Don't these sloped fins cause a lot of variation?
The device channel orientation is random vs 110 for ideal finfet and 100 for planar (mobility and many sources of variation)
Fin thickness depends on sidewall slope....and fin thickness sets my leakage and device threshold voltage, right?
I have bee puzzled why everyone claims trigate lowers standby leakage BUT I don't see any improvement in standby power at the chip level for intels 22nm ivy bridge??
Could this be the reasons leakage improvement does not match expectation for "ideal trigate".
Corner leakage is usually a problem, but so is reproducability and control. It is difficult to know from so little data, how much of this triangle approach is for leakage vs. process control (yield). If the power levels don't give a dividend it will all be for naught.
Perhaps it was intentional to flood the media with sketches& even SEMs of rt. angled fins so that the pretenders and knock off artists would be misled for a while. But the important thing is that the power consumption for Ivy Bridge ( 22 nm, FinFET ) is NOT yet significantly less than Sandy Bridge to get a foot in the door at the SoC for SmartPhones house.
iniewski has it right on one aspect.
Avoiding sharp corners is plausible advantage.
The second aspect I suspect is the ability to measure sidewall roughness without sidewall afm - atomic force microscopy that taps laterally ( the old IBM AFM that was a poor machine ). Here with sloped sidewalls, a topview high resolution SEM electron microscope images sidewalls usefully, and a comventional AFM topview tapping more trivially gets the needed "sidewall" roughness quantitaitvely measured with little difficulty versus the challenging vertical 90deg sidewall. And manufacturing metrology ease and accuracy of roughness here, which is a critical device parameter, since the surface is ETCHED ( worst thing you normally might do for a desired atomically smooth surface )...
Hence I suspect nano- metrology aspects are the driver ( this being a process engineer's perspective, not theoretical in the slightest )
Simplest way to put it, rectangles have one more corner than triangles. Besides process variation, corners tend to have leakage current affecting off-stage performance, such as Vt and Ioff. In addition, the equivalent width of the FinFET may be easier to scale and control in triangular shape than in rectangular shape. It will be interesting to see NMOS vs PMOS with various width and how the width scaling is done.
Avoiding sharp corners is always a good idea in silicon manufacturing due to electric field crowding in device operation...and even if you wanted sharp fin it would be difficult to make it always equally sharp hence yeild hit...I suspect 2012 pics were of the marketing types...Kris
I suspect that the "triangle" shape represents some compromise between what is simple and reproducible to fabricate with regards to high volume manufacturing considerations, and what is the ideal shape from from an electrical standpoint. It is also a more mechanically robust shape for a relatively high aspect ratio structure (less likely to break due to vibration, etc.).
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