The process of making silicon chips is as complex as the chips themselves. Each manufacturing plant, or “fab”, may cost billions of dollars and is a triumph of engineering.
Nov 15, ‘07 — Dr Peter Wilson, a Senior Lecturer in Electronics at the University of Southampton, School of Electronics and Computer Science, writes an in-depth article on “Fab World” for BBCNews.
“Fab world” is like no other place on earth.
Its pristine white walls, secure air locks, sterile air and ethereal yellow lighting makes it seem like you have arrived in the belly of an orbiting space station.
Outside, we worry about dirt on our shoes and wipe our feet, or perhaps wipe some dust off our laptop screen. In fab world, we worry about a few atoms contaminating the environment.
If dust falls on the delicate silicon wafers on which chips are printed it can render them useless.
Modern transistors - the tiny switches at the heart of these devices - are described in terms of the smallest feature sizes that can be made, such as a 45 nanometres, or 45 billionths of a meter. To put this in perspective, the average human hair will be between 20 and 100 micrometers across - over a thousand times larger - and a typical dust particle will be anything from 1 to 100 micrometres.
The fab is a place for chips, not for people. As a result, only the pure and the clean are given permission to penetrate its’ inner chambers. Anyone that enters must go through a strict set of procedures.
A series of ante-chambers serve as prep rooms where workers change into a series of gowns and gloves, collectively known as a “bunny suit”.
Sticky floors make sure that no one treads in any contaminants and an air shower before entry makes certain that any loose particles are stripped away. Skin flakes, lint, hair and anything else gets sucked into the grate in the floor.
And then it’s onwards into the hum of the clean rooms. Stark white walls reflect the yellow sodium lights from above and a constant breeze blows down from the ceiling taking any particles through the gridded floor.
In modern fabs, ultra high tech chips are manufactured in what are known as class 1 rooms that contain just one tiny particle per metre cubed. In contrast, a room where open heart surgery takes place may have as many as 20,000.
Inside, humans very rarely come into contact with the rainbow-streaked discs of reflective silicon on which the chips are cut. Instead, they are there to trouble shoot and monitor that everything goes correctly. The silicon wafers are handled on monorails that move above the fab floor and the processing is done by complex vacuum sealed robots.
The wafers enter one end of the line costing a couple of hundred dollars and appear at the other - weeks later - patterned with billions of transistors and worth tens of thousands of pounds.
The silicon itself is not made at the fab - the ultra pure ingots (up to 99.99999999% pure) are produced and cut by specialist companies and sold to the chip makers. The fab world’s magic is creating the incredibly complex patterns of wires and circuitry on chips the size of a postage stamp time and time again
Each layer of a processor is constructed using a mask which is like a stencil, to highlight the areas to be deposited, etched or doped. Doping involves adding impurities to the silicon to change its electrical characteristics - something which has to be done with astonishing precision.
In addition, the size of individual features is now smaller than the wavelength of light that used to be used to pattern them, which means the use of some clever optics is required.
The yellowish lights used inside the fab are to make sure that they do not interfere with this process. Each one of the 10mm by 10mm silicon squares is a triumph of design. More at BBCNews.
Feb 04, `08 — The first chip to pack more than two billion transistors has been launched by silicon giant Intel. The quad-core chip, known as Tukwila, is designed for high-end servers rather than personal computers.
