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MURITotal Ionizing Dose Effects in Bulk
Technologies and Devices
Hugh Barnaby, Jie Chen, Ivan SanchezDepartment of Electrical EngineeringIra A. Fulton School of Engineering
Arizona State University
Outline
Overview of ASU tasks
Total ionizing dose defect models
Device TID responseo Drain-to-source leakage
o Inter-device leakage
Analysis of defect buildup across oxide structure and between technologies
Other work
ASU task
• Characterize and model TID effects in modern devices, primarily CMOS transistors
• Technologies: deep sub-micron bulk CMOS, and silicon on insulator, general isolations
ASU task
• Characterize and model TID effects in modern devices, primarily CMOS transistors
• Technologies: deep sub-micron bulk CMOS, and silicon on insulator, general isolations
In Year 1, we have primarily focused ondeep-sub-micron bulk CMOS and generalisolation technologies.
Primary TID Threat
TID defect build-up in the “thick” shallow trench isolation (STI)
Defects
• Not - oxide trapped charge (E’ )• Nit – interface traps (Pb)
Both Nit and Not are related to holesgenerated and/or hydrogen present inoxide
Not, Nit tox
first orderassumption
STI
Gate oxide
halo implants
n+ source n+ drain
p-body
STI
> 300 nm < 3 nm
Trapped charge buildup in STI
oxotygot tεfεfDkΔN
After Fleetwood et al. TNS 1994
Model Parameters
Model for Not buildup
D - total dose [rad]
kg - 8.1 x 1012 [ehp/radcm3]
fy - field dependent hole yield [hole/ehp]
fot - trapping efficiency [trapped hole/hole]
tox - oxide thickness [cm]
Hole trapping processes
+
+ - surviving hole (p)
- hole trap (NT)
- trapped hole (Not)
fp- hole flux
area =
Si-SiO2
interface
-+
-
+
-
+ +
-
+ +fp,i
tox
Ionizing radiation Si-SiO2
interface
-+
-
+
-
+ +
-
+ +fp,i
tox
Ionizing radiation
ip,T
otpotT
ot
σfN
(t)Nσf(t)NN
t
N
After Rashkeev et al. TNS 2002
Simple analytical model (Not)
yg
ygp
fkD
t
pfkD
x
f
oxygip, tfkDf (steady state) (fp > 0 for all x)
oxygTot tftkDσNN
fot D(No saturation or annealingand traps at interface)
oxitDHygit tffεfDkΔN
After Rashkeev et al. TNS 2002
Model Parameters
Model for Nit buildup
D - total dose [rad]
kg - 8.1 x 1012 [ehp/radcm3]
fy - field dependent hole yield [hole/ehp]
fDH - hole, D’H reaction efficiency [H+/hole]
fit - H+, SiH de-passivation efficiency [interface trap/H+]
tox - oxide thickness [cm]
De-passivation processes
- protons
- Si-H (NSiH)
- dangling bond (Nit)
area = it
H
H+
fH - proton flux
- hydrogen defect (D’H)
Si-SiO2
interface
-+
-
+
-
+
H
-
+fH
tox
Ionizing radiation
H
xd
H
D’H volume
fp
H+
H+
HitSiH
it
itHititSiH
it
fσN
(t)Nfσ(t)NN
t
N
After Rashkeev et al. TNS 2002
De-passivation processes
pDHDH
pDHDHH
fNt
HfN
x
f
doxDHygH xtffkDf
oxyDHgSiHit tfftkDσNN
fitD
(fH > 0 for all x)(steady state)
(No saturation or annealingand traps at interface)
Leakage paths
1 2
3
1
2
3
NMOS Drain-to-Source
NMOS D/S to NMOS S/D
NMOS D/S to NWELL
Defect build-up in STI creates leakage paths in CMOS ICs.
CMOS inverters
2 and 3 are inter-device leakage
NMOS drain-to-source leakage
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
0 0.2 0.4 0.6 0.8 1 1.2 1.4
0k
100k
500k
No
rm. d
rain
cu
rren
t [A
/m
]
gate-to-source bias [V]
VG = 1.32V20 rad/s
Polysilicongate
N+ drain
N+ Source
LeakageLeakage
Polysilicon gate
N+ drain
N+ Source
LeakageLeakage
Polysilicongate
N+ drain
N+ Source
LeakageLeakage
Polysilicon gate
N+ drain
N+ Source
LeakageLeakage
130 nm bulk CMOS
Increasingtotal dose
Parasitic leakage model
“as drawn” “edge”
Weff
tOX-eff
VTH-eff“as drawn” “edge”
Weff
tOX-eff
VTH-eff
• Parasitic “edge” device modeled as MOSFET operating in parallel with “as drawn” FET.
• “Effective” parameters for “edge” device are extracted from data.
Extracting electrical characteristics
ID“edge”(post) ≈ IDtotal(post) – IDtotal(pre)
ID“edge”(post)
IDtotal(post)
IDtotal(pre)
Two assumptions:
1. IDtotal(pre) ≈ ID“as-drawn”(pre)
2. ID“as-drawn”(post) ≈ ID“as-drawn”(pre)
“Edge” Capacitor
Prior to radiation exposure, the
MOS capacitor of the “edge” device has small dimensions, W and tox
STI
Weff tox-eff
++
++
++
“Edge” Capacitor
Upon radiation exposure, the “edge capacitor is degradedand the dimensions enlarged.
STI
Weff tox-eff
++
++
STI
Weff
tox-eff
++
+ ++
++
Increasingtotal dose
++
“Edge” Capacitor
Increased defect buildup in theSTI sidewall leads to further increases in W and tox, until inherent limitations are met.
STI
Weff tox-eff
++
++
STI
Weff
tox-eff
++
+ ++
++
Increasingtotal dose
++
STI
Weff tox-eff
++
+ ++
+++
++++
++++
+++
+
2D simulations
Not = 2×1012 cm-2 Not = 5×1012 cm-2 Not = 7×1012 cm-2
Simulations show how increased Not along sidewall increases the width of the channel and the capacitor thickness
Weff Weff
Weff
New Test Structure
Devices designed by Faccio and fabricated at STMicro enable measurements on sidewall capacitor.
•1.3 um
•90 um
overlap
Pre-rad
Parameter extraction
1.00E-16
1.00E-14
1.00E-12
1.00E-10
1.00E-08
1.00E-06
1.00E-04
-0.5 0 0.5 1 1.5
gate bias (V)
drai
n cu
rren
t (A
) 100 krad
500 krad
1 Mrad
Series1
Series2
Series3
Expon.(Series1)Expon.(Series2)Expon.(Series3)
Img (1 Mrad)
2 1
3
4
Img (500 krad)
Img (100 krad)
1. Weff increases withTID (increased strong -inv current)
2. Not and Nit increase with TID (shift in threshold voltage)
3. Nit and tox increasewith TID (reducedsubthreshold slope)
4. Not increasewith TID (shifts inmidgap voltages)
Simultaneous equations
dsF
22
-qV /kTq2φ /kTsi a ids S F eff
F
e f
a
f ε qN kT nI (φ = 2φ ) =μ e (1-
L 4φ
We )
q N
si a B OTOX-efmg FB F f
OX
2ε qN φ - qV = V + φ +
ε
Nt
ITb
OX-ef
XO f
C + qn = 1+ ( )
ε
Dt
OX dsds eff gs TH-ef
eff
OX-efds
ff
ε VI = μ (V - V ) -
tV
L 2
W
1.
2.
3.
4.Solving simultaneouslyenables extraction ofparameters and defectlevels at each TID value
Parameters and sidewall defects
VTH-eff (V) tOX-eff (nm) Weff (nm)
pre N/A N/A N/A
100 krad 0.194 17.9 43.7
500 krad 0.180 17.9 99.9
1 Mrad 0.169 20.0 128.1
Parameters
Defects
Not (cm-2) NIit (cm-2)
100 krad – 500 krad 8.5×1010 6.4×1010
100 krad – 1 Mrad 1.0×1011
1.2×1011
Inter-device leakage
Aluminum line Polygate
Polygate
p+ p+n+n+
Aluminum gate
+++ + + + + + + + + + + + +
++
n+ p+n+
Leakage path
n+
p+ n+
n-well
n-well
VDD0V
Aluminum line Polygate
Polygate
n+ n+n+n+
Aluminum gate
+++ + + + + + + + + + + + +
++
n+ n+ n+n+
Aluminum line Polygate
Polygate
n+ n+n+n+
Aluminum gate
+++ + + + + + + + + + + + +
++
n+ n+ n+n+
Leakage path
VDD0V
n+ D/S to n-well n+ D/S to n+ D/S
Charge build-upin STI base
Field oxide transistors
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
0 10 20 30 40
gate-to-source bias [V]
dra
in c
urr
en
t [A
]
50k
100k
500k
130 nm bulk CMOS
noisefloor
p-well
STIn+ n+
n-well
-n+ D/S
n+ D/S n-well
n-well
Metal 1
Metal 1
++++
Field oxide capacitors
1500 Single Cell FOXCAPs in parallel
gate area of individual cell ~ 7.4 μm x 11.4 μm
Single cell
0.97
0.98
0.99
1
-40 -30 -20 -10 0 10 20 30
Gate Voltage [V]
Nor
mal
ized
Cap
actia
nce
Pre-rad
Rad-inducedshift
After 1-weekanneal
0.97
0.98
0.99
1
-40 -30 -20 -10 0 10 20 30
Gate Voltage [V]
Nor
mal
ized
Cap
actia
nce
Pre-rad
Rad-inducedshift
After 1-weekanneal
130 nm data
Defect build-up in STI base
Total Dose [krd(Si)]
Def
ect
s [c
m-2
]
Defect build-up is:
1. Greater for higher oxidefields (consistent w/ fy)
2. Linear with dose(no saturation … yet)
Comparison to other isolation technologies (Not)
Device tox (nm) Type Area (cm2) ∆Vot (V) K (x 103)
FOXCAP 320 p 0.0023 6.5 63.5
RF25 600 p 0.0012 4.175 11.6
XFCB 600 p 0.0070 6.12 17
E4403/W21* 1080 n 0.030 7.7 33.01
SIMOX 370 n 0.022 2.2 16.07
*data taken after 20 krad(SiO2) exposures
**radiation bias is 0V for all devices
yotox
g
2ox
ot ffε
qk
Dt
ΔVK
Sidewall vs. Base Comparison (Not)
01E+162E+163E+164E+165E+166E+167E+168E+16
100 400 700 1000Total Ionizing Dose (krad)
No
rmal
ized
No
t
STI sidewall
STI base
Indicates saturation in defect buildup
500 k 1000k
STI sidewall .0147 .0068
STI base .0109 .0094
otyff
Sidewall vs. Base Comparison (Nit)
0
1E+16
2E+16
3E+16
4E+16
5E+16
6E+16
7E+16
100 400 700 1000
TID (krad)
NIT
(n
orm
. to
ox
ide
thic
kn
ess
)STI sidewall
STI base
Other Work
• Separation of switch state defects in thick isolationoxides using frequency dependent charge pumping
• Packaging issues
Gate sweep data
12 umbase
collector
gate
emitter
12 umbase
collector
gate
emitter
Nss
Nss
Increased current is caused by switching state buildup (Nss) whichis composed of both interface and border traps
Separation of Switching States
Indicates border traps
Packaging IssuesGate Sweep (Crane)
1.E-09
1.E-08
1.E-07
1.E-06
-100 -80 -60 -40 -20 0
Vg (V)
Ib (
A)
sealed @ 30krad
unsealed @ 30Krad after 8 days• Recent testing showed
3x increase in Nit in GLPNP devices packaged with sealed gold plated kovar lids than packages with taped-on lids.
ΔNot (cm-2) ΔNit (cm-2)
Unsealed ~1.7x1011 ~0.8x1011
Sealed ~1.4x1011 ~2.5x1011
It’s a hydrogen problem
• As sealed lid is removed, H2 moves quickly out of the package and a concentration gradient is established for the remaining H2 in the oxide to diffuse out, thus reducing Nit generation.
100.00000.001917. Xenon
100.00000.000516. Krypton
100.00000.006415. NH3
100.00000.001314. Fluorocarbons
100.00000.003313. Tot. HC and Org.
100.00000.135212. Carbon Dioxide
100.00000.003211. Argon
100.00000.132610. Oxygen
100.00000.00009. Carbon Monoxide
100.000098.25088. Nitrogen
100.00000.00007. Neon (22)
100.00000.00146. Neon (20)
0.50000.09685. Water
100.00000.00584. Methane
100.00000.00143. Helium (4)
100.00000.00002. Helium (3)
100.00001.35931. Hydrogen
LIMIT in %
Volume % (1%=10,000ppm)
GASSES ANALYZED
100.00000.001917. Xenon
100.00000.000516. Krypton
100.00000.006415. NH3
100.00000.001314. Fluorocarbons
100.00000.003313. Tot. HC and Org.
100.00000.135212. Carbon Dioxide
100.00000.003211. Argon
100.00000.132610. Oxygen
100.00000.00009. Carbon Monoxide
100.000098.25088. Nitrogen
100.00000.00007. Neon (22)
100.00000.00146. Neon (20)
0.50000.09685. Water
100.00000.00584. Methane
100.00000.00143. Helium (4)
100.00000.00002. Helium (3)
100.00001.35931. Hydrogen
LIMIT in %
Volume % (1%=10,000ppm)
GASSES ANALYZED
H2
H2
H2
H2
H2
H2H2
H2
H2
H2
H2
H2
H2
H2H2
H2
H2
H2
H2
H2
H2
H2 H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2H2
H2H2
H2 H2H2
H
H
H
H
H
H2 ~ 1.3%
H2
H2
H2
H2
H2
H2H2
H2
H2
H2
H2
H2
H2
H2H2
H2
H2
H2
H2
H2
H2
H2 H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2H2
H2H2
H2 H2H2
H
H
H
H
H
H2 ~ 1.3%
ox
Si
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2 H2
H2
H2
H2
H2
H2
H2
H2
H2 H2
H2
H2
H2
H2<<1.3%
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2H2
H2
H2
H2
H2
H
H
H
H
H
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2 H2
H2
H2
H2
H2
H2
H2
H2
H2 H2
H2
H2
H2
H2<<1.3%
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2
H2H2
H2
H2
H2
H2
H
H
H
H
H
Another time dependent process
Results shows time dependence of Nit build-up related hydrogen out diffusion … we are working on the rate equations for this
Peak Base Current Vbe = 0.5V, 30Krad
0.0E+00
2.0E-08
4.0E-08
6.0E-08
8.0E-08
1.0E-07
1.2E-07
1.4E-07
1.6E-07
seal (30K) 1h (30K) 13h (30K) 7d (30K)
Time
Ib (
A)
lid off
taped kovar
taped ceramic
Not (cm-2) Nit (cm-2)
Sealed ~1.7x1011 ~2.4x1011
Unsealed 1hr
~1.6x1011 ~1.5x1011
Unsealed 13hrs
~1.6x1011 ~6.9x1010
Unsealed 7days
~1.6x1011 ~6.1x1010