Major progress reported in 157nm lithography

All major obstacles to manufacturing 157nm optical lithography have been overcome, according to industry experts attending the Third International Symposium on 157nm Lithography.

All major obstacles to manufacturing 157nm optical lithography have been overcome, and the industry is planning for insertion of 157nm lithography at the 65nm node, according to industry experts attending the Third International Symposium on 157nm Lithography, held in Antwerp, Belgium.

"Although very significant engineering challenges remain, it is believed that the developments are on track targeting insertion in manufacturing", said Luc Van den hove, general Chair of the 2002 157nm symposium, and vice president of Silicon Process and Device Technology at IMEC.

"All major bottlenecks have been removed".

Moreover, said Tony Yen, Symposium Co-chair and a Director of Lithography at International Sematech (ISMT), "All lens designs for the first-generation 157nm exposure tools have now been fixed, and suppliers' commitment to deliver the first 157nm scanners in 2004 is highly encouraging".

These machines will accommodate the use of hard as well as soft pellicles.

The meeting, held 3rd-6th September, was organised by IMEC and International Sematech in co-operation with Selete, the Japanese chip consortium.

Nearly 240 representatives from worldwide chipmakers, tool and materials suppliers, consortia, universities, laboratories, and research groups attended the symposium.

Other results of the conference include the following breakthroughs.

Over the last year, major progress has been achieved in resist technology.

Resists with increased transparency and improved imaging characteristics have been reported.

Further work remains on the integration of these new chemistries to provide resists with resolution and thickness needed for 65nm manufacturing.

Leading exposure toolmakers continue to plan for the shipment of first 157nm scanners before the end of 2004.

The problem of intrinsic birefringence of CaF2, as reported by NIST in May 2001 (study sponsored by International Sematech), has been solved by using a combination of lens elements made from <111> and <100> crystals, resulting in negligible net birefringence effects.

<111> and champion <100> lens blanks have met required specifications.

The viability of fused silica hard pellicles has been demonstrated.

While hard pellicles can be the solution for high-volume manufacturing of DRAM or logic devices where increased pellicle cost is averaged over many wafers, soft pellicles are still preferred for low-volume devices such as ASICs.

ISMT has launched a project involving several universities to study the mechanism of photochemical darkening that will lead to polymer materials capable of withstanding 157nm radiation.

The next worldwide 157nm forum - the 4th International Symposium on 157nm Lithography - will be held in Yokohama, Japan in August 2003 and will be organised by Selete and International Sematech in co-operation with IMEC.

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