Characteristics of CMOS/Bulk and SOS Memories in a Transient Environment

SOS and bulk silicon memories were exposed to 18 and 100 nanosecond pulses of 10 MeV electrons from a linac generator. Dose rates for upset, data scrambling, and latch-up were determined. The SOS devices did not scramble data when exposed to dose rates greater than 2×1010 rads(Si)/sec for the 18 nanosecond pulse. The upset dose rate in SOS devices during the read operation is dependent on the time of occurrence of the radiation pulse relative to the switching waveform during the operation. It varied from a low of 6×109 rads(Si)/sec to a high of >2.7 × 1010 rads(Si)/sec. depending on conditions of operation. Bulk silicon memories of equal size and similar design to the SOS devices latch-up at dose rates of 108 rads (Si)/sec, a smaller bulk memory (the CD4061) was shown to be capable of exposure to dose rates of 1011 rads(Si)/ sec with a limited number of samples latching-up when operated a 5 volts. All of these smaller memory samples latched-up when the voltage was increased to 10 volts and the dose rate was in the range of 2 to 6×109 rads (Si)/sec.