Majority of Japanese chipmakers choose minienvironments

By Peter Dunn

Earlier this year, eight of the top 10 Japanese integrated circuit (IC) companies indicated that they would break with Japan`s long-standing practice of open cassettes and tight cleanroom protocols in favor of the front-opening unified pods (FOUPs) that are gaining wide acceptance elsewhere in the semiconductor manufacturing world. NEC and Mitsubishi were reported to be the only holdouts.

NEC, Japan`s largest chipmaker, has not yet decided whether it will adopt the use of minienvironments for its 300 mm wafer fabs. The company is leaning toward continued use of open cassettes. If NEC does maintain its traditional use of open wafer cassettes, it would be one of only a handful of chipmakers to follow such a course.

Seiichirou Takabayashi, NEC`s liaison to the J300 standards development group, says the company continues to see the use of open cassettes as more likely than a shift to FOUPs. “We have much more experience with the use of open cassettes, and the system of open cassettes is simpler and has no big problems,” comments Takabayashi. “On the other hand, we will study the merits of FOUPs, and if we find higher merit, we may adopt them.”

For equipment suppliers, a monolithic shift to the use of FOUPs for 300 mm wafers would be helpful, as it would eliminate the need for developing and maintaining two slightly different wafer carrier interfaces. NEC is a large enough operation, however, that it could probably hold out against a contrary tide, at least for a generation or two. And unless equipment companies charge a premium for open-cassette versions of their tools, early cost of ownership results would likely fall in favor of open cassettes, given that most chipmakers maintain tight cleanroom standards even when they adopt minienvironments.

Takabayashi declined to comment on NEC`s time frame for making a final decision on the wafer carrier issue.

Jiro Yamamoto, NEC`s general manager for process technology, said in a Japanese magazine, the November 1997 issue of Electronic Journal, that NEC will not employ the FOUP system or any other minienvironments for near-future 300 mm manufacturing. Instead, they will use the open cassette system. According to Yamamoto, the FOUP has two problems: cleanliness and cost. He believes it is doubtful if cleanroom cleanliness can be reduced by the employment of the FOUP.

Kunio Morioka, NEC`s general manager-manufacturing engineering, said at the SEMI Technology symposium held during SEMICON Japan, December 3-5, 1997, that using open cassettes could reduce the size of stockers and keep cleanroom costs at a minimum.

Peter Dunn is the Editor of WaferNews, a sister publication to CleanRooms.