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A Transition For Transistors?

Intel may have made its bread and butter on silicon, but the chip making giant is considering using new types of metals in its future chips.

The Santa Clara, Calif.-based company said constant problems with electrical current leakage in its transistors have prompted it to develop high-performance transistors using a new material, called high-k, for the "gate dielectric" and new metal materials for the transistor "gate."

Transistors are the microscopic, silicon-based switches that process the ones and zeros of the digital world. The gate turns the transistor on and off and the gate dielectric is an insulator underneath it that controls the flow of electric current. For the last 30 years, silicon dioxide has served as the material of choice for this key transistor component because of its manufacturability and its ability to deliver continued transistor performance improvements at smaller sizes.

Now, Intel researchers say the new gate and gate dielectric materials help drastically reduce current leakage that leads to reduced battery power and generates unwanted heat. Intel said the new high-k material reduces leakage by more than 100 times over the silicon dioxide used for the past three decades.

Intel said it will use this advancement along with other innovations, such as strained silicon and tri-gate transistors, to extend transistor scaling and Moore's Law .

"This allows us to continue the historical rates of progress," Intel senior vice president and general manager of the Technology and Manufacturing Group Sunlin Chou said during a conference call to reporters. "Otherwise, progress would slow down or even stop. The most significant thing is that this shows you can get away from the good old silicon dioxide. Once you've demonstrated you can make a change, the thought of yet another change somehow doesn't seem nearly as intimidating as if you can't even demonstrate the first change."

Chou says the new discoveries can be integrated into an economical, high-volume manufacturing process, and is now moving this transistor research into the development phase. Intel says the transistors with these new materials are an option targeted to be integrated into future Intel processors as early as 2007, as part of the company's 45-nanometer (nm) manufacturing process.

On the road to making smaller and faster processors, Intel says it has successfully shrunk the silicon dioxide gate dielectric to sizes as small as 1.2-nm thick, which is equal to only five atomic layers. The problem, say researchers, is as the silicon dioxide material gets thinner, electric current leakage through the gate dielectric increases and leads to wasted current and unnecessary heat. To keep electrons flowing in the proper location and solve this critical issue, Intel plans to replace the current material with a thicker high-k material in the gate dielectric.

The company says the second part of the solution is the development of a metal gate material, but did not specifically identify which metal it would use. The material would have to be compatible with today's transistor gates since the high-k gate dielectric is not. Intel says the combination of the high-k gate dielectric with the metal gate enables a drastic reduction in current leakage while maintaining very high transistor performance.

Intel is expected to discuss details of the development of new transistor materials at the 2003 International Workshop on Gate Insulator in Tokyo this week.