Sb-rich Si–Sb–Te Phase-Change Material for Phase-Change Random Access Memory Applications

An Sb-rich (48 at.%) Si–Sb–Te phase-change material with moderate Si content (24 at.%) is proposed for phase-change random access memory (PCRAM) applications. The real time amorphous to crystalline transformation was studied by in situ transmission electron microscopy observations and in situ resistance measurements. The results of time-dependent resistance measurements show that the $\hbox{Si}_{24}\hbox{Sb}_{48} \hbox{Te}_{28}$ phase-change material has data retention of 10 years at about 382 K, suggesting a more stable amorphous state than the usual $\hbox{Ge}_{2}\hbox{Sb}_{2} \hbox{Te}_{5}$ (GST) phase-change material. The reversible set –reset ability of the PCRAM cell based on the $\hbox{Si}_{24}\hbox{Sb}_{48}\hbox{Te}_{28}$ phase-change material is much better than that of the device employing GST. The programming cycles can reach $\hbox{2.2} \times \hbox{10}^{4}$ under a set pulse of 1.5 V/1000 ns with a 30-ns falling edge and a reset pulse of 3.5 V/400 ns, whereas the resistance contrast retains a value of as large as two orders of magnitude.

I. Introduction

Phase-Change random access memory (PCRAM) is widely considered as one of the most promising candidates for the next-generation nonvolatile memory because of its excellent characteristics [1]–[6]. Although PCRAM has been commercialized in certain application fields at present, there are still some problems needed to be solved. First, for large-scale commercial applications, low power consumption is one of the most important issues. In addition, the volume change of the most commonly used phase-change material (GST) during the operation process is relatively large, which will lead to unreliable contact between the phase-change material and the heating electrode, thus deteriorating the reliability of the PCRAM device [7]. In order to improve the performance of the PCRAM, many efforts, including optimization of GST and device structure, have been carried out in the past years [8]–[10]. Furthermore, screening a proper new phase-change material is also an effective way to overcome the obstacles in the current PCRAM technology.