MOSFET transistors fabricated with high permitivity TiO/sub 2/ dielectrics

Abstract

Layers of polycrystalline anatase TiO/sub 2/ have been deposited through the thermal decomposition of titanium tetrakisisopropoxide (TTIP). 500 /spl Aring/ films deposited and annealed in oxygen at 750/spl deg/C had average roughnesses (R/sub a/) of about 30 /spl Aring/. Capacitors made from 190 /spl Aring/ layers of TiO/sub 2/ displayed a voltage dependent accumulation capacitance. This was postulated to be caused by finite width effects in the accumulation layer which we have dubbed the quantum capacitance effect. N-channel transistors made with these films showed near ideal behavior, but mobilities were significantly lower than those of thermal oxide MOSFETs. This mobility reduction was believed to be caused by interface states, which fell below 10/sup 11/ cm/sup -2/ eV/sup -1/ at midgap, but rose sharply on either side, unlike the "U" shaped behavior in thermal oxide MOSFET's.