Multiple double XTEM sample preparation of site specific ...| 4th Annual Washington DC Area FIB User Group Meeting | L. Gignac, et al. | 2/25/2011 IBM Research | Silicon Science &

IBM Research

Multiple double XTEM sample preparation of site specific sub-10 nm Si nanowires

L. M. Gignac, S. Mittal, S. Bangsaruntip, G. M. Cohen, and J. W. SleightIBM T. J. Watson Research Center, Yorktown Heights, NY

4th Annual Washington DC Area FIB User Group Meeting

February 25, 2011

| 4th Annual Washington DC Area FIB User Group Meeting | L. Gignac, et al. | 2/25/2011

IBM Research | Silicon Science & Process Technology

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Outline§ Si nanowire devicesq “top-down” Si nanowire (NW) process developed at IBM

q work presented at IEDM 2009 (S. Bangsaruntip et al.)

§ Previous work: XTEM-2 sample prepared from XTEM-1 sampleq 30 nm diameter, specific site electrically tested Si nanowire

q presented at Microscopy & Microanalysis 2009 (Gignac et al.)

§ Multiple XTEM samples q <10 nm diameter nanowires

q prepared 4 XTEM samples from 1 XTEM sample

§ Conclusions



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§ “top-down” Si nanowire CMOS deviceq fabricated using Si on Insulator (SOI), electron beam lithography, and semiconductor

processing methods (RIE, wet etching, thin film depositions PVD/CVD/ALD, etc.)

§ Paper presented at Int. Electron Devices Meeting (IEDM) 2009: q “High Performance and Highly Uniform Gate-All-Around Silicon Nanowire MOSFETs with Wire Size

Dependent Scaling,” S. Bangsaruntip, G.M. Cohen, A. Majumdar, Y. Zhang, S.U. Engelmann, N.C.M. Fuller, L.M. Gignac, S. Mittal, J.S. Newbury, M. Guillorn, T. Barwicz, L. Sekaric, M.M. Frank, and J.W. Sleight, IBM T. J. Watson Research Center

Si nanowire CMOS device fabrication

BOX

SOISOISOI

(SiO2) BOX

SOISOI

Si NW

gate dielectrics

poly-Si

(SiO2)

gate



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SEM image of cleaved Si NW



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TEM sections required to understand electrical data1. XTEM along NW:

-measure gate length, Lg

Lg

NW diam.

2. XTEM along NW:-measure NW diameter & shape

Si NW

CuCA

CuCA

source draingate

poly-Si

NiSix

Si NW



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TEM sections required to understand electrical data

It is ideal to have both measurements from 1 XTEM sample

• NW XTEM from XTEM shown at 2010 Washington DC FIB UGM

• now, multiple XTEM samples from 1 XTEM sample• an idea borrowed from atom probe FIB sample prep

Either of these types of X-TEM sections are challenging individually:• NW diameters <30 nm, pitch ~100 nm, gate width < 100 nm• requires state-of-the-art dualbeam FIB and highly skilled operator

NW diam.

Lg



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NW1 NW2 NW3 NW4 NW5 NW6

1 um XTEM-1 sample

In-situ XTEM-1 sample: In-situ lift-outtop down SEM of X-TEM section region


Multiple XTEM’s from 1 XTEM: Si nanowires

XTEM-1sectionplane

region enlarged



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NW 4:• XTEM images• 5 other NW’s in section

Si NWCuCA

CuCA

source drain

gate



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NW 4:• XTEM images• 5 other NW’s in section

Si NWCuCA

CuCA

source drain

10 nmHREM image of Si NW4

Si NW height = 9.4 nm

gate

poly-Si

TaN/Hf-based oxide



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rotate90o

Double XTEM Process:detach sample

from fingerre-attach

sample on top of finger



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XTEM1 TEMe- beam direction

XTEM2 TEM e- beam

direction

Double XTEM Process:



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XTEM-1 front sidegrid

e-beam Pt dep.front side

grid

XTEM-1sample

Omniprobegrid

e-beam Pt coated on NW: front and back

XTEM-1 sample on Omniprobe grid

“backside”



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XTEM-1 front sidegrid

e-beam Pt dep.front side

grid

e-beam Pt coated on NW: front and back

XTEM-1 sample on Omniprobe grid

e-beam Pt dep.back side

grid



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Insitu liftout sample: topdown image as-prepared

OP grid

image TEMsample from

top view



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Insitu liftout sample: topdown image post e-beam Pt depositione-beam Pt on bottom

e-beam Pt on top

OP grid

Insitu liftout sample: topdown image as-prepared

OP grid



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XTEM-1 sample detached from grid post

e-beam view (52o)

10 um

i-beam view (0o)



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XTEM-1 sample detached from grid post

e-beam view (52o)

XTEM-2 samples will be attached to grid postseach grid post was thinned



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attach XTEM-2 sampleNW6 on finger E

sample not completely attached and bent into

the beam when releasing

NW6NW4NW3NW1

NW6NW4NW3NW1



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re-attach XTEM-2 sampleNW4 on finger D

NW4NW3NW1

re-attach XTEM-2 sampleNW3 on finger C

NW3NW1

5 um

re-attach sample NW1 on finger A

NW1



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50 um

grid Cgrid D

TEM samples

TEM samples

2 um

XTEM-2 sample of NW 4: front side (pre-thinning)

XTEM-2 sample buried in ion/e-beam Pt



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ion-beam Pt

e-beam Pt

CuCA

NiSix

Si

Ion beam thinning XTEM-2 (NW4)

NW4

sample sitting on top of Grid finger D

NW4NW3NW1

SiO2

Si



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ion-beam Pt

e-beam Pt

CuCA

NiSix

Si

Ion beam thinning XTEM-2 (NW4)

NiSi2Si

NW4

CuCA

CuM1

SiNW

SiO2

Si

ion-beamPt

e-beamPt

Ga+ beam

sample sitting on top of Grid finger D

X-SEM image

SiO2

Si



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XTEM-2NW 4 on Grid “D”

Si NW in extension

region seen

e-beam Pt

e-beam Pt

Si

SiO2

SiO2

Si NW

2nd side

Si NWin gate

1st side



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NW6 Grid ENW4 Grid D

NW3 Grid CNW1 Grid A

4 XTEM-2 samples prepared from XTEM-1



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NW6 Grid E-missed NW

NW4 Grid DNW3 Grid C

NW1 Grid A


1 um

X-TEM section

sample very thin



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NW6 Grid E-missed NW

NW4 Grid DNW3 Grid CNW1 Grid A

50 nm

Final samples: hit 3 out of 4 Si NW’s

68 nm75 nm66 nm45 nm

13 nm

• original XTEM sample < 80 nm thick• Si damage from sectioning ~13 nm



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poly-Si

TaN /Hf-based

oxide

Si NW

SiO2

10 nm10 nm

NW4 Grid DNW3 Grid CNW1 Grid A

NW height = 9.4 nmNW width = 9.2 nm



Same type of Si NW: +/- 1 nm variation in dimensions



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NW4 Grid D: HR-TEM of same Si NW in both directions!

poly-Si TaN/Hf-based ox

SiSiO2



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NW3 Grid C: HR-TEM of same Si NW in both directions!



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NW1 Grid A



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Conclusions§ multiple XTEM sections from 1 XTEM section has been successfully

demonstrated on sub-10 nm diameter Si nanowiresq 3NW’s were imaged both along and perpendicular to the nanowire direction

q a forth sample was prepared but the NW location was not hit

q high resolution TEM images were taken of the same wire in both directions

§ this technique demonstrated X-TEM sectioning of features only 1.1 um apartq this small sample pitch is the result of having a thin TEM sample to section

§ Si damage layer from X-TEM 1 was 13 nm on both sides of sample

§ TEM sample is seen to be bent up at edgeq due to stress from the e-beam Pt deposition

q due to bending in final thinning of X-TEM 1

§ Si NW diameter: q W = 9.2 ! 0.9 nm, H = 8.6 ! 0.6 nm

§ paper submitted for review in Microscopy & Microanalysis

Documents

Multiple double XTEM sample preparation of site specific ...| 4th Annual Washington DC Area FIB User Group Meeting | L. Gignac, et al. | 2/25/2011 IBM Research | Silicon Science &