Alec Stanculescu, Fintronic USA

1
Design Verification Method for Radiation Hardness
using Simulation Farms

• Alec Stanculescu, Fintronic USA
• Alex Zamfirescu, ASC
• MAPLD 2004
• September 8-10, 2004
• alec_at_fintronic.com alexz_at_ascinc.com

2
Summary
Fintronic USA

• Problem Addressed
• Solution Proposed
• Conclusion
• Proposed Plan

3
Introduction

• Circuits malfunction due to radiations
• Transient errors may lead to Soft errors if an
  erroneous data is latched
• Cumulative effects may lead to permanent ( hard)
  errors (total dose)

4
Problem Addressed

• Reduce the cost of assessing the behavior of very
  large circuits under different radiation
  conditions by providing fast feedback to circuit
  designers regarding
• statistics of faults
• reliability
• nature of degradation

5
Solution Proposed

• Simulate radiation effect by injecting faults in
  the simulation based on the radiation failure
  susceptibility of the library cells used
• Use efficiently a simulation farm
• Automate the analysis of results

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Radiation Hardness Analyzer
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Radiation Failure Susceptibility

• For each cell, for each wire, record
• lttime windowgt ltfault_info_tripletgt
• ltfault_info_tripletgt
• ltp of a given fault-type occurring in the given
  windowgt,
• lttype of faultgt,
• ltp of at most one fault of the given type
  occurring in the given windowgt
• where p stands for probability

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Creation of Radiation Failure Susceptibility Data

• Calibration of Simulation
• High correlation between simulation results and
  manufactured circuit
• Calibration Methods
• Test all cells at various radiation environments

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Calibration Methods

• Fabricate all supported cells on tested chip
  selection of tests may affect calibration
• Use existing circuits for testing
• Use an un-hardened version of the actual circuit
• Use transistor susceptibility based on specific
  measurements

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FinFarmVerilog Simulation Farm

• Enables one engineer to manage many simultaneous
  simulations
• Network of computers
• Farming methodology
• Farming tools
• Current farms use between 10 and more than 1000
  licenses

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Farming Methodology

• Un-partitioned circuits
• small footprint 64-bit simulation helps
• Split stimulus
• Simultaneous verification of alternative
  components
• Program feedback-based verification

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Farming Tools

• Perform automated
• simulation launching
• simulation queuing
• collection reporting of simulation results
• collection merging of code coverage results
• Perform real-time monitoring
• Perform programmed re-launching of simulations

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FinFarm Usage

• Regression Testing
• Extensive Exploration of Design Space
• Evaluation of Reusable IPs
• Analysis of Design Trade-Offs Power, Size,
  Speed and search for optimal solution using
  feedback loop
• Radiation Hardening

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Rad. Hard. Simulation

• Describing effects on circuit by a given
  radiation environment, using VCD-F format (VCD
  fault format)
• VCD-F Reader injects corresponding faults in
  simulation
• Launching simultaneous simulations using
  simulation farm
• Collecting and processing results

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VCD-F Format

• VCD IEEE std 1364 results
• VCD-F specifies random faults, i.e. values are
  replaced by
• Fault types
• Randomization info

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VCD-F Reader

• VCD-F Reader injects faults in simulation.
• Nature of faults permanent, transient
• Kind of faults stuck at, bridging, cross talk,
  gate rupture, value toggle, timing, etc.

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Simulation Launching

• Save simulations at various check points, just
  before inserting faults
• Re-start simulation at latest checkpoint before
  the injected fault which caused errors
• Launch simultaneous simulations on FinFarm

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Collecting and Processing Results

• Record results databases
• Compare Results Databases
• Isolate circuits containing at least one error,
  for detailed analysis
• List of possible fault type
• Produce reports

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Summary of Solution

• Cells are measured once and results are stored in
  IEEE standard
• Use Monte Carlo technique to establish radiation
  susceptibility of complex ICs using simulation
• Fast feedback to designers
• Major cost reduction

20
Proposed Plan

• Establish a radiation assessment lab
• Create oversight task force
• Government
• Industry
• Academia
• Create standards for describing
• Radiation failure susceptibility of cells
• Distribution of faults in circuits in time