NAND flash follow-on technology

Allotropes you can eat

German memory-maker Qimonda wants us to know it has a promising new non-volatile memory [NV-RAM] technology to join the NAND flash replacement candidates: carbon-resistive memory.

Different forms of carbon are known as allotropes, and the element's atoms are bonded in different ways in each allotrope. In graphite the atoms are formed into a flat hexagonal lattice and layered in sheets, whereas in diamond they form a tetrahedral lattice.

Qimonda researchers have worked out how to change the orbital characteristics of the outer electrons of carbon molecules, and thus change the allotrope, by applying an electric current. According to a paper presented at IEDM in San Francisco yesterday, this can change the carbon molecule from conductive graphite, in which the outer electrons have a hybrid orbital value of sp2, to much less conductive diamond in a tetrahedral form with a hybrid orbital value of sp3.

The smallest molecule they can use in this new NV-RAM material is 2 - 3nm whereas the smallest unit in the Numonyx-supported Phase Change Memory [PCM]. a competing NAND successor technology, is ten or more times larger at 30 - 40nm. Ergo a chip of carbon-resistive memory [CRM] will have up to 10 - 20 times more capacity than the same size PCM chip.

It is not known how its size compares to spin-transfer torque random access memory (STT-RAM), another candidate for NAND successor technology, espoused by Hynix.

Both PCM and STT-RAM are said to have DRAM speed as well as non-volatility and so could function both as a DRAM and NAND flash successor. It is not known if CRM could combine both functions. The Qimonda researchers say that they have 'demonstrated repetitive high-speed switching and the potential for multi-level programming'.

It is highly important to vendors that their preferred NAND successor technology becomes standard, because technology and IP licensing fees could flow to them as a result.

The technology is only at the research stage but Qimonda engineers are excited enough about it - their outer electrons having been galvanised by the current of their research - to conduct the session at IEDM. ®