Abstract:
The invention discloses a technique for designing the power layout of an integrated circuit. The power layout design forms a power mesh and a power ring with a plurality of metal trunks with uniform line width. In particular, the power ring includes a plurality of metal rings, which are formed by arranging denser layout of the metal trunks with uniform line width. The power ring serves as a function of receiving and providing a power source to the elements of the integrated circuit.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a power layout design of an integrated circuit (IC), and more particularly, to a layout design of a power mesh and a power ring in an integrated circuit. 
     2. Description of the Prior Art 
     Please refer to  FIG. 1A .  FIG. 1A  shows a simplified sectional view of a conventional IC die (or a chip)  1 . As shown in  FIG. 1A , the IC die  1  includes a semiconductor layer  10 , six successive metal layers ( 121 ˜ 126 ) from bottom to top, several insulating layers  14  formed between two adjacent metal layers respectively, and a passivation layer  16 . The semiconductor layer  10  is used for forming electronic components such as transistors (not shown in  FIG. 1A ) and electrical routing among these electronic components. In order to achieve the minimal chip area and the fastest circuit rate, generally, only shorter electrical connections are formed on the semiconductor layer  10 . The metal layers  121 ˜ 126  are provided for other electrical connections. The number of the metal layers is determined by the complication of the practical routing. For example, eight or even more metal layers are widely used for IC design with complicated routing. 
     Regarding the routing at the metal layers  121 ˜ 126 , a power distribution network (not shown in  FIG. 1A ) can be formed at the first metal layer  121  and coupled to the electronic components. The power distribution network may be made of metal rails with finer line widths. 
     Please refer to  FIG. 1B .  FIG. 1B  shows the higher metal layers of the IC die  1  and the routing formed thereon. 
     As shown in  FIG. 1B , a power mesh  18  is formed at the sixth metal layer  126  and the fifth metal layer  125 . The power mesh  18  includes metal trunks  182  and  184  with line widths wider than the metal rail. In addition, the metal trunks  182  and  184  formed at different metal layers  125  and  126  are interconnected by a via  142  formed at the insulating layer  14 . In the same way, the power mesh  18  is connected to the power distribution network by the via  142 . The metal trunks  182  and  184  are divided into a power metal trunk  182  for connecting power and a ground metal trunk  184  for connecting ground. At the same metal layer, the power metal trunk  182  and the ground metal trunk  184  are interlaced. The metal trunks  182  and  184  formed at the sixth metal layer  126  are perpendicular to those formed at the fifth metal layer  125 . The metal trunks  182  formed at the sixth metal layer  126  are only connected to the metal trunks  182  formed at the fifth metal layer  125 , and the metal trunks  184  formed at the sixth metal layer  126  are only connected to the metal trunks  184  formed at the fifth metal layer  125 . 
     Please refer to  FIG. 1B  again. A power supply ring  17  (a small section of the power supply ring  17  is shown in  FIG. 1B ) can be formed at the sixth metal layer  126 . In practical applications, the power supply ring  17  consists of two metal rings  172  and  174  with line widths larger than the metal trunk  182  and  184 . The two metal rings  172  and  174  are divided into a power metal ring  172  for connecting power and a ground metal ring  174  for connecting ground. The metal rings  172  and  174  are formed at the sixth metal layer  126 , and the metal rings  172  and  174  surround the metal trunks  182  and  184  which are also formed at the sixth metal layer  126  to form a ring structure (not shown in  FIG. 1B ). The power supply ring  17  is used for receiving a power and conducting the power to the power distribution network through the power mesh  18 . The power distribution network is used for distributing the power to the electronic components. 
     When designing an IC, in order to provide well-planned power structures, it is necessary to collect a variety of specifications to match various requirements of the manufacturing process, the yield, and the occupied resource. Because a lot of details are requested, the power structures must be planned and accomplished by experienced layout engineers. As a result, a huge human resource burden is induced. 
     SUMMARY OF THE INVENTION 
     Therefore, a scope of the invention is to provide a power layout of an integrated circuit die (or a chip) and the designing method thereof. In the IC die, a power mesh and a power supply ring are integrated, and more particularly, the impedance difference between the power mesh and the power supply ring can be reduced. The routing congestion of the power mesh and the power supply ring can be effectively eased off. 
     A preferred embodiment according to the invention is an IC die. The IC die includes a semiconductor layer, a plurality of electronic components formed on the semiconductor layer, N successive metal layers from bottom to top, a power distribution network, a power mesh, and a power supply ring. Each of the N metal layers is isolated and formed over the semiconductor layer, wherein N is a positive integer. A power distribution network includes a plurality of metal rails and is coupled to the electronic components. The power mesh includes a plurality of metal trunks. The metal trunks are formed among the Nth metal layer to the ith metal layer. The metal trunks are interconnected by a plurality of first vias, and connected to the metal rails by a plurality of second vias, wherein i is a positive integer smaller than N. The power supply ring includes a plurality of metal rings. The metal rings are formed by parts of metal trunks that are densely concentrated. The power supply ring is used for receiving a power and conducting the power to the power distribution network through the power mesh. Then, the power distribution network distributes the power to the electronic components. 
     In another preferred embodiment according to the invention, the metal rings are also formed among the (N−1)th metal layer to the ith metal layer. The metal rings are also interconnected by a plurality of third vias. 
     The advantage and spirit of the invention may be understood by the following recitations together with the appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE APPENDED DRAWINGS 
         FIG. 1A  shows a simplified section view of a conventional IC die  1 . 
         FIG. 1B  shows the routing formed at metal layers  126  and  125  of the IC die  1 . 
         FIG. 2A  shows a simplified section view of an IC die  2  in a preferred embodiment according to the invention. 
         FIG. 2B  shows the routing formed at metal layers  228  and  227  of the IC die  2 . 
         FIG. 3  is a flow diagram of the method for designing IC die according to the invention. 
         FIG. 4  is a practical design diagram case of a part of the generated power supply ring after adjusting the wiring density of the metal routing according to the invention. 
         FIG. 5  is a practical design diagram case of the power supply ring (edge automatic routing) formed by computer automation according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The characteristic, spirit, advantage, and convenience in practice of the invention can be particularly explained by the following preferred embodiments according to the invention. 
     Please refer to  FIG. 2A .  FIG. 2A  shows a simplified sectional view of an IC die (or a chip)  2  in a preferred embodiment according to the invention. As shown in  FIG. 2A , the IC die  2  includes a semiconductor layer  20 , eight successive metal layers ( 221 ˜ 228 ) from bottom to top, several insulating layers  24  formed between two adjacent metal layers respectively, and a passivation layer  26 . The semiconductor layer  20  is used for forming electronic components such as transistors (not shown in  FIG. 2A ). The number of the metal layers is determined by the complexity of the practical routing. Thus, the eight metal layers shown in  FIG. 2A  are provided only for the convenience of explanation, not as a limit to the invention. 
     Regarding the routing at the metal layers  221 ˜ 228 , a power distribution network (not shown in  FIG. 2A ) is formed at the first metal layer  221  and coupled to the electronic components. The power distribution network can include metal rails with a first line width. The metal rails are formed at the first metal layer  221  and coupled to the electronic components. 
     Please refer to  FIG. 2B .  FIG. 2B  shows the higher metal layers and the routing formed thereon. 
     As shown in  FIG. 2B , a power mesh  28  is formed among the Nth metal layer (the eighth metal layer  228  shown in  FIG. 2B ) to the ith metal layer ( FIG. 2B  only shows the seventh metal layer  227 ). In an embodiment, N is an integer larger than or equal to 6, i is an integer ranging from (N−3) to (N−1). 
     The power mesh  28  includes a plurality of metal trunks  282  and  284  with a second line width. And, the metal trunks  282  and  284  formed at different metal layers (e.g., the eighth metal layer  228  and the seventh metal layer  227  shown in  FIG. 2B ) are interconnected by a first via  242  formed at the insulating layer  24 . In the same way, the power mesh  28  is connected to the power distribution network (not shown in  FIG. 2B ) by a second via (not shown in  FIG. 2B ) formed at the insulating layer  24 . In practical applications, if eight metal layers are provided, the routing of the metal trunks will use the eighth and the seventh metal layers. For the complicated routing, even the sixth and the fifth metal layers are also used. If six metal layers are provided, the routing of the metal trunks generally uses the sixth metal layer and the fifth metal layers. 
     In fact, the second line width can be larger than or equal to the first line width. In an embodiment, the second line width is wider than the first line width. That is to say, in this embodiment, the line widths of the metal trunks  282  and  284  are wider than the line widths of the metal rails. 
     As also shown in  FIG. 2B , the metal trunks  282  and  284  are divided into a power metal trunk  282  for connecting power and a ground metal trunk  284  for connecting ground. At the same metal layer, the power metal trunk  282  and the ground metal trunk  284  are interlaced. The metal trunks  282  and  284  formed at the adjacent metal layers (e.g., the eighth metal layer  228  and the seventh metal layer  227 ) are perpendicular to each other. The power metal trunks  282  formed at the adjacent metal layers (e.g., the eighth metal layer  228  and the seventh metal layer  227 ) are connected to each other, and the ground metal trunks  284  formed at the adjacent metal layers (e.g., the eighth metal layer  228  and the seventh metal layer  227 ) are also mutually connected. 
     Please refer to  FIG. 2B  again. A power supply ring  27  (a small section of the power supply ring  27  is shown in  FIG. 2B ) can be formed at the top metal layer  228 . The power supply ring  27  can include metal rings  272  and  274  with the second line width. That is to say, in an embodiment of the invention, the line widths of the metal rings  272  and  274  are the same with the line widths of the metal trunks  282  and  284 . In the invention, the required structure of the metal rings  272  and  274  is formed by adjusting the wiring density of the metal trunks  282  and  284 . The power supply ring  27  formed by defining the metal trunks  282  and  284  is capable of receiving a power and conducting the power to the power distribution network through the power mesh  28 . The power distribution network can be further used for distributing the power to the electronic components. 
     According to the routing technologies of the invention, the impedance difference between the power mesh  28  and the power supply ring  27  is reduced, and overheating of the metal routing is prevented. In addition, in order to ease off the routing congestion of the power mesh  28  and the power supply ring  27 , the metal rings  272  and  274  can also be formed among the (N−1)th metal layer to the ith metal layer in another preferred embodiment of the invention as shown in  FIG. 2B . 
     According the characteristic, spirit, and advantage of the invention, the invention also discloses a method  3  for designing an IC die (or a chip). Substantially, the IC die includes a semiconductor layer and N successive metal layers from bottom to top, wherein N can be a positive integer larger than or equal to 6. Each of the metal layers is isolated and formed over the semiconductor layer. The following will describe in detail the steps of the method  3  for designing an IC die according to the invention. 
     Please refer to  FIG. 3 . Firstly, the designing method  3  performs step S 30  to provide a layout of electronic components on the semiconductor layer. 
     Then, the designing method  3  performs step S 32  to provide a layout of a power distribution network at the first metal layer. The power distribution network includes metal rails and is coupled to the electronic components. 
     Next, the designing method  3  performs step S 34  to provide a layout of the power mesh among the Nth metal layer to the ith metal layer. i is an integer ranging from (N−3) to (N−1). The power mesh can include metal trunks with a second line width, and the second line width can be set wider than or equal to the first line width. The metal trunks are mutually interconnected by a plurality of first vias and further connected to the metal rails by a plurality of second vias. 
     At last, the designing method  3  performs step S 36  to adjust a wiring density of the metal trunks around the power mesh to form a power supply ring. The power supply ring includes a plurality of metal rings, the power supply ring receives a power and conducts the power to the power distribution network through the power mesh. The power supply ring can further distribute the power to the electronic components. 
     In order to ease off the routing congestion of the power mesh and the power supply ring, the designing method  3  can further provide a layout of the metal rings among the (N−1)th metal layer to the ith metal layer. 
     In an embodiment according to the invention, because the needed power supply rings can be generated by using the metal routing with the same line width, the needed power supply rings will be formed by adjusting the wiring density of the metal routing in a computer-automatized way after a user definition. In this way, it is not necessary to spend extra human resource for the routing in different circuit layouts. 
     Please refer to  FIG. 4  and  FIG. 5 .  FIG. 4  is a practical design diagram of a part of the generated power supply ring after adjusting the wiring density of the metal routing.  FIG. 5  is a practical design diagram of the power supply ring (edge automatic routing) formed by computer automation corresponding to the different circuit layouts. 
     With the example and explanations above, the features and spirits of the invention will be hopefully well described. Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teaching of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.