Sematech Warns of EUV Mask Blank Shortfall
By David Lammers
For much of the past year, many in the chip industry have viewed with alarm the slow progress in EUV source power. But GlobalFoundries’ Stefan Wurm, the director of Sematech’s lithography program, said the bigger challenge lies in the mask area, including getting the two major EUV mask blank vendors to boost their investments.
Stefan Wurm
At the recent Advanced Semiconductor Manufacturing Conference in Saratoga Springs, N.Y., Wurm said while boosting the source power has been a bigger challenge than expected, the investments of time and engineering resources have been large enough to solve the problem. “I have a lot more confidence today” that source power will increase sufficiently by the end of the year to support a 30 wafers-per-hour throughput level on the ASML NXE:3100 scanners now in the field.
“I am much more worried about the mask issue,” Wurm said, particularly the EUV mask blanks. The blanks have MoSi multilayers, and must be free of defects and particles to a much higher degree than today’s mask substrates. EUV blanks used by logic companies must have three or fewer total defects, and none larger than 100nm, he said. As design rules shrink, the size of critical defects also gets smaller.
“The real challenge is not the (MoSi) deposition process. The real problem is defects on the substrate. The number of (meaningful) substrate defects really increases as the defects get smaller,” Wurm said. (See a contributed article from Sematech on the mask defect issue.)
There are only two mask blank suppliers, Asahi Glass and Hoya, both Japan-based, mid-sized companies which Wurm said are now cautious about making relatively large investments – on the order of $100 million – to add significant mask blank capacity. “They see that the source power is taking a longer time than expected, and so they may be thinking they don’t have to make investments now. And they both have other businesses.”
Without being specific, Wurm said meetings have been held with the two mask blank suppliers to discuss ways to boost their investments. Time is growing short. Some memory suppliers want to start using EUV lithography as soon as next year, and logic vendors want to begin commercial use of EUV scanners in 2015, Wurm said. By that time, the industry will need a mask blank capacity of about 6,000 units, he estimated. Defect levels will need to be improved by 100-500 times compared with today’s levels in order to support high-volume manufacturing.
Tags: Asahi Glass, EUV lithography, GlobalFoundries, Hoya, Sematech