Patent Publication Number: US-2023153508-A1

Title: Cell layout of semiconductor device

Description:
RELATED APPLICATIONS 
     This application is continuation of U.S. application Ser. No 17/151,189, filed Jan. 17, 2021, now U.S. Pat. No. 11,568,119, issued Jan. 31, 2023, which is continuation of U.S. application Ser. No. 16/210,808, filed Dec. 5, 2018, now U.S. Pat. No. 10,922,466, issued Feb. 16, 2021, which is continuation of U.S. application Ser. No. 14/859,162, filed Sep. 18, 2015, now U.S. Pat. No. 10,162,925, issued Dec. 25, 2018, which is herein incorporated by reference. 
    
    
     BACKGROUND 
     Many circuit cells (inverters, comparators, registers, memory cells, etc.) in a semiconductor circuit are required to operate in synchronized timing. In order to provide precise clock signals to these circuit cells synchronously, a routing distribution (also known as a clock tree) of clock signals should be well designed, so as to prevent Signal Electromagnetic (SEM) issues happened on pins of circuit cells. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG.  1    is a top view diagram illustrating a cell layout of a semiconductor device; 
         FIG.  2    is a top view diagram illustrating a cell layout of a semiconductor device according to an embodiment of the disclosure; 
         FIG.  3    is a sectional view diagram illustrating the cell layout along a sectional line A-A shown in  FIG.  2   ; 
         FIG.  4    is a top view diagram illustrating another cell layout of a semiconductor device according to an embodiment of the disclosure; 
         FIG.  5    is a top view diagram illustrating another cell layout with tapping connectors of a semiconductor device according to an embodiment of the disclosure; 
         FIG.  6    is a top view diagram illustrating a cell layout of a semiconductor device according to an embodiment of the disclosure; 
         FIG.  7    is a sectional view diagram illustrating the cell layout along a sectional line B-B shown in  FIG.  6   ; 
         FIG.  8    is a top view diagram illustrating a cell layout of a semiconductor device according to an embodiment of the disclosure; 
         FIG.  9    is a top view diagram illustrating a cell layout of a semiconductor device according to an embodiment of the disclosure; 
         FIG.  10 A  is a top view diagram illustrating another embodiments of the connecting via between the first metal interconnect and the second metal interconnect; 
         FIG.  10 B  is a top view diagram illustrating still another embodiments of the connecting via between the first metal interconnect and the second metal interconnect; 
         FIG.  11    is a schematic diagram illustrating a cell layout library stored on a non-transitory computer readable storage according to an embodiment of the disclosure; and 
         FIG.  12    is a flow chart illustrating a synthesis method according to an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, specific details are presented to provide a thorough understanding of the embodiments of the present disclosure. Persons of ordinary skill in the art will recognize, however, that the present disclosure can be practiced without one or more of the specific details, or in combination with other components. Well-known implementations or operations are not shown or described in detail to avoid obscuring aspects of various embodiments of the present disclosure. 
     The terms used in this specification generally have their ordinary meanings in the art and in the specific context where each term is used. The use of examples in this specification, including examples of any terms discussed herein, is illustrative only, and in no way limits the scope and meaning of the disclosure or of any exemplified term. Likewise, the present disclosure is not limited to various embodiments given in this specification. 
     It will be understood that, although the terms “first,” “second,” etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     As used herein, the terms “comprising,” “including,” “having,” “containing,” “involving,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. 
     Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, implementation, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, uses of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, implementation, or characteristics may be combined in any suitable manner in one or more embodiments. 
       FIG.  1    is a top view diagram illustrating a cell layout  100  of a semiconductor device. The cell layout  100  includes a cell block CB 1  of the semiconductor device. In some embodiments, the cell block CB 1  is a basic cell unit, including, for example, a transistor, a switch, a logic gate, a register, an inverter, a comparator, a clock buffer, etc., of the semiconductor device. Many cell blocks are implemented in one semiconductor device, and these basic cell blocks are linked together to perform some functions, including, for example, storing, adding, multiplying, comparing, etc. In some embodiments, the cell layout  100  shown in  FIG.  1    is stored in a cell layout library and regarded as a standard cell layout. 
     In some embodiments, each of the cell blocks is configured to have some pins for transmitting signals. In the embodiments shown in  FIG.  1   , the cell block CB 1  includes four pins PIN 1 , PIN 2 , PIN 3  and PIN 4 . Among these four pins, the pin PIN 1  is a clock-related pin. For illustration, the pin PIN 1  is the clock input pin of the cell block CB 1  for receiving a clock signal from a system clock generator (not shown in figures). The timing of the cell block CB 1  is controlled by the pin PIN 1 , such that the cell block CB 1  is synchronized with other cell blocks in the semiconductor device. In some embodiments, the other pins PIN 2 , PIN 3  and PIN 4  are each configured as one of a data input pin, a control signal input pin, an output pin and/or an enable pin depending on the functions of the cell block CB 1 . The amount of the pins of the cell block CB 1  in  FIG.  1    is given for illustrative purposes. Various amounts of the pins of the cell block CB 1  are within the contemplated scope of the present disclosure. 
     In a cell layout as shown in  FIG.  1   , in some embodiments, the clock-related pin PIN 1  is implemented on a lower metal layer in the cell layout  100  together with other pins PIN 2 -PIN 4 . For illustration, the clock-related pin PIN 1  is implemented on the 1st metal layer (i.e., M 1  layer). 
     In order to make sure synchronization of different cell blocks, a clock tree is usually implemented to distribute the clock signals in the same timing to each of the cell blocks. During the clock tree spanning, a clock-trunk of the clock tree is globally routed first, and some clock buffers are placed at different locations on the clock tree for boosting the clock signals. Afterwards, the layers and tracks are assigned for clock-leaf connection. At last, detail routings are assigned for clock-leaf connections between the clock-leaf and the clock pins of all cell blocks. 
     In typical circuit design, circuit components are arranged in an automatic synthesis process assisted by electronic design automatic (EDA) tools to optimize space and/or circuit performance. However, current EDA tools have poor control on routing patterns (especially on lower metal layers) and may induce many SEM issues or failures in design rule check (DRC) while clock routing. Leaf wirings of the clock routing established by the EDA tools may occupy unnecessary resource (e.g., routing space on the layout) and significantly impact signal routability during the synthesis process. 
     In the cell layout  100  shown in  FIG.  1   , the pin PIN 1  of the cell block CB 1  is a tapping point of the clock signal. The clock signal from the clock tree is connected to the pin PIN 1  in the cell block CB 1 . However, the lower metal layers (e.g., M 1  layer and M 2  layer) in the cell layout  100  are usually occupied by many signal wirings. When the clock-leaf connections between the clock-leaf and the clock pins of all cell blocks are generated automatically by Electronic Design Automation (EDA) tools, the clock-leaf connections usually adopt a narrow signal wiring, or the clock-leaf connections might be overlapped with (or adjacent to) many other signals wiring. These clock-leaf connections will be failed in a design rule check (DRC) or a signal electromagnetic (SEM) simulation test because the clock signal transmitted over the clock-leaf connections tends to be affected by other signals. 
     Reference is made to  FIG.  2    and  FIG.  3   .  FIG.  2    is a top view diagram illustrating a cell layout  110  of a semiconductor device according to some embodiments of the present disclosure.  FIG.  3    is a sectional view diagram illustrating the cell layout  110  along a sectional line A-A shown in  FIG.  2   , according to some embodiments of the present disclosure. As shown in  FIG.  2   , the cell layout  110  includes the cell block CB 1  and a tapping connector TAP 1 . 
     The cell block CB 1  includes a clock-related pin PIN 1 . The clock-related pin PIN 1  is disposed at an Nth metal layer in the cell layout  110 . In some embodiments, N is an integer greater than or equal to 0. In some embodiments, the tapping connector TAP 1  is disposed, for illustration, at a (N+1)th metal layer and a (N+2)th metal layer, and the tapping connector TAP 1  is stacked above the clock-related pin PIN 1  of the cell block CB 1 . 
     The tapping connector TAP 1  is electrically connected to the clock-related pin PIN 1  and forms an equivalent tapping point of the clock-related pin PIN 1  of the cell block CB 1 , such that the routing of the clock tree will be easier (not required to find out a path to the clock-related pin PIN 1  in the lower metal layer). As a result, the clock tree is able to tap to the cell block CB 1  through the tapping connector TAP 1  on a relatively higher metal layer on the (N+2)th metal layer. In some other embodiments, the tapping connector (not shown in figures) is disposed and stacked above at least one of non clock-related pins PIN 2 ˜PIN 4  of the cell block CB 1 , and the tapping connector forms an equivalent tapping point of the non clock-related pin(s) PIN 2 ˜PIN 4  of the cell block CB 1 . 
     In the embodiments shown in  FIG.  3   , the clock-related pin PIN 1  is disposed at the 1st metal layer (i.e., the M 1  layer). In some embodiments, N is an integer greater than or equal to 0. The clock-related pin PIN 1  is electrically connected to an active layer OD of the semiconductor device through a connecting via VIA 0 . In some embodiments, the clock-related pin PIN 1  is electrically connected to an active layer OD of the semiconductor device through a contact (not shown). In some embodiments, the clock-related pin PIN 1  is electrically connected to a POLY or a gate layer (not shown) of the semiconductor device through a contact (not shown) or a via. The tapping connector TAP 1  includes a first metal interconnect INT 1  and a second metal interconnect INT 2 . For illustration purpose, the tapping connector TAP 1  only includes two metal interconnects in two metal layers, it is understood that the tapping connector TAP 1  may include J numbers of metal interconnects in K numbers of metal layers, wherein the J, K are integer numbers and are larger than or equal to 1. In some embodiments, J is equal to K. In some embodiments, J is larger than K. 
     As shown in  FIG.  2    and  FIG.  3   , the first metal interconnect INT 1  is disposed at the (N+1)th metal layer (i.e., the 2nd metal layer, M 2 ) and stacked over the clock-related pin PIN 1  of the cell block CB 1 . The first metal interconnect INT 1  is electrically connected to the clock-related pin PIN 1  through another connecting via VIA 1 . 
     The second metal interconnect INT 2  is disposed at the (N+2)th metal layer (i.e., the 3rd metal layer, M 3 ) and stacked over the first metal interconnect INT 1 . The second metal interconnect INT 2  is electrically connected to the first metal interconnect INT 1  through another connecting via VIA 2 . The second metal interconnect INT 2  forms the equivalent tapping point of the clock-related pin PIN 1  of the cell block CB 1 . The clock tree is able to tap on the second metal interconnect INT 2  instead of directly connecting to the clock-related pin PIN 1  of the cell block CB 1 . Compared to some approaches without tapping connector TAP 1 , it is easier for clock tree spanning to connect the clock-leaf to the equivalent tapping point, for example, the second metal interconnect INT 2  on the M 3  layer in  FIG.  3   . 
     In some embodiments, in  FIG.  2   , a width WD 1  of the first metal interconnect INT 1  is 1 to 3 times as wide as a minimum trace width on the M 2  layer in  FIG.  3   , according to design rules. A width WD 2  of the second metal interconnect INT 2  is 1 to 3 times the minimum trace width on the M 3  layer according to the design rules. 
     When the width WD 1  or the width WD 2  is decreased, the current density over the first metal interconnect INT 1  or the second metal interconnect INT 2  will be increased, and the clock signal transmitted over the first metal interconnect INT 1  and the second metal interconnect INT 2  will be affected by SEM noises and face DRC issues. 
     When the width WD 1  or the width WD 2  is increased, the current density over the first metal interconnect INT 1  or the second metal interconnect INT 2  will be reduced, and it will prevent the SEM noises and DRC issues. 
     In some embodiments, the width WD 1  is assigned to be around 2 times as wide as a minimum trace width on the M 2  layer, and the width WD 2  is assigned to be around 2 times as wide as a minimum trace width on the M 3  layer. The minimum trace width on the M 2 /M 3  layer is decided by a manufacturing rule or the design rules depending on different scales of manufacturing process. For example, the minimum trace width on the M 2  layer is about 32 nanometer (nm) and the minimum trace width on the M 3  layer is about 38 nanometer (nm) under the 16 nm manufacturing process. 
     As the embodiments shown in  FIG.  2   , the first metal interconnect INT 1  and the second metal interconnect INT 2  are widened interconnects, which, in some embodiments, have widths that are 2 times as wide as the minimum trace width on corresponding layers, such that the SEM noise will be reduced on the first metal interconnect INT 1  and the second metal interconnect INT 2 , and the widths of the first metal interconnect INT 1  and the second metal interconnect INT 2  will meet the width requirements defined in the design rules. 
     In some embodiments, the width WD 2  is 0.5 to 3 times as wide as the width WD 1 . In some embodiments, to balance the tradeoff between DRC/SEM issues and routing resources, the width WD 2  is assigned to be 0.6 to 0.67 times as wide as the width WD 1 . 
     For illustration, the cell layout  110 , when the width WD 2  is assigned to be 0.6 to 0.67 times as wide as the width WD 1 , has less DRC failures and more SEM benefits, compared to that the width WD2 is assigned to be, for example, 0.5 to 0.6 times, as wide as the width WD 1 . On the other hand, the cell layout  110 , when the width WD 2  is assigned to be 0.6 to 0.67 times as wide as the width WD 1 , has SEM benefits and is able to pass DRC without sacrificing too much routing resources, compared to that the width WD 2  is assigned to be, for example, 0.67 to 3 times, as wide as the width WD 1 . 
     The cell layout  110 , which includes the cell block CB 1  together with the tapping connector TAP 1  shown in  FIG.  2    and  FIG.  3   , is stored in the cell layout library beside the cell layout  100  shown in  FIG.  1   . The cell layout  110  regarded as a substitute cell layout corresponding to the standard cell layout (i.e., the cell layout  100  shown in  FIG.  1   ). 
     In response to that the standard cell layout (e.g., the cell layout  100 ) adopted in a synthesis process fails in a design rule check (DRC) or a signal electromagnetic (SEM) simulation test, the substitute cell layout (e.g., the cell layout  110 ) is utilized to replace the standard cell layout in the synthesis process. 
     In aforesaid embodiments, the cell block CB 1  is a sequential cell (e.g., the cell block utilized as the transistor, logic gates or inverter). In the sequential cell, only one pin is clock-related pin. However, in some specific cell, there are multiple clock-related pins existed in one cell block. For example, the input pin and the output pin of a clock buffer are both clock-related pin. 
     Reference is also made to  FIG.  4    and  FIG.  5   .  FIG.  4    is a top view diagram illustrating another cell layout  200  of a semiconductor device according to an embodiment of the disclosure.  FIG.  5    is a top view diagram illustrating another cell layout  210  with tapping connectors TAP 2 -TAP 3  of a semiconductor device according to an embodiment of the disclosure. 
     The cell block CB 2  of the cell layout  200  shown in  FIG.  4    has two pins PIN 1  and PIN 2 . In the embodiment, the pins PIN 1  and PIN 2  of the cell block CB 2  are both clock-related pins. 
     In the cell layout  210  shown in  FIG.  5   , there are two tapping connectors TAP 2  and TAP 3  stacked over the clock-related pins PIN 1  and PIN 2  of the cell block CB 2 . The tapping connector TAP 2  includes a first metal interconnect INT 1  and a second metal interconnect INT 2 . The tapping connector TAP 3  includes a third metal interconnect INT 3  and a fourth metal interconnect INT 4 . Details about the first metal interconnect INT 1  and the second metal interconnect INT 2  of the tapping connector TAP 2  and the third metal interconnect INT 3  and the fourth metal interconnect INT 4  of the tapping connector TAP 3  are referred to the descriptions of the tapping connector TAP 1  in aforesaid embodiment, and not to be repeated here. 
     In some embodiments, the size of the first metal interconnect INT 1  is similar to the size of the third metal interconnect INT 3 , and the size of the second metal interconnect INT 2  is similar to the size of the fourth metal interconnect INT 4 . 
     For simplicity of illustration, INT 2 /INT 1  indicates a ratio of the size of the second metal interconnect INT 2  to the size of the first metal interconnect INT 1 , and INT 4 /INT 3  indicates a ratio of the size of the fourth metal interconnect INT 4  to the size of the third metal interconnect INT 3 . In various embodiments, INT 4 /INT 3  is larger than INT 2 /INT 1 . In alternative embodiments, INT 4 /INT 3  ranges between (INT 2 /INT 1 )/ 2  and (INT 2 /INT 1 )*2. 
     In some embodiment, a width of the second metal interconnect INT 2  is 0.5 to 3 times as wide as a width of the first metal interconnect INT 1 . In some embodiments, the width of the second metal interconnect INT 2  is assigned to be 0.6 to 0.67 times as wide as the width of the first metal interconnect INT 1 . 
     In some embodiment, a width of the second metal interconnect INT 4  is 0.5 to 3 times as wide as a width of the first metal interconnect INT 3 . In some embodiments, the width of the second metal interconnect INT 4  is assigned to be 0.6 to 0.67 times as wide as the width of the first metal interconnect INT 3 . 
     For illustration purpose, the tapping connector TAP 2 /TAP 3  only includes two metal interconnects in two metal layers, it is understood that the tapping connector TAP 2 /TAP 3  may include J numbers of metal interconnects in K numbers of metal layers, wherein the J, K is integer numbers and is larger than or equal to 1. In some embodiments, J is equal to K. In some embodiments, J is larger than K. 
     In some embodiments, the cell layout  200  is stored in the cell layout as a standard cell layout. The cell layout  210 , which includes the cell block CB 2  together with the tapping connectors TAP 1 -TAP 2  shown in  FIG.  5   , is stored in the cell layout library beside the cell layout  200  shown in  FIG.  4   . The cell layout  210  regarded as a substitute cell layout corresponding to the standard cell layout (i.e., the cell layout  200  shown in  FIG.  4   ). 
     Aforesaid embodiments in  FIGS.  2 - 5    have disclosed a cell layout including the tapping connector. In some examples, the tapping connector includes widened metal interconnects stacked on one or more clock-related pins in the cell block. The widened metal interconnects reduce the current density of a bypassing signal (e.g., a clock signal), and reduce the risk to fail in DRC. The cell layout in the embodiment reduces a complexity of routing pattern at lower-layer is reduced, and also reduce the SEM impact from other wirings to the clock-related pin. 
     Reference is made to  FIG.  6    and  FIG.  7   .  FIG.  6    is a top view diagram illustrating a cell layout  310  of a semiconductor device according to an embodiment of the disclosure.  FIG.  7    is a sectional view diagram illustrating the cell layout  310  along a sectional line B-B shown in  FIG.  6   . The cell layout  310  disclosed in  FIG.  6    demonstrates another example of a substitute cell layout corresponding to the cell layout  100  (the standard cell layout) shown in  FIG.  1   . 
     As shown in  FIG.  6   , the cell layout  310  includes a cell block CB 3  and a tapping connector TAP 4 . The cell block CB 3  includes a clock-related pin PIN 1  and other pins PIN 2 -PIN 4 . The clock-related pin PIN 1  and the other pins PIN 2 -PIN 4  are disposed at the Nth metal layer in the cell layout  310 . In some embodiments, N is equal to 1, and the clock-related pin PIN 1  is disposed at the 1st metal layer (M 1 ). In some other embodiments, N is an integer greater than or equal to 0. 
     As shown in  FIG.  6    and  FIG.  7   , the tapping connector TAP 4  is disposed at the (N+1)th metal layer (the 2nd metal layer, M 2 ) and a (N+2)th metal layer (the 3rd metal layer, M 3 ). The tapping connector TAP 4  is stacked above the clock-related pin PIN 1  of the cell block CB 3 . The tapping connector TAP 4  is electrically connected to the clock-related pin PIN 1  and forms an equivalent tapping point of the clock-related pin PIN 1  of the cell block CB 3 . In some embodiments, the tapping connector TAP 4  may be electrically connected to the pins other than the clock-related pin. 
     For illustration purpose, the tapping connector TAP 4  only includes two metal interconnects in two metal layers, it is understood that the tapping connector TAP 4  may include J numbers of metal interconnects in K numbers of metal layers, wherein the J, K is integer numbers and is larger than or equal to 1. In some embodiments, J is equal to K. In some embodiments, J is larger than K. 
     The tapping connector TAP 4  includes a plurality of first metal interconnects and a plurality of second metal interconnects. In the embodiment shown in  FIG.  6    and  FIG.  7   , there are three first metal interconnects INT 1   a -INT 1   c  and two second metal interconnects INT 2   a -INT 2   b  in the tapping connector TAP 4 . For illustration, the first metal interconnects INT 1   a -INT 1   c  and two second metal interconnects INT 2   a -INT 2   b  form a 3*2 interconnect-mesh.  FIG.  6    and  FIG.  7    show only three first metal interconnects INT 1   a -INT 1   c  and two second metal interconnects INT 2   a -INT 2   b,  but they are given for illustrative purposes. Various numbers of the first/second metal interconnects are within the contemplated scope of the present disclosure. In some embodiments, the interconnect-mesh is an A*B mesh. Each of A and B is a positive integer greater than or equal to 1. 
     The first metal interconnects INT 1   a -INT 1   c  are disposed at the 2nd metal layer (M 2 ). The first metal interconnects INT 1   a -INT 1   c  are parallel to each other. At least one of first metal interconnects INT 1   a -INT 1   c  is stacked over the clock-related pin PIN 1  and is electrically connected to the clock-related pin PIN 1  through a connecting via VIA 1 . 
     The second metal interconnects INT 2   a -INT 2   b  are disposed at the 3rd metal layer (M 3 ). The second metal interconnects INT 2   a -INT 2   b  are parallel to each other. The second metal interconnects INT 2   a -INT 2   b  are stacked over the first metal interconnects INT 1   a -INT 1   c.  The second metal interconnects INT 2   a -INT 2   b  are disposed to be perpendicular to the first metal interconnects INT 1   a -INT 1   c,  such that the first metal interconnects INT 1   a -INT 1   c  and the second metal interconnects INT 2   a -INT 2   b  forms the 3*2 mesh. The second metal interconnects INT 2   a -INT 2   b  are electrically connected to the first metal interconnects INT 1   a -INT 1   c  through connecting vias VIA 2 . The second metal interconnects INT 2   a -INT 2   b  form the equivalent tapping point of the clock-related pin PIN 1  of the cell block CB 3 . 
     Aforesaid embodiments in  FIG.  6    and  FIG.  7    disclose a cell layout including the tapping connector. In some embodiments, the tapping connector includes a metal interconnect-mesh stacked on one or more clock-related pins in the cell block. The metal interconnect-mesh reduces the current density of a bypassing signal (e.g., a clock signal), and reduces the risk to fail in DRC. The clock-related pin in the cell layout originally at a lower metal layer is pre-stacked through the tapping connector to a higher metal layer, such that a complexity of routing pattern at lower-layer is reduced in the cell layout. The tapping connector is formed by a widened metal interconnect or a metal interconnect-mesh, such that a bypass current will not congest in a narrow path along the routing pattern. Accordingly, the clock signal is transmitted to the clock-related pin through the tapping connector, instead of being transmitted through a narrow path. As a result, SEM impact from other surrounding wirings is avoided. 
     In addition, when the cell block CB 3  includes more than one clock-related pin (not shown in figures), an additional metal interconnect-mesh (i.e., the tapping connector TAP 4 ) is implemented on other clock-related pin(s). The details can be referred to the embodiment disclosed in  FIG.  5   , in which the cell block CB 2  includes multiple clock-related pins and multiple tapping connectors. 
     In some embodiments, a width WD 3  of each of the first metal interconnect INT 1   a -INT 1   c  is longer than the minimum trace width on the M 2  layer according to design rules, and a width WD 4  of each of the second metal interconnect INT 2   a -INT 2   b  is longer than a minimum trace width on the M 3  layer according to the design rules. 
     In some embodiments, the width WD 3  is as Q times width as the width WD 4 . In some embodiments, Q is a positive value from, for example, 0.7 to 1.5. In some other embodiment, Q is a positive value from, for example, 0.85 to 0.9. 
     In some embodiments, the width WD 3  of each of the first metal interconnect INT 1   a -INT 1   c  is similar to the width WD 4  of each of the second metal interconnect INT 2   a -INT 2   b.    
     In some other embodiments, the width WD 3  of each of the first metal interconnect INT 1   a -INT 1   c  is different from the width WD 4  of each of the second metal interconnect INT 2   a -INT 2   b.    
     Reference is made to  FIG.  8   .  FIG.  8    is a top view diagram illustrating a cell layout  410  of a semiconductor device according to an embodiment of the disclosure. The cell layout  410  disclosed in  FIG.  8    demonstrates another embodiment of a substitute cell layout corresponding to the cell layout  100  (the standard cell layout) shown in  FIG.  1   . 
     The cell layout  410  includes a cell block CB 4  and a tapping connector TAPS. The cell block CB 4  includes a clock-related pin PIN 1  and other pins PIN 2 -PIN 4 . The clock-related pin PIN 1  and the other pins PIN 2 -PIN 4  are disposed at the Nth metal layer in the cell layout  410 . In some embodiments, N is equal to 1, and the clock-related pin PIN 1  is disposed at the 1st metal layer (M 1 ). In some embodiments, N is an integer greater than or equal to 0. 
     For illustration purpose, the tapping connector TAPS only includes two metal interconnects in two metal layers, it is understood that the tapping connector TAPS may include J numbers of metal interconnects in K numbers of metal layers, wherein the J, K is integer numbers and is larger than or equal to 1. In some embodiments, J is equal to K. In some embodiments, J is larger than K. 
     The tapping connector TAPS is a combination of embodiments illustrated in  FIG.  5    and  FIG.  6   . The tapping connector TAP 5  includes a first metal interconnect INT 1  and a plurality of second metal interconnects INT 2   a -INT 2   b.  The first metal interconnect INT 1  is disposed at the 2nd metal layer (M 2 ) and stacked over the clock-related pin PIN 1 . The first metal interconnect INT 1  is electrically connected to the clock-related pin PIN 1 . 
     The second metal interconnects INT 2   a -INT 2   b  are disposed at the 3rd metal layer (M 3 ). The second metal interconnects INT 2   a -INT 2   b  are parallel to each other. The second metal interconnects INT 2   a -INT 2   b  are stacked over and disposed to be perpendicular to the first metal interconnect INT 1 . The second metal interconnects INT 2   a -INT 2   b  are electrically connected to the first metal interconnect INT 1 . The second metal interconnects INT 2   a -INT 2   b  form the equivalent tapping point of the clock-related pin PIN 1  of the cell block CB 4 . 
     In some embodiments, a width WD 5  of the first metal interconnect is 1 to 3 times as wide as a minimum trace width on the 2nd metal layer according to design rules, and a width WD 6  of each of the second metal interconnects INT 2   a -INT 2   b  is longer than a minimum trace width on the 3rd metal layer according to the design rules. 
     In some embodiments, the width WD 5  of the first metal interconnect INT 1  is different from the width WD 6  of each of the second metal interconnect INT 2   a -INT 2   b.    
     In some embodiments, the width WD 5  is as R times width as the width WD 6 . In some embodiments, R is a positive value from, for example, 1.5 to 5. In some other embodiments, R is a positive value from, for example, 1.7 to 2.7. 
     Reference is made to  FIG.  9   .  FIG.  9    is a top view diagram illustrating a cell layout  510  of a semiconductor device according to an embodiment of the disclosure. The cell layout  510  disclosed in  FIG.  9    demonstrates various embodiments of a substitute cell layout corresponding to the cell layout  100  (the standard cell layout) shown in  FIG.  1   . 
     The cell layout  510  includes a cell block CB 5  and a tapping connector TAP 6 . The cell block CB 5  includes a clock-related pin PIN 1  and other pins PIN 2 -PIN 4 . The clock-related pin PIN 1  and the other pins PIN 2 -PIN 4  are disposed at the Nth metal layer in the cell layout  510 . In some embodiments, N is equal to 1, and the clock-related pin PIN 1  is disposed at the 1st metal layer (M 1 ). In some embodiments, N is an integer greater than or equal to 0. 
     For illustration purpose, the tapping connector TAP 5  only includes two metal interconnects in two metal layers, it is understood that the tapping connector TAPS may include J numbers of metal interconnects in K numbers of metal layers, wherein the J, K is integer numbers and is larger than or equal to 1. In some embodiments, J is equal to K. In some embodiments, J is larger than K. 
     The tapping connector TAP 6  is a combination of embodiments illustrated in  FIG.  5    and  FIG.  6   . The tapping connector TAP 6  includes a plurality of first metal interconnects INT 1   a -INT 1   c  and a second metal interconnect INT 2 . The first metal interconnects INT 1   a -INT 1   c  are disposed at the 2nd metal layer. The first metal interconnects INT 1   a -INT 1   c  are parallel to each others. At least one of first metal interconnects INT 1   a -INT 1   c  are stacked over the clock-related pin PIN 1  and electrically connected to the clock-related pin PIN 1 . 
     The second metal interconnect INT 2  is disposed at the 3rd metal layer and stacked over the first metal interconnects INT 1   a -INT 1   c.  The second metal interconnect INT 2  is electrically connected to the first metal interconnects INT 1   a -INT 1   c,  and the second metal interconnect INT 2  forms an equivalent tapping point of the clock-related pin PIN 1  of the cell block CB 5 . 
     In some embodiments, a width WD 7  of each of the first metal interconnects INT 1   a -INT 1   c  is longer than a minimum trace width on the 2nd metal layer according to the design rules, and a width WD 8  of the second metal interconnect INT 2  is 1 to 3 times as wide as a minimum trace width on the 3rd metal layer according to design rules. 
     In some embodiments, the width WD 7  of each of the first metal interconnects INT 1   a -INT 1   c  is different from the width WD 8  of the second metal interconnect INT 2 . 
     In some embodiments, the width WD 7  is as T times width as the width WD 8 . In some embodiments, T is a positive value from 0.3 to 0.7. In some other embodiments, T is a positive value from 0.33 to 0.55. 
     In aforesaid embodiments, the connecting via VIA 2  between the first metal interconnect INT 1  and the second metal interconnect INT 2  shown in  FIG.  3    is formed in one piece. Reference is made to  FIG.  10 A  and  FIG.  10 B .  FIG.  10 A  is a top view diagram illustrating another embodiments of the connecting via between the first metal interconnect INT 1  and the second metal interconnect INT 2 .  FIG.  10 B  is a top view diagram illustrating still another embodiments of the connecting via between the first metal interconnect INT 1  and the second metal interconnect INT 2 . 
     As shown in  FIG.  10 A , the connecting via VIA 2  between the first metal interconnect INT 1  and the second metal interconnect INT 2  includes a 1*2 via-array. The 1*2 via-array is formed by two separated vias between the first metal interconnect INT 1  and the second metal interconnect INT 2 . The 1*2 via-array is suitable to reduce the SEM noise when the width WD 2  of the second metal interconnect INT 2  is assigned to be 0.6 to 0.67 times as wide as the width WD 1  of the first metal interconnect INT 1 . 
     As shown in  FIG.  10 B , the connecting via VIA 2  between the first metal interconnect INT 1  and the second metal interconnect INT 2  includes a 2*2 via-array. The 2*2 via-array is formed by four separated vias between the first metal interconnect INT 1  and the second metal interconnect INT 2 . The 2*2 via-array is suitable to reduce the SEM noise when the width WD 2  of the second metal interconnect INT 2  is assigned to longer than the width WD 1  of the first metal interconnect INT 1 . 
     Reference is made to  FIG.  11   , which is a schematic diagram illustrating a cell layout library  600  stored on a non-transitory computer readable storage according to an embodiment of the disclosure. The cell layout library  600  is associated with cell layouts for defining a layout design used by a processor for fabrication of at least one aspect of a semiconductor device. The cell layout library  600  includes standard cell layouts CL 1 -CL 2  and substitute cell layouts CL 1   a -CL 1   c  and CL 2   a -CL 2   c.    
     Each of the standard cell layouts (e.g., the cell layout  100  in  FIG.  1    and the cell layout  200  in  FIG.  4   ) includes a cell block having a clock-related pin. 
     Each of the substitute cell layouts CL 1   a -CL 2   c  corresponds to one of the standard cell layout CL 1 -CL 2 . In the embodiment, the substitute cell layouts CL 1   a -CL 1   c  corresponds to the standard cell layout CL 1 . The substitute cell layouts CL 2   a -CL 2   c  corresponds to the standard cell layout CL 2 . 
     Each of the substitute cell layouts CL 1   a -CL 2   c  includes a corresponding cell block and a tapping connector. The corresponding cell block is equivalent to the cell block of the standard cell layout. For illustration, the cell layout  110  in  FIG.  2   , the cell layout  310  in  FIG.  6   , the cell layout  410  in  FIG.  8    and the cell layout  510  in  FIG.  9    are substitute cell layouts corresponding to the cell layout  100  in  FIG.  1   . The cell layout  210  in  FIG.  5    is a substitute cell layout corresponding to the cell layout  200  in  FIG.  4   . 
     The tapping connector is stacked above a clock-related pin of the corresponding cell block. The tapping connector forms an equivalent tapping point of the clock-related pin of the corresponding cell block. Details of the tapping connector are mentioned in aforesaid embodiments, and not to be repeated here again. 
     In response to that the standard cell layout adopted in a synthesis process fails in a design rule check (DRC) or a signal electromagnetic (SEM) simulation test, the substitute cell layout is utilized to replace the standard cell layout in the synthesis process. For illustration, if the cell layout  100  in  FIG.  1    is adopted in a synthesis process and fails in a design rule check (DRC) or a signal electromagnetic (SEM) simulation test, one substitute cell layout selected from the cell layout  110  in  FIG.  2   , the cell layout  310  in  FIG.  6   , the cell layout  410  in  FIG.  8    or the cell layout  510  in  FIG.  9    is utilized to replace the cell layout  100  in  FIG.  1   . Then, the layout plan with the substitute cell layout will be entered to the synthesis process again. Because the substitute cell layout has the tapping connector pre-stacked on the clock-related pin, the layout plan with the substitute cell layout has a better chance to pass the design rule check (DRC) or the signal electromagnetic (SEM) simulation test. In some embodiments, the tapping connector is pre-stacked on non clock-related pin(s) of the cell layout. 
     In some embodiments, the tapping connector within one substitute cell layout is widened metal interconnects pre-stacked above the clock-related pin of the corresponding cell block (referring to the cell layout  110  in  FIG.  2   ). A width of each widened metal interconnect is 1 to 3 times as wide as a minimum trace width on a corresponding metal layer according to design rules. 
     In some embodiments, the tapping connector within one substitute cell layout is an interconnect-mesh pre-stacked above the clock-related pin of the corresponding cell block (referring to the cell layout  310  in  FIG.  6   , the cell layout  410  in  FIG.  8    or the cell layout  510  in  FIG.  9   ). The interconnect-mesh includes a plurality of metal interconnects disposed on two different metal layers. The metal interconnects are electrically connected to each others. 
     Reference is made to  FIG.  12   , which is a flow chart illustrating a synthesis method  700  according to an embodiment of the disclosure. The synthesis method  700  is suitable to synthesis a semiconductor device according to a cell layout library. The cell layout library includes standard cell layouts and corresponding substitute cell layouts (referring to the cell layout library  600  in  FIG.  11   ). 
     Operation S 701  of the synthesis method  700  is executed to plan the semiconductor device according to standard cell layouts in a cell layout library at the beginning. 
     Operation S 702  of the synthesis method  700  is executed to form a routing pattern to the standard cell layouts. In some embodiments, the routing pattern includes clock routes and signal routes. 
     Operation S 703  is executed to perform a design rule check (and/or a signal electromagnetic simulation test, SEM test) on the routing pattern, so as to check if a current congestion region exists in the layout plan (or if a narrow wiring existed in the layout plan). 
     Operation S 704  is executed to determine whether at least one of the standard cell layouts passes the DRC and/or the SEM test. In some embodiments, one of the design rule check or the SEM test is performed to the layout plan in operation S 703 , and the operation S 704  is executed to determine whether the layout plan passes the check/test or not. In other embodiments, both of the design rule check and the SEM test are performed to the layout plan in operation S 703 , and the operation S 704  is executed to determine whether the layout plan passes both of them, or fails in either one of them. 
     If the standard cell layouts pass the DRC, operation S 705  is executed to synthesize the semiconductor device according to the layout plan directly. 
     If at least one of the standard cell layouts is failed in the DRC (and/or the signal electromagnetic simulation test, SEM test), operations S 711 -S 713  are executed. Operation  711  is executed to identify at least one of the standard cell layouts failed in the DRC (or SEM test). Operation  712  is executed to adjust the layout plan by replacing the standard cell layouts failed in the DRC (or SEM) with substitute cell layouts in the cell layout library. Afterward, operation S 713  is executed to form a routing pattern to the standard cell layouts and the substitute cell layouts in the layout plan after adjustment. Then, operation S 705  is executed to synthesize the semiconductor device according to the layout plan after adjustment. 
     Aforesaid embodiments in  FIG.  11    and  FIG.  12    have disclosed the cell layout library  600  and the synthesis method  700 . In response to that the standard cell layout fails in the design rule check (DRC) or a signal electromagnetic (SEM) simulation test, the substitute cell layouts are utilized to replace the standard cell layouts. In some embodiments, each of the substitute cell layouts includes a tapping connector. The tapping connector can reduce the current density of a bypassing signal (e.g., a clock signal), and reduce the risk to fail in DRC. The cell layout in the embodiment reduces a complexity of routing pattern at lower-layer is reduced, and also reduce the SEM impact from other wirings to the clock-related pin. 
     In some embodiments, a device is disclosed that includes a cell block, at least one first metal interconnect, and second metal interconnects. The cell block includes a pin, and the pin is disposed at a Nth metal layer in a cell layout. The at least one first metal interconnect is disposed at a (N+1)th metal layer above the Nth metal layer and stacked over the pin, and electrically coupled to the pin. The second interconnects are disposed at a (N+2)th metal layer and stacked over the at least one first metal interconnect, and parallel to each other. The second metal interconnects are electrically coupled to the at least one first metal interconnect, and forming an equivalent tapping point of the pin of the cell block. The equivalent tapping point and the pin are vertically overlapped with each other, and fabrication of the device is initiated after a DRC or a SEM simulation test is passed. A first width of at least one first metal interconnect is different from a second width of one of the plurality of second metal interconnects. 
     Also disclosed is a device that includes a cell block, a tapping connector, and a second via. The cell block has a pin. The tapping connector is stacked above the pin and configured to form an equivalent tapping point of the pin. The tapping connector includes at least one first metal interconnect, at least one second metal interconnect, and a first via. The at least one first metal interconnect is disposed at a first metal layer, and is stacked over the pin and electrically coupled to the pin. The at least one second metal interconnect is disposed at a second metal layer above the first metal layer. The first via connects the at least one first metal interconnect to the at least one second metal interconnect. The second via connects the at least one first metal interconnect to the pin. The equivalent tapping point and the pin are vertically overlapped with each other, and fabrication of the device is initiated after a DRC or a SEM simulation test is passed. A first width of the at least one first metal interconnect is the same to a second width of the at least one second metal interconnect. 
     A method is also disclosed that includes the operations below. A standard cell layout having a pin and a tapping connector electrically coupled to the pin to form an equivalent tapping point of the pin is arranged. The interconnect-mesh includes at least one first metal interconnect and at least one second metal interconnect. A first via connects the at least one first metal interconnect to the at least one second metal interconnect, and a second via connects the at least one first metal interconnect to the pin. The at least one first metal interconnect is perpendicular to the pin. A semiconductor device is planned according to the standard cell layout. Fabrication of the semiconductor device is initiated after a DRC or a SEM simulation test is passed. The equivalent tapping point and the pin are vertically overlapped with each other. Arranging the standard cell layout includes arranging an interconnect-mesh stacked above the pin and electrically coupled to the pin. The at least one second metal interconnect and the at least one first metal interconnect extend in different directions. 
     The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.