Source Aperture Lithography Handbook Partial Coherence Minimum feature size Condenser of Illumination (resolution) Lens σ = sinθ /sinθ c o MFS = k λ/NA ≈ 1 k1 0.8 Mask (resist/enhancements) Depth of Focus
DOF = k λ/(NA)2 ≈2 Projection k1 1 Numerical Lens (enhancements) θ θ Aperture c o NA=sinθ o Wafer
optrev.fm WHAT A DEEP-UV STEPPER REALLY LOOKS LIKE
optlitho.doc “WAVEFRONT ENGINEERING” TECHNIQUES IN PHOTOLITHOGRAPHY
Modified Illumination
Light Source conventional annular quadru Effective pole Source Phase Shifting
Mask Condenser Lens Phase 0 π 0 π 0 alternate attenuated Mask Pupil Filtering Projection Pupil Function Lens Phase Distribution Aperture Multiple Exposure (Pupil)
FLEX Wafer
Wafer Enhanced Resists Stage Surface Imaging New Image Formation Exposure Optics Techniques
optrev.fm PHASE-SHIFT MASK TECHNIQUES
mask mask structure structure
amplitude amplitude E-field E-field at mask at mask
intensity intensity on wafer sidelobe on wafer
Alternating phase mask Attenuated phase mask (Levenson)
optrev.fm VACUUM ULTRAVIOLET TRANSMISSION CUTOFFS OF AVAILABLE OPTICAL MATERIALS
2-3 mm thick
UC Berkeley Stanford NSF/SRC-ERC: LITHOGRAPHY FOR 100 nm AND BEYOND MIT CONTINUED EXTENSION OF OPTICAL PROJECTION
λ • Historical approach: (MFS = k1 /NA) ⇒ Increase NA ⇒ Decrease λ ⇒ Decrease k1 • Transmission optics reach to 193 nm ≈ 0.75, ≈ 0.5 ⇒ ≈ - Expect limiting NA k1 MFS 130 nm • What about Vacuum UV? (λ = 100 nm - 200 nm range) - Diminishing returns absent further NA increase
srcjb96.doc 1996 SRC Lithography Review J. Bokor
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R E BE · · ·1 8 6 8· OPTICAL LITHOGRAPHY IN THE FUTURE OPTICAL LITHOGRAPHY TODAY (1997) 100 nm → 30 nm FEATURE SIZE 0.25 µm FEATURE SIZE
DUV (248 nm), Catadioptric optics EUV (13 nm), All-reflective optics, Reflection mask EUVL ENGINEERING TEST STAND
DARPA/SRC Network for Advanced Lithography J. Bokor 6 ILP 3/12/98 1997 Resist / EUVL Imaging Status
TSI process No crosslinker Etch selectivity 45:1
70 nm lines
70 nm lines/spaces (2:1 pitch) Coded for 70nm 15.6 mJ/cm2 dose 10x microstepper
7 J. Bokor Dec. 9, 1997 IEDM Lithography Panel EUVL Trend
10 1 LithographyLithography “Laws”“Laws” • CD = k *l/NA • CD = k11*l/NA ••DOFDOF = = 1.2* 1.2*ll/NA/NA22
m) NA (k1=0.3) NA m 1 NA (k1=0.7) 0.1 DOF(k1=0.3) DOF(k1=0.7) DOF ( “k factor” “k11 factor” Conventional: k = 0.7 Conventional: k11 = 0.7 Strong PSM: k = 0.3 0.1 0.01 Strong PSM: k11 = 0.3 100 10 CD (nm)
J. Bokor UC Berkeley