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Electrical OverStress on large
discrete components
Fabrice ROQUETA – TCAD team – ST Tours
IMAPS – Thermal Management Workshop
February 2017
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Contents
1. Introduction
2. Approaches
1. “Global” approach
2. “Local” approach
3. Intermediate approaches
3. Conclusion & Outlooks
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Introduction
Introduction
Approaches
Conclusion & Outlooks
IMAPS - Thermal Management Workshop – February 2017
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Aim of the studygeneral purpose
• Focus on 2 main ST Tours products :
• Protection diodes (Transient Voltage Suppressor component (TVS))
• Rectifiers (SiC and Si diodes)
• These components have to withstand transient high current, therefore relative high temperature→ optimization of these components
• Electrical behavior
• Thermal behavior
• Use of simulation
• To avoid these failures
• To optimize
• To improve performances
• To evaluate cost reduction
4
Need of electro-thermal simulation ?
How to do simulations ?
IMAPS - Thermal Management Workshop – February 2017
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Aim of the studyWhy electro-thermal model is needed?
• Si/SiC properties depending on temperature
• Carrier mobility
• Intrinsic density
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Breakdown voltage
Resistance Thermal behavior
IMAPS - Thermal Management Workshop – February 2017
Voltage signal
with Temperature
without Temperature
Current signal
Need of electro-thermal simulation ? YES but how ?
Difference between
with vs. without Temperature
~ 20% Energy increase
~ 50% Temperature increase
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Possible approaches for surge simulation
• For transient Electrical OverStress simulation electro-thermal simulation is necessary
• How to simulate ? Which structure is the most representative ?
• Different approaches possible:
• 0D electro-thermal simulation (‘‘global approach’’)
• 3D electro-thermal simulation (‘‘local approach’’)
• Intermediate approaches
• 2D electro-thermal simulation
• 2D/3D electro-thermal simulation (weak or strong coupling)
• … other possibilities ?
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Approaches
Introduction
Approaches
Conclusion & Outlooks
IMAPS - Thermal Management Workshop – February 2017
o 0D electro-thermal simulation (‘‘global’’ approach)
o 3D electro-thermal simulation (‘‘local’’ approach)
o Intermediate approaches
• 2D electro-thermal simulation
• 2D/3D electro-thermal simulation (weak or strong coupling)
• other possibilities ?
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0D electro-thermal approach (1/1)
• Advantages
• Easy to implement
• Calculation time
• Easy to use
8
• Drawbacks
• Geometry limitations
• Hot spot localization
useless for optimization
• Models based on exp. characterization
weak level of predictability
Limitations of this approachIMAPS - Thermal Management Workshop – February 2017
Electrical
model
)(tI
))(,( tITVF j
Dissipated power
TcaseThermal
model
),(' TjtZth
)(tT j
Junction temperature
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inputs outputs
• 3D structure (with die + package)
• Doping profile
• Boundary Conditions
• Electrical conditions
• Thermal conditions• Natural convective transfer coefficient
• Fixed Temperature or heat transfer coefficient
• Meshing criteria
• Topology / Doping profile
• Temperature distribution
(iterative remeshing)
3D electro-thermal approach (1/3) 9
IMAPS - Thermal Management Workshop – February 2017
Current Density
Temperature Heat flux
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3D electro-thermal approach (2/3) 10
IMAPS - Thermal Management Workshop – February 2017
IFSM peak time 35 µs 200 µs 10 ms
Exp. results
Sim.results
at 17.5µs at 100µs at 5.5ms
Failure localized
at periphery
Failure localized
at periphery
Large die melting
area
Good correlation for hot spot localization between Exp. and Sim.
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3D electro-thermal approach (3/3)
• Advantages
• No geometry limitation
Close to real device
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• Drawbacks
• Calculation time
• Meshing
Not always possible
OK simple structure in forward mode
Possible for large structure in forward
mode but lack of accuracy
Not possible for diode in reverse
mode
• Device working in reverse mode
• Depletion width ~ 0.1 µm
• Current generation in this layer
due to avalanche effect
→ need to describe accurately Electric
Field
→ element size ~ 0.01 µm !!!
- affordable in 2D
- not yet in 3D
(due to the number of elements)
Limitations of this approachIMAPS - Thermal Management Workshop – February 2017
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Approaches
Introduction
Approaches
Conclusion & Outlooks
IMAPS - Thermal Management Workshop – February 2017
o 0D electro-thermal simulation (‘‘global approach’’)
o 3D electro-thermal simulation (‘‘local approach’’)
o Intermediate approaches
• 2D electro-thermal simulation
• 2D/3D electro-thermal simulation (weak or strong coupling)
• other possibilities ?
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inputs outputs• Doping profile
• Boundary conditions• Electrical
• Thermal
• Meshing criteria• Doping profile• Previous Electrical and thermal simulation results (iterative remeshing)
2D electro-thermal approach (1/2) 13
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2D electro-thermal approach (2/2)
• Advantages
• Easily meshed
• CPU time
accuracy
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• Drawbacks
• Geometry limitations
• 3D device layout
• Taking into account wires / package
Not always possible
Limitations of this approachIMAPS - Thermal Management Workshop – February 2017
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Coupling between 2D electro-thermal simulation (at die level)
and 3D thermal simulation (at package level)
inputs outputs
• Use of previous data
• 3D structure (with package)
• Boundary Conditions
• Heat source :
active surface of the device
Power vs time (from 2D device simulation)
• Natural convective transfer coefficient
• Fixed Temperature or heat transfer coefficient
• Meshing criteria
• Topology
• Temperature distribution
(iterative remeshing)
2D/3D electro-thermal approach (1/3)- weak coupling
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2D/3D electro-thermal approach (2/3)- weak coupling
• Assembly DOE
• Parameters
• Number of wires (3, 4, 6)
• Number of stitch (1, 2, 3)
• Die size (A, B, C, D)
• IFSM performances
• Thermal simulations
(with same methodology)
Tcrit=950K
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2D/3D electro-thermal approach (3/3)- weak coupling
• Advantages
• Fine mesh in 2D for electro-thermal
simulation
• 3D structure for a good description
of the heat dissipation
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• Drawbacks
• Weak coupling
• Many operations to do
• Many verification
• Uniform distribution of the power
not realistic
Limitations of this approachIMAPS - Thermal Management Workshop – February 2017
P+
N
P+
N0%
of current
100%
of current100%
of current
0%
of current
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2D/3D electro-thermal approach (1/1)- strong coupling
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Limitations of this approach due to thermal resistances
• Advantages
• Strong coupling
• Fine mesh in 2D for data transfer
electro-thermal simulation
• 3D structure for a good description
of the heat dissipation
• Drawbacks
• Data transfer by contacts
• Presence of thermal resistances
• Number
• Position
• Value
• Use of multi-device feature of SDEVICE multi-scale
• 1 device for die-scale : 2D electro-thermal model
• 1 device for package-level : 3D pure thermal model
IMAPS - Thermal Management Workshop – February 2017
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nodal approach (1/1) 19
In progress
• Advantages
• Calculation time
• Linked with Cadence
• Drawbacks
• Knowledge of electro-thermal model
• Discretization of the structure with boxes for thermal circuit and electro-thermal circuit
• RC element for thermal circuit
• R + Diode for electro-thermal circuit
• Coupling of electro-thermal circuit and thermal circuit
JC KRENCKER, Institut d'Électronique
du Solide et des Systèmes (ICUBE)
Therminic 2012
A Todri-Sanial, LIRMM/University of
Montpellier
EuroSimE 2013
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Conclusion & Outlooks
Introduction
Approaches
Conclusion & Outlooks
IMAPS - Thermal Management Workshop – February 2017
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Conclusion / Outlooks
• Reminder of the aim :
• To determine a methodology allowing to simulate surge
because of multi-scale simulation need
• Transient electro-thermal simulation approaches
• Advantages and drawbacks for every approaches
• According to device and surge choice of an approach
• Some approaches seem very interesting but lack of maturity or
knowledge
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