Jul 1, 2011
Nanolayers improve performance of phase change memory
Thin film experts from Seoul National University and Hynix Semiconductor in Korea have shown that the thermal efficiency of phase change random access (PcRAM) can be enhanced by incorporating SiO2 into Ge2Sb2Te5 (GST) and report on the structure's physical, structural and electrical properties. Two different phases (amorphous/polycrystalline) of Ge2Sb2Te5 correspond to the two digital states in PcRAM and the transition between the two phases is obtained by Joule heating. By enhancing the thermal efficiency of the material, the team aims to improve the performance of the PcRAM devices.
The thermal conductivity was largely lowered by SiO2-doping because thermal conduction by phonon vibration is sensitive to microstructure. SiO2-doped Ge2Sb2Te5 was observed to have a layered structure resulting from the inhomogeneous distribution of SiO2 after annealing.
In order to clarify the influence of SiO2-doping on device performance, the team fabricated a test cell and performed electrical characterization on the PcRAM device.
Electro-thermal simulation revealed that the reduced thermal conductivity contributes to the improvement in cell efficiency as well as to a reduction in the reset current. In addition, the SiO2-doped GST has a large sensing margin comparable to that of GST, which is usually unexpected from other dopants, such as O, N and Si.
More information can be found in the journal Nanotechnology.
About the author
S W Ryu is a postdoctoral fellow in the Y Nishi group at electrical engineering, Stanford University, Stanford, US, and his research is currently focused on resistive switching random access memory (ReRAM). H-K Lyeo is exploring the thermal properties of thin film materials. J H Lee, Y B Ahn and G H Kim are PhD students at Seoul National University. C H Kim, S G Kim, S-H Lee, K Y Kim, J H Kim and W Kim are affiliated to Hynix Semiconductor Inc. C S Hwang and H J Kim lead two research groups at Seoul National University investigating materials related to next generation semiconductor devices.