Transcript High resolution morphological and mechanical

High resolution morphological
and mechanical characterization
of Niobium films obtained by MS
and Biased MS PVD
E. Bemporad, M. Sebastiani, F. Carassiti
University "Roma Tre", Dep't of Mechanical and Industrial Engineering
Via Vasca Navale 79 - 00146 Rome Italy
[email protected]
The International Workshop on:
Thin Films and new ideas for
pushing the limits of RF superconductivity
October 9-12, 2006
Where is the University “Roma Tre”?
Rome
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Roma Tre, some numbers…
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www.uniroma3.it
INFN Workshop, 10-2006
Born in 1992.
One of the 4 State University in
Rome (9 in total).
125.000 m2.
More than 40.000 students
(3.900 enrolled in Engineering)
More than 700 Researchers
and Professors.
Faculty of Engineering:
 Civil
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 Materials Science and
Technology research
group
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
3
Main objectives of presented work
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To measure basic surface mechanical
properties of Nb films, such as
hardness, Elastic modulus and work
hardening behaviour;
To correlate this data with
microstructure and surface roughness,
which greatly affect the transition
temperature (Tc) and the Residual
Resistivity Ratio (RRR) of Nb films.
To compare results obtained from
biased MS and non biased MS films
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Outline
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Introduction
Materials and methods
 Modelling of basic surface mechanical
properties overview
Results
 Mechanical properties
 Microstructure and morphology
Discussion and conclusions
Further developments
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Introduction
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Both structure and properties of films
depend on deposition conditions used
Increasing bias voltage increases the
energy of bombardment ions, resulting
in:
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
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Densification of the film
Increasing inherent compressive stress due
to Ar incorporation
Additional defects in coatings structure
Changing in texture
Preferential grow direction
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Introduction
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Microstructural changes reflect also in
mechanical properties changes
By the measure of mechanical properties
the effect of deposition condition on
microstructure can be verified
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Materials and Methods
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
8
Materials
INFN Workshop, 10-2006
9
765
CERN type sputtering
12
766
CERN type sputtering
YY
767
bias type sputtering (100V)
R
768
bias type sputtering (100V)
4
769
CERN type sputtering
2
770
CERN type sputtering
Q
771
bias type sputtering (100V)
LL
772
bias type sputtering (100V)
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
9
Materials
INFN Workshop, 10-2006
9
765
CERN type sputtering
12
766
CERN type sputtering
YY
767
bias type sputtering (100V)
R
768
bias type sputtering (100V)
4
769
CERN type sputtering
2
770
CERN type sputtering
Q
771
bias type sputtering (100V)
LL
772
bias type sputtering (100V)
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Methods
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OM and SEM observation, plan view
and LN2 cross-section
Micro Hardness measurements, both
Vickers and Knoop indenters, with
loads ranging from 1N down to
0,005N
AFM in contact mode on the surface
and inside indentation marks
FIB-CrossBeam cross-section on the
surface and inside indentation marks
(still ongoing)
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Methods
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Elastic modulus obtained by 3D
reconstruction of residual indent volume
and applying Lesage (on Vickers indent)
and Marshall (on Knoop indents)
models.
Work hardening behavior evaluated by
the Indentation Size Effect (Meyer
model);
Intrinsic hardness obtained applying
Jonsson-Hogmark and Chicot-Lesage
hardness models;
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Modeling of basic surface
mechanical properties
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Vickers indenter
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Knoop indenter
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Vickers indentation at different loads
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Elastic modulus, Lesage model
Model based on residual
indent volume (VRe)
measurement, and
comparison with the
theoretical one.
Indentation performed at low load (0,005N), so to have z < film thickness/10
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Elastic modulus, Lesage model
dP
dh

h  hmax
Pmax
2
2

 Er  AC 
 Er  d
h'


h'  hth  heq
Er 
1 2
VRe  d heq
6

Pmax
6 VRe 
2 
d   zth  2 
d 


 
1  i
1
1  2


Er
E
Ei
2

J.Lesage et al., Surface and Coating
Technology 81 (1996) 269-274
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Elastic modulus, Marshall model
HK
W ' 
W 
 
 0,45
 
E
 L  misurato  L  teorico
D.B.Marshall, comunication of the
American Ceramic Society, C-175 (1982)
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Vickers hardness
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Knoop hardness
φ
L = 7,114w
θ
P
P
HK 
 2
APAC L  tg   2  tg  
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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ISE – Meyer, elasto-plastic behaviour
σ
σ
σS
σS
ε
High load, macro hardness
INFN Workshop, 10-2006
n
ε
Low or very low load,
micro/nano hardness
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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ISE – Meyer, elasto-plastic behaviour
Lower loads
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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ISE – Meyer, elasto-plastic behaviour
Lower loads
 y   y0  
m
m  n2
Work hardening effect
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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ISE – Meyer, elasto-plastic behaviour
Example: Ti6Al4V alloy
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H  H0  d
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
n 2
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Hardness of coated systems
HV
Hardness of the film
Plastic
zone
Film
Substrate
Low Load
Models
H d   H 0 
k
d
Film
Hardness of the substrate
1/d
INFN Workshop, 10-2006
Substrate
Plastic zone
High Load
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
26
Hardness of coated systems
HC  aHF  bHS
HC  H S  H (e, d , E)  (H F  H S )
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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JÖNSSON & HOGMARK (1984)
Geometrical representation
AF
x
x
B’
B
AS
C
HF
t
22°
A
A  A S  AF
 AF
HC  
 A
INFN Workshop, 10-2006
t
t
11°
A’
t
HS
HS
Total area :
HF
C’
Ductile material
C=1
 AS 

H F   H S

 A
Brittle material
C=0.5
AF
t
2 t 
 2C  C  
A
d
d 
AS
AF
 1
A
A
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
2
28
Chicot & Lesage
(1995)
bS
bF
Film
Substrate
+
Substrate
VSS
Film
VFS
VSF
VS VSF VSS
 VFF VSF
H C 1
 V V
S
 F
1 
t

1/ 3
H C H S   3  tg  
2 
d

INFN Workshop, 10-2006
VFF
VF VFF VFS

 VFS VSS

H F  2 
 V V
S

 F
 H
  F
 EF
1/ 2



 HS
 
 ES
1/ 2





H S



   H F H S 
 

Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Static and dynamic indentation
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All model presented are based on
measurements performed on the residual
indent.
Some equipments, called depth sensing
indenter, let to measure the load
displacement curve during the indentation
test
In this case the Oliver and Pharr method
gives a way to evaluate hardness and Elastic
modulus simultaneously, for a given
maximum load
No data on depth sensing indentation will be
reported in this work
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Results
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
31
MHV at 0,5 g load
Biased vs. not biased MHV results
0,4
0,35
0,3
V (um3)
0,25
0,2
0,15
0,1
Biased V_(A)
Biased V_(A+B+C)
Not biased V_(A)
Not biased V_(A+B+C)
0,05
0
0,1
0,15
0,2
0,25
0,3
0,35
z (um)
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
32
Elastic modulus and ISE
Biased MS E = 88,95 GPa
INFN Workshop, 10-2006
unbiased MS E = 54,33 GPa
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
33
Hardness comparison
biased MS (#YY-767)
INFN Workshop, 10-2006
unbiased MS (#12-766)
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
34
Hardness comparison
700
HV film hardness mean value J-H model
600
500
400
300
200
100
0
LL-772
Q-771
R-768
biased MS
INFN Workshop, 10-2006
YY-767
12-766
2-770
4-769
9-765
Not biased MS
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
35
Results
deposition
mode
unbiased
MS
biased MS
INFN Workshop, 10-2006
ID
Elastic modulus
[GPa]
HARDNESS
MHV, [Kg/mm2]
#
Lesage
(ref.)
JonssonHogmark
ChicotLesage
4-769
(103)
468,3
(671,9)
2-770
(103)
508,8
(685,5)
9-765
(103)
329,3
(561,5)
12-766
54,33
255,3
337,6
Q-771
(103)
547,8
(617,6)
LL-772
(103)
542,5
(716)
YY-767
88,95
478,7
589,1
R-768
(103)
663,7
(794,7)
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
36
Results
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Biased MS films show more than 50% higher
MHV hardness then unbiased MS films
Biased films are more prone to be work
hardened with respect to unbiased films
Elastic modulus of biased MS films resulted to
be more than 60% higher than unbiased MS
films
Such differences in Elastic Modulus are
obviously not due to changes in the Nb Elastic
properties, but due to a variation of coating
microstructure (density, homogeneity, grain
growth direction,…).
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Micro morphology
Cu substrate
unbiased MS
INFN Workshop, 10-2006
biased MS
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
38
Microstructure and morphology
Ln2 cross section, biased MS, #R-768
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Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Microstructure and morphology
FIB cross section, unbiased MS, #2-770
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
40
Microstructure and morphology
FIB cross section, unbiased MS, #2-770
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Results
Halbritter, Journal Of
Applied Physics 97,
083904 (April, 2005)
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Sub-micro morphology
unbiased MS (#12-766); grain size ≈ 300nm
biased MS (#R-768); grain size < 100nm
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
43
Sub-micro morphology
unbiased MS (#12-766); grain size ≈ 300nm
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Surface defects: FIB
(25 kV, 8.000 x, SEM
SE detector)
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Microdroplets
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Sub-micro morphology
biased MS (#R-768); grain size < 100nm
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Sub-micro morphology
G. Wu et al. / Thin Solid Films 489 (2005) 56– 62
51V bias
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Ion beam sputtering on deposited film
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J. Appl. Phys., Vol. 81, No. 10,
Grain type A:
15 May 1997
channeling direction
aligned with ion beam
promote growing
Grain type B:
shadowed by type A
grain growing,
demote growing
Grain type C:
high ion sputter rate
Roughness is proportional to
highly demote
normalized energy and film
growing
thickness
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
49
Ion beam sputtering on deposited film
biased MS (#Q-771)
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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71
14
80
12
70
60
Ra and RMS
10
50
8
40
6
30
4
2
20
R-768
0 MS
biased
LL-772
YY-767
Q-771
R-768 YY-767 12-766
biased MS
Peak to Peak value
Peak to Peak value
INFN Workshop, 10-2006
12-766
2-770
2-770
4-769
10
Peak to Peak (nm)
Roughness
4-7
0 MS
Not biased
9-765
Not biased MS
RMS value
RMS value
Ra value
Ra value
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
51
Results
THICKNESS
#
[µm]
RMS
Ra
peak- to peak
[nm]
4-769
0,73
8,2
6,5
55,7
2-770
0,61
7,1
5,7
43
9-765
1 (±0,1)
7,6
6,1
46
12-766
1,9 (±0,2)
8,2
6,6
43,5
Q-771
1
12,4
10
68
LL-772
0,98
9,4
7,4
59,3
YY-767
1,3
11,8
9,7
62
R-768
0,9 (±0,1)
12,5
10,2
68
deposition
mode
unbiased
MS
biased MS
ROUGHNESS
(7,5 µm2 investigated)
ID
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
52
Results
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At a macroscopic scale, biased films
seem to replicate substrate
morphology, whilst unbiased films
seem to flatten substrate surface
At sub-micrometric scale, biased films
showed an higher roughness that the
unbiased films
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
53
Results
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Unbiased MS films show a first growing
thickness of about 200nm with a
polycrystalline shape, afterward grains
are all columnar
Columnar grains bend without apparent
cracks, so showing a low value of
residual stress compared to Nb
strength
Grains dimension is lower for biased
films, with an apparent influence on
grain growth direction
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
54
Conclusions
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
55
Conclusion
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Surface mechanical properties obtained form
Vickers indentation of biased and unbiased
MS Nb films has been correlated with microstructural and morphological properties
Results confirmed that biased MS films shows
higher hardness, higher Elastic modulus,
higher work hardening behavior, coupled with
higher roughness compared with unbiased
films
Preferential sputtering of biased MS films
based on crystallographic orientation are also
observed, driving to the growth of elongated
grains
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
56
Conclusion
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After hardness measurement and the use
of models to extrapolate true film
hardness, some useful information on
density and residual stress can be
estimated by the evaluation of the work
hardening attitude and the elastic
modulus calculation.
The combined use of FIB and AFM
techniques confirmed to be the best
choice for the evaluation of
microstructural and morphological
parameters
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
57
Further developments
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More statistics
Applying Marshall model to evaluate
Elastic modulus via in-plane recovery of
Knoop indent
Complete FIB characterization of oxide
layer thickness, grain size and growth
defects for both type of films
Use of Finite Element Modeling to
foresee behavior of multilayer “soft on
soft” films
INFN Workshop, 10-2006
Bemporad et al.: High resolution morphological and mechanical characterization
of niobium films obtained by MS and Bias-MS PVD
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Thank you for your attention
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[email protected]
www.stm.uniroma3.it
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of niobium films obtained by MS and Bias-MS PVD
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DIMI - STM
Material Science and Technology Research Group
Structural and thermo-mechanical applications
Università di Roma - Roma TRE
Via Vasca Navale, 79 00146 – Roma
WEB SITE:
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