FD-SOI: The Right Choice
Posted date : May 14, 2011

Although Intel will do FinFETs at 22nm, FD-SOI remains the better alternative for most all the industry for low power and mobile apps. In the weeks and months to come, we’ll continue hearing  the SOI camp addressing key points.

1. FD-SOI technology is the most cost-effective solution. The wafers are available from multiple sources. With volume purchasing, multiple mask layer savings and evolutionary design transition, FD-SOI comes in cheaper.

2. Ultra-thin SOI wafers are ramping in volume this year. Although for years, it was thought SOI wafers with super thin top silicon and BOX were beyond the purview of suppliers, Soitec has done it using their standard Smart Cut wafer manufacturing technology. These wafers are available now (see the ASN16 article where Soitec gives the details). Manufacturing lines are set to roll with industry ramp.

3. The ultra-thin SOI can include ultra-thin BOX. Much of FD-SOI will use ultra-thin BOX as well as ultra-thin top Si. ST is an example of a company doing great things here.  As they pointed out in a recent ASN article, “Designing a good SOC involves using the right blend of low, standard and high-Vt devices according to the target application and how it’s being used at any given time.” The ultra-thin BOX and ground plane with or without bias enables this option with a simple process flow. Their hybrid co-integration approach on ultra-thin Si/BOX SOI lets them reuse bulk ESD and I/O IP.

4. FD-SOI does very well  for both performance and power savings – at high and at low voltages. The supply voltage (Vdd, which  essentially determines power consumption) is different depending on the app and the state of the device. Intel says its TriGate gets a 37% propagation time improvement (therefore enabling improvement of operating frequency by 58%) over the previous generation at 0.7V; but FD-SOI is getting a +125% operating frequency improvement. The SOI Consortium recently published data about FD-SOI on an ARM chip.  Now they’re working on further data, and on lining up the ecosystem.

For the real world of high-performance, low-power mobile apps, planar FD-SOI really looks like the way forward.  For those in the fabless world, it gives game-changing results without changing existing design flows or manufacturing processes. The SOI Consortium has a terrific Q&A if you need more about planar-FD-SOI in general.

Intel does amazing things on the fab floor, to be sure. But the FD-SOI camp has done the math, too – and they’ve got a very different story to tell. Watch this space!

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