Litho meeting: 4x reduction ratio to stay, for now

08/01/1999

Don't look for a change in the standard lithographic reduction ratio or reticle size - not yet, at least. A recent international meeting of lithography experts in Chicago discussed the question prior to its review of next-generation lithography progress, with most attendees coming down in favor of no change from today's 4x reduction factor on 6-in. reticles.

"The breakout groups said staying with six-inch and 4x is the preferred way to go," said Sematech's Gil Shelden, who is leading the consortium's optical extension efforts. "Those who preferred to make a move, which was a much smaller number, wanted to go to 5x on six-inch reticles. Another group, that was smaller still, said 6x on seven-inch reticles; very few wanted nine-inch." To a large degree, positions were determined by product type - makers of DRAMs and high-volume logic run thousands of wafers/mask and seek high throughput, while ASIC producers are more concerned about mask costs, which must be amortized over far fewer wafers.

Earlier this year, some in the industry had suggested that a change in the standard reduction ratio could simplify the problems facing development of masks for advanced litho technology, particularly the 157nm wavelength.

Shelden noted, however, that "right after the group got done saying that the preferred solution is 4x, they proceeded to list the problems with maskmaking and why it could be a showstopper for the industry." The reduction ratio question could be raised again down the road, he said, "if there is enough pain."