Origin of wide retention distribution in 1T Floating Body RAM

Abstract

The variability of 1T FBRAM performances is investigated. The VG read window and the state "1" distribution are correlated with the number of holes injected during the write "1" related to the electric field in the S/D junctions. Besides, the origin of wide retention time distribution has been correlated with the distribution of G-R center in the Si band gap. Single defect with the Si midgap energy level can generate a leakage path affecting strongly the cell retention time. This can explain also wide retention distribution. Thight control of such defects poses extreme challange for the manufacturing of FBRAM.