Highly Sensitive Optical Method for the Characterization of SiO2 Films in Bonded Wafers

Abstract
The thickness of very thin films (1-10 nanometers thick) and the frequency of the longitudinal optical mode of the material composing the film (related to its chemical and structural properties) are demonstrated to be measurable with high sensitivity by means of infrared transmission. The particular optical configuration proposed permits the analysis of the SiO2 film in bonded wafers. It is shown that the sensitivity of this new method increases as the films are made thinner.