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Ironing Out A Vexing Chipmaking Problem


Developments to Watch

IRONING OUT A VEXING CHIPMAKING PROBLEM

WHEN SEMICONDUCTOR MAKERS WANT TO COMBINE TWO MATERIALS TO PRODUCE SOMETHING that can't be made from a single material, such as ultraviolet light-emitting diodes (LEDs), they have a limited menu of choices. That's because of the so-called lattice mismatch--the difference in spacing between the atoms in various chip materials. Even tiny, 1% mismatches rapidly multiply into strains that result in material flaws--and defective LEDs. For many combinations, the mismatch factor climbs to 20% or more.

Now, researchers at Cornell University seem to have found a way to do the impossible. And it's so simple that materials scientists are dumbfounded. "Even we don't understand why it works so well," admits Felix E. Ejeckam, a Ph.D. student whose computer simulations indicated that the "too-easy" idea from Yu-Hwa Lo, a Cornell associate professor of electrical engineering, just might work.

It boils down to this: Take a very thin film of gallium arsenide and place it on a gallium arsenide wafer. Rotate the film about 10 degrees out of lattice alignment, then iron it down with heat and pressure. Now, a badly mismatched material can be grown atop this buffer layer, and lattice-mismatch strains are somehow passed through the buffer into the bulk substrate, where they cause no harm. Chipmakers are excited by the technique because it also promises a new silicon foundation for computer chips.EDITED BY OTIS PORTReturn to top

FROM THE FOLKS WHO BROUGHT YOU DOLLY

WHAT HAPPENS WHEN YOU cross a rabbit and a salmon? If all goes well at the U.S. laboratories of PPL Therapeutics PLC--the Scottish biotech company that helped create Dolly, the cloned sheep--the answer will be a boundless supply of a valuable osteoporosis drug.

PPL researchers, fresh from their success with Dolly, have just taken the wraps off Babe, a rabbit whose chromosomes bear a transplanted salmon gene that codes for the protein calcitonin. This protein is widely used to reduce the crippling bone loss that afflicts roughly one-third of all women in their 70s. Sales of just one such product, Novartis' calcitonin nose spray, topped $200 million last year.

Researchers at PPL Inc.'s lab in Blacksburg, Va., led by general manager Julian Cooper, selected a salmon gene because it had already been identified and studied. Just 28 weeks after the gene transfer, calcitonin was detected in Babe's milk in relatively high concentrations. And unlike most proteins produced in so-called transgenic animals, which require extensive processing before they can be administered, Babe's calcitonin occurs in a form that's effective for humans.By Neil Gross EDITED BY OTIS PORTReturn to top

FOR THE APPIAN WAY, HIT COMMAND-A

ROME WASN'T BUILT IN A DAY. Reconstructing it in virtual reality is no snap, either. The ambitious Rome Re-born project at the University of California at Los Angeles plans to make a multilayer virtual reality Rome that spans the centuries from 850 B.C. to 450 A.D. Archaeologists, architects, historians, and other researchers will be able to click on a spot and peel the virtual reality "onion" to step back in time.

The project won't be completed until about 2020. But Imperial Rome of 450 A.D. will spring to life again in time for the Eternal City's celebration of the new millennium. In multimedia kiosks around the city, people will be able to prowl the Colosseum's dungeons, stroll through the Roman Forum, and listen to toga-clad actors. This first model will be sold on CD-ROMs to help defray the project's cost--as much as $20 million.

Rome Reborn was started in 1995 by a multidisciplinary group of UCLA professors. When they learned of similar efforts at Infobyte, an Italian multimedia company, the groups joined forces. Infobyte expects to finish its model of the Colosseum within weeks. UCLA plans to unveil its reconstruction of the Trajan Forum at the opening of the new Getty Museum in Los Angeles late this year.By Monica Larner EDITED BY OTIS PORTReturn to top


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