Wafer Madness
Twenty-four hours a day at Motorola’s MOS 11 factory outside Austin, workers race to build the complex computer chips that power our brave new world. For two weeks, I was one of them.
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Some people in the gowning area had already suited up in the snow-white Gore-Tex jumpers, called gowns or bunny suits, that are the standard uniform inside the factory. The suits block flakes of dead skin or lint from escaping and fouling up the chips’ circuitry. The workers in bunny suits looked like Star Trek characters. The hood, which resembles a malleable version of a knight’s headgear, goes on first. “That’s inside out,” someone said to me as I pulled mine on. “My first day here, I put my hood on like that.” Then I tried to step into my Gore-Tex jumper without letting any part of it touch the floor, which was nearly impossible to do without falling over. Finally, I pulled on knee-high Gore-Tex boots and put on latex gloves and a face mask. When I was finished, just the skin around my eyes remained uncovered. Willis put on safety glasses, but I didn’t, because I wear glasses anyway. Employees said that putting everything on and then taking it all off every time they leave the third floor is one of the most tiresome things about working in the factory. At the same time, some people like the feeling of anonymity or authority that the suit gives them. “I was in the military, so I look at it as getting dressed for duty,” said Willis. Unless supervisors happen to be carrying a two-way radio, which is a status symbol, it is hard to pick them out of a crowd. But social interactions are not entirely muffled by the suits—operators learn to recognize acquaintances by their build or walk and to gauge a range of feelings by their co-workers’ eyes. They know when someone is smiling from the crinkles behind the safety glasses.
Once we had suited up, I got a lint-free notebook, with pages that were laminated with a barely discernible layer of plastic, and a low-sodium pen. (The sodium in the ink of a normal ballpoint pen can paralyze a factory because it can become a charged ion, travel through the air, and alter the electrical properties of the wafers it lands on.) Then Willis and I walked through a second air shower and stepped into the clean room. Ahead of us stretched a wide central corridor that ran down the middle of the factory, which was the size of a football field. People in bunny suits were ducking through the automatic sliding glass doors that led into the different manufacturing areas—diffusion, photolithography, etch, and films. Above us, the automatic wafer transport system carried boats of wafers on tracks suspended from the ceiling—it looked like a model railroad, but it was nearly silent, because the cars were floating just above the tracks on magnets to avoid creating flakes of metal or rubber that might contaminate the fab. People at Motorola’s other factories call MOS 11 “the Country Club” because of such advanced features, although the level of automation also means there are more machines to go haywire. One time, operators in the photo area heard a colossal crash and discovered that the transport system was busily knocking whole batches of wafers onto the floor. They danced around below, trying to catch the wafers before they smashed to bits, until somebody shut the system down. A completed wafer is worth from $1,000 to $10,000, and watching the valuable merchandise being destroyed horrified the onlookers. “Working in this place is like working in a diamond mine,” said an employee who had been at the scene. “The wafers are like huge, extremely breakable diamonds.”
We headed for the diffusion area, where Willis used to work as an operator. This is where bare silicon wafers enter the manufacturing process, and where the first steps in building chips take place. All the chips that MOS 11 makes—there are about fifty different kinds—are built on wafers that consist mostly of pure silicon in a crystallized form. Crystallized silicon does not conduct electricity well because its molecules are hooked together in a lattice, preventing the electrons from moving around. However, most of the wafers have been doped by the companies that supply them to Motorola so that when they arrive, they contain traces of elements like boron or phosphorus, which allows that part of the wafer to conduct electricity very well. Electronic circuits are constructed from millions of tiny devices that function like switches, alternately allowing or obstructing the flow of electricity, and silicon’s nature as a semiconductor—one of the rare elements that can either block or permit the flow of electricity—makes it an ideal foundation on which to build circuits. Building circuits on silicon is like carving a pattern into a woodblock, except that chemicals are used to do the work, instead of mechanical tools. First a layer of material, such as glass or metal, is deposited across the surface of the entire wafer, then a pattern of circuitry is photographed onto the material, and finally either acid or plasma is used to eat away the glass or metal that isn’t necessary. The material that is left behind becomes the microscopic parts of components such as transistors, diodes, and capacitors. The process is repeated over and over again with layers of different types of materials—it takes from forty to eighty days to build a complete chip—until the circuits are finished.
None of the seventeen workers in the diffusion area were touching wafers with their hands, because scratching a wafer ruins it. Before any circuitry was built, the wafers were cleaned in a series of heavy-duty plastic sinks called a hood. A robotic arm dunked the wafers into the sinks, which held corrosive substances such as sulfuric acid, hydrogen peroxide, ammonium hydroxide, and most dangerous of all, hydrofluoric acid. “That’s nasty stuff,” Willis said. “If it gets on you, you don’t feel it until it starts eating your bones away.”
Motorola’s track record in handling toxic chemicals is one of the best in the industry, but spills are inevitable. One day shortly before my visit, alarms sounded throughout the factory, and everybody was ordered out of the building. One hundred thirty employees from the factory’s emergency response teams fanned out to search for the problem. On the factory’s second floor, they discovered several pools of hydrofluoric acid. Because of an unusual series of events, the factory’s drainage system had reversed itself, and the acid had flowed backward into the factory from waste tanks outside. Nobody was injured and the spill was contained, but the accident sent a jolt of anxiety through the factory and caused production to stop for a full eight hours. A week later, supervisors were still encouraging operators to hustle to make up for the lost time.
After the wafers were cleaned, they were baked in furnaces set into the walls of the diffusion area. The furnaces looked like large microwave ovens, but they cooked the wafers at temperatures ranging from 600 to 1,200 degrees Celsius. While the wafers baked, gases were fed into the ovens, causing layers of new material to form on the wafers as the gases reacted with their surfaces. The bare wafers had looked like dark mirrors, but when they came out of the furnaces, they were magenta, turquoise, and yellow. When they start out in the diffusion area, most wafers begin with what is called an oxide layer, as oxygen is piped into the furnaces to form an extremely thin sheet of silicon dioxide—otherwise known as glass. Glass is a good insulator; among other things, it is used to make transistors, one of the primary building blocks of the chip’s circuitry.
At every step along the way—when wafers were put into the hood, and again when they were put into the furnace—the operators entered data into computer terminals that stood on tables made of thin metal rods (to keep dust from collecting). That way, if anything went wrong, engineers would be able to retrace a lot’s history, or if a customer needed to know when an order would be finished, managers could track down where it was in the process. The computers functioned as a two-way communication system: Operators could also check charts to see how much scrap was being produced or whether any bottlenecks were forming in the flow of traffic. In most factories only senior managers would have access to such information, but Motorola’s executives thought employees would work harder if they knew how their contribution fit into the scheme of things. Though managers encourage friendly rivalry among the factory’s divisions, over the past year everyone at MOS 11 has been trying to meet the needs of the people in other parts of the factory who receive their wafers, as well as their own supervisors, so that the entire institution can function more smoothly and produce chips as quickly as possible. “The better my numbers are at the end of the shift, the better I look, right?” said Jesse Barrera, a supervisor in the etch area. “Well, yes, but does the whole factory benefit? Probably not. I’m likely to be flooding the next area with a bunch of work that they can’t even use.”
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