July 2, 2004 12:12 PM PDT

Start-up develops tiny hot plate that burns like Venus

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Boston MicroSystems has developed a chip that is thinner than a human hair but can quickly go from zero to 1,100 degrees Celsius, an invention that scientists may someday use to study chemical reactions in action.

The company's micro hot plates--which measure on average 100 microns by 100 microns--can reach higher temperatures much faster than existing tiny heating units, but are also more robust and less prone to failure, according to Rick Mlcak, president co-founder of the company.

The unit takes only about 1 one-thousandth of a second to hit peak temperature of 1,100 degrees Celsius, or 2,012 degrees Fahrenheit. That's about the same temperature as the surface of Venus. The rapid climb in temperature, in part, comes from the small size of the unit, the materials involved and the design of the plate.

As a result, researchers may be able to use this to study chemical interactions that now prove difficult to produce. Semiconductor designers, for instance, currently layer chemicals onto wafers by heating a wafer in a chamber to several hundred degrees Celsius, dispersing a metallic vapor, and then cooling the chamber to let the metal adhere. The heating and cooling process can be time consuming.

With Boston MicroSystems' hot plates, a section of a wafer can be more rapidly heated and cooled, so a researcher can perform and study more interactions. Similarly, a scientist with a precision microscope can scrutinize materials while heating them.

What sets the company's technology apart is that it is a chip sculpted out of a single sliver of silicon carbide. The heating coils, tiny channels, are carved out of the center of the chip through lithographic processes. These sit just below the surface of the chip, much as a barbeque unit is recessed in tables in Japanese barbeque restaurants. The heating area is suspended by four tethers that are also part of the original wafer.

"The top of the hot plate itself is the original wafer," said Mlcak.

Silicon carbide is stable at high temperatures, but also impervious to chemical attack from most materials. As an added benefit, the hot plates can be cleaned by merely burning debris off the surface.

Other micro hot plates are assembled from different parts. That, however, can limit the upper temperature range. If any of the parts are metal, there is risk that it will react with silicon in the micro hot plate.

Additionally, "each layer will have different thermal coefficients of expansion," he said.

Boston MicroSystems has made hot-plate chips ranging from 43 microns on a side to 128 microns on a side, although on average they are 100 microns by 100 microns. A micron is a millionth of a meter--by comparison, a human hair is about 150 microns thick. While small in human terms, microns are huge when it comes to chips. Most processor components today are measured in nanometers, or billionths of meters.

The six-employee Boston MicroSystems has created a heating unit that contains four of the hot plates in a two-by-two array.

The hot plates are an example of a microelectromechanical system, or MEMS, or chips that function like machines. Other companies are working on miniature pumps, or chips that can perform blood tests and lab work.

Boston MicroSystems was founded by Mlcak and Harry Tuller, an MIT professor. The product was developed with support from the National Science Foundation, the Department of Energy, the Environmental Protection Agency, and NASA.

 

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