RTP Annealings for High-Quality LPCVD Interpolysilicon Dielectric Layers

Deposited instead of thermally grown oxides were studied to form high-quality interpolysilicon dielectric layers for embedded non-volatile memory application. It was found that by optimizing the texture and morphology of the polysilicon layers and by optimizing the post-dielectric deposition-anneal, very high-quality dielectric layers can be obtained. In this paper it is shown that for deposited interpolysilicon oxides rapid thermal annealing leads to improved electrical characteristics, like high charge to breakdown (Qbd≈20 C/cm2), lower leakage currents and decreased charge trapping during stress, depending on the RTP anneal ambient. Three annealing ambients are compared: N2, O2 and N2O. Annealing in N2O ambient is shown to be superior to the other annealings.