Quantitative identification for the physical origin of variable retention time: A vacancy-oxygen complex defect model

We quantitatively examined current high-density DRAMs to identify the physical origin of the so-called variable retention time phenomenon, which is characterized by bistability of the data retention time of a DRAM bit. Experimental and theoretical analyses led us to supporting a vacancy-oxygen complex defect model. On the basis of the model, we achieved significant improvements in the VRT bit rate by introducing three control methods, defect reduction, defect deactivation, and stress reduction processes.