Double Patterning Makes a Big Debut in Roadmap Aaron Hand, -- Semiconductor International, 2/1/2007 Given that this is an update year rather than a year for a new edition of the International Technology Roadmap for Semiconductors (ITRS), one wouldn't necessarily expect to see a lot of major changes. But the 2006 update of the Lithography chapter has the effects of one significant change written all over its pages, and that's the introduction of double patterning as a potential solution for furthering the resolution capabilities of 193 nm immersion lithography (193i). A possibility that has come on like gangbusters in the past year (see “Double Patterning Wrings More From Immersion Lithography ”), double patterning makes an appearance throughout the updated chapter — within Difficult Challenges, Technology Requirements, and Potential Solutions. The ITRS's Lithography technology working group (TWG) has deemed it appropriate to add 193i double patterning as a potential solution at both the 45 and 32 nm half-pitch. It's not a surprise, actually, that the technique — which basically splits a design into two masks to relax the pitch of the pattern — has been incorporated as a potential solution, given that the industry has been brimming with positive talk about its potential for at least a year. But it is not without its headaches, which is why double patterning also figures prominently in the Difficult Challenges section of the Lithography chapter. A double patterning section was dropped in below extreme ultraviolet (EUV) lithography, with double patterning difficult challenges listed as: Overlay of multiple exposures, including mask image placement. Availability of software to split the pattern, apply optical proximity correction (OPC), and verify the quality of the split while preserving critical features and maintaining no more than two exposures for arbitrary designs. Availability of high-productivity scanner, track and process to maintain low cost of ownership (CoO). Resists with independent exposure of multiple passes. Fab logistics and process control to enable low cycle time impact that include on-time availability of additional reticles and efficient scheduling of multiple exposure passes. Within the Technology Requirements section, double patterning makes an appearance in both the resist and the mask tables, where requirements have been added for the near-term and long-term years through 2020. Wafer backside particle density in photoresists for double patterning does not appear to be a particular issue, with manufacturable solutions existing even for the 0.14 defects/cm2 required for 2007 and beyond. However, the resist requirements table shows nothing but red from here on out for defect limits in spin-coated resist films for double patterning, with a stated requirement of 0.005 defects/cm2. There's an awful lot of red showing for the double patterning requirements added to the mask tables. Image placement for double patterning already hit the brick wall in 2006 at a requirement of 5.7 nm, multipoint, and continues on through 2020, when the requirement is expected to fall to 1.0 nm. Although interim solutions are known through 2008 for the difference in CD mean-to-target for two masks used as a double patterning set, it all turns to red from there on, as the requirement goes to 2 nm in 2009 and continues on down to 0.55 nm by 2020. A small number of other updates have been made to the chapter, particularly in color changes in the requirements tables that reflect improvements in the industry. http://www.semiconductor.net/article/CA6409511.html -- ◣ ◢ .. ◥S --

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