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Easier OPC is tools' promise

Posted: 03 Apr 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Halo-iOPC? Tachyon OPC+? optical proximity correction? OPC? Aprio Technologies?

The semiconductor industry's battle with design-for-manufacturing (DFM) challenges is mainly focused on the resolution enhancement technology (RET) front, with EDA executives saying that as much as 80 percent of DFM revenue is lithography-related. As recent product introductions by Cadence Design Systems Inc. and startup Invarium Inc. attest, companies big and small see a big market opportunity in providing technology that can improve yields by giving customers more control over the implementation of RET features to compensate for the fact that they are printing lines smaller than the wavelength of light used to image them.

Adding to the momentum, two privately held companies, Aprio Technologies Inc. and Brion Technologies Inc., introduced products that apply their established technologies to the most common RET, optical proximity correction (OPC). Aprio's Halo-iOPC and Brion's Tachyon OPC+ were launched at the recent SPIE Microlithography Conference in California.

Pre-OPC cells
Halo-iOPC extends Aprio's Halo hierarchical OPC implementation technology to "pre-OPC" cells. It conducts lithography simulation prior to tape-out, giving designers more accurate data derived from simulated silicon results, the company said. For its part, Tachyon OPC+ applies technology used by Brion's Tachyon hardware-accelerated lithography-simulation engine to OPC implementation.

According to Aprio, the advent of distributed processing is not enough to alleviate problems of exorbitant runtimes and inaccuracy at 65nm and 45nm nodes. Halo-iOPC (or "incremental OPC") includes all the features of Aprio's original OPC implementation product, but also enables manufacturing-side users to optimize the lithographic performance of cells. At design tape-out, Halo technology integrates pre-optical-proximity-corrected cells, non-corrected cells, layout and routing to achieve substantial runtime improvements over conventional OPC tools, the company said.

Halo-iOPC, according to Aprio, also enables designers to take advantage of "DFM views," generated from simulated printed images for more accurate characterization of cell performance.

A large percentage of SoC designs today are essentially done before they are started, thanks to the use of third-party processor cores, compiled memories and other elements, said Mike Gianfagna, Aprio's president and CEO. Aprio, he said, discovered that a lot of customers perform pre-OPC work up front on these elements for characterization purposes, but discard that data for want of a method of saving it, and essentially "OPC from scratch" during tape-out. Aprio decided that this was inefficient.

"If you can access the data early on, why not pre-OPC the libraries and save the information?" Gianfagna asked. The top-tier EDA vendors, he said, have not had the luxury of concentrating on this problem. "That's where startups come in."

Brion, meanwhile, touts Tachyon OPC+ for its ability to deliver high-quality, accurate OPC features using the company's focus-exposure-modeling, through-process-window, full-chip technology. Unlike conventional OPC tools, Tachyon OPC+'s processing speed scales linearly with die size, enabling large, complex devices to be processed at the same speed per square millimeter as smaller designs. This, the company said, enables computational lithography departments to know beforehand how long an OPC run will take, easing scheduling and removing an aspect of uncertainty from the DFM flow.

The tool is built on Brion's Tachyon platform, a hardware-accelerated, image-based data and simulation engine that has been shipping since 2003. Brion describes Tachyon as a hybrid architecture that combines the strengths of image-based simulation with polygon- and contour-based geometry processing used by conventional physical-design EDA tools. The result, according to the company, is accuracy, comprehensive coverage, predictable runtimes and flexible user-controllability. Brion says it has built 30 Tachyon systems and that thousands of production circuit layers have been processed by Tachyons worldwide.

Brion has been working on Tachyon OPC+ closely with select customers for about two years, said Jim Wiley, Brion's senior technical director. He said that two companies, the names of which Wiley declined to divulge, are already using a prototype of the product.

One of the major differences between Tachyon OPC+ and conventional OPC implementation tools is that it uses an image-based hybrid approach that is more effective for implementing model-based OPC. According to Wiley, users of traditional OPC implementation tools face a trade-off between speed and accuracy. Tachyon OPC+ provides both, allowing users to perform traditionally time-prohibitive operations like dense dissection and modeling of field-dependent effects without compromising throughput or quality.

Tougher sell
Brion has applied to the product a great deal of knowledge gained through its experience in lithography simulation. Wiley said Brion's production experience gives it a leg up on startup rivals that haven't earned customers' trust with their technologies. Even so, he acknowledged that the success of Tachyon OPC+ would require the company to overcome new hurdles. It's one thing, he said, for a chipmaker to trust a company providing verification technology. But an OPC implementation tool is a tougher sell because OPC affects every facet of a design and could have very significant negative impact if not done correctly.

Aprio and Brion each tout both the speed and accuracy of their tools. But Gianfagna and Wiley acknowledged that accuracy is the more important attribute here.

While speed may be the customer's more immediate short-term need, accuracy is what will ultimately make the difference, Gianfagna said. Speeding up OPC implementation is a valuable thing, he argued, but a lack of accuracy could result in respins that would wipe out an advantage in turnaround time.

"The tactical problem is runtime," Gianfagna said. "It's a mess. If you can walk through the door and say you can cut that problem down to size, that gets people's attention. But the ability to predict accuracy before tape-out is actually a bigger and more strategic long-term benefit."

According to Wiley, OPC implementation tools "have to have accuracy to get through the gate." Customers may buy implementation tools for speed, but if they can't prove that they are accurate, they will not even be considered.

Both confident that they have speed and accuracy to offer, Aprio and Brion are likely to encounter mutual competitive challenges in the suddenly crowded market for OPC implementation tools.

- Dylan McGrath
EE Times

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