Expediting spectral measurement in semiconductor device fabrication

1. An interferometric-spectroscopy metrology tool comprising:

an interferometric microscope configured to create a first interferogram from light beams derived from a first white light illumination during vertical conveyance of a focal lens, the first interferogram captured by a single-pixel detector associated with the interferometric microscope, wherein the light beams include a beam reflected from a broadband reflector so as to characterize a spectrum of the first white light illumination in the first interferogram; and

a computer configured to render the first interferogram into a frequency spectrum through application of a Fourier transformation on the first interferogram;

wherein the interferometric microscope is further configured to create a second interferogram from a second white light illumination during focusing of the second white illumination during overlay sequence, the second white light illumination comprising a reference light beam and a test light beam, the test light beam reflected from a processed wafer having microstructures, the second interferogram captured by the single-pixel detector from the recombination of the reference light beam and the test light beam; and

wherein the computer is further configured to render the second interferogram into a composite frequency spectrum characterizing the second white light illumination and the spectral reflectivity of the processed through application of a Fourier transformation on the second interferogram.

2. The tool of claim 1 , wherein the broadband reflector is implemented as a mirror.

3. The tool of claim 1 , wherein the broadband reflector is implemented as bare silicon.

4. The tool of claim 1 , wherein the interferometric microscope includes a Linnik beam splitter cube.

5. A method of expediting acquisition of spectral data in semiconductor device fabrication metrology; the method comprising:

splitting a first white light illumination into two light beams with an interferometric microscope;

reflecting one of the two light beams off a broadband reflector;

receiving a first interferogram on a single-pixel detector, the first interferogram formed from recombination of the two light beams;

applying a Fourier transform to the first interferogram so as to render the first interferogram into a frequency spectrum characterizing the first white light illumination;

splitting a second white light illumination into a reference light beam and a test light beam with the interferometric microscope;

capturing a second interferogram on the single-pixel detector during focusing of the second white light illumination during overlay sequence, the second interferogram formed from recombination of the reference light beam and the test light beam, the test light beam reflected from a processed wafer having microstructures; and

applying a Fourier transform to the second interferogram so as to render the second interferogram into a composite frequency spectrum characterizing both the second white light illumination and spectral reflectivity of the processed wafer.

6. The method of claim 5 , wherein the broadband reflector is implemented as a mirror.

7. The method of claim 5 , wherein the broadband reflector is implemented as a bare wafer.

8. The method of claim 7 , further comprising dividing the composite frequency spectrum by the frequency spectrum of the first white light illumination so as to generate a frequency spectrum characterizing a reflectivity of the processed wafer.