Measuring elastic moduli of dielectric thin films using an optical metrology system

Abstract

An optical metrology system is provided with a data analysis method to determine the elastic moduli of optically transparent dielectric films such as silicon dioxide, other carbon doped oxides over metal or semiconductor substrates. An index of refraction is measured by an ellipsometer and a wavelength of a laser beam is measured using a laser spectrometer. The angle of refraction is determined by directing a light pulse focused onto a wafer surface, measuring a first set of x, y, and zcoordinates, moving the wafer in the z direction, directing the light pulse onto the wafer surface and measuring a second set of x, yand zcoordinates, using the coordinates to calculate an angle of incidence, calculating an angle of refraction from the calculated angle of incidence, obtaining a sound velocity v, from the calculated angle of refraction and using the determined sound velocity v, to calculate a bulk modulus. Hardware calibration and adjustments for the optical metrology system are also provided in order to minimize the variation of the results from tool to tool down to about 0.5% or below.