Hot-carrier memory effect in an Al/SiN/SiO₂/Si MNOS diode due to electrical stress

An Al/SiN(70 Å)/SiO2(126 Å)/(p)Si MNOS diode was fabricated by using the LOCOS process. The interface trap densities at SiN-SiO2and at the SiO2-Si interface were measured by a CV method. Successive stresses of biasing at -20 V introduces both trap densities. Memory effect of the flat-band shifts was observed. The electron traps were first produced at the SiN-SiO2interface. In addition, the hole traps were also produced owing to the two-step barrier formation in the insulators. Fowler-Nordheim tunneling may be responsible for the trapping in the oxide. The hole traps can be annealed while the electron traps cannot be.