Thursday, July 08, 2010

US Patent 7749801 - Phase change memory fabricated with CNTs

Phase change memory is appearing to be the primary choice for a next-generation universal non-volatile memory. This patent from Korea Advanced Institute of Science & Technology teaches a way to reduce the contact area between the bottom electrode and phase change material using vertical carbon nanotubes thus increasing the integration density of phase change memory cells. Claim 1 reads:

1. A method for fabricating a phase change memory using carbon nanotubes, the method comprising:

disposing a catalyst for forming a plurality of carbon nanotubes over predetermined regions of a current source electrode supplying external current to a target, thereby widening the predetermined regions responsible for the phase change and increasing the threshold margin of a phase change material;

growing the carbon nanotubes in vertical direction using the catalyst as a seed to form carbon nanotube electrodes;

depositing an insulation layer over the current source electrode in a manner to cover the carbon nanotube electrodes;

polishing the insulation layer until flush with the carbon nanotube electrodes to form a planarized insulation layer flush with the carbon nanotube electrodes; and

forming a phase change material layer over the planarized insulation layer, which is flush with the carbon nanotube electrodes, in contact with the carbon nanotube electrodes.