Effect of DC/AC stress on the reliability of cell capacitor in DRAM

The influence of DC and AC stress on leakage current Ileak of cell capacitor was analyzed. Experimental results indicated that DC stress induced the asymmetric damage of cell capacitor and increase of Ileak due to the increase of trap assisted emission electron, AC stress induced the damage on both nodes of capacitor and increase of Ileak due to formation of tunneling path in dielectric when AC stress was applied. At stress voltage VD1 ≥ 2.1 V, lifetime under AC stress was much worse that under DC stress, but the guaranteed voltage under AC stress at 10 years was twice as large as that under DC stress due to the difference of acceleration constant factor between DC and AC. As these results, the increase of Ileak under DC stress should be considered more important than that of AC stress for reliability estimation of cell capacitor as operating voltage decreases.