Evolution of Phase-Change Memory for the Storage-Class Memory and Beyond

Kim, Tae-Hoon; Lee, Seung-Yun

doi:10.1109/ted.2020.2964640

Cited by 96 publications

(43 citation statements)

References 61 publications

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“…[ 3 ] Within their competitive substitutes, phase‐change random access memory (PCRAM) has received more attention due to its ability to operate in both electronic and optical manners. [ 4,5 ] Such unique feature arises from the so‐called phase‐change materials (PCMs) whose electronic properties can be rapidly and reversibly switched between an electrically conductive crystalline and an electrically resistive amorphous states according to an external electrical excitation. [ 6,7 ] This advantageous switching characteristic undoubtedly renders PCRAM as one of the most promising candidates in the future RAM market.…”

Section: Figurementioning

confidence: 99%

Design of Phase‐Change Memory Using Apertureless Scanning Near‐Field Optical Microscopy in the Near‐Infrared Region

Liu

Wang

2020

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A novel optical secondary storage memory operated in the near‐infrared (NIR) region is developed through the integration of an apertureless scanning near‐field optical microscopy probe with the conventional Ge2Sb2Te5 storage stack. The probe composite and the optical coefficients of the storage media stack, particularly for the indium tin oxide capping layer, are optimized according to a previously developed electromagnetic wave model, and a newly established density functional theory model, respectively. The dielectric core and the metal coating medium of the probe are devised to be glass and barium, respectively, to provide high electric field in the NIR region, while the thickness of the ITO capping layer is chosen to be 3 nm here to provide high optical transmittance simultaneously with exemption of complex fabrication process. The recording operation of the aforementioned optimized device is subsequently simulated by a newly established thermo‐optics model, and its feasibility of achieving ≥Tbit in−2, 108 bits per second, and picojoule energy consumption per bit is theoretically demonstrated.

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Section: Figurementioning

confidence: 99%

Design of Phase‐Change Memory Using Apertureless Scanning Near‐Field Optical Microscopy in the Near‐Infrared Region

Liu

Wang

2020

Physica Rapid Research Ltrs

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“…Phase change memory (PCM) stands as a promising candidate for storage, [1,2] neuromorphic computing, [3] radio-frequency applications, [4,5] and in-memory computing, [6][7][8] thanks to its nonvolatility, long retention, high endurance, short switching time, and compatibility with the back-end of line of standard silicon processing. [9] Intel's Optane memory, a PCM-based memory aimed at storage class memory applications, [10] is an example of the maturity of this technology.…”

Section: Introductionmentioning

confidence: 99%

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Uncovering Phase Change Memory Energy Limits by Sub‐Nanosecond Probing of Power Dissipation Dynamics

Stern

Wainstein

Keller

et al. 2021

Adv Elect Materials

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ratio (>10 3 ) between the amorphous and crystalline phase of chalcogenides glasses, mainly compounds of the ternary Ge x Sb y Te z . The phase transition is triggered by Ovonic threshold switching, [1,11] where the resistance of the chalcogenide is reduced above a certain threshold voltage, enabling high current densities, and selfheating for crystallization.The memory cell structure consists of a phase change material, such as, Ge 2 Sb 2 Te 5 (GST), sandwiched between two electrodes. Electrical current crowding is achieved by either a small-area heater bottom electrode (BE) in a mushroom-type cell, or a narrow pore in the surrounding dielectric of the PCM layer in a so-called confined cell. [2] To crystallize the PCM (i.e., set) to its low resistance state (LRS), a medium-amplitude voltage or current pulse is applied, which heats the material above its crystallization temperature. The set pulse must be sufficiently long to allow for the material to crystallize. To amorphize the cell (i.e., reset) to its high resistance state (HRS), a large-amplitude electrical pulse is applied for a short time (or with a short fall time) to melt the material and rapidly quench it below the crystallization temperature. [2,12,13] Because the phase transition is thermally induced, devicelevel heat management is crucial. The energy and power consumption are of great concern, and their fundamental limits are yet to be fully understood. [14] Particularly, the reset process includes heating the phase change material above its melting temperature (typically T m > 600 °C) which requires very high power density, on the order of ≈10 MW cm −2 (100 mW µm −2 ). Reports on the values of reset power (during the pulse) and energy are scarce because of the need to capture the current and voltage during a short transient (typically less than 100 ns), but the reported energies per area are in the range of ≈1 J cm −2 (10 nJ µm −2 ). [15,16] Previous research efforts toward improving energy-efficiency (heating energy per device area) of the meltquench process in PCM focused on thermal engineering of materials, [17,18] interfaces, [19,20] and device structure. [21,22] However, the range of thermal properties of materials and their interfaces is limited. [23] In this article, we probe the power dissipation dynamics of PCM reset with sub-nanosecond (ns) resolution and show that the energy efficiency improves with the reduction of Phase change memory (PCM) is one of the leading candidates for neuromorphic hardware and has recently matured as a storage class memory. Yet, energy and power consumption remain key challenges for this technology because part of the PCM device must be self-heated to its melting temperature during reset. Here, it is shown that this reset energy can be reduced by nearly two orders of magnitude by minimizing the pulse width. A high-speed measurement setup is utilized to probe the energy consumption in PCM cells with varying pulse width (0.3-40 nanoseconds) and uncover the power dissipation dynamics. A key finding is that the swit...

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“…In recent years, phase-change random-access memories (PCRAMs) based on ternary Ge-Sb-Te chalcogenides have been extensively studied due to their huge potential as a candidate for nonvolatile memory (NVM). [1][2][3] The Ge-Sb-Te chalcogenidesbased 3D PCRAM array enabled by coupling a selector element has been commercialized by Intel and Micron. [4,5] PCRAMs utilize a joule heating-induced fast and reversible phase transition between the amorphous and crystalline phases in phasechange materials (PCMs) and information can be stored using the significant resistance difference between the two phases.…”

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Temperature‐Dependent Electronic Transport in Non‐Bulk‐Resistance‐Variation Nitrogen‐Doped Cr₂Ge₂Te₆ Phase‐Change Material

Hatayama

Ando

et al. 2020

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The electronic transport mechanism of the nitrogen‐doped Cr2Ge2Te6 (NCrGT) phase‐change material (PCM) is studied, showing almost zero resistivity variation upon phase transition. A similar low‐temperature variable‐range hopping (VRH) behavior in both the amorphous and crystalline phases of the NCrGT PCM is observed by measuring the temperature‐dependent resistivity. At high temperatures above 300 K, the conduction mechanism in the amorphous NCrGT is thermally activated band conduction, while the carrier transport in the crystalline NCrGT is still driven by VRH. Moreover, Hall property measurements reveal a thermally activated carrier in the amorphous NCrGT and mobility‐driven hopping conduction in the crystalline NCrGT at a high temperature range from 300 to 400 K. The conduction mechanism difference between the amorphous and crystalline NCrGT/tungsten (W) contacts is further investigated by measuring the temperature‐dependent I–V characteristics. The conduction in the amorphous NCrGT/W contact is dominated by thermionic‐field emission, while the transport mechanism through the crystalline NCrGT/W interface is controlled by the defect‐assisted tunneling current. Such noticeable conduction mechanism variation results in a large contact resistance contrast in a memory cell.

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Evolution of Phase-Change Memory for the Storage-Class Memory and Beyond

Cited by 96 publications

References 61 publications

Design of Phase‐Change Memory Using Apertureless Scanning Near‐Field Optical Microscopy in the Near‐Infrared Region

Design of Phase‐Change Memory Using Apertureless Scanning Near‐Field Optical Microscopy in the Near‐Infrared Region

Uncovering Phase Change Memory Energy Limits by Sub‐Nanosecond Probing of Power Dissipation Dynamics

Temperature‐Dependent Electronic Transport in Non‐Bulk‐Resistance‐Variation Nitrogen‐Doped Cr₂Ge₂Te₆ Phase‐Change Material

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Evolution of Phase-Change Memory for the Storage-Class Memory and Beyond

Cited by 96 publications

References 61 publications

Design of Phase‐Change Memory Using Apertureless Scanning Near‐Field Optical Microscopy in the Near‐Infrared Region

Design of Phase‐Change Memory Using Apertureless Scanning Near‐Field Optical Microscopy in the Near‐Infrared Region

Uncovering Phase Change Memory Energy Limits by Sub‐Nanosecond Probing of Power Dissipation Dynamics

Temperature‐Dependent Electronic Transport in Non‐Bulk‐Resistance‐Variation Nitrogen‐Doped Cr2Ge2Te6 Phase‐Change Material

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Temperature‐Dependent Electronic Transport in Non‐Bulk‐Resistance‐Variation Nitrogen‐Doped Cr₂Ge₂Te₆ Phase‐Change Material