High trap density and long retention time from self-assembled amorphous Si nanocluster floating gate nonvolatile memory

Abstract

The memory performance of floating gate nonvolatile memory based on amorphous Si (a-Si) nanoclusters self-assembled during low-temperature oxidation is investigated. A 2nm thick a-Si layer was grown on a top of a 5.6nm thick thermal oxide tunneling layer by ultrahigh vacuum ion beam sputter deposition and subsequently oxidized by annealing in flowing N2∕O2 (9:1) environment for 0–540s at 900°C. After oxidation, a 14nm thick Al2O3 control oxide layer was grown by atomic layer deposition. The authors find that the a-Si layer breaks up upon oxidation, self-assembling into a dense array of 1000s at at 150°C.