Project works on silicon carbide ICs for high temperatures

Scientists at Raytheon’s Glenrothes facility are working on a project to demonstrate integrated circuits made from silicon carbide that operate at temperatures above 300°C.

Ewan Ramsay, a principal engineer at Raytheon, told The Engineer: ‘The technology can be used to implement analogue and digital functions where the operating temperature can go above 300°C.

‘The technology is currently at the demonstrator phase and our project is focusing on two main demonstrators,’ said Ramsay. ‘The first is a standardised sensor interface circuit and the second is a demonstration of a gate drive for high-temperature power switches.’

Raytheon is hoping to combine its complementary metal oxide semiconductor (CMOS) experience with recent silicon carbide process experience into a unique capability.

Jen Cormack, Raytheon’s silicon carbide manager, said: ‘We believe that by manufacturing integrated circuits on thin wafers of silicon carbide, the temperature at which integrated circuits can operate will be increased by more than 200°C.’

Previously, integrated circuits designed to withstand high temperatures were made out of silicon, which could only operate up to temperatures of 125°C.

Ramsay added: ‘In aerospace there is a pressing need to improve the fuel efficiency of commercial airliners. One way to do this is to reduce the weight of the aircraft by decreasing the amount of wiring around the gas turbine.

‘High-temperature CMOS can be used to decrease the amount of wiring by allowing electronics to be closer to the high-temperature sensors.

‘By having electronics closer to the gas turbine engine combustion chambers more accurate sensing can be done, increasing the overall efficiency of the unit,’ he said. 

The technology could also have applications in the power converter industry, which is growing due to the increase in renewable energy sources.

Ramsay said: ‘A new technology is emerging where the power converter switches are implemented using silicon carbide, which allows better efficiency. High-temperature CMOS technology can be used to drive and protect these components.’

According to Raytheon, the application of silicon carbide in these industries enables more efficient use of energy resources through reducing weight, and reducing electrical energy losses.

The biggest challenge facing the scientists is the lack of a support infrastructure because high-temperature CMOS is a relatively new technology.

For certain applications, silicon carbide wafers can cost up to £900 each in comparison with silicon wafers, which are less expensive. However, Raytheon believes the price for silicon carbide wafers will decrease dramatically when the demand rises. 

Raytheon is collaborating with Strathclyde University for the project dubbed HiTSiC (High Temperature Silicon Carbide) and is being funded by the EPSRC and the TSB’s Materials for Energy programme.