The effects of boron penetration on p+ polysilicon gatedPMOS devices |
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Authors: | Pfiester J.R. Baker F.K. Mele T.C. Tseng H.-H. Tobin P.J. Hayden J.D. Miller J.W. Gunderson C.D. Parrillo L.C. |
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Affiliation: | Motorola Inc., Austin, TX; |
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Abstract: | The penetration of boron into and through the gate oxides of PMOS devices which employ p+ doped polysilicon gates is studied. Boron penetration results in large positive shifts in VFB , increased PMOS subthreshold slope and electron trapping rate, and decreased low-field mobility and interface trap density. Fluorine-related effects caused by BF2 implantations into the polysilicon gate are shown to result in PMOS threshold voltage instabilities. Inclusion of a phosphorus co-implant or TiSi2 salicide prior to gate implantation is shown to minimize this effect. The boron penetration phenomenon is modeled by a very shallow, fully-depleted p-type layer in the silicon substrate close to the SiO 2/Si interface |
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