Abstract:
A multiple-patterned semiconductor device and a method of manufacture are provided. The semiconductor device includes one or more layers with signal tracks. The signal tracks have a quality characteristic. The semiconductor device also includes repeater banks to repower signals. The method of manufacture includes defining portions of layers with photomasks having signal track patterns, determining a quality characteristic of the signal track patterns, and selecting a photomask for etching vias.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of co-pending U.S. patent application Ser. No. 13/732,721, filed Jan. 2, 2013. The aforementioned related patent application is herein incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to a semiconductor device and method of manufacture and, more particularly, relates to a multiple-patterned semiconductor device. 
     BACKGROUND 
     The semiconductor industry is producing more and more capable components with smaller and smaller feature sizes. Due to the increased demand for highly integrated semiconductor devices, advanced techniques of fabricating more semiconductor devices in a smaller die area have become strongly relied upon. The production of such semiconductor devices reveals new design and manufacturing challenges to be addressed in order to maintain or improve semiconductor device performance. 
     As the device density of semiconductors increases, the conductor line width and spacing within the semiconductor devices decreases. Multiple-pattern lithography represents a class of technologies developed for photolithography to enhance the feature density of semiconductor devices. Double-patterning, a subset of multiple-patterning, may be used as early as the 45 nm node in the semiconductor industry and may be the primary technique for the 32 nm node and beyond. Double-patterning employs multiple masks and photolithographic steps to create a particular level of a semiconductor device. With benefits such as tighter pitches and narrower wires, double-patterning alters relationships between variables related to semiconductor device wiring and wire quality to sustain performance. 
     SUMMARY 
     In an embodiment, this disclosure relates to a multiple-patterned semiconductor device. The semiconductor device may include one or more layers. A particular level of the semiconductor device may include signal tracks defined by different masks and exposures. The signal tracks may have a quality characteristic. The semiconductor device may include repeater banks. The repeater banks may repower signals. The semiconductor device may achieve a timing tolerance standard. 
     In an embodiment, this disclosure relates to a method of manufacture for a multiple-patterned semiconductor device. The method of manufacture includes defining portions of layers. Photomasks having signal track patterns may be used to define the portions of the layers. The method may include determining a quality characteristic of the signal track patterns. The method may include selecting a photomask for etching vias. The method may achieve a signal travel path within a timing tolerance standard. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view showing double-patterned signal tracks carrying wires, connectors, and repeater banks pursuant to the disclosure; 
         FIG. 1B  is a planar view showing both an example signal path on wires that a signal may travel on double-patterned signal tracks and the relative location of repeater banks according to an embodiment of the disclosure; 
         FIG. 1C  is a planar view showing both an example signal path on wires that a signal may travel on double-patterned signal tracks and the relative location of repeater banks according to an embodiment of the disclosure; 
         FIG. 2  is a perspective view showing double-patterned signal tracks carrying wires, connectors, and repeater banks pursuant to the disclosure; 
         FIG. 3  is a perspective view showing double-patterned signal tracks carrying wires, connectors, and repeater banks pursuant to the disclosure; 
         FIG. 4A  is a cross-sectional view of a semiconductor device pre-exposure to a first mask and pre-exposure to a second mask pursuant to the disclosure; 
         FIG. 4B  is a cross-sectional view of a semiconductor device post-exposure to the first mask and pre-exposure to the second mask pursuant to the disclosure; 
         FIG. 4C  is a cross-sectional view of a semiconductor device post-exposure to both the first mask and to the second mask pursuant to the disclosure; 
         FIG. 4D  is a cross-sectional view of a semiconductor device post-development pursuant to the disclosure; 
         FIG. 5A  is a perspective view showing double-patterned signal tracks carrying wires, connectors, and repeater banks pursuant to the disclosure; 
         FIG. 5B  is a planar view showing both an example signal path on wires that a signal may travel on double-patterned signal tracks and the relative location of repeater banks according to an embodiment of the disclosure; 
         FIG. 5C  is a planar view showing both an example signal path on wires that a signal may travel on double-patterned signal tracks and the relative location of repeater banks according to an embodiment of the disclosure; 
         FIG. 5D  is a planar view showing both an example signal path on wires that a signal may travel on double-patterned signal tracks and the relative location of repeater banks according to an embodiment of the disclosure; 
         FIG. 6  is a flow chart showing an operation to choose via masks in accordance with an embodiment; and 
         FIG. 7  is a flow chart showing an operation to choose via masks in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     As conductor line width and pitch geometries decrease, the use of double-patterning on a particular level may increase in order to achieve the required conductor dimensions while still using existing state of the art lithographic exposure equipment. A benefit of double-patterning includes the ability to form tight conductor pitches; however, double-patterning may introduce other variables related to timing and noise into the semiconductor process. Double-patterns alter relationships between adjacent wires in both width and spacing. Adjacent wire channels may be defined in separate lithography steps. Distinctions between adjacent wires may arise due to lithographic exposure variations and registration or placement errors of one exposure relative to another. The need to design for non-optimal wires restricts semiconductor design variables, such as signal repeater spacing, which may affect semiconductor die size. 
     Single level patterning enables straightforward characterization of parameters with signal delay implications such as wire width, height, and spacing variations. A product of a resistance value (R) of a wire and a capacitance value (C) of the wire forms an RC time constant for the wire (note this is an approximation since the R and the C are distributed along the wire length). Historically, a decrease in wire width or thickness brings about a resistance increase and a corresponding capacitance decrease. The C decrease approximately offsets the R increase in the RC time constant. Such capacitance decrease occurs in part due to a reduction in lateral capacitance because the space between wires increases as wire width decreases. Similarly, an increase in wire width or thickness brings about a resistance decrease approximately offset in the RC time constant by a corresponding capacitance increase. Such a capacitance increase occurs in part due to a rise in lateral capacitance because the space between wires decreases as wire width increases. Thus, in conventional, single-patterned wires the RC time constant remains within appropriate limits of tolerance. 
     Double-patterning prompts a different nature of lateral capacitance relative to single level patterning. In double-patterning, the width of adjacent wires is rather independent, i.e., track poorly. Wire widths may not track well between adjacent wires created using separate exposures. Relatively narrow wires may be next to or between relatively wide wires. Double-patterning creates varying lateral capacitance between adjacent wires effectively separate from wire resistance variations. The resistance value (R) and the capacitance value (C) may fail to counterbalance each other across process variations. For example, a highly resistive wire may have high R and high C. Thus, the RC time constant between adjacent wires may vary significantly. Wires of one pattern of a double-pattern may carry a signal faster than wires of the other pattern. This may cause signals to reach their respective destinations at different times. Early analysis of a particular 14-15 nm technology indicates a potential doubling of worst case lateral capacitance between adjacent wires, doubling of coupled noise, and increased total wire C by as much as 50%. Such variations may require a solution to mitigate these effects. Potential solutions include repeaters more frequently placed or wires separated more. Such solutions may increase semiconductor die size. Increasing semiconductor die size may be discouraged and may negatively impact the ability to use such a semiconductor device in some systems. Using signal tracks from more than one pattern to carry a signal may achieve desirable results related to signal timing. 
     Given significant variations in a wire RC time constant, designing for a high RC time constant on both “A wires” and “B wires” may involve close signal repeater spacing. As only either the “A wires” or the “B wires” may be at the RC time constant limit of tolerance, mitigating the one of a higher RC time constant by reducing signal repeater spacing may suffice. This may reduce the excess margin required for spacing all signal repeaters at the high RC time constant wire driven limit. As the logic content of a die increases, on-chip communication requirements tend to grow exponentially in both the width of buses between die elements and the speed at which the buses must run. Reducing signal repeater spacing impacts designs by limiting the maximum sized unit that can be placed between repeater bays, which may complicate large block timing closure and increase die size. Maximizing signal repeater spacing may benefit semiconductor die size. 
     A semiconductor device may include a layer which may conduct a signal. Such a signal conductor layer may be multiple-patterned. In an embodiment, the layer may be double-patterned. Photolithography steps may involve separate masks including a first mask and a second mask. Adjacent wire channels may be defined with such separate masks in separate lithography steps. A first pattern with a wire channel may carry an “A wire” and a second pattern with a wire channel may carry a “B wire.” Wiring channels may alternate in layout for “A wires” and “B wires.” Thus, an “A wire” may exist between “B wires” and a “B wire” may exist between “A wires.” 
     A repeater may transfer a signal from a first signal track to a second signal track. As such, the repeater may transfer the signal from an “A wire” to a “B wire” or from a “B wire” to an “A wire.” The signal may be transferred multiple times in traveling from an origin to a destination. Signal paths may carry signals in part on fast wires and in part on slow wires. Signal paths may be transferred using vias and a higher level metal. Signal paths may criss-cross. Other possibilities for transferring signals are considered. 
     The repeater may repower the signal. The signal may be repowered multiple times in traveling from the origin to the destination. Two signals traveling from origins on “A wires” and “B wires” may each reach destinations to achieve a timing tolerance standard. The timing tolerance standard may include a difference from an amount of time for a first signal path and a second signal path to carry a signal a distance from the origin to the destination. The amount of time may be the expected time for the signal path to carry the signal the distance. The difference may be statistical or deterministic. The difference may be statistical when a signal path carries a signal on an equal number of “A wires” and “B wires.” The difference may be deterministic when a signal path carries a signal on an unequal number of “A wires” and “B wires,” such as embodiments where a signal path carries a signal on one more “A wire” or on one more “B wire.” In embodiments, at least one signal path may transfer or criss-cross without repowering. Other expected times and differences are considered. 
     Advanced semiconductor process technologies may utilize a dual damascene technique. With this technique, a metal trace may be defined before an underlying via to an underlying plane. The signal tracks may have a quality characteristic. Examples of the quality characteristic may be a size value, a width, an RC time constant value, or a time for a signal to travel a distance. A first quality characteristic may be considered substantially equal to a second quality characteristic if the values are within five percent of one another. 
     The width of the metal troughs for “A wires” and “B wires” may be measured. The width of the metal trough for an “A wire” may be the first quality characteristic and the width of the metal trough for a “B wire” may be the second quality characteristic. The measurement may occur before etching the metal troughs. The measurement may occur before etching the underlying vias. The connections below said metal wire may be modified by selecting one of various via level design reticles. Allowing a potential via in either of two or more locations that could connect to either of two or more potential signal repeaters may mitigate the effects of the high RC time constant, slower wire. In this case, the slower wire drives more closely spaced repeaters. 
       FIG. 1A  is a perspective view showing double-patterned signal tracks carrying wires, connectors, and repeater banks pursuant to the disclosure. Illustration  100  depicts a semiconductor device according to an embodiment. In  FIG. 1A , for example, signal tracks carrying “A wires”  101  (shown relatively wide) may be faster than signal tracks carrying “B wires”  102  (shown relatively narrow). The “A wires”  101  may have a shorter RC time constant than the “B wires”  102 . A signal track carrying an “A wire”  101  and signal track carrying a “B wire”  102  may be distanced by a signal track separation space  105 . 
     A repeater may exist with multiple repeater banks. A repeater bank may be synonymous with a repowering block. Each repeater bank may have a measurable area, FET width, transistor threshold voltage, and buffer strength. A first repeater bank  111  and a second repeater bank  112  may be distanced by a repeater bank separation space  115 . The repeater banks may each have an insulation  130 , a gate  131  or  132 , and source-drain areas  133 ,  135  or  134 ,  136 . In an embodiment, the first repeater bank  111  and the second repeater bank  112  may have equivalent areas, FET widths, transistor threshold voltages, and buffer strengths. 
     Vias may serve to connect wires and repeater banks. A first via input  121  may exist to join a previous wire segment to the first repeater bank  111 . A second via input  122  may exist to join a previous wire segment to the second repeater bank  112 . A first via output  123  may exist to join the first repeater bank  111  to a next wire segment. A second via output  124  may exist to join the second repeater bank  112  to a next wire segment. In an embodiment, the inputs  121 ,  122  and the outputs  123 ,  124  of the repeater banks  111 ,  112  may be alternated by one signal track. In other embodiments, inputs such as  121 ,  122  and outputs such as  123 ,  124  may be arranged an odd number of signal tracks apart. Other possibilities are considered with other embodiments. 
       FIG. 1B  is a planar view showing both an example signal path on wires that a signal may travel on double-patterned signal tracks and the relative location of repeater banks according to an embodiment of the disclosure. In  FIG. 1B , for example, signal tracks carrying “A wires”  101  may be faster than signal tracks carrying “B wires”  102 . The “A wires”  101  may have a shorter RC time constant than the “B wires”  102 . The wires may be in segments shown in  FIG. 1B  as  101 A,  101 B,  101 C,  101 D,  101 E for “A wires” and  102 A,  102 B,  102 C,  102 D,  102 E for “B wires.” 
     A signal track carrying a wire may have a signal path transferred to another signal track carrying a wire at each repeater bank. In an embodiment, the signal path may be alternated by one signal track. The signal path may alternate between “A wires”  101  and “B wires”  102 , transferring at repeater banks. In other embodiments, the signal path on “A wires”  101  and “B wires”  102  may be staggered in different ways such as an arrangement where signal paths include signal tracks where the transfer of a signal is to a signal track an odd number away. As in  FIG. 1B , the effect is that signal paths carrying signals may weave back and forth between “A wires”  101  and “B wires”  102 , repowering at repeater banks along the way. 
     As depicted in  FIG. 1B , the signal path of example signal  141  may originate on an “A wire”  101 A, transfer using repeater bank  141 AB to a “B wire”  102 B, transfer using repeater bank  141 BC to an “A wire”  101 C, transfer using repeater bank  141 CD to a “B wire”  102 D, and transfer using repeater bank  141 DE to an “A wire”  101 E where signal  141  ultimately reaches its destination. Similarly, the signal path of example signal  142  may originate on a “B wire”  102 A, transfer using repeater bank  142 AB to an “A wire”  101 B, transfer using repeater bank  142 BC to a “B wire”  102 C, transfer using repeater bank  142 CD to an “A wire”  101 D, and transfer using repeater bank  142 DE to a “B wire”  102 E where signal  142  ultimately reaches its destination. 
     Two signal paths, each carrying a signal, traveling on an equal number of “A wires”  101  and “B wires”  102  may result in the signals traveling the same distance in a nearly equivalent amount of time as each other. A signal traversing in an alternating fashion between “A wires”  101  and “B wires”  102  may arrive at the destination at a time nearly equivalent to a signal traversing in an alternating fashion between “B wires”  102  and “A wires”  101 . As in illustration  140 , signals  141  and  142  will reach their destinations at nearly the same time, having traveled on fast wires  101  and slow wires  102  the same distances (plus or minus the length of one wire segment). Such signal travel may occur without excessively stressing a high RC wire. 
       FIG. 1C  is a planar view showing both an example signal path on wires that a signal may travel on double-patterned signal tracks and the relative location of repeater banks according to an embodiment of the disclosure. In  FIG. 1C , for example, signal tracks carrying “A wires”  101  may be faster than signal tracks carrying “B wires”  102 . The “A wires”  101  may have a shorter RC time constant than the “B wires”  102 . The wires may be in segments shown in illustration  170  as  101 A,  101 B,  101 C,  101 D,  101 E for “A wires” and  102 A,  102 B,  102 C,  102 D,  102 E for “B wires.” 
     A signal track carrying a wire may have a signal path transferred to another signal track carrying a wire at each repeater bank. In an embodiment, the signal path may be alternated by one signal track. The signal path may alternate between “A wires”  101  and “B wires”  102 , transferring at repeater banks. In other embodiments, the signal path on “A wires”  101  and “B wires”  102  may be staggered in different ways such as an arrangement where signal paths include signal tracks where the transfer of a signal is to a signal track an odd number away. As in  FIG. 1C , the effect is that signal paths carrying signals may weave back and forth between “A wires”  101  and “B wires”  102 , repowering at repeater banks along the way. 
     As depicted in  FIG. 1C , the signal path of example signal  171  may originate on an “A wire”  101 A, transfer using repeater bank  171 AB to a “B wire”  102 B, transfer using repeater bank  171 BC to an “A wire”  101 C, transfer using repeater bank  171 CD to a “B wire”  102 D, and transfer using repeater bank  171 DE to an “A wire”  101 E where signal  171  ultimately reaches its destination. Similarly, the signal path of example signal  172  may originate on a “B wire”  102 A, transfer using repeater bank  172 AB to an “A wire”  101 B, transfer using repeater bank  172 BC to a “B wire”  102 C, transfer using repeater bank  172 CD to an “A wire”  101 D, and transfer using repeater bank  172 DE to a “B wire”  102 E where signal  172  ultimately reaches its destination. 
     Two signal paths, each carrying a signal, traveling on an equal number of “A wires”  101  and “B wires”  102  may result in the signals traveling the same distance in a nearly equivalent amount of time as each other. A signal traversing in an alternating fashion between “A wires”  101  and “B wires”  102  may arrive at the destination at a time nearly equivalent to a signal traversing in an alternating fashion between “B wires”  102  and “A wires”  101 . As in  FIG. 1C , signals  171  and  172  will reach their destinations at nearly the same time, having traveled on fast wires  101  and slow wires  102  the same distances (plus or minus the length of one wire segment). Such signal travel may occur without excessively stressing a high RC wire. 
     The magnitude of the RC time constant may correlate to the magnitude of delay with a changing wire length. Signal delay on a signal path may correlate to the square of the wire length needed for the signal to traverse a distance. Reducing repeater spacing may reduce the wire component of the RC time constant by the square of the ratio of the reduced repeater spacing and the original repeater spacing. The wire may extend the distance of the original repeater spacing. The capacitance component may fail to experience a reduction. Allowing the higher RC wires to be more closely spaced than the better quality wires nets a larger average spacing between repeaters. As discussed above, a larger average spacing between repeaters may benefit the die size and permit more design variables. Such spacing may positively impact the semiconductor device as a whole. 
       FIG. 2  is a perspective view showing double-patterned signal tracks carrying wires, connectors, and repeater banks pursuant to the disclosure. Illustration  200  depicts a semiconductor device according to an embodiment. Aspects of the embodiment depicted in  FIG. 2  are similar or the same as depicted in illustration  100 . In illustration  200 , for example, signal tracks carrying “B wires”  202  may be faster than signal tracks carrying “A wires”  201 . The “B wires”  202  may have a shorter RC time constant than the “A wires”  201 . 
     Vias may serve to connect wires and repeater banks. A first via input  221  may exist to join a previous wire segment to the first repeater bank  111 . A second via input  222  may exist to join a previous wire segment to the second repeater bank  112 . A first via output  223  may exist to join the first repeater bank  111  to a next wire segment. A second via output  224  may exist to join the second repeater bank  112  to a next wire segment. In an embodiment, the inputs  221 ,  222  and the outputs  223 ,  224  of the repeater banks  111 ,  112  may be alternated by one signal track. In other embodiments, inputs such as  221 ,  222  and outputs such as  223 ,  224  may be arranged an odd number of signal tracks apart. Other possibilities are considered with other embodiments. 
       FIG. 3  is a perspective view showing double-patterned signal tracks carrying wires, connectors, and repeater banks pursuant to the disclosure. Illustration  300  depicts a semiconductor device according to an embodiment. Aspects of the embodiment depicted in illustration  300  may be similar or the same as depicted in illustrations  100 ,  200 . In illustration  300 , for example, signal tracks carrying “A wires”  301  may be equivalent in speed to signal tracks carrying “B wires”  302 . The “A wires”  301  may be equivalent in RC to the “B wires”  302 . 
     Vias may serve to connect wires and repeater banks. A first via input  321  may exist to join a previous wire segment to the first repeater bank  111 . A second via input  322  may exist to join a previous wire segment to the second repeater bank  112 . A first via output  323  may exist to join the first repeater bank  111  to a next wire segment. A second via output  324  may exist to join the second repeater bank  112  to a next wire segment. In an embodiment, the inputs  321 ,  322  and the outputs  323 ,  324  of the repeater banks  111 ,  112  may be alternated by one signal track. In other embodiments, inputs such as  321 ,  322  and outputs such as  323 ,  324  may be arranged an odd number of signal tracks apart. If the wires are equivalent in RC, illustrations such as  100 ,  200  may also succeed and the connections may be discretionary. Other possibilities are considered with other embodiments. 
     Connections may be made at a different pattern design levels or layers according to embodiments. Transfer of signals may occur between multiple layers. Repowering may occur in this context as well. A signal may transfer from a signal track on a first signal conductor layer to a signal track on a second signal conductor layer using vias and higher level metals or other techniques. The transfer may occur in a similar fashion as shown in illustrations  100 ,  140 ,  170 ,  200 ,  300 . As such, the signal may be transferred multiple times in traveling from an origin to a destination. Such back and forth between signal tracks carrying slow wires and fast wires may occur across the semiconductor device between multiple layers. Other configurations and possibilities are considered with other embodiments. 
       FIG. 4A  is a cross-sectional view of a semiconductor device pre-exposure to a first mask and pre-exposure to a second mask pursuant to the disclosure. To form a semiconductor device, an interlayer insulating film  402  may be formed on a semiconductor substrate  401  in which various components are to be formed. A photoresist  403  may then be coated on the interlayer insulating film  402 . Advanced semiconductor process technologies may utilize a dual damascene technique. With this technique, the metal trace may be defined before the underlying via to the underlying plane. A first mask  411  may be used to define a first signal track set and a second mask  422  may be used to define a second signal track set. 
       FIG. 4B  is a cross-sectional view of a semiconductor device post-exposure to the first mask and pre-exposure to the second mask pursuant to the disclosure. The first mask  411  may define the first signal track set on the photoresist  403  through exposure. A photoresist  413  post-exposure to the first mask may have the first signal track set defined. 
       FIG. 4C  is a cross-sectional view of a semiconductor device post-exposure to both the first mask and to the second mask pursuant to the disclosure. The second mask  422  may define the second signal track set on the photoresist  413  through exposure. A photoresist  423  post-exposure to the second mask may have the second signal track set defined. 
       FIG. 4D  is a cross-sectional view of a semiconductor device post-development pursuant to the disclosure. A photoresist  433  post-development may have both the first signal track set and the second signal track set ready to be measured. The width of the metal troughs for “A wires” and “B wires” may be measured on the photoresist  433 . The measurement may occur after the photoresist has been developed and processed. Processing may include removing portions of the photoresist that were exposed. The measurement may occur before etching the metal troughs. The measurement may occur before etching the underlying vias. Via locations may be decided before etching. The dominant variable of the variation in trough width may be due to the exposure. In  FIG. 4D , for example, channels developed for “A wires” with a first width  441  may be faster than channels developed for “B wires” with a second width  442  because the first width  411  may be greater than the second width  412 . In some embodiments, after etching the metal troughs, measurement may occur again before etching the underlying vias. 
       FIG. 5A  is a perspective view showing double-patterned signal tracks carrying wires, connectors, and repeater banks pursuant to the disclosure. Aspects of the semiconductor device depicted in illustration  500  may be similar or the same as depicted in illustrations  100 ,  140 ,  170 ,  200 ,  300 ,  400 . In illustration  500 , for example, signal tracks carrying “A wires”  101  may be faster than signal tracks carrying “B wires”  102 . The “A wires”  101  may have a shorter RC time constant than the “B wires”  102 . A first repeater bank  511  and a second repeater bank  512  may be distanced by a repeater bank separation space  515 . The repeater bank separation space  515  may be as small as possible. For example, the repeater bank separation space  115  in illustrations  100 ,  140 ,  170 ,  200 ,  300 ,  400  may be 30 microns whereas the repeater bank separation space  515  in illustration  500  may be 1 micron. 
     A buffer strength may indicate the ability of a repeater to boost a signal over a distance from an origin to a destination. The buffer strength of a strong repeater bank may be fifty percent stronger than a weak repeater bank. In an embodiment, the first repeater bank  511  and the second repeater bank  512  may have different buffer strengths. A greater buffer strength may successfully drive a signal over a length of a particular wire in a specified time. In illustration  500 , the buffer strength of the first repeater bank  511  connected to a signal track carrying a fast wire  101  may be weaker than the buffer strength of the second repeater bank  512  connected to a signal track carrying a slow wire  102 . 
     In an embodiment, the different buffer strengths of the first repeater bank  511  and the second repeater bank  512  may result from making FET widths different or establishing different transistor threshold voltages for each repeater bank. The width of a repeater bank connected to a signal track with a slow wire may be larger relative to a FET width of a repeater bank connected to a signal track with a fast wire. A threshold voltage is the voltage at which there are sufficient electrons in to make a low resistance conducting path. Reducing a transistor threshold voltage of a repeater bank may increase the buffer strength of the bank. The transistor threshold voltage of a repeater bank connected to a signal track with a slow wire may be reduced relative to that of a repeater bank connected to a signal track with a fast wire. As depicted in illustration  500 , repeater bank  512  may have a wider FET width or a reduced transistor threshold voltage relative to that of repeater bank  511 . Thus, the buffer strength of the repeater bank  511  connected to a signal track with a fast wire  101  may be weaker than the buffer strength of the repeater bank  512  connected to a signal track with a slow wire  102 . 
     In an embodiment, the different buffer strengths of the first repeater bank  511  and the second repeater bank  512  may result from establishing different areas for each repeater bank. The area may be directly proportional to a quantity of repeater finger connectors, hence affecting the buffer strength. Reducing the area of a repeater bank may decrease the buffer strength of the repeater bank. Enlarging the area of a repeater bank may increase the buffer strength of the repeater bank. Reducing the area of a first repeater bank may offset enlarging the area of second repeater bank. The total area of the two repeater banks as a whole may change insubstantially in modifying the area of each repeater bank individually. The area of the first repeater bank  511  connected to a signal track with a fast wire  101  may be reduced relative to that of the second repeater bank  512  connected to a signal track with a fast wire  102 . In an embodiment, the first repeater bank  511  may have fewer repeater finger connectors than the second repeater bank  512 . Thus, the buffer strength of the repeater bank  511  connected to a signal track with a fast wire  101  may be weaker than the buffer strength of the repeater bank  512  connected to a signal track with a slow wire  102 . 
       FIG. 5B  is a planar view showing both an example signal path on wires that a signal may travel on double-patterned signal tracks and the relative location of repeater banks according to an embodiment of the disclosure. Aspects of the semiconductor device depicted in  FIG. 5B  may be similar or the same as depicted in  FIGS. 1A-5A . In  FIG. 5B , for example, signal tracks carrying “A wires”  101  may be faster than signal tracks carrying “B wires”  102 . The “A wires”  101  may have a shorter RC time constant than the “B wires”  102 . The wires may be in segments shown in  FIG. 5B  as  101 A,  101 B,  101 C,  101 D,  101 E for “A wires” and  102 A,  102 B,  102 C,  102 D,  102 E for “B wires.” The segment lengths may be of a substantially equal length. A substantially equal length may be a length of a first segment within ten percent of a length of a second segment. Selected vias  546  for a weaker repeater bank  541 AB and selected vias  547  for a stronger repeater bank  542 AB are shown in  FIG. 5B . The vias  546 ,  547  may be chosen to connect signal tracks of a given RC time constant with repeater banks of a given strength. The needed strength or weakness selection and appropriate via connection may be done based on determination, by measurement, of trench widths. The trench will be filled with metal to make an “A wire” or a “B wire.” 
     A signal track carrying a wire may have a signal path transferred to another signal track carrying a wire at each repeater bank. In an embodiment, the signal path may be alternated by two signal tracks. The signal path may alternate between different “A wires”  101  or different “B wires”  102 , transferring at repeater banks. In other embodiments, the signal path on “A wires”  101  and “B wires”  102  may be staggered in different ways such as an arrangement where signal paths include signal tracks where the transfer of a signal is to a signal track an even number away. As in  FIG. 5B , the effect is that signal paths carrying signals may weave back and forth between different “A wires”  101  or different “B wires”  102 , repowering at repeater banks along the way. 
     In an embodiment, the repeater banks may have different buffer strengths. The different buffer strengths may result from establishing different FET widths or transistor threshold voltages for each repeater bank.  FIG. 5B  depicts signal  541  traveling on “A wires” and signal  542  traveling on “B wires.” The signal may repower at repeater banks along the way. Repeater banks  541 AB,  541 BC,  541 CD, and  541 DE may be weaker repeater banks connected to signal tracks with fast wires  101  and repeater banks  542 AB,  542 BC,  542 CD, and  542 DE may be stronger repeater banks connected to signal tracks with slow wires  102 . The FET widths of repeater banks connected to signal tracks with slow wires  102  may be larger relative to that of repeater banks connected to signal tracks with fast wires  101 . Alternatively, the transistor threshold voltage of repeater banks connected to signal tracks with slow wires  102  may be reduced relative to that of repeater banks connected to signal tracks with fast wires  101 . In such embodiment, a signal traveling on “A wires”  101  may arrive at the final destination at a time statistically equivalent to a signal traveling on “B wires”  102 . 
     As depicted in  FIG. 5B , the signal path of example signal  541  may originate on an “A wire”  101 A, transfer using weaker repeater bank  541 AB to an “A wire”  101 B, transfer using weaker repeater bank  541 BC to an “A wire”  101 C, transfer using weaker repeater bank  541 CD to an “A wire”  101 D, and transfer using weaker repeater bank  541 DE to an “A wire”  101 E where signal  541  ultimately reaches its destination. Similarly, the signal path of example signal  542  may originate on a “B wire”  102 A, transfer using stronger repeater bank  542 AB to a “B wire”  102 B, transfer using stronger repeater bank  542 BC to a “B wire”  102 C, transfer using stronger repeater bank  542 CD to a “B wire”  102 D, and transfer using stronger repeater bank  542 DE to a “B wire”  102 E where signal  542  ultimately reaches its destination. 
       FIG. 5C  is a planar view showing both an example signal path on wires that a signal may travel on double-patterned signal tracks and the relative location of repeater banks according to an embodiment of the disclosure. Aspects of the semiconductor device depicted in  FIG. 5C  may be similar or the same as depicted in  FIGS. 1A-5B .  FIG. 5B  and  FIG. 5C  may differ only by repeater bank areas. In  FIG. 5C , for example, signal tracks carrying “A wires”  101  may be faster than signal tracks carrying “B wires”  102 . The “A wires”  101  may have a shorter RC time constant than the “B wires”  102 . The wires may be in segments shown in  FIG. 5C  as  101 A,  101 B,  101 C,  101 D,  101 E for “A wires” and  102 A,  102 B,  102 C,  102 D,  102 E for “B wires.” The segment lengths may be of a substantially equal length. A substantially equal length may be a length of a first segment within ten percent of a length of a second segment. Selected vias  576  for a weaker repeater bank  571 AB and selected vias  577  for a stronger repeater bank  572 AB are shown in  FIG. 5B . The vias  576 ,  577  may be chosen to connect signal tracks of a given RC time constant with repeater banks of a given strength. The needed strength or weakness selection and appropriate via connection may be done based on determination, by measurement, of trench widths. The trench will be filled with metal to make an “A wire” or a “B wire.” 
     A signal track carrying a wire may have a signal path transferred to another signal track carrying a wire at each repeater bank. In an embodiment, the signal path may be alternated by two signal tracks. The signal path may alternate between different “A wires”  101  or different “B wires”  102 , transferring at repeater banks. In other embodiments, the signal path on “A wires”  101  and “B wires”  102  may be staggered in different ways such as an arrangement where signal paths include signal tracks where the transfer of a signal is to a signal track an even number away. As in  FIG. 5C , the effect is that signal paths carrying signals may weave back and forth between different “A wires”  101  or different “B wires”  102 , repowering at repeater banks along the way. 
     In an embodiment, the repeater banks may have different buffer strengths. The different buffer strengths may result from establishing different areas for each repeater bank.  FIG. 5C  depicts signal  571  traveling on “A wires” and signal  572  traveling on “B wires.” The signal may repower at repeater banks along the way. Repeater banks  571 AB,  571 BC,  571 CD, and  571 DE may be weaker repeater banks connected to signal tracks with fast wires  101  and repeater banks  572 AB,  572 BC,  572 CD, and  572 DE may be stronger repeater banks connected to signal tracks with slow wires  102 . The area of repeater banks connected to signal tracks with slow wires  102  may be greater than that of repeater banks connected to signal tracks with fast wires  101 . In such embodiment, a signal traveling on “A wires”  101  may arrive at the final destination at a time statistically equivalent to a signal traveling on “B wires”  102 . 
     As depicted in  FIG. 5C , the signal path of example signal  571  may originate on an “A wire”  101 A, transfer using weaker repeater bank  571 AB to an “A wire”  101 B, transfer using weaker repeater bank  571 BC to an “A wire”  101 C, transfer using weaker repeater bank  571 CD to an “A wire”  101 D, and transfer using weaker repeater bank  571 DE to an “A wire”  101 E where signal  571  ultimately reaches its destination. Similarly, the signal path of example signal  572  may originate on a “B wire”  102 A, transfer using stronger repeater bank  572 AB to a “B wire”  102 B, transfer using stronger repeater bank  572 BC to a “B wire”  102 C, transfer using stronger repeater bank  572 CD to a “B wire”  102 D, and transfer using stronger repeater bank  572 DE to a “B wire”  102 E where signal  572  ultimately reaches its destination. 
       FIG. 5D  is a planar view showing both an example signal path on wires that a signal may travel on double-patterned signal tracks and the relative location of repeater banks according to an embodiment of the disclosure. Aspects of the semiconductor device depicted in  FIG. 5D  may be similar or the same as depicted in  FIGS. 1A-5C . FIG. In  FIG. 5C , for example, signal tracks carrying “A wires”  101  may be substantially equal in speed to signal tracks carrying “B wires”  102 . The “A wires”  101  may have a substantially equal RC time constant compared to the “B wires”  102 . The wires may be in segments shown in  FIG. 5D  as  101 A,  101 B,  101 C,  101 D,  101 E for “A wires” and  102 A,  102 B,  102 C,  102 D,  102 E for “B wires.” The segment lengths may be of a substantially equal length. A substantially equal length may be a length of a first segment within ten percent of a length of a second segment. Selected vias  596  for a stronger repeater bank  591 AB and selected vias  597  for a weaker repeater bank  592 AB are shown in  FIG. 5D . The vias  596 ,  597  may be chosen to connect signal tracks of a given RC time constant with repeater banks of a given strength. The needed strength or weakness selection and appropriate via connection may be done based on determination, by measurement, of trench or trough widths. The trench or trough will be filled with metal to make an “A wire” or a “B wire.” 
     A signal track carrying a wire may have a signal path transferred to another signal track carrying a wire at each repeater bank. The signal path may alternate between different “A wires”  101  or different “B wires”  102 , transferring at repeater banks. In other embodiments, the signal path on “A wires”  101  and “B wires”  102  may be staggered in different ways. As in  FIG. 5D , the effect is that signal paths carrying signals may weave back and forth between different “A wires”  101  or different “B wires”  102 , repowering at repeater banks along the way. In an embodiment, the repeater banks may have different buffer strengths with signals able to repower at repeater banks along the way. Repeater banks  591 AB,  591 BC,  591 CD, and  591 DE may be stronger repeater banks and repeater banks  592 AB,  592 BC,  592 CD, and  592 DE may be weaker repeater banks. In such embodiment, signal  591  may arrive at the final destination at a time statistically equivalent to signal  592 . 
     As depicted in  FIG. 5D , the signal path of example signal  591  may originate on an “A wire”  101 A, transfer using stronger repeater bank  591 AB to an “A wire”  101 B, transfer using weaker repeater bank  592 BC to an “A wire”  101 C, transfer using stronger repeater bank  591 CD to an “A wire”  101 D, and transfer using weaker repeater bank  592 DE to an “A wire”  101 E where signal  591  ultimately reaches its destination. Similarly, the signal path of example signal  592  may originate on a “B wire”  102 A, transfer using weaker repeater bank  592 AB to a “B wire”  102 B, transfer using stronger repeater bank  591 BC to a “B wire”  102 C, transfer using weaker repeater bank  592 CD to a “B wire”  102 D, and transfer using stronger repeater bank  591 DE to a “B wire”  102 E where signal  592  ultimately reaches its destination. 
     Two signal paths, each carrying a signal, traveling on “A wires”  101  and “B wires”  102  with stronger and weaker repeater banks may result in the signals traveling the same distance in a nearly equivalent amount of time as each other.  FIG. 5B ,  FIG. 5C , and  FIG. 5D  show first signals  541 ,  571 ,  591  and second signals  542 ,  572 ,  592  may arrive at the destination at a nearly equivalent time. Such signal travel may occur without excessively stressing a high RC wire. 
     Aspects of the semiconductor device as depicted in  FIGS. 1A-5D  may include other characteristics according to other embodiments. Connections may be made at a different pattern design levels or layers according to embodiments. Signal paths may include multiple layers. Repowering may occur on multiple layers in this context as well. A signal may transfer from a signal track on a first signal conductor layer to a signal track on a second signal conductor layer using vias and higher level metals or other techniques. The transfer may occur in a similar fashion as shown in the illustrations. As such, the signal may be transferred multiple times in traveling from an origin to a destination. Such back and forth between signal tracks may occur across the semiconductor device between multiple layers. Other configurations and possibilities are considered with other embodiments. 
       FIG. 6  is a flow chart showing an operation to choose via masks in accordance with an embodiment. Wire channels or tracings for wire channels created by masks for “A wires” and “B wires” may be measured as in block  610 . A measurement in block  610  may include measuring the width of a trench or trough. Trench, trough, and channel may be synonymous. The measurement in block  610  may be performed before a via etch. The measurement in block  610  may be performed before via or metal depositions. Measurements from block  610  may be used to compare channels created by masks for “A wires” and “B wires” in block  620 . The largest measurement from block  610  of the width of a trench or trough may be considered faster in decision block  620 . The smallest measurement from block  610  of the width of a trench or trough may be considered slower in decision block  620 . Thus, a channel with a larger width may be faster than a channel with a smaller width. 
     In an embodiment, a via mask may be chosen based on a comparison of channels. Via etching may occur in accordance with embodiments as described in  FIGS. 1A-5D . If channels for “A wires” are larger than channels for “B wires” then an “A faster than B” via mask may be used as in block  631 . Through use of an “A faster than B” via mask, vias may be etched in accordance with semiconductor device wiring  100  as in block  641 . If channels for “B wires” are larger than channels for “A wires” then a “B faster than A” via mask may be used as in block  632 . Through use of a “B faster than A” via mask, vias may be etched in accordance with semiconductor device wiring  200  as in block  642 . If channels for “A wires” are equal to channels for “B wires” then an “A equals B” via mask may be used as in block  633 . Through use of an “A equals B” via mask, vias may be etched in accordance with semiconductor device wiring  300  as in block  643 . 
       FIG. 7  is a flow chart showing an operation to choose via masks in accordance with an embodiment. Operation  700  is similar to operation  600 . Operation  700  may differ from operation  600  after decision block  620 . Via masks as in blocks  731 ,  732 ,  733  may differ from via masks of blocks  631 ,  632 ,  633  of operation  600 . Via etching may occur in accordance with a semiconductor device wiring utilizing buffers of different strengths as in blocks  741 ,  742 ,  743  similar to illustration  500 . 
     If channels for “A wires” are larger than channels for “B wires” then an “A faster than B” via mask may be used as in block  731 . Through use of an “A faster than B” via mask, vias may be etched in accordance with illustration  500  as in block  741 . Vias may connect the faster “A wires” to weaker buffers and the slower “B wires” to stronger buffers as described in block  741 . If channels for “B wires” are larger than channels for “A wires” then a “B faster than A” via mask may be used as in block  732 . Through use of a “B faster than A” via mask, vias may be etched with similar methodology to illustration  500  as in block  742 . Vias may connect the faster “B wires” to weaker buffers and the slower “B wires” to stronger buffers as described in block  741 . If channels for “A wires” are equal to channels for “B wires” then an “A equals B” via mask may be used as in block  733 . Through use of an “A equals B” via mask, vias may be etched with similar methodology to illustration  300 . Vias may alternate connecting wires with buffers of different strengths as in block  743  so that the signals reach the final destination at the same time. Other embodiments and variations on embodiments are contemplated.