Knowledge Center

Knowledge Center

Design Rule Pattern Matching

Locating design rules using pattern matching techniques.


To help designers find complex features with a design implementation, physical verification and DFM tools may employ pattern matching techniques. That is, a designer can simply copy a particular feature (portion of a layout) that has been identified as a problem and place it into a pattern library. Then the DFM tool is instructed to search the entire layout for all instances of the pattern. Of course, the tool must be intelligent enough to account for different orientations and placements of the pattern, and even small variations in dimensions of the pattern, as specified by the designer. Once the problem features are identified, designers can take appropriate action to modify or eliminate them. Then can also employ the tool to make small changes to the pattern to make it legal according to a set of predefined rules.

Design constraints and influences have spread far beyond simple length/width measurements at 45 nm and below.

Pattern Matching replaces lengthy and multi-operational text-based design rules with an automated visual geometry capture and compare process that significantly reduces rule deck size and improves congruence between the original intent of the design specification and its implementation. The technology enables designers to implement complex design constraints, and also helps ensure uniformity and more streamlined communication between design, manufacturing and test teams. Because pattern matching is a direct visual comparison between actual geometries, accuracy and precision are increased, and debugging is greatly simplified.

Some typical features to look for in a pattern matching facility include:
• A drawing environment to allow designers to create and edit patterns from scratch
• Automated pattern capture patterns from an existing layout via a GUI
• Batch process that uses error markers from a DRC run to identify and capture problem patterns in one step
• Ability to specify exact match or add controlled variability with pattern constraints
• Ability to interoperate with all major design environments

The following benefits of using a pattern-based approach to DRC have been observed:
• Reducing time required for rule deck development by simplifying and automating the creation of complex physical verification or design methodology checks that were previously difficult or operationally impossible to create using text-based scripting.
• Reducing design variability by performing physical verification checks previously difficult or impossible to perform.
• Simplifying debugging by providing a direct visual comparison between actual geometries, making it much easier to understand and fix violations.
• Faster updates between manufacturing and design, enabling the quick accurate implementation of recently- identified yield-limiting patterns.
• Improving consistency and accuracy across flows and between teams by enabling design, manufacturing and test teams to share pattern libraries across multiple tools. Pattern libraries can be created for specific design methodologies, manufacturing processes, or other categorizations.
• Improving communication between designers and fab/foundry by using actual patterns (rather than text- based abstractions) to create complex checks.

Original page contents provided by Mentor Graphics

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