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Researchers applies solar cells directly to silicon chip

Posted: 04 Sep 2013     Print Version  Bookmark and Share

Keywords:sensor modules  Fraunhofer Institute for Microelectronic Circuits and Systems IMS  SOLCHIP  solar cell  silicon chips 

Sensor networks made up of individual sensor modules that communicate wirelessly with one another have the capacity to measure local parameters over large areas, and then to pass these data on among sensor modules to a central station. This makes sensor networks suitable for a wide range of applications. The issue of how to power the individual sensor modules remains a sticking point in these sorts of applications.

Researchers from the Fraunhofer Institute for Microelectronic Circuits and Systems IMS have developed an ingenious alternative based on SOLCHIP Ltd IP. The resource they have harnessed to provide power is one that is freely available in almost any location: sunlight.

"We use special process steps to place a mini solar cell straight on sensor modules' silicon chips," said Andreas Goehlich, who heads up the project for Fraunhofer IMS.

"This might sound easy at first, but it actually isn't. For one thing, the Application Specific Integrated Circuits (ASICs) on the silicon chip cannot be disturbed in any way by later steps in the process. ASICs could be termed the brain of the sensor module, facilitating its specific functions. They are manufactured on a piece of silicon in the course of several processing steps, including ion implantation, oxidisation or metal deposition. The structures of ASICs are extremely sensitive, which makes subsequent processing extremely tricky."

"That's why we use a specially developed 'soft' processing technology that has already proved itself on a variety of different ASICs," he added.

In opting for mini solar cells, the researchers are turning to "energy harvesting" method that is becoming more and more established in the low-power sector in particular. This means that the sensor modules are their own mini power stations, independent of external sources of electricity.

Potential energy resources include harnessing vibrations or differences in temperature. Goehlich, however, believes that solar cells have a few advantages over these solutions: "Light is almost always available over long periods of time. What's more, it is not subject to such great fluctuations in supply as other resources." Then there is the advantage that solar energy can be converted into electricity relatively easily.

Development work is currently focusing primarily on agricultural applications.

The technology is ready to be implemented and SOLCHIP Ltd is now taking care of marketing its first product.

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