News Article
The road to EUV is paved with water
In 2005, immersion lithography cemented its position as the next viable production patterning process, with a range of new tools arriving and chipmakers announcing firm plans for moving the technology into production in the next few years. As 2006 begins, immersion is expected to achieve even finer resolution, with shipments of 45nm-capable tools (and the necessary materials and ancillary equipment), and research institutions continuing their important development work. Ron Kool, Director of Product Marketing at ASML looks beyond immersion and discusses the future of ASML's lithography programme including next year's delivery of ASML's EUV Alpha tools to research organisations in Europe and North America.
One important milestone of 2005 was the success of immersion pre-production projects at several manufacturing sites around the world using new generation immersion systems. Results showed the system's imaging capability adhered well to dry system specifications. Other equipment makers announced their own pre-production immersion tools this year, while several of ASML's customers shared encouraging results of their immersion development research.
The success of ASML's first generation immersion tools laid the groundwork for shipment of ASML's XT:1400i, with 0.93 NA ArF lenses. The XT:1400i, announced in 2004, was shipped in the middle of 2005. In that same timeframe, ASML announced its fourth-generation immersion system, the TWINSCAN XT:1700i for delivery in 2006. The XT:1700i features a Starlith catadioptric lens from Carl Zeiss SMT AG, with a 1.2 NA, and an expected throughput of 122 wafers per hour, the fastest immersion tool in the industry.
This next-generation tool also includes an advanced polarised illumination system for improved contrast and exposure latitude at full throughput. With a 1.2 NA, polarisation enhances resolution down to 45nm. Overlay accuracy in the XT:1700i is approaching the high levels previously achieved with 193nm dry lithography.
A key differentiator of the XT:1700i from ASML's earlier immersion tools is the 1.2 NA catadioptric lens, which contains mirrors. Its uni-axial lens design, made specifically for the TWINSCAN platform, has low aberration levels and excellent lens heating performance. The design concept can be extended beyond an NA of 1.3. These advances relax many lithography process parameters, which helps customers improve yields.
Where do we go from here?
Beyond the achievements of 2005, much work remains. In immersion, the higher refractive quality of water boosts the depth of focus and enables higher resolution. However, defectivity becomes a challenge with the introduction of water into the process, and this has been a primary focus of more than two dozen equipment and materials suppliers in the Industrial Affiliation program set up by the IMEC research institution in Belgium.
Several options exist for supporting customers' roadmaps by extending the water based immersion concept, such as immersion with higher index fluids and double patterning. The high resolution enabled by powerful new-generation lenses, coupled with development of new fluids or fluid-doping techniques, suggest it is possible to achieve a 1.5 NA. That would enable 36nm half-pitch resolution printing and extend immersion's capability to close to EUV's capability of 32nm half-pitch dimensions. In anticipation of customer needs at that juncture, ASML has developed pre-production, full-field EUV scanners capable of printing test patterns for research and development.
This EUV Alpha tool, the semiconductor industry's first-ever full-field EUV scanner, is scheduled to be shipped to IMEC and Albany Nanotech in 2006. EUV may be the only technology that can deliver the production volumes required by leading-edge chip companies, whose devices will require design shrinks below 25nm half-pitch. Collaboration has played a vital role in bringing immersion this far and a broad partnership effort is committed to continuing and, indeed, intensifying, the collaboration required to extend the bridge from immersion to EUV.
Traditionally, lithographers have not been able to see clear solutions more than two generations ahead. While this is still generally true today, the basic course of development seems clearer now than it has in several years, and 2006 is shaping up to be another very progressive year for the lithography sector.
The success of ASML's first generation immersion tools laid the groundwork for shipment of ASML's XT:1400i, with 0.93 NA ArF lenses. The XT:1400i, announced in 2004, was shipped in the middle of 2005. In that same timeframe, ASML announced its fourth-generation immersion system, the TWINSCAN XT:1700i for delivery in 2006. The XT:1700i features a Starlith catadioptric lens from Carl Zeiss SMT AG, with a 1.2 NA, and an expected throughput of 122 wafers per hour, the fastest immersion tool in the industry.
This next-generation tool also includes an advanced polarised illumination system for improved contrast and exposure latitude at full throughput. With a 1.2 NA, polarisation enhances resolution down to 45nm. Overlay accuracy in the XT:1700i is approaching the high levels previously achieved with 193nm dry lithography.
A key differentiator of the XT:1700i from ASML's earlier immersion tools is the 1.2 NA catadioptric lens, which contains mirrors. Its uni-axial lens design, made specifically for the TWINSCAN platform, has low aberration levels and excellent lens heating performance. The design concept can be extended beyond an NA of 1.3. These advances relax many lithography process parameters, which helps customers improve yields.
Where do we go from here?
Beyond the achievements of 2005, much work remains. In immersion, the higher refractive quality of water boosts the depth of focus and enables higher resolution. However, defectivity becomes a challenge with the introduction of water into the process, and this has been a primary focus of more than two dozen equipment and materials suppliers in the Industrial Affiliation program set up by the IMEC research institution in Belgium.
Several options exist for supporting customers' roadmaps by extending the water based immersion concept, such as immersion with higher index fluids and double patterning. The high resolution enabled by powerful new-generation lenses, coupled with development of new fluids or fluid-doping techniques, suggest it is possible to achieve a 1.5 NA. That would enable 36nm half-pitch resolution printing and extend immersion's capability to close to EUV's capability of 32nm half-pitch dimensions. In anticipation of customer needs at that juncture, ASML has developed pre-production, full-field EUV scanners capable of printing test patterns for research and development.
This EUV Alpha tool, the semiconductor industry's first-ever full-field EUV scanner, is scheduled to be shipped to IMEC and Albany Nanotech in 2006. EUV may be the only technology that can deliver the production volumes required by leading-edge chip companies, whose devices will require design shrinks below 25nm half-pitch. Collaboration has played a vital role in bringing immersion this far and a broad partnership effort is committed to continuing and, indeed, intensifying, the collaboration required to extend the bridge from immersion to EUV.
Traditionally, lithographers have not been able to see clear solutions more than two generations ahead. While this is still generally true today, the basic course of development seems clearer now than it has in several years, and 2006 is shaping up to be another very progressive year for the lithography sector.
