Electronic Design

From The Labs

To cope with the increasing challenges of IC design, microelectronic researchers at Rensselaer Polytechnic Institute are building chips upward instead of out. Stacking electronic circuits on top of each other, the researchers say, will cut product costs and improve performance. Side-by-side wafers require comparatively long wires to carry signals between chips. Vertically stacked chips can use shorter wires. Designers make two or more layers of the device on different wafers and then laminate them in pairs. According to researcher John McDonald, "These laminated pairs can then be treated as single wafers with two layers of circuitry on them and further bonded as pairs again. This can result in up to four layers of intimately connected circuits that have extremely short wires for some of the critical paths." For more information, see the March edition of Rensselaer magazine.

By combining two closely packed silicon-wire MOSFETs, Japanese scientists have crafted what is said to be the first silicon-based device to manipulate single units of charge. According to Nature magazine (www.nature.com), the single-charge transfer device can generate, store, and transfer individual holes (positive charge carriers) when operated at a temperature of 25 K. Akira Fuijiwara and Yasuo Takahashi of the NTT Basic Research Laboratories in Atsugi, Japan, point out that their single-charge transfer device is better suited to large-scale integration than previously developed single-electron tunneling devices. In addition, the new silicon component enables a much more precise measurement of current than is otherwise possible.

A newly discovered plant gene could pave the way for new types of plastics produced from plant materials rather than petroleum products. Professor Clint Chapple of Purdue University and Knut Meyer of DuPont and Co. have cloned a gene that enables plants to package and store materials in their cells. Using this discovery, scientists may be able to develop plants that produce a wide array of monomers, the molecular building blocks that make up the polymer chains in plastics. Currently, most polymer chains are derived from petroleum, which limits the number of chains available.

An economical process for recovering neodymium from magnetic scrap material is expected to produce the first large-scale commercial recycling of this valuable rare-earth element. Though it may primarily benefit the magnesium casting industry, this discovery could also potentially reduce the cost of building the neodymium-iron-boron magnets used in many small motors. Researchers at the Department of Energy's Ames Laboratory developed a technique that uses molten magnesium to extract neodymium from the waste materials that are produced when manufacturers machine and handle the brittle neodymium-iron-boron magnets. Though by weight only 29% of the scrap material is neodymium, its $30/kg price tag (nearly as much as silver) is a strong incentive for recovery. Unlike previous recovery methods, which were too complicated and expensive for commercial use, the lab's process is relatively simple.

TAGS: Components
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