The objective of evaluation the ACTEL FPGA's (manufactured by Matsushita) was to determine their present capability and furture potential for space applications. The ACTEL technology and FPGA architecture are among many available to the aerospace community. However, the ACTEL products were chosen as having more radiation tolerance in earlier investigations. Therefore a more thorough review and evaluation was warranted and now successfully completed by the aerospace community.
Two important requirements for space application are product reliability and quality. To evaluate these, there was examination of the manufacturing process suing destructive physical analysis methods. In addition product life tests were conducted. The life tests and DPA evaluation were directed toward giving insight into whether the technology and product could meet the stringent standards necessary for space applications. All space projects and designs will have different part standards and requirements. But some minimum level of reliability must be assured to be deemed acceptable by the aerospace community. The one concern as a result of the DPA is the poor quality of metal step coverage. The A1020/A1020 (2 µm) is acceptable provided a 20% minimum step coverage in contacts and vias is met by the manufacturer and the application temperature is limited to 90°C. The A1280 (1.2 µm) and the A1020A (1.2 µm) are not recommended at tis time because mission lifetime is jeopardized due to possible electromigration. Product life testing also showed evidence that some parameters may change. To insure against these changes a delta criteria is recommended as part of the screening flow or life tests.
The radiation data collectively for the A1020/A1020 show the product to have an acceptable TID tolerance for some space applications. The total dose achieved without any hard failures is at or slightly above 100 krads (Si). SEU LET thresholds appear to be in the 15 to 25 MeV(mg/cm2) range. There was no latchup observed for LET less than or equal to 120 MeV/(mg/cm2).
The A1280 is more vulnerable to SEU, because by design it is comprised of C-modules and S-modules. The S-module LET threshold is less than 5 MeV/(mg/cm2). The total dose fot eh A1280 is at 5 krads (Si), significantly less than that for the A1020/A1020. Further study of the A1280 is needed to understand its limited performance.
In summary we hope this report provides useful information to all space application users. It was through the cooperation of all who participated and those who contributed information that a much better understanding of the FPGA's performance as a radiation hard and reliable device has been achieved.
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Last Revised: January 09, 2002
Digital Engineering Institute
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