Nonvolatile Memory Based on Phase Change in Se–Sb–Te Glass

Nakayama, Keiichi I.; Kojima, Kazuhiko; Imai, Yoshihiko; Kasai, Tokuzo; Fukushima, Sanae; Kitagawa, Akio; Kumeda, Minoru; Kakimoto, Y.; Suzuki, Masakuni

doi:10.1143/jjap.42.404

Cited by 67 publications

(49 citation statements)

References 5 publications

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“…[1][2][3][4][5][6][7][8][9][10] In both the optical and electrical phase-change data storage methods, data are written by locally melt quenching the crystalline phase-change film into an amorphous state using an optical ͑laser͒ or electrical pulse. The written amorphous bit can be read due to its large optical ͑reflectivity͒ or electrical ͑resistivity͒ contrast with the surrounding crystalline background.…”

Section: Influence Of Capping Layers On the Crystallization Of Doped mentioning

confidence: 99%

Influence of capping layers on the crystallization of doped SbxTe fast-growth phase-change films

Pandian

Kooi

Hosson

et al. 2006

Journal of Applied Physics

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Isothermal crystallization of doped Sb x Te fast-growth phase-change films, with and without capping layers, was investigated using transmission electron microscopy, which provided direct and quantitative information on nucleation and growth processes separately. Two types of amorphous dielectric layers, ZnS -SiO 2 and GeCrN, were used for sandwiching the Sb x Te films to form typical trilayer stacks, which are the active part in applications. The nucleation and growth parameters of Sb x Te films were found to be influenced by the dielectric capping layers. The crystal growth rate is temperature dependent and it reduces when the film is sandwiched between the dielectric layers. The reduction in growth rate differs with the capping layer type. The capping layer influence on the growth rate is pronounced at lower temperatures ϳ160°C, but tends to vanish at higher temperatures ϳ200°C. The activation energy for crystal growth is 2.4± 0.3 eV for an uncapped film and it increases ϳ40% when the capping layers, GeCrN or ZnS -SiO 2 , are added. A temperature and time dependent nucleation rate is found and it is accelerated ϳ1.7 times by GeCrN layers, whereas it is retarded ϳ5 times by ZnS -SiO 2 layers. The activation energy for crystal nucleation is 6.1± 0.4 eV for an uncapped film and it is not noticeably altered by the capping layers. These variations observed in the crystallization kinetics are attributed to variations in interface energy between the phase-change film and the capping layers or vacuum and the confinement effect by the capping layers on the phase-change film.

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Section: Influence Of Capping Layers On the Crystallization Of Doped mentioning

confidence: 99%

Influence of capping layers on the crystallization of doped SbxTe fast-growth phase-change films

Pandian

Kooi

Hosson

et al. 2006

Journal of Applied Physics

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“…The SeSbTe system needs longer set operation (< 300 ns) than that of the GeSbTe system (10-100 ns). Although, the T m of the SeSbTe system is lower than that of the GeSbTe system [7]. For example, the T m of the Se 15 Sb 15 Te 70 and Ge 2 Sb 2 Te 5 are 672 K and 889 K [14], respectively.…”

Section: Discussionmentioning

confidence: 92%

“…The sample preparation, composition of phase change alloy and structure of memory cells are the same as those of conventional PRAM [7]. Figure 2 shows the basic electrical circuit used to control the phase change between the amorphous and crystalline states.…”

Section: Sample Preparation and Experimentsmentioning

confidence: 99%

Pulse number control of electrical resistance for multi-level storage based on phase change

Nakayama

Takata

Kasai

et al. 2007

J. Phys. D: Appl. Phys.

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Abstract. Phase change nonvolatile memory devices composed of the SeSbTe chalcogenide semiconductor thin film were fabricated. The resistivity of the SeSbTe system was investigated to apply to multi-level data storage. The chalcogenide semiconductor acts as a programmable resistor that has a large dynamic range. The resistance of the chalcogenide semiconductor can be set in intermediate resistances between the amorphous and crystalline states using electric-pulses of a specified power, and it can be controlled by repetition of the electric pulses. The size of the memory cell used in the present work is 200 nm thick with a contact area of 1 µmφ. The resistance of the chalcogenide semiconductor gradually varies from 41 kΩ to 840 Ω with in octal steps. The resistance of the chalcogenide semiconductor decreases with an increase in the number of applied pulses. The step-down characteristic of the resistance can be explained as the crystalline region of the active phase change region is increased with an increase in the number of applied pulses. The extent of crystallization was also estimated by the overall resistivity of the active region of the memory cell.

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“…Phase-change materials are widely applied for optical data storage and ovonic unified memory [1][2][3]. Phase change between amorphous and crystalline states can be induced by laser or electrical pulse in the chalcogenide films.…”

Section: Introductionmentioning

confidence: 99%

Selective wet etching of Ge2Sb2Te5 phase-change thin films in thermal lithography with tetramethylammonium

Deng

Geng

2011

Appl. Phys. A

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In this paper, we study Ge 2 Sb 2 Te 5 phase-change film as a promising inorganic photoresist using organic alkaline: tetramethylammonium hydroxide (TMAH) solution, instead of inorganic alkali or acid as etchant. The basic etching properties are investigated by prior and posterior annealing Ge 2 Sb 2 Te 5 films. Selectivity is found to be dependent on concentration of TMAH. There is a good selectivity in the 25% TMAH solution, in which the amorphous state is etched away, whereas the crystalline state remains. The etching rate decreases when the concentration of TMAH is diluted; and an opposite selectivity, compared with 25% TMAH solution, is observed in the 0.125% TMAH solution. Selective etching with laser crystallization in different power levels is also studied, and an excellent wet selectivity in the 25% TMAH solution is obtained. The remaining crystalline lines are observed by atomic force microscopy. The surface roughness after etching is at a good level. The selective wet-etching mechanism is also discussed.

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Nonvolatile Memory Based on Phase Change in Se–Sb–Te Glass

Cited by 67 publications

References 5 publications

Influence of capping layers on the crystallization of doped SbxTe fast-growth phase-change films

Influence of capping layers on the crystallization of doped SbxTe fast-growth phase-change films

Pulse number control of electrical resistance for multi-level storage based on phase change

Selective wet etching of Ge2Sb2Te5 phase-change thin films in thermal lithography with tetramethylammonium

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