Collected Essays (24 page)

And then the wind and the movement of the light remind me that this is real, this is where I live. In the mist a big bird circles on great, fingered wings, and I’m filled with joy at being alive in a world where I can dig into the details, just as I am, without a work station.

Standing there bathed in the real world’s full-body sensory input, the efforts of computer reality seemed fiddling and paltry. The world has been running a massively parallel computation for billions of years, after all; how can we even dream of trying to make our machines catch up?

But we do keep pursuing the impossible dream of computer reality anyway; we keep on trying to digitally kit-bash the cosmic matte. It’s one of the human race’s ways of blooming—like science or like art. And in a funny way, thinking about computer realities gives you a greater appreciation for the real thing you get to walk around in.

Note on “Use Your Illusion: Kit-Bashing the Cosmic Matte”

Written in 1993.

Published in
Wired
, Sept/Oct, 1993.

In 1993, I managed to connect with the then rather new
Wired
magazine in San Francisco. They basically took over the market niche for high-tech weirdness that
Mondo 2000
had carved out. The
Wired
mix replaced psychedelia with entrepreneurism, and they were a zillion times more profitable.

I seem to recall that my initial contact at
Wired
was the writer Kevin Kelly, who I’d met at the first conference on Artificial Life.
Wired
gave me three really great journalism gigs, and the first of these was to meet the wizards at ILM.

Robot Obstetric Wards

I fell in love with the Silicon Valley word “fab” the first time I heard it. This short, moderne word means “chip fabrication plant.” A manager might, for instance, say “What kind of outs are we getting from the fab?” In the ‘50s and ‘60s, of course, fab was short for “fabulous,” as in the detergent Fab, or as in the lines in “Bob Dylan’s 115
^th
Dream” that go: “I ran right outside and I hopped inside a cab. I went out the other door; this Englishman said fab.” Gear! Kicky!

After exceedingly many phone calls, I managed to get to go inside two fabs in Silicon Valley, one belonging to the chip-giant Intel, and the other to Intel’s small challenger, AMD (Advanced Micro Devices). AMD recently won a court battle with Intel over the right to produce its own “K6” version of the popular 486 processor chips for DOS and
Windows
-based personal computers. AMD is very much a “we try harder” company, and they were the first to let me into their fab—a quarter-billion-dollar building in Sunnyvale called the Submicron Development Center.

A micron is a unit of measurement equal to one millionth of a meter. A typical human hair might be a hundred microns wide. The scale of chips is discussed in terms of the size of the smallest features of the patterns on the chip. Today’s chips use features about half a micron in size, hence they are said to be using
submicron
designs.

AMD’s Submicron Development Center was originally intended to be purely a research facility, but the demand for the AMD 486 chips is such that the facility is now also being used for commercial production. It turns out to be crowded and a bit hellish in the AMD fab, which feels to be about the size of a wide office-building corridor plus maybe six offices on either side.

Something I hadn’t initially realized is that being a fab worker is like being any other kind of assembly-line worker. It’s a rigorous blue-collar job. Most of the workers are Asian or Hispanic. The AMD fab is open twenty-four hours a day, every day of the year except Christmas—and in the Intel fab they work on Christmas too. The workers pull twelve-hour shifts, with three shifts one week and four shifts the next, for an average of forty-one hours a week. Although some of the fab workers are highly paid engineers, starting pay for a simple technician is around $24,000 a year, which comes to something like $12 an hour.

What actually goes on in a fab? A fab buys blank silicon wafers and draws complicated patterns on them. This changes a wafer’s value from $200 to $30,000 or more. It’s almost like printing money. The catch is that each of the many machines used in a fab costs over a million dollars. And buying machines for your fab is kind of complicated, although the Sematech consortium is seeking to make this easier.

When a fab finishes a wafer, the wafer is shipped to another plant where the wafer is sawed up into chips and the chips are put into the familiar plastic cases with wires coming out. These secondary plants are mostly in southeast Asia—the Silicon Valley fabs are solely concerned with printing the chips onto the wafers. To avoid dust, the wafers are shipped in vacuum-sealed bags.

The essence of the environment inside a fab is that this is a place for chips and not for people. People are dirty. Their bodies flake and crumble, sending off showers of dust. One dust particle can ruin a chip, for instance by shorting out the separation between two nearby submicron circuit lines.

In the current prehistoric state of robotics, there is no hope of fully automating a fab, especially given the fact that the process technology is subject to being changed over and over. To deal with having dirty people in there, the fab must be maintained as a clean room.

The cleanliness of a room is specified in terms of the number of particles larger than one micron that can be found in a cubic foot of air. An average non-smoking restaurant might have a few hundred thousand of such particles per cubic foot. In a surgical operating theater, the level is brought down to about twenty thousand. In the outer hallways of a fab building, the level is ten thousand, while in the wafer-handling areas of the fab itself, the level is brought down to one individual particle per cubic foot. How? At AMD the procedure went like this.

My guide is Dan Holiga, a member of the AMD Corporate Training division, responsible for instructing new workers on clean room procedures and for arranging science courses for them at local colleges. Dan leads me into the pregowning room. The floor inside the door is covered with sticky adhesive. I sit down on a bench and put some blue booties over my shoes so as not to track dirt into the locker room. The woman behind the counter can’t find Dan’s special fab badge, so she gives him a Visitor badge like mine. We select building suits in our sizes: two-piece suits like tight-cuffed blue pajamas. The woman gives us each some white plastic shoes like bowling shoes.

In the pregowning room, we stash our street-clothes in the lockers and put on the blue building suits and the white plastic shoes. We wash our hands and put on hair nets and safety glasses. Dan has brought a camera with him. We walk through a corridor into the outer hallway of the fab building. This is the ten-thousand-particles-per-cubic-foot zone, and the air feels cleaner than any I’ve breathed in a long time. My allergies are gone; the odorless air flows smoothly into my lungs.

We pass a break room where some of the fab workers are having non-dusty snacks like apple juice and yogurt. Then we go into a second locker room. I’d thought we were already dressed for the fab, but that was just the start. The second locker room is the gowning room proper.

Rudy in the chip fab gowning room. (Photo by Dan Holiga.)

Here we put on latex gloves. Then we wipe off our safety glasses and our Visitor badges and Dan’s camera—wipe everything three times with lint-free alcohol-soaked cloths. We put on white hoods and “bunny suit” overalls made of Fibrotek, which is a sandwich of nylon and Teflon. We pull “fab booties” over our shoes and we put on face masks. We pull vinyl gloves over our latex gloves. This is starting to feel a teensy bit…obsessive. I’m reminded of the “environmentally ill” people you see in Berkeley natural food stores, shopping while wearing gas-masks and elbow-length gloves. They’d love it here in the gowning room. But, I remind myself, this isn’t about obsession here, this is about objective scientific fact: getting down to one micron-sized particle of dirt per cubic foot of air!

Now Dan leads me through the air shower: a corridor lined with air-nozzles blasting away. We hold up our hands and turn around, letting the air wash us all over. The invisible particles fall to the floor, where they are sucked away. In the air shower and in the fab, the floors are coarse grates, and the ceilings are filled with fans. There is a constant flow of air from above to below, with any showers of filthy human particles being sucked out through the floor grates. The air in a fab is completely changed ten times a minute.

I step out of the air shower and, fully purified, I step into the fab. As the Bible says, “I was glad when they said unto me, let us go into the house of the Lord.” I am in the heart of the temple to the God-machine of Silicon Valley. The lights are yellow to avoid clouding the photo-resist emulsions; this gives the fab a strange, underworld feeling. The rushing air streams down past me from ceiling to floor. Other white-garbed figures move about down the corridor; all of us are dressed exactly the same.

On the sides of the corridor are metal racks holding boxes or “boats” of wafers waiting for the next stage of their processing. The racks have wires instead of shelves—there are in fact no flat horizontal surfaces at all in a fab, as such surfaces collect dust and interfere with the air flow.

The only hint of human contamination is the meaty smell of my breath, bounced back to me by the white fabric face mask I’m wearing. I wish I could tear off the mask and breathe the clean pure air of the chips. But then I would exhale, and the wafers wouldn’t like that—detectors would notice the increased number of particles-per-cubic-foot, and lights would flash.

The layout of a fab is a single main corridor with bays on either side. To keep the bays clean and uncluttered, most of their machines are set so that the faces of the machines are flush to the bay walls, with the bodies of the machines sticking out into sealed-off corridors called chases. Like people, machines have bodies whose exigencies are not fully tidy. The chases are clean only to a ten particles per cubic foot level, as opposed to the bays and the main fab corridor, which are kept at the one particle level.

As we move down the main corridor to start our tour, people recognize Dan and come over to pat him on the back or on the arm. Dan theorizes that in the clean room, people can’t see each other’s faces, so they tend to fill in non-verbal communication by touching each other. Another factor could be that, given that everyone is clean, there is no fear of getting yourself dirty through human contact. Or maybe it’s just that you have less inhibitions towards someone who is dressed exactly like you. In any case, the fab workers seems to have a strong team spirit and sense of camaraderie. They’re like happy termites in a colony.

The craft of getting a hundred 486 or Pentium chips onto a silicon wafer involves laying down about twenty layers of information. It’s a little like printing a silk-screen reproduction with twenty different colors of ink. At each step a fresh layer of silicon dioxide is baked on, parts of the new layer are etched away, and metals or trace elements are added to the exposed areas.

As well as having to be positioned to an accuracy of a tenth of a micron or better, the successive layers need to have a very specific thickness. Rather than being measured in microns, the thickness of the layers are best measured in
nanometers
, or billionths of a meter. Each layer is about ten nanometers thick. It’s all about fiddling with little details, to a mind-boggling degree.

The process takes as long as twelve weeks for a completed wafer’s worth of chips. It’s not so much a linear assembly line as it is a loop. Over and over, the wafers are baked, printed, etched and doped. At AMD, workers carry the boats of wafers up and down the corridor; while at Intel’s plant there is a miniature overhead monorail on which the boats move about automatically, like gondolas in a scale model of an amusement park ride.

At AMD, I visit the etching bay first. There are a series of sinks filled with different kinds of acid piped up from tanks located on the story below the fab. In the bad old days, you could recognize fab workers by the scars on their neck from splashes of acid, but now they have a small industrial robot arm to dip the chips. I’m happy to see the arm; this is confirms my science fictional notion that fabs will ultimately be places where robots reproduce themselves: robot obstetric wards.

The acid baths are for removing the photo-resist masks after the etching itself is done. The etching is typically done “dry”—that is, a fine dust of ions is whipped into a frenzy with powerful radio frequency signals to make a submicron sandblaster. The idea is to dig out parts of the chip so that metal conductors and metal-doped semiconductors can be patterned in to make up the wires and transistors of the integrated circuit which the chip is to become.

The real heart of a fab is the photolithography bay. Here the gel called photo-resist is sprayed onto the wafers, and then the wafers go into a stepper, which is the machine that projects the circuit diagrams onto the wafer’s chips.