Patent ID: 7280230

Claim:
An apparatus for measuring one or more parameters associated with a diffracting structure, said diffracting structure located adjacent to one or more first film structures, said diffracting structure or at least a first layer of said one or more first film structures comprising a first material and having associated thickness and optical index information, comprising: a second structure; an instrument measuring data associated with the second structure, said second structure and said diffracting structure or said at least first layer formed from the same manufacturing process, said second structure having substantially the same thickness as the diffracting structure or said at least first layer, and/or comprises a second material having substantially the same optical properties as those of the first material; an optical source directing a beam of electromagnetic radiation at a plurality of wavelengths at said diffracting structure and the one or more first film structures; at least one detector detecting intensity and/or phase data of a diffraction at said plurality of wavelengths from said diffracting structure of said beam; and a computer determining said one or more parameters using the data associated with the second structure and data detected from said diffracting structure in an optimization process, wherein the computer feeds forward the data associated with the second structure to said optimization process to simplify the optimization process for determining said one or more parameters.