Plastic superconductor could revolutionize cleanrooms
04/01/2001
Mark A. DeSorbo
MURRAY HILL, NJ—Scientists at Bell Labs have developed a plastic that can conduct electricity at low temperatures without any resistance, making it a superconductor and perhaps the catalyst that could revolutionize cleanroom efficiency and change the face of chipmaking.
According to Saswato Das, a spokeman for Bell Labs, the research and development arm of Lucent Technologies, the superconductor's key component, polythiophene, has been used to make optoelectronic devices and may someday be used in future applications such as quantum computing and superconducting electronics.
 Scientists Christian Kloc, Zhenan Bao and Ananth Dodabalapur were three key researchers on a Bell Labs team that produced a plastic superconducting material. |
The breakthrough comes after a 20-year quest to find organic polymers that act as superconductors. Organic polymers are chemical molecules that contain strands of carbon atoms and make versatile plastics. Conductive organic polymers have been around since the 1970s. In fact, last year's Nobel Prize for Chemistry went to the researchers who discovered plastic conductors—organic materials that have some resistance to the flow of electricity.
Creating a superconducting organic polymer, however, proved to be far more difficult.
Das says scientists studied the molecular structure of polythiophene and subjected it to sub-frigid temperatures to give it superconducting qualities. He explained that scientists plan to study the inter-relationships between semiconductors, superconductors and molecular electronics with materials such as polythiophene in the coming months. Das says scientists also believe polythiophene, which can also be a conductor at room temperatures, may be the first of many superconducting plastics.
A crystal, polymer ball?
So what does this mean for the chip industry?
Das says Bells Labs does not want to speculate if its superconductor could be the platform for new and improved wafers.
"So far, Moore's Law has been working," Das says. "We do long-term research and many are pushing for what's going to be important tomorrow. This is a scientific advance and any future applications are still very speculative at this point."
But others close to the semiconductor industry see the Bell Labs discovery as the shape of things to come.
"Organic polymers will play a significant role in computing and related technologies, from data storage to fiber optics to flat panel display and semiconductors. These technologies are no longer isolated from each other," says Stanley Meyers, president of Semiconductor Equipment and Materials International (SEMI; San Francisco). "Organics will play a major role, and they will effect the industry in the future."
Industry observers share that sentiment.
"Silicon will not last forever," says Pieter "Pete" Burggraaf, senior technical editor for Solid State Technology, the international magazine for semiconductor manufacturing. "This is a good indication of some potential solutions out there that are real viable, and this is a snap shot of a larger area of development in which we will find a replacement for silicon in microelectronics applications," he adds.
Dr. Ken Goldstein, of Cleanroom Consultants Inc. (Scottsdale, AZ), says this discovery is potentially revolutionary.
For one, he says, the superconductor could make electricity significantly cheaper, especially if the technology can be used to make smaller transformers and if it has the same capabilities as copper cable and wire.
And that potential is one that Bell Labs does acknowledge. "Because they offer no resistance, superconductors do no waste any power," Das says.
And if that's the case, cleanrooms may operate at an efficiency that facilities directors have only dreamed of, Goldstein says.
"Fan motors could change drastically on the re-circulation and make-up air sides, meaning less power consumption, and lower power consumption would mean better space utilization because rooms for electrical equipment could be smaller or done away with," he adds.
In addition, he explains that fewer electrical components, like fans, mean less electrical and mechanical heat will be generated in the cleanroom, which also means fewer chillers and pumps.
"It could also speed up the construction process, and eliminate some long lead times. Overall, it would somewhat simplify the process," Goldstein says. "This won't happen in the next 10 years, but try to imagine the world in the next 20 or 30 years."
How they did it
Das says the multidisciplinary team has backgrounds ranging from experimental low-temperature physics to materials science and organic chemistry. Their challenge in creating a plastic superconductor was overcoming the inherent structural uncertainty of a polymer—similar to strands of cooked spaghetti—which prevented electronic interactions necessary for superconductivity.
Scientists, he says, were able to overcome obstacles by making a solution containing the inexpensive plastic, polythiophene. Scientists then deposited thin films of it onto an underlying layer so that polymer molecules stacked up against one another like uncooked spaghetti.
"Basically, it's thin film deposition. The technical term is solution casting, meaning that a solution was used to make an extremely thin sheet of the plastic. It almost looks like Saran wrap," Das says.
To give it superconducting qualities, researchers put the material in a deep freeze to remove electrons from the polythiophene.
"They use liquid helium cooling, which brought the temperature down to minus 455 degrees Fahrenheit, and low and behold it became a superconductor," Das adds. Although this is extremely cold, scientists are optimistic that they can raise the temperature in the future by altering the molecular structure of the polymer.