Maskless tools to boost ASIC throughputs

In 2006, e-Shuttle was established by Japan's Fujitsu Microelectronics Ltd and Advantest Corp. to provide IC prototyping services and low-volume chip manufacturing for customers. The venture uses Advantest's direct-write electron-beam tool, dubbed as F3000.

"Today, e-Shuttle focuses on the production of ASICs and high-speed SRAMs for customers," said Shinji Sugatani, general manager, e-Shuttle. "The company's customers are mostly in Japan and we want to tap that," he added.

One of the company's customers is U.S.-based eASIC Corp., a provider of structured ASICs. With the help of e-Shuttle, the ASIC provider said it has surpassed 100 design wins in only 18 months for 90nm family devices.

Previously, eASIC claimed that there are little or no NRE and mask costs associated with its Nextreme family of ASICs. ''The cost of traditional ASIC customization became prohibitive for the majority of applications and designers. The eASIC's zero mask-charge Nextreme devices have changed the landscape,'' said Ronnie Vasishta, president and CEO, eASIC.

Direct-write e-beam services offered by e-Shuttle, Taiwan Semiconductor Manufacturing Co. Ltd (TSMC) and others could indeed change the landscape for ASICs and related devices. Traditional e-beam tools write transfer design data directly onto the wafer and exposes it, eliminating the photomask.

''The rapidly rising costs and increasingly complex design cycle for advanced standard cell and SoC products have forced many potential customers into postponing or canceling projects, or seeking alternatives such as FPGA prototyping to initiate their designs,'' according to a e-Shuttle report.

''Higher reticle prices and other factors have had quantifiable impact,'' the paper said. It added that, ''The benefits of e-beam lithography are illustrated by reviewing reticle costs, which are six times higher for designs built using 65nm processes technology compared when they were at 130nm. At 45nm process technology, reticle costs will escalate to 10 times the cost at 130nm. For the 65nm process generation, a mask set is priced at $2 million, too high for prototyping.''

Future direction of e-Shuttle
After moving into 90nm production, e-Shuttle is now processing 65nm devices. E-Shuttle is also working on a 40nm technology with plans to offer this capability by the end of fiscal 2008.

The devices are processed via the F3000 e-beam tool from Advantest. In addition, e-Shuttle will expand its capacity by installing a second F3000 e-beam tool next month. Supporting 300mm wafers, Advantest's F3000 is said to pattern designs to the 40nm node. It has a dimensional accuracy of ± 7nm and an overlay accuracy of ± 20nm.

The F3000 makes use of a block exposure system. ''Block mask is an important technology used to reduce the volume of drawing data. E-Shuttle prepares basic master patterns at the same time the technology is developed, and sets the patterns in e-beam direct-write equipment,'' said e-Shuttle. ''Standard cell or SRAM ICs can be drawn by using block mask. This method also increases the precision of the pattern as the measurement of the mask is predetermined."

Advantest and e-Shuttle are making some enhancements to the F3000, including a more stable mechanism and a lower aberration lens. However, despite the improvements, the tool will still have an overall throughput of only about 0.5 wafers per hour. With its new shuttle service, overall throughputs can be increased to about 1 wafer an hour.

This makes e-beam tools a probative technology in mainstream production fabs. Direct-write is, however, being used in the development of compound semiconductor devices.

In fact, the problem with e-beam tools is that they are costly and slow in terms of throughput. This has prompted interest in a new class of maskless lithography tools from a number of startups. The technology, sometimes called ML2, makes use of multiple beams in a system to boost throughputs.

E-Shuttle is keeping a close eye on the ML2 landscape, especially the developments at Mapper Lithography BV. The Dutch-based company is developing a multibeam e-beam tool and has received funding from TSMC. The silicon foundry giant has expressed interested in using Mapper's tools for ASIC production in the future.

"We are very interested in Mapper," Sugatani said. E-Shuttle may use ML2 tools from Mapper or others in the future, but the IC prototyping service company has not made any formal announcements. The company insists that Advantest is its chosen e-beam vendor.

- Mark LaPedus
EE Times