jong-hyeon lee and duk-young jung* department of chemistry, sungkyunkwan university south korea...
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Jong-Hyeon Lee and Duk-Young Jung*
Department of Chemistry ,
SungKyunKwan University
South Korea
Etching of Organo-Siloxane Thin Layer by Thermal and Chemic
al Methods
Etching of Organo-Siloxane Thin Layer by Thermal and Chemic
al Methods
Inorganic Chemistry, SungKyunKwan Univ.
Introduction
Self-Assembled Monolayers (SAMs) have begun to explore applications in microfabrication, including microcontact- printing. For selective deposition, earlier reports show that patterned SAMs of OTS can be utilized as a molecular resist or templates in directing the thin-film. However, in many occasions, the OTS SAMs are found to still remain on the surface.
We observed substrate-effects and stability in microcontact-printed OTS SAMs on oxidized silicon and slide glass by thermal, hydrothermal and photochemical treatments.
SAMs(Self-Assembled Monolayers)
SAMs form spontaneously by chemisorption and self-organization of functionalized, long-chain organic molecules onto the surfaces of appropriate substrates.
Functional group
Alkyl chain
Reaction group
substrate
Inorganic Chemistry, SungKyunKwan Univ.
O
Si
O
Si O
O
Si
O
O
oxide layer
hydrophobic functional groups
tilted angle : 8-10 º
chemical bonding on the surface
(Structure of OTS SAMs)
(OTS : n-octadecyltrichlorosilane)
cross link
(22~ 25Å)
Inorganic Chemistry, SungKyunKwan Univ.
PDMS
Si
Si
PDMS
PDMS Spin casting of OTS solution
Microcontact printing
Fabrication of patterned OTS SAMs
Ink (OTS solution)
Microcontact Printing
oxide layer
hydrophobic areahydrophilic area
(PDMS : Silicon elastomer)
(OTS SAMs)
Hydrophobicity of OTS SAMs
Moisture
Optical Microscope Image
(Substrate : S i(100) p-type wafer)
OTS SAMs (hydrophobic are
a)
OTS SAMs
Inorganic Chemistry, SungKyunKwan Univ.
( x 10 )
Si
H2O H2O H2O oxide layer
Application of Patterned OTS SAMs
Inorganic Chemistry, SungKyunKwan Univ.
20m 5m
SEM ImageOptical Microscope Image
200m
(selective deposition of CdS) (selective deposition of zeolite)
Si
Si
Si
Si
Patterned OTS SAMs on Si wafer by microcontact printing
Solution deposition of CdS
Sonication of the sample in acetone Obtain selective deposited CdS. H
owever OTS SAMs remain.
Remove OTS SAMs
Procedure of selective deposition of CdSOTS SAMs
Thermal treatmentThermal treatment
0 100 200 300 400 50030
40
50
60
70
80
90
100
110
15min 30min
cont
act a
ngle
(deg
ree)
temperature ( oC)
Water contact angle
Cleaning : nitric acid (60% , ultra sonicatefor10min) ammonia water (5 M , 2-3min)
critical point
Inorganic Chemistry, SungKyunKwan Univ.
Si
SAMsH2OH2O
of OTS SAMs
Substrate : Si (100) p-type Complete Decomposition temp
at 15min above 500 ºC
at 30min above 400 ºC
Bare Si (100) wafer : 37 degree
UV treatmenttreatment
-20 0 20 40 60 80 100 120 140 160
0
20
40
60
80
100
120
con
tact
an
gle
(deg
ree)
time(min)
Water contact angle
Cleaning : piranha solution ( 98% H2SO4 : 28% H2O2 ) = 7 : 3 ( ultra sonicate for 10 min) ammonia water (5 M , 2-3 min)
Substrate : Si (100) p-type UV lamp(high pressure Hg lamp) : 320 nm / 1000W Complete Decomposition time : over 130 min
completely decomposed region
Inorganic Chemistry, SungKyunKwan Univ.
Si
SAMsH2O
of OTS SAMs
Bare Si (100) wafer : 5 degree
Hydrothermal treatmentHydrothermal treatment
Optical Microscope Image(x10)
Substrate : slide glass Cleaning : ammonium persulfate (NH4S2O8) in 1M sulfuric acid (ultra sonicate for 10 min) 28% ammonia water (2-3 min)
Hydrothermal condition 110/120/130/140/150/160/180 ºC , 5 h in DI water
110/120/130/140 ºC : no hydrolysis (patterned OTS SAMs remain upto 140 ºC) 150 ºC : slightly hydrolysis 160/180 ºC : fully hydrolysis
Inorganic Chemistry, SungKyunKwan Univ.
( x 10) ( x 40)plate
of OTS SAMs- slide glass -
(140 ºC) (150 ºC) (160 ºC)
slide glass
slide glassplate plate
slide glass
(180 ºC)
Optical Microscope Image
OTS SAMs
moisture
Hydrothermal treatmentHydrothermal treatment
( x 10)
Si (100) wafer
Substrate : Si (100) p-type wafer
Cleaning : piranha solution ( 98% H2SO4 : 28% H2O2 ) = 7 : 3 ( ultra sonicate for 10 min) ammonia water (5M , 2-3 min)
Inorganic Chemistry, SungKyunKwan Univ.
of OTS SAMs
Hydrothermal condition : 200 ºC, 5 h in DI water
no hydrolysis (patterned OTS SAMs remain up to 200 ºC)
- Si (100) wafer -
TGA (Thermal Gravimetric Analysis) of OTS hydrolysis product (PODS)
Inorganic Chemistry, SungKyunKwan Univ.
poly(octadecylsiloxne) (PODS) : OTS hydrolysis product
OTS +3 H2Owater layer
- 3HCl
TGA(under N2 gas)
0 200 400 600 800 10000
20
40
60
80
100 97%
III
14.7%
F ,
% f
ract
ion
of
init
ial w
eig
ht
temperature( oC)
100 200 30095
100
II
I
(release of H2O)
0 200 400 600 800 10000
20
40
60
80
100
IV
III
18% 6.7%
60%
97%
F, %
fra
ctio
n o
f in
itia
l wei
gh
t
50 100 150 20096.5
97.0
97.5
98.0
98.5
99.0
99.5
100.0
100.5
(2.7%)
(0.8%)
II
I
( release of H2O)
( Parikh et al. J. Am. Chem. Soc., Vol. 119, 1997, 3135 )
TGA (under Air)
(white powder)
Conclusion
Inorganic Chemistry, SungKyunKwan Univ.
In thermal treatment,In thermal treatment, OTS SAMs have tendency that the decomposition increases as the temperature rises. They completely decompose above 400 ºC (30 min) and 500 ºC (15 min).
In UV treatment,In UV treatment, the decomposition of the OTS SAMs increases as the exposed time increases. In addition, they have clearly decomposed when exposed over 130 min.
In hydrothermal treatment,In hydrothermal treatment, OTS SAMs show different behaviors on the surface of silicon and slide glass. OTS SAMs on silicon clearly remain up to 200 ºC (5 h). However OTS SAMs on slide glass remain up to 140 ºC (5 h). Particularly they hydrolyze above 150 ºC (5 h).