Impact ofWSi,, MetalGateStoichiometry onFully Depleted SOI MOSFETsElectrical Properties

EOT increase wasobserved withWSixon SiO2gatedielectric Forthefirst time, wereport fully depleted SOIMOS transistors with compared totheTiNgate. Thismaybeduetothefluorine (F)and/or WSixgateonHfO2.Gateworkfunction, dielectric properties and chlorine (Cl) diffusion into SiO2(Fig. 7).SiO2dielectric constant can channel mobility arepresented interms ofSi/Wratio andcompared to decrease orfreeoxygenatomcandiffuse totheSiO2/Si interface TiNgatedevices. A 35%electron mobility gainwasobtained witha inducing gateoxide re-growth [10]. Compared toSiO2, HfO2blocks F WSixgatedevice ascompared toaTiNgatetransistor. Itwasfound andClatomsdiffusion attheinterface (Fig. 7),limiting theEOT thatbothmobility anddielectric characteristics weredrastically increase. Theslight EOT enhancement observed onWSix/HfO2 gate improved bydecreasing theSi/Wratio ofWSixfilms.