Gate Oxide Thinning Limit Influenced by Gate Materials

N-type poly Si has no serious influence on thin oxides down to about 30 Ã…. For a boron-doped poly-Si gate, however, current increase characterized by negative gate bias is found. For an Mo gate, gate oxide surface layer of about 20 Ã… next to the gate are deteriorated. By minimizing boron diffusion from a boron-doped poly-Si and Mo penetration during Mo gate formation, both gates will be of practical use for thin gate oxide down to near 30 Ã….