Effect of Work-function Variation on Transfer Characteristics and Memory Performances for Gate-all-around JLFET based Capacitorless DRAM

Abstract

In this study, we present variations in transfer characteristics and memory performances caused by work-function variation (WFV) in the metal gate of a one-transistor dynamic random-access memory cell based on a gate-all-around junctionless field-effect transistor (GAA-JLFET). To investigate the influence of WFV, we simulated 200 samples of GAA-JLFETs. The samples had different transfer characteristics depending on the metal grain granularity. In addition, we calculated and analyzed the mean and standard deviations for the transfer characteristics. Further, the memory performances were analyzed using two extreme cases with the highest and lowest threshold voltage (V<SUB>th</SUB>) as examples. When WFV was not considered, the current ratio was 108, and retention time was more than 10 ms. Meanwhile, when WFV was considered, the current ratio was 10² and 10⁴, and the retention time was reduced to 0.051 ms and 2.2 ms, respectively. These results showed that WFV affected not only the transfer characteristics in GAA-JLFET but also the memory performances; it could adversely affect the reliability of the memory device.