Cu对用于高速相变存储器的Sb2Te薄膜的结构及相变的影响研究

采用原位X射线衍射仪、拉曼光谱仪和X射线反射仪分别研究了Cu-Sb₂Te 薄膜的微结构、成键结构和结晶前后的密度变化. Sb₂Te薄膜的结晶温度随着Cu含量的增加而增大. 在10 at.%和14 at.% Cu的Sb₂Te薄膜中, Cu与 Te 成键, 结晶相由六方相的Cu₇Te₄、菱形相的Sb及六方相的Sb₂Te构成. 10 at.% 和14 at.% Cu 的Sb₂Te薄膜在结晶前后的厚度变化分别约为3.2%和 4.0%, 均小于传统的Ge₂Sb₂Te₅ (GST)薄膜. 制备了基于Cu-Sb₂Te薄膜的相变存储单元, 并测试了其器件性能. Cu-Sb₂Te器件均能在10 ns的电脉冲下实现可逆SET-RESET操作. SET和RESET操作电压随着Cu含量的增加而减小. 疲劳测试结果显示, Cu 含量为10 at.%和14 at.%的PCRAM单元的循环操作次数分别达到1.3×10⁴和1.5×10⁵, RESET和SET态的电阻比值约为100. Cu-Sb₂Te可以作为应用于高速相变存储器(PCRAM)的候选材料.

Effect of Cu on the structure and phase-change characteristics of Sb2Te film for high-speed phase change random access memory

In this paper, in-situ X-ray diffratometer, Raman spectrometer, and X-ray reflectometer are employed to study the crystal structure, bonding states, and density change upon crystallization of Cu-Sb₂Te films. It is shown that the crystallization temperature increases with increasing Cu content due to much more energy being required to overcome the rigid atomic network for the atoms rearrangement as a result of the complex branching and cross links. In X-ray diffraction pattern, both hexagonal Cu₇Te₄ and Sb₂Te peaks have nearly the same peak positions, while the rhombohedral Sb peaks shift obviously their positions toward a small angle upon heating, suggesting a significant increase in lattice parameters of Sb phase. A Cu-Te bond is formed in Sb₂Te films containing 10 at% and 14 at% Cu which are crystalized into hexagonal Cu₇Te₄, rhombohedral Sb and hexagonal Sb₂Te three phases. When Cu concentration increases to 19 at%, Cu-Te bond becomes full, and the excess of Cu will bond with Sb. Compared with Ge₂Sb₂Te₅ (GST), Sb₂Te films with 10 at% and 14 at% Cu have lower density changes upon crystallization which are about 3.2% and 4.0%, respectively. Phase change random access memory (PCRAM) based on Cu-Sb₂Te is successfully fabricated and characterized. Operations of set-reset can be realized in a 10 ns pulse for Cu-Sb₂Te based PCRAM. The value of set and reset operation voltage decreases with increasing Cu content. The endurance test shows that the operation cycle numbers can reach 1.3×10⁴ and 1.5×10⁵ for the 10 at% and 14 at% Cu-based PCRAMs, respectively. The resistance ratio of reset and set states maintains a balance of about 100. Cu-Sb₂Te film may be considered as one of the promising candidates for high-speed PCRAM.