Apparatus and process for determination of dynamic scan field curvature

Abstract

A process for the determination of focal plane deviation uniquely due to the scanning dynamics associated with a photolithographic scanner is described. A series of lithographic exposures is performed on a resist coated silicon wafer using a photolithographic scanner. The lithographic exposures produce an array of focusing fiducials that are displaced relative to each other in a unique way. The resulting measurements are fed into a computer algorithm that calculates the dynamic scanning field curvature in an absolute sense in the presence of wafer height variation and other wafer/reticle stage irregularities. The dynamic scan field curvature can be used to improve lithographic modeling, overlay modeling, and advanced process control techniques related to scanner stage dynamics.

1 . An apparatus for determining dynamic scan field curvature of a photolithographic scanner, the apparatus comprising: 
 a data interface that receives data taken from a developed substrate; and    a processor configured to accept metrology data from the data interface wherein the data is obtained from measuring a substrate with exposed focusing fiducials and dynamic lens field curvature data and to output dynamic scan field curvature in accordance with focal plane deviation values based on measurements of the focusing fiducials on the substrate.    
   
   
       2 . A method as defined in  claim 1 , wherein the substrate is a semiconductor wafer.  
   
   
       3 . A method as defined in  claim 1 , wherein the substrate is a flat panel display.  
   
   
       4 . A method as defined in  claim 1 , wherein the substrate is a reticle.  
   
   
       5 . A method as defined in  claim 1 , wherein the substrate is an electronic recording media.  
   
   
       6 . A photolithographic projection scanner comprising: 
 a projection lens;    a reticle stage and a substrate carrier that can be positioned relative to each other; and    a processor that can control the projection scanner to position the reticle stage and substrate carrier in accordance with an exposure sequence, and adjust the scanner in accordance with measurements of focusing fiducials exposed on the substrate and a dynamic lens field curvature map so as to minimize the dynamic lens field curvature of the scanner.    
   
   
       7 . A scanner as defined in  claim 6 , whereby the measurements of the focusing fiducials are made on a measurement subsystem of the scanner.  
   
   
       8 . A scanner as defined in  claim 6 , whereby the substrate carrier is a semiconductor wafer carrier.