Fraunhofer researchers develop process for compact microchips that operate at up to 300 ˚C
06 May 2014
Scientists of the Fraunhofer Institute for Microelectronic Circuits and Systems IMS have developed a new type of high-temperature process that can fabricate extremely compact microchips that operates at temperatures of up to 300 ˚C (572 ˚F). The chips could have down-hole applications in drilling for oil and gas or geothermal resources.
Conventional semiconductor chips (CMOS) sometimes tolerate temperatures of up to 250 ˚C (482 ˚F), but their performance and reliability fall off rapidly. Frequently, companies must test a large quantity of standard chips using the trial-and-error method before they obtain an acceptable selection—a laborious undertaking.
Continuously cooling the heat-sensitive microelectronics, is another option, but requires extensive additional effort. There are also specialized high-temperature chips on the market, but with about one micrometer minimal structure size, they are very large.
The solutions available are always associated with certain trade-offs: either they have comparatively large components, or they function with limited performance.—Holger Kappert, head of High-Temperature Electronics at Fraunhofer IMS
The microchips from IMS are different, though. At a characteristic dimension of 0.35 µm, they are considerably smaller than the high-temperature chips available today. The advantage of these kinds of complex microstructures can be summarized as “more functionality at less size”.
To fabricate the heat-tolerant mini-chips, the researchers in Duisburg, Germany, use a specialized high-temperature silicon-on-insulator (SOI) CMOS process that introduces a layer that insulates the transistors from one another. This insulation prevents leakage currents that occur from influencing the operation of the chip. Leakage currents are electrical currents flowing over other than intended paths. They are caused or increased by elevated temperatures in particular. The researchers also use tungsten metallization for their chips, which is less temperature-sensitive than the aluminum usually used. This increases the operating life of the high-temperature chips.
Production of geothermal energy, natural gas, or oil is not the sole area of potential application. The microchips could also prove valuable to aviation, for instance by enabling sensors to be located as close as possible to turbine engines in order to be able to observe the state of their operation. This could permit the turbines to be operated more reliably and efficiently, saving jet fuel and thereby making aviation environmentally friendlier. The first field tests of the new chips have been positive. The researchers want to offer the fabrication process as a service later this year.
If the price can be brought down far enough, these chips will be attractive for automotive use as well. Temperature control has always been an issue for sensors and actuators, and if they can be run in engine coolant or oil or heat-soaked in the hottest under-hood air and still work, the system costs related to engineered low-temperature heat sinks can be eliminated.
Posted by: Engineer-Poet | 06 May 2014 at 09:04 AM