Patent ID: 8668383
Filing Date: 2014-03-11
Classification: G01J,G01K

Abstract:
1. A method for determining the temperature of a wafer comprising: directing light towards a first side of a wafer, at least part of the wafer having an optical absorption at a first wavelength that varies with temperature and having an optical path length at a second wavelength that varies with temperature; heating the wafer; measuring an absorption characteristic of the wafer at the first wavelength to determine an absolute temperature value; making at least a first measurement and a second measurement of a value of an optical property that is sensitive to the optical path length of the light being directed through at least part of the wafer, wherein the first measurement and the second measurement are performed at different temperatures of the wafer; determining a change in temperature based upon the measured values of the optical property that are sensitive to the optical path length through at least part of the wafer; and determining a temperature of the wafer based upon the determined absolute temperature value and the determined change in temperature from the measured values of the optical property that are sensitive to the optical path length through at least part of the wafer.