Method for determining absolute reflectance of a material in the ultraviolet range
AssigneeNanometrics Incorporated
InventorVincent J. Coates
Life of this patent
Estimating the term…
Abstract
A method for determining a value of absolute reflectance of a material at a predetermined wavelength, in the ultraviolet range from its measured reflectance which includes system losses contributed by optics, illumination sources, detectors, etc. The method involves the measurement of reflectance from a known material such as single crystal silicon whose absolute reflectance is well known, dividing the measured value by the absolute value to obtain a system efficiency coefficient at the known wavelength and then, without changing the illumination or optics, measuring the reflectance of the unknown material and applying this coefficient to this measured value to obtain its absolute value.
Claims5
A method for determining an absolute reflectance of material from a microscopic measurement of its measured reflectance in the ultraviolet radiation range, said method comprising the steps of:
- determining a value of absolute reflectance of a known material at a predetermined wavelength;
- measuring the reflectance of said known material to obtain a value of measured reflectance with a microscope illuminated with radiation at said predetermined wavelength;
- with said values of absolute reflectance and measured reflectance, calculating an efficiency coefficient representing all absorption and losses caused by the microscope optical system, its reflectance detectors and its illumination system at said predetermined wavelength;
- measuring the reflectance of an unknown material to obtain a second value of measured reflectance with said microscope illuminated with said radiation at said predetermined wavelength;
- applying said efficiency coefficient to said second value of measured reflectance to obtain a value of absolute reflectance of said unknown material.
Dependencies are inferred from the claim text.