Abstract:
A method for automatic wire size modification comprising the steps of routing a wire to a source; detecting a first size differential between the wire and the source by calculating a width difference between a width of the wire and a width of the source, and dividing the width difference by the width of the wire; and modifying a size of the wire if the first size differential is less than a maximum width percentage and if a length of the source is less than a length range specified by a user.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   The present application is related to concurrently filed, co-pending, and commonly assigned U.S. patent application entitled SYSTEM AND METHOD FOR AUTO-ROUTING JOG ELIMINATION, the disclosure of which is hereby incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a system and method for designing and fabricating circuits. Specifically, the present invention relates to a system and method for automatically modifying wire sizes to, for example, eliminate undesirable edges or “jogs” in a wiring tool. 
   2. Description of Background 
   The process of designing and fabricating a circuit, e.g., with the use of a circuit mask design editor, may include the use of an auto wiring tool. The auto wiring tool fabricates wires using the input design and rules based on the technology being employed and the physical demands placed on the circuit. For example, a rule that may be employed during the fabrication process is a minimum feature distance requirement which ensures that every wire and source is wide enough to function properly. Those of ordinary skill in the art will appreciate that the wiring tool may be automated as well as manually operated. 
   Many times the wires created with a wiring tool include edges or jogs. A jog is an edge that is shorter than the minimum width of the metal used to make the wire. Often times, jogs create unnecessary edges or corners, that can be detrimental to the yield of the design because they can require added mask compensation shapes which cause what is known as a blooming effect during optical proximity correction or OPC. 
   One solution for this problem is to have the user manually edit the size of the wire or resulting shape after production. Another solution is to run a wire straightening program after the wires and jogs are created with the auto wiring tool. This may also be applied during post processing and may be run on the entire design. It is clear that these solutions are not favorable or cost effective. The disadvantages to these solutions include the inefficiencies created by the additional post processing step and the additional costs associated with adding steps to the production process. 
   A further solution to eliminating unwanted jogs is through the use of cost analysis. A cost value is assigned to each wire placement option indicating the cost of the jog that would result in the masking process corresponding to that placement, wherein a greater cost indicates that a more undesirable jog would be created in the masking process than would be created by a placement assigned a lesser cost. The placement having the lowest cost of the plurality of possible placements is selected. This solution provides a good solution to minimizing small jogs, however, if the wire width and length is small relative to the connecting wire width, it could be beneficial and effective to extend the wire width of the routed wire to match that of the wire being routed to. 
   SUMMARY OF THE INVENTION 
   A method for automatic wire size modification, the method comprising the following steps: routing a wire to a source, where the source includes other wires, metals or vias to which the wire is routed; detecting a first size differential between the wire and the source by calculating a width difference between a width of the wire and a width of the source, and dividing the width difference the width of the wire; and modifying a size of the wire if the first size differential is less than a maximum width percentage and if a length of the source is less than a length range specified by a user. 
   It is an object of the present invention to remove and minimize unwanted jogs during the design and fabrication process of circuits. 
   The present invention is advantageous over previous solutions because small jogs are removed during auto routing thus eliminating the additional post-fabrication steps of having to correct the undesirable edges created in the process of wiring circuits with an auto routing tool. 
   An additional advantage is that the extracted simulation results will be more accurate because changes are not made post process, but rather prior to post process, thus creating more stable designs. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
       FIG. 1  illustrates an exemplary environment for managing the processes in accordance with the invention. 
       FIG. 2A  illustrates an exemplary wiring in accordance with the prior art. 
       FIG. 2B  illustrates another exemplary wiring in accordance with the prior art. 
       FIG. 3A  illustrates an exemplary wiring with an exemplary jog. 
       FIG. 3B  illustrates an exemplary wiring in accordance with one exemplary embodiment of the present invention. 
       FIG. 4A  illustrates an exemplary wiring in accordance with one exemplary embodiment of the present invention. 
       FIG. 4B  illustrates an exemplary wiring in accordance with one exemplary embodiment of the present invention. 
       FIG. 5A  illustrates an exemplary wiring with an exemplary jog. 
       FIG. 5B  illustrates an exemplary wiring in accordance with one exemplary embodiment of the present invention. 
       FIG. 5C  illustrates an exemplary wiring with an exemplary jog. 
       FIG. 5D  illustrates an exemplary wiring in accordance with one exemplary embodiment of the present invention. 
       FIG. 6A  illustrates an exemplary wiring in accordance with one exemplary embodiment of the present invention. 
       FIG. 6B  illustrates an exemplary wiring in accordance with one exemplary embodiment of the present invention. 
       FIG. 7  illustrates an exemplary jog elimination process in accordance with one exemplary embodiment of the present invention. 
   

   The detailed description explains the preferred embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
   DETAILED DESCRIPTION OF THE INVENTION 
   The invention can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment containing both hardware and software elements. In a preferred embodiment, the invention is implemented in software, which includes but is not limited to firmware, resident software, microcode, etc. Furthermore, the invention can take the form of a computer program product accessible from a computer-usable or computer-readable medium providing program code for use by or in connection with a computer or any instruction execution system. 
   With reference to the accompanying drawings,  FIG. 1  shows an illustrative environment  2  for computer user  1  to manage the processes in accordance with the invention. To this extent, the environment  2  includes a computer infrastructure  3  that can perform the processes described herein. In particular, the computer infrastructure  3  is shown including a computing device  4  operable to perform the processes described herein. The computing device  4  is shown including a processor  5 , a memory  10 , an input/output (I/O) interface  6 , and a bus  9 . Further, the computing device  4  is shown in communication with an external I/O device/resource  7  and a storage system  8 . As is known in the art, in general, the processor  5  executes computer program code, which is stored in memory  10  and/or storage system  8 . While executing computer program code, the processor  5  can read and/or write data, such as the range boundary  50 , to/from memory  10 , storage system  8 , and/or I/O interface  6 . The bus  9  provides a communications link between each of the components in the computing device  4 . The I/O device  7  can comprise any device that enables an individual to interact with the computing device  4  or any device that enables the computing device  4  to communicate with one or more other computing devices using any type of communications link. 
   The computing device  4  can comprise any general purpose computing article of manufacture capable of executing computer program code installed thereon (e.g., a personal computer, server, handheld device, etc.). However, it is understood that the computing device  4  is only representative of various possible equivalent computing devices that may perform the processes described herein. Similarly, the computer infrastructure  3  is only illustrative of various types of computer infrastructures for implementing the invention. For example, in one embodiment, the computer infrastructure  3  comprises two or more computing devices (e.g., a server cluster) that communicate over any type of communications link, such as a network, a shared memory, or the like, to perform the process described herein. 
     FIG. 2A  illustrates an exemplary wiring according to prior art. Source  20  and wires  30  represent an exemplary design input into the auto wiring tool, e.g., masking tool. It is understood by those with ordinary skill in the art that source  20  may be different components (e.g., other wires, metals or vias) of a chip for which wiring is implemented. In this example, source  20  is used to couple wires  30  to vias  22 . Resulting shape  40  is created by the auto wiring tool. Resulting shape  40  includes several jogs  42   a  and  42   b  that result from the fabrication process. Some of these jogs are undesirable because they may be detrimental to the yield of the design. 
   As shown in  FIG. 2B , if wire  30  is aligned with source  20 , then the unwanted jogs may be eliminated. For example, in  FIG. 2B , jogs  42   a  depicted in  FIG. 2A  are no longer present in resulting shape  40 . As described above, currently, a wire straightening program must be manually run after the wiring tool in order to remove unwanted jogs such as jogs  42   a.    
   One objective of auto routers is to connect two points with the shortest path possible. For example, when the auto router starts creating a wire, it is desirable for the edge of wire  30  to line up with the edge of the target source  20  of the same metal, as shown in  FIG. 3B , rather than the misalignment depicted in  FIG. 3A . The auto router will stray from the shortest path based on the costs that are implemented into the wiring algorithm. 
   In addition, when the router places via  22  to change to an adjacent metal level, it is desirable for the edges of via  22  to line up with the existing edge of the wire  30 . As mentioned above, a cost-based wire placement solution may eliminate unwanted jogs  42   a . However, if the wire width of the routed wire is not equal to, but is relatively close to, that of the wire being routed to the metal level, unwanted jogs may not be eliminated. For example, a less-than-preferred routing  300   a  is shown in  FIG. 4A , in which a wire  320   a  is routed to the center of a shape  310 . A more preferable routing  300   b  is shown in  FIG. 4B , in which the wire  320   b  is routed so as to be flush with the selected edge of the shape  310 . 
   The present invention eliminates unwanted jogs by altering the width of connecting wires. For example,  FIG. 5A  illustrates the placement of wire  30  to source  20  with an auto router. The placement of wire  30  to source  20  by the auto router creates unwanted jog  42   a . In accordance with a preferred embodiment of the present invention, the unwanted jog  42   a  is eliminated by altering the width of wire  30 .  FIG. 5B  illustrates an exemplary wiring in accordance with a preferred embodiment of the present invention. In  FIG. 5B , the width of wire  30  is altered to match the width of source  20 . 
   According to this embodiment of the invention, if the width of the wire being routed, e.g., wire  30 , is less than a predefined percentage of the width of the shape being routed to, e.g., source  20 , and the length of the wire segment being routed is less than a predefined percentage of the width of the source being routed to then the routed segment&#39;s width is extended to match the width of the source being routed to. This may be calculated, for example, by increasing the width of wire  30  if (a) the difference between the length of wire  30  and the width of source  20  divided by the width of source  20  is less than a predefined maximum length percentage; and (b) the difference between the width of source  20  and wire  30  divided by the width of source  20  is less than a predefined maximum width percentage. Exemplary pseudo code for the described algorithm may include:
     if(|(L 1 −W 2 )/W 2 |&lt;Max Length %) {
       if(|(W 2 −W 1 )/W 2 |&lt;Max Width %) {
           Remove Jogs;   
           }   else {
           Do Not Remove Jogs;   
           }   
       }   

     FIG. 6A  illustrates an exemplary embodiment indicating the variables in the above algorithm. Specifically, L 1  in the above algorithm is the length of the wire  30  being routed, and W 1  is the width of the wire  30  being routed. W 2  is the width of the source  20  to be routed. The algorithm is iterative in nature and may be integrated into the auto router such that if the algorithm fails, information may be fed back to the auto router. 
     FIG. 5C  illustrates another placement of wire  30  to source  20  with an auto router. In this example, the width of wire  30  is larger than the width of source  20 . Similar to the illustrations above, this creates an unwanted jog  42   a . In another preferred embodiment of the present invention, the jog can be removed by altering the length of wire  30 . For example, the length of wire  30  may be lengthened with the use of a metal extender. This may be calculated, for example, by increasing the length of wire  30  if (a) the difference between the width of the wire  30  and the width of source  20  divided by the width of wire  30  is less than a predefined percentage; and (b) the length of source  20  is less than a user specified range. Exemplary pseudo code for the described algorithm may include:
     if(|(W 1 −W 2 )/W 1 |&lt;Max Width %) {
       if(L 2 &lt;User Specified Length Range) {
           Remove Jogs;   
           }   else {
           Do Not Remove Jogs;   
           }   
       }   
     FIG. 6B  illustrates an exemplary embodiment indicating the variables in the above algorithm. Specifically, W 1  in the above algorithm again represents the width of the wire being routed and W 2  represents the width of the source being routed to, e.g., source  20 . L 2  is the length of the source being routed to. The algorithm above is also iterative in nature and may be integrated into the auto router such that if the algorithm fails, information may be fed back to the auto router. 
   These jog elimination algorithms may be implemented through the exemplary process illustrated in  FIG. 7 . Jog search engine  700  is a part of the wire routing process. At step  705 , it is determined whether a jog is present by using jog formulas of database  707 . If a jog is not present, the jog elimination process ends. If, on the other hand, a jog is present, the wire size is modified at step  710 . The layout of the modified wire is checked at step  715  using the layout rules in database  717 . If the layout verification step  715  is passed, the modification of the wire size is committed at step  720 . If the layout verification step  715  is failed, the last made modification is removed at step  730 . The system then checks whether there is an alternate modification available at step  735 . If there is an alternate modification available, the process returns to step  710 . If there is no alternate modification available, the system continues to step  725  and checks whether the jog elimination process is complete. If the process is complete, the jog elimination process ends. If the process is not complete, the system returns to step  705  to determine whether other jogs are present. 
   The diagrams depicted herein are just examples. There may be many variations to these diagrams or the steps (or operations) described therein without departing from the spirit of the invention. For instance, the steps may be performed in a differing order, or steps may be added, deleted or modified. All of these variations are considered a part of the claimed invention. 
   While the preferred embodiment to the invention has been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the invention first described.