Combination of normal and oblique incidence polarimetry for the characterization of gratings
AssigneeNanometrics Incorporated
InventorsPablo I. Rovira, Guorong Vera Zhuang, John D. Heaton
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Abstract
A normal incidence spectroscopic polarimeter is combined with an oblique incidence spectroscopic polarimeter to provide an accurate characterization of complex grating structures, e.g., structures with sloping sidewalls, with notches and with multiple underlying layers. The normal incidence spectroscopic polarimeter includes a polarizing element that is in the path of the normal incidence light beam such that the light beam is transmitted through the polarizing element before reaching the sample and after being reflected off the sample. The two systems may advantageously share a single light source and/or the spectrophotometer.
Claims20
A metrology device for characterizing a grating structure on a sample, comprising:
- a normal incidence polarimeter that focuses on said grating structure on said sample, said normal incidence polarimeter having a light source that produces a light beam, said light beam being normally incident on said sample, and a means for polarizing, said normally incident beam passing through said means for polarizing towards said sample and after reflecting off said sample;
- and
- an oblique incidence polarimeter that focuses on said grating structure on said sample.
A metrology apparatus comprising:
- at least one radiation source that produces a beam directed to be normally incident at a location on a sample, and a beam directed to be obliquely incident at said location on said sample;
- a polarizing element in the path of the normally incident beam, said normally incident beam passing through said polarizing element towards said sample and after reflecting off said sample;
- a polarization state generator in the path of the obliquely incident beam, said obliquely incident beam passing through said polarization state generator toward said sample;
- a polarization state detector in the path of said obliquely incident beam after said obliquely incident beam is reflected off said sample, said obliquely incident beam passing through said polarization state detector;
- and
- at least one photometer that detects said normally incident beam after being reflected off said sample and passing through said polarizing element and that detects said obliquely incident beam after being reflected off said sample and passing through said polarization state detector.
A method of characterizing a grating structure on a sample, the method comprising:
- providing a polarized beam to be normally incident on said grating structure;
- providing a polarized beam to be obliquely incident on said grating structure;
- obtaining normal incidence data by detecting the normally incident beam after reflecting off said grating structure;
- obtaining oblique incidence data by detecting the obliquely incident beam after reflecting off said grating structure;
- generating calculated data using an optical model of said grating structure;
- and
- fitting said normal incidence data and said oblique incidence data to said calculated data to characterize said grating structure.
Dependencies are inferred from the claim text.