Photolithography 光刻 Part I: Optics

Transcription

1 微纳光电子材料与器件工艺原理 Photolithography 光刻 Part I: Optics Xing Sheng 盛兴 Department of Electronic Engineering Tsinghua University 1

2 Integrate Circuits Moore's law transistor number transistor size 5

3 Transistor size s 1 cm ~ 2 mm < 100 nm revolution evolution 6

4 CMOS Process 'Lithography is the cornerstone of modern IC technology' ---- Silicon VLSI, Plummer et al., 7

5 Lithography litho- 石头 -graph 图案 8

6 Photography 曝光 显影 打印 9

7 Photolithography( 光刻 ) Xing Sheng, EE@Tsinghua 10

8 Photolithography( 光刻 ) Video 光刻胶 光源 掩膜 11

9 Exposure ( 曝光 ) 接触式接近式投影式 12

10 Exposure ( 曝光 ) stepper ( 步进投影 ) Video mass chip production in industry 13

11 Resolution ideal case actual case 14

12 Resolution the smaller, the harder 15

13 Resolution diffraction: light is a wave! 16

14 Resolution contact and proximity mode R resolution wavelength g gap size R ~ g smaller, g ---> smaller R UV, DUV, EUV, x-ray,... g minimum: resist film thickness 17

15 projection mode Resolution 18

16 Resolution ideal MTF = 1 poor MTF ~ 0 MTF =? modulation transfer function (MTF) MTF I I max max I I min min 19

17 Resolution diffraction pattern (Airy's disk) 20

18 Resolution 21

19 Resolution resolution smaller, larger NA ---> smaller resolution UV, DUV, EUV, x-ray,... n refractive index (air: 1, oil: 1.4~1.7) sin maximum =

20 Depth of Focus (DOF) Xing Sheng, off focus on focus off focus trade-off between resolution and DOF 23

21 Depth of Focus (DOF) Xing Sheng, 24

22 Spatial Coherence 25

23 Resolution Improvement Xing Sheng, R ~ nsin reduce increase n??? 26

24 Immersion Lithography Xing Sheng, R ~ nsin n > 1.0 n = 1.0 high index fluid n = 1.7 resolution is reduced by ~40% 27

25 Phase Shift Mask 28

26 Double Patterning 29

27 Optical Proximity Correction (OPC) mask resist 30

28 Photomasks ( 掩膜 ) 31

29 Photomasks ( 掩膜 ) Layout design CAD tools see examples Example Transparency film flexible mask design layout Chrome mask glass substrate chrome coating transparency film chrome mask 32

30 Photomasks ( 掩膜 ) write by laser or Ebeam 33

31 Mercury (Hg) arc lamp Light Sources g-line 436 nm, h-line 405 nm, i-line 365 nm R ~ nsin 34

32 Light Sources Mercury (Hg) arc lamp g-line 436 nm, h-line 405 nm, i-line 365 nm yellow light in cleanroom 35

33 Light Sources Deep UV (DUV) excimer lasers, KrF (248 nm), ArF (193 nm) R ~ nsin Extreme UV (EUV) X-ray Tin (Sn) plasma lasers, 13.5 nm 0.01 ~ 10 nm Electron beam (E-beam)... 36

34 Optics for EUV quartz glass metals air at EUV: glass is not transparent metal is not reflective even air is absorptive 37

35 Optics for EUV multilayer mirrors (Mo/Si) reflective masks 38

36 Optics optical loss > 95% UV (365 nm) EUV (13.5 nm) 39

37 Equipment UV (365 nm) resolution ~ 2 m price ~ 200,000 RMB EUV (13.5 nm) resolution ~ 10 nm price ~ 100,000,000 $$$ 40

38 wavelength 0.1~10 nm X-ray Lithography 41

39 Electron Beam (Ebeam) Lithography similar to a scanning electron microscope (SEM) proximity effect 42

40 Wavelength example: for V = 30 kv, = nm The resolution is limited by secondary electrons resolution ~ 10 nm No mask for electron, only direct writing! Xing Sheng, EE@Tsinghua Electron Beam (Ebeam) Lithography ( nm) 1.23 "To cover the 700 cm 2 surface area of a 300 mm silicon wafer, the minimum write time would extend to 7*10 8 seconds, about 22 years." - Wikipedia Only for research purposes now V 43

41 NanoPhotonics 44

42 Optical Cloak J. Valentine, et al., Nature Mater. 8, 568 (2008) 45

43 Metalens 40 m 300 nm M. Khorasaninejad, et al., Science 352, 1190 (2016) 46

44 Thank you for your attention 48