Hybrid TiN nanocrystals/Si 3 N 4 nonvolatile memory featuring low voltage operation by spinodal phase segregation

Hybrid nonvolatile memory with Si nanocrystals embedded in the Si 3 N 4 has demonstrated higher operation speed than a plain silicon-oxide-nitride-oxide-silicon (SONOS) memory while maintaining better retention characteristic than a pure Si nanocrystal memory [1]. Based on this concept, TiN nanocrystals embedded in the Al 2 O 3 have exhibited improved memory characteristics [2]. Because Si 3 N 4 has been verified to possess more trapping sites than Al 2 O 3 , TiN nanocrystals three-dimensionally embedded in the Si 3 N 4 film was studied in this work as the charge trapping layer. In fact, three-dimensionally incorporating metal nanocrystals in the Si 3 N 4 (double heterogeneous stack) has been previously investigated and presented better memory performance than that with single heterogeneous stack [3]. However, the formation of this double heterogeneous floating-gate requires sequential deposition of Si 3 N 4 and metal nanocrystals which is relatively complicated and necessitates rigorous process parameter control. To address this issue, a single co-sputtering process was explored to achieve the hybrid memory structure by spinodal phase segregation.