LITHOGRAPHY STEPPER OPTICS - EECS Instructional...
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optrev.fm LITHOGRAPHY STEPPER OPTICS θ o Source Aperture Condenser Lens Mask Projection Lens Wafer Numerical Aperture NA=sinθ o Lithography Handbook Minimum feature size (resolution) MFS = k 1 λ/NA k 1 ≈ 0.8 (resist/enhancements) Depth of Focus DOF = k 2 λ/(NA) 2 k 1 ≈ 1 (enhancements) θ c Partial Coherence σ = sinθ c /sinθ o of Illumination
Transcript of LITHOGRAPHY STEPPER OPTICS - EECS Instructional...
LITH
Lithography Handbook
imum feature size(resolution)
MFS = k1λ/NAk1 ≈ 0.8
ist/enhancements)
Depth of Focus
OF = k2λ/(NA)2
k1 ≈ 1 enhancements)
u
optrev.fm
NumApeNA=
PartiCohe
σ = sof Ill
OGRAPHY STEPPER OPTICS
θo
Source
Aperture
CondenserLens
Mask
ProjectionLens
Wafer
ericalrturesinθo
Min
(res
D
(θc
alrence
inθc/sinθo
mination
optlitho.doc
WHAT A DEEP-UV STEPPER REALLY LOOKS LIKE
optrev.fm
“WAVEFRONT ENGINEERING” TECHNIQUES IN PHOTOLITHOGRAPHY
Modified Illumination
Phase Shifting
Pupil Filtering
Multiple Exposure
Enhanced Resists
conventional annular quadru pole
Mask
Phase 0 π 0 π 0 alternate attenuated
PupilFunction
Phase Distribution
FLEX
Surface Imaging
Light Source
EffectiveSource
CondenserLens
Mask
ProjectionLens
Aperture(Pupil)
Wafer
WaferStage
New Image FormationTechniques
Exposure Optics
optrev.fm
PHASE-SHIFT MASK TECHNIQUES
maskstructure
amplitudeat mask
intensityon wafer
maskstructure
amplitudeat mask
intensityon wafer
E-field E-field
sidelobe
Alternating phase mask(Levenson)
Attenuated phase mask
NSF/SRC-ERC: LITHOGRAPHY FOR 100 nm AND BEYOND
UC Berkeley
StanfordMIT
VACUUM ULTRAVIOLET TRANSMISSION CUTOFFSOF AVAILABLE OPTICAL MATERIALS
2-3 mm thick
srcjb96.doc 1996 SRC Lithography Review J. Bokor
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RS I T Y • O F • C
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•1868•
LET TH
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LI G H T ELECTRONICS RESEARCH LAB, UNIVERSITY OF CALIFORNIA, BERKELEY
CONTINUED EXTENSION OF OPTICAL PROJECTION
• Historical approach: (MFS = k1λ/NA)
⇒ Increase NA
⇒ Decrease λ⇒ Decrease k1
• Transmission optics reach to 193 nm
- Expect limiting NA ≈ 0.75, k1 ≈ 0.5
• What about Vacuum UV? (λ = 100 nm - 200 nm range)
- Diminishing returns absent further NA increase
⇒ MFS ≈ 130 nm
OPTICAL LITHOGRAPHY TODAY (1997)
DUV (248 nm), Catadioptric optics
0.25 µm FEATURE SIZE
OPTICAL LITHOGRAPHY IN THE FUTURE
EUV (13 nm), All-reflective optics,Reflection mask
100 nm → 30 nm FEATURE SIZE
J. BokorILP 3/12/986
DARPA/SRC Network for Advanced Lithography
EUVL ENGINEERING TEST STAND
J. Bokor Dec. 9, 1997 IEDM Lithography Panel7
70 nm lines/spaces (2:1 pitch)Coded for 70nm15.6 mJ/cm2 dose10x microstepper
70 nm lines
TSI processNo crosslinkerEtch selectivity 45:1
1997 Resist / EUVL Imaging Status
J. BokorUC Berkeley
EUVL Trend
0.01
0.1
1
10100
CD (nm)
NA
0.1
1
10
DO
F (
µm
)
NA (k1=0.3)
NA (k1=0.7)
DOF(k1=0.3)
DOF(k1=0.7)
Lithography “Laws”
• CD = k1*λ/NA
• DOF = 1.2*λ/NA2
Lithography “Laws”
• CD = k1*λ/NA
• DOF = 1.2*λ/NA2
“k1 factor”
Conventional: k1 = 0.7
Strong PSM: k1 = 0.3
“k1 factor”
Conventional: k1 = 0.7
Strong PSM: k1 = 0.3
