[email protected] engineering & computer science 1 radsafe - an...

[email protected] Electrical Engineering & Computer Science1

RADSAFE - An Integrated Radiation Effects

Simulation Framework Robert A. Weller, Robert A. Reed

& Marcus H. MendenhallVanderbilt University

9-10 May 2005


RADSAFE - The Objective

To create a system for first-principles predication of device, circuit and system response to

radiation.

RADSAFE is a strategy for implementation of the “third paradigm” of scientific discovery

in the field of the interaction of semiconductor electronics with physical

systems, in general, and with radiation, in particular.


The RADSAFE System

A revolutionary, modular computational system for predicting the radiation response of electronic devices, circuits, and systems from basic device structure, circuit topology, and fundamental radiation characteristics. Its goals – to be informed by the best available physics, implemented by robust algorithms, enabled by supercomputer technology, and calibrated by data.


The RADSAFE System


Implementation? How it works…

ISE TCAD (DESSIS)

Geometry

VUmps (GEANT4)

Mathematica& Python

C++ Tools,Scripting

AutomaticMeshing

QuickTime™ and aMPEG-4 Video decompressor

are needed to see this picture.

Events

Gaussian charge generation


The single event - a collection of segments

Particle TrajectoriesIncident proton: blue

Electrons: red Energy in the transistor: 44.7 keV


The single event - trajectory segment math

• The radiation event is a collection of trajectory segments

• Each segment has an associated energy• Each segment is convolved with a

Gaussian yielding:

f (

rx, t) =

Q(2π )3/2vσ 2τ

e

rr⋅

rv( )2 −v2r2

2v2σ 2 erf(v2 −2

rr ⋅

rv

2 2 vσ) + erf(

v2 + 2rr ⋅

rv

2 2 vσ)

⎡

⎣⎢

⎤

⎦⎥

e−

t−t0( )2

2τ2

1+erf (t0

τ 2)

rx0 ≡

12(rx1 +

rx2 )

rv≡

rx2 −

rx1

rr ≡

rx−

rx0 v=

rv etc.


TCAD geometry parsing

• The key simulation step: Importing a TCAD structure

• The strategy: Reduce the structure to tetrahedra

• A constructive solid tetrahedron has been created for Geant4


TCAD Geometry Interface - Complex layers

Device Description

Radiation Events

• High energy protons incident on advanced CMOS integrated circuit

• Interaction with metallization layers dramatically increases energy deposition


Displacement Damage (Screened scattering)

• Screened Rutherford scattering is not part of Geant4• However - It is vital for displacement damage• MRED includes screened scattering using algorithms

that have been tested for more than a decade• Results accomplish the intent of NIEL but with

enhanced microscopic detail• Results point to an important research area for the

future


Displacement Damage in GaAs


A Displacement Single Event

How does energy translate to electrical activity?


Single Event Simulation

• System: Si diode, a 5 µm cube.

• Events: 1 GeV/nucleon 12C. 106 total incident.

• Pre-selection: >1.5 MeV in a 1 µm cube, 0.5 µm below the junction. 267 candidate events.


The radiation event - Trajectories

Event037

Event267

Event256

3.8 MeV 14.1 MeV10.6 MeV


Ion Tracks for Event 037

1018 e-/cm3 1014 e-/cm3



1018 e-/cm3 1014 e-/cm3


Radiation event: Meshing

Event267

Slice at y = 1.0 µm Slice at x = 0 µm


Validation: Charge Conservation


RADSAFE - Future Developments (12-24 mos.)

• Unified xml-based command and geometric description language using W3C xercesc parser

• Additional Python integration (Replacing Geant4-style message passing in VU code)

• Output Mathematica®/xml selectable• Improved sensitive volume definition -

coincidences• Time-stamped segments in TCAD• FLOODS integration-With U. Florida (USAF

MURI)


Outstanding Scientific Issues and Questions

• Experimental and computational tests of heavy-ion nuclear reactions. All ions. E < 1 TeV/nucleon

• Theory-based heavy ion stopping (Sigmund theory?) including spatial and energy distribution of electron-hole pairs

• Energy deposition in sub 100 nm structures• Energy deposition and persistent defects• Structure of electrically active defects• Fundamental device modeling in the quantum

regime• Spatially-dependent tensor mobility - Next talk!• “Deep Impact” - Core vacancy effects

[email protected] engineering & computer science 1 radsafe - an...

Documents