Nanocrystal MOS memories obtained by LPCVD deposition of Si nanograins

We have realized silicon quantum dots embedded in SiO2 which act as nano-floating gates of MOS memories. The dots with nanometer sizes have been deposited by LPCVD on a 3nm tunnel oxide. Two processes at a fixed pressure have been explored by varying the temperature. SiH4 with a N-2 carrier gas have been used in the former case, SiH4 and H-2 have been used in the latter, In both cases a nanocrystalline silicon layer is obtained, with nanocrystals a density higher than 10(11) cm(-2). The process with H-2 carrier gas is more controllable and leads to the formation of nanocrystals with a more regular shape. In both cases the density of grains is able to originate detectable threshold shifts in the memory cell, even though process SiH4 and H-2 shows better electrical performances.