The Effect of the Gate Material in MIS Structures on the High-Field Charge Degradation in the Gate Dielectric

Comparative studies are carried out to investigate high-field charge degradation effects in the gate dielectric of metal—insulator—semiconductor (MIS) structures with aluminum and polysilicon gates. Charging phenomena in MIS structures are explored using high-field electron injection into the dielectric under conditions of gradually increasing voltage current density, with periodic short-term switching to a measurement mode at a constant low injection current density. This approach makes it possible to obtain new insights into the charge degradation effects developing inside the gate dielectric of MIS structures made of different gate materials under high-field injection conditions. The results demonstrate that, in MIS structures having a phosphorus-doped polysilicon gate, the formation of a thin phosphorus—silicate glass layer significantly suppresses the rate of charge degradation processes. As a consequence, the average charge injected into the gate dielectric prior to breakdown during high-field voltage testing increases by more than an order of magnitude.