Scaling properties of phase change materials

Scalability is one of the most important properties of phase-change non-volatile memory. In this paper we review the scaling properties of ultra-thin films and phase change nanostructures investigated by time-resolved X-ray diffraction. Phase change nanostructures were fabricated by electron-beam lithography and diblock-copolymer self-assembly based lithography using sputter deposition and spin-on deposition. Films as thin as 1.3 nm and nanoparticles as small as 10 nm of various phase change materials all showed transitions from the amorphous to the crystalline phase. Based on these promising scaling properties phase change devices were fabricated using doped GeSb with a record low cross-section of the phase change material of only 3 nmtimes20 nm. The cells were repeatedly switched and showed good thermal stability. To investigate the properties of phase change nanoparticles at sizes smaller than the limits of lithography, nanoparticles were synthesized using a solution-based chemical approach. The sizes of these germanium selenide and germanium telluride phase change nanoparticles were in the 1-10 nm range, and the particles were crystalline as synthesized. Further studies of the properties of these nanoparticles are planned.