Tunable wavelength illumination system

Abstract

A lithographic apparatus comprises an alignment system including a tunable narrow pass-band filter configured to receive a broad-band radiation and to filter the broad-band radiation into narrow-band linearly polarized radiation. The tunable narrow pass-band filter is further configured to modulate an intensity and wavelength of the narrow-band radiation and to provide a plurality of pass-band filters at a same time or nearly the same time. The alignment system further includes a relay and mechanical interface configured to receive the narrow-band radiation and to adjust a profile of the narrow-band radiation based on physical properties of alignment targets on a substrate. The adjusted narrow-band radiation is focused on the alignment targets using a focusing system.

What is claimed is: 
     
         1 . An alignment system comprising:
 a tunable narrow pass-band filter configured to:
 receive broad-band radiation, and 
 filter the broad-band radiation into narrow-band radiation; 
   a relay and mechanical interface configured to:
 receive the narrow-band radiation, and 
 adjust a profile of the narrow-band radiation based on a physical property of a plurality of alignment targets on a substrate; and 
   a focusing system configured to focus the adjusted narrow-band radiation on the plurality of alignment targets.   
     
     
         2 . The alignment system of  claim 1 , wherein the tunable narrow pass-band filter is configured to filter the broad-band radiation into narrow-band linearly polarized radiation. 
     
     
         3 . The alignment system of  claim 1 , wherein the tunable narrow pass-band filter is further configured to select a plurality of narrow-band wavelength set points at a same time or nearly the same time. 
     
     
         4 . The alignment system of  claim 1 , wherein the tunable narrow pass-band filter is further configured to modulate intensity and wavelength of the broad-band radiation. 
     
     
         5 . The alignment system of  claim 1 , wherein the tunable narrow pass-band filter is further configured to provide a plurality of pass-band filters at a same time or nearly the same time. 
     
     
         6 . The alignment system of  claim 1 , wherein the tunable narrow pass-band filter is an Acousto-Optical Tunable Filter (AOTF). 
     
     
         7 . The alignment system of  claim 1 , wherein the narrow-band radiation has a mean wavelength of approximately 980 nm. 
     
     
         8 . The alignment system of  claim 1 , wherein the broad-band radiation ranges from 450 nm to 2500 nm. 
     
     
         9 . A method to align a substrate in a lithographic apparatus, the method comprising:
 filtering, using a tunable narrow pass-band filter, a broad-band radiation to generate a narrow-band polarized radiation;   receiving, using a relay and mechanical interface, the narrow-band polarized radiation from the tunable narrow pass-band filter;   adjusting a profile of the narrow-band polarized radiation; and   focusing the adjusted narrow-band polarized radiation on an alignment target on the substrate.   
     
     
         10 . The method of  claim 9 , further comprising:
 selecting, using the tunable narrow pass-band filter, a plurality of narrow-band wavelength set points at a same time or nearly the same time.   
     
     
         11 . The method of  claim 9 , further comprising:
 modulating, using the tunable narrow pass-band filter, intensity and wavelength of the broad-band radiation.   
     
     
         12 . The method of  claim 9 , further comprising:
 providing, using the tunable narrow pass-band filter, a plurality of pass-band filters at a same time or nearly the same time.   
     
     
         13 . The method of  claim 9 , wherein the tunable narrow pass-band filter is an Acousto-Optical Tunable Filter (AOTF). 
     
     
         14 . A lithographic apparatus comprising:
 a tunable narrow pass-band filter configured to:
 receive a broad-band radiation, and 
 filter the broad-band radiation into narrow-band radiation; 
   a relay and mechanical interface configured to:
 receive the narrow-band radiation, and 
 adjust a profile of the narrow-band radiation based on physical properties of alignment targets on a substrate; and 
   a focusing system configured to focus the adjusted narrow-band radiation on the plurality of alignment targets.   
     
     
         15 . The lithographic apparatus of  claim 14 , wherein the tunable narrow pass-band filter is configured to filter the broad-band radiation into narrow-band linearly polarized radiation. 
     
     
         16 . The lithographic apparatus of  claim 14 , wherein the tunable narrow pass-band filter is further configured to select a plurality of narrow-band wavelength set points at a same time or nearly the same time. 
     
     
         17 . The lithographic apparatus of  claim 14 , wherein the tunable narrow pass-band filter is further configured to modulate intensity and wavelength of the broad-band radiation. 
     
     
         18 . The lithographic apparatus of  claim 14 , wherein the tunable narrow pass-band filter is further configured to provide a plurality of pass-band filters at a same time or nearly the same time. 
     
     
         19 . The lithographic apparatus of  claim 14 , wherein the tunable narrow pass-band filter is an Acousto-Optical Tunable Filter (AOTF). 
     
     
         20 . The lithographic apparatus of  claim 14 , wherein the tunable narrow pass-band filter comprises a library of spectral filters.