One of the major sources of yield loss is shorts between wires.
This failure mode is made more likely by the habit of designers and
design tools of running interconnect wires at or near the minimum
metal pitch. This may make sense at the time, conserving valuable
space for more wires later. But, this can leave the finished design
with tightly packed wiring next to empty space. Techniques for
spreading these wires into the empty space can result in
significant reductions in extra material critical area and
increases in yield. A simple technique that involves minimal
changes to the design is to search the layout for interconnect
wires that are next to some empty or "white space".
Wire spreading technique
Two layers can then be "added" to define a region to be removed
and a corresponding region to be added. These two regions define a
small displacement of the wire, reducing the critical area between
the interconnect. Note, this also reduces the capacitance of the
displaced nets.
