Transcript Role of Hydrogen in Radiation Response of

Role of Hydrogen in Radiation Response of
Lateral PNP Bipolar Transistors
I.G.Batyrev1, R. Durand2, D.R.Hughart2,
D.M.Fleetwood2,1, R.D.Schrimpf2 ,M.Law3 and
S.T.Pantelides1
1Department
2Electrical
of Physics and Astronomy
Engineering and Computer Science Department
Vanderbilt University, Nashville, TN
3Department
of Electrical and Computer Eng., University of Florida
Supported by AFOSR and US Navy
Outline
• Experimental results on H2 diffusion from
NAVSEA Crane
– Strong effect of H2 exposure on BJT rad response
• Multilevel modeling approach
– Hydrogen molecule diffusion, FLOOPS/FLOODS
– First principles calculations
– Interactions of H2 with holes and defects
– H+ with defects near interface
– I(V) curves , ISE TCAD
H2 exposures at Crane (G. Dunham)
• Devices were sealed in 100% H2 atmosphere for various times
at room temperature
– Apparatus used low H2 permeability tubing with vacuum
grease at all seals.
– During H2 soak and irradiation, all pins were tied together.
– System volume is ~0.45 liters. The system was purged with
at least 2 liters of 100% H2 prior to sealing the system. For
long soaks, H2 was added every 6 to 12 hours.
• Devices were irradiated to 10 krad(SiO2) at 40 rad(SiO2)/s at
room temperature
– Devices were tested no later than 2 minutes after completion
of irradiation.
Very strong effect of H2 exposure on
TID response
H2 exposure makes
these bipolar
transistors much
softer
Normalized Peak Base Current
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0
10
20
30
H2 Soak Time (hr)
40
50
All parts were
irradiated to
the same TID
10 krad(SiO2)
Florida Object Oriented Process Simulator
FLOOPS
• Object oriented
• Multi-dimensional
• Complex shapes and edges
• Meshing of oxide and over layers
• TR-BDF time discretization operator for PDE
• Different boundary conditions for different
interfaces of device with packaging
100 % H2
μm
7*1017 cm-3
1.5
1.0
0.5
PSG
PSG
Al
Al
SiO2
3*1017 cm-3
6*1015 cm-3
Al
3*1015 cm-3
SiO2
C
-10
B
10
μm
E
H2 concentration in base oxide, calculated
with FLOOPS
Normalized Peak Base
Current
1.0
0.8
0.6
Rapid increase of
hydrogen in gate
region of bipolar device
due to H2 soak
0.4
0.2
0.0
0
7
10
20
30
40
50
(Hr)
a
Qualitatively similar to
rad response
H2 Soak Time (Hr)
Experimental Ic & Ib(Vbe) curves
Ic, 48 hours H2 soak
1E-02
Ib, 48 hours H2 soak,
postrad
Ic & I b (A)
1E-04
1E-06
Ib, 1 hour H2 soak,
postrad
Ib, 48 hours H2 soak,
prerad
1E-08
1E-10
1E-12
0.2
0.3
0.4
0.5
0.6
Base Voltage (V)
Data from NSWC Crane
0.7
0.8
First principles calculations
• Activation energies
• Cross-sections and rates of reactions
- generation of protons
- depassivation of Si-H bonds near interface
• Discretization of the rate equations in a particular
device geometry
p(x,t), n(x,t), CH+ (x,t), ΔNit(x,t)
Simulation of effect of interface trap density ΔNit
on Ic & Ib(Vbe) curves
Ic
1E-05
Ib, ΔNit ~ 1011 cm-2
Ic & Ib (A)
1E-07
Ib, ΔNit ~1010 cm-2
1E-09
Ib, ΔNit < 109 cm-2
1E-11
1E-13
1E-15
0.2
0.3
0.4
0.5
Vbe (V)
0.6
0.7
Conclusions
• Exposure to H2 dramatically affects radiation response
– Overlayers affect H2 transport
– H2 diffuses through oxides and reacts to form interface traps
• Multi-scale simulation approach developed
– H2 transport
– Charge transport and trapping
– Interface-trap formation
– Transistor-level degradation
• Data base of hydrogen properties in microelectronic
materials produced
– Diffusivities
– Activation energies