Semiconductor300 attacks 300-mm challenges
07/01/1998
Semiconductor300 attacks 300-mm challenges
The Semiconductor300 joint venture between Motorola and Siemens is reportedly the world`s first 300-mm wafer fabrication facility, and as such will have to try many experiments and grapple with a number of immature product sets when wafers begin to run by the end of this year. The type of problems faced by the Dresden, Germany, fab`s managers gives a sense of just how challenging it is to be the icebreaker at the 300-mm party.
For example, Semiconductor300 executives say the first wafers will be run in lots of 25, using front-opening unified pods (FOUPs), because the initial tools are set up for that size pod. But there are no mature 25-wafer FOUPs on the market, so at some point, the operation will switch to 13-wafer FOUPs, which have been on the market for a year or two and gone through several design revisions. For pilot production, the facility will probably convert back to 25-wafer lots so that statistical comparisons of the two lot sizes can be made. "It`s part of our mandate," said general manager Peter Kucher, a Siemens veteran.
The 300-mm wafers themselves also pose a number of questions. "Epi is certainly the target substrate," noted Karl Mautz, a Motorola assignee who is serving as lithography and etch manager. "But we need testing of the wafers to ensure the proper electrical parameters, flatness, and cleanliness. It`s a challenge. There will be comparisons, to prove whether epi is necessary."
Edge exclusion is another area of research. Semiconductor300 had originally hoped for a 3-mm exclusion zone, but it now appears that the deep trench etching and CMP processes will force a 5-10-mm exclusion, said Mautz. "That increases the difficulty of the layout." No specifications on the kerf between chips has been published, he added.
Another logistical issue is how best to locate and operate wafer stockers. Mautz said modeling of the fab suggests that a central stocker design would require wafer lots to travel 24 miles during their processing. Placing stockers on each aisle would reduce this to 17 miles, while having a stocker on each tool would cut the distance to 11 miles. Moreover, said Kucher, some stockers, like those in the implant area will have to be very large. As a result, he noted, "the operation of stockers is starting to approach the complexity of operating cluster tool robots."
Kucher noted that his experience as a project manager at the IBM-Siemens-Toshiba memory joint venture in East Fishkill, NY, would be helpful in his new role. "It`s important to define the same goal for all the partners, and make sure you have the same path to the goal," said Kucher. And while he accepts the challenges of his position as the head of the world`s first 300-mm line, he states, "I would appreciate having other fabs, so that we could get broader input. We want to use the International 300-mm Initiative, and not create something specific - that would be very costly." He added that Siemens hopes I300I will continue to exist through 1999 to cover the period when fabs are beginning to start up.
Tools began arriving last November at the facility, which is a 2400 m2 area (1800 m2 of cleanroom space) within Module 2 of the Siemens Dresden fab. Most process equipment is expected in the 3Q, although Mautz cautioned, "it`s a one-of-a-kind set, and schedules change." A 0.25-?m DRAM process will be used for equipment and process development; Kucher commented, "to bring up a manufacturing technology, you start with an established technology. Both companies have their own programs in process development."
A decision on where the companies will build subsequent 300-mm facilities will likely come in 1999, said Kucher; the West Creek facility in Virginia and the Dresden facility are contenders. Meanwhile, 0.25-?m processes will be brought up in four Siemens 200-mm fabs. - P.N.D.