Electrical Characteristics for Flash Memory With Germanium Nitride as the Charge-Trapping Layer

Due to a larger band offset and a higher permittivity compared to Si $_{3}$N$_{4}$, Ge $_{3}$N$_4$ formed by NH $_{3}$ plasma nitridation of an amorphous Ge film was explored in this study as the charge-trapping layer for flash memory devices. As the nitridation time prolongs, memory window and operation speed are improved accordingly. The improvement is inferred to be the increased number of trapping sites and higher permittivity of the charge-trapping layer caused by the introduction of nitrogen atoms. The former is helpful in storing more charges while the latter offers a higher electric field over the tunnel oxide. Memory devices with 180-s NH$_{3}$ plasma nitridation hold great potential for advanced memory applications because they possess many promising characteristics such as a large hysteresis memory window, high operation speed, robust endurance performance up to 10$^{5}$ program/erase (P/E) cycles, and good retention characteristic with 15% charge loss after 10-year operation at 85 °C.