EUV In-Situ Linearity Calibration for TDI Image Sensors Using Test Photomasks

Abstract

A photomask includes a plurality of distinctly patterned regions to provide different respective intensities of extreme ultraviolet (EUV) light in response to illumination with an EUV beam. The photomask may be part of a system that also includes a time-delay-integration (TDI) inspection tool with an EUV light source and a TDI sensor. The EUV light source is to generate the EUV beam. The photomask is to be loaded into the TDI inspection tool. The system further includes a reference intensity detector to be mounted in the TDI inspection tool to measure intensities of EUV light collected from the photomask.

What is claimed is: 
     
         1 . A system, comprising:
 a photomask comprising a plurality of distinctly patterned regions to provide different respective intensities of extreme ultraviolet (EUV) light in response to illumination with an EUV beam.   
     
     
         2 . The system of  claim 1 , wherein:
 the plurality of distinctly patterned regions comprises a plurality of regions having respective line-space grating patterns of alternating EUV-absorber lines and EUV-reflective multi-layer coatings; and   the respective line-space grating patterns have distinct respective absorber duty ratios, the absorber duty ratios being ratios of EUV-absorber line width to grating pitch.   
     
     
         3 . The system of  claim 2 , wherein the respective line-space grating patterns have distinct respective EUV-absorber line widths but have identical grating pitches. 
     
     
         4 . The system of  claim 2 , wherein:
 the EUV-absorber lines comprise tantalum boron nitride (TaBN); and   the EUV-reflective multi-layer coatings comprise alternating layers of molybdenum (Mo) and silicon (Si).   
     
     
         5 . The system of  claim 1 , wherein:
 the plurality of distinctly patterned regions comprises a plurality of regions having respective EUV-reflective multi-layer coatings; and   the respective EUV-reflective multi-layer coatings have distinct respective numbers of layers.   
     
     
         6 . The system of  claim 5 , wherein the respective EUV-reflective multi-layer coatings comprise distinct respective numbers of alternating layers of Mo and Si. 
     
     
         7 . The system of  claim 1 , wherein the plurality of distinctly patterned regions composes a graded EUV-reflective multi-layer coating. 
     
     
         8 . The system of  claim 7 , wherein:
 the graded EUV-reflective multi-layer coating comprises a number of alternating layers of Mo and Si;   the alternating layers of Mo and Si have graded thicknesses in a first direction and uniform thicknesses in a second direction perpendicular to the first direction; and   the alternating layers of Mo and Si have a constant thickness ratio.   
     
     
         9 . The system of  claim 1 , wherein:
 the plurality of distinctly patterned regions comprises a plurality of regions comprising respective EUV-absorber areas and respective EUV-reflective multi-layer coatings, the respective EUV-absorber areas being situated above the respective EUV-reflective multi-layer coatings; and   the respective EUV-absorber areas have distinct respective thicknesses.   
     
     
         10 . The system of  claim 9 , wherein:
 the respective EUV-absorber areas comprise TaBN and a TaBO capping layer above the TaBN; and   the respective EUV-reflective multi-layer coatings comprise identical numbers of alternating layers of Mo and Si.   
     
     
         11 . The system of  claim 1 , further comprising:
 a time-delay-integration (TDI) inspection tool comprising:
 an EUV light source to generate the EUV beam, and 
 a TDI sensor, 
 wherein the photomask is to be loaded into the TDI inspection tool; and 
   a reference intensity detector to be mounted in the TDI inspection tool to measure intensities of EUV light collected from the photomask.