Patent ID: 8873050
Filing Date: 2014-10-28
Classification: G01J

Abstract:
1. A system configured to determine information for a wafer, comprising: an illumination subsystem configured to direct light having wavelengths in a broadband range to a wafer; a first grating positioned in a path of the light from the wafer, wherein the first grating diffracts the light from the wafer having wavelengths in a first portion of the broadband range and does not diffract the light from the wafer having wavelengths in a second portion of the broadband range; a second grating positioned in the path of the light that is not diffracted by the first grating, wherein the second grating diffracts the light from the wafer having the wavelengths in the second portion of the broadband range, and wherein the first and second gratings are arranged in series; a first detector configured to generate first output responsive to the light diffracted by the first grating; a second detector configured to generate second output responsive to the light diffracted by the second grating; and a computer subsystem configured to determine information for the wafer using the first and second output.