The Arrival of Nanotech Memories

By Roland Piquepaille

After the ages of DRAM and SRAM memories, is this time for nanotech memories? ExtremeTech says that "molecular memories" as well as memories based on carbon nanotubes are emerging. With these nanotech memories, several startup companies are envisioning future chips mixing logic, memory and reconfigurable computing elements. One of these promising startups is ZettaCore, which has built a prototype of a molecular memory designed to replace both SRAM and DRAM kinds of memories. These molecules, which are about 1 nanometer in size, are also self-assembling, meaning that they can be manufactured with existing equipment used in the semiconductor industry.

The market targeted by Zettacore and others is huge -- so vast that industry watchers acknowledge that it could all be too good to be true. Initially, however, Zettacore's "molecular memory" is being designed to replace both the nonvolatile SRAM market as well as the much larger, lucrative DRAM market, which market research iSuppli Corp. estimates to be worth $21.2 billion in 2004. Eventually, analysts said, the company will try and make the leap to developing components that could integrate logic, as well.

Here are some details about the technology.

In nature, a class of organic compounds known as porphyrins are found within chlorophyll and hemoglobin, stable molecules which can be "charged up" to transfer energy, said Randolph Levine, president and chief executive of ZettaCore. It just so happens that adding charge is one of the requirements of volatile memory, like DRAM.

Instead of silicon, the Zettacore technology uses individual porphyrin molecules to store charge, adding and subtracting individual electrons to represent bits of data. Each "bit" will likely be represented by several -- even hundreds or thousands -- of redundant molecules chained together to represent an accurate signal.

Since each molecule can have differing numbers of electrons attached to it, Zettacore believes that the technology could be used to store more than one bit of information per cell. The company said it has designed molecules with eight states, potentially offering a 4-bit-per-cell density.

Here is a simplified diagram of ZettaCore molecules in a memory array (Credit: ZettaCore)

The ZettaCore molecules are very small, about one nanometer in size, and composed of only of a few hundred atoms. You can find more information about the technology on this page, which says that the Zettacore molecules are self-assembling.

Our molecules are also designed to assemble automatically in the right place in an electronic circuit. This allows the molecules to attach only to a particular type of surface (silicon, gold or other metals), to pack tightly on that surface, and to align properly on the surface for electronic operation.

Because of this chemical self-assembly, our molecular memory chips can be manufactured using equipment and processes common in the semiconductor industry.

When will we see real products? Probably sooner than you think.

Zettacore doesn't plan to manufacture its memory cells itself, but either license them to customers or build the chips using a third party foundry. The company has developed a "demonstration chip at a commercially interesting scale," Levine said, and has begun to approach potential customers.

ExtremeTech mentions several other startups, such as Nantero, "which is using carbon nanotubes to develop memory arrays." For more information about Nantero's technology, you can read a previous story, "Here Comes the Buckytube."

Source: Mark Hachman, ExtremeTech, March 16, 2004