0000000000819075
AUTHOR
T. Rossetti
Effects of nitridation by N2O or NO on the electrical properties of thin gate or tunnel oxides
We have studied the effects of nitridation on the leakage current of thin (7-8 nm) gate or tunnel oxides. A polarity dependence of the tunneling current has been found this behavior is related to the presence of a thin silicon oxynitride layer at the SiO2/Si-substrate interface. The oxynitride layer lowers the tunneling current when electrons are injected from the interface where the oxynitride is located (substrate injection). The current flowing across the oxide when electrons are injected from the opposite interface (gate injection) is not influenced by the oxynitride. The increase of nitrogen concentration leads to a decrease of the tunneling current for substrate electron injection.
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 N2 carrier gas have been used in the former case, SiH4 and H2 have been used in the latter. In both cases a nanocrystalline silicon layer is obtained, with nanocrystals a density higher than 1011 cm-2. The process with H2 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 me…