SEU characterization of hardened CMOS SRAMs using statistical analysis of feedback delay in memory cells

Write-time measurements confirm that the amount of feedback delay introduced by the polysilicon cell resistors in a SEU (single-even-upset) hardened CMOS SRAM (static random-access memory) is not identical for all cells in a memory chip. It is noted that the effect of the variance in the normal dist...

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Bibliographic Details
Published in:IEEE Transactions on Nuclear Science (Institute of Electrical and Electronics Engineers); (USA) 1989-12, Vol.36 (6), p.2318-2323
Main Authors: Kohler, R.A., Koga, R.
Format: Article
Language:English
Subjects:
360605 - Materials- Radiation Effects
440200 - Radiation Effects on Instrument Components, Instruments, or Electronic Systems
Delay effects
ELECTRICAL EQUIPMENT
ELEMENTS
Energy exchange
Gaussian distribution
HARDENING
INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
MATERIALS SCIENCE
MEMORY DEVICES
MOS TRANSISTORS
PHYSICAL RADIATION EFFECTS
QUALITY ASSURANCE
RADIATION EFFECTS
RADIATION HARDENING
Random access memory
RESISTORS
Semiconductor device measurement
SEMICONDUCTOR DEVICES
SEMIMETALS
SILICON
State feedback
Statistical analysis
Temperature distribution
Testing
TRANSISTORS
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Summary:Write-time measurements confirm that the amount of feedback delay introduced by the polysilicon cell resistors in a SEU (single-even-upset) hardened CMOS SRAM (static random-access memory) is not identical for all cells in a memory chip. It is noted that the effect of the variance in the normal distribution of feedback delay has become pronounced because of the large number of resistors in state-of-the-art memory chips. Consequently, statistical analysis of the distribution of feedback delay is useful for proper interpretation of SEU test data to quantify device response for confident hardness assurance. Statistical analysis of the feedback delay distribution in cell arrays using write-time analysis shows that a feedback delay of 6 ns at the temperature of interest is sufficient to harden the AT&T SRAM cell against all LETs (linear energy transfers). To assure the hardness in all cells, however, the mean value must be set higher than the minimum required resistor value. Statistical information about the feedback delay population can be used to calculate the acceptable resistance limits. Alternately, a novel part acceptance plan based on direct electrical measurement of the feedback delay distribution is proposed.< >
ISSN:0018-9499
1558-1578
DOI:10.1109/23.45442