A method for polishing wafers includes polishing a process layer formed on a wafer, the process layer overlying a grating structure; illuminating at least a portion of the process layer and the grating structure; measuring light reflected from the illuminated portion of the process layer and the grating structure to generate a reflection profile; comparing the measured reflection profile to a target reflection profile having an acceptable degree of planarity; and terminating the polishing of the process layer based on the comparison of the measured reflection profile and the target reflection profile. A metrology tool adapted to measure a wafer having a grating structure and a process layer formed over the grating structure after initiation of a polishing process includes a light source, a detector, and a data processing unit. The light source is adapted to illuminate at least a portion of the process layer overlying the grating structure. The detector is adapted to measure light reflected from the illuminated portion of the process layer and the grating structure to generate a reflection profile. The data processing unit is adapted to compare the measured reflection profile to a target reflection profile having an acceptable degree of planarity and generate an endpoint signal based on the comparison of the measured reflection profile and the target reflection profile.
A method for polishing a thin film formed on a substrate includes planarizing a thin film formed on a reference substrate by a CMP process such that the thin film remains on the reference substrate. After the planarizing, the thin film is cleaned, and then values of .DELTA. and .PSI. with respect to the cleaned thin film are measured by ellipsometry. A physical property of the thin film is determined based on the .DELTA. and .PSI. which have been measured by ellipsometry, and a polishing condition for an other substrate having a thin film to be polished is set based on physical property data which are obtained by the determining of the physical property.
