Phase change memory (PCM) cells based on Ge2Sb2Te5 were synthesized and investigated. Currentvoltage measurements demonstrated different final resistances. Transmission electron microscopy (TEM),high resolution electron microscopy (HREM) and the energy dispersive X-ray spectroscopy (EDS) analyses were used to characterize the microstructures of the PCM cells. The architectures,structures and defects in the cells including the deposited elemental distributions and the interfacial structures between electrodes and barrier layers were studied in detail.
WANG KeHAN XiaoDongZHANG ZeWU LiangCaiLIU BoSONG ZhiTangFENG SongLin
We report on the investigation of the origin of high oxide to nitride polishing selectivity of ceria-based slurry in the presence of picolinic acid. The oxide to nitride removal selectivity of the ceria slurry with picolinic acid is as high as 76.6 in the chemical mechanical polishing. By using zeta potential analyzer, particle size analyzer, horizon profilometer, thermogravimetric analysis and Fourier transform infrared spectroscopy, the pre- and the post-polished wafer surfaces as well as the pre- and the post-used ceria-based slurries are compared. Possible mechanism of high oxide to nitride selectivity with using ceria-based slurry with picolinic acid is discussed.
We report on new experimental results for below-diffraction-limited hybrid recording. In our experiments, by means of focused laser assisted magnetic recording, the magnetic domains within TbFeCo thin films are obtained under an external perpendicular direct magnetic field. For a single magnetic medium, the domain size is mainly determined by the focused spot, which is about 620 nm for the laser wavelength λ=406 nm, and a numerical aperture of the lens of 0.80. However, when a silicon thin film structure is inserted between the substrate and the magnetic medium, the recording domains can be reduced obviously. By optimizing the experimental condition, even the size can be reduced to about 100 nm, which is below the diffraction limit, i.e. about 1/6 of the spot size. This is very useful for improving the hybrid recording density in practical applications.
Simulation of the heat consumption in phase change random access memories （PCRAMs） is investigated by a three-dimensional finite element model. It is revealed that the thermal conductivity and electrical conductivity of the buffer layer are crucial in controlling the heating efficiency in RESET process. The buffer layer mater/Ms W, TiN, WOa, Ti02 and poly-germanium （poly-Ge） are applied in the simulation respectively, and compared with each other. The simulation results show that limitation of electrical conductivity is effective on heating efficiency and the limitation of thermal conductivity is important on the reliable RESET process.
A three-dimensional finite element model for phase change random access memory is established to simulate electric, thermal and phase state distribution during （SET） operation. The model is applied to simulate the SET behaviors of the heater addition structure （HS） and the ring-type contact in the bottom electrode （RIB） structure. The simulation results indicate that the small bottom electrode contactor （BEC） is beneficial for heat efficiency and reliability in the HS cell, and the bottom electrode contactor with size Fx=80 nm is a good choice for the RIB cell. Also shown is that the appropriate SET pulse time is lOOns for the low power consumption and fast operation.
GONG Yue-Feng SONG Zhi-Tang LING Yun LIU Yan LI Yi-Jin
