Model-Based Fill

Abstract

Various aspects of this disclosure relate to increasing pattern density in a circuit layout design of a circuit layer so as to control the thickness of material in a manufactured integrated circuit. For example, a layer in circuit design may be divided into separate areas, and a target thickness range may be established for all of the tiles in the integrated circuit design. Each area may be analyzed to determine if it has a sufficient pattern density for a thickness estimation model to accurately estimate its expected material thickness upon manufacture. Each tile may be analyzed to determine if the expected thickness for that tile is within the target thickness range.

1 . A method of adding fill pattern density to an integrated circuit design for controlling a variation in a thickness of material over a surface of an integrated circuit manufactured from the integrated circuit design, comprising:
 determining if a window of an integrated circuit design complies with one or more specified thickness-related criteria, and   if the window does not comply with the specified pattern density criteria, then   (a) selecting a fill pattern shape from a plurality of fill pattern shapes,   (b) determining an amount of the selected fill pattern shapes to be added to the window for the window to have a potential pattern density greater than a target pattern density,   (c) determining a potential pattern perimeter-to-area ratio for the window if the amount of the selected fill pattern shapes is added to the window, and   (d) determining an expected material thickness for the portion of the integrated circuit design based upon the potential pattern density and the potential pattern perimeter-to-area ratio;   repeating steps (a) through (d) until a successful fill shape is selected that provides an expected material thickness for the window that is above a target material thickness; and   adding the amount of the successful selected fill shape that provides an expected material thickness above the specified material thickness to the window.   
     
     
         2 . The method recited in  claim 1 , wherein determining the expected material thickness for the portion of the integrated circuit design based upon the determined window pattern perimeter-to-area ratio includes employing a look up table. 
     
     
         3 . The method recited in  claim 1 , wherein the one or more specified pattern density criteria includes at least one of:
 a window pattern density above a specified pattern density, and   
       a window pattern perimeter-to-area ratio above a specified pattern perimeter-to-area. 
     
     
         4 . The method recited in  claim 1 , further comprising:
 if, in step (b), an amount of the selected fill pattern shapes to be added to the window for the window to have a potential pattern density greater than a target pattern density cannot be determined, then repeating steps (a) through (d) with a different selected fill shape.