UNIVERSITÀ DEGLI STUDI DI PADOVASCIENCE FACULTY
MATERIAL SCIENCE DEGREE
INFN – LABORATORI NAZIONALI DI LEGNARO
MORPHOLOGY OF NIOBIUM FILMS SPUTTERED AT MORPHOLOGY OF NIOBIUM FILMS SPUTTERED AT DIFFERENT TARGET DIFFERENT TARGET –– SUBSTRATE ANGLESUBSTRATE ANGLE
DIEGO TONINI
�� WhatWhat isis the the effecteffect of target of target –– substrate substrate angle on the film properties?angle on the film properties?
�� HowHow the film the film morphologymorphology variesvaries changingchangingtarget target –– substrate angle? substrate angle?
2 QUESTIONS…
DEPOSITIONS MADE AT DIFFERENT TARGET –SUBSTRATE ANGLE
CRYSTAL STRUCTURE
SUPERCONDUCTINGPROPERTIES
TC MEASURE
RRR
MAGNETO-OPTICAL
ELECTROCHEMICALIMPEDANCE
SPECTROSCOPY
AFM IMAGING
THICKNESS
TEXTURE ANALYSIS
X-RAYDIFFRACTION
FILM MORPHOLOGY
• 7 substrates coated in the same run
• Almost identical processconditions for each sample
MULTI-ANGLE SAMPLE HOLDER
PULSED MAGNETRON SPUTTERING
• BETTER PROPERTIES FOR PULSED CURRENT DEPOSITION
• THERE IS STILL THE SAME ANGLE DEPENDENCE OF TCAND RRR
DC MAGNETRON SPUTTERING WITH SUBSTRATE HEATING
Substrate temperature kept at 600°C duringprocess
1. Better properties
2. Less angle sensitivity
0 15 30 45 60 75 900
5
10
15
20
25
RR
R
deposition angle (degrees)
0 15 30 45 60 75 908.2
8.4
8.6
8.8
9.0
9.2
9.4
9.6
TC (K
)
deposition angle (degrees)
20 40 60 80 100 120 1400
20
40
60
80
100
321222310220
211200
110
75 degrees
60 degrees
45 degrees
30 degrees
15 degrees
Rel
ativ
e In
tens
ity
2 Theta (degrees)
XRD SPECTRA OF FILM DEPOSITED AT DIFFERENT TARGET – SUBSTRATE ANGLE
ESTIMATED GRAIN DIMENSION
)2()cos(9.0
θθλ∆⋅
=D
15 30 45 60 75
60
80
100
120
140
crys
talli
te d
imen
sion
(Ang
stro
m)
deposition angle (degrees)
d110 OF CRYSTAL PLANES
λθ nd hkl =sin2 )(
15 30 45 60 75
1,0
1,2
1,4
1,6
1,8
2,0
2,2
2,4
2,6
2,8
3,0
d 110 (
Ang
stro
m)
deposition angle (degrees)
TEXTURE ANALYSISDC VS PULSED MAGNETRON SPUTTERING
0 15 30 45 60 75 90
0
10
20
30
40
50Φ
max
cou
nts
(deg
rees
)
deposition angle (degrees)
DC PULSED
0 15 30 45 60 75 900
2
4
6
8
10
12
14
16
18
20
roug
hnes
s (n
m)
deposition angle (degrees)
ATOMIC FORCE MICROSCOPY DC MAGNETRON SPUTTERING
0 15 30 45 60 75 900
2
4
6
8
10
12
14
16
18
20
roug
hnes
s (n
m)
deposition angle (degrees)
Variable thickness Uniform thickness
I campioni depositati in corrente pulsata sono sistematicamente più rugosi
ATOMIC FORCE MICROSCOPY PULSED MAGNETRON SPUTTERING
ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY
)cos()( 0 tVtV ω=
)cos()( 0 ϕω −= tItI
)cos()cos(
)()(
0 ϕωω−
==t
tZ
tItV
Z
ϕjeZZ 0=
ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY NYQUIST PLOT
0 2 4 60
2
4
6porous electrodeideally flat electrode
Im(Z
) /a
rbitr
ary
units
Re(Z) / arbitrary units
FLAT ELECTRODE:
Real part of impedance representsRs at any frequency
Immaginary part does not vary withfrequency
NYQUIST PLOT IS A VERTICAL LINE
POROUS/ROUGH ELETRODE:
The apparent capacity Cdl dependson frequency because the penetration length of electric fieldinside the pores raises whendecreasing frequency.
NYQUIST PLOT IS A 45°INCLINED LINE
ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY DC MAGNETRON SPUTTERING
VARIABLE FILM THICKNESS
Up to 45°there is porouselectrode behaviour
Film deposited at higher angles are less thick so resistence is greaer
COMPARISON BETWEEN FILM WITH DIFFERENT THICKNESS AND FILM WITH CONSTANT THICKNESS
Films with the same thickness havethe same resistance
There is a maximum in capacity at 60°target – substrate angle
ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY DC MAGNETRON SPUTTERING
Films with the same thickness –measures in passivaton condition
Imposed potential to create a passivation layer on the film
Oxide tichkness depends onlyon applied potential
Oxide growth follows niobiumfilm morphology
Capacity shows the sameangle dependence of non oxidized films
ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY DC MAGNETRON SPUTTERING
100×−=∆ pulsedac
pulsedac
contac
CCC
R
ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY PULSED MAGNETRON SPUTTERING
MAGNETO-OPTICAL ANALYSIS
OFHC copper substrate (not electropolished)
Target – substrate angle: 0°
Good connectivity respect tovortex penetration
Target – substrate angle: 45°
Vortex penetrate along substratediscontinuity
CONCLUSIONS s.c. and transport properties
0 15 30 45 60 75 90
7.8
8.0
8.2
8.4
8.6
8.8
9.0
9.2
9.4
9.6
TC (K
)
deposition angle (degrees)
DC PULSED HEATED
0 15 30 45 60 75 900
5
10
15
20
25
RR
R
deposition angle (degrees)
DC PULSED HEATED
Properties depend on target – substrate angle
Pulsed magnetron sputtering and heating of the substratereduce the angle dependence
CONCLUSIONS Crystal structure
FilmsFilms depositeddeposited at at higherhigher anglesangles tendtend towardstowardsamorphizationamorphization
Lattice Lattice parameterparameter hashas a a maximummaximum at 60at 60°°target target ––subtrate anglesubtrate angle
(110) crystal (110) crystal planesplanes of the of the growinggrowing film film orientorientalongalong niobiumniobium atomsatoms arrivalarrival directiondirection
ThisThis effecteffect isis reducedreduced usingusing pulsedpulsed magnetron magnetron depositiondeposition
CONCLUSIONSmorphology
0 15 30 45 60 75 90
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
norm
aliz
ed in
tens
ity
deposition angle
Impedance spectroscopy AFM simulated
There is a maxmum in roughness between 60°and 75°target – substrate angle
This is not a thickness effect but is due to deposition dynamics