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1. SiO2properties and applications.
2. Thermal oxidation basics.
3. Manufacturing methods and equipment.
4. Measurement methods.
5. eal!gro"e model #linear parabolic model$.
%. Thin oxide gro&th' dependence on gaspressure and cr(stal orientation
). *l!containing gas' 2 gro&th' substratedoping e+ect .
,. -nterface charges' dopant redistribution.
Si(s) + O2(g) SiO2(s)
*hapter % Thermaloxidation and the
SiSiO2interface
1
3 Microfabrication and thin lm technolog(ctor o *ui' 0*0' ni"ersit( of aterloo6 httpece.u&aterloo.ca7bcuio8 Silicon 9:S- Technolog( b( ;lummer' eal and
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;roperties of thermall( gro&n SiO2
-t is amorphous.
Stable' reproducible and
conformal SiO2gro&th Melting point 1)>>*
ensit( 2.21 gcm3#almostthe same as Si that is 2.33gcm3$
*r(stalline SiO2?@uartAB C2.%5gmcm3
Dtomic densit( 2.31>22moleculescm3
#Eor Si' it is 51>22
atomscm3
$ Fefracti"e index nC1.4%
ielectric constant C3.G #&h( notCn2H$
0xcellent electrical insulator
resisti"it( I 1>2>cm' energ(gap 0gC,!G e9.
Jigh brea8do&n electric eld I1>)9cm
*onformalgro&th
2
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3
The perfectinterface bet&een Si and SiO2is one
maKor reason &h( Si is used for semiconductor
de"ices #instead of
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STI
Dpplication of SiO2in -* industr(
4
9er( good etching selecti"it( bet&een Si and SiO2using JE
ST- shallo& trench isolation
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i+usion mas8 for commondopants
SiO2can pro"ide a selecti"e mas8
against
di+usion at high temperatures. #SiO2 si$
Oxides used for mas8ing are >.5!1Nm thic8.
SiO2mas8s for and ;
#not good for
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:ocal Oxidationof Si #:O*OS$
)
Eull( recessed process
attempts to minimiAe birdPspea8.
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Eor nanofabrication oxidationsharpening for sharp DEM tips or eld
emitters for displa(
Si
SiO2
ing' QSilicon Eield 0mission Drra(s ith Dtomicall(Sharp Tips Turn!On 9oltage and the 0+ect of TipFadius istributionR' 2>>2.
Eield emission displa( #E0$
,
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Oxide Structure
asic structure of silica a silicon
atom tetrahedrall( bonds to fourox(gen atoms
The structure of silicon!silicondioxide interface some silicon
atoms ha"e dangling bonds. G
Dmorphous tetrahedral net&or8
ridging ox(gen /on!bridging
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Single cr(stal#quartA$2.%5 gcm3
Dmouphous#thermal oxide$.2.21 gcm3
Oxide Structure
1>
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1. SiO2properties and applications.
2. Thermal oxidation basics.
3. Manufacturing methods and equipment.
4. Measurement methods.
5. eal!gro"e model #linear parabolic model$.
%. Thin oxide gro&th' dependence on gaspressure and cr(stal orientation
). *l!containing gas' 2 gro&th' substratedoping e+ect .
,. -nterface charges' dopant redistribution.
11
*hapter % Thermaloxidation and the
SiSiO2interface
343 Microfabrication and thin lm technolog(
ructor o *ui' 0*0' ni"ersit( of aterlootboo8 Silicon 9:S- Technolog( b( ;lummer' eal and
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r( and &et oxidation
r( oxidation Si#s$ O2#g$ SiO2#s$6 etsteam oxidation Si#s$ 2J2O#g$
SiO2#s$ 2J2#g$ oth t(picall( G>>!12>>*' &et oxidation is about 1>faster than dr(oxidation.
r( oxide thin >.>5!>.5m' excellent insulator' for gate oxides6 for "er(thin gate oxides' ma( add nitrogen to form ox(nitrides.
et oxide thic8 2.5 m' good insulator' for eld oxides or mas8ing.@ualit( su+ers due to the di+usion of the h(drogen gas out of the lm'&hich creates paths that electrons can follo&.
Foom temperature Si in air creates Qnati"e oxideR "er( thin 1!2nm'poor insulator' but can impede surface processing of Si.
9olume expansion b( 2.2#C1>.4%$' so SiO2lm has compressi"e
stress.
=>.4%
Si &afer Uoxis nal oxide thic8ness
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1. SiO2properties and applications.
2. Thermal oxidation basics.
3. Manufacturing methods and equipment.
4. Measurement methods.
5. eal!gro"e model #linear parabolic model$.
%. Thin oxide gro&th' dependence on gaspressure and cr(stal orientation
). *l!containing gas' 2 gro&th' substratedoping e+ect .
,. -nterface charges' dopant redistribution.
13
*hapter % Thermaloxidation and the
SiSiO2interface
343 Microfabrication and thin lm technolog(
ructor o *ui' 0*0' ni"ersit( of aterlootboo8 Silicon 9:S- Technolog( b( ;lummer' eal and
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Thermal silicon oxidation methods
D three!tubehoriAontalfurnace&ith multi!Aonetemperature control
9erticalfurnace
#not popular$ 14
et oxidation using J2and O2is
more popular #cleaner$ than using
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The tubular reactor made of quartA or glass' heated b(resistance.
Ox(gen or &ater "apor Vo&s through the reactor and pastthe silicon &afers' &ith a t(pical "elocit( of order 1cms.
Thermal oxidation equipment
15
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1. *lean the &afers #F*D clean' "er( important$
2. ;ut &afers in the boat
3. :oad the &afers in the furnace4. Famp up the furnace to process temperature in /2#pre"ents oxidation
from occurring$
5. StabiliAe
%. ;rocess #&et or dr( oxidation$
). Dnneal in /2. Dgain' nitrogen stops oxidation process.,. Famp do&n
Thermal oxidation in practice
1!
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1. SiO2properties and applications.
2. Thermal oxidation basics.
3. Manufacturing methods and equipment.
4. Measurement methods #mechanical' optical'electrical$.
5. eal!gro"e model #linear parabolic model$.
%. Thin oxide gro&th' dependence on gaspressure and cr(stal orientation
). *l!containing gas' 2 gro&th' substratedoping e+ect .
,. -nterface charges' dopant redistribution.
1)
*hapter % Thermaloxidation and the
SiSiO2interface
343 Microfabrication and thin lm technolog(
ructor o *ui' 0*0' ni"ersit( of aterlootboo8 Silicon 9:S- Technolog( b( ;lummer' eal and
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Oxide etched a&a( b( JE
o"er part of the &afer and amechanical st(lus is draggedo"er the resulting step.
Surface prolometr( #e8ta8$mechanical thic8ness
measurement
Stylus
1,
Mirror image of st(lus
st(lus
can also be used for thic8ness measurement. atomic force microscop($
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Thic8ness determination b( loo8ing the color
Oxide thic8ness for constructi"e interference #"ie&ed from abo"e C>o$UoC82n' nC1.4%' 8C1' 2' 3L
Our e(e can tell the color di+erence bet&een t&o lms ha"ing 1>nmthic8ness di+erence.
Eilm thic8ness #nm$
Felati"eillum
inationintensit(
1!
O i l hi 8 lli
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L igh t
source F il te r P o la r ize r
Q u a r t e r
w a v e p l a te
S ubs t r a t e
F i l m b e in g
me a su r e d
D e t e c t o rA n a l y z e r
Dfter quarter &a"e plate' the linear polariAed light becomes circularpolariAed' &hich is incident on the oxide co"ered &afer.
The polariAation of the reVected light' &hich depends on the thic8nessand refracti"e index #usuall( 8no&n$ of the oxide la(er' is determinedand used to calculate the oxide thic8ness.
Multiple &a"elengthsincident angles can be used to measurethic8nessrefracti"e index of each lm in a multi!lm stac8.
Optical thic8ness measurement ellipsometr(
er( accurate #1nm accurac($
2>
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0lectrical thic8ness measurement *!9 of MOSE0T
Substrate is /!t(pe. 0lectron ismaKorit( carrier' hole is minorit(carrier.
a. Dccumulation positi"e gate"oltage attracts electrons to
the interface.b. epletion negati"e gate
bias pushes electrons a&a(from interface. /o charge atinterface. T&o capacitance inseries.
c. -n"ersion further increase
SmallAC"oltage is
applied on top of the* "oltage forcapacitancemeasurement.
21
0+ t f f f D* it
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;!t(pe substrate here#pre"ious slide /!t(pe$
0+ect of frequenc( for D* capacitance measureme
Dtafter in"ersion
Eor lo& frequenc(' #minorit($ charge
generation at the interface canfollo& the D* eld to balance thecharge at the gate' so *in"C*ox.
Eor high frequenc(' the gate chargehas to be balanced b( the carrierdeep belo& the interface' so *in"
!1C
*ox!1
*Si!1
.eep depletion for high scanningspeed #the DC"oltage scan fast intolarge positi"e "oltage$' depletiondepth Udmust increase to balance
the gate charge.
22
;arameter from *!9measurement ielectric constant of Si W
SiO2 *apacitor area Oxide thic8ness -mpurit( prole in Si
Threshold "oltage of MOScapacitor
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