Scaling analysis of phase-change memory technology

Pirovano, A.; Lacaita, A.L.; Benvenuti, A.; Pellizzer, F.; Hudgens, S. J.; Bez, R.

doi:10.1109/iedm.2003.1269376

Cited by 236 publications

(179 citation statements)

References 3 publications

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“…[4] The crystalline phase is more reflective and up to three orders of magnitude more electrically conductive than the amorphous phase. [1] These differences in the physical properties between phases, in addition to the ability to retain either phase state for a long time at ambient temperatures, [5] have been utilized in technologies such as rewritable optical data storage (DVD-RW, Blu-ray RW) and nonvolatile electronic phase-change memories…”

Section: Doi: 101002/aelm201700079mentioning

confidence: 99%

Mixed‐Mode Electro‐Optical Operation of Ge₂Sb₂Te₅ Nanoscale Crossbar Devices

Rodriguez-Hernandez

Hosseini

Rı́os

et al. 2017

Adv Elect Materials

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The use of phase‐change materials for a range of exciting new optoelectronic applications from artificial retinas to ultrahigh‐resolution displays requires a thorough understanding of how these materials perform under a combination of optical and electrical stimuli. This study reports for the first time the complex link between the electronic and optical properties in real‐world crossbar nanoscale devices constructed by confining a thin layer of Ge2Sb2Te5 between transparent indium tin oxide electrodes, forming an optical nanocavity. A novel proof‐of‐concept device that can be operated by a combination of optical and electrical stimuli is presented, leading the way for the development of further applications based on mixed‐mode electro‐optical operation.

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Section: Doi: 101002/aelm201700079mentioning

confidence: 99%

Mixed‐Mode Electro‐Optical Operation of Ge₂Sb₂Te₅ Nanoscale Crossbar Devices

Rodriguez-Hernandez

Hosseini

Rı́os

et al. 2017

Adv Elect Materials

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“…In contrast to other memory technologies, PCRAM is the most preferred due to its nonvolatile nature, high scalability, faster read/write operations and high endurance. [3][4][5] However, in spite of its many advantages, the high programming current (>0.1mA) becomes a limiting factor with respect to other memory technology, where the Joule heating must be localized to bit volume.…”

Section: Introductionmentioning

confidence: 99%

The role of atomic vacancies on phonon confinement in α-GeTe

Kalra

Murugavel

2015

AIP Advances

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Atomic defects and their dynamics play a vital role in controlling the behavior of non-volatile phase change memory materials used in advanced optical storage devices. Synthesis and structural analysis by XRD and Raman spectroscopy on α-GeTe single crystal with different sizes are reported. The spectroscopic measurements on micron and nano sized α-GeTe single crystal reveal the evolution of phonon confinement with crystal sizes of few hundred nanometers. The characteristic vibrational modes of bulk α-GeTe structure are found to downshift and asymmetrically broaden to lower frequency with decreasing the single crystal size. We attribute the observed downshift of Raman lines in α-GeTe is largely due to the presence of high concentration of atomic vacancies. The crystal size and temperature dependent Raman spectra provide explicitly the dynamics of vacancies on optical phonon confinement in α-GeTe structure. Thus, the observed large concentration of vacancies and their size dependency might influence the phase change phenomenon in GeTe based alloys.

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“…Although the k value of GST shows a relatively small variation, in the range of 0.2-0.5 W m − 1 K − 1 , 21 the σ value varies drastically with the crystallinity of GST, varying from 0.5 to 2770 S m − 1 . 21 Thus, the crystallinity-dependent electrical conductivity, σ, of GST is the major factor that determines the temperature distribution and the maximum temperature (T max ) in the active switching volume. …”

Section: Characterizationmentioning

confidence: 99%

“…The cell geometry constructed for FEM is detailed in Figure 2a, and the material properties are summarized in Table 1. [21][22][23] According to Equation (1), the amount of heat generated within the switching volume of PCRAM is predominantly determined by the actual σ and k values of GST. Although the k value of GST shows a relatively small variation, in the range of 0.2-0.5 W m − 1 K − 1 , 21 the σ value varies drastically with the crystallinity of GST, varying from 0.5 to 2770 S m − 1 .…”

Section: Characterizationmentioning

confidence: 99%

Microstructure-dependent DC set switching behaviors of Ge–Sb–Te-based phase-change random access memory devices accessed by in situ TEM

et al. 2015

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Phase-change random access memory (PCRAM) is one of the most promising nonvolatile memory devices. However, inability to secure consistent and reliable switching operations in nanometer-scale programing volumes limits its practical use for highdensity applications. Here, we report in situ transmission electron microscopy investigation of the DC set switching of Ge-Sb-Te (GST)-based vertical PCRAM cells. We demonstrate that the microstructure of GST, particularly the passive component surrounding the dome-shaped active switching volume, plays a critical role in determining the local temperature distribution and is therefore responsible for inconsistent cell-to-cell switching behaviors. As demonstrated by a PCRAM cell with a highly crystallized GST matrix, the excessive Joule heat can cause melting and evaporation of the switching volume, resulting in device failure. The failure occurred via two-step void formation due to accelerated phase separation in the molten GST by the polaritydependent atomic migration of constituent elements. The presented real-time observations contribute to the understanding of inconsistent switching and premature failure of GST-based PCRAM cells and can guide future design of reliable PCRAM. INTRODUCTIONPhase-change random access memory (PCRAM) devices store and erase information by utilizing a large resistivity difference between the crystalline and amorphous states of chalcogenide materials. 1 Among various chalcogenide materials, the Ge-Sb-Te (GST) alloy system is currently considered the most promising candidate material for PCRAM owing to its fast and reversible phase-transition capability, in both the amorphous-to-crystalline (set) and the reverse crystallineto-amorphous (reset) switching. 2,3 Moreover, the set switching of GST occurs through an abrupt increase in the current density at a critical electric field, which is known as threshold switching. 1,4 The threshold switching provides local Joule heat and thereby facilitates the crystallization process at a relatively low electric field, ranging from 30 to 50 V μm − 1 . 5,6 Many modern PCRAM cell designs adopt a nanometer-scale hemispherical or cylindrical shape for programing volume to increase the cell density and reduce the operation power. 7 In such device structures, only a portion of the programing volume makes direct contact with a heater electrode, and the other sides are surrounded by passive GST that remains in the crystalline state and acts as an electrical conductivity path during the set and reset switching. One of the critical reliability issues related to these cell structures is the compositional change, or phase separation, caused by electric field-

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Scaling analysis of phase-change memory technology

Cited by 236 publications

References 3 publications

Mixed‐Mode Electro‐Optical Operation of Ge₂Sb₂Te₅ Nanoscale Crossbar Devices

Mixed‐Mode Electro‐Optical Operation of Ge₂Sb₂Te₅ Nanoscale Crossbar Devices

The role of atomic vacancies on phonon confinement in α-GeTe

Microstructure-dependent DC set switching behaviors of Ge–Sb–Te-based phase-change random access memory devices accessed by in situ TEM

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Scaling analysis of phase-change memory technology

Cited by 236 publications

References 3 publications

Mixed‐Mode Electro‐Optical Operation of Ge2Sb2Te5 Nanoscale Crossbar Devices

Mixed‐Mode Electro‐Optical Operation of Ge2Sb2Te5 Nanoscale Crossbar Devices

The role of atomic vacancies on phonon confinement in α-GeTe

Microstructure-dependent DC set switching behaviors of Ge–Sb–Te-based phase-change random access memory devices accessed by in situ TEM

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Mixed‐Mode Electro‐Optical Operation of Ge₂Sb₂Te₅ Nanoscale Crossbar Devices

Mixed‐Mode Electro‐Optical Operation of Ge₂Sb₂Te₅ Nanoscale Crossbar Devices