Characteristics of Si-Sb-Te Films for Phase Change Memory
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0918-H08-04
Characteristics of Si-Sb-Te Films for Phase Change Memory Jie Feng1, Yin ZHANG1, Baowei Qiao1, Yanfei Cai2, Yinyin Lin2, Tingao Tang2, Bingchu Cai1, and Bomy Chen3 1 Key lab. for thin film and microfabrication of Ministry of Education, Inst. of Micro/Nano Sci.& Tech, Shanghai Jiao Tong University, 1954 Huasan Road, Shanghai, 200030, China, People's Republic of 2 State Key Laboratory of ASIC £¦ System, Fudan University, Shanghai, 200433, China, People's Republic of 3 Silicon Storage Technology, Inc., 1171 Sonora Court, Sunnyvale, CA 94086
ABSTRACT The novel phase change materials Si-Sb-Te films were prepared. The crystallization temperature of films increases with the increasing of Si concentration. Phase separation was observed in the Si-Sb-Te films, the dominant phase is Sb2Te3. The melting temperature of Si-SbTe decreased to ~550ºC lower than 640ºC of Ge2Sb2Te5. The decrease of film thickness of Si-SbTe films is less than 2% after annealing at 400ºC, which is less than ~7% of the film thickness change of Ge2Sb2Te5 film. The crystalline resistivity of Si-Sb-Te films increased and the ratio of amorphous/crystalline resistivity of Si-Sb-Te films increased also comparing with Ge2Sb2Te5 film, which is benefit to reduce the writing current and keep higher on/off ratio of phase change memory. Reversible switching was performed in the devices with Si-Sb-Te films. The device with Si14.3Sb28.6Te57.2 film can be programmed with a 100 ns SET pulse and a 20 ns RESET pulse. The Reset current is only 1.37mA for a 10µm-sized device. INTRODUCTION Phase change memory (PCM) based on the rapid reversible phase change effect in the chalcogenide film has been regarded as one of the candidates for the next-generation nonvolatile memories, because of its low cost, low programming voltage, high endurance, good compatibility with CMOS technologies, and excellent scalability to nanometer cell size [1]-[3]. The conventional chalcogenide film used in PCM is Ge2Sb2Te5 film (GST), which has been widely used in rewritable compact disk (CD) and digital versatile disk (DVD). However large writing current is a crucial issue before the commercial application of PCM [2]. In order to reduce the writing current, some approaches from two directions are proposed, one is reducing the programming volume by improving the cell structure [4][5], the other is optimizing the properties of phase change material, for example, increase the crystalline resistance by nitrogen doping [5] or silicon doping [6]. On the other hand, the film thickness of GST decreases about 7% after it crystallizes from amorphous state, the larger change of film thickness would be disadvantageous to the stability of PCM. In order to reduce the writing current and improve the stability of PCM, developing the new chalcogenide films other than Ge2Sb2Te5 film is necessary.
It has been reported that Si-doping has a great effect on the phase change properties, which increases the crystalline resistivity and decreases the melting temperature of Ge2Sb2Te5 film [6]. In this study,
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