bragg Diffraction and Image Calculation Image Characterization I EE 0 25 NL MEEF LAVA Website Simulation Mask Viewer Suggested reading Griffin Plummer Deal and Chapter 5 Sheats and Smith 188 196 124 133 148 152 182 188 121 Wong 31 45 55 58 83 Copyright 2006 Regents of University of California EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 ASML 5500 90 Tool Fly s Eye Sigma Aperture Light path Condenser Lens Mask Port Objective Lens To Wafer Copyright 2006 Regents of University of California Hexagonal Light Pipe Output EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Projection Printer Examples Wafer Mask Stepper Mask Scanner Wafer Sheats and Smith Copyright 2006 Regents of University of California EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Optical Projection Printing Parameters 0 Key Parameters NA Wavelength 248 nm Numerical Aperture NA sin 0 5 Partial Coherence Factor NAc NAo 0 3 Copyright 2006 Regents of University of California EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Parameters for Microlab Projection Printers Working Resolution k1 LEN deg ILL deg k1 NA nm 4NA nm TFR nm Canon 436 0 28 gh 405 0 7 0 8 16 11 1250 390 5500 4 GCA g 436 0 28 0 7 0 8 16 11 1250 390 5500 10 GCA i 0 5 0 8 19 13 900 285 3500 10 0 25 0 7 30 7 2 350 125 990 Tool nm NA 365 0 32 ASML 248 DUV 0 5 TFR Total focus range 2 x Rayleigh Depth of Focus 2DOF M is the demagnification factor Copyright 2006 Regents of University of California LLINEWIDTH k1 NA DOF k 2 2 2 NA 5 EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Optical System Point Spread Function Mask The small pinhole due to its size diffracts uniformly over all angles Pin hole This diffraction uniformly fills the lens pupil Lens Wafer Image of a pin hole Diffraction limited Relationship for electric fields The lens re phases the remaining emerging rays so that they re converge at the wafer with the same relative phases and uniform magnitude The electric field at the waver is thus the inverse Fourier transform of a disk Airy Function The intensity is the time average of the square of the electric field Airy function 2 The pattern shape is independent of the shape of the pin hole with diameter 1 22 NA The peak E is proportional to pin hole area the peak I is proportional to Area2 or dimension 4 Copyright 2006 Regents of University of California EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Resolution in Projection Printing f focal distance d lens diameter Point spread function f f 1 22 0 61 0 61 NA d d 2 F f d Null position Copyright 2006 Regents of University of California Minimum separation of a star to be visible PDG Fig Ch 5 EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Resolution Transverse Variation Larger angles give higher resolution 1 Resolution P 2 2 sin 0 5 NA 248 nm Assumes one wave is onaxis and the other off axis TRANS sin 3 22 800nm The most useful rays in forming an image are those with the same pitch as the pattern Copyright 2006 Regents of University of California Wave graphic by Ongi Englander and Kien Lam EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Depth of Focus Phase change on vertical axis Plane of Best Focus 4 75 5 0 Plane of Rayleigh l 4 Defocus Copyright 2006 Regents of University of California Wave graphic by Ongi Englander and Kien Lam Observe phase along a vertical line EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Depth of Focus in Projection Printing 2 Depth of Focus 2NA2 Result must be modified for a High NA and b Two waves at arbitrary angles Copyright 2006 Regents of University of California PDG Fig Ch 5 EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Normalized Parameters For any wavelength and numerical aperture NA LLINEWIDTH k1 NA DOF k 2 2 2 NA 365 248 193 157 13 4 nm NA 0 167 0 38 0 5 0 63 0 7 0 75 0 80 Instead of recalculation for every new combination of and NA a universal catalog of image behavior can be utilized if we first determine the k1 and k2 factors in the actual system for the linewidth and defocus and look up results in a data based based on 0 5 m and NA 0 5 0 5 m LLINEWIDTH k1 k1 k1 m NA 0 5 0 5 m DOF k 2 k2 k 2 m 2 2 2 NA 2 0 5 Copyright 2006 Regents of University of California EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Optical Proximity Effect lateral influence function E field Point Spread Function for Coherent Imaging illuminator Condenser lens Finite size of projection lens i e low pass filter images point on mask as Airy pattern on wafer mask Airy IFT disk f l NA Projection lens wafer Copyright 2006 Regents of University of California NA 0 6 1 1 EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Various Types of Image Distortion Proximity effect with neighbors End shortening Copyright 2006 Regents of University of California Nonlinearity with size Corner rounding EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Optical Proximity Correction OPC Called Optical Process Proximity Correction OPP when compensations for other process effects are included Wong Copyright 2006 Regents of University of California EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Qualitative Explanation of image degradation by lens Mask 2 wafer plane lens 1 0 1 parallel optical beam L P sin n 2 grating with spatial frequency 1 P S P Copyright 2006 Regents of University of California n 0 1 2 lm P 2L sin NA of lens EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Bragg Condition Incident ray with wave fronts P L Quartz S n P L S n Transmitted ray P sin n n Copyright 2006 Regents of University of California Chrome Wavefronts Ray of Light Diffracted ray 3 The Bragg condition sets the diffraction angles EE 143 Optical Lithography Lecture A R Neureuther Sp 2006 Ver 4 11 06 Pupil Wave Traffic Partial Coherence 4 Lens is a low pass filter of mask diffraction at Bragg angles Sin Y …
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