Intel 22nm finFETs debut
By now, you’ve probably heard that Intel has uncloaked “tri-gate” finFET (a.k.a. Multi-Gate FET or MuGFET) architectures as the company’s 22nm transistor technology for high-volume manufacturing (HVM) of digital ICs. This confirms the rumors that have spread for the last half-year, and proves that this pseudo-3D approach will finally live outside of R&D labs. With much of the IC fab world focusing on low-power chips for mobile applications, the fully-depleted channels of finFETs provide reduced power consumption.
To be sure finFETs are a very attractive way to get to fully-depleted channels and so achieve the lowest possible off-current in transistors. At last year’s IEDM, with rumors of this move by Intel rampant, there was much hallway conversation about the relative merits and demerits of wrapping gates around a fin. In general, there are 2nd-order electrostatic issues associated with the 3D structures so that new possible leakage paths must be controlled. An IEDM evening panel discussion sponsored by Applied Materials featured a discussion on finFETs vs. FD-SOI vs. alternate-channel materials for 22nm node processing. Witek Maszara of GlobalFoundries explained that, “Better electrostatics could come from FD or MuGFET devices, while better transport could come from high-mobility channels.”
Intel first showed tri-gate finFETs for SRAMs in 2006, and claims that only 2-3% additional processing costs are needed to go from planar FETs in high-volume. Consequently, the major advantage of finFETs at 22nm is that no new channel materials will have to be integrated, and the extra cost of silicon-on-insulator wafers can be skipped. Intel did not mention the costs associated with re-spinning all of their designs to be able to go from planar to fins (this will be the topic of a future Siliconisms blog post). To be sure, old planar transistor models must be replaced.
Intel’s promotion of this transistor architecture includes extensive mention of Atom chips and mobile applications. The company clearly wants everyone to still think of Intel when we think of mobile computing, despite the stunning failures of Atom chips to compete with ARM-cores in the last few years. The raw transistor performance boost of 22nm finFETs will certainly provide an advantage over 32nm planar FETs, and so Intel’s less-efficient Atom chips may win some sockets from the ARM hordes while the rest of the industry catches up to 22nm.