Hydrogen 2007 1
Studying the Effect of Molecular Hydrogen on Silicon Device Radiation Response
Using Gated Bipolar Transistors
Jie Chen, David Wright, and Hugh BarnabyElectrical Engineering, ASU, Tempe, Az
Hydrogen 2007 2
Topics of Discussion
• Motivation for the study
• Background
• Initial experimental results
• Modeling the effect of molecular hydrogen
• Recent experimental results
• Experimental data vs. model
• Summary
Hydrogen 2007 3
Motivation of Study
1.E-09
1.E-08
1.E-07
1.E-06
-100 -80 -60 -40 -20 0Vg (V)
Ib (A
)
sealed @ 30kradunsealed @ 30Krad after 8 days
Previous experiments showed 3x increase in Nit in devices in sealedpackages compared toun-sealed ones.
ΔNot (cm-2) ΔNit (cm-2)
Unsealed ~1.7x1011 ~0.8x1011 0.00005% H2
Sealed ~1.4x1011 ~2.5x1011 1.3% H2
Sealed package
Unsealed package
Hydrogen 2007 4
Post-irradiation annealing in H2
After Mrstik & Rendell, IEEE Trans. Nucl. Sci., 1991
• MOSFETS exposed to 10Mrad and 1Mrad 10KeV x-rays.
• Post-irradiation annealing in 100%, 10%, and 1% H2 environment.
• Results show increase in Nit after annealing in H2.
Increase in Nit
Increase in Nit
Hydrogen 2007 5
Earlier Experiments
NAVSEA Crane performed HDR testing performed at NAVSEA on devices in 100% H2
1.E-09
1.E-08
1.E-07
1.E-06
-100 -80 -60 -40 -20 0Vg (V)
Ib (A
)
preradIrrad in airIrrad in 1.3% H2Irrad in 100% H2
0
5E+10
1E+11
1.5E+11
2E+11
2.5E+11
0 10000 20000 30000 40000
Total Dose (rad)
del N
it (c
m̂-2
)
Air (unsealed)1.3% H2 (sealed)100% H2 (unsealed)
Increase in Nit
Hydrogen 2007 6
Interface Trap Formation:2 stage model
Si-SiO2
interface
-+
-
+
-
+H
-
+fH
tox
Ionizing radiation
H
xd
H
DH volume
fp
H+
H+
- protons
- Si-H (NSiH)
- dangling bond (Nit)
H
H+
fH- proton flux
- hydrogen defect (D’H)
H+
HDH DH p
f HN fx t
it itSiH it it H
it
N N (t)N N (t) σ ft
After Mclean TNS 1980Rashkeev et al. TNS 2002
Hydrogen 2007 7
Model:Impact of Molecular H2
Si-SiO2interface
-+
-
+
-
+H
-
+fH
tox
Ionizing radiation
H
xd
H
D’H volume
fp
H+
H+
H+
Si-SiO2interface
-+
-
+
-
+H
-
+fH
tox
Ionizing radiation
H
xd
H
D’H volume
fp
H+
H+
H+
Empty D centers
HH
HH
H2 molecules
Molecular hydrogen reacts with empty D centers to generate more DH centers
2DH2DH2
HH
DHcenters
H
H
H
H2 transportinto material
21
H2
21H1
DH2
2
Nk1Nk
N
Rad-inducedholes
Hydrogen 2007 8
1D Analytical Model
2
2
12
1 212
2
21
oDH DH SiH it g y oH
it
H
x
k ( )N ( N Dk f t t )
NN
N/
k ( )
Note: final 1D model assumes steady state, no Nit saturation or annealing
21
H2
21H1
DH2
2
Nk1Nk
N
Equil. H2 - DH model Steady state hole transport
oxygp tfkDf (fp > 0 for all x)
HDH DH p
f HN fx t
Proton continuity
it itSiH it it H
it
N N (t)N N (t) σ ft
Trap continuity
Final Model
*
Hydrogen 2007 9
Latest Experiments
• GLPNP devices used are designed by NAVSEA Crane and fabricated using National’s standard linear bipolar IC process
• Using only devices with no-passivation (Wafer #4) for simplicity (one less parameter in modeling)
• 10%, 0.1%, 0.01%, 50% H2 ambient concentrations, as well as re-examination of 1% and 100% data points
GLPNP with no passivation
Hydrogen 2007 10
Experimental Details
• 4 device samples for each H2 concentration
• De-seal lids at least 3 days prior to soaking
• 10-5 torr vacuum before filling of H2
• >48hrs soaking before irradiation
• Gamma HDR test to 30Krad at 18 rad/s
• Pb shield used during irradiation
• Devices grounded during irradiation
• Soaking temperature: 72 deg F
• Irradiation temperature: 72 deg F H2 Chamber (Soaking & Irradiation)
Hydrogen 2007 11
Latest Experimental Results• Characterization performed using Agilent 4156 SPA. Gate Sweep (GS),
Subthreshold Sweep (SS), and Gummel are performed.
• Gate Sweep: VG = 80V to -100V, VBE = 0.5V, VC = 0V
Hydrogen 2007 12
Latest Experimental Results• Subthreshold Sweep: Vg = 10V to -100V, VE = -0.1V as the drain of the
pMOSFET, VC = 0V, VB = 0V.
Hydrogen 2007 13
1D model fit to data
• ASU results indicated monotonic increase of Nit vs ambient H2 concentration, agrees with the predictions of the model.
• Saturation at high H2 and low H2 concentration agrees with the predictions of the model,
• Crane’s 100% data is different than ASU’s 100% data. The difference may be due to differences in dose, dose rate, environmental factors, etc.
Re-fit of the data with the analytical model
Hydrogen 2007 14
Continuing work
• Post-irradiation annealing studies
• Effect of high pressure H2 environment
• Model refinement
• Relate dose-rate effects to the reaction processes of hydrogen species in SiO2
• Effect of H2 under low temperature exposure