November 29, 1999
UPTON, NY-For years, scientists and engineers have dreamed about building machines smaller than the diameter of a human hair to perform microscopic tasks. But the techniques used to make these micro-machines have been expensive and time-consuming. Now, scientists at the U.S. Department of Energy's Brookhaven National Laboratory and Standard MEMS Inc., which has a manufacturing facility in Hauppauge, N.Y., are collaborating on a revolutionary micro-fabrication technique that promises to be more economical than present approaches and likely to produce cost-effective devices.
Micro-fabrication techniques were first developed to manufacture computer chips and other integrated circuits. Patterns for circuits are transferred to silicon wafers using masks and some form of radiation, usually ultraviolet (UV) light, to transfer the pattern from the mask to the wafer - similar to the way an image is formed on film in a camera. This technique, however, is limited primarily to two-dimensional designs and silicon-based compounds as building materials.
Until recently, three-dimensional micro-fabrication (also called high-aspect-ratio micro-fabrication) has required the use of synchrotron X-ray beams and masking materials that can block X-rays. The high cost of an X-ray mask and the small number of synchrotron X-ray sources limit the use of this technique.
Through a Cooperative Research and Development Agreement (CRADA), Brookhaven and Standard MEMS Inc. plan to optimize a process to manufacture three-dimensional microstructures with a specialized UV-sensitive material to achieve results similar to those produced by X-rays. The process could then be easily incorporated into existing manufacturing systems at silicon foundries, like Standard MEMS, which are accustomed to working with UV exposure sources. That will make the work of designing, testing and refining microstructures proceed much more rapidly than is possible with the current technique, says materials scientist John Warren of Brookhaven. "You can do in weeks what would have taken months," he says.
"Brookhaven is doing the initial research to develop the microfabrication technique," says Bill Trimmer, Vice President of Technology at Standard MEMS. "Standard MEMS will then commercialize the process," he adds.
The first step will be to evaluate the mechanical, electrical and thermal properties of the new material to determine what kinds of structures can be made from it and for what purposes. "Once we fully understand the processing parameters of this technology, then many products will undoubtedly be based on it," says Warren.
Some possibilities are sensors for various types of energy, such as ultraviolet and infrared rays, as well as micro-actuators, or mechanical movers that can manipulate things at the micron scale. "We're already using this technology to make more accurate X-ray detectors and we're exploring its applicability for several biomedical applications," Warren says.
To make these devices, designers would use a patterned mask to cover portions of the film-like material and expose it to UV radiation. The UV exposure triggers cross-linking to strengthen the bonds in the exposed areas of the material. When the material is then unmasked and put into a developing solution, the stronger, cross-linked areas remain while the areas that had been masked dissolve. The resulting "photo-etched" 3-D structure can then be used as a scaffold or as a mold for other building materials.
Standard MEMS Inc. is one of the world's largest suppliers of micro-electro-mechanical systems (MEMS), including a device used in inkjet printer cartridges. The company is headquartered in Burlington, Mass., with a MEMS manufacturing facility in Hauppauge, N.Y. More information about Standard MEMS is available at http://www.stdmems.com, or by contacting Diego J. Cisneros, V.P. Marketing & Sales, at (781) 270-4180 or firstname.lastname@example.org.
Brookhaven's participation in this CRADA is funded by the DOE's Office of Science, Laboratory Technology Research Program.
The U.S. Department of Energy's Brookhaven National Laboratory creates and operates major facilities available to university, industrial and government personnel for basic and applied research in the physical, biomedical and environmental sciences, and in selected energy technologies. The Laboratory is operated by Brookhaven Science Associates, a not-for-profit research management company, under contract with the U.S. Department of Energy.