Effects of boron penetration and resultant limitations in ultra thin pure-oxide and nitrided-oxide gate-films

The boron penetration effect was compared for p/sup +/ poly gate PMOSFETs with pure oxide gates and nitrided oxide gates. For a gate thickness of 6.5 nm, reduced boron dosage and rapid thermal processing solve the problem of boron penetration in the pure oxide case. However, when the film thickness is less than 6.5 nm, only a nitrided oxide film can solve the problem. From the results of EDX analysis in nitrided oxide films, it was found that nitrogen build-up at the interface is small and that a nitrogen concentration of only a few percent leads to complete suppression of boron penetration down to the 2 nm range of film thickness. Excellent characteristics in 2.6 nm nitrided oxide gate p-MOSFETs, free from boron penetration effects, were demonstrated.<>