Double Patterning Drives Computational Upgrades

Aaron Hand, Executive Editor, Electronic Media -- Semiconductor International, 2/25/2008 5:30:00 AM

Brion Technologies (Santa Clara, Calif.) today introduced both a platform upgrade and a new product that are geared toward enabling double patterning lithography techniques at 32 nm and beyond. Tachyon DPT has been released specifically to help chipmakers with pattern splitting and stitching. Tachyon 2.5, meanwhile, is an upgrade to the company’s flagship Tachyon computational lithography platform, providing the speed-up necessary for the increased computational load that double patterning will bring with it. “We see an explosion coming in the computational needs from the extension of 193 down to 22 nm,” said Neal Callan, vice president of product operations at Brion.

At the SPIE Advanced Lithography conference in 2007, Brion introduced the Tachyon 2.0, which offered improvements in quality and performance over the company’s original platform, Tachyon 1200. This year, the upgrade to the platform, the Tachyon 2.5, is 2.5× faster than the 2.0. It sits on the same infrastructure as the 2.0, however, so is bit-for-bit compatible.

The Tachyon 2.5 takes advantage of an upgrade from dual-core to quad-core processors to significantly enhance speed performance. But the system also has a few other upgrades to boost the speed even further. “Nominally, when you upgrade from a dual core to a quad core, you typically see in the order of 1.5-1.7× improvement in speed,” Callan said. “We are seeing, overall, about a 2.5× speed-up.” This is due to a few other enhancements:

• Significantly faster aerial imaging computations, essentially speeding up the system firmware software.
• More of the simulation capability is moved onto the accelerated hardware platform.
• Enhanced system-level communication.

Tachyon 2.5 upgrades enable additional speed improvements relative to quad-core upgrades only. (Source: Brion Technologies)

“The significant advantage that the 2.5 brings is, for the same IT infrastructure, in terms of power consumption and floor space, you’re realizing the 2.5× improvement,” Callan said. “So from a cost-of-ownership perspective, we’ll be delivering significant advantages in the same form factor.”

The increased computational speed helps to support development and use of double patterning techniques, as well as other low-k1 resolution enhancement techniques (RETs). “At 22 nm, we will see the adoption of much more double patterning, more mask 3-D effects, things of this nature,” Callan said. “We have to deliver the same consistent cycle time to the customer, within the same package, that enables them to see the same basic turnaround time by adding more computational capabilities.”

Tachyon DPT is a production-ready, complete end-to-end solution that supports both litho and spacer double patterning techniques. It offers full-chip conflict-free pattern split, model-based optical proximity correction (OPC), model-based stitching compensation, and automatic density balancing.

The double patterning software takes a mask image provided by a customer and identifies which features go on which mask, Callan explained. The software can do the coloring on a layer-specific basis to make sure, for example, that a line is not split if it goes across an active gate. “It sounds simple conceptually, but from a software implementation, it’s a little more complicated,” he noted.

The software also takes care of the OPC on the two masks. “And we have to stitch them back together in such a way that they take into account the overlay variations you will see from an actual scanner between when you image two masks together, especially when there’s an etch step between them,” Callan said. “So we have overlay-aware model-based stitching, which means that we can take into account during the software optimization that variation in the overlay that’s due to the sequential processing steps of the two masks. And that can be dialed in by the customer to the number they believe they can hold on the scanner.”

Tachyon DPT also factors in automatic density balancing to avoid CD variation caused by loading effects. “So not only do you have to split the mask to take advantage to increase your k1, but you have to do it in such a way that you can maintain the CD control as much as possible — equivalent to a single exposure as you would a double exposure,” Callan said. “CD control is extremely important for double patterning, as also is the overlay of the two masks.”

As noted, in broad terms, Tachyon DPT supports both litho (photo, etch, photo, etch) and spacer double patterning techniques. But the system also provides an open architecture so that customers may develop more proprietary double patterning techniques. “We basically provide a very open API engine to the customers, where they can develop some of their own techniques,” Callan said.

Tachyon DPT is currently available, and Tachyon 2.5 will be available in June.