Actel FPGA (Field Programmable Gate Array) Presentation to NASA and Industry September 22, 2004

1
Actel FPGA (Field Programmable Gate Array)
Presentation to NASA and IndustrySeptember 22,
2004

• Aerospace Actel Team
• Team Lead Larry Harzstark

2
Problem Statement

• Several contractors experienced device failures
  (approximately 36) after successfully programming
  the FPGAs
• All failures occurred within first 100 hours of
  operation
• All contractors were operating parts outside of
  Actel specification
• Multiple post-programming failures raised
  potential latent failure and reliability concerns
• Aerospace issued first Aerospace Alert/Advisory
  in December 2003
• Aerospace hosted three industry meetings - Oct
  2003, Feb 2004, Jun 2004
• Industry investigation team formed (headed by
  Aerospace) to determine root cause, potential
  hardware exoneration screens, long term
  reliability.

3
Boeing MEC FPGA Test Plan Old-Algorithm
4B125 MHz, 17 I/Os switching, 12.5 I/O toggle
rate -1V undershoot 4B250 MHz, 70 I/Os
switching 50 toggle rate -2V undershoot
Project 4B1

Project 7
550 parts
600 hrs
Project 4B2

2000 hrs

• Project 7 31 failures observed thru 600 hours
• Project 4B1 3 failures observed thru 1000 hours
• Project 4B2 2 failures observed thru 1000 hours
• Projects 4B1 and 4B2 resumed testing 9/20-21

4
Boeing Project 4 Test Results

• Failures consistent with continuation of Project
  7 Weibull curve
• -No evidence that stress (SSU) caused any
  additional failures

Test Point Units Tested 4B1 4B2 Identified Failures 4B1 4B2
0 hours 232 232 0 0
24 hours 232 232 2 0
168 hours 230 232 0 1
336 hours 230 231 0 1
500 hours 230 230 1 0
1000 hours 229 230 0 0
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Analysis of Boeing Project 7 Results

• 31 failures observed thru 600 hours of test
• Weibull FIT Rate developed based on Boeing test
  results for old algorithm with 90 confidence
  limits

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Failure Predictions Based on Boeing Test Results
Hours Parts Screened 1 Year Mission 3 Year Mission 10 Year Mission
100 4.9 6.6 8.8
500 3.6 5.3 7.5
7
Tiger-Team MEC Parts Testing
4B250 MHz
4B2 old algo 25 deg C
70 I/Os
switching,
50 I/O
4B2 old algo 85 deg C/ Vcca3
559 parts
toggle rate
-2 V undershoot
4B2 new algo 25 deg C
Electrical test points at 0, 24, 48, 168, 500,
1000 hours
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Tiger Team MEC Parts Testing

• Current Status as of Sept 17, 2004
• Old Algorithm
• Completed 168 hours 9/17
• 500 hours to be complete 10/4
• 1000 hours to be complete 10/31
• Group A at 25 deg C had 4 failures observed thru
  168 hours
• Group B at 85 deg C and Vcca3.0 V had 11
  failures observed thru 168 hours
• New Algorithm
• Completed 168 hours 9/14
• 500 hours to be complete 9/30
• 1000 hours to be complete 10/25
• Group A at 25 deg C had 11 failures observed thru
  168 hours
• 5 F X antifuses
• 5 I, K S antifuses
• 1 unknown-type antifuse

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Tiger Team MEC Test Results
Algo Type No Parts Programmed No Parts Into ATE Test 0 hour 0 1 hour 1 25 hours 25 - 49 hours 49 168 hours 168 500 hours 500 1000 hours
Old Algo Group A 25oC 88 83 2/83 1/81 0/80 0/80 1/80 TBD TBD
Old Algo Group B 85oC 87 83 2/83 4/81 4/77 1/73 0/72 TBD TBD
New Algo 25oC 384 336 4/330 4/326 2/322 1/320 0/319 TBD TBD
2 units kept as controls
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Tiger Team MEC Test Results

• Unexpected failures (5) of new algorithm high
  current (F X) antifuses
• 2 DPAs completed at Aerospace on F X antifuses
• One device has evidence of residual photoresist
• Potentially affects all other parts in Tiger-Team
  tests
• Parts tested directly into P4B2 environment at 25
  deg C show behavior comparable to Boeing P7 tests
• No acceleration apparent
• Parts tested in 85 deg C, 3 V stress environment
  does appear to show an increase in the number of
  failures
• Need additional analysis and investigation

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Additional Testing Planned

• Government working with Actel for formal space
  qualification of UMC 0.25 um technology
• Includes evaluation of physics of failure,
  development of activation energy and acceleration
  factors
• Aerospace to begin long-term (2-3 year) life test
  on UMC parts shortly
• 120 plastic A54SX32A parts
• Design configured to detect functional and
  timing-shift failures
• All programming pulses and waveforms will be
  recorded for each part and analyzed
• Interim data and results will be published and
  provided to industry

12
Conclusions

• There is significant risk of future failure with
  the MEC old-algorithm parts
• Screening does not appear to be feasible
• Tiger-Team tests have not shown sufficient
  reduction in failure risk to recommend use of MEC
  new-algorithm parts
• Wafer processing defects maybe contributing to
  failures observed
• UMC-parts testing by NASA to begin shortly
• All Actel results to date are promising
• ASIC alternative is appropriate if program
  schedules permit