Inverse Lithography For High Transmission Attenuated Phase Shift Mask Design And Creation

Abstract

Various implementations of the invention provide for generation of a high transmission phase shift mask layout through inverse lithography techniques. In various implementations of the present invention, a set of mask data having a plurality of pixels is generated. The transmission value associated with each pixel may then be determined through an inverse lithography technique. With various implementations of the invention, the inverse lithography technique identifies an objective function, minimizes the objective function in relation to a simulation of the optical lithographic process, such that the transmission value, which is greater than 6%, may be determined.

1 . A computer implemented method for generating photolithographic mask data comprising:
 identifying a target image, the target image corresponding to an image to be printed onto a substrate through an optical lithographic process;   generating by a computer a set of mask data having a plurality of pixels;   simulating on a computer an intensity on a substrate generated by employment of the set of mask data in the optical lithographic process;   identifying an objective function that compares the simulation of the intensity to an ideal image intensity corresponding to the target image;   minimizing by a computer the objective function to determine a transmission value for the plurality of pixels, wherein ones of the plurality of pixels have a determined transmission value greater than 6%.   
     
     
         2 . A method for generating photolithographic mask data comprising:
 identifying a target image, the target image corresponding to an image to be printed onto a substrate through an optical lithographic process;   generating by a computer a set of mask data, the set of mask data including:
 a plurality of main features having a transmission value of 100%, 
 a plurality of assist features having a transmission value of 100%, and 
 a plurality of phase shift areas having a transmission value of greater than 6%; 
   simulating by a computer an intensity on a substrate generated by employment of the set of mask data in the optical lithographic process;   identifying an objective function that compares the simulation of the intensity to an ideal image intensity corresponding to the target image;   minimizing by a computer the objective function to determine a placement for the plurality of main features in the set of mask data; and   minimizing by a computer the objective function to determine a placement for the plurality of assist features in the set of mask data.   
     
     
         3 . The computer implemented method recited in  claim 2 , further comprising
 minimizing by a computer the objective function to determine a size and/or shape for the plurality of main features in the set of mask data; and   minimizing by a computer the objective function to determine a size and/or shape for the plurality of assist features in the set of mask data.   
     
     
         4 . The method recited in  claim 3 , further comprising:
 modifying the mask data to include a plurality of patch areas having a transmission value of 0%.   
     
     
         5 . The method recited in  claim 4 , the patch areas covering the plurality of phase shift areas located at least 60 nanometers away from either a one of the plurality of main features or a one of the plurality of assist features. 
     
     
         6 . The method recited in  claim 5 , further comprising:
 manufacturing a mask, the mask corresponding to the mask data.   
     
     
         7 . The method recited in  claim 6 , the step for manufacturing a mask comprising:
 performing a first patterning operation on a lithographic mask blank, the first patterning operation causing the main features and the assist features to be formed on the lithographic mask blank; and   performing a second pattering operation on the lithographic mask blank, the second patterning operation causing the patch areas to be formed on the lithographic mask blank.   
     
     
         8 . The method recited in  claim 7 , wherein the patch areas are formed from a chromium material. 
     
     
         9 . A photolithographic mask produced according to the method recited in  claim 7 . 
     
     
         10 . The method recited in  claim 2 , further comprising:
 manufacturing a mask, the mask corresponding to the mask data.   
     
     
         11 . The method recited in  claim 10 , the step for manufacturing a mask comprising:
 performing a first patterning operation on a lithographic mask blank, the first patterning operation causing the main features and the assist features to be formed on the lithographic mask blank.   
     
     
         12 . A photolithographic mask produced according to the method recited in  claim 11 . 
     
     
         13 . The computer implemented method recited in  claim 2 , the plurality of phase shift area transmission values being within the range of 7% to 35%. 
     
     
         14 . The computer implemented method recited in  claim 2 , the plurality of phase shift area transmission values being approximately 30%. 
     
     
         15 . A computer program product for enabling a computer to alter a portion of a layout design comprising:
 software instructions for enabling a computer to perform a set of predetermined operations; and   a computer readable storage medium bearing the software instructions;   the set of predetermined operations including:
 identifying a target image, the target image corresponding to an image to be printed onto a substrate through an optical lithographic process; 
 generating a set of mask data, the set of mask data including:
 a plurality of main features having a transmission value of 100%, 
 a plurality of assist features having a transmission value of 100%, and 
 a plurality of phase shift areas having a transmission value of greater than 6%; 
 
 simulating an intensity on a substrate generated by employment of the set of mask data in the optical lithographic process; 
 identifying an objective function that compares the simulation of the intensity to an ideal image intensity corresponding to the target image; 
 minimizing the objective function to determine a placement for the plurality of main features in the set of mask data 
 minimizing the objective function to determine a placement for the plurality of assist features in the set of mask data; and 
 saving the mask data to a memory storage location. 
   
     
     
         16 . The computer program product recited in  claim 15 , the set of predetermined operation further including:
 minimizing the objective function to determine a size and/or shape for the plurality of main features in the set of mask data.   minimizing the objective function to determine a size and/or shape for the plurality of assist features in the set of mask data.   
     
     
         17 . The computer program product recited in  claim 16 , the set of predetermined operations further including:
 modifying the mask data to include a plurality of patch areas having a transmission value of 0%.   
     
     
         18 . The computer program product recited in  claim 17 , the patch areas covering the plurality of phase shift areas located at least 60 nanometers away from either a one of the plurality of features or a one of the plurality of assist features. 
     
     
         19 . The computer program product recited in  claim 15 , the plurality of phase shift area transmission values being within the range of 7% to 35%. 
     
     
         20 . The computer program product recited in  claim 15 , the plurality of phase shift area transmission values being approximately 30%.