Engineering & Computer Science 1 RADSAFE - An Integrated Radiation Effects Simulation Framework Robert A. Weller, Robert A. Reed & Marcus H. Mendenhall Vanderbilt University 9-10 May 2005

Engineering & Computer Science 2 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.

Engineering & Computer Science 3 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.

Engineering & Computer Science 4 The RADSAFE System

Engineering & Computer Science 5 Implementation? How it works… ISE TCAD (DESSIS) Geometry VUmps (G EANT 4) Mathematica & Python C++ Tools, Scripting Automatic Meshing Events Gaussian charge generation

Engineering & Computer Science 6 The single event - a collection of segments Particle Trajectories Incident proton: blue Electrons: red Energy in the transistor: 44.7 keV

Engineering & Computer Science 7 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:

Engineering & Computer Science 8 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

Engineering & Computer Science 9 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

Engineering & Computer Science 10 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

Engineering & Computer Science 11 Displacement Damage in GaAs

Engineering & Computer Science 12 A Displacement Single Event How does energy translate to electrical activity?

Engineering & Computer Science 13 Single Event Simulation System: Si diode, a 5 µm cube. Events: 1 GeV/nucleon 12 C total incident. Pre-selection: >1.5 MeV in a 1 µm cube, 0.5 µm below the junction. 267 candidate events.

Engineering & Computer Science 14 The radiation event - Trajectories Event 037 Event 267 Event MeV 14.1 MeV 10.6 MeV

Engineering & Computer Science 15 Ion Tracks for Event e - /cm e - /cm 3

Engineering & Computer Science 16 Ion Tracks for Event e - /cm e - /cm 3

Engineering & Computer Science 17 Ion Tracks for Event e - /cm e - /cm 3

Engineering & Computer Science 18 Radiation event: Meshing Event 267 Slice at y = 1.0 µmSlice at x = 0 µm

Engineering & Computer Science 19 Validation: Charge Conservation

Engineering & Computer Science 20 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)

Engineering & Computer Science 21 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