Patent ID: 8989890
Filing Date: 2015-03-24
Classification: B24B,C01G,G01B,H01L

Abstract:
1. A method, comprising: storing a target thickness in a computer; after storing the estimated or target thickness, polishing a first substrate having a layer of GST, the layer of GST disposed over an underlying layer; during polishing, directing a non-polarized light beam onto the layer of GST, the nonpolarized light beam reflecting from the first substrate to generate a reflected light beam having an infra-red component; during polishing, generating a sequence of measurements of intensity of a selected wavelength in the infra-red component, the selected wavelength being such that intensity values of the reflected light beam at the selected wavelength provide no local peaks or valleys across a thickness range of at least 500 A of GST that includes the target thickness and no intensity value for the selected wavelength corresponds to multiple thicknesses within the thickness range, wherein the intensity values are monotonic within the thickness range; and in the computer, determining a time at which the sequence of measurements exhibits a predefined feature indicating a the target thickness of the layer.