Patent ID: 6489624
Filing Date: 2002-12-03
Classification: G01B

Abstract:
An apparatus for measuring thickness of a patterned layer on a workpiece comprising a planar substrate to which the patterned layer has been applied, the patterned layer being subjectable to a process that causes a time-varying change in the thickness and/or planarity of the patterned layer, the apparatus comprising:(a) a probe light source that produces a beam of probe light having multiple wavelengths and a transverse area larger than an area of a unit cell on the patterned layer and that directs the beam to be incident on selected pattern features of the patterned layer and produces a signal light from reflection of the probe light from the patterned layer or transmission of the probe light through the patterned layer by interaction of probe light with the selected pattern features of the patterned layer; (b) a light detector situated so as to receive and detect multiple wavelengths of the signal light and produce a corresponding electronic signal encoding data regarding intensity at various wavelengths of the detected signal light; and (c) a processor connected to the light detector, the processor being configured to calculate, from the electronic signal, a spectrum of intensity versus wavelength based on the reflection or transmission of the probe light by the selected pattern features, the intensity spectrum providing data indicating the thickness and/or planarity of the patterned layer based on a comparison of the spectrum of intensity and a reference spectrum of intensity based on reflection or transmission from pattern features of a reference patterned layer corresponding to the selected pattern features.