Hardness Assurance Considerations for the Neutron Environment

Two related questions pertaining to neutron hardness assurance technology are examined. (1) How much statistical variability in neutron response is present when the same product is manufactured by two different companies on controlled lines. (2) How does circuit design margin affect neutron failure probability. A large body of statistical data on semiconductor device neutron degradation has been accumulated at Rockwell International covering procurement from several manufacturers over approximately five years. The data has shown that the neutron radiation response usually differs by less than a factor of two when comparing the same device from two manufacturers; furthermore, the neutron radiation response of a specific device usually varies by less than a factor of two from the line average when compared over a period of several years. At a selected failure probability, the failure fluence divided by the circuit design safety margin is approximately constant over a wide range of selected failure probabilities and design safety margins. (auth)