Correlation between chemical structure and functional properties of organosilicon plasma polymers and Si02-like films
Lenka Zajíčková1, Vilma Buršíková1, David Trunec1, Václav Pekař1, Vratislav Peřina2, Romana Mikšová2, Daniel Franta1
1 Department of Physical Electronics Masaryk University, Brno, Czech Republic
2 Institute of Physics, AS CR, Praha, Czech Republic lenkaz@physics.muni.cz
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Motivation Experimental Variety of materials Temperature Induced Changes Conclusion
• Motivation
• Experimental
• Variety of materials
• Temperature Induced Changes
• Conclusion
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Hexamethyldisiloxane (HMDSO)
- versatile starting material for PECVD:
HMDSO
o
o
source of Si-O-Si bonds (especially for HMDSO/O2)
PECVD in low pressure rf capacitively coupled discharges (CCP) - variety of different materials can be prepared when using the mixture of HMDSO/O2 in varying deposition conditions:
► percentage of HMDSO in HMDSO/O2 pressure p rf power P
*■ dc self-bias Ub (in relation with P and p)
source of Si-C bonds
© /      \ ©
How these materials react to annealing?
PECVD using HMDSO at atmospheric pressure: competition with low pressure process in achievement of silica-hard coatings
Will help an increased deposition temperature?
Motivation Experimental Variety of materials
PECVD in low pressure rf CCP from HMDSO/02
Experimental
etwee
Variety of materials
Temperature Induced Chai
variation of HMDSO % in the mixture •
variation of QQ2 at the fixed Qhmdso = 4 seem
decrease of HMDSO % (expecially for 5-8 %) => decrease of ion energy flux
350 300 250 200 150 100 50
increase of pressure
>
5     10    15   20   25 30
pressure [Pa]
■   10 Pa (100%)	
2 0 Pa (44%)	
4 4 Pa (17%)	
•   26.6 Pa (8%)	
100   200   300   400 500 P(W)
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Zajíčková etai. Plasma Sources Sei. Technol. 16 (2007) S123
Zajíčková etal. Surf. Coat. Technol. 142-144 (2001) 449, Zajíčková etat. Plasma Sources Sei. Technol. 16 (2007) S123
Variety of materials Temperature Induced Changes
5% HMDSO, effect of pressure
P Qhmdso     Q02 P Uh Si(%) Q(%) C(%) H(%)
(Pa) (seem) (seem) (W) (V)               25 43 10 22
40         4           80 100 -20               23 56 1 20
2.5        0.7 14 100 -120
1000   1500   2000   2500 3000
wavenumber (cm1)
nduce
Annealing induced changes in Si02-like films deposited in low pressure (2.5 Pa) CCP from 5% HMDSO/02
Improvement of mechanical properties of SiC>2-like films deposited in atmospheric pressure dielectric barrier discharge (DBD) by slight increase of deposition temperature
Improvement of mechanical properties of SiOxCyHz film deposited in CCP from 8% HMDSO/02 at 450 W by annealing
Annealing experiments for the films deposited in CCP from HMDSO-rich mixtures (17, 44 and 100% of HMDSO)
Temperature Induced Changes
5 % HMDSO, 2.5 Pa / Si02-like film in CCP
q_
(3
12
10
140
•ro 120
cl
CD
X 100 Hi
80
5% HMDSO/02 P = 100W, U :
2.5Pa, -120V
■ as depos —'-500°C
0.2   0.4   0.6   0.8   1.0   1.2 1.4 indentation depth (|jm)
CL
C3
T3
10
-d— = 800nm-
indentation induced delamination
0.0 0.2 0.4 0.6 0.8  1.0  1.2 1.4
relative indentation depth
Originally:
compressively stressed film with good fracture toughness
Annealing:
slight stress relaxation due to annealing
decrease of hardness induced by stress relaxation compensated by creation of new Si-O-Si bonds instead of Si-OH
■0 0.0
Motivation Experimental Variety of materials Temperature Induced Changes
5 % HMDSO, 2.5 Pa / Si02-like film in CCP
Townsend-like (homogeneous) discharge at 6 kHz
max. power 10W/cm3
discharge gap of 0.5 mm
upper electrode covered by Simax (1.5 mm thick)
bottom covered by glass substrate or glass plate (1mm thick) with Si substrate
substrate temperature 23-150 °C
HMDSO / synthetic air / nitrogen
6 seem of N2
6slm of synthetic air
6 or 16sccm of air through liquid HMDSO
6seem => 70ppm of HMDSO, 200 ppm of 02 in N2
16seem =^ 173 ppm of HMDSO, 532ppm of 02 in N2
Variety of materials
q_
o
cd
c
T3
glass 6/6/
25   50    75   100 125 150
temperature (°C)
ron Si subs.
	60	6sccm of air	Si	-'1
cd O)	50		-------0	
ra			• c	
"c	40		--------h	
cd				
O	30			
cd				
Q.	20			
o				
E	10	......		
o	n			
25   50   75   100 125 150
temperature (°C)
o
a
	2.0
	1.8
o	
-S	1.6
	
>.	1.4
"tri	
c	1.2
CD	
"O	1.0
	0.8
Temperature Induced Changes
density molar density
on Si subs.
- IL
25 50 75 100 125 150
temperature (°C)
0.20	
	E
	ü
0.15	ö
	E,
0.10	>.
	m
	c
	cd
0.05	X3
	ns
0.00	mol
1500 2000 2500 3000 3500 wavenumber (cm" )
Trunec etal. J. Phys. D 43 (2010) 225403
4 □ ►  4 3 ► 4
Motivation Experimental Variety of materials
CCP 450 W, 8 and 17% HMDSO
Temperature Induced Chai
8% HMDSO: p = 26.5Pa, Ub 17% HMDSO: p = 4.5Pa, Ut
12 :
Critical depth for indentation induced crack initiation in /^m: -100V -250V
co q_
q_
CD
6 - 1-
8% HMDSO -17% HMDSO
80 70 60
50-
100
200 300 T(°C)
400 500
%/ T(°C)	-	300	350	400	500
8 17	0.34 > 1	0.42 > 1	0.44 > 1	0.45 > 1	> 1 0.46
q.
C3
0.2 0.4 0.6 indentation depth (|jm)
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Motivation Experimental Variety of materials
CCP 450 W, 8 and 17% HMDSO
as deposited:
Temperature Induced Chai
%	8%	17%
Si	22	20
o	47	37
c	5	11
H	25	32
-8%,  5.5 GPa 17%, 9.0 GPa
as deposited
0.2 0.1
0.0
2200 2400 2600 2800 3000 3200 4
500 1000 1500
wavenumber (cm"1)
% HMDSO	T(°C)	O/Si	H/Si	C/Si
8	-	2.12	1.12	0.24
8	300	1.94	0.81	0.29
8	500	1.93	0.55	0.21
17	-	1.85	1.60	0.56
17	300	1.79	1.37	0.57
17	500	1.99	1.01	0.57
O 0.12 "%0.10
P(g/cm )
0       300 500       0       300 500
temperature (°C)
	0.2
	0.1
E	0.0
	
O	4
	3
a	2 •1
	1 0
2300   2800 3000 3200 3400 3600
	1.2
	1.0
	0.8
E	
o	0.6
o	0.4
s	0.2
	0.0
500 1000 1500
wavenumber (cm"1)
8%, 450W
1620-1610 1710cm"1
2260cm"1
1650        2500   3000 3500
wavenumber [cm"1]
■0 0.0
Motivation Experimental Variety of materials Temperature Induced Changes
CCP 450 W, 44 and 100% HMDSO
»   8% HMDSO	44% HMDSO	Chmdso (%)	8	17	44	100
-■-17% HMDSO	100% HMDSO	p(Pa)	26.5	4.5	2	1
16,-		Uh (V)	-100	-250	-300	-335
q_
O
TO CL
CD
6-140 :
120
100
LU 80
60-
0    100   200   300   400 500 T(°C)
10
q_
c
"O
100% HMDSO, 1Pa 450W, -335V ^
2
0.0
- as deposited 350°C 400°C 500°C
0.1 0.2 0.3
relative indentation depth
100 and 44% films are compressively stressed but the hardness does not decreases with annealing temperature
fracture toughness is not as good as for 8 and 17% films and does not improve with annealing
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Motivation Experimental Variety of materials Temperature Induced Changes
CCP 450 W, 44 and 100% HMDSO
^hmdso	T(°C)	Si (%)	O (%)	C (%)	H (%)	O/Si	C/Si	H/Si
44%	-	15	18	28	39	1.2	1.9	2.6
44%	500	14	20	31	35	1.4	2.2	2.5
100%	-	17	9	32	42	0.5	1.9	2.5
100%	500	20	7	39	34	0.4	2.0	1.7
1.5 1.0 0.5 E 0.0
-44%, 10.8 GPa 100 %, 12.5 GPa
o    2000    2500     3000     3500 4000
as deposited
500 1000 1500
wavenumber (cm" )
1.5 1.0 0.5
2130cm 2235cm"1
-44%, 14.3 GPa 100%, 14.2 GPa
o    2000    2500     3000     3500 4000
500 1000 1500
wavenumber (cm" )
Qimdso	T{°C)	q (g/cm3)	qm (mol/cm3)
44%	-	1.8	0.17
44%	500	1.8	0.16
100%	-	1.8	0.17
100%	500	1.8	0.15
Motivation Experimental
CCP100 and 300 W,
44% HMDSO: 100% HMDSO:
100W 100W
Variety of materials
300W 300W
co q_ C3
10r
8 6 4
2
80
ro 60 ■ q_
e>
40-
LU~
20-0-
0    100   200   300   400 500 T(°C)
Films deposited at 300 W were not stable => peeled off when not annealed
Temperature Induced Chai
Self-bias Ub for 44 and 100% HMDSO/02 (2 and 1 Pa) at different rf powers:
P (W) / chmdao (%)	44	100
100	-120	-145
300	-230	-270
450	-300	-335
100% HMDSO film is soft polymeric material which hardness can be slightly increased by annealing and significantly improved by increased rf power.
100 W, -145 V 200 W, -215 V 450 W, -335 V
1000 2000 3000 4000 wavenumber [cm"1]
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Motivation Experimental Variety of materials Temperature Induced Changes
CCP 100W, 44 and 100% HMDSO
^hmdso	T(°C)	Si (%)	O (%)	C (%)	H (%)	O/Si	C/Si	H/Si
44%	-	15	20	17	48	1.3	1.1	3.2
44%	500	15	25	20	40	1.7	1.3	2.7
100%	-	12	18	21	49	1.5	1.8	4.1
100%	500	12	19	22	47	1.6	1.8	3.9
1.5-1.0-0.5-
0.0^ 2000
-44%, 3.5 GPa -100%, 1.8 GPa
A
2500     3000     3500 4000
as deposited
500 1000 1500
wavenumber (cm1)
2176cm |2232cm-1
1.5 1.0 0.5 0.0
2000    2500     3000     3500 4000
44%, 4.5 GPa 100%, 3.3 GPa
500 1000 1500
wavenumber (cm"1)
Qimdso	T{°C)	Q (g/cm3)	giA (mol/cm3)
44%	-	1.4	0.14
44%	500	1.4	0.12
100%	-	1.2	0.13
100%	500	1.3	0.14
Variety of materials
Temperature Induced Changes
Understanding of the changes in film mechanical properties (because of different deposition parameters or annealing) requires complete study of the film composition, chemical bonds and film density. Thermal desorption spectroscopy is advantageous.
Molar density increased with increased deposition temperature of APTD films and decreased with annealing temperature of CCP films.
Significant hydrocarbon desorption observed only for increased deposition temperature of APTD-SiOxCyHz films.
For CCP films, carbon desorption detected only for annealing of SiCVIike film (5% HMDSO, 2.5 Pa) - rather decrease of C02 than CHX. Desorption of -OH and -H more important.
Annealing of compressively stressed CCP films led to their stabilization due to stress relaxation.
Annealing of hard compressively stressed films (either SiOx:H or SiOxCyHz) did not decrease but increase the hardness - stress relaxation is compensated by cross-linking of material, i.e. replacing the end-groups (Si-OH, Si-H, C=0) by new strong bonds.
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