20151006-tno-euvl-sub-50 nm metrology on euv...
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SUB-50 nm METROLOGY ON EUV
CHEMICALLY AMPLIFIED RESISTA systematic assessment | Diederik Maas
http://dx.doi.org/10.1063/1.4932038
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SUB-50 nm METROLOGY CHALLENGES FROM ITRS
Lithography ITRS 2013: “… there are many metrology challenges that will need to be addressed…”
2 | Sub-50 nm metrology on EUV chemically amplified resist 06 October 2015
2Dand3D
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How about feature size and position metrology?• Precision• Accuracy
Mask Aerial image
GOAL: ASSESS sub-50-nm 2D-Metrology capabilities
of OCD, SEM, HIM and AFM on EUV CAR resist
OutlineTest structure: dense arrays of contact holesSub-50 nm CD metrology challenges ITRSMetrology tools used in the studyResultsSummary
3 | Sub-50 nm metrology on EUV chemically amplified resist 06 October 2015
Dense arrays of Contact HolesEUV resist exposed in ASML NXE:3300Height ~40 nmHalf pitch (HP) 15 – 40 nmCD ≅ HP ± 20%Side wall angle SWA ≅ 70°- 90°(not studied)
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EXTREME-ULTRAVIOLET LITHOGRAPHYProduction of 1:1 pitch CH arrays by ASML using NXE:3300 in a Chemically amplified resist
06 October 20154 | Sub-50 nm metrology on EUV chemically amplified resist
HIM at cross of best energy & best focusAFM at best energy & best focus
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EQUIPMENT USED IN 2D-METROLOGY ASSESSMENT
ON DENSE ARRAYS OF Sub-50-nm CONTACT HOLES
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ASML Yieldstar S-100Scatterometry(OCD)
Bruker FastScan AFMFastScan DX probesPeak force (0.2 nN) tapping mode
Zeiss Orion Plus HIM30 keV He+
iSE signal
Hitachi CD SEM CG4000500 V e-
eSE signal
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CORRELATION OF OCD, HIM, AFM AND CD-SEM
But accuracy? Better understanding of beam-sample interaction needed!
6 | Sub-50 nm metrology on EUV chemically amplified resist 06 October 2015
LCDU
CH CD (CD-SEM) [nm]ΔΔ ΔΔ
CD
[n
m] HIM
OCDAFM
ΔΔΔΔCD with respect to CD-SEM
this CH CD
Investigate images for this CH CD
Good correlation => precision and repro OK
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40 nm HP DCH @ BEST ENERGY AND BEST FOCUS
60 electrons/pixelFrame averaging
7 | Sub-50 nm metrology on EUV chemically amplified resist 06 October 2015
12 ions/pixelsingle frame scan
Peak force (0.2 nN) tapping modeTip shape eroded from AFM image
700 nm Field-of-view
Off-sets in CD significantly larger than
LCDU
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WAVEFORM ANALYSIS FOR CD-SEM, HIM AND AFM
eSE and iSE yield differentHIM vs. SEM: other material & morphology contrastHIM noisier (less primaries)
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WAVEFORM ANALYSIS AFM 24 AND 40 nm HP CH
Peak-force tapping mode allows for repeat imaging without damage to resistErosion needed to arrive at correct CDHigh aspect ratio (HAR) AFM tips needed to assess smallest CHs
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24 nm HP
40 nm HP
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LOCALITY OF SEM AND HIM SIGNAL
Data points: 6 SEM and HIM waveforms, shifted over pitchFitted by double Gaussian
Edge width lower for HIM than for SEM=> iSEs more localized than eSEs
At 24 nm HP SEM waveform is raised between CHs => cross-talk between CHs
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PSEUDO-SE IMAGES (MC CALCULATIONS)
HIM iSE signal more localized than SEM eSE signal
K. Ohya J. Electron Microsc. 53 (2004) 229
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HIMSEM
See also C.G. Frase et al., Model-based SEM for dimensional metrology tasks in semiconductor and mask industry,J. Phys. D: Appl. Phys. 42 (2009) 183001
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FOURIER TRANSFORMS OF 40 nm HP DCH IMAGES
Non-round CH => non-round spectrum
HIM resolved most high spatial frequenciesHIM has highest noise (low pixel dose)
Mask Aerial SEM
HIM AFM
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CORRELATION OF LCDU (3σ) BY CD-SEM AND HIM
LCDU data are extracted from 54 SEM and 54 HIM images
The correlation slope is 1.26 for a R2 of 0.21
Not for every pitch a clear correlation in the LCDU data was found for CD-SEM and HIM.
Postulates why HIM measures higher LCDU/LWRiSEs are more localized => measure at higher spatial frequenciesLCDU/LWR is conserved more, since the shrink is more local
Argument: same shrink found in SEM and HIM image=> resist shrink is due to SEs
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IMAGING THROUGHPUT OCD, SEM, HIM AND AFM
Measurement times this experiment: 700 nm FOV and 1024x1024 pixelsFAB: OCD 0,5 s. (move and measure)FAB: SEM 3 s. (move and measure)LAB: HIM 1 min. (manual move ~50s, 10 s measure)LAB: AFM 7 min. (manual move ~100s, 340 s measure)
Conclusions on TPOCD can do full wafers in-lineSEM can do full wafers off-lineHIM needs engineering but scalable to full wafer, slower than SEMAFM needs >1000x TP boost! (See e.g. poster P-MR-06, Parallel AFM status)
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CONCLUSIONS
OCD, CD-SEM, HIM and AFM all measure precise below 50 nm
CD-SEM image suffers from charging and cross-talk between neighbouring contact holes
HIM iSE signal offers most localized information
AFM metrology of small features needs ultrathin HAR tipNot available below ~20 nm CD (yet)
Quantitative modelling of probe-sample interaction requiredto reach better accuracy
15 | Sub-50 nm metrology on EUV chemically amplified resist 06 October 2015
LCDU
CH CD (CD-SEM) [nm]
ΔΔ ΔΔC
D [
nm
] HIMOCDAFM
ΔΔΔΔCD with respect to CD-SEM
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OTHER EUVL CONTRIBUTIONS FROM TNO
P-RE-01 Improving pattern fidelity in helium ion beam lithography, Wouter Mulckhuyse
P-MR-013D reticle backside inspection, Peter van der Walle
P-MR-04RapidNano: An affordable particle detection platform for EUV mask blanks,
Jacques van der Donck
P-MR-06Parallel AFM Status: Demonstration of 3D metrology and inspection with 1000 times
increase in speed, Hamed Sadeghian
P-MR-08Overlay improvement via large dynamic range scanning probe microscope, Stefan Kuiper
P-OC-01 A traffic light for clean vacuum: The Mass-Filtered Ion Gauge (MFIG), Michel van Putten
P-OC-02 EBL2: EUV exposure and surface analysis system, Edwin te Sligte
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MANY THANKS TO…
17 | Sub-50 nm metrology on EUV chemically amplified resist 06 October 2015
Emile van Veldhoven Rodolf HerfstHamed Sadeghian
Timon FliervoetJeroen MeessenVidya VaenkatesanJan van SchootHarm DillenRoel KnopsAnn de VeirmanFriso Wittebrood
Samuel LeskoPatrick Markus
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THANK YOU FOR
YOUR ATTENTION
http://dx.doi.org/10.1063/1.4932038