November 25, 2001 2:45 PM PST

Intel transistors fight the power

Transistors, the microscopic circuits that animate semiconductors, are going to be flipping off and on a trillion times a second in a few years, a prospect that is forcing Intel back to the drawing board.

In a presentation at the International Electron Devices meeting next week in Washington, D.C., the Santa Clara, Calif.-based chip giant will shed light on a series of major changes coming to the design of its transistors--culminating in the "Terahertz" transistor in the second half of the decade--that ideally will keep a lid on the growing problem of power consumption.

Overall, the pending chemical and architectural changes will let Intel by 2007 manufacture chips that contain a billion transistors but consume about the same amount of power as today's processors.

"If nothing is done, Moore's Law is going to be throttled," said Rob Willoner, a researcher in the Logic Technology Group at Intel. "Power consumption is running away from us...This is aiming at the heart of the problem."

The presentation will also no doubt spark a technological space race with IBM. One of Intel's proposed changes involves incorporating a version of silicon-on-insulator (SOI) technology into its chips, a technology IBM already uses and that Intel has roundly criticized. IBM will also present papers at the conference on advancements to its own version of SOI.

Transistors are the red blood cells of computing, tiny units that ferry electronic signals across semiconductors that eventually get orchestrated into higher commands. Under Moore's Law, the number of transistors on a chip doubles roughly every two years through, among other factors, shrinking the transistors. The transistor explosion has allowed computers to experience continual improvements in performance.

That means some awfully complex devices by the second half of the decade. Some chip elements then will measure 20 nanometers wide, 1/250th the width of a human hair. Processors will contain a billion transistors (compared with 42 million today on a Pentium 4) switching off and on a trillion times a second. In human terms, it would take a person 15,000 years to flip a light switch a trillion times, Willoner said. Current transistors top out at 100 billion operations per second.

Unfortunately, smaller, faster transistors require increasing amounts of power, which creates a host of problems. Without any structural changes, for instance, future power-hungry chips will exude more heat, proportionally speaking, than the sun. While companies are examining a wide variety of power-reduction technologies, no one is really certain which ones will succeed.

"Physics was once our friend," said Nathan Brookwood, an analyst at Insight 64. "Now, it is our enemy."

The Terahertz transistor will contain three major changes, Willoner noted. First, the transistors will feature thicker source and drain regions, substructures inside individual transistors that allow electrical current to pass. Second, the company will embed an insulating layer, called Ultra Thin SOI, below the source and drain.

Third, Intel will change the chemical composition of the gate oxide, a layer that connects the transistor gate to the source and drain. (The transistor gate sits between and above the source and drain. When the gate is charged, current passes from the source to the drain, which roughly switches the transistor from a "0" state to a "1" state to correspond with binary data.)

All three improvements are independent but work toward the same goal: allowing transistors to use electricity more efficiently.

Thickening the source and drain regions, for instance, and changing the chemical composition of the gate oxide will help stem gate leakage, current that leaks out of the gate. As transistors get smaller, more current


Gartner analyst Tom Austin says that while "impossible" leaps in technology will continue to happen at least through 2011, they won't necessarily trigger corresponding growth in the IT market.

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escapes from them, forcing designers to pump in even more electricity, which then generates even more heat.

The addition of the SOI layer will also lower resistance to the flow of current across the source and drain. Ultimately, lower resistance can either let designers lower power consumption or improve performance at a given level of energy.

Other benefits also will likely appear. Free-floating alpha particles that come in contact with a transistor on current chips can switch a transistor's state unexpectedly and cause errors. In the future, the Ultra Think SOI layer will absorb these, Willoner said.

Much work remains, however. Intel has yet to determine the chemical composition of the gate oxide. Currently, gate oxides are made of silicon dioxide. Future candidates include oxides from aluminum, titanium or other materials.

These changes will be incorporated into processors at separate times but at some point during the second half of the decade will all be standard features in Intel processors, Willoner said.

As far as the pending SOI debate goes, Willoner said one of the reasons Intel has been skeptical of IBM's version of SOI is that it doesn't perform as well as it should. It helps reduce energy consumption, or conversely improve performance, but not economically, he said. Additionally, Intel's version of SOI is far easier to design into processors.

IBM representatives could not be reached for comment, but sources inside IBM's microelectronics division said some of Intel's plans look like IBM's version of SOI "in disguise."

 

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