Critical Challenges of EUV Mask Blank Volume Production

Transcription

1 Critical Challenges of EUV Mask Blank Volume Production Holger Seitz, Markus Renno, Thomas Leutbecher, Nathalie Olschewski, Helmut Popp, Torsten Reichardt, Ronny Walter, Günter Hess SCHOTT Lithotec AG, Jerusalemer Str. 13, D Meiningen, Germany U. Kleineberg 1, J. Lin 1, U. Neuhäusler 1, N. Weber 2, M. Merkel 2, A. Oelsner 3, G. Schönhense 3 1 University of Bielefeld, Faculty of Physics, Universitätsstr. 25, D Bielefeld, Germany 2 FOCUS GmbH, Am Birkhecker Berg 20, D Hünstetten-Görsroth, Germany 3 Johannes Gutenberg University Mainz, Saarstr. 21, D Mainz, Germany

2 Outline: Challenge: Achieving a large number of parameters simultaneously on a integrated blank Status of EUV Mask Blanks from SCHOTT Lithotec Performance of available LTEM Substrates Progress in manufacturing defect free blanks EUVL mask blank properties Performance of new TaN-Absorber in mask process Actinic inspection by EUV PEEM Summary 2 Tuesday, November 8th, 2005

3 Challenge: Achieving a large number of parameters simultaneously Absorber stack: Defectivity, optical properties at EUV and inspection wavelength as well as dry etch performance Multilayer stack: Defectivity, EUV-reflectivity and centroid wavelength- uniformity as well as long term stability LTEM substrates: Defectivity, thermal stability, flatness and roughness Backside coating: Defectivity, electrical conductivity Leading-edge metrology 3 Tuesday, November 8th, 2005

4 Substrates LTEM-Substrates: Flatness below 70 nm on both sides available Frontside flatness: < 70 nm Backside flatness: < 70 nm Area: 142 mm x 142 mm Area: 142 mm x 142 mm 4 Tuesday, November 8th, 2005

5 Substrates LTEM-Substrates: Excellent High Spatial Frequency Roughness High Spatial Frequency Roughness of 1.7 Å rms Local slope of 2.3 mrad (250 nm < λ spatial < 5 μm) 5 Tuesday, November 8th, 2005

6 Defectivity of Quartz Substrates: Excellent substrate defect performance after backside coating Defect inspection by Lasertec M1350 (measured at Sematech North Albany) Pixel 6 corresponds to 80 nm 3 defects achieved above 80 nm 0.01 defects/cm 2 achieved for backside coated quartz substrates 6 Tuesday, November 8th, 2005

7 Multilayer: Continuous learning on defect reduction over 2 years Each point corresponds to a mean value of total defects over dozens of samples Cut-off size 200 nm PSL equivalent Absolute Front Defects Learning curve for Multilayers 1 Jul 02 Jan 03 Aug 03 Mrz 04 Sep 04 Apr 05 Okt defects /cm² achieved (cut-off size: 150 nm PSL equivalent) 7 Tuesday, November 8th, 2005

8 EUV-Multilayer Multilayer: Best result on total defect level for EUVL multilayer stack Defect inspection by Lasertec M1350 (measured at Sematech North Albany) Pixel 8 corresponds to 80 nm 0.7 defects/cm 2 achieved for Multilayer Coating on Quartz substrates (cut-off size 80 nm) Learning curve for Multilayers 10 Defect/cm 2 (> 80 nm PSL) Jan 04 Jan 05 Jan 06 Jan 07 8 Tuesday, November 8th, 2005

9 EUV-Reflectometry Multilayer: EUV-Reflectometer from AIXUV GmbH monitors current blank production and development Throughput up to 3 blanks per hour Mapping capability of 140 mm x 140 mm Absolute accuracy of EUV-reflectivity < 0.5% Absolute accuracy of central wavelength < ± nm Calibration by measurements performed at PTB EUV-Reflectivity EUV-Reflectivity of Multilayer Wavelength [nm] AIXUV ESR 9 Tuesday, November 8th, 2005

10 EUV-Multilayer Multilayer: Excellent performance of central wavelength 1.00% 0.80% Uniformity of Centroid Wavelength 0.4% uniformity of central wavelength achieved Full Range 0.60% 0.40% 0.20% 0.00% Blank Number Offset of Centroid Wavelength 0.06 Deviation from Target [nm] Offset of central wavelength from target value well below 0.06 nm (Specification according to SEMATECH Roadmap) Blank Number 10 Tuesday, November 8th, 2005

11 Excellent improvements: Integrated EUV mask blank of Schott Lithotec on track towards production specification Defectivity of Multilayers 0.7 defects/cm 2 (>80nm PSL equivalent) achieved EUV-Performance of Multilayers Multilayer-reflectivity > 64% Uniformity of the reflectivity 0.6% Uniformity of central wavelength: ca. 0.5% Offset of central wavelength from target: < 0.05 nm Flatness of LTEM-Substrates Down to 70 nm on both sides 50 nm on quality area of EUV Alpha Demonstrator tools High spatial frequency roughness of LTEM-Substrates 1.7 Angstroem Local slope of LTEM-Substrates 2.3 mrad 11 Tuesday, November 8th, 2005

12 EUVL Absorber Ta-based Absorber Material: Design for 257 nm inspection wavelength Design includes antireflective coating Low reflectivity <13.5% at 257 nm Thickness uniformity of 3σ < 1% (140 mm x 140 mm) 12 Tuesday, November 8th, 2005

13 EUVL Absorber Ta-based Absorber Material: Good dry etch performance CD uniformity of 3σ = 6.4 nm Sidewall angle larger than Tuesday, November 8th, 2005 Dry etch process developed by IMS Chips Stuttgart/Germany and AMTC Dresden/Germany Further data have been presented at BACUS Photomask 2005

14 Actinic Inspection EUV PEEM: Actinic mask blank defect inspection by EUV PEEM Goal: Development of a full field high resolution at wavelength microscopy technique for fast detection of small defects (50nm size and smaller) in EUVL mask blanks Future tool production and distribution by Focus GmbH Basic principle of the technique Concept Visualization of the wavefront distortion (caused by defects) of the standing EUV wavefield in the ML using a photoelectron emission microscope (PEEM), taking advantage of high electron emission in surface regions with wave front anti-nodes low electron emission for node regions Wavefront phase for node-antinode adoption accomplished by tuning photon energy around 13.5 nm 14 Tuesday, November 8th, 2005

15 Actinic Inspection EUV PEEM: EUV PEEM with toroidal multilayer coated microreflector Setup at BESSY II in Berlin Sample stage with Mask blank toroidal refocusing microreflector 15 Tuesday, November 8th, 2005

16 Actinic Inspection EUV PEEM: Visualization of programmed phase defects 50 nm * 1 µm 1 µm * 1 µm SEM images of an array of 50 nm high Ti nanostructures Images taken BEFORE sputtering the structures with a Mo/Si EUV multilayer 16 Tuesday, November 8th, 2005

17 Actinic Inspection EUV PEEM: Improved actinic defect sensitivity due to refocusing multilayer optic Mid resolution image : High resolution image : Native defects Field of view : 110 mm Field of view : 25 mm Programmed defect (50 nm * 50 nm) 17 Tuesday, November 8th, 2005

18 Actinic Inspection EUV PEEM: PEEM can address 30nm defects PEEM resolution tests with Hg-Lamp (250nm radiation) Field of View 13µm Field of View 2.3µm PEEM: Illumination with Reflector (first try) More Moore _ % % averaged counts % 0% 29nm 29 nm Field of View 110µm x (nm) 18 Tuesday, November 8th, 2005

19 Status Summary: EUV mask blanks from SCHOTT Lithotec are available now EUVL mask blanks based on low defect substrates with flatness down to 70 nm 0.4% central wavelength uniformity achieved Low defect dry-etch optimized buffer and absorber 0.01 defects/cm² for backside coatings on quartz Characterized by advanced metrology of LTEM Substrates and EUV Mask Blanks Actinic inspection by EUV PEEM: Enhanced sensitivity by improved multilayer optics Status: 50nm defect sensitivity for programmed phase defects achieved Goal: 20nm defect sensitivity seems achievable 19 Tuesday, November 8th, 2005

20 Acknowledgements Acknowledgements Would like to thank Florian Letzkus (IMS Chips, Stuttgart/Germany ) as well as Uwe Dersch (AMTC Dresden/Germany) and colleagues for dry etch development German Ministry of Education and Research (contract-no. 13N8853) European project: Medea+ EXTUMASK European project: More Moore (project n : IST IP ) 20 Tuesday, November 8th, 2005