Crystallization Characteristics of SiNx-Doped SbTe Films for Phase Change Memory

Abstract

SbTe films doped with different SiNx concentrations (2, 5, 17, 25at.%) are prepared by co-sputtering with Si3N4 and SbTe alloy targets. In order to study the crystallization process and amorphous state stability and to compare with Ge2Sb2Te5 (GST) and pure SbTe films, x-ray diffraction (XRD), transmission electron microscopy (TEM) and in situ film resistance measurements are carried out. SiNx doping enhances the amorphous state stability of the SbTe films. The temperature for 10-year retention of amorphous state of pure SbTe films is −11°C and that of 17at.% SiNx-doped SbTe films increases to 75°C. SiNx addition increases the crystallization temperature and the electrical resistivity of SbTe films. The microstructures of SiNx-doped SbTe films are analyzed through XRD and TEM. After annealing at 350°C, SiNx-doped SbTe films crystallized into a kind of nanocomposite films with rhombohedra Sb2Te3 nanoparticles embedded into an amorphous SiNx matrix. The nanocomposite structure and higher crystalline resistivity of the SiNx-doped SbTe films is helpful to reduce the RESET current of phase change memory.