BACUS: DFEB mask, EUV gets Brion boost


At the Annual SPIE/BACUS Symposium 2010 (Sept. 13-16), the eBeam Initiative had several members jointly presenting the latest achievements related to an design for e-beam (DFEB) manufacturing approach, showing the effectiveness of DFEB mask technology on advanced photomasks at the 22nm node and beyond.

A key demonstration at BACUS was the first demonstration of improved shot count results of writing curvilinear features using overlapping e-beam shots, Aki Fujimura, CEO of D2S and managing sponsor of the Initiative, told SST. "Due to the collaborative efforts of the eBeam Initiative members, we continue to make progress on the DFEB mask technology roadmap," he said.

For 22nm process technologies, the ability to use curvilinear features for mask lithography becomes critical. DFEB mask technology makes cost-effective, optical lithography for 22nm a reality by leveraging the rounding nature of e-beams to enable practical turnaround times for complex and curvilinear features. The collaborative results from the eBeam Initiative members further demonstrate the ability of DFEB mask technology to enable fewer shot counts and less write-time than traditional e-beam writing techniques on advanced photomasks.

Also at BACUS, Brion Technologies debuted its Tachyon NXE software to optimize predictive modeling for parent company ASML's extreme ultraviolet (EUV) scanners, claiming it can reduce development time and cost to produce chips on the EUV systems.

Left: Circular and variable shaped beam (VSB) shots used to shoot an inverse lithography technology (ILT) mask for a contact layer at the 22nm logic node incorporating circular and curvilinear features using design for e-beam (DFEB) mask technology. Right: VSB shots used to shoot a Manhattanized ILT mask with rectangular main features using DFEB mask technology. This mask would produce nearly identical wafer lithography quality as the mask printing at left. Using D2S' Model-Based Mask Data Preparation (MB-MDP) engine, this pattern is produced with 402 overlapping VSB shots versus 620 VSB shots with conventional fracturing. Only rectangular VSB shots are used.

The Tachyon NXE software package integrates with existing Tachyon products to enable EUV lithography process simulation. To develop the EUVL simulation models, TwinScan NXE:3100 scanner characteristics were incorporated to model the optical performance. By simulating the behavior of the new scanner, Tachyon NXE can efficiently predict and correct NXE-specific effects before the start of chip production, helping to decrease EUV mask re-spins and shorten the learning cycles during final mask development.

Brion's applications for optical proximity correction (Tachyon OPC+) and lithography manufacturability check (Tachyon LMC) can now incorporate the new software model of ASML's EUV pre-production scanners, six of which are slated to ship before mid-2011, and have been optimized for EUV requirements of accuracy, file size and run-time. In multiple DRAM test cases, the company says it has demonstrated the capability to perform full-field (~8cm2) EUV mask data correction in less than eight hours on a single Tachyon system.

Accurate models across the full imaging field, as well as acceptable run times and file size, are key end user requirements, Jim Koonmen, GM of Brion, tells SST. But full-field is the key new requirement with EUV—and in turn, it drives acceptable run times and file sizes. The full-field nature of EUV makes the job more complex because the imaging performance can vary across the scanner's full imaging field. For example, flare (i.e., stray light) varies across the scanner's field. In immersion scanners, flare is insignificant. In EUVL, however, flare becomes a more substantial effect that is driven by attributes of the EUV mask and EUV scanner. These attributes lead to a nonhomogeneous distribution of flare across the imaging field, says Koonmen. If not dealt with appropriately, each chip in the imaging field may require its own unique correction, thereby exploding the data. Koonmen discusses how the new product addresses these challenges.

Brion says it will continue to invest in Tachyon NXE to continuously improve its capabilities, while developing a separate product that will enable customer access to NXE-specific effects within a broad range of simulation tools. This second product will be available soon. — D.V., J.M., M.C.

At, Jim Koonmen, GM of Brion, talks about the industry transition to EUV and the software's role. And Fujimura and SST's Debra Vogler talk about "making the impossible 80hr photomask possible." — J.M

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