Abstract:
The invention discloses a power mesh management method utilized in an integrated IC. The integrated circuit includes a macro block including at least a macro block power supplying line growing along a first direction. The management method includes: defining a plurality of first power supplying lines located in a metal layer above the macro block, wherein each of the first supplying lines grows along the first direction; defining a plurality of second power supplying lines located in another metal layer above the macro block, wherein each of the second supplying lines grows along a second direction; defining a partial power supplying line from the plurality of first power supplying lines where the partial power supplying line overlaps the macro block power supplying line; and removing the partial power supplying line from the plurality of first power supplying lines.

Description:
BACKGROUND OF THE INVENTION 
     (a) Field of the Invention 
     The invention relates to a power mesh management method, particularly to a macro block power mesh management method. 
     (b) Description of the Related Art 
     During the integrated circuit design process, the APR (automatic placement and routing) tool not only helps a circuit designer placing the circuit elements at the suitable locations in the chip easily but also helps the circuit designer managing the power routing. The APR tool has become one of the indispensable tools for the circuit designer. 
     In general, the APR tool uses two types of blocks to manage the circuit elements. One type of the blocks is the standard cell. As the name implies, the standard cell is a standardized block of specific size and fixed power management method for managing some often-used standard circuit elements, such as: flip-flops, logic gates, and the like. Then, the APR tool can neatly arrange a plurality of standard cells in areas of the chip. The other type is the macro block. A macro block is used to manage some circuit elements of specific function designed by the circuit designer, such as: SRAM, ADC, and so on. In practical applications, as is well known in the industry, the size of the macro block usually depends on the size of the circuit elements for the specific function designed by the designer. The APR tool can also arrange the macro blocks at the suitable locations of the chip automatically. 
     However, although the APR tool can follow specific routing rules to manage the suitable locations for the macro block and to draw the power mesh for the macro block. (Power mesh is usually placed in the upper metal layers of the circuit.) But, as the APR tool can only handle regular management, detailed management still needs manual adjustments by a designer. Therefore, the APR tool still needs to be improved. 
     Please refer to  FIG. 1  which shows a schematic diagram illustrating the macro block  100  managed by the APR tool according to the prior art. In this example, the macro block comprises the annular power supplying lines  110 ,  120  and the internal circuitry  130 . The annular power supplying lines  110 ,  120  are of annular structure surrounding the internal circuitry and couple to the various circuit elements of the internal circuitry  130  (not shown in  FIG. 1 ). The power supplying line  110  conducts the external power to the internal circuitry  130  through the power mesh in the upper layer (not sown in  FIG. 1 ). And, the power supplying line  120  also conducts the ground voltage to the internal circuitry  130  through the power mesh in the upper layer (not sown in  FIG. 1 ). 
     Please note that the above mentioned annular power supplying lines  110 ,  120 , including horizontal direction and vertical direction, are just one example. In practical applications, the power supplying lines of the macro block  100  can be of any shape and are not limited to the annular structure surrounding the internal circuitry  130 . 
     Then, please refer to  FIG. 2  which shows the macro block  100  of  FIG. 1  and the power mesh  200  located in a layer above the macro block  100 . As shown in  FIG. 2 , the dotted line portion indicates the macro block  100  shown in  FIG. 1  (including the annular power supplying lines  110 ,  120  and the internal circuitry  130 ) while the continuous line portion indicates the power mesh  200  managed by the APR tool in the prior art. As shown in the figure, the power mesh  200  comprises the horizontal power supplying lines  210  and the vertical power supplying lines  220 . The vertical power supplying lines  220  are located in a layer above the horizontal power supplying lines  210 . In other words, the power supplying line  110 ,  120 , the horizontal power supplying lines  210  and the vertical power supplying lines  220  are respectively located in different metal layer. The power supplying lines  210  and the power supplying lines  220  are mutually perpendicular to form a matrix. Besides, the power supplying lines  210  include a plurality of power lines  211  and ground lines  212  placed in a mutually interlaced manner while the power supplying lines  220  include a plurality of power lines  221  and ground lines  222  placed in a mutually interlaced manner. Please note that only three sets of power supplying lines  210 ,  220  are shown in the figure for convenience. In general, when there are more power supplying lines  210 ,  220 , the power meshes formed are denser too. 
     Besides, please note that the small squares  230  shown in  FIG. 2  are the via holes (“vias”)/contact and the via plugs for coupling/connecting the structures of different layers. In one embodiment of the invention, as the power lines  211 ,  221  correspond to the same electrical property, the power lines  211 ,  221  couple to each other through the vias and the via plugs  230 . On the other hand, as the ground lines  212 ,  222  also correspond to the same electrical property, the ground lines also couple to each other through the vias and the via plugs  230 . 
     As known by the industry, the power lines  211 ,  221  couple to the external power (not shown in the figure) and the above mentioned annular power supplying line  110  through the vias and the via plugs at suitable locations for conducting the voltage provided by the external power to the macro block  100 . The ground lines  212 ,  222  couple to the ground voltage and the above mentioned annular power supplying line  120  through the vias and the via plugs at suitable locations for conducting the ground voltage to the macro block  100 . 
     Please note that, since it is necessary to conduct the external power/ground voltage into the macro block  100 , the resistance between the external power and the macro block  100  is generally properly designed to obtain better overall circuit performance. The resistance between the external power and the macro block  100  is directly related to the number of the vias and via plugs. As is well known to the industry that, due to the resistance shunting effect, the more is the number of the vias the more is the reduction of the resistance between the external power and the macro block  100 . 
     Hence, the position that can be allocated for the via becomes crucial. As mentioned before, the adjustable range of the resistance becomes larger when there are more allocable positions for the via. Therefore, the routing rule of the APR tool is usually designed to place the via and the via plug for coupling at the overlapping areas of the annular power supplying lines  110 / 120  and the power supplying lines  210 / 220 , and at the overlapping areas of the power supplying line  210  and the power supplying line  220 . However, such a design will cause some problems. 
     Please refer to  FIG. 3  which shows the interconnections of the annular power supplying lines  110 ,  120  and the power mesh  200  in the layer above the annular power supplying lines  110 ,  120  through the vias and the via plugs. As shown in  FIG. 3 , the power supplying lines  210 ,  220  overlap the annular power supplying lines  110 ,  120  in areas  240  where the power supplying lines  210 ,  220  interlace the annular power supplying lines  110 ,  120  vertically. Therefore, the electrical interconnections among these are provided by the vias and the via plugs located in these vertically interlaced overlapping areas. But, as the power supplying lines  210 ,  220  in the upper layer overlap the annular power supplying lines  110 ,  120  in areas  250  where the power supplying lines  210  are parallel to the annular power supplying lines  110 ,  120 . The electrical interconnections among these become a problem. 
     Please refer to  FIG. 4  regarding the possible problems of the electrical interconnections in areas  250  among the power supplying lines  210 ,  220  and the annular power supplying lines  110 ,  120 .  FIG. 4  shows two kinds of situations that may cause problems. The first situation is indicated by the area  251 . As the power line  211  of the power mesh  200  overlaps the annular power supplying line  110  of the macro block  100  that is to be coupled in the area  251 , the via and the via plug are placed in the overlapping area to form the electrical connections. But, from the vertical cross-section point of view, the via and the via plug form a wall-like structure due to the neighboring parallel relationship. As the other metal routings of the same metal layer cannot pass through this wall-like structure, the flexibility of routing is greatly limited. The second situation is indicated by the area  252 . As the ground line  222  of the power mesh  200  overlaps the annular power supplying line  120  of the macro block  100  that is to be coupled in the area  252 , the via and the via plug are placed in the overlapping area to form electrical connections. But, the power supplying lines  211  and the annular power supplying line  120  are of different electrical potential and are in parallel overlapping relationship. The area available for the via and the via plug in the area  252  to couple the ground line  222  and the annular power supplying lines  120  becomes greatly limited. Therefore, the resistance of the power mesh cannot be reduced effectively. 
     Therefore, those who are skilled in the art must develop new routing rules and layout methods to solve the above mentioned problems. 
     BRIEF SUMMARY OF THE INVENTION 
     Therefore, one object of the invention is to provide a routing rule of the APR tool and the related integrated circuit layout method for solving the problems in the prior art. 
     A power mesh management method for placing a power mesh in an integrated circuit is provided according to one embodiment of the invention. The integrated circuit includes at least a macro block. Each macro block comprises at least a macro block power supplying line growing along a first direction. The management method defines a plurality of first power supplying lines, a plurality of second power supplying lines, and a partial power supplying line from the plurality of first power supplying lines. The first power supplying lines are located in a metal layer above the macro block. Each of the first supplying lines grows along the first direction. The second power supplying lines are located in another metal layer above the macro block. Each of the second supplying lines grows along a second direction. The partial power supplying line from the plurality of first power supplying lines overlaps the macro block power supplying line. The partial power supplying line is removed from the plurality of first power supplying lines. 
     An integrated circuit layout structure is provided according to another embodiment of the invention. The structure includes at least a macro block. Each macro block comprises at least a macro block power supplying line growing along a first direction and a power mesh located in at least a metal layer above the macro block. The power mesh electrically couples to an external power and the macro block to input the external power to the macro block for providing the power needed by the macro block. The power mesh comprises a plurality of first power supplying lines, a plurality of second power supplying lines, and a plurality of vias and via plugs. Each of the first supplying lines grows along the first direction. Each of the second supplying lines grows along the second direction. The plurality of vias and via plugs located between the macro block and the power mesh electrically couple the macro block and the power mesh. None of the first power supplying lines is placed at the position, overlapping the position of the macro block power supplying line, above the macro block power supplying line. 
     The APR tool according to the invention provides a circuit layout having an improved power mesh. The via and the via plug are prevented from forming a wall-like structure that blocks other conducting wires. On the other hand, the structure located in the upper layer of the power mesh is also prevented from blocking the structure located in the upper layer of the power mesh while coupling the macro block through the via and via plug. Therefore, the circuit design flexibility is increased. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic diagram illustrating a macro block and the related annular power supplying lines managed by the APR tool according to the prior art; 
         FIG. 2  shows a schematic diagram illustrating the macro block, the annular power supplying lines, and the power mesh above the macro block in  FIG. 1 ; 
         FIG. 3  shows a schematic diagram illustrating the macro block, the annular power supplying lines, and the power mesh above the macro block in  FIG. 1   
         FIG. 4  shows an enlarged schematic diagram illustrating an area in  FIG. 3 ; 
         FIG. 5  shows a schematic diagram illustrating a macro block and the related power mesh managed by the APR tool according to a first embodiment of the invention; 
         FIG. 6  shows a flow chart illustrating the steps executed by the APR tool according to one embodiment of the invention; 
         FIG. 7  shows a schematic diagram illustrating a macro block and the related power mesh managed by the APR tool according to a second embodiment of the invention; and 
         FIG. 8  shows a flow chart illustrating the steps executed by the APR tool according to the another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Please refer to  FIG. 5  which shows a schematic diagram illustrating the macro block and the related power mesh managed by the APR tool according to the first embodiment of the invention. Please note that the macro block  100 , the related annular power supplying lines  110 ,  120 , and the internal circuitry  130  shown in  FIG. 5  are exactly the same as the above mentioned macro block  100 , the related annular power supplying lines  110 ,  120 , and the internal circuitry  130 . The power lines  511 ,  521  and the ground lines  512 ,  522  also have the same functions as the above mentioned power lines  211 ,  221  and the ground lines  212 ,  222 . But, the structure of the power mesh  500  is different from the above mentioned power mesh  200 . Although the SRAM memory unit is taken as an example of the macro block  100  according to the embodiment of the invention, those who are skilled in the art should be able to understand that the invention is not limited by these examples. Any common or newly developed circuit element can be configured as the macro block  100  and is to be encompassed by the scope of the present invention. 
     As shown in  FIG. 5 , the power mesh  500  includes the horizontal power supplying line  510  and the vertical power supplying line  520  where the vertical power supplying line  520  is located in the layer above the horizontal power supplying line  510 . However, please note that the power mesh  500  and the annular power supplying lines  110 ,  120  do not have any overlapping portion that is growing along corresponding to the same direction (that is neighboring in parallel). Therefore, in the embodiments according to the invention, the situation of forming a wall-like structure by the vias or blocking the vias from coupling to the annular power supplying lines  110 / 120  in the prior art will not happen. 
     Please refer to  FIG. 6  and  FIG. 5 .  FIG. 6  shows the flow chart illustrating the steps executed by the APR tool according to one embodiment of the invention. The method comprises the following steps: 
     Step  600 : defining at least a macro block  100  that comprises the power supplying lines  110 ,  120  and the internal circuitry  130 ; 
     Step  602 : defining a power mesh in the layer above the macro block that includes a structure growing along the vertical direction and a structure growing along the horizontal direction that are placed in different metal layers; 
     Step  604 : removing the partial power supplying line of the power mesh that is growing along the same corresponding direction (or corresponding to the same direction) and overlaps with the power supplying line of the macro block to define a corrected power mesh; and 
     Step  606 : coupling the corrected power mesh to the power supplying line of the macro block. The coupling step is completed by forming the via and the via plug in the overlapping area where the corrected power mesh vertically intersects with the power supplying line of the macro block according to one embodiment of the invention. 
     At first, the APR tool according to the invention allocates the macro block  100  at the suitable location on the chip (Step  600 ). The internal circuitry  130  of the macro block  100  couples to the related annular power supplying lines  110 / 120  properly for conducting the external power into the internal circuitry  130  through the annular power supplying lines  110 / 120 . Please note that the shape of the annular power supplying lines  110 / 120  is just one of the examples according to the invention and should not be construed as any limitation on the range of implementation of the invention. In practical applications, the power supplying line of the macro block  100  can be of any shape distributed around or within the macro block  100  and is not limited to the annular shape. 
     Then, the APR tool according to the invention defines a power mesh in the layer above the macro block  100  (Step  602 ). Please note that the power mesh defined by the APR tool in this step is just the above mentioned power mesh  200 . The power mesh  500  shown in  FIG. 5  is not yet defined. 
     Next, the APR tool according to the invention defines the portion of the power mesh  530  that is growing along the same corresponding direction as that for the power supplying lines  110 ,  120  and also overlaps the power supplying lines  110 ,  120  in the lower layer. The APR tool then removes such a portion (Step  604 ) to define a corrected power mesh. Please refer to  FIG. 2  and  FIG. 5 . As shown in the power mesh  200  of  FIG. 2 , the portion of the power supplying line  210 , that is growing along the same corresponding direction as the direction of the annular power supplying line and also overlaps the annular power supplying line in lower the layer, also causes the above mentioned problem. Therefore, removing the overlapping portion as shown in  FIG. 5  avoids the problems in the prior art. After removing the overlapping portion, it becomes the corrected power mesh  500  shown in  FIG. 5 . 
     Finally, the APR tool according to the invention utilizes the via and the via plug  530  to couple the power mesh  500  and the annular power supplying lines  110 ,  120  (Step  606 ) together. Then, the power needed by the macro block  100  can be conducted into the macro block through the power mesh  500  and the annular power supplying line  110 . Please note that, since the overall structure of the power mesh  500  has been completed based on the technical content disclosed up to now, it is not difficult to do the placement of the via and the via plug  530  by those who are skilled in the art and thus the details will not be repeated hereinafter. 
     Please note that only examples of the horizontal power supplying line  510  having the portion overlapping the annular power supplying line below are disclosed in the above. Therefore, the disclosure only teaches the removal of the overlapping portion of the horizontal power supplying line  510 . But, in practical applications, the vertical power supplying line  520  can also overlap the annular power supplying line below. In one preferred embodiment of the invention, in order to prevent the vertical power supplying line  520  and the annular power supplying line below from forming the wall-like vias, the portion of the vertical power supplying line  520  overlapping the annular power supplying line below is also removed. Such equivalent changes are foreseeable by those who are skilled in the art and the details will not be repeated hereinafter. 
     Please refer to  FIG.7  which shows a schematic diagram illustrating a macro block and the related power mesh managed by the APR tool according to the second embodiment of the invention. Similarly, the macro block  100 , the related annular power supplying lines  110 ,  120 , and the internal circuitry  130  shown in  FIG. 7  have the same functions as the macro block  100 , the related annular power supplying lines  110 ,  120 , and the internal circuitry  130  shown in  FIG. 1  and operate in the same manner. The power lines  711 ,  721  and the ground lines  712 ,  722  also have the same functions as the power lines  211 ,  221  and the ground lines  212 ,  222  mentioned before. But, please note that the structure of the power mesh  700  is different from the above mentioned power mesh  200 . 
     As shown in  FIG. 7 , the power mesh  700  also includes the horizontal power supplying line  710  and the vertical power supplying line  720 . The vertical power supplying line  720  is located in the layer above the horizontal power supplying line  710 . However, please note that the power mesh  700  and the annular power supplying lines  110 ,  120  do not have any overlapping portion that is growing along the same corresponding direction (that is neighboring in parallel) (as shown in the figure, the portion that was overlapping is shifted to other locations). Therefore, in the embodiments according to the invention, the situation of forming a wall-like structure by the via or blocking the via from coupling to the annular power supplying lines  110 / 120  in the prior art will not happen. 
     Please refer to  FIG. 8  and  FIG. 7 .  FIG. 8  shows the flow chart illustrating the steps executed by the APR tool according to another embodiment of the invention. The method comprises the following steps: 
     Step  800 : defining at least a macro block  100  that comprises the power supplying lines  110 ,  120  and the internal circuitry  130 ; 
     Step  802 : defining a power mesh in the layer above the macro block that includes a structure along the vertical direction and a structure along the horizontal direction that are placed in different metal layers; 
     Step  804 : shifting the partial power supplying line of the power mesh that is growing along the same corresponding direction as the direction of the power supplying line of the macro block and also overlaps with the power supplying line of the macro block so that the partial power supplying line no longer overlaps with the power supplying line of the macro block below along neighboring parallel direction so as to define a corrected power mesh; and 
     Step  806 : coupling the corrected power mesh to the power supplying line of the macro block by way of the via and the via plug that are formed in the overlapping area where the corrected power mesh vertically intersects with the power supplying line of the macro block according to one embodiment of the invention. 
     Please note that the steps  800 ,  802 ,  806  are the same as the steps  600 ,  602 ,  606  and the details will not be repeated hereinafter. However, the step  804  according to this embodiment of the invention is different from the step  604  mentioned before. Please note that in the step  804 , the APR tool according to the invention uses the practice of shifting the partial power supplying line to replace the practice of removing the partial power supplying line as mentioned before. The benefit is that, after shifting, there are still opportunities for the shifted partial power supplying line to couple to the annular power connecting line below in the vertically intersecting overlapping area (such as the area  731  shown in  FIG. 7 ). Therefore, the flexibility of managing the vias is increased and the resistance can be reduced as much as possible. The problem of blocking the vias or forming a wall-like structure by the vias in the prior art will not happen, either. 
     Similarly, as shown in  FIG. 7 , since only the horizontal power supplying line  710  has the portion that overlaps with the annular power supplying line below, only the overlapping portion of the horizontal power supplying line  710  is removed. But, in practical applications, the vertical power supplying line  720  may also include the portion that overlaps with the annular power supplying line below. In one preferred embodiment of the invention, to prevent the vertical power supplying line  720  and the annular power supplying line below from forming the wall-like vias, the portion of the vertical power supplying line  720  that overlaps with the annular power supplying line below is also shifted to other location. Although, as shown in  FIG. 7 , one of the two power supplying lines is shifted upward and the other one is shifted downward, the invention is not limited by these examples. In other embodiments of the invention, even if both of the two power supplying lines are shifted upward or downward, it is still encompassed by the scope of the present invention. 
     Those who are skilled in the art should be able to understand the content disclosed up to now and the APR tool according to the invention can be developed. The step that removes or shifts the neighboring parallel area of the power supplying line is taken as an example. As is well known by those who are skilled in the design of APR process flow, the portion to be removed or the position to be shifted can be determined by marking coordinates. Therefore, the details of the program code of the APR tool will not be repeated hereinafter. Besides, although the APR tool is used as an example of the circuit layout tool in the above mentioned disclosure, the invention is not limited by this example. For instance, those who are skilled in the art can use various methods to manage the above mentioned circuit layout. But, no matter whether APR tool or manual practice is used to execute the above mentioned managing steps or to draw the above mentioned circuit layout, such equivalent changes are still encompassed by the scope of the present invention. 
     In other words, if a circuit layout comprises a macro block having power supplying lines and a power mesh in the upper layer. The power mesh of the circuit layout is a uniformly distributed power mesh. The portion of the power mesh that is growing along the same corresponding direction as the direction of the power supplying line of the macro block and also overlaps with the power supplying line of the macro block is either removed or shifted. Then, such a circuit layout is to be encompassed by the scope of the present invention. 
     Please note that, the purpose of showing only 3˜4 sets of power supplying lines (including the ground lines and the power lines) in the power meshes in  FIG. 5  and  FIG. 7  is only to facilitate the clarity of description. In practical applications, the power meshes  500 ,  700  in the layer above the macro block can be of much denser power meshes. 
     Compared to the prior art, the APR tool according to the invention provides better circuit layout to prevent the via from forming the wall-like structure and thereby avoiding the wall-like structure from blocking other conducting lines. Therefore, the embodiments according to the invention can increase the flexibility of circuit design. 
     Although the present invention has been fully described by way of above-mentioned examples of embodiment, however, it should not be construed as any limitation on the scope of the invention. Various modifications or changes can be performed by those who are skilled in the art without deviating from the scope of the invention.