Optical and electrical thickness measurements of alternate gate dielectrics: A fundamental difference

Abstract

We will describe a fundamental difference between the interpretation of optical and electrical measurements of gate dielectric thickness. This difference has major ramifications on the characterization of, and metrology for, advanced, alternate gate dielectrics and gate dielectric stacks. The purpose of this paper is to clear up possible misunderstandings that arise when comparing the thickness of gate dielectrics derived from optical and electrical measurements. Oxynitride data will be used to illustrate the divergence between optical and electrical measurements of thickness for films with a permittivity near and slightly above that of SiO2. Experimental characterization of Ta2O5 dielectrics will demonstrate the complementary nature of electrical and optical measurements.