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  • SEMICON West - Leti FDSOI and IOT, status and roadmap

    Article: A Brief History of Cadence Design Systems-leti-cea-intitute-min-jpgOn Tuesday, July 12th at SEMICON West I had an opportunity to sit down with Marie Semeria, the CEO of Leti and discuss the status and future of FDSOI. Leti pioneered FDSOI 15 years ago and has been the leading FDSOI research ever since.

    Two years ago Leti and ST Micro demonstrated products on 28nm that are cost competitive with bulk technology. For the first time the industry could consider two approaches to leading edge requirements, FinFET for high-end and FDSOI for low-cost and flexible IOT designs. Both technologies can cover multiple technology nodes. Since then ST has licensed 28nm to Samsung and Global Foundries and 14nm developed with Leti to Global Foundries. Global Foundries is now preparing to introduce a 22nm technology, 22FDX based on the Leti-ST 14nm front end with a relaxed back end for cost. FDSOI is out of research into foundries and an IDM and products are coming out.

    In terms of scalability:
    • 14nm - demonstrated the technology is scalable to 14nm with ST Micro.
    • 10nm - they have completed modeling and some test devices. They have a full integration scheme and they have shown the modeling matches the actual results allowing them to have confidence when they use modeling to extrapolate to the next node. Strained SOI and silicon germanium are 10nm performance boosters but even with the current substrate they can meet 10nm requirements.
    • 7nm - modeling done.
    • 5nm - beyond 7nm Leti believes that at 5nm horizontal nanowires will be the next technology.


    Authors note - the following table was added to the article on 8/10/2016

    Leti defines the nodes mentioned above as follows where CPP = contacted poly pitch.

    Node (nm)1410753
    CPP (pitch)8060504030
    M1 (pitch)6448403224




    Commercially 28nm is running at ST and Samsung and 22nm is coming up at Global Foundries. Global Foundries plans a follow-on to 22nm and Leti has assignees in Dresden working with Global Foundries and discussions are ongoing. The exact node for the follow-on technology hasn't been announced yet (authors note - in a recent interview with Samsung they also discussed a follow-on technology to the 28nm process they are running; they want to avoid multi-patterning for cost reasons so it sounds like a relaxed 22nm technology at Samsung, at Global Foundries my guess is something in the 12nm to 16nm range will be next).

    The ecosystem for FDSOI is completely established with fabless, foundries, IP companies and IDMs all supporting it. Leti has established the silicon impulse initiative as a gateway for designers to get trained and use multi-project wafers to evaluate FDSOI. In one year more than 20 companies have joined the initiative to assess the technology. There are over 60 tape-outs running at ST, Global Foundries and Samsung.

    Marie expects to see many more FDSOI products in IOT due to low energy consumption and the ability to support RF and embedded memory. They have demonstrated RF to over 300Ghz! Leti is working with ST to develop back-end memory for 28nm or 20nm for a microcontroller. The memory may be PCM or OxRAM. Leti is also working with Spin Tech on magnetic memory, they have a European research grant and are focused on embedded memory and low voltage operation.

    IOT is a very fragmented market today and requires a lot of different types of IP, FDSOI could be the IOT platform. In automotive IOT it is at the connected device level, plus processing of data and security. More and more big companies are developing their own structures and clouds to manage data. SOI has good radiation hardness and that is an advantage for automotive. At DAC Leti demonstrated a new driver assistance system using an ST microcontroller. Automotive needs low cost and global environment coverage, Leti has a probabilistic approach that avoids floating point operations and lowers computing requirements by 100x and power by 200-400x. In IOT you have to think about specific requirements of the application and then you can have tremendous impact on power and cost. You don't need a lot of capacity in computing if you look at the whole system. They are working with companies in automotive to optimize the system to keep relevant information close to the sensors and optimize it for the type of operation.

    In the late nineties IBM introduced partially depleted SOI (PDSOI) in their internal processor line. I suggested to Marie that because PDSOI required an expensive SOI substrate and yet didn't reduce process costs it was an expensive solution and created an image of SOI an unaffordable whereas FDSOI greatly reduces the process complexity making FDSOI far more affordable (authors note - IBM's processor needs were for high performance and cost wasn't really an issue). My belief is this created a perception of SOI as high cost that FDSOI is still working to overcome and Marie agreed with me on this.

    Today with Global Foundries poised to ramp 22FD and Samsung and ST running 28nm FDSOI is finally poised to take off. Global Foundries and Samsung are also both planning follow on nodes and FDSOI has a path to continue to scale for many years.