Leakage mechanism of local junctions forming the main or tail mode of retention characteristics for dynamic random access memories

We have reported the test structure for measuring the leakage characteristics of the local junctions. In this paper, we analyze the measurement results of the leakage characteristics of local pn junctions. We determined that the trap-assisted tunneling mechanism controls the leakage current of the main mode cells. It is observed that the increment of the leakage current at the leaky junctions in the tail mode is smaller than that at the normal junctions in the main mode when the supply voltage is increased. We propose a two-traps related leakage mechanism for the leakage current of the pn junctions in the tail mode. The two-traps pair increases the leakage current and forms the tail mode in the distribution of retention time of the dynamic random access memories.