TEM analysis of failed bits and improvement of data retention properties in megabit-DRAMS

Direct observation of failed bits in DRAMs indicates that the dislocation lines originating at the sidewall edge of the cell plate cause data retention errors. The elongated dislocation lines were observed during the annealing treatment after As-implantation. It was found that the failure due to n/sup +/-substrate leakage in the cell increased in proportion to the dislocation density. The failure due to the leakage was greatly decreased by eliminating As-implantation in the regions between the cell plate and the transfer gate. The yields were also improved.<>