Abstract:The quest for universal memory is driving the rapid development of memories with superior all-round capabilities in non-volatility, high speed, high endurance and low power. Phase-change materials are highly promising in this respect. However, their contradictory speed and stability properties present a key challenge towards this ambition. We reveal that as the device size decreases, the phase-change mechanism changes from the material inherent crystallization mechanism (either nucleation- or growth-dominated)… Show more
“…However, a RESET temperature reduction in the number of crystal nuclei is observed for smaller dimensions, indicating a transition towards growthdominated behaviour. Indeed, for the smallest cells it can be observed that a crystallization process driven purely by 'interfacial growth' from the crystalline-amorphous boundary occurs for GST dimensions of 10 nm and below (see inset of Figure 2), a phenomenon previously reported in pore-type PCM cells [25].…”
Section: B Electrical Switching and Scaling Characteristicsmentioning
Abstract-The scaling potential of patterned probe phasechange memory (PP-PCM) cells is investigated, down to singlenanometer dimensions, using physically realistic simulations that combine electro-thermal modelling with a Gillespie Cellular Automata (GCA) phase-change model. For this study, a trilayer TiN/Ge2Sb2Te5/TiN cell structure (isolated by a SiO2 insulator) was preferred, due to its good performance and practicability, over previously investigated probe-based structures such as those that used diamond-like carbon capping layers or immersion in an inert liquid to protect the phase-change layer (while still allowing for electrical contact). We found that PP-PCM cells with dimensions as small as 5 nm could be successfully amorphized and re-crystallized (RESET and SET) using moderate voltage pulses. The resistance window between the RESET/SET states decreased with a reduction in cell dimensions, but it was still more than order of magnitude even for the smallest cells, predicting that PP-PCM cells are indeed scalable and operable in the sub-10 nm region. Most importantly, it was found that the storage density could be increased by cell size scaling with storage densities as high as 10 Tb/in 2 being achieved, which is significantly higher than the storage densities previously reported in phase-change probe storage, and other probe-based technologies such as thermomechanical, magnetic and ferroelectric probe storage.
IndexTerms-GeSbTe, phase-change materials, scanning-probe memories, patterned probe phase-change memories, scaling, terabit-per-square-inch (Tb/in 2 ) storage density.
“…However, a RESET temperature reduction in the number of crystal nuclei is observed for smaller dimensions, indicating a transition towards growthdominated behaviour. Indeed, for the smallest cells it can be observed that a crystallization process driven purely by 'interfacial growth' from the crystalline-amorphous boundary occurs for GST dimensions of 10 nm and below (see inset of Figure 2), a phenomenon previously reported in pore-type PCM cells [25].…”
Section: B Electrical Switching and Scaling Characteristicsmentioning
Abstract-The scaling potential of patterned probe phasechange memory (PP-PCM) cells is investigated, down to singlenanometer dimensions, using physically realistic simulations that combine electro-thermal modelling with a Gillespie Cellular Automata (GCA) phase-change model. For this study, a trilayer TiN/Ge2Sb2Te5/TiN cell structure (isolated by a SiO2 insulator) was preferred, due to its good performance and practicability, over previously investigated probe-based structures such as those that used diamond-like carbon capping layers or immersion in an inert liquid to protect the phase-change layer (while still allowing for electrical contact). We found that PP-PCM cells with dimensions as small as 5 nm could be successfully amorphized and re-crystallized (RESET and SET) using moderate voltage pulses. The resistance window between the RESET/SET states decreased with a reduction in cell dimensions, but it was still more than order of magnitude even for the smallest cells, predicting that PP-PCM cells are indeed scalable and operable in the sub-10 nm region. Most importantly, it was found that the storage density could be increased by cell size scaling with storage densities as high as 10 Tb/in 2 being achieved, which is significantly higher than the storage densities previously reported in phase-change probe storage, and other probe-based technologies such as thermomechanical, magnetic and ferroelectric probe storage.
IndexTerms-GeSbTe, phase-change materials, scanning-probe memories, patterned probe phase-change memories, scaling, terabit-per-square-inch (Tb/in 2 ) storage density.
“…Besides, endurance up to 3.3 × 10 5 cycles without failure (Fig. 4b) also demonstrates that Sc 0.1 Sb 2 Te alloy has great potential for PCRAM application 24 .Figure 4( a ) Resistance-Voltage characteristics of Sc 0.1 Sb 2 Te based PCRAM device with difference voltage pulse widths. The inset depicts the schematic diagram of the T-shaped PCRAM cell structure.…”
Phase change random access memory (PCRAM) has gained much attention as a candidate for nonvolatile memory application. To develop PCRAM materials with better properties, especially to draw closer to dynamic random access memory (DRAM), the key challenge is to research new high-speed phase change materials. Here, Scandium (Sc) has been found it is helpful to get high-speed and good stability after doping in Sb2Te alloy. Sc0.1Sb2Te based PCRAM cell can achieve reversible switching by applying even 6 ns voltage pulse experimentally. And, Sc doping not only promotes amorphous stability but also improves the endurance ability comparing with pure Sb2Te alloy. Moreover, according to DFT calculations, strong Sc-Te bonds lead to the rigidity of Sc centered octahedrons, which may act as crystallization precursors in recrystallization process to boost the set speed.
“…The smaller grain size benefits the crystallization rate and reduces the power consumption of PCM device. 16 The Fig. 3(d)-3(f) display the HRTEM results of tested films.…”
In this paper, phase change characteristics of SiO 2 -doped Sb 2 Te materials were systematically investigated. It was found that phase change properties of Sb 2 Te were remarkably improved through SiO 2 addition. The crystallization temperature is enhanced obviously, showing a relatively good thermal stability. With increasing concentration of SiO 2 , the temperature for 10-yr data retention increased to 131 • C. In addition, the SiO 2 -doped Sb 2 Te based device remains a fast operation speed (10 ns). XRD and TEM results suggest the incorporation of SiO 2 suppress the crystallization of Sb 2 Te and then smaller grain size obtained, which benefits to the operation speed and power consumption.
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