Effects of TID on SRAM Data Retention Stability at the 5-nm Node

The total-ionizing dose (TID) response of a 5-nm bulk FinFET technology is evaluated through static random access memory (SRAM) arrays. Single-port (SP) and two-port (TP) SRAM arrays are exposed to 10-keV X-ray TID in grounded and biased conditions. The effects of TID are measured as changes in the data retention voltage (
$V_{\mathrm {DR}}$
), or the lowest voltage at which an SRAM cell is able to retain written data. Results show that TID exposures lead to increases in average
$V_{\mathrm {DR}}$
for cells/arrays. Although the average
$V_{\mathrm {DR}}$
value increases after irradiation, individual cells experience varying levels of changes in
$V_{\mathrm {DR}}$
. Degradation in average
$V_{\mathrm {DR}}$
values is lower for parts that were grounded during irradiation compared to those that were operated at a nominal operating voltage. TP SRAM cells show greater degradation than SP cells for the same bias and input conditions during irradiation due to a higher number of transistors connected to the storage nodes. Single-event upset (SEU) rates do not change significantly across TID exposure.