Integrated phase angle and optical critical dimension measurement metrology for feed forward and feedback process control

Abstract

Methods and apparatus for controlling the critical dimensions and monitoring the phase shift angles of photomasks. Critical dimensions measurement data before wafer processing and after wafer processing are collected by an integrated metrology tool to adjust the process recipe, to determine if the critical dimensions are in specification and to determine if additional etching is required. Phase shift angle and uniformity across substrate measurement after wafer processing are collected by an integrated metrology tool to determine if the phase shift angle and its uniformity are in specification. The real time process recipe adjustment and determination if additional etching is requires allow tightening of the process control. The phase shift angle and uniformity monitoring allows in-line screening of phase shift photomasks.

1 . An apparatus for controlling the critical dimensions of a photomask substrate, comprising: 
 a photomask etch chamber for processing a photomask substrate;    a measuring tool for measuring critical dimension information prior to and after processing by the process chamber; and    a computer system, coupled to the process chamber and the measurement tool, for storing the critical dimension information.    
     
     
         2 . The apparatus of  claim 1 , wherein the measuring tool can operate under either reflective mode or transmission mode.  
     
     
         3 . The apparatus of  claim 1  further comprising: 
 a controller coupled to the etch chamber and in communication with the computer system; and    computer readable media containing instructions, that when executed by the controller, cause the etch chamber to perform a method for controlling critical dimensions of a photomask substrate comprising: 
 measuring pre-etch critical dimensions of a printed photolithographic pattern formed a metal layer disposed on a photomask substrate the measuring tool;  
 providing an initial etch recipe for a metal etch process to be preformed in the etch chamber;  
 modifying the etch recipe based on the pre-etch critical dimension data of said photomask substrate;  
 performing the etch process on said photomask substrate in the etch chamber based on the modified etch recipe to form an etched pattern on said photomask substrate; and  
 measuring post-etch critical dimensions of the etched pattern.  
   
     
     
         4 . The apparatus of  claim 3 , wherein the computer readable media contains instructions, that when executed by the controller, cause the method to further comprise; 
 modifying the initial etch recipe for the next photomask substrate based on the post-etch critical dimensions data.    
     
     
         5 . The apparatus of  claim 1  further comprising: 
 a controller coupled to the etch chamber and in communication with the computer system; and    computer readable media containing instructions, that when executed by the controller, cause the etch chamber to perform a method for controlling critical dimensions of a photomask substrate comprising: 
 etching the features according to an etch recipe to be performed in the etch chamber for specified critical dimensions of the features modified based on a measured pre-etch critical dimensions of the features by the measuring tool;  
 measuring the features to determine conformity with the specified critical dimensions by the measuring tool;  
 determining from the measurement the modifications of the etch recipe required to conform to the specified critical dimensions; and  
 etching another photomask substrate in the etch chamber according to the modified etch recipe.  
   
     
     
         6 . An apparatus for monitoring the phase shift angles of a phase shift photomask substrate, comprising: 
 a process chamber for processing a substrate;    a measuring tool positioned for measuring phase shift angle and its uniformity across the substrate after the substrate is processed by the process chamber; and    a computer system, coupled to the process chamber and the measurement tool, for storing the measured information.    
     
     
         7 . The apparatus of  claim 6  wherein the process chamber is an etch chamber.  
     
     
         8 . The apparatus of  claim 6  further comprising: 
 a controller coupled to the etch chamber and in communication with the computer system; and    computer readable media containing instructions, that when executed by the controller, cause the etch chamber to perform a method for controlling critical dimensions of a photomask substrate comprising: 
 measuring pre-etch critical dimensions of a printed photolithographic pattern formed a metal layer disposed on a photomask substrate the measuring tool;  
 providing an initial etch recipe for a metal etch process to be preformed in the etch chamber;  
 modifying the etch recipe based on the pre-etch critical dimension data of said photomask substrate;  
 performing the etch process on said photomask substrate in the etch chamber based on the modified etch recipe to form an etched pattern on said photomask substrate; and  
 measuring post-etch critical dimensions of the etched pattern.  
   
     
     
         9 . The apparatus of  claim 8 , wherein the computer readable media contains instructions, that when executed by the controller, cause the method to further comprise; 
 modifying the initial etch recipe for the next photomask substrate based on the post-etch critical dimensions data.    
     
     
         10 . The apparatus of  claim 6  further comprising: 
 a controller coupled to the etch chamber and in communication with the computer system; and    computer readable media containing instructions, that when executed by the controller, cause the etch chamber to perform a method for controlling critical dimensions of a photomask substrate comprising: 
 etching the features according to an etch recipe to be performed in the etch chamber for specified critical dimensions of the features modified based on a measured pre-etch critical dimensions of the features by the measuring tool;  
 measuring the features to determine conformity with the specified critical dimensions by the measuring tool;  
 determining from the measurement the modifications of the etch recipe required to conform to the specified critical dimensions; and  
 etching another photomask substrate in the etch chamber according to the modified etch recipe.  
   
     
     
         11 . An apparatus for controlling the critical dimension and monitoring phase shift angles of a phase shift photomask substrate, comprising: 
 a process chamber for processing a substrate;    a measuring tool positioned for measuring phase shift angle and its uniformity across the substrate after the substrate is processed by the process chamber;    a measuring tool positioned for measuring critical dimension information prior to and after processing by the process chamber; and    a computer system, coupled to the process chamber and the measurement tool, for storing the critical dimension information.    
     
     
         12 . The apparatus of  claim 11  wherein the process chamber is an etch chamber.  
     
     
         13 . The apparatus of  claim 11  further comprising: 
 a controller coupled to the etch chamber and in communication with the computer system; and    computer readable media containing instructions, that when executed by the controller, cause the etch chamber to perform a method for controlling critical dimensions of a photomask substrate comprising: 
 measuring pre-etch critical dimensions of a printed photolithographic pattern formed a metal layer disposed on a photomask substrate the measuring tool;  
 providing an initial etch recipe for a metal etch process to be preformed in the etch chamber;  
 modifying the etch recipe based on the pre-etch critical dimension data of said photomask substrate;  
 performing the etch process on said photomask substrate in the etch chamber based on the modified etch recipe to form an etched pattern on said photomask substrate; and  
 measuring post-etch critical dimensions of the etched pattern.  
   
     
     
         14 . The apparatus of  claim 13 , wherein the computer readable media contains instructions, that when executed by the controller, cause the method to further comprise; 
 modifying the initial etch recipe for the next photomask substrate based on the post-etch critical dimensions data.    
     
     
         15 . The apparatus of  claim 11  further comprising: 
 a controller coupled to the etch chamber and in communication with the computer system; and    computer readable media containing instructions, that when executed by the controller, cause the etch chamber to perform a method for controlling critical dimensions of a photomask substrate comprising: 
 etching the features according to an etch recipe to be performed in the etch chamber for specified critical dimensions of the features modified based on a measured pre-etch critical dimensions of the features by the measuring tool;  
 measuring the features to determine conformity with the specified critical dimensions by the measuring tool;  
 determining from the measurement the modifications of the etch recipe required to conform to the specified critical dimensions; and  
 etching another photomask substrate in the etch chamber according to the modified etch recipe.