As submicron precision becomes the industry bellwether, the American Society for Precision Engineering has become the premier venue for announcing developments in interferometry. Last week, at ASPE's Summer Topical Meeting on Precision Interferometric Metrology in Middletown, Conn., breakthroughs in submicron measurements were announced for semiconductor wafers, flat-panel displays, photolithography, automotive systems and other challenging environments. Interferometry is the science of combining two or more waveforms to create a higher-resolution measurement. An interferometer makes use of the principle that when two waves of the same phase coincide they amplify each other, while two waves with opposite phases will cancel each other out. At the conference, the National Institute of Standards and Technology (NIST) demonstrated an infrared-laser technique that it claims more precisely measures the thickness of 300-mm silicon wafers. The technique uses color infrared interferometry to produce a spatial map that represents variations in wafer thickness as different colors. Green represents the ideal thickness; red, orange and yellow show areas that are overly thick; and turquoise and blue shows areas that are too thin. NIST plans to offer a calibration service based on its infrared laser interferometry for the master wafers that the industry uses to calibrate wafer thickness.
Monday, July 25, 2005
When the U.S. military stormed Fallujah, it relied on a range of aerial surveillance sources � high-orbit geosynchronous satellites deployed 20,000 miles over Iraq, low-Earth-orbit probes that scanned the horizon from just 20 miles up, unmanned Predator drone aircraft surveying the ground below from an altitude of 65,000 feet. None of those eyes in the sky, however, was cheap enough to be considered disposable, nor could any hover in the "no-man's land" above aircraft but below satellites. Now Johns Hopkins University has developed a blimp that it claims will achieve both aims. "What we can do is what a satellite cannot do � provide persistent intelligence, surveillance and reconnaissance from no-man's land" at a relatively low cost, said Vincent Neradka, an engineer at Johns Hopkins' Applied Physics Laboratory in Baltimore. No-man's land isn't just an expression in this context: It's the gap between the 65,000-foot ceiling of commercial aircraft and the 100,000-foot (20-mile) minimal distance required for low-Earth-orbit satellites. Nor is Johns Hopkins the only organization targeting that void: Unmanned military blimps from the U.S. Air Force Space Command and Lockheed Martin are close to deployment.
Monday, July 18, 2005
As major semiconductor fabs tackle the submicron nanoscale patterning of wafers, researchers at Pennsylvania State University have already moved to the angstrom scale. Their organic monolayers with 5-angstrom features promise to enable the self-assembly of patterns too small for lithography by serving as templates for chip atoms. "We use molecules that are deliberately designed to be less stable in their substrate attachment than other related molecules, so they would be unlikely to be used directly," professor Paul Weiss said. "Rather, they will be used to shore up patterns and to stabilize the precision of the patterns at this subnanometer scale." Self-assembled monolayers (SAMs) offer a way to create intricate angstrom-scale patterns that can be tuned by adjusting their chemical makeup and thereby precisely adjusting their resulting physical properties. Using these patterns, which serve as placeholders, single-molecule devices can potentially be arrayed across wafers. The SAMs consist of adamantanethiol, a commonly used organic molecule for this kind of work. Weiss' group is developing a catalog of useful chemical formulas that can create a variety of self-assembled monolayers that serve as patterns for single-molecule semiconductor devices.
While nanotechnology promises devices with extremely high speed and simplified architectures, physical problems that make the structures unreliable and difficult to manufacture must be tackled. Recent developments in fabricating semiconducting nanowires and nanocrystals may move the industry closer to realizing new generations of ultrasensitive, high-frequency, high-density devices. Northwestern University researchers have hit upon a reliable and efficient method for forming 5-nanometer gaps in nanowires that could be used to establish electrical contact to nanoscale devices such as nanocrystals and molecular transistors. Experimental physicists at Northwestern University, meanwhile, have applied theory developed at the Naval Research Laboratory to demonstrate a technique for doping nanocrystals. And work on ballistic electron devices at the University of Manchester has paid off with a nanowire-based diode that can operate at frequencies as high as 110 GHz.
An environmental engineer has found a way not only to cleanse contaminated wastewater with its own bacteria but to generate electricity from the funky flow. Lars Angenent, an assistant professor of chemical engineering at Washington University (St. Louis), has already prototyped his findings in a device the size of a thermos bottle � a variation on the hydrogen fuel cell � but he knows it will have to scale up dramatically to fill a commercial role. With scaled-up capacity, Angenent said, a large food-processing plant, which now must cleanse its water at a cost, would be able to turn that processing into a profit center. Industrial-scale wastewater treatment plants, he said, could produce enough electricity to power thousands of households while simultaneously cleansing their water. Angenent's microbial fuel cell design uses the bacteria from wastewater on its anode and cathode instead of platinum, enabling it to make a fuel from the water to create electricity while simultaneously neutralizing the biological matter that would otherwise have to be purged from the water.
Monday, July 11, 2005
As flat-panel liquid-crystal displays made from amorphous silicon grow to gargantuan sizes, Hong Choi, chief technology officer at Kopin Corp., has an alternative display solution. "At Kopin, we believe that mobile video will be really big-you already have television content available on cell phones, and portable media players can store three movies in a single gigabyte," Choi said. "The only thing that is missing is a way to view a really good, large-sized image without having to carry around a big monitor." Kopin (Taunton, Mass.) offers OEMs tiny single-crystal silicon microdisplays that combine with a magnifying lens to project onto the retina an image that appears to be coming from 20- to 30-inch displays. By eliminating the need to carry a life-sized display, the microdisplays offer mobile users of cell phones and media players the same resolution as large flat panels but in a package small enough to fit into a shirt pocket.
Friday, July 08, 2005
Detecting a bomb in a public space like a bus or a building is technologically doable, according to engineers and researchers working on such devices today. The solutions won't come cheap, and it will be at least a year before devices sensitive enough to prevent disasters like last week's bombings are deployed. But "when terrorists are willing to go to the extremes we have seen, the one thing we have to fight them is technology," said Bonner Denton, a professor at University of Arizona. Denton has invented a capacitive transimpedance amplifier that he claims increases the sensitivity of ion-mobility spectrometers by a thousandfold, thereby enabling 100 percent of passengers to be efficiently screened. Denton collaborated with researchers at Sandia National Laboratories (Albuquerque, N.M.) to develop the device. Sandia is using it in a "microhound" explosives detector that it says will replace bomb-sniffing dogs.
Posted by R. Colin Johnson at 2:00 PM
Monday, July 04, 2005
Sandia National Laboratories has combined ultrawideband (UWB) radio signals with advanced encryption techniques to develop a secure sensor and communications network for the U.S. military. The ultrasecure UWB communication system promises to help the government protect its troops on the battlefield by detecting the position of enemies and by making it much harder for them eavesdrop or jam military communications. "We are making military communications signals extremely difficult to detect, intercept or jam," said Sandia National Laboratories researcher Timothy Cooley, "by utilizing the immense spectrum of UWB to spread the energy of communications signals from sensors over such a wide frequency spectrum that the signal power falls below the noise floor of normal receivers." Cooley added, "By combining UWB with AES [Advanced Encryption Standard], our signals are virtually impossible to crack." Also known as "impulse radio," ultrawideband radio transmissions smear a wide spectrum with short, 100-picosecond pulses that are below the noise floor of conventional radio receivers. Even if enemies were equipped with a special UWB receiver, they would be unlikely to know how to reassemble the disparate data packets of each impulse into a coherent whole. And even if they should manage to reassemble the packets, they would still have to crack the 256-bit AES encryption used by Sandia's special secure military communications version.
Georgia Institute of Technology researchers have developed a chip-cooling process that they hope will replace the bulky, bolt-on metal towers used with microprocessors like the G5. Instead of an entire tower through which water circulates, they have created water-filled wafers that can be integrated on self-cooling pc boards. The boards, which are being fabricated by the Microelectronics Advanced Research Corp. (Marco), will provide the plumbing for flip-chip-mounted ICs. In the streamlined cooling system envisioned by the researchers, water will circulate through the silicon substrates of microprocessors and other system-level chips by virtue of trenches etched on the otherwise unused backside of the wafer. "We have applied for the patents with Marco, and so far we have garnered interest in licensing our technology from over a dozen major semiconductor makers," said Georgia Institute of Technology EE Bing Dang. The researcher co-invented the technique in collaboration with professors Paul Kohl and James Meindl and their research assistants Paul Joseph, Muhannad Bakir and Todd Spencer. Although the technique is still in the prototype stage, the EEs have succeeded in fabricating very deep trenches that are only about 100 microns wide in the backside of wafers. Normally that side remains unused, but the new technique utilizes almost the entire surface area of that side for cooling. Because the water circulates through the silicon chips themselves, which have excellent thermal conductivity, the approach promises to cool chips much more efficiently than the customary metal cooling towers.