Characterization of ultra-thin dielectric films buried under poly-Si electrodes using x-ray reflectivity

Abstract

Probe of deep buried gate dielectric thin films under poly-Si electrode capping layer by x-ray reflectivity using synchrotron radiation has been demonstrated. The structural variation in gate insulator was observed sensitively and the depth profiles of density were obtained with depth resolution less than 4 A. The structural parameters were evaluated quantitatively from discrete-layers model using the modified Parratt recursive formalism, provided that the real interfaces could be represented by a continuous refractive index profile. The depth profiles from the discrete-layers model to consider the interfacial roughnesses were compared to those from the continuous-media model within the experimental limit that doesn’t include interfacial roughness. Consistency was so satisfactory that we could suggest the x-ray reflectivity to be the reliable measurement of the thickness of ultra-thin dielectric films and to be useful for the off-line characterizations of structural variation from thermal processes.