Method and apparatus for a diffusion bridged cell library

Abstract

A library of cells for designing an integrated circuit, the library comprises continuous diffusion compatible (CDC) cells. A CDC cell includes a p-doped diffusion region electrically connected to a supply rail and continuous from the left edge to the right edge of the CDC cell; a first polysilicon gate disposed above the p-doped diffusion region and electrically connected to the p-doped diffusion region; an n-doped diffusion region electrically connected to a ground rail and continuous from the left edge to the right edge; a second polysilicon gate disposed above the n-doped diffusion region and electrically connected to the n-doped diffusion region; a left floating polysilicon gate disposed over the p-doped and n-doped diffusion regions and proximal to the left edge; and a right floating polysilicon gate disposed over the p-doped and n-doped diffusion regions and proximal to the right edge.

What is claimed is: 
     
         1 . A method to bridge together cells in an integrated circuit, the method comprising:
 adding a marker layer to each edge of a cell;   for each marker shape touching two diffusion edges, growing a shortest diffusion edge of the two diffusion edges touched by the each marker shape, wherein the growth is a width of the each marker shape;   applying a Boolean AND to grown diffusion edges and marker shapes to define new diffusion regions;   growing each new diffusion region to have a polysilicon pitch of the integrated circuit; and   growing each floating gate proximal to a grown new diffusion region.   
     
     
         2 . The method of  claim 1 , wherein growing each floating gate proximal to a grown new diffusion region includes growing the each floating gate under the grown new diffusion region. 
     
     
         3 . A method to bridge together cells in an integrated circuit, the method comprising:
 during post placement of cells in a design, inserting continuous diffusion compatible (CDC) filler cells in the design;   grouping and ordering cells on a placement row to form a list of cells; and   traversing the list of cells in order, wherein
 if a cell in the list of cells is a CDC cell and a neighboring cell of the cell is a CDC cell, the cell and its neighboring cell each comprising diffusion regions, then creating a bridge cell at an edge of the cell to overlap the cell and its neighboring cell so as to electrically connect together the diffusion regions of the cell and its neighboring cell. 
   
     
     
         4 . The method of  claim 3 , further comprising:
 if a second cell in the list of cells is a filler cell and a neighboring cell of the second cell is a CDC cell, the second cell and its neighboring cell each comprising diffusion regions, then replacing the filler cell with a filler cell having a diffusion profile that provides the neighboring cell of the second cell with improved performance and creating a bridge cell at an edge of the second cell to overlap the second cell and its neighboring cell so as to electrically connect together the diffusion regions of the second cell and its neighboring cell.   
     
     
         5 . A method to generate filler cells in an integrated circuit, the method comprising:
 adding a first set of placement constraints in a design, the first set of placement constraints to enforce minimum spacing between continuous diffusion compatible (CDC) cells and non-CDC cells;   selecting and inserting end cap cells to terminate voids between CDC and non-CDC cells in the design due to the minimum spacing; and   creating filler cells where there are placement voids between CDC cells on a placement row in the design.   
     
     
         6 . The method of  claim 5 , further comprising:
 adding a second set of placement constraints to provide placement constraints in addition to the first set of placement constraints, the second set of placement constraints to prevent a first type of cell in the design from abutting a second type of cell in the design; and   selecting and inserting dual end cap cells to terminate voids between incompatible CDC cells in the design.