GEant4 Microdosimetry Analysis Tool - GEMAT Fan Lei, Peter Truscott & Petteri Nieminen SPENVIS/Geant4 Workshop, Leuven, Belgium 05 October 2005

2 Contents 1Background 2GEMAT overview –Geometry Builder –Physics list –Analysis manager 3Application example 4Further developments 5Summary

3 Background Single event effects are data corruptions or failures induced in microelectronics by single particles These are a major factor limiting the reliability of future microelectronics. Susceptibilities to SEEs and the range of effects are on the increase Currently, best way to quantify device susceptibility to energetic particles is to use accelerator facilities - expensive, may not relate to operational conditions, and does not tell us about the physics processes

4 SEE Modelling Objectives Develop modelling capability to simulate high-energy interaction processes, charge production, and semiconductor device response In doing so: –Reduce the reliance on repeated recourse to experiments to determine device susceptibility –Enable better understanding of dominant physical processes driving observed effects Provide an engineering tool to assist in cost-effective selection of current/future components for aerospace and general safety-critical projects At QinetiQ SEE modelling activities are supported by the MoD/CRP and by ESA through the REAT, REAT-MS contracts.

5 Simulation of the Single Event Effect Processes Need develop models for the complete process, these include 1. nuclear interaction 2. charge generation 3. charge collection This talk is addressing process 1 only

6 GEant4 Microdosimetry Analysis Tool - GEMAT A Geant4 based application for microdosimetry analysis of microelectronics Easy to use geometry builder –Handle more complex volumes than regular parallelepiped Dedicated physics list –Making use of the full G4 physics capability Build-in analysis modes –PHS: SEU rates calculated based on experimental ion data –Path-length: used with environment h-ion LET data –…

7 GEMAT Overview It is a standard Geant4 application: –Geometry construction –Primary particle generation –Physics list –Histogram/Analysis manager

8 Geometry Constructor Options C++ coding Geometry/structure file from SILVACO device physics code Using the build-in geometry commands: –Material definition –Geometry definition –Visualization attributes

9 Material Definition Commands /geometry/material/add »/delete »/list List of commands: Predefined material: There are 4 predefined materials New material can be added by given its name, element composition and density e.g. /geometry/material/add SiOxide Si-O2 2.7

10 Geometry Construction Commands A layered geometry structure –Arbitrary number of layers of different materials One layer is designated as the Contact Layer –Contact Volumes (CVs) can be added One layer is designated as the Depleted Layer –Sensitive Volumes (SVs) can be added

11 CV/DV Shapes Basic shapes –Cylinder: 2 parameters –Box: 2 parameters –L-shape: 4 parameters –U-shape: 4 parameters All can be tapered at top/bottom Position (x,y) in the layer Material & Vis. Attr.

12 Physics List G4LowEnergyEM G4HPNeutron G4Binary/G4Bertini G4BinaryLightIon G4Abrasion/G4Ablation G4RadioactiveDecay Layer dependent cut-offs Max step-size, max frac. Of energy loss Bias the C-S of a process Primary Particle Generator G4GeneralParticleSource (GPS)

13 Analysis Manager Fluence, Pulse Height Spectrum (PHS) and Path-length Applied to selected sensitive volumes (SVs) Build-in histogram capability –Wide choice of binning scheme, inc. arbitrary –Output in CSV format Coincidence analysis: –Between up to 3 DVs –Each volume can have its own threshold

14 An application Example: 4 Mbit SRAMs A large amount of beam test data available, from heavy Ion to thermal neutrons Good knowledge of the device geometry Two types of simulations using –Detailed geometry at cell level –An array of simple cells

15 GEMAT geometry for four-transistor cell, forming part of a 4Mbit SRAM Pink-outlined regions indicate sensitive volumes

16 Proton SEU predictions for Samsung KM684002A 4Mbit SRAM The energy-deposition spectrum from events in SVs integrated over a Weibull fit to LET data from heavy-ion tests

17 Neutron Data SVs modelled as an array of simple 0.5x0.5  m 2 cells

18 MBU rates Proton Neutron

19 Further Developments Within the REAT-MS project –Porting to the GRAS simulation framework –Geometry: GDML CVs/DVs in any layer –Physics: improved biasing –Analysis: AIDA SEU rate calculations –Integration into SPENVIS In the longer term: –Ion track models –Charge generation process Phonons and plasmason –Low energy Ion nuclear interaction (< 100 MeV/nucl.) –More SEU algorithms and models –…–…

20 Summary Modelling is required to reduce the reliance of SEE study on beam experiments and for understanding of the underlying physics processes Much of the physics to perform detailed single-event simulations are in place in Geant4. GEMAT provided the accessibility to this powerful toolkit It also provide easy to use methods for definition of 3D microdosimetry geometry representing semiconductor, and incident particles (spectrum, angular distribution) GEMAT has already been successfully used in a wide range of SEE analysis New developments planned in the REAT-MS project will further improve its capability and usability, making it available in the SPENVIS system