Tag Archives: CMOS

Moore’s Law Smells Funny

…maybe we need “Integrated Cleverness Law”

“Jazz is not dead, it just smells funny.” – Frank Zappa 1973
from Be-Bop Tango (Of The Old Jazzmen’s Church)

Marketing is about managing expectations. IC marketing must position next-generation chips as adding significant new/improved functionalities, and for over 50 years the IC fab industry has leaned on the conceptual crutch of “so-called Moore’s Law” (as Gordon Moore always refers to it) to do so. For 40 years the raw device count was a good proxy for a better IC, but since the end of Dennard Scaling the raw transistor count on a chip is no longer the primary determinant of value.

Intel’s has recently released official positions on Moore’s Law, and the main position is certainly correct:  “Advances in Semi Manufacturing Continue to Make Products Better and More Affordable,” as per the sub-headline of the blog post by Stacy Smith, executive vice president leading manufacturing, operations, and sales for Intel. Smith adds that “We have seen that it won’t end from lack of benefits, and that progress won’t be choked off by economics.” This is what has been meant by “Moore’s Law” all along.

When I interviewed Gordon Moore about all of this 20 years ago (“The Return of Cleverness” Solid State Technology, July 1997, 359), he wisely reminded us that before the industry reaches the limits of physical scaling we will be working with billions of transistors in a square centimeter of silicon. There are no ends to the possibilities of cleverly combining billions of transistors with sensors and communications technologies to add more value to our world. Intel’s recent spend of US$15B to acquire MobileEye is based on a plan to cost-effective integrate novel functionalities, not to merely make the most dense IC.

EETimes reports that at the International Symposium on Physical Design (ISPD 2017) Intel described more than a dozen technologies it is developing with universities and the SRC to transcend the limitations of CMOS. Ian Young, a senior fellow with Intel’s Technology Manufacturing Group and director of exploratory integrated circuits in components research, recently became the editor-in-chief of a new technical journal called the IEEE Journal of Exploratory Solid-State Computational Devices and Circuits, which explores these new CMOS-fab compatible processes.

Meanwhile, Intel’s Mark Bohr does an admirable job of advocating for reason when discussing the size of minimally scaled ICs. Bohr is completely correct in touting Intel’s hard-won lead in making devices smaller, and the company’s fab prowess remains unparalleled.

As I posted here three years ago in my “Moore’s Law Is Dead” blog series, our industry would be better served by retiring the now-obsolete simplification that more = better. As Moore himself says, cleverness in design and manufacturing will always allow us to make more valuable ICs. Maybe it is time to retire “Moore’s Law” and begin leveraging a term like “Integrated Cleverness Law” when telling the world that the next generation of ICs will be better.


The Last Technology Roadmap

After many delays, the last ever International Technology Roadmap for Semiconductors (ITRS) has been published. Now that there are just a few companies remaining in the world developing new fab technologies in each of the CMOS logic and memory spaces, each leading-edge company has a secret internal roadmap and little motivation to compare directions within fiercely competitive  commercial markets. Solid State Technology Chief Editor Pete Singer covered these developments in his blog post early last year.

Rachael Courtland at IEEE Spectrum provides a great overview of the topic and interviews many of the key contributors to this last global effort. The article provides a nice graph to show how the previously predicted (in the just-prior ITRS 2013 edition) continued physical gate length reduction of CMOS transistors is now expected to stop in 2020. Henceforth, 3D stacking of transistors—perhaps built with arrays of Gate-All-Around NanoWires (GAA-NW)—will be the only way to get more density in circuitry but it will come with proportionally increasing cost.

As Gary Patton, CTO and SVP of Worldwide R&D for GlobalFoundries, mentioned during the 2016 Imec Technology Forum in Brussells, “We will continue to provide value to our customers to be able to create new products. We’re going to innovate to add value other than simple scaling.”

The 17 International Technology Working Groups (ITWGs) were replaced in 2015 by 7 Focus Teams in the last ITRS:  System Integration, Heterogeneous Integration, Heterogeneous Components, Outside System Connectivity, More Moore, Beyond CMOS and Factory Integration. The final reports from each Focus Team are available for free download from Dropbox.

The IEEE Rebooting Computing Initiative, Standards Association, and the Computer Society announced a new International Roadmap for Devices and Systems (IRDS) on 4th of May this year. Paolo Gargini is leading this work that began with the partnership between the IEEE RC initiative and the ITRS, with aspiration to build “a comprehensive end-to-end view of the computing ecosystem, including devices, components, systems, architecture, and software.”

In parallel to the IRDS efforts, the Heterogeneous Integration Roadmap activities will continue as sponsored by IEEE Components, Packaging and Manufacturing Technology Society (CPMT), SEMI  and the IEEE Electron Devices Society (EDS). Bill Bottoms is leading this collaboration with other IEEE Technical Societies that share interest in the Heterogeneous Technology Roadmap as well as to organizations outside IEEE that share this common vision for the roadmap.


CMOS-Photonic Integration Thermally Sensitive

As published in the journal Nature, CMOS transistors have been integrated with optical-resonator circuits using complex on-chip sensors and heaters to maintain temperature to within 1°C. While lacking the laser-source, these otherwise-fully-integrated solutions demonstrate both the capability as well as the limitation of trying to integrate electronics and photonics on a single-chip. The Figure shows a simplified schematic cross-section of the device.

Full chip cross-section (not to scale) from the silicon substrate to the C4 solder balls, showing the structures of electrical transistors, waveguides, and contacted optical devices. The minimum separation between transistors and waveguides is <1 μm, set only by the distance at which evanescent light from the waveguide begins to interact with the structures of the transistor.

Full chip cross-section (not to scale) from the silicon substrate to the C4 solder balls, showing the structures of electrical transistors, waveguides, and contacted optical devices. (Source: Nature)

Lead author Chen Sun—affiliated with UC Berkeley and MIT, as well as with commercial enterprise Ayar Labs, Inc.—developed the thermal tuning circuitry, designed the memory bank, implemented the ‘glue-logic’ between various electronic components, and performed top-level assembly of electronics and photonics. The main limitation is the temperature control, since deviation by more than 1°C results in loss of coupling that otherwise provides for P2M/M2P transceivers:

* Waveguide Loss – 4.3 dB/cm,
* Tx and Rx Data Rate – 2.5 Gb/s,
* Tx Power – 0.02 pJ/bit,
* Rx Power – 0.50 pJ/bit, and
* Ring Tuning Control Power – 0.19 pJ/bit, so
* Total power consumption = 0.71 pJ/bit.

The Register reports that this prototype has a bandwidth density of 300 Gb/s per square millimetre, and needs 1.3W to shift a Tb/s straight from the die to off-chip memory. A single chip integrates >70 million transistors and 850 photonic components to provide microprocessor logic, memory, and interconnect functions.


Batteries? We don’t need no stinking batteries.

We’re still used to thinking that low-power chips for “mobile” or “Internet-of-Things (IoT)” applications will be battery powered…but the near ubiquity of lithium-ion cells powering batteries could be threatened by capacitors and energy-harvesting circuits connected to photovoltaic/thermoelectric/piezoelectric micro-power sources. At ISSCC2015 in San Francisco last week, there were several presentations on novel chip designs that run on mere milliWatts (µW) of power, and the most energy efficient circuit blocks now target nanoWatt (nW) levels of power consumption. Two presentations covered nW-scale microprocessor designs based on the ARM Cortex-M0+ core, and a 500nW energy-harvesting interface based on a DC-DC converter operating from 1µm available power was shown by a team from Holst Centre/imec/KU Leuven working with industrial partner OMRON.

Read more on this in MicroWatt Chips shown at ISSCC available at SemiMD.