부산대학교 도서관

Cell transistor and data retention time characteristics were studied in a 90-nm design-rule 512Mbit DRAM for the rst time. Also, the characteristics of the cell transistor were investigated for dierent shallow trench isolation (STI) gap-ll materials. A high-density plasma (HDP) oxide with a high compressive stress increased the threshold voltage of the cell transistor whereas the polysilazane spin-on-glass (P-SOG) oxide with a small stress decreased the threshold voltage of the cell transistor. The stress between the silicon and the gap-ll oxide material was found to be the major cause of the shift of the cell transistor threshold voltage. When a high stress material was used for STI gap ll, the channel-doping concentration could be reduced, so the cell junction leakage current was decreased and the data retention time was increased.?