German scientists have successfully fabricated compact microchips able to tolerate temperatures up to 300°C in an achievement that could have significant implications for the geothermal and oil production industries.
Drill bits and borehole probes employed in the geothermal industry are fitted with a range of sensors and control mechanisms in order to record and analyze environmental parameters at various depths. This information is used to determine suitable—warm—regions for geothermal production. However, say researchers at the Fraunhofer Institute for Microelectronic Circuits and Systems (IMS), these devices hit their thermal limits when exposed to temperatures over 200°C, rendering them unable to function close to the Earth’s core, where temperatures range from 150°C to over 200°C, or in the Earth’s core, where temperatures of up to 7,000°C are thought to be present.
Now, a new type of high-temperature fabrication process developed by the Fraunhofer IMS team could enable the geothermal, natural gas and oil industries to access resources closer to the Earth’s core.
“It becomes possible with this process to fabricate extremely compact microchips that operate flawlessly even at temperatures of up to 300 degrees Celsius,” Holger Kappert, head of High-Temperature Electronics at Fraunhofer IMS, said.
Measuring just 0.35 µm, the microchips are created using a specialized high-temperature SOI CMOS process. “SOI stands for ‘silicon-on-insulator’ – that means we introduce a layer that insulates the transistors from one another,” Kappert explained, adding that the insulation prevents leakage currents—electrical currents flowing over other-than-intended paths—from hindering chip operation. Furthermore, the chips were made using tungsten metallization, which is less temperature-sensitive than traditional aluminum.
In addition to geothermal energy, natural gas and oil production applications, the Fraunhofer IMS team also sees potential uses in the aviation industry, such as in sensors located close to hot turbine engines.
Field testing of the new chips thus far has reportedly yielded positive results, and the researchers hope to offer the fabrication process as a service later this year.
