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SelfSelf--assembled assembled monolayersmonolayers: surface : surface engineering and characterizationengineering and characterizationC.M. Whelan*, T. Fernandez Landaluce#, A. Caro Maestre,
V. Sutcliffe# and Fabrice SinapiIMEC, Kapeldreef 75, B-3001 Leuven, Belgium.
J. Ghijsen and J.-J. PireauxLISE, FUNDP, Namur, Belgium.
M. de Ridder and H.H. BrongersmaCalipso B.V., Eindhoven, The Netherlands.
*Corresponding author. E-mail: whelan@imec.be#Texas Instruments assignee at IMEC.Current address: #Materials Science Centre, University of Groningen, The Netherlands.
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 2
Self-assemblyspontaneous
chemisorption of active surfactant on a solid from
gas/liquid phase
Terminal functional groupexposed SAM-gas/liquid interfacemethyl, phenyl, amine, carboxylic acid, alcohol, …
Head groupbonding to specific substrate sites thiol/metals, silane/SiO2, acid/metal oxide
SAMsSAMs: surfaces : surfaces ““mademade--toto--orderorder””
Self-assembled monolayersmonomolecular organic film
Hydrocarbon segmentslateral interactions and tilt to minimise free volumegenerally alkyl chains with VdWs interactions
CH3
(CH2)n
SCu
18.4 Å2θ ~ 12°
Organic surfaces ‘made-to-order’
‘pseudo-(100)’ octanethiolate on Cu(111)1
1F. Schreiber, Prog. Surf. Sci. 65 (2000) 151
Composition controls structure and chemistry Manipulate atomic scale propertiesEngineer surfaces and interfaces
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 3
OutlineOutline
ALD of WCxNy/various-SAMs
Atomic layer depositionSAM compatibility with ALDEffect of SAM termination Influence of alkyl chain length
SAMs as Cu diffusion barrier
Previous workAdhesion & Cu silicide formation
Characterization of Cu/CO2H-SAM
LEIS: SAM outer most surfaceXPS: SAM-metal bonding
Conclusions
Application of SAMs in Nanoelectronics: surface engineering
Passive
Active
Characterization
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 4
ALD depends on surface chemistry1 - combination of precursors and their sequence and the type and density of reactive substrate surface sites
For interconnect metallization - ALD of WCxNy as Cu diffusion barrier form on low-k substrates2
WF6 + NH3 + B(C2H5)3 + surface groups → WCxNy
Selective (enhance/inhibit) WCxNy ALD - identify favourable/unfavourable surface groupsusing monofunctionalised surfaces
1Puurunen R.L., J. Appl. Phys. 97 (2005) 121301.2Martin Hoyas et al., J. Appl. Phys., 95 (2004) 381.
Use self-assembled monolayers as model substrates for studying ALD processes
Atomic Layer Deposition (ALD) for interconnect Atomic Layer Deposition (ALD) for interconnect metallization in IC technologymetallization in IC technology
IBM, 2002Bell Labs,1947
Shrinking dimensions → Al/SiO2 → Cu/low-k → conformal Cu diffusion barrier → ALD
Scaling requires newmaterials and processes
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 5
ExperimentalExperimental
ALD/SAM preparationSubstrate : SiO2 /Si(100)1
ALD : WCxNy from triethylborane (TEB), tungsten hexaflouride and ammonia at 300ºCSAM : alkyltrichlorosilanes ALCVDTM Pulsar® 2000 reactor
ASM PolygonTM 8200
SAM precursor X(CH2)nYterminal group X = CH3, Br, CNCH2 chain length n = 7-17head group Y = SiCl3
alkyltrichlorosilanes CH3-Cn-SAM CH3(CH2)nSiCl3n=7,9,10,11,15,17,21
bromoundecyltrichlorosilane Br-C11-SAM Br(CH2)11SiCl3cyanoundecyltrichlorosilane CN-C11-SAM CN(CH2)11SiCl3
ALD ALD WCWCxxNNyy::
ALCVDTM Pulsar® 2000 reactor integrated with an automated wafer handling platform (ASM PolygonTM 8200). A precursor (mixed with a nitrogen carrier gas flow) pulse sequence of (C2H5)3B, WF6, and NH3 represents one deposition cycle. Excess precursor gas was removed by flowing nitrogen after each precursor pulse. The deposition temperature was 300ºC.
Analysis:Analysis:H2O contact angle, XPS, TDS, Rs, XRF, ellipsometry, AFM, SEM, EF-TEM, TOF-SIMS, XRR, AES
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 6
ExperimentalExperimental
ALD ALD WCWCxxNNyy::
ALCVDTM Pulsar® 2000 reactor integrated with an automated wafer handling platform (ASM PolygonTM 8200). A precursor (mixed with a nitrogen carrier gas flow) pulse sequence of (C2H5)3B, WF6, and NH3 represents one deposition cycle. Excess precursor gas was removed by flowing nitrogen after each precursor pulse. The deposition temperature was 300ºC.
Analysis:Analysis:H2O contact angle, XPS, TDS, Rs, XRF, ellipsometry, AFM, SEM, EF-TEM, TOF-SIMS, XRR, AES
SiO2
Si
Si
O
O O
CH3 CH3
OO SiSi
CH3
Si
CH3
O
O O O
SiCl
Cl
Cl
CH3
H2O
CH3
OH
OH
OH Si
SiO2/Si(100) immersed in 10-3 M in toluene 1 hr. Rinsed with toluene, acetone, ethanol. Dried under nitrogen flow.
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 7
1Kluth et al., Langmuir, 13 (1997) 3775.2Whelan et al., Mat. Res. Soc. Symp. Proc., 812 (2004) F2.2.1.
SAM compatibility with ALD: MeSAM compatibility with ALD: Me--CCnn--SAM thermal stability SAM thermal stability TDS masses 11TDS masses 11--100100
M=40
0
4000
8000
12000
0 200 400 600 800 1000
Temperature (C)
Cou
nt ra
te (c
ps)
C8
C12 (Specimen2)
C16 (Specimen2)SiO2 (Specimen 2)
YYYYY96-98
YYYYY79-85
YYYYY66-71
YYYYY53-58
YYYYY47
YYYYY39-43
YYYYYes26-29
1715119n=7MassRange
All CH3-Cn-SAMs (n = 7-17) show :No water desorptionLeading edge ~ 500°CMaximum 600°C
Decomposition 470-690ºCFor fixed n, substitution of CH3 with Br or CN reduces thermal stability2
Previous EELS study in vacuum of decomposition mechanism for n=3,7,171
Stable to 470°C C-C bond cleavage → HC desorptionCreates surface CH3-Si groups to 620°CSiloxane head groups to 830°C
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 8
SAM compatibility with ALD: WCSAM compatibility with ALD: WCxxNNyy/Br/Br--CC1111--SAMSAMContact angle, XPS, TDSContact angle, XPS, TDS
XPS composition analysis of Br-UTS SAMs before and after WCxNy ALD. ALD cycles O % C % Siox% Sisubstrate% Br % W % N %
0 26.77 40.35 11.9 18.8 2.0 50 33.15 42.2 9.8 13.5 0.46 0.79
100 41.95 44.08 3.5 4.2 6.23 200 41.75 41.29 11.13 5.80 500 43.17 36.15 13.21 7.37
XPS composition analysis of Br-C11-SAM before and after WCxNy ALD
Water contact angle for as-prepared Br-C11-SAM86.2 ± 1.2° literature86.6 ± 1.5° experimental
All SAMs show:
Well-ordered surfaces with expected terminationNo chlorine presentDesorption maximum 550-600°CSurvive multiple ALD cycles
Suitable model substrates for studying ALD of WCxNy
200 ALD cycles/Br-C11-SAM
50 ALD cycles/SiO2
0
1000
2000
3000
4000
5000
6000
7000
200 ALD cycles/SiO2
Mas
s 68
inte
nsity
(a.u
.)
0 200 400 600 800
50 ALD cycles/Br-C11-SAM
Temperature (degrees C)
Br-C11-SAM
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 9
Effect of SAM termination on Effect of SAM termination on WCWCxxNNyy growth: W content growth: W content XRFXRF
0 200 400 600 800 1000 1200 1400
W (a
tom
s cm
-2)
0 200 400 600 800 1000 1200 1400
CN-C11-SAM
0 200 400 600 800 1000 1200 1400
CH3-C10-SAM
0 200 400 600 800 1000 1200 1400
SiO2
0 200 400 600 800 1000 1200 14000
1x1017
2x1017
3x1017
4x1017
5x1017
6x1017
Br-C11-SAM
No. of WCxNy ALD cycles
Initial non-linear growth Transient regimeWCxNy/substrate
Linear regimeWCxNy/ WCxNy
1 CPS = 2.70E+15 atoms 1.11E+15 atoms = 1 MLE
Initial non-linear growth on all SAMsLinear growth regime from 100-200 cycles for C10 & C11 SAMsGrowth on CN-terminated SAM favoured
CH3-C17-SAM
W (M
LE)
CN-C11-SAM
CH3-C10-SAM
SiO2
0 200 4000.0
5.0x101
1.0x102
1.5x102
2.0x102
Br-C11-SAM
No. of WCxNy ALD cycles
Effect of terminal group but also influence of alkyl
chain length?
Off-set from linearity
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 10
Influence of SAM alkyl chain length on Influence of SAM alkyl chain length on WCWCxxNNyy growth: growth: selectivity selectivity XRF XRF
0 100 200 300 400 5000
200
400
600
800
1000
1200
1400
CH3-C17-SAM CH3-C15-SAM CH3-C11-SAM CH3-C9-SAM CH3-C7-SAM
W (a
tom
nm
-2)
No. WCxNy ALD cycles
Transient regimeoffset
6 8 10 12 14 16 180
50
100
150
200
250
W (a
tom
nm
-2) @
150
ALD
cyc
les
n
0 100 200 300 400 5000
200
400
600
800
1000
1200
1400
CH3-C17-SAM CH3-C15-SAM CH3-C11-SAM CH3-C9-SAM CH3-C7-SAM
W (a
tom
nm
-2)
No. WCxNy ALD cycles
Selectivity for WCxNygrowth varies with n
Offset from linearity increases with increasing chain length
C17 most crystalline with few defects available for metal nucleation –retarding film growth
C7 least ordered SAM with higher population of defects available for metal nucleation
But defects unlikely to be linear over n = 7 to 17
CH3(CH2)nSiCl3
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 11
Influence of SAM alkyl chain length on Influence of SAM alkyl chain length on WCWCxxNNyy growth: growth: mechanism mechanism AFMAFM
+ 500
CH3-C15-SAM
After cycles of ALD WCxNy
+ 200 + 500
+ 100
As-prepared
Islanding growth mechanism Constant island densityLateral and vertical growth before coalescence
Same for all CH3-Cn-SAM with chain length dependent offset
100 X 100 nm2
-0.2
0.2
0.6
1
1.4
1.8
-50 50 150 250 350 450 550ALD cycles
RM
S (n
m)
CH3-C7-SAM
CH3-C11-SAM
CH3-C15-SAM
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 12
0 100 200 300 400 5000
200
400
600
800
1000
1200
1400
CH3-C11-SAM CH3-C7-SAM CN-C11-SAM
W (a
tom
nm
-2)
No. WCxNy ALD cycles
Influence of SAM alkyl chain length Influence of SAM alkyl chain length vs.vs. terminal terminal group on group on WCWCxxNNyy growth: selectivity growth: selectivity XRFXRF
Selectivity for WCxNy growth varies with n BUT influence of n not
exclusive CN-C11-SAM
vs.
CH3-C11-SAM CN-C11-SAM similar to CH3-C7-SAM shows terminal group enhancement
of growth
Both terminal group and alkyl chain length determine WCxNy
growth behaviour
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 13
(1) ALD/SAM: conclusions(1) ALD/SAM: conclusionsSilane SAMs investigated as model substrates for WCxNy ALD for : SiCl3 head group, chain lengths (n = 7-17) and terminal groups (CH3, CN, Br)
SAMs stable to >470°C and present after multiple 300°C ALD cycles
SAM termination effects WCxNy growth : CN-termination favouredCN-, Br- & CH3-terminated C10 & C11-SAM vs. CH3-C17 SAM
Selectivity for WCxNy growth varies with n due to thickness rather than structural defects within the SAMs
Both terminal group and alkyl chain length determine WCxNy growth behaviour
SAMs provide suitable model substrates for studying metal deposition
Vary substrate structure (alkyl chain) & chemistry (terminal group) to selectively control growth
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 14
OutlineOutline
ALD of WCxNy/various-SAMs
Atomic layer depositionSAM compatibility with ALDEffect of SAM termination Influence of alkyl chain length
SAMs as Cu diffusion barrier
Previous workAdhesion & Cu silicide formation
Characterization of Cu/CO2H-SAM
LEIS: SAM outer most surfaceXPS: SAM-metal bonding
Conclusions
Application of SAMs in Nanoelectronics: surface engineering
Passive
Active
Characterization
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 15
Previous work Previous work SAMsSAMs as Cu diffusion barrier as Cu diffusion barrier 1Krishnamoorthy, Appl. Phys. Lett., 78 (2001), 2Ramanath, Appl. Phys. Lett. 83 (2003)
Cu diffusion barrier properties chain length & terminal group dependent1
Most promising candidate, SAM-SH, enhances Cu-SiO2adhesion & acts as Cu diffusion barrier2
No chain, bulky head group
Chain, no bulky head group
Chain and bulky head group
Chain and bulky head group with reactive heteroatomSAM1
SAM2
SAM3
SAM4
Cu seed layerevaoporated
diffusion barrier
bulk Cu (electroplated)
Si
Cu interconnect structure
SiO2
SAM1 SAM2 SAM3 SAM4
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 16
Concept: Concept: seleciveselecive process for process for DD integrationDD integrationC.M. Whelan, V. Sutcliff, U.S. Patent 2006/0128142 A1, European Patent 1 670 054 A1
SAM-Ssacrifical: CH3(CH2)9SHSAM-Bbarrier: HS(CH2)3Si(OCH3)3
Si(OCH3)3-SiO2
HS-Cu
Cu
SiO2
SAM-B
Cu
SiO2Si(OCH3)3-SiO2
HS
CH3
HS-Cu
SAM-S
SAM-B
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 17
Concept: Concept: seleciveselecive process for process for DD integrationDD integrationC.M. Whelan, V. Sutcliff, U.S. Patent 2006/0128142 A1, European Patent 1 670 054 A1
SAM-Ssacrifical: CH3(CH2)9SHSAM-Bbarrier: HS(CH2)3Si(OCH3)3
Si(OCH3)3-SiO2
HS-Cu
Cu
SiO2
SAM-B
Cu
SiO2Si(OCH3)3-SiO2
HS
CH3
HS-Cu
SAM-S
SAM-B
SAM-S thermal release
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 18
Assessment of Assessment of SAMsSAMs with systematic variation of with systematic variation of molecular structuremolecular structure
Same terminal & head groups but different chain lengths
CH3(CH2)nSiCl3 where n = 7,9,10,11,15,17,21
Same terminal & chain length but different head group
CH3(CH2)17SiX3 where X = Cl3, Cl2(OCH3), (OCH3)3
Same head group & chain length but different terminal group
CH3(CH2)11SiCl3 vs. CN(CH2)11SiCl3 vs. Br(CH2)11SiCl3SH(CH2)3Si(OCH3)3 vs. NH2(CH2)3Si(OCH3)3 vs. C5H4N(CH2)2Si(OCH3)3
Longer chain length (CH2)n for improved film order & Cu blocking efficiency
New head group -SiCl3 for improved adhesion, coverage-packing density & thermal stability
SH(CH2)n>6SiCl3 not commercially available
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 19
SiO2/CN-SAM/CuN 1s peaks Cu and the SiO2 sideStrong head group-SiO2 & CN-Cu bonding
SiO2/Br-SAM/CuBr 3d peaks Cu sideWeak head group-SiO2 & strong Br-Cu bonding
SiO2/SH-SAM/Cu
S 2p peaks Cu sideWeak head group-SiO2 & strong S-Cu bonding
Cu-SH = Br > CNSH-SAM failure at oxide in agreement with literature
4 points bending probe: fracture surface analysis4 points bending probe: fracture surface analysis
P.G. Ganesan et al., Mater. Sci. Forum 426-432 (2003) 3487, G. Ramanath et al. Appl. Phys. Lett. 83 (2003) 383
Cu/SH-SAM/SiO2structures delaminate at SAM/SiO2interfaceS atoms strongly bound to Cu & Si(OCH3)3 easily detach from the SiO2 surface
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 20
A crude look at Cu/A crude look at Cu/SAM/SiOSAM/SiO2 2 barrier properties: barrier properties: visual inspectionvisual inspection
SH
NH2
blank
Pyridine
325
300
375
350
SHPyridine
Cu
Pyridine
NH2
SH
Cu
Cu
SH
Pyridine
NH2
NH2
Annealing Temp. (°C)
HNC5H4CH2Si(OCH3)3
H2N (CH2)3Si(OCH3)3
HS(CH2)3Si(OCH3)3
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 21
0
50
100
150
200
250
300
0 200 225 250 275 300
Temperature
Shee
t rsi
stan
ce
Si/SiO2/MPTMS/Cu Recipe I UV-O3cleaning
Si/SiO2/Cu Recipe I UV-O3cleaning
A crude look at Cu/A crude look at Cu/SAMSAM--B/SiOB/SiO2 2 barrier properties: barrier properties: RRss vs.vs. temperaturetemperature
Cu silicideformation
Cu/SiO2
Cu/SAM-SH/SiO2
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 22
Darkened except for NH2
No change
No change
No change
Visual inspection upon anneal
Cu silicide formation >300oC* for SH & HNC5H4 slight inc.
No Cu silicideformation <400oC
No Cu silicideformation <400oC
but Si(OCH3)3>300oC slight inc.
No Cu silicideformation <
400oC
Sheet resistance(Ω/□)No
FailSame SiCl3 head group & chain length, n=11, but different terminal
groups, Br, CN, & CH3
Fail exceptSi(OCH3)3
Same CH3 terminal & chain length, n=17, different head group, SiCl3,
Si(OCH3)Cl2 & Si(OCH3)3
PassSame Si(OCH3)3 head group & similar chain length, n=1 or 3, but
different terminal groups, NH2, SH & HNC5H4
FailSame CH3 terminal and SiCl3 head groups but different chain lengths,
n= 7-21
Tape testSample
SAMsSAMs compared: adhesion & Cu compared: adhesion & Cu silicidesilicide formationformation
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 23
(2) (2) SAMsSAMs as Cu diffusion barrieras Cu diffusion barrier -- conclusionsconclusions
Molecules with SiCl3 head group show enhanced inhibition of silicide formation (> 400°C) - related to the relatively high thermal stability of the SAM (550-600°C) and dense SAM packing
No obvious effect of chain length n = 7-21 or terminal group CH3, Br & CN
Significant effect from head group, all molecules (including CH3 terminated) with Si(OCH3)3 head group pass tape tests - less densely packed SAMs may allow Cu penetration promoting adhesion
In general, molecules with Si(OCH3)3 head group, even with reactive terminal groups, show lower inhibition of silicide formation (250-300oC) compared with molecules with SiCl3 head group (>400oC). But adhesion on Si(OCH3)3 >> SiCl3.
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 24
OutlineOutline
ALD of WCxNy/various-SAMs
Atomic layer depositionSAM compatibility with ALDEffect of SAM termination Influence of alkyl chain length
SAMs as Cu diffusion barrier
Previous workAdhesion & Cu silicide formation
Characterization of Cu/CO2H-SAM
LEIS: SAM outer most surfaceXPS: SAM-metal bonding
Conclusions
Application of SAMs in Nanoelectronics: surface engineering
Passive
Active
Characterization
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 25
LEIS: preparation of the Au(111) substrateLEIS: preparation of the Au(111) substrate
LEIS spectra measured with 3 keV 4He+ ions from a (111)-textured Au surface as-received, following oxidation treatment with an atomic oxygen source, and after cleaning by 20Ne+
sputtering cycles and annealing to ∼500 K for 30 min.
1000 1500 2000 2500 30000
100
200
300
400
500
600
Au
O
Inte
nsity
(Cts
/nC
)
Energy (eV)
as-received oxidized
sputtered (9.4*1014 ions/cm2) annealed
M. de Ridder and H.H. Brongersma
Calipso B.V., Eindhoven, The Netherlands.
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 26
LEIS: gas phase adsorption of 3MPALEIS: gas phase adsorption of 3MPA
500 1000 1500 2000 2500 30000
20
40
60
80
O
Inte
nsity
(Cts
/nC
)
Energy (eV)
0.05*1015 ions/cm2
0.11*1015
0.16*1015
0.27*1015
800 1000 1200 140020
25
30
35
40
Inte
nsity
(Cts
/nC
)
Energy (eV)
0.05*1015 ions/cm2
0.11*1015
0.16*1015
0.27*1015
2200 2400 2600 2800 30000
20
40
60
80
Inte
nsity
(Cts
/nC
)
Energy (eV)
0.05*1015 ions/cm2
0.11*1015
0.16*1015
0.27*1015
LEIS spectra measured with 3 keV 4He+ ions showing (a) the entire spectrum, (b) the oxygen peak, and (c) the high-energy onset of the background for a 3-MPA SAM adsorbed from the gas phase on Au(111). The spectra are normalised to the maximum background intensity of the first spectrum measured.
(b)
Full spectrum
Oxygen
High energy onset
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 27
LEIS: gas LEIS: gas vs.vs. liquid phase adsorptionliquid phase adsorption
Change in the oxygen peak area with increasing ion dose for 3-MPA and 11-MUA SAMs adsorbed from the gas or liquid phase on Au(111). Measurements were done with 3 keV4He+ ions. Peak areas were determined by fitting with a Gaussian after linear background subtraction.
0.0 0.5 1.0 1.5 2.00
50
100
150
200
250
Oxy
gen
peak
are
a (a
.u.)
4He+ ion dose (*1015 ions cm-2)
Adsorption phase 3-MPA gas 3-MPA liquid 11-MUA liquid
Surface oxygen contentSurface oxygen content
LEIS spectra measured with 3 keV 4He+ ions showing the high-energy onset of the background for 3-MPA and 11-MUA SAMs adsorbed from the gas or liquid phase on Au(111). A spectrum from clean Au(111) is shown for comparison with the Au peak normalised to the same height as the SAM/Au spectra at 2200 eV.
2200 2400 2600 2800 30000
20
40
60
80
Nor
mal
ised
inte
nsity
(Cts
/nC
)
Energy (eV)
Adsorption phase 3-MPA gas 3-MPA liquid 11-MUA Liquid Au
Film thicknessFilm thickness
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 28
LEIS: gas LEIS: gas vs.vs. liquid phase adsorptionliquid phase adsorption
Change in the oxygen peak area with increasing ion dose for 3-MPA and 11-MUA SAMs adsorbed from the gas or liquid phase on Au(111). Measurements were done with 3 keV4He+ ions. Peak areas were determined by fitting with a Gaussian after linear background subtraction.
0.0 0.5 1.0 1.5 2.00
50
100
150
200
250
Oxy
gen
peak
are
a (a
.u.)
4He+ ion dose (*1015 ions cm-2)
Adsorption phase 3-MPA gas 3-MPA liquid 11-MUA liquid
Surface oxygen contentSurface oxygen content
Sample Thickness (Å) Theoretical thickness (Å)
3-MPA(g) 4 ± 1 4.5
3-MPA(l) 6.5 ± 2 4.5
11-MUA(l) 11 ± 2 13.9
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 29
XPS: gas phase adsorption of 3MPAXPS: gas phase adsorption of 3MPA
160 162 164 166 528 530 532 534 536 538
533.3532.0
163.7
162.5O 1sS 2p
Inte
nsity
[Arb
. Uni
ts]
Binding Energy [eV]
292 290 288 286 284 282 280
C 1s
284.6285.2
289.1
Inte
nsity
[Arb
. Uni
ts]
Binding Energy [eV]
CO2H
CO2H-CH2CH2SH
thiolate C=Ocarbonyl
C-OHhydroxyl
2 types of oxygen
3 types of carbon
1 type of sulphurJ. Ghijsen and J.-J. PireauxLISE, FUNDP, Namur, Belgium.
C.M. Whelan et al., Thin Solid Films (2005) HOCS
Au(111)
mercaptopropionic acid CO2H-(CH2)2-SH
12
3
12
1
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 30
HO
CS
Au
Cu
O-Cu-O bidentate
Cu-OhydroxylCu-Ocarbonylunidentate
Cu/COCu/CO22HH--SAMs: possible bonding interactionsSAMs: possible bonding interactions
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 31
XPS: evaporation of Cu on 3MPAXPS: evaporation of Cu on 3MPA
292 290 288 286 284 282 280
C1s
0
0.35
0.72
1.4
2.2
3.6
5.0
Cu [ML]
Inte
nsity
[Arb
.Uni
ts]
Binding Energy [eV]
CO2H-Cu bonding
538 536 534 532 530 528
Cu [ML]
5.0
3.6
2.2
1.4
0.72
O1s
0.35
0In
tens
ity [A
rb. U
nits
]
Binding Energy [eV]
Cu-O bonding
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 32
XPS: evaporation of Cu on 3MPAXPS: evaporation of Cu on 3MPA
538 536 534 532 530 528
Cu [ML]
5.0
3.6
2.2
1.4
0.72
O1s
0.35
0In
tens
ity [A
rb. U
nits
]
Binding Energy [eV]
Cu-O bonding
538 536 534 532 530 528
Cu [ML] 0 0.35 0.72 1.4 2.2 3.6 5
Binding Energy [eV]
Cu interacts with CO2H group
Selective deposition at OH site
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 33
XPS: evaporation of Cu on 3MPAXPS: evaporation of Cu on 3MPA
940 936 932 928 572 568 564
1.0
0.350.721.42.2
3.65.0
Cu [ML]
Cu 2p3/2Cu LMM
Inte
nsity
[Arb
. Uni
ts]
Binding Energy [eV]
960 955 950 945 940 935
Cu2O/CuO
Cu0/Cu2O
Binding Energy [ev]
Cu(II) shake-up
932.5 eV
Cu-O interaction weak and/or Cu clustersCu oxidation state Cu(0)-Cu(I)no Cu penetration to Au surface
568.5 eV(918.1 eV)
568.8 eV (917.8 eV)
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 34
LEISDifferent CO2H-SAMs for gas vs. liquid phase formation :
Thickness 4 vs. 6.5 ÅSurface oxygen content x 5 difference
XPSThiolate surface intermediate with an intact carboxylic acid function
Cu adsorption : induces changes in carboxylic acid C 1s preferential modification of the hydroxyl group indicating unidentate complexationCu 2p comparable with bulk suggests cluster growth and weak Cu-CO2H-SAM interactionsNo penetration to the Au surface
(3) Cu/CO(3) Cu/CO22HH--SAM characterization SAM characterization -- conclusionsconclusions
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 35
Final remarksFinal remarks
ALD of WCxNy/various-SAMsTerminal group and alkyl chain length determine growth behavior
Vary substrate structure & chemistry to selectively control growth
SAMs as Cu diffusion barrierCu silicide formation: SAM-SiCl3 show enhanced inhibition attributed to high thermal stability and dense packing of SAM but no no obvious effect of chain length or terminal groupAdhesion: significant effect from head group, SAM-Si(OCH3)3 less densely packed may allow Cu penetration, XPS fracture analysis shows failure at SAM/SiO2 interface (vs. Cu/SAM for SiCl3)
SAM composition impacts adhesion & barrier properties
Characterization of Cu/CO2H-SAMLEIS reveals SAM outer most surfaceXPS identifies exact SAM-metal bonding
Frontiers of Characterization and Metrologyfor Nanoelectronics 2007 36
AcknowledgementsAcknowledgements
F. Clemente, A.-C. Demas$, A. Martin Hoyas, J. Schuhmacher,
L. Carbonell, T. Conard, B. Eyckens, O. Richard, Y. Travaly, D. Vanhaeren,
Rudy Caluwaerts, Caroline de Meurisse, and IMEC P-line.
This work has been carried out within IMEC’s Advanced Interconnect Industrial Affiliation Program.
$CEA/DRT/LETI/DPTS/SCPIO/LCPO, Grenoble, France.
THANK YOU !
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