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Optical System for Measurement of Exposure Plane Irradiance in Lithographic Tools

IP.com Disclosure Number: IPCOM000034993D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Cogley, RM: AUTHOR [+2]

Abstract

A spectrometer built into an enclosure the same size and shape as a wafer chuck is used to measure irradiance energy in discrete wavelength bands at any number of points in the exposure plane of lithographic exposure tools. Referring to the figure, one end of fiber bundle 4 is formed into a circular light collection region 2 in the wafer exposure plane. Light collected in region 2 is transmitted by fiber bundle 4 formed into a linear array or slit image at its opposite end. The slit image formed by fiber bundle 4 is matched to the numerical aperture of diffraction grating 14 by magnification mirror 6. The slit image continues through a series of folding mirrors 8, 10, and 12 to flat field exposure grating 14. The grating 14 disperses the light from the magnified slit image into its spectral components.

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Optical System for Measurement of Exposure Plane Irradiance in Lithographic Tools

A spectrometer built into an enclosure the same size and shape as a wafer chuck is used to measure irradiance energy in discrete wavelength bands at any number of points in the exposure plane of lithographic exposure tools. Referring to the figure, one end of fiber bundle 4 is formed into a circular light collection region 2 in the wafer exposure plane. Light collected in region 2 is transmitted by fiber bundle 4 formed into a linear array or slit image at its opposite end. The slit image formed by fiber bundle 4 is matched to the numerical aperture of diffraction grating 14 by magnification mirror 6. The slit image continues through a series of folding mirrors 8, 10, and 12 to flat field exposure grating 14. The grating 14 disperses the light from the magnified slit image into its spectral components. Folding mirror 16 provides the proper image distance for the flat field grating 14 so that an image the same size as the object is formed on photodiode array 8. The entire spectrum of interest is dispersed across the full width of an array of photodiodes 8. Electronics for converting signals from the photodiode array 8 into output of irradiance energy vs. wavelength is housed in region 20. Thus, means for sampling light from a small area of the exposure plane of a lithographic tool and determining its spectral energy content are contained within an enclosure 22 which may be substitute...