Opc simulation model using socs decomposition of edge fragments

Abstract

A system for estimating image intensity within a window area of a wafer using a SOCS decomposition to determine the horizontal and vertical edge fragments that correspond to objects within the window area. Results of the decomposition are used to access lookup tables that store data related to the contribution of the edge fragment to the image intensity. Each lookup table stores data that are computed under a different illumination and feature fabrication or placement conditions.

1 . A method for evaluating the image intensity formed in the image plane of a photolithographic imaging system, comprising:
 receiving at least a portion of a layout file that defines features corresponding to one or more objects to be created in a microdevice;   dividing the layout file received into a number of windows of relevance that include one or more features or portions thereof;   for each window of relevance:
 decomposing the features or portions thereof in the window of relevance into a number of areas; and 
 retrieving data from a set of lookup tables associated with each area, wherein the data stored in the area lookup tables is related to the each area's contribution to the image intensity within the window of relevance; 
 decomposing the features or portions thereof in the window of relevance into a number of edges; 
 retrieving data from a set of lookup tables associated with each of the edges, wherein the data stored in the set of edge lookup tables is related to each edge's contribution to the image intensity within the window of relevance; and 
 combining the data from the lookup tables to compute the image intensity within the window of relevance due to the area of the features or portions thereof in the window of relevance and due to the edges of the features or portions thereof in the window of relevance. 
   
   
   
       2 . The method of  claim 1 , wherein the data in the lookup tables associated with the area and edges of the features or portions thereof in the window of relevance are calculated under different and independent illumination conditions. 
   
   
       3 . The method of  claim 2 , wherein the different and independent illumination conditions assume linear polarized light that is oriented in orthogonal directions. 
   
   
       4 . The method of  claim 2 , wherein the lookup tables store data for each edge assuming an illumination light that is linearly polarized parallel to an edge. 
   
   
       5 . The method of  claim 2 , wherein the lookup tables store data for each edge assuming an illumination light that is linearly polarized perpendicular to an edge. 
   
   
       6 . The method of  claim 2 , wherein the lookup tables store data for each edge that is calculated taking into account the position of the edge with respect to a corresponding feature or portion thereof. 
   
   
       7 . The method of  claim 1 , wherein the lookup tables store data for each edge taking into account how the corresponding feature or portion thereof will be created on a mask. 
   
   
       8 . The method of  claim 1 , wherein each tables associated with the areas and edges of the features or portions thereof is computed with a different kernel. 
   
   
       9 . A computer readable medium containing a plurality of lookup tables for use in a SOCS algorithm, including a plurality of lookup tables having data associated with areas in a window of relevance that relate the area's contribution to an image intensity within the window of relevance, and a plurality of lookup tables having data associated with the position of a number of edges within the window of relevance that relate each edge's contribution to the image intensity within the window of relevance. 
   
   
       10 . The computer readable medium of  claim 9 , wherein the data in each of the lookup tables is computed assuming different and independent illumination conditions. 
   
   
       11 . The computer readable medium of  claim 10 , wherein the different and independent illumination conditions assumes linearly polarized light that is oriented in orthogonal directions. 
   
   
       12 . The computer readable medium of  claim 10 , wherein the different and independent illumination conditions takes into considerations each edge's position with respect to a feature or portion thereof in the window of relevance. 
   
   
       13 . In a method for use in optical proximity correction in mask design, a method for simulating light scattering in openings in the mask comprising the steps of:
 a) defining openings in the mask by edges;   b) simulating light scattering by the edges, and   c) summing the simulated light scattering by the edges to simulate light scattering in mask openings, the improvement comprising:   storing precomputed data in lookup tables associated with the edges, wherein the data is calculated assuming a variety of independent illumination and polarization conditions.   
   
   
       14 . In a method for use in inspecting photomasks, a method for simulating light scattering in openings in the mask comprising the steps of:
 a) defining openings in the mask by edges;   b) simulating light scattering by the edges, and   c) summing the simulated light scattering by the edges to simulate light scattering in mask openings, the improvement comprising:   storing precomputed data in lookup tables associated with the edges, wherein the data is calculated assuming a variety of independent illumination and polarization conditions.   
   
   
       15 . A method for correcting a microdevice layout for processing effects, comprising:
 simulating the intensity of the image of at least a portion of a photomask under predetermined conditions of illumination angle and polarization;   storing the simulation results in a lookup table;   accessing a layout for a layer of a microdevice;   dividing the features within layout into edges;   determining which entries in the lookup table correspond to the edges in the layout;   creating an image by summing the entries stored in the lookup that correspond to the edges in the layout;   using the resulting image to compute an edge placement error that will occur when in the image is printed by a lithographic system;   altering the layout file to reduce the edge placement error, and outputting the altered layout file.   
   
   
       16 . A method of preparing layout data for the application of one or more RETs, comprising:
 determining the image intensity at a point on a wafer due to the illumination of a feature on a mask; and   adjusting the image intensity for a number of edges of the feature using a SOCS algorithm.   
   
   
       17 . The method of  claim 15 , wherein:
 the SOCS algorithm adjusts the image intensity for a number of edges by accessing a number of tables having precomputed data therein that relate to the image intensity contributed by each edge, wherein each table has data computed under different illumination conditions.