US 7,890,906 B2Granted

Method of laying out integrated circuit design based on known polysilicon perimeter densities of individual cells

AssigneeInternational Business Machines Corporation

InventorsLaura S. Chadwick, James A. Culp, David J. Hathaway, Anthony D. Polson

Life of this patent

Estimating the term…

Loading patent…

Abstract

Disclosed is a method of laying out individual cells of an integrated circuit design, based at least in part on the known polysilicon perimeter densities of those cells. That is, the method embodiments use the knowledge of polysilicon perimeter density for known cells to drive placement of those cells on a chip (i.e., to drive floor-planning). The method embodiments can be used to achieve approximately uniform across-chip polysilicon perimeter density and, thereby to limit performance parameter variations between functional devices that are attributable to variations in polysilicon perimeter density. Alternatively, the method embodiments can be used to selectively control variations in the average polysilicon perimeter density of different regions of a chip and, thereby to selectively control certain performance parameter variations between functional devices located in those different regions.

Claims16

Dependent claims

A method of forming an integrated circuit, said method comprising:

providing a library of predefined cells with known polysilicon perimeter densities, said providing of said library comprising determining a polysilicon perimeter density for each predefined cell by dividing a sum of the perimeter of all polysilicon shapes in said predefined cell by the area of said cell;
receiving a design for said integrated circuit;
selecting, from said library, cells required to form said integrated circuit according to said design;
and
determining locations on a chip for said cells and placing said cells in said locations to form said integrated circuit, said determining of said locations and said placing of said cells in said locations being performed based at least in part on said known polysilicon perimeter densities in order to achieve one of approximately uniform across-chip polysilicon perimeter density and selectively controlled across-chip polysilicon perimeter density variations;
said determining of said locations on said chip and said placing of said cells in said locations to achieve said approximately uniform across-chip polysilicon perimeter density comprising distributing cells having relatively high polysilicon perimeter densities approximately evenly across said chip.

3 more elements

A method of forming an integrated circuit, said method comprising:

providing a library with sets of predefined cells, each set comprising predefined cells having a same function but different polysilicon perimeter densities, said providing of said library comprising determining a polysilicon perimeter density for each predefined cell in each set by dividing a sum of the perimeter of all polysilicon shapes in said predefined cell by the area of said cell;
receiving a design for said integrated circuit;
determining, based on a predetermined criteria, a mapping order for cells required to form said integrated circuit according to said design;
according to said mapping order, for each cell required to form said integrated circuit according to said design, mapping said cells on a chip such that, when said cells are subsequently placed on said chip to form said integrated circuit, polysilicon perimeter density across said chip is approximately uniform, said mapping comprising, for each cell:
determining a current average polysilicon perimeter density on said chip;
comparing said current average polysilicon perimeter density of said chip to a target average polysilicon perimeter density;
and
selecting for said cell a predefined cell from one of said sets in said library, wherein said selecting is based at least in part on a known polysilicon perimeter density of said predefined cell in order to adjust said current average polysilicon perimeter density towards said target average perimeter density;
and
based on said mapping, placing selected predefined cells on said chip to form said integrated circuit.

7 more elements

A method of forming an integrated circuit, said method comprising:

providing a library of predefined cells with known polysilicon perimeter densities, said providing of said library comprising determining a polysilicon perimeter density for each predefined cell by dividing a sum of the perimeter of all polysilicon shapes in said predefined cell by the area of said cell;
receiving a design for said integrated circuit;
selecting, from said library, multiple predefined cells required to form said integrated circuit according to said design;
sorting said multiple predefined cells based on relative importance of a specified performance parameter, wherein variations in said specified performance parameter are attributable to variations in polysilicon perimeter density across a chip;
and
determining locations on said chip for said multiple predefined cells and placing said multiple predefined cells on said chip to form said integrated circuit, said determining of said locations and said placing of said multiple predefined cells being performed based at least in part on said relative importance of said specified performance parameter such that predefined cells for which said specific performance parameter is of high importance are located in a first region of said chip having a first average polysilicon perimeter density and such that predefined cells for which said specific performance parameter is of low importance are located in a second region of said chip having an second average polysilicon perimeter density that is different from said first average polysilicon perimeter density.

3 more elements

Dependencies are inferred from the claim text.