Inside the Clean Room of Fab 36

Imagine if every time you reached office, you had to change into a T-shirt and sweat pants. You had to change your shoes, put on two masks, one to cover your hair, and the other to cover everything above your shoulders. You then had to put on another suit to cover the rest of your body, and as if that was not enough, you even had to wear two types of gloves! Sounds unbelievable and something you would never do? Well, that's exactly what the dress is code for a clean room, which is the place where microprocessors are manufactured. I had the opportunity to visit the clean room of AMD's latest microprocessor fabrication facility in Dresden Germany, called Fab 36. The experience of course was equally extraordinary. With the opening of this fab, AMD expects to double its microprocessor shipments to 100 million units by 2007. The Fab 36 uses 300 mm wafers and is capable of producing at 65 nm. One of the reasons that Dresden was chosen as the site was that AMD already had a Fab there (called Fab 30), which had been successfully running ever since it was brought up. An interesting aside, the number 36 in Fab 36 indicates the number of years that AMD's been in existence (same for Fab 30 and the rest of AMD's

fabs).

Investments worth $2.5 billion have already gone into Fab 36, and an equal amount more is expected by 2007

All the dress-up I described may sound odd, but that's what all employees (or visitors like me) going in a clean room have to wear, and not without good reason. Clean rooms are highly sensitive areas, where even the slightest amount of dust or other particles can harm the production. To be more precise, even the vapor from an after-shave lotion, or particles from a woman's make-up are enough to spoil the production of microprocessors.Clean rooms are a symbol of cutting edge technology, and the outfit isn't the only way of keeping it clean. The area is humidity controlled, temperature controlled, and even the entire air in the area is completely recycled every 90 seconds. 

The air inside the fabrication machines is kept even cleaner, with a tolerance of only .01% impurities. The way the microprocessor is manufactured is also really interesting. Explaining the technicalities is beyond the scope of this article, so we'll only talk about some of its interesting aspects, which I learnt at the Fab 36. 

Production of a microprocessor can be compared to cooking a recipe, with the difference that instead of food, there are Silicon wafers. While the food is put into an oven after the chef mixes all the ingredients in it, a Silicon wafer has to pass through several ovens. In each oven, a different set of ingredients are applied to it, which are various elements, gases, etc like Boron, Nitrogen, Germanium, etc. So while one oven treats it with Nitrogen, another might treat it with Ozone or Phosphorus, and yet another might treat it with Arsenic. All the production equipment is installed on a raised floor. Beneath the floor are all sorts of meters that control the flow of these gases. So basically, a different recipe is applied to the wafer in different ovens. 800 steps later, the wafer comes out with all the microprocessors etched on it, ready to go for the packaging. 

The FOUPs (below) are automatically delivered to specific process stops using the 6 kms long ceiling track shown in this picture A technician verifies the stack of Front Opening Unified Pods (FOUPs), the transportation boxes for silicon wafers

As you can imagine, it's not easy cramming those hundreds of millions of transistors on the Silicon. The 800 steps involved in AMD Fab 36 give a gist of how tedious and difficult the process is. 

The fab has been built from ground up in two years flat, right from the ground-breaking process to the installation of all the equipment. It uses the latest technologies and production equipment, and a process to control everything called Automate Precision Manufacturing, or APM for short. This allows for dynamic, real-time adjustments to the fabrication process. 

Anil Chopra