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One of the major users of SOI wafers has been Sony, who uses them for the Cell microprocessor. However, a story over at Semiconductor International highlights that Toshiba’s taking over production of the chip has led the company to consider moving the design to its bulk CMOS process instead. 

SI quotes Atsutoshi Nishida, Toshiba President and CEO, so there is no rumor mill stuff here. Interestingly, the story paints the picture that the reason for dumping SOI wafers is because Toshiba has no experience with SOI and that to gain the necessary experince would require extra resources and time that it obviously doesn’t think it can afford.

Following on from this, it is strange that the Sony engineers currently working and expected to be retained at the soon-to-be-acquired fab in Nagasaki have plenty of experience with SOI!

It would seem, however, that it is in reality a simple manufacturing cost issue as the story rightly points out that Toshiba is planning to fabricate a range of bulk CMOS chips based on the Cell design for graphics apps and the like.

Having a mix of wafer types as well as different designs and processes is a headache only a few foundries could handle - and at a premium. Toshiba is therefore attempting to keep wafer lots as simple as possible.

The losers in this shift are obviously the SOI wafer growers. Though Soitec springs to mind, Sony has also used Japanese wafer suppliers, so the impact is rather spread out. But the one that actually concerns me is SIMOX-SOI implantation equipment company Ibis Technology, which has supplied Japanese wafer grower SUMCO with a couple of its SOI implanters.

Ibis has been hanging on by its fingertips for longer than I can remember and any loss of SOI orders in Japan from Toshiba’s shift back to bulk would limit the near-term need for SUMCO to order an additional tool. Ibis would find it almost impossible to remain a player in the industry if no new order is received in 2008, and that looks highly likely at the moment!

However, the bigger picture hasn’t really changed. SOI may lose a long-standing partner but only last year we saw UMC and ARM get serious about the future use of SOI for a whole range of IC devices. Though Intel knocks SOI, it is still dabbling with the technology and its announcement that it is moving back into the mobile market in the future could mean it adopts SOI for those applications.

Yes, the Toshiba news could be a knock for the SOI camp, but it’s no knock-out.