European chip company STMicroelectronics NV is gaining design wins for its 28nm fully depleted silicon-on-insulator (FDSOI) manufacturing process but is being coy about who will be its initial partner for high volume manufacturing. The date for the start of second-source volume manufacturing of FDSOI chips also appears to have slipped.
Jean-Marc Chery, executive vice president and general manager of embedded processing solutions at ST, told Electronics 360 that the number of FDSOI IC designs in development has risen to 15. That number stood at three about eight months ago. But he also declined to discuss progress at Globalfoundries in bringing up high volume manufacturing capacity of FDSOI chips.
Chery said: "By Q4 we will be ready for mass production in Q1. We will have an open, dual-foundry source for FDSOI." When asked if that second source would be Globalfoundries, Chery added: "We have an agreement with Globalfoundries that is not exclusive."
ST (Geneva, Switzerland) can run prototype-to-medium volumes of FDSOI at its own pilot wafer fab anf R&D center in Crolles, France. In February 2013 a Globalfoundries executive told a conference that the first "risk production" of FDSOI chips under license agreement with ST would come out of Globalfoundries wafer fab in 4Q13 and that volume production would ramp during the first half of 2014. That appears to be at odds with Chery's latest statement.
In May 2013 Chery disclosed that ST was considering the transfer of the 28nm FDSOI process to a couple of other foundries; Semiconductor Manufacturing International Corp. (Shanghai, China) and United Microelectronics Corp. (Hsinchu, Taiwan). It could be that a south-east Asian foundry will be the first to offer ST's FDSOI process.
The FDSOI process, originally developed within IBM, has been pioneered as commercial offering by ST but it remains outside the mainstream. The conventional wisdom is that bulk planar CMOS at 28nm and 20nm will migrate to FinFET manufacturing at a 16/14nm node. Intel has pioneered FinFET manufacturing transition at 22nm and now the leading pure-play foundries, including TSMC and Globalfoundries, are preparing to make the same transition.
Chery insists that FDSOI has clear benefits for applications in SoC chips addressing set-top-box, client-server, and home gateway applications. ST is itself designing a family of 64-bit chips for such applications under the STi8K name that will be implemented in 28nm FDSOI. These will follow on from a current generation of 32bit chips being made for ST by Samsung in 28nm bulk CMOS, Chery said.
"The performance improvement from a move to 20nm bulk CMOS is not so great. A move to 28nm FDSOI provides 30 to 40 percent performance improvement, lower power and much greater flexibility on the operating voltage," Chery said. "Another factor is that access to FinFET processes from foundries is limited to a short list of companies that does not include vendors of STB ICs," he added indicating that for initial FinFET sales foundries are primarily interested in mobile application processor vendors with extremely high volume requirements.
Other reasons to turn to FDSOI include the simplicity of design and support for analog circuits. "Communications ICs also need analog capability in the form of high-speed SERDES [serializer-deserializer I/O]. Analog is easier in FDSOI," Chery said.
Chery also added that for STB and some other applications – such as ASICs for communications infrastructure, networking and routers – the volumes required can be supported out of Crolles. "Crolles can support a selective list of customers that need high complexity and low volume. ST will be the preferred manufacturer for those customers."
Of the 15 design wins six are in the communications infrastructure category and 9 are for consumer applications and ST's STB design is only counted as one of these. "There is one application that makes use of very low voltage, 0.6V operation," Chery said, indicating that designers of power-constrained chips for Internet of Things (IoT) applications are also looking at FDSOI.
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