Non-volatile memory

In the April issue of Nature Materials, scientists at Philips Research will publish details of an innovative phase-change memory that promises to match the speed, density, low voltage and low power consumption requirements of future deep sub-micron silicon chips.

Unlike existing non-volatile memory technologies such as Flash memory, the performance of this new memory improves in virtually every respect the smaller you make it.

Phase-change materials, which change their physical properties depending on whether they are in their amorphous or crystalline phase, are widely used in optical storage media such as DVD Recordable and Rewritable discs. In these discs, it is the reflectivity of the material that changes, with a laser being used both to heat the material to the required temperature in order to switch it between its amorphous and crystalline phases and to detect the resultant change in its reflectivity.

Philips' new solid-state memory cell employs similar phase-change materials deposited as an ultra-thin film on the surface of a silicon chip, and uses an electric current to switch it between phases and to detect the resultant change in its electrical resistance. Although similar memory devices have been investigated before, Philips' says that its new 'line-cell' phase-change memory has the potential to meet both the performance and scaling requirements of future nano-electronic silicon chips.