Design rule constraints (DRC) are the industry workhorse for constraining design to ensure both physical and electrical
manufacturability. However, as technology processes continue to shrink and aggressive resolution enhancement
technologies (RET) and optical proximity correction (OPC) are applied, standard DRC sometimes fails to fully capture
the concept of design manufacturability. Consequently, some DRC-clean layout designs are found to be difficult to
manufacture. Attempts have been made to "patch up" standard DRC with additional rules to identify these specific
problematic cases. However, due to the lack of specificity with DRC, these efforts often meet with mixed-success.
Although it typically resolves the issue at hand, quite often, it is the enforcement of some DRC rule that causes other
problematic geometries to be generated, as designers attempt to meet all the constraints given to them. In effect,
designers meet the letter of the law, as defined by the DRC implementation code, without understanding the "spirit of the
rule". This leads to more exceptional cases being added to the DRC manual, further increasing its complexity.
DRC Plus adopts a different approach. It augments standard DRC by applying fast 2D pattern matching to design layout
to identify problematic 2D configurations which are difficult to manufacture. The tool then returns specific feedback to
designers on how to resolve these issues. This basic approach offers several advantages over other DFM techniques: It is
enforceable, it offers a simple pass/no-pass criterion, it is simple to document as part of the design manual, it does not
require compute intensive simulations, and it does not require highly-accurate lithographic models that may not be
available during design. These advantages allow DRC Plus to be inserted early in the design flow, and enforced in
conjunction with standard DRC.