Partial Crystallization of \hbox for Two-Bit/Four-Level SONOS-Type Flash Memory

The nonvolatile memory properties of the partially crystallized HfO 2 charge storage layer are investigated using short-channel devices of gate length L g down to 80 nm. Highly efficient two-bit and four-level device operation is demonstrated by channel hot electron injection programming and hot hole injection erasing for devices of L g > 170 nm, although the reduction of the memory window is observed for devices of L g < 170 nm. A memory window of 5.5 V, ten-year retention of V th clearance larger than 1.5 V between adjacent levels, endurance for 10 5 programming/erasing cycles, and immunity to programming disturbances are demonstrated. Flash memory with partially crystallized HfO 2 shows a larger memory window than HfO 2 nanodot memory, assisted by the enhanced electron capture efficiency of an amorphous HfO 2 matrix, which is lacking in other types of reported nanodot memory. The scalability, programming speed, V th control for two-bit and four-level operation, endurance, and retention are also improved, compared with NROM devices that use a Si 3 N 4 trapping layer.