Rice creates two terminal memory chips

Rice University boffins have created the first two-terminal memory chips that use only silicon.

They claim that the discovery will extend the limits of miniaturisation subject to Moore’s Law.

The new technology places multiple layers of memory capacity on the same chip, creating a 3-D memory architecture.

A Rice spokesman said the technology will improve scalability by an order of magnitude compared to current NAND flash technology.

Doing all this in 3D makes it highly scalable and creates memory that’s made out of dirt-cheap material.

It all started in 2008 when boffins worked out that electrical currents could repeatedly break and reconnect 10-nanometre strips of graphite. This potentially boosted flash memory capacity by many times.

The new technology could withstand radiation and temperatures of 200 degrees Celsius that would cause solid-state disk memory to disintegrate.

But professors James Tour, Douglas Natelson and Lin Zhong were not sure why it worked so well. This latest finding proved that the circuit doesn’t need the carbon to function, only silicon.

Jun Yao, a graduate student in Tour’s lab, sandwiched an insulating layer of silicon oxide between semiconducting sheets of polycrystalline silicon that served as the top and bottom electrodes.

When he applied a charge to the electrodes, he created a conductive pathway by stripping oxygen atoms from the silicon oxide, forming a chain of nanometre-sized silicon.

The chain can be broken and reconnected by applying a pulse of varying voltage.

But it is five times denser than 20 nanometre flash without 3D stacking.

Zong thought that the nanowire-based idea was more amenable to vertical stacking, which makes the technology very scalable as process technology improves. The density can be further doubled or tripled with two or three layers.

NAND flash memory is controlled by three terminals or wires but the new silicon memory requires two terminals. This makes it viable for three-dimensional or stacked silicon arrays and multiplying a chip’s capacity. Chips made with silicon consume virtually no power and keep data intact.