Sub-Wavelength Holographic Lithography SWHL. NANOTECH SWHL Prof. Dr. Vadim Rakhovsky October, 2012

Transcription

1 Sub-Wavelength Holographic Lithography SWHL NANOTECH SWHL Prof. Dr. Vadim Rakhovsky October, 2012

2 EXECUTIVE SUMMARY SWHL is a new, alternative low cost approach to lithography SWHL is suitable for all range of technologies covered by DUVL (ʎ=193) and even smaller CD s using coherent light sources with a shorter wavelength SWHL will cut your costs for: Masks - up to factor of 10! Steppers - up to factor of 4. Existing litho equipment (mask aligner, steppers, etc.) can be used as a base for Holographic Stepper SWHM has an unlimited (almost) lifetime and does not need any repair. Aerial images of IC topologies are not sensitive to SWHM local defects SWHL is based on a mathematical method of holographic mask computation 2

3 NANOTECH SWHL TEAM Professor V.I. Rakhovsky Professor V.A. Borovikov Professor A.S. Shamaev Dr. M.V. Borisov Chief Optitian Dr. А.V. Boshliakov Senior Physisits D.A. Chelyubeev Senior Programmer D.Yu. Knyazkov Mathematitian A.A. Gavrikov Programmer V.V. Posdnyakov Senior Engineer V.V. Chernik Physicists P.A. Mikheev Programmer 3

4 WHAT IS SWHL? SWHL realizes a new approach to the lithography process SWHL is based on and employs the basic principles of wave optics to create topologies with sub-wavelength elements SWHL uses newly developed mathematical apparatus that made possible digital synthesis of SWHM for aerial images with topology elements with CD s λ/2 SWHM combines main functions of a mask and projection lens in the projection lithography 4

5 PROJECTION LITHOGRAPHY VS. SWHL Projection Lithography uses the principle of a photo camera. Highly complicated and expensive optical projection system is required to produce images of high quality. SWHL uses the principle of wave-front reconstruction (discovered by D. Gabor). SWHL does not require any optical system. 5

6 HOLOGRAPHIC LITHOGRAPHY IN PAPERS AND PATENTS Most papers and patents on periodical structures creation, that use the term "holographic lithography, mean interferential lithography There are no papers or patents related to manufacturing of sub-wavelength IC topologies with the use of holographic masks. There are works where test images are created. Characteristic sizes of these images topology elements are much larger then recovery radiation wavelength. There are no papers on digital synthesis of holographic patterns containing considerable number (>107) of topology elements. There are no papers on the creation of holograms allowing to reconstruct IC layer topologies with required quality. 6

7 MAIN FEATURES 7

8 SIMPLE AND MORE EFFICIENT OPTICAL SCHEME Traditional mask is replaced with a hologram (Sub-wavelength Holographic Mask - SWHM) No Projection Lens used Exposure stage at traditional projective lithography Carl Zeiss Patent, US , 2004 Exposure stage at sub-wavelength holographic lithography (SWHL) 8

9 COMPLEX TECHNOLOGICAL OPERATIONS (PHASE-SHIFT AND OPC) ARE REPLACED BY COMPUTATION DUV-mask SWHM Initial Topology DUVL Contour of Aerial Image SWHL Contour of Aerial Image 9

10 SWHM CONSISTS OF SIMPLE UNIFORM ELEMENTS Desired topology in Si-wafer Corresponding SWHM Small part of SWHM Small part of band The linear size of transmission areas varies from 0.7λ to the full size of cell. The linear size of SWHM cell is constant and defined beforehand. It falls within the range 5λ to 2,5λ. 9 cells with 9 transmission areas (TA) 10

11 SWHM TOPOLOGY DOES NOT DEPEND ON AERIAL IMAGE COMPLEXITY (computer simulation 1) λ /2 Original SWHM Aerial Image Hologram Size Quantity of Transmission areas Picture Size 300μm x 300μm μm x 86μm 11

12 SWHM TOPOLOGY DOES NOT DEPEND ON AERIAL IMAGE COMPLEXITY (computer simulation 2) Original SWHM Aerial Image Hologram Size Quantity of Transmission Areas Picture Size 300μm x 300μm μm x 86μm 12

13 SWHM LOCAL DEFECTS DO NOT AFFECT AERIAL IMAGE QUALITY Defect-free SWHM Aerial image SWHM with 7% working area defects Aerial Image DUVL&EUVL SWHL Acceptable ratio of the total area of defects to the overall mask working area DUVL EUVL < Used as an all-time and full operation routine For DUVL and EUVL Rather short <12 weeks, for EUVL very short <2 weeks Defect inspection and post-correction Life time for IC mass production (insignificant decrease of image quality) Used as a one-time (after mask production) and minimal operation manipulation Practically unlimited 13

14 SWHM LOCAL DEFECTS DO NOT AFFECT AERIAL IMAGE QUALITY CONTD. Dust area (in %) on the SWHM (each particle 1 μ 2 ) 0% 45% 98% Initial image ( black and white indicates Phase-Shift) Normalized aerial images (dusted SWHM are above) (Computer simulation) 14

15 Virtual HoloOPC & HoloPhase-Shift 15

16 CONVENTIONAL OPC IS REPLACED WITH VIRTUAL HOLOOPC Conventional calculated & technologically produced OPC HoloOPC is realized by computation and not produced technologically Chris Mack, «Fundamental Principles of Optical Lithography:The Science of Microfabrication», 2009 John Wiley & Sons 1 2 Contours of aerial image before (1) and after (2) HoloOPC 16

17 CONVENTIONAL ALTERNATIVE PHASE-SHIFT IS REPLACED WITH ALTERNATIVE HOLO PHASE SHIFT Conventional alternative phaseshift is realized as a technological operation Alternative holo phase-shift is realized by computation and does not need any technological operation Phase 0 Phase 180 Initial topology Alternative phases Hologram Contour of topology Aerial image of topology Chris Mack, «Fundamental Principles of Optical Lithography:The Science of Microfabrication», 2009 John Wiley & Sons 17

18 CONTINUOUS HOLOPHASE-SHIFT ALLOWS TO CREATE TOPOLOGIES IMPOSSIBLE WITH PROJECTION LITHO FOR CD S = Λ/2 Initial Topologies Recovered Images 18

19 HoloOptimization We can continuously change local values of phase & amplitude of radiation used for creation of aerial image on photo resist. With HoloOptimization method we can obtain topologies that are not possible with projection lithography. Initial Topology Optimized Topology SWHM Optimized Image Contour Optimized Image 19

20 ECONOMICS

21 Comparison of Mask Service Reasons for DUVL & SWHL Damage of pellicle % Nonremovable particles % Particles under pellicles % Damaged masks % Exposure degradation % Other random local defects % DUVL 23,4 23,3 4,4 3,6 11,7 33,9 SWHL none* none none none none none * Pellicle not used No need for regular service for SWHM 21

22 PRICE of DUVL & SWHL Masks for Different Technologies Nanotech SWHL s data Prices of DUV-masks is taken from SEMATECH data 22

23 Some Estimates Price of Stepper Annual Cost of Stepper Maintenance Price of Mask-Set Annual Cost of Mask-Set Maintenance (Cleaning, Repel & Control) Si-FAB s Total Expenses for Basic Litho Equipment DUVL 60 3,6 1,5 9* 80,6 SWHL 30 0,8 0,6-31,4 * After illumination of 5000 wafers DUV-mask requires Cleaning, Repel & Control Operations. The cost of such operations for Mask-Set is 5% of it s Price. Estimation is done for Fab with capacity w/months for 45 nm technology. All Prices & Expenses in $M 23

24 Experimental results (produced with HoloPhase-Shift & HoloOPC) 24

25 Aerial Image of Test Sample Achieved Resolution: 0,56λ Simulated Aerial Image Tag-stripes (Image registered by ССD-Matrix, λ= nm) Stripes, L - length нм B - width & gap 250 nm Stripes, L - length нм b- width & gap 350 nm 25

26 SEM-Photo of Test 0bject Image on Photo Resist x Non-optimal development causes width of stripes 0,35 λ 26

27 Thank You for Your ATTENTION!