Nanoscale observations of the operational failure for phase-change-type nonvolatile memory devices using Ge2Sb2Te5 chalcogenide thin films

Yoon, Sung‐Min; Choi, Kyu-Jeong; Lee, Nam-Yeal; Lee, Seung-Yun; Park, Young-Sam; Yu, Byoung–Gon

doi:10.1016/j.apsusc.2007.07.098

Cited by 52 publications

(23 citation statements)

References 10 publications

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“…The electric current effect on crystalline GST has been typically associated with a high current density of over 10 7 A/cm 2 1011121314. In this condition, electric current generates disorder or massive displacement of atoms because the driving force for migration is sufficient to create structural changes with high current density.…”

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confidence: 99%

New pathway for the formation of metallic cubic phase Ge-Sb-Te compounds induced by an electric current

Park

Cho

Jeong

et al. 2016

Sci Rep

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The novel discovery of a current-induced transition from insulator to metal in the crystalline phase of Ge2Sb2Te5 and GeSb4Te7 have been studied by means of a model using line-patterned samples. The resistivity of cubic phase Ge-Sb-Te compound was reduced by an electrical current (~1 MA/cm2), and the final resistivity was determined based on the stress current density, regardless of the initial resistivity and temperature, which indicates that the conductivity of Ge-Sb-Te compound can be modulated by an electrical current. The minimum resistivity of Ge-Sb-Te materials can be achieved at high kinetic rates by applying an electrical current, and the material properties change from insulating to metallic behavior without a phase transition. The current-induced metal transition is more effective in GeSb4Te7 than Ge2Sb2Te5, which depends on the intrinsic vacancy of materials. Electromigration, which is the migration of atoms induced by a momentum transfer from charge carriers, can easily promote the rearrangement of vacancies in the cubic phase of Ge-Sb-Te compound. This behavior differs significantly from thermal annealing, which accompanies a phase transition to the hexagonal phase. This result suggests a new pathway for modulating the electrical conductivity and material properties of chalcogenide materials by applying an electrical current.

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confidence: 99%

New pathway for the formation of metallic cubic phase Ge-Sb-Te compounds induced by an electric current

Park

Cho

Jeong

et al. 2016

Sci Rep

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“…Thus, only a small part of the whole GST layer, corresponding to point A and its adjacent region, is thought to participate in the phasechange process. In our previous work [5], a Ge 16 Sb 37 Te 47 layer generated after 2 × 10 6 repetitive cycling caused a short-mode failure of a PCM device, which indicates that the Ge-deficient GST layer containing a smaller amount of Ge than Ge 2 Sb 2 Te 5 hardly transforms into the amorphous state. Therefore, it is probable that the phase transition does not occur in the Ge-deficient GST layer, including points C and D. Fig.…”

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confidence: 99%

Phase-change memory device fabricated using solid-state alloying

Lee¹,

Park²,

Yoon³

et al. 2010

Electron. Lett.

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A novel fabrication method for phase-change memory devices using solid-state alloying is presented, which enables programming current reduction. Preformed pores, exposing germanium layers, were filled with antimony-tellurium layers, and germanium -antimony -tellurium (GST) phase-change layers were prepared by the solid-state alloying of germanium and antimony-tellurium. Programming currents for reset and set operations were drastically reduced compared to those of a control device. The decreased programming currents are attributed to a small-sized programmable volume and the existence of GST thermal barriers.Introduction: Chalcogenide alloys comprising chalcogen atoms S, Se and Te reversibly change between the amorphous and crystalline phases in response to light or electrical pulses. Electrical resistance of the chalcogenide materials differs greatly depending on their crystalline structure, so they have been adopted as an active layer for phase-change memory (PCM) applications. The PCM has drawn much attention as emerging non-volatile memory because of its excellent scaling prospects compared to floating-gate non-volatile memory devices. The high programming current for the RESET operation (i.e. the phase transition from the crystalline to the amorphous state) has been one of the most challenging barriers to commercialisation of PCM [1]. Many methods for decreasing programming current have been suggested such as device scaling [2] and development of new phase-change materials or heater materials [3]. Aggressive scaling of PCM devices is the most promising approach, but it usually requires very expensive process technology. In this Letter, we report a novel fabrication method for producing low-power PCM devices by which the need for the aggressive scaling is reduced. We have prepared a small-sized phase-change material in a self-aligned manner by using solid-state alloying, and have examined the performance improvement of PCM devices including the phase-change material.

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“…As the potential candidate, PCM based on GST-225 must have good SET-RESET performance and high reliability. As the PCM density increases, PCM experiences harsher operating conditions, such as high current density and temperature, which can cause failure and reliability issues induced by compositional change and void formation [4,5]. While phase transition processes are well understood, issues on performance and reliability are getting more and more attention in recent years, which makes the failure analysis of PCM becomes more and more important.…”

Section: Introductionmentioning

confidence: 99%

RESET failure analysis of phase change memory based on Ge2Sb2Te5

Wang

Chen

et al. 2017

IEICE Electron. Express

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Some nonvolatile phase change memory (PCM) cells with 80 nm heating electrodes are found early RESET failure. The causes, which result in the early failure of the PCM, have been studied. Compared the energy dispersive X-ray spectroscopy (EDS) results, it is observed some segregation has occurred in the components at the positions close to the TiN and bottom electron contact (BEC) interface for the early failed cells. The main causes are considered to be the unstable interface between the Ti-rich TiN and the Ge 2 Sb 2 Te 5 (GST-225) layers and the inconsistent manufacturing process. Thanks to the segregation, the chemical components of the material close to BEC in the early failed cells are found changed. The changed material is taken as the immediate reason for the RESET failure, which has been confirmed by a two-dimensional finite analysis.

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Nanoscale observations of the operational failure for phase-change-type nonvolatile memory devices using Ge2Sb2Te5 chalcogenide thin films

Cited by 52 publications

References 10 publications

New pathway for the formation of metallic cubic phase Ge-Sb-Te compounds induced by an electric current

New pathway for the formation of metallic cubic phase Ge-Sb-Te compounds induced by an electric current

Phase-change memory device fabricated using solid-state alloying

RESET failure analysis of phase change memory based on Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub>

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