Nonvolatile Memory Characteristics with Embedded Hemispherical Silicon Nanocrystals

Abstract

Silicon nanocrystal-embedded memories were fabricated by using the thermal agglomeration of an ultrathin (1.5–1.8 nm) amorphous silicon (a-Si) film. The a-Si was deposited on a 4-nm tunnel-oxide layer by electron beam evaporation and subsequently annealed in situ at 850 °C for 5 min. Hemispherical Si nanocrystals were self-assembled, and nonvolatile memories were fabricated after depositing a 17-nm control-oxide layer. A threshold voltage window of 0.9 V was achieved under write/erase (W/E) voltages of ±10 V, and good endurance characteristics up to 104 cycles were exhibited. Increasing W/E voltages created a large memory window (>2.7 V), and the retention characteristics showed little temperature dependence up to 85 °C.