Breakthrough chip research brings faster and cheaper semiconductors

RESEARCHERS HAVE UNCOVERED a way to make faster and more efficient chips while saving on manufacturing costs.

The new semiconductor technology was developed by Stanford University, and uses gallium arsenide as opposed to silicon.

It can handle data at higher speeds, or high-frequency radio signals, because the material allows electrons to move through it up to six times faster.

Silicon has traditionally been used as a semiconductor material, despite the technical advantages of gallium arsenide, as it's around 1,000 times cheaper to produce.

As a result, gallium arsenide-based devices are used only in niche applications where its special capabilities justify the higher cost, such as smartphones that make use of high-frequency radio signals which arrive faster than silicon can handle.

However, Stanford's researchers have announced the development of a new manufacturing process that could reduce the cost of gallium arsenide electronic devices and thus open up new uses for the technology.

Pros and cons
Silicon and gallium arsenide are developed from raw crystal and are used in electronic devices in the same way, each material being fashioned into what electronics manufacturers call 'wafers'.

It can cost about $5,000 to make an 8in gallium arsenide wafer, compared with just $5 for a same-sized silicon wafer.

These wafers are flat, circular platters of purified material which can eventually create computer chips, solar cells or other electronic devices.

Stanford University said that the new manufacturing process looks to lessen this 1,000-to-one cost difference by reusing the $5,000 wafer.

"Today the working electronic circuits in a gallium arsenide device are grown on top of this wafer. Manufacturers make this circuitry layer by flowing gaseous gallium arsenide and other materials across the wafer surface," explained the university.

"This material condenses into a thin layer of circuitry atop the wafer. In this scenario, the wafer is only a backing. The thin layer of circuitry on top of this costly platter contains all the electronics."

A new process
To make the wafer reusable the Stanford process adds several steps to the manufacturing process. Firstly, the wafer is covered with a layer of disposable material, then a standard process of gas deposition is used to form a gallium arsenide circuit layer on top of the disposable layer.

Next, a laser is used to vaporise the disposable layer and lift off the circuitry layer "like a flapjack on a greased griddle".

Finally, this thin circuitry layer is mounted on a more solid backing and the costly gallium arsenide wafer is cleaned to make the next batch of circuits.

Aneesh Nainani, who teaches semiconductor manufacturing at Stanford, said that this reuse could create gallium arsenide devices that would be 50 to 100 times more expensive than silicon circuits. That's still a big difference compared with the super-cheap silicon process, but it's much less than the current difference.

Bruce Clemens, Stanford's professor of materials, science and engineering, who led the work, explained that the new process could restore interest in gallium arsenide electronics.

"Silicon is inexpensive today because, over time, the electronics industry has focused all its ingenuity on making silicon cheaper," he said.

"Silicon wafers are $5 today because manufacturers compete to satisfy the world's ever-increasing appetite for silicon wafers and, over the course of decades, that competition has driven prices down."

He added that it all boils down to economies of scale. "Once it becomes possible to make gallium arsenide more cost-effectively, other people will jump in to improve other parts of the process," he said.

"And with each advance, more uses will open up, especially in solar energy generation where gallium arsenide has clear efficiency advantages."

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