Stanford method could reduce GaAs bill
Researchers at Stanford University in the US have invented a manufacturing process that they think could reduce the cost of making GaAs electronic devices and open up new uses for them.
It can cost about $5,000 to make a wafer of GaAs 8 inches in diameter, versus $5 for a silicon wafer, according to Aneesh Nainani, who teaches semiconductor manufacturing at Stanford
To do this the Stanford process would add several steps to the manufacturing process, which the researchers have demonstrated in the lab.
First they covered the wafer with a layer of disposable material. Then they used standard processes of gas deposition to form a GaAs circuit layer on top of the disposable layer. Next, using a laser, they vapourised the disposable layer and lifted off the circuitry layer like flapjack on a greased griddle.
They mounted this thin circuitry layer on a more solid backing and cleaned the costly GaAs wafer to make the next batch of circuits.
Nainani estimates that this reuse could create GaAs devices that would be 50 to 100 times more expensive than silicon circuits - still a big differential but much less than what exists today.
It all boils down to economies of scale, said Bruce Clemens, the professor of materials science and engineering who led this work. "Once it becomes possible to make GaAs more cost-effectively, other people will jump in to improve other parts of the process," Clemens said. "And with each advance, more uses will open up, especially in solar energy generation where GaAs has clear efficiency advantages."
