Bit flipping effect on 6T, 7T and 10T static random access memory by TCAD simulation

Abstract

In space there are many high energetic particles and rays which potentially hazardous to microelectronic circuits and systems. The study of electrical characterization with radiation effect is important for any space exploration as high energetic particles and rays of space seriously limiting the reliability of electronic devices like memory cell. Bit flipping is one of the most common radiation effect found in space environment for memory cell like Static-RAMs (SRAMs). To protect SRAMs from bit flipping effect, it is important to know the sensitive striking position and intensity threshold point of SRAMs. Technology Computer Aided Design (TCAD) have always been viable alternatives for characterizing bit flipping as it is difficult, hazardous and costly to emulate high energy space particles in the lab. This research presents TCAD simulation for bit flipping effect on 6T, 7T and 10T SRAMs. A comparison study of intensity threshold point along with most sensitive striking area for SRAM cell are presented in this research. The intensity threshold study with Silicon over Insulator (SOI) technology is also presented for 10T SRAM. In this study, simulation of bit flipping were done using pulsed optical beam by MixedMode feature of ATLAS from Silvaco Inc. MixedMode is a mixed circuit and device simulator which can handle both circuit and device simultaneously. In the MixedMode study, SRAM cells were simulated by using SPICE coding where targeted transistor is a physically based device. The results show that, midpoint of drain is the most sensitive node for any radiation strike. It is also found that, for these particular structures, intensity threshold is increasing with the increase of transistor number in the SRAM and with the SOI technology intensity threshold increased significantly.