Crystallization process and amorphous state stability of Si-Sb-Te films for phase change memory

Abstract

Crystallization process and amorphous state stability of Si-Sb-Te films with different Si concentration (10, 20 at. %) and Sb/Te ratio (2:3 and 1:1) have been studied and compared with Ge2Sb2Te5 (GST) film by in situ film resistance measurements. The effects of Si concentration and Sb content on crystalline resistivity, crystallization temperature, activation energy of crystallization, and amorphous state stability of films have been studied. The activation energy Ea of crystallization of GST film was confirmed to be 2.34 eV, while the activation energy Ea of Si10Sb36Te54 film increased to 2.99 eV and further reached to 3.65 eV for Si20Sb32Te48 film when the Si content increased to 20 at. %. Si addition increased the crystallization temperature and crystalline resistivity of Si-Sb-Te films largely, and enhanced the amorphous state stability of the films, while Sb revealed contrary effects to Si. The microstructures of Si-Sb-Te films were analyzed through x-ray diffraction and high resolution transmission electron microscopy. Phase separation has been observed in annealed Si-Sb-Te films, and Si-Sb-Te films crystallized into rhombohedral Sb2Te3 phase surrounded by amorphous Si-rich grain boundaries with high resistance, which would be helpful to reduce the writing current of phase change memory.

Investigation on pseudo-binary ZnSb–Sb2Te3 material for phase change memory application

“…2(d) and (e), high Zn-doping concentration increases the amorphous thermal stability of ZST4 and ZST5 films greatly, so we have to increase the annealing temperature to observe the drop of the sheet resistance. Generally speaking, the crystallization time decreases largely when the Sb/Te ratio increases [25]. The reason is that more Sb in Zn-Sb-Te films increases the crystallization rate of the films.…”

Stress reduction and performance improvement of phase change memory cell by using Ge2Sb2Te5–TaOx composite films

“…Figure 4 shows TEM image of the GST-TaO x ͑38.3 mol %͒ film after heating at 350°C for 5 min. Feng et al 22 reported that phase separate ͑Sb 2 Te 3 nanocrystals were surrounded by amorphous Si-rich grain boundaries͒ was found in annealed SiSbTe films. Lee et al 15 reported that separate domain formation ͑spherical Ge 2 Sb 2 Te 5 -rich domains were enclosed by SiO x -rich domains͒ was found in Ge 2 Sb 2 Te 5 -SiO x mixed layer.…”

Silicon doping effect on the crystallization behavior of Ge2Sb2Te5 film

“…However, there are some issues still need to be solved in PCRAM application. One of the most crucial issues is to reduce the power consumption in PCRAM devices, especially the consumption during the RESET process . Till now, many efforts such as realizing multilevel storage , inserting a heating layer , optimizing the structure of the PCM device , have been made to try to achieve these goals.…”