Double patterning at 20nm is one of those big unavoidable changes that it is almost impossible to know too much about. Mentor’s David Abercrombie, DFM Program Manager for Calibre, has written a series of articles detailing the multifaceted impacts of double patterning on advanced node design and verification. There is a pdf that gives an introduction and a link to each article here.
Treat this as an advanced tutorial on the issues of double patterning, in particular the different approaches that different companies are deciding to take. Do you want your designers to see the two colors on the mask or leave it up to either specialists or the foundry? Do you want designers to be able to seed double patterning, which can be important in analog to guarantee better control over some of the parasitics.
David won the award for the best tutorial at the 2012 TSMC OIP for his presentation, along with Peter Hsu of TSMC, on Finding and Fixing Double Patterning Errors in 20nm. This pretty much summarizes what everyone has to become aware of the lower layers of 20nm.
Of course, since David works for Mentor, the solutions are all positioning Calibre’s capabilities. But the pieces mostly don’t mention Calibre and are general tutorials on double patterning that do not depend on the tool flow that you are using. After all, double patterning is a lithography problem requiring doubled up masks for some layers, and the fundamental problem doesn’t depend on the tool flow you take to get to a solution. If you are doing 20nm layout, you need to have at least a working knowledge of this stuff.
The different pieces that go to make up the whole tutorial are:
- Double Patterning Requires a Double Take
- Double Patterning: Sharing the Benefit and the Burden
- Debugging Double Patterning without Getting Double Vision
- To Cut or Not To Cut? That is the Double Patterning Question
- Colorblind—Colorless versus Two-Color Double Patterning Design
- Anchors Away – Anchoring and Seeding in Double Pattern Design
- Monsters, Inc.: How Do I Fix These Double Patterning Errors Anyway?
- Double Patterning: Challenges and Possible Solutions in Parasitics Extraction
- Why do my DP colors keep changing?
I fully recommend reading the entire summary if not all of David’s articles that the summary links to. Again, the document (pdf) is here.