Alpha-particle-induced SER of embedded SRAMs affected by variations in process parameters and by the use of process options

We investigate the alpha-particle-induced soft-error rate (SER) of embedded SRAMs with a focus on the spread in SER owing to variations in the process parameters. The alpha-particle-induced SER of SRAM-instances processed in 0.18 and 0.13 mu m technologies was determined experimentally using accelerated testing. The SER in both the 0.18 and the 0.13 mu m processes show design-to-design and batch-to-batch variations. In addition, the 0.13 mu m SRAMs show a variation in SER between individual samples from the same batch. Also, circuit simulations were performed to Study the statistical variations in the critical charge of the SRAM cell. Our calculations show that the total spread in SER equals a factor of 3.0 and 4.3 for 0.18 and 0.13 mu m SRAMs, respectively. These results are in agreement with the experimental data. We show that the use of the high-V-T process option can reduce SER, because of a decrease in the collection of induced charges. Our results illustrate the importance of accurate simulation methods and stress the need to test several samples, batches, and designs in order to characterize the SER of a specific type of SRAM. (c) 2005 Elsevier Ltd. All rights reserved.