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 xingsheng@tsinghua.edu.cn 1
Integrate Circuits Moore's law transistor number transistor size 5
Transistor size 1947 1961 2000s 1 cm ~ 2 mm < 100 nm revolution evolution 6
CMOS Process 'Lithography is the cornerstone of modern IC technology' ---- Silicon VLSI, Plummer et al., 7
Lithography litho- 石头 -graph 图案 8
Photography 曝光 显影 打印 9
Photolithography( 光刻 ) Xing Sheng, EE@Tsinghua 10
Photolithography( 光刻 ) Video 光刻胶 光源 掩膜 11
Exposure ( 曝光 ) 接触式接近式投影式 12
Exposure ( 曝光 ) stepper ( 步进投影 ) Video mass chip production in industry 13
Resolution ideal case actual case 14
Resolution the smaller, the harder 15
Resolution diffraction: light is a wave! 16
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
projection mode Resolution 18
Resolution ideal MTF = 1 poor MTF ~ 0 MTF =? modulation transfer function (MTF) MTF I I max max I I min min 19
Resolution diffraction pattern (Airy's disk) 20
Resolution 21
Resolution resolution smaller, larger NA ---> smaller resolution UV, DUV, EUV, x-ray,... n refractive index (air: 1, oil: 1.4~1.7) sin maximum = 1.0 22
Depth of Focus (DOF) Xing Sheng, EE@Tsinghua off focus on focus off focus trade-off between resolution and DOF 23
Depth of Focus (DOF) Xing Sheng, EE@Tsinghua 24
Spatial Coherence 25
Resolution Improvement Xing Sheng, EE@Tsinghua R ~ nsin reduce increase n??? 26
Immersion Lithography Xing Sheng, EE@Tsinghua R ~ nsin n > 1.0 n = 1.0 high index fluid n = 1.7 resolution is reduced by ~40% 27
Phase Shift Mask 28
Double Patterning 29
Optical Proximity Correction (OPC) mask resist 30
Photomasks ( 掩膜 ) 31
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
Photomasks ( 掩膜 ) write by laser or Ebeam 33
Mercury (Hg) arc lamp Light Sources g-line 436 nm, h-line 405 nm, i-line 365 nm R ~ nsin 34
Light Sources Mercury (Hg) arc lamp g-line 436 nm, h-line 405 nm, i-line 365 nm yellow light in cleanroom 35
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
Optics for EUV quartz glass metals air at EUV: glass is not transparent metal is not reflective even air is absorptive 37
Optics for EUV multilayer mirrors (Mo/Si) reflective masks 38
Optics optical loss > 95% UV (365 nm) EUV (13.5 nm) 39
Equipment UV (365 nm) resolution ~ 2 m price ~ 200,000 RMB EUV (13.5 nm) resolution ~ 10 nm price ~ 100,000,000 $$$ 40
wavelength 0.1~10 nm X-ray Lithography 41
Electron Beam (Ebeam) Lithography similar to a scanning electron microscope (SEM) proximity effect 42
Wavelength example: for V = 30 kv, = 0.007 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
NanoPhotonics 44
Optical Cloak J. Valentine, et al., Nature Mater. 8, 568 (2008) 45
Metalens 40 m 300 nm M. Khorasaninejad, et al., Science 352, 1190 (2016) 46
Thank you for your attention 48