Method of making routable layout pattern using congestion table
View Patent ↗A method for generating a standard cell layout pattern for standard cell placement in an integrated circuit uses a congestion map. First, congestion zones are identified in a congestion map generated by an Electronic Design Automation (EDA) application. Next, routing tracks data corresponding to bounding boxes belonging to the congestion zones are used to calculate values of average vertical and horizontal congestion. Subsequently, a value of modified standard cell density is calculated based on the values of average vertical and horizontal congestion, and an unmodified standard cell density. The dimensions of a layout pattern unit are calculated using the value of the modified standard cell density and the width of standard cells. Various layout pattern units then are placed adjacent to one another to form a standard cell layout pattern.
1. A method for generating a standard cell layout pattern for standard cell placement in an integrated circuit, comprising:
identifying one or more congestion zones in a congestion map, wherein the congestion map is generated by an Electronic Design Automation (EDA) tool and includes a plurality of bounding boxes, and wherein the EDA tool generates routing tracks data corresponding to each bounding box;
calculating values of an average vertical congestion (H) and an average horizontal congestion (V) corresponding to each of the identified congestion zones using the routing tracks data;
calculating a value of a modified standard cell density for at least one of the identified congestion zones using the values of the average vertical congestion (V), the average horizontal congestion (H), and an unmodified standard cell density (D 0 ), wherein calculation of the modified standard cell density (D mod ) is mathematically represented as D mod =D 0 /H×V, and wherein the unmodified standard cell density is generated by the EDA application;
calculating dimensions of a layout pattern unit, wherein the layout pattern unit comprises a keep-out region and a placement region, wherein one or more standard cells are placed in the placement region, and wherein the keep-out region comprises one or more routing tracks; and
arranging one or more layout pattern units to form the standard cell layout pattern, wherein at least one routing track in a keep-out region of a first layout pattern unit overlaps with at least one routing track in a keep-out region of a second layout pattern unit.
2. The method for generating a standard cell layout pattern of claim 1 , wherein the routing tracks data comprises a count of horizontal routing tracks and vertical routing tracks available for routing one or more nets corresponding to each bounding box.
3. The method for generating a standard cell layout pattern of claim 2 , wherein the routing tracks data further comprises a count of horizontal routing tracks and vertical routing tracks required for routing the one or more nets corresponding to each bounding box.
4. The method for generating a standard cell layout pattern of claim 3 , wherein the value of the average vertical congestion is the arithmetic mean of ratios of a sum of the count of vertical routing tracks required and the count of vertical routing tracks available to the count of vertical routing tracks available corresponding to the bounding boxes of the one or more congestion zones.
5. The method for generating a standard cell layout pattern of claim 4 , wherein the value of the average horizontal congestion is the arithmetic mean of ratios of a sum of the count of horizontal routing tracks required and the count of horizontal routing tracks available to the count of horizontal routing tracks available corresponding to the bounding boxes of the one or more congestion zones.
6. The method for generating a standard cell layout pattern of claim 5 , wherein the modified standard cell density is a ratio of the unmodified standard cell density to a product of the average horizontal congestion and the average vertical congestion.
7. The method for generating a standard cell layout pattern of claim 1 , wherein the dimensions of the layout pattern unit comprise a length of the keep-out region and a length of the placement region.
8. The method for generating a standard cell layout pattern of claim 1 , wherein a bounding box comprises a portion of a congestion zone having a predetermined length and a predetermined width.
9. The method for generating a standard cell layout pattern of claim 1 , wherein the routing tracks data used to calculate the average vertical and horizontal congestion values corresponds to the bounding boxes of the identified congestion zones.