IBM Advances New Form of Transistor to Improve Chips

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EAST FISHKILL, N - 03 Dec 2001: ... IBM today announced advances in the development of an alternate type of transistor -- the basic building block of microchips -- that could lead to major performance, function and power consumption improvements in semiconductors within several years.

Called a "double-gate" transistor, the device can carry twice the electrical current, operate at up to twice the speed and be reduced in size well below today's conventional transistors. The opportunity for further miniaturization is key, as the dimensions of the traditional transistor are reaching the limits imposed by the law of physics, threatening to slow the gains in performance that are required for high-speed communications, information systems and consumer electronics.

The breakthrough was made possible by a series of innovations from IBM in new device designs and materials such as SOI, a chip-making material that IBM pioneered and that is now becoming a standard in the industry. IBM's expertise in SOI is allowing scientists to alter the design of the transistor in ways not possible before, while still allowing them to be built on conventional manufacturing lines. SOI continues to enable IBM to produce leadership technology for conventional, high-performance Complementary Metal Oxide Semiconductors (CMOS), both in manufacturing and development.

IBM's work on the double-gate transistor and the latest SOI developments will be presented as part of more than 20 papers delivered this week at the International Electronic Device Manufactures (IEDM) conference in Washington, D.C.

"SOI is changing the rules in semiconductors," said Bijan Davari, vice president of semiconductor development at IBM Microelectronics. "Other than getting smaller, the basic transistor has largely gone unchanged for decades, but it has now been shrunk nearly to a point where it will cease to function. Fortunately, our wealth of experience using SOI allows us to change the basic design of the transistor, permitting further shrinkage and other improvements."

IBM overcame a number of challenges that have held back the research of these experimental double-gate transistors at labs throughout the industry, taking a significant step toward manufacturability. Improved transistors, such as the double-gate, are expected to be needed in five-to-ten years, when transistors shrink so small, it becomes difficult to shut them off.

The transistor -- a type of electrical on/off switch -- is the key component of the integrated circuit, or microchip. The performance of the chip depends largely on the ability of its millions of transistors to switch on and off quickly and completely, and to require the least amount of energy to do so.

Within a transistor, an element called a "gate" controls the electrical flow through the transistor. However, as transistors continue to shrink, it becomes more difficult for a single gate to effectively control switching. In IBM's double-gate transistor, the channel is surrounded by two gates, doubling control of the current and enabling significantly smaller, faster and lower-power circuits.

The work on double-gate transistors is the culmination of a multi-year collaborative effort between the IBM Research and Microelectronic Divisions. With this announcement, IBM has moved the double-gate transistor from the purely theoretical to a structure that shows potential for actual use in chips in the future. While others in the industry have long studied the use of double gate transistors, there have been a number of problems associated with previous experimental designs that IBM has been able to overcome, such as electrical leakage, high energy demands and poor electrical flow. IBM's double gate design solves many of these problems for the first time, helping double gate technology turn a major corner toward eventual production.

Other IBM papers being presented at the conference include:

Over the past four years, IBM's labs have turned out a number of groundbreaking technologies that have changed the industry and given IBM a lead in semiconductor technologies.

In 1997, IBM engineers improved the connections between transistors by allowing copper (a better conductor of electricity) to be substituted for aluminum. Another IBM breakthrough came in 1998, when IBM turbocharged transistor technology with its unique silicon-on-insulator process that allows chips to run faster. That same year, IBM became the first company to mass produce chips made of silicon germanium to speed communications products. Then, in 2000, IBM unveiled a new manufacturing technique that uses a material known as a "low-K dielectric" to effectively shield millions of individual copper circuits on a chip, reducing electrical " crosstalk" between wires that can hinder chip performance and waste power.

Earlier this year, IBM announced a breakthrough method to alter silicon called "strained silicon", a technology that stretches the silicon material, speeding the flow of electrons through transistors to increase performance and decrease power consumption in semiconductors -- which is expected to boost chip speeds by up to 35 percent.

Images relating to this work can be found at:

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