Advanced exposure techniques for programmable lithography

Abstract

Advanced techniques for programmable photolithography provide enhanced resolution and other aspects of a photolithography system. A combination of multiple exposures and movement of a substrate relative to a programmable mask in a photolithographic system accomplishes single shutter exposure overlaps to create features smaller than the single shutter intensity profile, i.e., sub-pixel resolution. Advanced timing adjustment capabilities are used to modulate the light so that no unwanted features are created. Additionally, a library of shapes may be used, one shape on each pixel, with the small features of the shapes created by phase shifting. Patterns are built up by multiple exposures with relative movement of the mask and resist so as to place each shape from the library where it is needed on the resist. Electro-Optic phase shifting material may be applied to the shutter so as to adjust the single shutter intensity profile, or to adjust the interaction of adjacent shutters. An apodizing mask may be used to engineer the wavefronts of the light striking the resist in such a manner to achieve better resolution.

1 . A method for exposing a substrate using a programmable mask having plural pixels, the method comprising: 
 controlling the plural pixels of said programmable mask to provide an exposure pattern;    applying a first phase shift amount to at least a first of said plural pixels;    applying a second phase shift amount different from said first phase shift to at least a second of said plural pixels; and    exposing the substrate by passing illuminating energy through said programmable mask, said applied first and second phase shift amounts adjusting the intensity exposure profile of energy striking the substrate.    
   
   
       2 . The method of  claim 1  wherein said first phase shift amount differs from said second phase shift by about 180 degrees.  
   
   
       3 . The method of  claim 1  wherein said applying steps are performed by passing said illuminating energy through an optical material having a refractive index.  
   
   
       4 . The method of  claim 3  wherein said exposing step includes directing electromagnetic energy through said programmable mask and said optical material toward the substrate.  
   
   
       5 . The method of  claim 3  further including selectively applying an electric field to said material to selectively change the phase shift applied thereby.  
   
   
       6 . The method of  claim 1  further including providing an electro-optical material having an array of discrete programmable phase shift elements corresponding to at least some of said programmable mask plural pixels, and said applying steps comprise programmably determining the amount of phase shift to be applied at each of said discrete programmable phase shift elements.  
   
   
       7 . The method of  claim 1  wherein said applying steps each comprise selectively applying an electric field to discrete electro-optical programmable phase shift elements to provide programmable pixel-by-pixel phase shifts for the plural pixels.  
   
   
       8 . The method of  claim 1  wherein said applying steps includes controlling said first and second phase shifts in accordance with a pattern.  
   
   
       9 . The method of  claim 1  wherein said applying steps include providing a constructive or destructive interference pattern corresponding to at least part of a desired exposure pattern.  
   
   
       10 . A system for exposing a substrate comprising: 
 a programmable mask having plural pixels;    a controller coupled to said programmable mask, said controller controlling the plural pixels of said programmable mask to provide an exposure pattern;    a phase shifting arrangement optically coupled to said programmable mask, said phase shifting arrangement applying a first phase shift amount to at least a first of said plural pixels and applying a second phase shift amount different from said first phase shift to at least a second of said plural pixels; and    a source that directs illuminating energy through said programmable mask toward said substrate, said applied first and second phase shift amounts adjusting the intensity exposure profile of energy striking the substrate to provide a desired exposure pattern.    
   
   
       11 . The system of  claim 10  wherein said phase shift arrangement applies said first phase shift amount that differs from said second phase shift by about 180 degrees.  
   
   
       12 . The system of  claim 10  wherein said phase shift arrangement applies said first phase shift amount of about zero and applies said second phase shift amount different from zero.  
   
   
       13 . The system of  claim 10  wherein said phase shift arrangement comprises an optical material having a refractive index.  
   
   
       14 . The system of  claim 13  wherein said source directs electromagnetic energy through said programmable mask and said optical material toward the substrate.  
   
   
       15 . The system of  claim 13  wherein said phase shifting arrangement selectively applies an electric field to said material to selectively change the phase shift applied thereby.  
   
   
       16 . The system of  claim 10  wherein said phase shifting arrangement comprises an electro-optical material having an array of programmable phase shift elements corresponding to said programmable mask plural pixels, and said controller is coupled to said phase shifting arrangement and programmably controls the amount of phase shift to be applied at each of said programmable phase shift elements.  
   
   
       17 . The system of  claim 16  wherein said controller selectively applies an electric field to said programmable phase shift elements to provide programmable pixel-by-pixel phase shifts for the plural pixels.  
   
   
       18 . The system of  claim 10  wherein said phase shifting arrangement controls said phase shifts in accordance with a pattern.  
   
   
       19 . The system of  claim 10  wherein said phase shifting arrangement provides a constructive or destructive interference pattern corresponding to at least part of a desired exposure pattern.