SUB-50 nm METROLOGY ON EUV

CHEMICALLY AMPLIFIED RESISTA systematic assessment | Diederik Maas

http://dx.doi.org/10.1063/1.4932038

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

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)

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

EQUIPMENT USED IN 2D-METROLOGY ASSESSMENT

ON DENSE ARRAYS OF Sub-50-nm CONTACT HOLES

5 | Sub-50 nm metrology on EUV chemically amplified resist 06 October 2015

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

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

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

WAVEFORM ANALYSIS FOR CD-SEM, HIM AND AFM

eSE and iSE yield differentHIM vs. SEM: other material & morphology contrastHIM noisier (less primaries)

8 | Sub-50 nm metrology on EUV chemically amplified resist 06 October 2015

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

9 | Sub-50 nm metrology on EUV chemically amplified resist 06 October 2015

24 nm HP

40 nm HP

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

10 | Sub-50 nm metrology on EUV chemically amplified resist 06 October 2015

PSEUDO-SE IMAGES (MC CALCULATIONS)

HIM iSE signal more localized than SEM eSE signal

K. Ohya J. Electron Microsc. 53 (2004) 229

11 | Sub-50 nm metrology on EUV chemically amplified resist 06 October 2015

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

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

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

13 | Sub-50 nm metrology on EUV chemically amplified resist 06 October 2015

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)

14 | Sub-50 nm metrology on EUV chemically amplified resist 06 October 2015

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

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

16 | Sub-50 nm metrology on EUV chemically amplified resist 06 October 2015

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

THANK YOU FOR

YOUR ATTENTION

http://dx.doi.org/10.1063/1.4932038