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SPIE Microlithography Conference: Lithographers clean up their act |
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Feb 23, 2006 at 12:00 AM |
It was down right dirty last Sunday at Nikon's Litho Visions conference and Monday was a poor attempt to clean up the act. It looked like Nikon had an edge over ASML in the dirty talking stakes. Was this going to tarnish ASML's clean living image?
Let me back track a moment and explain that one of the current marketing or rather positioning attempts of Nikon concerning its immersion tool is that they have no defect problems compared to ASML. The perception Nikon is giving at SPIE is that ASML's shower head design, which uses an air shield to keep the water contained within the bottom lens head area is inferior to Nikon's design.
Last year Nikon spent a lot of effort telling people that ASML had a problem with bubbles in the water that were causing defects on the imaged pattern. Nikon's system didn't have that problem. By the end of the last years conference ASML had demonstrated in several different ways that the new shower head design did not produce bubbles.
This year the fight is over defectivity and this is proving an interesting battle, not least because both suppliers systems are not immune to wafer defects.
IBM and TSMC have come out in support of ASML yesterday, demonstrating that the defect issues on the ASML immersion tool have been brought under control and importantly are in the range that makes it easy to transition immersion into volume production at the 45nm node.
The defect issue is actually not just a shower head design issue as many papers at the conference highlighted how bubbles left on the wafer after the scanning motion were a great breeding ground for the subsequent killer defects. Work carried out by TEL indicates that neither lithography tool supplier has any real advantage over the other in the defect stakes and that the real work to limit defects is really taking place the resist processing track.
The fact that many of the defects can be handled with a new rinse process step highlights that immersion tools will pass the defectivity issue but at a cost of adding steps in the track. The track work will actually be on going due to the variety of resists etc... any one fab will be using. It's a dirty job for TEL but some one has got to do it!
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