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

SbTe films doped with different SiN_x 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. SiN_x 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.% SiN_x-doped SbTe films increases to 75°C. SiN_x addition increases the crystallization temperature and the electrical resistivity of SbTe films. The microstructures of SiN_x-doped SbTe films are analyzed through XRD and TEM. After annealing at 350°C, SiN_x-doped SbTe films crystallized into a kind of nanocomposite films with rhombohedra Sb₂Te₃ nanoparticles embedded into an amorphous SiN_x matrix. The nanocomposite structure and higher crystalline resistivity of the SiN_x-doped SbTe films is helpful to reduce the RESET current of phase change memory.