layout for signal lines
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Guidelines for the Layout of Signals
• Choose routing layers based on process parameters and circuit requirements.
For each process a standardized list of routing layers should be determined
based on layer resistance and capacitance. Layers such as N-well, active, and
high-resistance poly gate are not used for routing. Priorities between routing
layers can also be standardized using the same criteria.
• Minimize the width of input signals. Minimizing the routing of the signals
within the design is also important. This reduces the input capacitance for
the signal. This is important for signals that are part of cells that are used
many times. An example of this would be a clock signal within a cell.
• Choose routing width carefully. The choice of the width of a routing signal
should be made judiciously. It is tempting to simply use the minimum design
rule line width as the routing width. This is not practical in all cases because
connections must be made to every line.