Prompt and total dose response of hard 4K and 16K CMOS static random access memories (SRAMs)

Total dose (TD) and prompt dose (PD) rate effects were measured in three types of SRAMs: Harris 6504RH (CMOS/bulk) and RCA 11121 (CMOS/SOS) which are commercially available 4K memories, and developmental samples of a more recent hardened 16K CMOS/SOS SRAM (RCA TA 12702). TD exposure was performed with C0-60 at dose rates of 5-240 rad (Si)/s, while PD testing used facilities that can deliver a PD of 7 krad (Si) in a 22 ns pulse and 50 krad (Si) in a 45 ns pulse. The results indicate that the dynamic upset level for the TA 12702 is 1.1 x 10 to the 11th rad (Si) for either a read or write mode of operation at 5 V bias for a wide range of process variables. The static upset level for most of the samples was greater than 5 x 10 to the 11th rad (Si)/s. Increasing the voltage to 6 V would make the noncorruptible dose rate about 10 to the 12th rad (Si)/s. It is concluded that production-quality parts of all three device types can operate at high ionizing dose levels, i.e., greater than 100 krad (Si).