Ultrathin Oxide Grown on Polysilicon by Using an Electron Cyclotron Resonance N2O Plasma

Abstract

We have developed a process for growing ultrathin oxide on a polysilicon layer by using an electron cyclotron resonance (ECR) N2O plasma. Sub-4-nm thick polyoxides were grown on n(+) and pf polysilicon layers and were characterized. These oxides had larger breakdown fields, smaller electron trapping characteristics, and larger Q(BD) values than those of thermal polyoxides. The electron trapping characteristics of ECR N2O plasma polyoxides, which were smaller than those of thermal polyoxides at positive bias, resulted from the smaller roughness of the polysilicon surface after the oxidation process. Under a negative constant-current stress of 20 mA/cm(2), Q(BD) values of up to 86 C/cm(2) for polyoxide on n(+) polysilicon and up to 80 C/cm(2) for polyoxide on p(+) polysilicon were obtained. These ultrathin plasma polyoxides would be good candidates for future inter-poly dielectrics and gate oxides for thin film transistors.