NOVEL SOFT ERASE AND RE-FILL METHODS FOR A P{sup}+-POLY GATE NITRIDE-TRAPPING NON-VOLATILE MEMORY DEVICE WITH EXCELLENT ENDURANCE AND RETENTION PROPERTIES

摘要

Novel soft erase and re-fill methods are proposed for P{sup}+-poly gate nitride trapping non-volatile memory device. The soft erase is a short negative FN (Fowler-Nordheim) channel erase that can be performed after the hot-hole sector erase. By using a P{sup}+-poly gate the gate injection is reduced and this soft erase produces excellent self-converging property with desirable low V{sub}T, and it recovers both the hard-to-erase and over-erase cells. Since the hard-to-erase problem is solved by this soft erase, it can be combined with low-power programming methods such as CHISEL; more than 2 MB/s programming throughput is achieved, suitable for data Flash applications. Soft erase also possesses a strong electrical annealing effect to recover the hot-hole induced damages. Moreover, a shorter version of this soft erase method can be applied to the programmed state to eradicate shallow-level electrons and replace them with deep-level electrons (Re-fill). Repeated "re-filling" of electrons results in a shifting of the trapped electron energy distribution to a "bluer" spectrum. Greatly improved endurance and retention properties are demonstrated by these new methods.