Progress of Optical Design for EUV Lithography Tools in BIT

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1 2014 EUVL Workshop Progress of Optical Design for EUV Lithography Tools in BIT Yanqiu Li*, Zhen Cao, Fei Liu, Qiuli Mei, Yan Liu Beijing Institute of Technology, China June 25, 2014

2 OUTLINE Introduction Design of EUV projection objective Grouping design method Design of co-axial objective systems Design of off-axial objective systems Design of EUV illuminator Reverse design/adjustment method Design results Acknowledgment 2

3 Introduction Constraints for Objective High resolution Almost none distortion Telecentricity on image side Accessible Stop Working distance Low aspheric departure Constraints for illuminator pupil matching high uniformity at the arc-shaped field Small angle of incidence Chief ray angle at mask Total Tack 3

4 Introduction Trend of NA for projection objective ADT & NXE 3100 NEX nm node 8nm node RES HP 45nm 32nm 22nm 16nm 11nm NA NA NA NA NA NA NA NA NA k1 NA * New design forms are needed! * New design strategy is required! 4

5 Introduction What is new in this year s presentation? I Design of co-axial objective systems 1. 6M objective with central obscuration (NA0.5) 2. 8M unobscured objective (NA0.4) 3. 10M objective with central obscuration (NA0.75) II Design of off-axial objective systems 6M unobscured objective (NA0.4) III Design of EUV illuminator 5

6 Grouping Design for EUVL Objective Parameter calculation condition Non-Obstruction condition Obscuration ratio condition Pupil-stop condition Conjugation condition Spherical initial structure Connecting rules Grouping strategy (GS) GS for 6-mirror objective GS for 8-mirror objective GS for 10-mirror objective Basic Group Database Object side group Image side group Obscured image side group Middle two mirrors group Middle four mirrors group 6

Wafer Middle two-mirror group (G2) M3 Middle four-mirror group (G2 )

7 Five Kinds of Mirror Groups Basic Mirror Groups Object side group (G1) MASK M1 M2 Image side group (G3) Wafer Obsc-image group (G3 ) Wafer Middle two-mirror group (G2) M3 Middle four-mirror group (G2 ) M l M m M n M4 M k Basic mirror groups Connect All-sphere initial structure 7

8 6M unobscured objective: Grouping Strategy Mask G1 G3 M2 M1 M3 M6 M5 Wafer G1: M1, M2 G2: M3, M4 G3: M5, M6 M4 G2 6M objective with central obscuration: G1 : M1, M2 G2 : M3, M4 G3 : M5, M6 Mask M2 M4 G1 M1 G2 M3 M6 G3' Wafer M5 8

9 8M unobscured objective Mask M2 G1 M1 M6 M4 Grouping Strategy G2' M3 M5 M8 G3 M7 Wafer 10M objective with central obscuration Mask G1 G1 :M1, M2 G2 :M3, M4, M5, M6 M2 M1 G3 :M7, M8 G3 :M9, M10 M4 G2' G1 :M1, M2 G2 :M3, M4, M5, M6 G3 :M7, M8 M3 M6 M8 M5 G3' M7 G3' M10 M9 Wafer 9

Clearance: The distance between the edge of a mirror and the beam near it.

10 Parameter Calculation Condition Non-obstruction condition: The radius of one mirror can be expressed as a function of the clearance. Clearance: The distance between the edge of a mirror and the beam near it. U ai hai ha0 the slope angle of the upper marginal ray on the ray height of the upper marginal ray on the ray height of the ray beam near Mi 1 M i M i c i h ai ha 0 CLi di U arctan / ai sin( ) hai

11 Parameter Calculation Condition Obscuration Ratio condition: The radius of one mirror can be expressed as a function of the ratio of hole to whole mirror diameter. h ai M i (D i ) -U ai M i+1 (D i+1 ) h adi+1 U ai the slope angle of upper marginal ray of hai height of upper marginal ray of M i hadi M i height of upper marginal ray of the virtual surface D i -d i WDI radio i the diameter ratio of the hole to the mirror M i c i U arctan ( hadi+1 radio ) / (- ) ai i1 hadi+1 hai di = sin h ai 11

12 Parameter Calculation Condition Pupil-stop condition: Surface parameter is the function of the pupil or stop position. STOP hzs chief ray height on Ms U zt M s d s M s M separation between and s 1 Ms 1 d s h zt U zt zzs slope angle of the chief ray on the along optical axial distance of the incident point on Ms M s c s arctan h zs / ds zzs U zt sin( ) hzs

13 Parameter Calculation Condition Conjugation condition: Surface parameters should match the adjacent groups properties (e.g. petzval sum, object-image, Magification, pupil matching). M b l a l b d a l pb l pa M a 1 2 ca ps ps 4B A 2 d A Ml l M l + 2Ml psl l cb ps ca db l b lb1 TT la da lb1 2 2 da 1 la 1 la la 1+ Ml pal pb ps A ps A 4AB A 2 a pb pa pa pb pa pb M ps denotes the magnification of the middle two mirror group denotes the pezval sum of it ps A 2 2 4AB A Mlpb lpa lpam TT M lpb l pa+ 2Mlpb l pa lpbl pa lpbtt B ps M lpa lpb M lpb lpa M lpa lpb

14 Design of co-axial objective systems 6M unobscured objective presented in 2013 EUVL work shop NA 0.3 MAGNIFICATION 1/4 TOTAL TRACK 1530mm NA 0.3 MAGNIFICATION 1/4 TOTAL TRACK 1239mm NA 0.3 MAGNIFICATION 1/4 TOTAL TRACK 1280mm 14

Design of co-axial objective systems 1. 6M objective with central obscuration To enable 11nm node, 6-mirror with central obscuration is one of the solutions. The NA of the objective is around 0.45.

15 Design of co-axial objective systems 1. 6M objective with central obscuration To enable 11nm node, 6-mirror with central obscuration is one of the solutions. The NA of the objective is around Our latest design form G3 is calculated under obscuration ratio condition firstly. G2 is then calculated under non-obstruction condition. To match the ray path of G2 and G3, G1 can be determined under conjugation condition. 15

16 Design of co-axial objective systems Performance Wavelength 13.5nm 13 mm Numerical aperture mm A field of view 13mm 1mm 10:25: M O 0.6 D U L 0.5 A T I O 0.4 N Z Y X New lens from CVMACR O:cvnewlens.seq DIFFRACTION SQ WAVE RESPONSE Ring field 04-Jun-14 DIFFRACTION LIMIT T R 0.9 FIELD ( 5.67 O ) T R 0.9 FIELD ( 5.84 O ) T R 1.0 FIELD ( 6.02 O ) T R 1.0 FIELD ( 6.20 O ) T R 1.0 FIELD ( 6.39 O ) WAVELENGTH WEIGHT 13.5 NM 1 DEFOCUSING SPATIAL FREQUENCY (CYCLES/MM) R T Reduction 8 Total track working distance Chief ray angle on mask Chief ray angle on wafer 1630mm 34mm < Wavefront error (RMS) λ Distortion <1.2nm Pupil obscuration <25% 16

Design of co-axial objective systems Generation of new

Changing the separations of mirrors in G2, new design

To connect G2 and G3, the design forms of G1 will be

17 Design of co-axial objective systems Generation of new design forms Other design forms G3 is fixed. Changing the separations of mirrors in G2, new design forms of G2 will be obtained. To connect G2 and G3, the design forms of G1 will be changed accordingly. A new initial design are obtained by connecting the three groups. 17

18 Design of co-axial objective systems 2. 8M unobscured objective NA 0.4 Reduction 4 TOTAL TRACK 947mm NA 0.4 Reduction 4 TOTAL TRACK 1235mm NA 0.4 Reduction 4 TOTAL TRACK 1274mm 18

19 Design of co-axial objective systems 3. 10M Objective with central obscuration NA 0.7 Reduction 8 TOTAL TRACK 2743mm NA 0.7 Reduction 8 TOTAL TRACK 2743mm 19

20 Design of off-axial objective systems 1. 6M objective off-axial unobscured system Coaxial objective with NA 0.3 NA is increased to 0.4 and obscuration occurs NA 0.4 off-axial objective without obscuration Optimized objective with XYpolynomial surface 20

21 Design of off-axial objective systems Performance 26 mm 1.5mm Wavelength 13.5nm Numerical aperture 0.4 Y Z X 29mm A field of view 26mm 1.5mm Reduction 4 21:39: M O 0.6 D U L 0.5 A T I O 0.4 N Rectangular field New lens from CVMACR O:cvnewlens.seq DIFFRACTION SQ WAVE RESPONSE 14-Jan-14 DIFFRACTION LIMIT Y X (-1.31,-6.11) DEG Y X (-1.31,-6.22) DEG Y X (-1.97,-5.91) DEG Y X (-1.97,-6.01) DEG Y X (-1.97,-6.12) DEG WAVELENGTH WEIGHT 13.4 NM 1 DEFOCUSING X Total track 1263mm working distance 35mm Chief ray angle on mask <6.0 Chief ray angle on wafer 0.18 Wavefront error (RMS) 0.034λ Distortion 1.8nm SPATIAL FREQUENCY (CYCLES/MM) Y 21

Reverse design/ adjusting method for illuminator Reverse design method: Object of the illuminator----exit pupil of objective Stop of the illuminator-----arc shape field Design target: to match IF of

22 Reverse design/ adjusting method for illuminator Reverse design method: Object of the illuminator----exit pupil of objective Stop of the illuminator-----arc shape field Design target: to match IF of given plasma source Para-position for pupil facets and field facets to ensure the illumination uniformity Aperture (Reticle) Exit pupil of illuminator The dummy exit pupil relay2 relay1 Pupil facets Collector R Field facets Y X Source Z 22

The figure of the component is the same. Item Set 1 Set 2 Set 3 Wavelength 13.

23 Reverse design/ adjusting method for illuminator Reverse adjusting method: A adjusting method for illuminator to match objectives with different NA and pupil parameters. Only the position of the component is adjusted. The figure of the component is the same. Item Set 1 Set 2 Set 3 Wavelength 13.5nm Exposure field on the reticle Chief ray angle on the reticle 104mm 6mm, R=119mm 5.52 degree 6 degree 4.9 degree demagnification 1/4 1/4 1/4 NA in image space

24 Reverse design method for illumination system Collector Source IF Field facets The second relay mirror Pupil facets The first relay mirror reticle Exit pupil 90-degree dipole illumination 45-degree quadrupole illumination annular illumination Pupil facets Exit pupil The illumination uniformity is better than 2.5%. 24

Members of our EUV team Yanqiu Li received the MS and PhD degrees in optics from Harbin Institute of Technology.

professor of Tohoku University of Japan, and as a frontier researcher at RIKEN of Japan.

Zhen Cao (Speaker) received the BS degree in optoelectronic information engineering from Xi an Technological University in 2008.

25 Members of our EUV team Yanqiu Li received the MS and PhD degrees in optics from Harbin Institute of Technology. She worked as a director of the micro- and nano-fabrication division at Institute of Electrical Engineering Chinese Academy of Science, as a senior engineer at Nikon, as an invited professor of Tohoku University of Japan, and as a frontier researcher at RIKEN of Japan. She is currently a professor of School of Optoelectronics at Beijing Institute of Technology, Beijing, China. Zhen Cao (Speaker) received the BS degree in optoelectronic information engineering from Xi an Technological University in He is currently works at Beijing Institute of Technology. His current interests include optical system design for EUVL. Fei Liu received the BS degree in measurement and control technology and instruments from Changchun University of Science and Technology in She is currently a PhD candidate directed by Professor Yanqiu Li in the School of Optoelectronics at Beijing Institute of Technology. Her current interests include optical system design for EUVL. 25

Qiuli Mei received her BS degree in optical information science and technology from Wuhan university of technology in 2010.

Her current interests involve design of illumination system and the applications of free form surface in non-imaging optics.

He is currently a PhD candidate directed by Professor Yanqiu Li in the School of Optoelectronics at Beijing Institute of Technology.

26 Qiuli Mei received her BS degree in optical information science and technology from Wuhan university of technology in She is currently a PHD candidate in the School of Optoelectronics at Beijing Institute of Technology. Her current interests involve design of illumination system and the applications of free form surface in non-imaging optics. Yan Liu received the BS degree in Optoelectronic information engineering from Changchun University of Science and technology in He is currently a PhD candidate directed by Professor Yanqiu Li in the School of Optoelectronics at Beijing Institute of Technology. His current interests include optical system design for EUVL. Xinli Liang received the BS degree in optical information science and technology from Nanjing University of Aeronautics and Astronautics in She is currently a MS candidate directed by Professor Yanqiu Li in the School of Optoelectronics at Beijing Institute of Technology. His current interests include design of illumination system for EUVL. 26

27 Acknowledgment This work is supported by National Science and Technology Major Project. 中继镜组视场复眼掩模椭圆聚光镜掠入射镜光阑复眼出瞳 27

28 28

EUVL Activities in China

EUVL Activities in China Yanqiu Li Beijing Institute of Technology (BIT) Phone/Fax: 010-68918443 Email: liyanqiu@bit.edu.cn June 13, 2013 HI Contents Overview of EUVL in China System EUVL Optics EUV Metrology