New interconnect plasma induced damage analyzed by flash memory cell array

We report new degradation phenomena induced by interconnect plasma processes observed in flash memory cell array. We found two different kinds of charge transport mechanisms for the ultra low leakage current induced by the plasma damage. One is field emission (1E-17 A/cell at 25C) and the other is thermal emission (1E-20 A/cell at 300C). The dominant key process steps to induce the damage have been demonstrated as VIA hole-RIE and resist ashing processes, respectively. These new degradation phenomena are caused by different mechanisms. The methods to reduce the leakage current are proposed. They require both structural and process improvement.