Challenges of EUV masks and preliminary evaluation Naoya Hayashi Electronic Device Laboratory Dai Nippon Printing Co.,Ltd. EUV Mask Workshop 2004 1
Contents Recent Lithography Options on Roadmap Challenges for EUV Mask Multi Layer Substrates Defect Free Mask Absorber Delineation (Writing Tools & Processes) Inspection & Repair Metrology With Preliminary Results Summary EUV Mask Workshop 2004 2
Potential Lithography Solutions Technology Node 2004 2007 2010 2013 2016 2019 2003 2005 2006 2008 2009 2011 2012 2014 2015 2017 2018 hp90 hp65 hp45 hp32 hp22 hp16 90 193 nm Technology Options at Technology Nodes (DRAM Half-Pitch, nm) 193nm + LFD 193nm immersion PEL 65 Narrow options 45 193nm immersion + LFD EUV ML2, 157nm immersion, PEL Narrow options 32 EUV 193nm immersion + LFD 157nm immersion + LFD, ML2 Imprint EUV Innovative 157nm or 193 nm immersion 22 ML2 Imprint, innovative technology Narrow options DRAM Half-pitch (dense lines) Narrow options Innovative technology ML2, EUV + RET, imprint Narrow 16 options Research Required Development Underway Qualification/Pre-Production Continuous Improvement This legend indicates the time during which research, development, and qualification/pre-production should be taking place for the solution. EUV Mask Workshop 2004 3
65nm-45nm node lithography/mask options 193nm extension (RET from mask side) Aggressive OPC (ie Scattering Bar of 100nm width) will be inevitable. High transmission att-psm (both embedded shifter type and CLM) with tritone feature is thought as a possible option. Aggressive Alt-PSM adoption.. 193nm immersion lithography There is no major mask related issue for immersion lithography. RET will be accelerated. 157nm Dry and/or Immersion will be the backup for 45nm and beyond. Electron beam lithography LEEPL technology has been focusing on hole pattern for memory devices. Image placement measurement, defect Inspection/repair, are still in development stage. EUV lithography Research & Development for production engineering is required. Especially, defect-free multi layer substrate, inspection/repair, are critical issues. EUV Mask Workshop 2004 4
Current Status and Schedule for EUV Mask Development Current Status Through research activity with consortia, trying to define EUV mask specifications Absorber, buffer/capping layer materials Patterning processes Printable defects, inspection, metrology, etc. Starting to provide evaluation plate 2004/H2. Multilayer substrate will be available from several vendors. Future Plan Investment for production will start 2006 EUV Mask Workshop 2004 5
EUVL mask stacking structure Absorber layer(s) Buffer layer Capping layer Multilayer (about 40 pairs of Mo and Si) Underlayer LTEM Conductive coating EUV Mask Workshop 2004 6
EUVL blank initial test results Tantalum based absorber on Chromium based buffer Etching capability test of 200nm patterns Hole Iso-Space Repair capability test with Micromachining Reference Defect size 160nm Iso-Line L&S After repair Currently, several sets of materials from various blank suppliers are tested to investigate their capability as absorber and buffer. EUV Mask Workshop 2004 7
Cross section profile of TaGeN Dense line Dense hole Isolate line CF4 gas process Cl2 gas process Pattern size 200nm Vertical side wall were obtained in both gas process courtesy by ASET EUV Mask Workshop 2004 8
Etch bias uniformity Exposure tool : 50kV EB Measurement tool : CD-SEM Area size : 122 X 122 mm 2 Pattern : 400 nm Iso-Space CF4 process +5nm -5nm Cl2 process Mean : 2.05nm Max : 9.31nm Min : -4.31nm 3sigma : 9.95nm Mean : -27.3nm Max : -21.62nm Min : -33.71nm 3sigma : 8.36nm EUV Mask Workshop 2004 9
EUV mask reflectivity EUV reflectivity after buffer layer dry etching Absorber layer : CF4 gas process 70 60 Buffer layer : Cl2 + O2 gas process Reflectivity [%] 50 40 30 20 10 0 12.5 13 13.5 14 14.5 Wavelength [nm] Centroid wavelength : 13.54nm Peak reflectivity : 63.8% courtesy by ASET EUV Mask Workshop 2004 10
EUV mask pattern and wafer print result 70nm line and space pattern 5um Mask pattern ( Exposure tool : HiNA set 3) 1um Wafer pattern courtesy by ASET and Nikon EUV Mask Workshop 2004 11
Availability of mask infrastructures EUV Mask Workshop 2004 12
Mask Writing Systems Vendor Systems Writing Strategy Etec Systems MEBES-RSB Variable Shaped E-Beam Etec Systems ALTA-4000 Spot Multi-Laser-Beam JEOL JBX-3030 Variable Shaped E-Beam Hitachi HT HL-7000M Variable Shaped E-Beam Nu Flare EBM-4000 Variable Shaped E-Beam Raster Scan Raster Scan Vector Scan Vector Scan Vector Scan Accelerating 50KeV (257nm) 50KeV 50KeV 50KeV Voltage Max.Substrat 6 inch sq. 6 inch sq. 7 inch sq. 7 inch sq. 230mm sq. e Size Writing Area - 144 x 144 mm - 7 inch x 7 inch 222 x 228.6 mm Min.Feature Size 0.20 um 0.35 um - 0.10 um 0.25 um Min.Addressing 1.0 nm 2.5 nm 1.0 nm 1.0 nm 1.0 nm Pattern Position Accuracy Overlay 12 nm(3 ) 22 nm(3 ) 15 nm(max.) 15 nm(3 ) 12 nm(3 ) 8 nm(3 ) 15 nm(3 ) - - 10 nm(3 ) Accuracy Butting Error 10 nm(mean+r/2) 10 nm (Mean+R/2) 15 nm(max.) 10 nm(mean+3 ) - CD Accuracy 7 nm ( 3 ) 12 nm (Range/2) 8 nm(3 ) 8 nm(3 ) 7 nm(3 ) (Global Unif.) Remarks 2 Pass Writing 4 Pass Writing 2 Pass Writing 2 Pass Writing 4 Pass Writing EUV Mask Workshop 2004 13
Resist material vs. Resolution Resist SEM Image (minimum resolution) Isolated space 80nm 40nm 40nm 35nm Dense space 100nm 70nm 55nm 75nm Hole 120nm 90nm 65nm 65nm Resist Thickness CAR_A 400nm CAR_A 100nm CAR_B 100nm Non-CAR_A 300nm EUV Mask Workshop 2004 14
Mask Inspection Systems Syetem MD3000 LM7000 LM7000B SLF87 KLA575(576) DUV Aera193 Maker Lasertec NEC NEC KLA-Tencor KLA-Tencor AMAT Mode D/D (Cell shift) D/B, D/D D/B, D/D D/B, D/D, SL D/B, D/D Illumination for inspection Wavelength [nm] Trans only Trans only Trans and Reflect Trans and Reflect Trans, Reflect D/D, (D/M) (Aerial Image) Trans only 248 266 266 365 257 193 Pixel size [nm] 125 100 100 150 125 (90) 150 Sensitivity [nm] 100 (80) 100 80 100 80 (70) 10%CD@wafer Min. Line width [nm] Scan Time [min] 100mm sq. 300 400 280 400 B225/W255 (B180/W200) Not specified 120 122 195 74 90 (175) 120 EUV Mask Workshop 2004 15
Absorber layer defect repair Evaluated repair technique FIB-GAE (Gas Assist Etching) AFM Machining FIB-GAE Ga + beam AFM Machining AFM tip (Diamond) Cr XeF2 gas Substrate TaGeN Cr Substrate TaGeN EUV Mask Workshop 2004 16
SEM images of AFM machining defect repair results Before buffer layer dry etching Reference 1um line and space Defect pattern size 0.5 um TEST 1-1 X bias 40nm Z bias 5nm TEST 1-3 X bias 0nm Z bias 5nm TEST 1-2 X bias 20nm Z bias 5nm TEST 2-2 X bias 20nm Z bias 0nm EUV Mask Workshop 2004 17
Mask Topography Measurement with CD-AFM Differences Between 1D and 2D SFM Scan direction Servo direction Scan direction Servo direction EUV Mask Workshop 2004 18
Summary Mask technology development for EUV has been establishing with Consortia at feasibility study stage. Most of current infrastructures and technologies have been adapting for preliminary evaluation of EUV mask making. Ta based absorber material has been patterned successfully. Various repair technologies for absorber pattern has been evaluating. Issues are Quality of substrate material (Specifications??) Improvement of mask quality (CD, etc.) Inspection & repair Cleaning and mask handling What do you really want?! Need feed back from exposure result to define realistic specifications. Printable defects, flatness, surface treatment, etc. EUV Mask Workshop 2004 19