Transcript SILICON OXYNITRIDE DEPOSITED BY N2/O2/Ar/SiH4 ECR

INSULATORS MADE BY ECR
PLASMAS ON Si or GaAs
SUBSTRATES AT ROOM
TEMPERATURE
J.A. Diniz, I. Doi and J.W. Swart.
UNICAMP, CCS and DSIF/FEEC,
CEP.13083-970, CP. 6101,
CAMPINAS, SP, BRAZIL.
OUTLINE
CCS/DSIF/UNICAMP
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MOTIVATION
INTRODUCTION
EXPERIMENTS
RESULTS AND DISCUSSIONS
CONCLUSIONS
MOTIVATION
CCS/DSIF/UNICAMP
Silicon Nitrides (SiNx) and Silicon Oxynitrides (SiOxNy)
on Si and GaAs
ECR
N2O HIGH
PLASMA
DENSITY
DEPOSITION
PLASMA
or OXIDATION
atatroom
low temperature
temperature
DEVICE ISOLATION
(LOCOS)
Requirement:
•nitrides with high resistance
to thermal oxidation ( 1000oC);
•reduced bird’s beak after wet
oxidation
GATE DIELECTRIC
Requirement:
•low effective charge density;
•surface passivation
MOS devices
INTRODUCTION
CCS/DSIF/UNICAMP
Silicon nitride (SiNx) or Silicon oxynitride (SiOxNy) films
considerable attention
electrical and physical properties
for enhance
MIS structures
radiation hardening
Barrier against boron diffusion
surface passivation
The improved dielectric reliability
the pile up of the incorporated N in the vicinity of the SiO2/Si interface.
The Si-N bonds replace the strained Si-O bonds at interface,
decreasing the interface strain.
INTRODUCTION
CCS/DSIF//UNICAMP
High-density plasma techniques
ECR and ICP
have been employed for
thin film (SiNx, SiOxNy and SiO2) depositions on
semiconductor substrates, such as Si and GaAs.
ECR systems  remote plasma reactors
•control separately ion energy (RF power) and ion flux (W power).
•operate at low pressure (1-10 mTorr)  reduce ion surface sputtering
•A 2.45GHz W source generates the plasma at high power
•A 13.56 MHz RF power source biases separately the sample chuck.
INTRODUCTION
CCS/DSIF/UNICAMP
ECR SYSTEM
GAS INLET
~
MAGNETIC
FIELD
875GAUSS
ECRWPOWER
2.45GHz
PLASMA
SUBSTRATE
GAS RING
~
VACUUM PUMP
RFchuckPOWER
13.56MHz
INTRODUCTION
CCS/DSIF/UNICAMP
This work - surface passivation with SiNx
•SiNx films deposited on GaAs substrates
to passivate Heterojunction Bipolar Transistor (HBT)
structures ;
Silicon Nitride
Passivation
Emitter
+
Base
n GaAs Cap
AlxGa1-x As
+
p GaAs
n GaAs
+
n GaAs
SI-GaAs Substrate
Collector
INTRODUCTION
CCS/DSIF/UNICAMP
This work - plasma oxidation (without silane)
•SiOxNy insulators obtained by low-energy 28N2+ implantation
(E=5keV/dose=1015cm-2) in Si substrates prior to
high density O2 ECR plasma oxidation
 to gate dielectric for MOS devices;
Metal
Al
SiOxNy
p-type Si (100)
•SiOxNy insulators grown on Si by O2/N2/Ar ECR plasma oxynitridation
 to gate dielectric for MOS devices;.
INTRODUCTION
CCS/DSIF/UNICAMP
This work - SiNx for isolation technology -LOCOS
• SiNx films deposited on SiO2/Si structures
 to verify the masking characteristics
for local oxidation of silicon process.
LOCOS
LOCOS
LOCOS
EXPERIMENTAL
CCS/DSIF/UNICAMP
SiNx films deposited on GaAs substrates
passivation  MIS devices
Cleaned by organic
solvents - Sox-let distillate
n-GaAs (100)
E-beam or
sputtering
evap.
SiNx
Al or WN
C-V
characteristics
n-GaAs(100)
n-GaAs (100)
SiNx deposited by ECR plasma
N2/Ar/SiH4 (2.5/5/200sccm)
1mTorr/250WECR/1Wrf
CN
samples
AuGeNi
Ellipsometry, FTIR,
profile meas.
Silicon Nitride
Passivation
Emitter
HBT
+
Base
n GaAs Cap
AlxGa1-x As
+
p GaAs
n GaAs
+
n GaAs
SI-GaAs Substrate
Collector
I-V characteristics
EXPERIMENTAL
SiOxNy obtained by
O2/N2/Ar ECR plasma oxynitridation
Cleaned by
RCA method
SiOxNy deposited
or oxidized
p-type Si (100)
by ECR plasma
CCS/DSIF/UNICAMP
SiOxNy
p-type Si (100)
13N2/7O2/20Ar/750WECR/10WRF/4mTorr/200C
DEPOSITION
OXIDATION
With SiH4 flow
of 200sccm
Without SiH4
ONCVD samples
ONPO samples
EXPERIMENTAL
SiOxNy obtained by 28N2+ implantation
+ plasma oxidation
CCS/DSIF/UNICAMP
Cleaned by RCA method
GATE DIELECTRIC
Si -p
OXYNITRIDE FORMATION
Dose of
1015/cm2
CTA
N2/1000ºC/20min
+
plasma oxidation
O2 flows=40sccm
500WECR
20W RF/10 mTorr 200C/30
min
ONECR
samples
5keV N2+
Si -p
ION IMPLANTATION
WITHOUT
IMPLANTATION
plasma oxidation
SiOxNy
O2 flows=40sccm
500WECR
20W RF/10 mTorr
200C/30 min
CONTROL
OXIDE
Si -p
COECR
samples
EXPERIMENTAL
CCS/DSIF/UNICAMP
SiOxNy obtained on Si
Physical characterization
•Chemical bonding SiOxNy FTIR.
•Thickness, the deposition (or oxidation) rates
and etch rates in buffered HF  profile measurements
Metal/oxynitride/Si capacitors
e-beam evaporation of
150 nm thick Al film
SiOxNy
p-type Si (100)
Al electrodes  200 m diameter dots.
C-V measurements
Electrical characterization
EXPERIMENTAL
CCS/DSIF/UNICAMP
LOCOS
Cleaned by Dry oxidation SiNx deposited
RCA method for pad oxide by ECR plasma
formation
SiO2
p-type Si (100)
WET OXIDATION
FOR ISOLATION
THICK OXIDE
SILICON
NITRIDE
p-type Si (100)
BIRD’S BEAK
SILICON
NITRIDE
PAD OXIDE
PAD OXIDE
Ellipsometry, FTIR,
profile meas.
LOCAL OXIDATION
SILICON SUBSTRATE
Nitride Deposition Process Parameters
200sccmSiH4/20sccmAr/5mTorr/1000WECR/1WRF/200C
SILICON
NITRIDE
DEPOSITIONS
20sccmN2 -N20
10 sccmN2 - N10
05sccm N2 - N5
2.5sccmN2 -N2.5
SEM
analysis
samples
RESULTS AND DISCUSSIONS
SiNx films deposited on GaAs substrates
SAMPLE
DR
(nm/min)
CN
BHF-ER
(nm/min)
4.8
TN
(nm)
26
nN
CCS/DSIF/UNICAMP
Peak pos.
(cm-1)
48 1.9
856
bond
Qo/q
(1011cm-2)
Si-N-
0.5
LOW DR
Ellipsometry
excellent
passivation
C-V
C (pF)
20.33
(nitride richs in Nitrogen)
Profile meas.
FTIR (Si-N and N-H bonds)
Low porosity
0.035
Si-N
0.3640
/div
16.89
-1.0
absorbance
0.025
0.2/div
1.0
C (pF)
0.02
27.08
N-H2
0.015
0.01
0
(a) Al/CN/GaAs capacitor
Q0/q of 6x1010/cm2
0.03
Low [H]
VF
N-H
N-H
Si-N
0.005
0.71
/div
0.000
4000
3500
3000
2500 2000
Wavenumber
1500
1000
(cm-1)
500
19.98
-1.0
VF
0
0.2/div
(b) WN/CN/GaAs capacitor
Q0/q of 5x1010/cm
1.0
RESULTS AND DISCUSSIONS
SiNx films deposited on GaAs substrates
Silicon Nitride
Passivation
I-V characteristics
HBT
Emitter
0,1
+
Base
CCS/DSIF/UNICAMP
n GaAs Cap
0,01
AlxGa1-x As
+
p GaAs
1E-3
n GaAs
Collector
1E-4
+
Current (A)
SI-GaAs Substrate
an increase in current gain of
over an order of magnitude
100
1E-6
1E-8
nB=1.39
(passivated)
1E-9
1E-10
1E-11
1E-12
0,0
20x16 m
20x6 m
0,2
2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
1,8
2,0
VBE (Volts)
10
passivated
unpassivated
1E-8
nC = 1.05
(passivated)
1E-7
2
1
1E-9
IB
(unpassivated) nB=2.27
1E-5
n GaAs

IC
(unpassivated) nC=1.36
1E-7
1E-6
1E-5
IC (A)
1E-4
1E-3
0,01
Excellent
passivation
with nitride
the base current ideality factor
reduces from 2.27 in the
unpassivated device
to 1.39 in the passivated HBT
RESULTS AND DISCUSSIONS
SiOxNy obtained by 28N2+ implantation
+ plasma oxidation
samples
TN
(nm)
COECR 8.1
ONECR 8.1
nN
Peak pos.
(cm-1)
bond
1.46
1.46
1070
1070
Si-O
Si-O
CCS/DSIF/UNICAMP
Qo/q
Charge density
11
-2
(10 cm )
1 Control oxide
0.6 oxynitride
Ellipsometry
(NO INHIBITION
OXIDATION)
FTIR
C-V
(high quality oxynitride)
Charge Density (Qo/q) (cm-2)
(Si-O, O-Si-N and high quality)
COECR
ONECR
CORP
ONRP
COTOX
ONTOX
1E12
Control
1E11
oxynitride
0
10
20
Time(min) time
Sintering
30
RESULTS AND DISCUSSIONS
CCS/DSIF/UNICAMP
SAMPLE
deposited
ONCVD
ONPO
DR
(nm/min)
BHF-ER
(nm/min)
12.7
0.7
267
43
A b s o r b a n c e ( A .U .)
0 .1 8
0 .1 7
d e p o s ite d O N C V D
o x y n itrid e
0 .1 5
0 .1 4
0 .1 3
0 .1 2
0 .1 1
S i-O -S i
g ro w n O N P O
o x y n itrid e
1100cm
-1
S i-O -N
900 - 1000cm
-1
0 .1 0
1400
1200
1000
-1
W a v e n u m b e r (c m )
Peak pos.
(cm-1)
bond
Qo/q
(1011cm-2)
950
1100
Si-O-N
Si-O
10
0.3
Low
porosity [H]
films
FTIR (Si-O and Si-O-N bonds)
0 .1 6
nN
103 1.57
5 1.46
Low
oxidation
rate
Ultra-thin
films
Plasma
oxidation
TN
(nm)
800
C-V
ONPO   = 4.6
5nm
oxynitride
RESULTS AND DISCUSSIONS
CCS/DSIF/UNICAMP
SiNx for LOCOS
N20
10.3
86.2
DEPOSITION RATE (nm/min)
60
10,5
40
10,0
SiNx ECR-CVD
20Ar/200SiH4/5mTorr
20
BHF ETCH RATE (nm/min)
80
Si-N bond
peak position (cm-1)
2.48 Richs in Si 833
1.94
852
1.90 Richs in N 860
130
1.88
nN
FTIR
(nitrides rich in N
except to N2.5 sample)
(Si-N and N-H bonds
to N5,N10, N20)
Ellipsometry x FTIR
0
1000WECR/1Wrf/5mTorr/20 C
850
840
1000WECR/1Wrf/20 C
0
0
5
10
15
N2 FLOWS (sccm)
20
SiNx ECR
20sccmAr/200sccmSiH4
860
0
9,5
864
Ellipsometry
Profile meas.
N2 flow
ER
Porosity
[H] 100
11,0
TN
(nm)
120
132
139
-1
N2.5
N5
N10
DR
BHF-ER
(nm/min) (nm/min)
9.6
<2
10.5
29.2
11.1
69.4
WAVENUMBER [cm ]
Samples
nitride
richs
in N
nitride richs in Si
830
1,8
2,0
2,2
REFRACTIVE INDEX
2,4
RESULTS AND DISCUSSIONS
CCS/DSIF/UNICAMP
SiNx for LOCOS
(a)
LOCOS with N2.5 Nitride
For LOCOS technology,
SiNx(150nm)/pad-SiO2(50nm)/Si
850nm
880nm
450nm
structures were used.
N2.5 nitrides were oxidized and
not effective mask against
oxidation
N2.5 nitride + pad oxide
850nm field oxide
Silicon substrate
(b)
LOCOS with N5 Nitride
150nm N5 nitride
(c)
Nitreto N20 – 150nm
Pad – 50nm
LOCOS with N20 Nitride
150nm N20 nitride
850nm field oxide
209nm
50nm pad oxide
Bird’s
beak
length of
1 m
874nm
1.09m
870nm field oxide
Silicon substrate
high quality
for LOCOS
isolation
technology
1.32m
850nm field oxide
186nm
50nm
pad
oxide
50nm pad oxide
851nm
Silicon substrate
Silicon substrate
CONCLUSIONS
CCS/DSIF/LPD/UNICAMP
Oxynitrides grown by O2/N2/Ar ECR plasma oxynitridation were obtained
Characteristics:
• thickness of 5.5nm
• dielectric constant of 4.6, which confirms the oxynitride formation
• medium breakdown E-fields of 10 MV/cm
• effective charge densities of about 1010/cm2 for bombardments with
doses up to 1012 protons/cm2
therefore
are suitable gate insulators for MIS devices,
when the proton radiation hardening is a requirement
The deposited oxynitrides presented low quality
as gate dielectric MOS devices.
Acknowledgements
CCS/DSIF/LPD/UNICAMP
The authors would like to thank
CCS/UNICAMP Staff for technical assistance,
and Prof. Dr. Inés Pereyra (LME/EPUSP) for FTIR analysis.
The work is supported by CNPq, AEB, FAPESP and FINEP of
Brazil.