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Your current location :Home > News > Moores Law The rule that really matters in tech

Moores Law The rule that really matters in tech

In 1965, Intel co-founder Gordon Moore foresaw an inexorable rise in chip power that eventually delivered the computer to your pocket. While long in the tooth, Moores prediction still has plenty of life in it. Heres why.

Intel co-founder Gordon Moore speaking in 2007 at the Intel Developer Forum in San Francisco.

Year in, year out, Intel executive Mike Mayberry hears the same doomsday prediction: Moores Law is going to run out of steam. Sometimes he even hears it from his own co-workers.

But Moores Law, named after Intel co-founder Gordon Moore, who 47 years ago predicted a steady, two-year cadence of chip improvements, keeps defying the pessimists because a brigade of materials scientists like MayberMoores Law The rule that really matters in tech,ry continue to find ways of stretching todays silicon transistor technology even as they dig into alternatives. (Such as, for instance, super-thin sheets of carbon graphene.)

Oh, and dont forget the money thats driving that hunt for improvement. IDC predicts chip sales will rise from $315 billion this year to $380 billion in 2016. For decades, that revenue has successfully drawn semiconductor research out of academia, through ctories, and into chips that have powered everything from a 1960s mainframe to a 2012 iPhone 5.

The result: Moores Law has long passed being mere prognostication. Its the marching order for a vast, well-funded industry with a record of overcoming naysayers doubts. Researchers keep finding ways to maintain a tradition that two generations ago would have been science fiction: That computers will continue to get smaller even as they get more powerful.

If youre only using the same technology, then in principle you run into limits. The truth is weve been modifying the technology every five or seven years for 40 years, and theres no end in sight for being able to do that, said Mayberry, vice president of Intels Technology and Manucturing Group.

Plenty of other industries arent as fortunate. You dont see commercial supersonic airplane travel, home fusion reactors, or 1,000-mile-per-gallon cars. But the computing industry has a fundamental flexibility that others lack: its about bits, not atoms.

Automobiles and planes are dealing with the physical world, such as the speed of sound and the size and mass of the humans they carry, said Sam Fuller, chief technology officer of Analog Devices, a chipmaker thats been in the electronics business even longer than Intel. Computing and information processing doesnt have that limitation. Theres no fundamental size or weight to bits. You dont necessarily have the same constraints you have in these other industries. There potentially is a way forward.

To shrink its microprocessor circuitry elements to todays 22-nanometer size -- just 22 billionths of a meter -- Intel had to develop a technology called tri-gate transistors in which silicon semiconductor material protrudes in fin-shaped ridges.

That means that even if Moores Law hits a wall and chip components stop shrinking, there are other ways to boost computer performance.

This chart from Intel co-founder Gordon Moores seminal 1965 showed the cost of transistors decreased with new manucturing processes even as the number of transistors on a chip increased.

Before we get too carried away with lauding Moores Law, be forewarned: Even industry optimists, Moore included, think that about a decade from now there could be trouble. Yes, all good things come to an end, and at some point those physical limits people have been predicting will turn out to be real.

To understand those limits and how they may be overcome, I talked to researchers at the big chip companies, academics, and industry gurus. I wanted to go beyond what what most of us think we know about semiconductors and hear it from the experts. Do they have doubts? What are they doing about those doubts? The overwhelming consensus among the chip cognescenti, I found, was, yes, theres a stumbling block a decade or so from now. But dont be surprised if we look back at that prediction 20 years from now and laugh.

For related coverage, see what would happen if Moores Law fizzled and a Q&ther fixes include gates out of metal, connecting transistors with copper rather than aluminum wires, and using strained rather than ordinary silicon for the channel between source and drain.

In 2013, Intel plans another shrink to a 14nm process. Then comes 10nm, 7nm, and, in 2019, 5nm.

And its not just Intel up these numbers. In the chip business, a fleet of companies depend on coordinated effort to make sure Moores Law stays intact. Combining academic research results with internal development and cross-industry cooperation, they grapple with quantum-mechanics problems such as electron tunneling and current leakage -- a bugaboo of incredibly tiny components in which a transistor sucks power even when its switched off.

Doom and gloom

Given the engineering challenges, a little pessimism hardly seems out of place.

Intels current chip manucturing road map extends to the 5nm process node, scheduled to arrive in chips in 2019.

A 2005 Slate article bore the title, The End of Moores Law. In 1997, the New York Times declared, Incredible Shrinking Transistor Nears Its Ultimate Limit: The Laws of Physics, and in another piece quoted SanDisks CEO forecasting a brick wall in 2014. In 2009, IBM Fellow Carl Anderson predicted continuing exponential growth only for a generation or two of new manucturing techniques, and then only for high-end chips.

Even Intel has fretted about the end by predicting trouble ahead getting past 16nm processes.

In decades past, Moore himself was worried about how to manucture chips with features measuring 1 micron, then later chips with features measuring 0.25 microns, or 250 nanometers. A human hair is about 100 microns wide.

Yes, there are fundamental limits -- for example, quantum mechanics describes a phenomenon called tunneling where the position of an electron cant be pinned down too precisely. From a chip design point of view, that turns out to mean that an electron can essentially hop from source to drain, degrading a chip with leakage current.

So is there an end to Moores Law? In a 2007 interview, Moore himself said, There is. He continued:

Any physical quantity thats growing exponentially predicts a disaster. It comes to some kind of an end. You cant go beyond certain major limits... But its been amazing to me how technologists have been able to keep pushing those out ahead of us. For about as long as I remember, the fundamental limits were about two or three generations out. So r weve been able to get around them. But I think another decade, a decade and a half, or something, well hit something that is irly fundamental.

That was five years ago, and few seem to want to venture too much rther beyond Moores prediction.

I think we have at least a decade before we start getting into issues, said Patrick Moorhead, analyst at Moor Insights & Strategy. I still give it another decade, added Robert Mears, founder and president of Mears Technologies, which has developed a technology called MST CMOS designed to improve the performance of the conventional silicon channel.

Beyond silicon

Although Moores Law might not continue if transistors cant be shrunk, the post-silicon future shouldnt be overlooked. When traditional silicon transistors eventually run out of gas, there are plenty of alternatives waiting in the wings.

The most probable outcome is that silicon technology will find a way to keep scaling, some way continue to deliver more value with succeeding generations, said Nvidia Chief Scientist Bill Dally.

One likely candidate keeps the same basic structure as todays transistors but speeds them up by breaking out of todays constraints in the periodic table of the elements. In transistors now, the source, drain, and channel are made from silicon, which inhabits a column of the periodic table called group IV.

But its possible to use indium arsenide, gallium arsenide, gallium nitride or other so-called III-V materials from group III and group V. Being from different groups on the periodic table means transistor materials would have different properties, and the big one here is better electron mobility. That means electrons move ster and transistors therefore can work ster.

You can imagine staying with irly traditional transistors, moving to silicon-germanium, then III-V structures, Fuller said. But thats mostly a stopgap. There is some potential future in that, but it pretty quickly runs into similar limits that hit silicon. There may be [performance improvement] ctors of two, four, maybe eight to be gained.

IBM is working on replacing silicon channels in transistors with carbon nanotubes. These images show a schematic and real-world images of such a device. Image b shows a top view, image c shows a cross section, and image d shows an end-on view.

Another tweak could replace the silicon channel with nanowires, super-thin wires made of various semiconductor materials (including, it so happens, lowly silicon itself). More exotic and more challenging is the possibility of using carbon nanotubes instead. These are made of a cylindrical mesh of interlinked carbon atoms that can carry current, but there are lots of difficulties: connecting them to the rest of the transistor, improving their not-so-hot semiconductor properties, and ensuring the nanotubes are sized and aligned correctly.

Glorious graphene

Which brings us to one of the most promising post-silicon candidates: graphene, a flat honeycomb lattice of carbon that resembles atomic chicken wire. If you roll up a sheet of graphene, you get a nanotube, but it turns out the flat form also can be used as a semiconductor.

One advantage graphene holds over carbon nanotubes is the possibility that it can be manuctured directly as a step in the wafer processing that goes on in chip ctories, instead of being bricated separately and added later. (This is a very big deal in the intricate and minutely choreographed business of chip manucture.) Another is that its got ntastically high electron mobility, which could make for very st switching speeds if graphene is used to connect source and drain in a transistor.

I think graphene is very promising, Fuller said.

But graphene has plenty of challenges. First on the list: it lacks the good band gap, a separation in energy levels that determines whether a semiconductor conducts electrons or insulates. Graphene by itself has a band gap of zero, meaning that it just conducts electricity and ils as a semiconductor.

Graphene has some very nice properties, but as it stands at the moment, it doesnt have a proper band gap, Robert Mears, president of Mears Technologies. Its not really a replacement for silicon or other semiconductor materials. Its a good connect medium, conductor, but not necessarily a good switch at the moment.

IBM has figured out how to build a graphene-based transistor on an integrated circuit geared for wireless communication purposes, not for computing.

Heres how Fuller describes an ideal transistor: When you turn on, it comes on strong, and when you turn it off, it consumes almost no power. Thats what you want for a great logic gate. The problem so r, though. is that the graphene transistors today have been hard to turn off.

But there are ways to give the material a band gap, including using two separated strips of graphene bricated as nanoribbons. Varying the placement of the transistor gate or gates also can help. If scientists work out the challenges, the result could be a transistor thats not necessarily smaller, but that is a lot ster.

Were in the early days of exploring the use of graphene, like we were with silicon a long time ago -- in the 1950s, maybe, Fuller said.

But wait, theres more

Another radical approach is called spintronics, which relies on information being transmitted within a chip using a property of electrons called spin.

If you could use spin to store a 1 or a 0, rather than charge or absence of charge, it doesnt have the same thermodynamic limits that moving charge around does, Fuller said. You probably wouldnt run into the same power limits.

Silicon photonics, in which light rather than electrons carry information, could be involved in future chips.

That can be a great partial solution between chips, or even on chips, Fuller said. Today, a large fraction of a chips power is used to keep the chip components marching lockstep by broadcasting ticks of the chips clock, but there are promising research projects to do that with optical links.

There are limits to how short optical links get, said Mears, who by the way invented the erbium-doped fiber amplifier (EDFA) technology that vastly improved fiber-optic network capacity. The problem: the wavelength of light is inconveniently large compared to chip components, he said.

In spite of it having been one of my main research subjects, Im not a great n of optics on a chip, Mears said. Any kind of optical waveguide on a chip will look huge compared to the kinds of devices you can put on a chip.

The chip industry treadmill involves tackling a constant series of challenges. Intel has maintained an ability to predict whatll happen for about the next decade.

Fuller concurred. What makes it great for communicating over long distances makes it difficult to make a logic gate out of them: photons dont interact with each other. If you want to build a NOR gate or NAND gate [two forms of basic logic gates out of which chips are assembled], you need to switch from photons to electrons for the gate, then back to photons to transmit the data, he said.

Mayberry is keeping an eye on so-called spintronics, but as with many technologies hes cautious. A spin wave travels at a slower rate than an electron wave, he notes. There are also numerous manucturing challenges.

Beyond that, theres a wide range of even more exotic research under way -- quantum computing, DNA computing, spin wave devices, exitonic field-effect transistors, spin torque majority gates, bilayer pseudospin field-effect transistors, and more. An industry consortium called the Nanoelectronics Research Initiative is monitoring the ideas.

There are something like 18 different candidates theyre keeping track of. Theres no clear winner, but there are emerging distinctive trends that will help guide future research, Mayberry said.

Its certainly possible that computing progress could slow or fizzle. But before getting panicky about it, look at the size of the chip business, its importance to the global economy, the depth of the research pipeline, and the industrys continued ability to deliver the goods.

Theres an enormous amount of capital thats highly motivated to make sure this continues, said Nvidias Dally. The good news is were pretty clever, so well come through for them.

Stephen ShanklandStephen Shankland writes about a wide range of technology and products, but has a particular focus on browsers and digital photography. He joined CNET News in 1998 and has also covered Google, Yahoo, servers, supercomputing, Linux, other open-source software, and science.

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