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Last Updated: Thursday, 17 August 2006, 12:47 GMT 13:47 UK
Speedy silicon sets world record
Modern circuits contain millions of transistors
A simple tweak to the way common silicon transistors are made could allow faster, cheaper mobile phones and digital cameras, say UK researchers.

Devices with the modification have already set a new world record for the fastest transistor of its type.

To achieve the speed gain, researchers at the University of Southampton added fluorine to the silicon devices.

The technique uses existing silicon manufacturing technology meaning it should be quick and easy to deploy.

"It just takes a standard technology and adds one extra step," said Professor Peter Ashburn at the University of Southampton, who carried out the work. "This is a really cheap method."

Silicon sandwich

The research was carried out using a simple type of transistor known as a silicon bipolar transistor.

Transistors are the tiny building blocks of most microchips and millions are found in desktop computers, mobile phones and MP3 players.

It's atomic engineering really, even smaller than nanotechnology
Professor Peter Ashburn

They are used to regulate electronic currents in microchips, and depending on the type may be used to amplify a signal or open and close a circuit.

Combinations of transistors can be used to do calculations or useful computational work.

Bipolar transistors are made of three layers of semi-conducting material arranged in a sandwich structure, with two layers of one material with a filling of a different sort.

A thinner filling in the transistor means electrons can flow through the device more quickly, increasing the overall speed of a circuit or chip.

Alternative approaches for building fast transistors exist but they use other materials, such as gallium arsenide or a silicon germanium mix, which require more expensive manufacturing techniques.

The silicon industry would like to continue to squeeze greater speeds out of smaller chip using existing manufacturing processes which are cheap and reliable.

The work from the University of Southampton offers one solution.

Atomic scales

Professor Ashburn and colleagues at ST Microelectronics used a simple transistor made of silicon with a boron filling for the research.

To make transistors of this type requires high temperature manufacturing processes which cause the boron layer to diffuse, creating a thicker and hence slower layer.

A man looks at the latest mobile phones
The new chips could be used in mobile phones

To get round this problem, the researchers added fluorine implants to the silicon layers using a common manufacturing process, known as ion implantation.

Ion implantation involves firing atoms of one element, in this case fluorine, at a target of silicon.

At an atomic level, the fluorine creates small clusters of vacancies, areas of missing silicon atoms. These voids suppress boron diffusion, creating a thinner layer and therefore speeding up the transistor.

"It's atomic engineering really, even smaller than nanotechnology," said Professor Ashburn.

World record

When the researchers tested the new device it clocked a speed of 110 GHz.

Complete circuits usually operate at about a tenth of the speed of the component transistors meaning the new devices could allow engineers to build chips that operate at a speed of about 11GHz.

There's no Guinness Record for this but it is the fastest in the published literature
Professor Ashburn

The previous world record, held by electronic giant Philips, created transistors that operate at speeds of up to 70GHz, allowing operating circuit speeds of 7GHz.

"There's no Guinness Record for this but it is the fastest in the published literature," said Prof Ashburn.

At present, mobile phone circuits operate at speeds of about 1GHz.

Working circuits using the new design of transistor are currently being developed by Professor Ashburn's research partner ST Microelectronics in Italy.

Although a product has not been built using the new devices, Prof Ashburn says they could be used to amplify the signal in mobile phones or to improve the way that handsets convert speech into digital signals.

Complete circuits are also used in digital cameras or scanners to improve the way they convert information from the real world into pixels.

"There are many applications," said Professor Ashburn.

Chilly chip shatters speed record
20 Jun 06 |  Technology
Nano circuit offers big promise
24 Mar 06 |  Science/Nature
IBM squeezes more into microchips
21 Feb 06 |  Technology
Law that has driven digital life
18 Apr 05 |  Science/Nature

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