Ever get the feeling you've left the oven on? William Warren had that feeling a couple of years ago, and he was right. Someone in his semiconductor research group at Sandia National Laboratories had accidentally kept an experimental capacitor--a type of component in an electric circuit--roasting too long in the lab. When they rescued it, the group decided to run some tests just for the heck of it. When they exposed the capacitor to a positive voltage, its electrical properties were just as they had expected. But when they reversed polarity and exposed the chip to a negative voltage, it behaved rather strangely. What's more, the component continued behaving strangely even after they turned the voltage off. Stranger still, they could undo the change by reversing the voltage once again.
What happened? Apparently, the unorthodox heating had freed protons to move around within the capacitor. The positive voltage nudged these charged particles down to the capacitor's bottom surface, where they acted to change the capacitor's conductivity. They stayed there until a reverse voltage came along and forced them back to the top surface. Nothing quite like this had ever been observed in electrical components made of silicon, but even so, Warren didn't think of it as anything more than a curiosity. Until, that is, he sat down with other researchers at an electronics conference a few weeks later and someone blurted out that the component might be great for nonvolatile memory--computer chips that don't forget everything when the power's turned off.
Most portable electronic devices, such as cellular telephones and digital cameras, already have some nonvolatile memory chips in them, but they are expensive to manufacture and slow compared with conventional memory. Warren's chips, by contrast, are made the same way regular chips are, which means they should be just as cheap to manufacture and just as fast. The researchers made their first batch of transistors in April 1998, but, Warren cautions, they still have a fair amount of refining to do before they are ready to produce commercial-quality working chips crammed with thousands of transistors. "Chips with great electrical properties don't do you much good if they're based on 'bolonium' and 'unobtanium,'" he muses.
Fractal Antenna Systems' Fractal Antenna
Innovator: Nathan Cohen
Nathan Cohen wasn't looking for any breakthroughs back in 1987 when he started folding the makeshift wire antenna for his beloved ham radio. It was just that he didn't want his neighbors to complain about an unsightly antenna stretched out his apartment window.
But how to fold it? Cohen remembered hearing something in a lecture about fractals, those geometric shapes with patterns that repeat over a wide range of scales, as in the edges of leaves and shorelines and elsewhere in nature. But what was it? Fractals, he finally recalled, allow you to stuff a maximum length into a minimum area. So he bent the wire into a pagoda-like fractal pattern that took up one-quarter the space of the straight wire and then grabbed his power meter to check how much the signal had degraded. "I was astounded," he recalls. "Bending a wire almost always reduces the signal, but in this case there was no measurable difference."
Cohen promptly maxed out his credit card putting together a lab in his garage to explore the phenomenon. Apparently the fractal shapes act as capacitors and inductors--electronic components that are usually added to conventional antennas to tune them to specific frequencies. By some poorly understood quirk of their geometry, however, fractal antennas seem to be sensitive to a much broader range of frequencies than conventional ones, even without added components. Cohen, though, didn't linger too long on the theory. By January 1997 he had designed a fractal antenna no bigger than a 35-millimeter slide that picks up the lower frequency signals used by cell phones. Since the antenna is small enough to fit inside a cell phone, it is less prone to breakage than the stubby copper-coil designs used with most wireless phones, and it should also be cheaper to manufacture.
Cohen's firm, Fractal Antenna Systems, is setting up a deal with a manufacturer (Cohen won't say who) to put the antenna in cell phones by 1999. He is also negotiating with an electric power company on a readerless power meter that radios usage figures automatically. And he's at work on a version of the antenna for direct-broadcast tv.
Metal of Choice
IBM's Copper Chips
Innovator: Randy Isaac
Copper is the ideal material from which to make the microscopic wires that connect transistors in electronic chips. That's because it's a great electrical conductor, meaning little power gets wasted as heat. There are just three little problems: no one could figure out how to get copper into the microscopic holes and grooves where it was needed, how to get it off the spots where it wasn't needed, and how to keep the highly reactive metal from contaminating a chip's silicon substrate. As a result, chips have always employed aluminum wires, even though the metal is an inferior conductor. "The saying in the industry was that copper was the wire of the future--and always would be," says IBM research vice president Randy Isaac.
Isaac can laugh at that sentiment now, because last September, after 15 years of effort, he and his colleagues at ibm finally announced that they had developed a technique for making chips with copper. Not only do the chips work better, but as an entirely unexpected bonus, they're actually cheaper to make than aluminum-based chips.
To get the copper on the chip, Isaac's team ignored the conventional method of applying the metal in vapor form and instead turned to a liquid copper solution. In the presence of a low voltage, copper ions in the solution are attracted to the holes and gullies on the chip and adhere. To remove copper from other spots, the team sanded it off with a plastic pad and a chemical slurry. Finally, to protect the silicon from the reaction-hungry copper, they put a chemical barrier between the copper and the silicon.
"Most people thought we'd never get all this to work together," says Isaac. But by next year, the first copper chips should be coming off the assembly line, and most observers expect the entire industry to evolve toward the metal.
The Black Box of Chess
IBM's Deep Blue
Innovator: C. J. Tan
The dream of getting a computer to beat a reigning chess grandmaster dates back to the dawn of the computer age. But it wasn't until an IBM team led by C. J. Tan developed a 1.4-ton machine made out of 32 processing engines, called the RS6000SP, that scientists had the computing muscle to pull it off.
The main challenge was to get all those processors to work in harmony. To do it, Tan's group let one processor act as a central clearinghouse, parceling out possible moves to the other processors for evaluation. Each processor looked at potential countermoves and counter-countermoves, consulting a database of games each time for tips. Then the processors compared notes, focused on the most promising moves, and examined these in more detail, looking ahead several more moves. All told, the machine could consider 200 million moves per second. The computer, called Deep Blue, lost its first match to world chess champion Garry Kasparov 3 games to 1 back in 1996. But before the rematch, Tan and his crew improved Deep Blue's ability to evaluate unfamiliar moves and expanded its database. "We worked with a grandmaster to capture his knowledge and embedded it in the program," explains Tan.
The rest, of course, is history: Deep Blue beat Kasparov 2 games to 1 in May 1997 in New York City. Kasparov proposed a marathon 20-game rematch, but Tan has refused. He'd rather concentrate on applying some of the lessons learned from building Deep Blue to other applications--those with huge numbers of variables, such as drug discovery and financial analysis.
University of Michigan's Micromechanical Resonators
Innovator: Clark Nguyen
There are two reasons we don't have wristwatch cell phones and they both have to do with an essential component called a resonator circuit. These electronic gizmos oscillate at exactly the same frequency as the radio waves that carry the conversation, making it possible to pluck them from the myriad signals in the air. First, resonator circuits, which are made of either quartz or wire coils, are bulky. Second, they eat a lot of power, which means you need big batteries.
Clark Nguyen was just an undergraduate at the University of California at Berkeley when he recognized a potential solution: replace the electronic resonators with mechanical versions consisting essentially of a simple vibrating strip of silicon anchored to a supporting structure; from there it would be a simple matter of converting the mechanical vibrations to oscillations in an electric signal. The only hitch was that for a resonator to vibrate at cellular phone frequencies, it would have to be less than two-thousandths of an inch long. Fortunately, researchers were just starting to make microscopic electromechanical devices using techniques similar to those for making electronic chips, and Nguyen quickly joined them. "I liked electronics, but I also liked small mechanical things, and I played guitar, which is a type of mechanical resonator," he says. "All my interests just clicked together."
Nguyen, who is now an electrical engineer at the University of Michigan, finally demonstrated in January 1997 a micromechanical resonator small enough to replace the lower-frequency electronic resonators in cell phones. Since the resonator is carved out of the surface of a silicon chip, it can probably be manufactured alongside the phone's microelectronics. That will pave the way for an entire phone on a chip. First, however, Nguyen will have to shrink the resonators further so they can vibrate at the higher cell phone frequencies, and that should take another few years.