Leakage current observation on irregular local PN junctions forming the tail distribution of DRAM retention characteristics, with new test structure

The new test structure is proposed to observe the small leakage current for a large number of local PN junctions. This new structure makes it possible to catch the leaky cells corresponding to the tail distribution of the DRAM retention characteristics. It is found that the field enhanced thermionic emission is the leakage mechanism for both the leaky and conventional junctions. The leaky junctions are characterized by the small active energy of the traps in the depletion layer. Moreover, we observe the leakage characteristics corresponding to the DRAM bit with variable retention time. The kink phenomena can be observed in the leakage current while sweeping the voltage with trapping or detrapping the electrons from the traps.