electrical overstress on large discrete components

Electrical OverStress on large

discrete components

Fabrice ROQUETA – TCAD team – ST Tours

IMAPS – Thermal Management Workshop

February 2017

Contents

1. Introduction

2. Approaches

1. “Global” approach

2. “Local” approach

3. Intermediate approaches

3. Conclusion & Outlooks

2

IMAPS - Thermal Management Workshop – February 2017

Introduction

Introduction

Approaches

Conclusion & Outlooks


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 ?


Aim of the studyWhy electro-thermal model is needed?

• Si/SiC properties depending on temperature

• Carrier mobility

• Intrinsic density

5

Breakdown voltage

Resistance Thermal behavior


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

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 ?

6


Approaches

Introduction

Approaches



o 0D electro-thermal simulation (‘‘global’’ approach)

o 3D electro-thermal simulation (‘‘local’’ approach)

o Intermediate approaches



• other possibilities ?

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

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


Current Density

Temperature Heat flux



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.


• Advantages

• No geometry limitation

Close to real device

11

• Drawbacks


• 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)


Approaches

Introduction

Approaches



o 0D electro-thermal simulation (‘‘global approach’’)

o 3D electro-thermal simulation (‘‘local approach’’)

o Intermediate approaches



• other possibilities ?

inputs outputs• Doping profile

• Boundary conditions• Electrical

• Thermal

• Meshing criteria• Doping profile• Previous Electrical and thermal simulation results (iterative remeshing)




• Advantages

• Easily meshed

• CPU time

accuracy

14

• Drawbacks

• Geometry limitations

• 3D device layout

• Taking into account wires / package

Not always possible


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

15



• 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

16



• Advantages

• Fine mesh in 2D for electro-thermal

simulation

• 3D structure for a good description

of the heat dissipation

17

• Drawbacks

• Weak coupling

• Many operations to do

• Many verification

• Uniform distribution of the power

not realistic


P+

N

P+

N0%

of current

100%

of current100%

of current

0%

of current

2D/3D electro-thermal approach (1/1)- strong coupling

18

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


nodal approach (1/1) 19

In progress

• Advantages


• 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



Introduction

Approaches



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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electrical overstress on large discrete components

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