Impurity barrier properties of reoxidized nitrided oxide films for use with P/sup +/-doped polysilicon gates

The ability of thin reoxidized nitrided oxide (ONO) gate dielectrics formed by rapid thermal processing to act as a barrier to boron penetration resulting from p/sup +/ poly gate processing are investigated. Measurements comparing the threshold voltage instability of capacitors fabricated with BF/sub 2/ implanted poly gates subjected to various postgate thermal cycles have been performed. The ONO gate dielectrics are found to be an excellent impurity barrier to boron diffusion, even in the presence of fluorine. The extent of the nitridation is also found to affect the diffusion barrier properties, with the highest temperature nitridations forming the best barriers. Reoxidation of the nitrided films reduces the barrier properties somewhat, but improvement is still observed over SiO/sub 2/.<
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