Electrothermal and phase-change dynamics in chalcogenide-based memories

Lacaita, A.L.; Redaelli, A.; Ielmini, Daniele; Pellizzer, F.; Pirovano, A.; Benvenuti, A.; Bez, R.

doi:10.1109/iedm.2004.1419330

Cited by 77 publications

(48 citation statements)

References 5 publications

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“…Studies of the low-field cell resistance and threshold voltage as a function of the amorphous fraction, i.e., the effective amorphous layer thickness normalized to its maximum value, are also presented. The results show a good agreement between the measurements and the trap-limited transport model and also reinforce the hypothesis of a series distribution of amorphous and crystalline phases in the volume of a programmed phasechange element [10][11][12]. …”

Section: Introductionsupporting

confidence: 79%

Estimation of amorphous fraction in multilevel phase-change memory cells

Παπανδρεου

Pantazi

Sebastian

et al. 2010

Solid-State Electronics

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Section: Introductionsupporting

confidence: 79%

Estimation of amorphous fraction in multilevel phase-change memory cells

Παπανδρεου

Pantazi

Sebastian

et al. 2010

Solid-State Electronics

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“…Lacaita et al 18 have observed a linear relation between the amorphous resistance and threshold voltage across a large range (more than an order of magnitude difference) in Fig. 6(a)].…”

Section: Threshold Voltage and Resistance As A Function Of Pulse Hmentioning

confidence: 96%

“…2,34 Furthermore, the extrapolated threshold voltage at zero amorphous mark size is finite and also material dependent. 9,11,18,34 The phenomenological threshold voltage is therefore related to both quantities and the length of the amorphous mark. A decrease of both the crystallization temperature and threshold voltage accompanied by a decrease of the amorphous resistivity of almost an order of magnitude was observed for increasing the Sb content in Sb x Te (1Àx) alloys (x !…”

Section: Temperature and Activation Energy Of Crystallizationmentioning

confidence: 99%

Evolution of cell resistance, threshold voltage and crystallization temperature during cycling of line-cell phase-change random access memory

Oosthoek

Attenborough

Hurkx

et al. 2011

Journal of Applied Physics

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Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Doped SbTe phase change (PRAM) line cells produced by e-beam lithography were cycled 100 million times. During cell cycling the evolution of many cell properties were monitored, in particular the crystalline and amorphous resistance, amorphous resistance drift exponent, time-dependent threshold voltage, threshold voltage as a function of RESET pulse height, crystallization temperature, and activation energy of crystal growth. The power of the present approach is that all these properties were measured simultaneously during the life of single cells. The evolution of the cell properties can be summarized by (i) an initialization phase characterized by settle-in effect of the material surrounding the programmable region, (ii) a usable life phase where initially the cell properties remain fairly constant until after $5 Â 10 5 cycles decomposition of the programmed region caused degradation of the cell properties, and (iii) finally an end of life phase where the cell is stuck in the SET state after typically 10 8 cycles. Although generally the threshold voltage is directly related to the amorphous resistance it was found that during cycling this relation is not constant but evolved as well. Instead, the crystallization temperature could be linked to the threshold voltage throughout the complete life cycle of the cell which could lead to new insights to the nature of the threshold event.

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“…Following the original work of Ovshinsky 1 , the reversible switching phenomena observed in disordered semiconductors has attracted substantial theoretical 2,3,4,5,6,7 and experimental 8,9,10,11,12,13 efforts targeted at gaining a deep understanding of the physical principles that govern the switching dynamics, and also learning how to control and optimize the power requirements coupled with characteristic switching timescales. Dramatic and ultra-fast (nanosecond scale) changes in the physical properties such as electrical resistivity and optical reflectivity upon amorphization or crystallization makes chalcogenides ideal potential candidates for a universal non-volatile memory device, especially if, the device switching characteristics are highly scalable to nanometer dimensions.…”

Section: Introductionmentioning

confidence: 99%

Electrical switching dynamics in circular and rectangular Ge2Sb2Te5 nanopillar phase change memory devices

Ozatay

Stipe

Katine

et al. 2008

Journal of Applied Physics

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We have measured the critical phase change conditions induced by electrical pulses in Ge 2 Sb 2 Te 5 nanopillar phase change memory devices by constructing a comprehensive resistance map as a function of pulse parameters (width, amplitude and trailing edge). Our measurements reveal that the heating scheme and the details of the contact geometry play the dominant role in determining the final phase composition of the device such that a non-uniform heating scheme using rectangular contacts promotes partial amorphization/crystallization for a wide range of pulse parameters enabling multiple resistance levels for data storage applications. Furthermore we find that fluctuations in the snap-back voltage and set/reset resistances in repeated switching experiments are related to the details of the current distribution such that a uniform current injection geometry (i.e. circular contact) favors more reproducible switching parameters. This shows that possible geometrical defects in nanoscale phase change memory devices may play an essential role in the performance of the smallest possible devices through modification of the exact current distribution in the active chalcogenide layer. We present a three-dimensional finite element model of the electro-thermal physics to provide insights into the underlying physical mechanisms of the switching dynamics as well as to quantitatively account for the scaling behaviour of the switching currents in both circular and rectangular contact geometries. The calculated temporal evolution of the heat distribution within the pulse duration shows distinct features in rectangular contacts providing evidence for locally hot spots at the sharp corners of the current injection site due to current crowding effects leading to the observed behaviour.

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Electrothermal and phase-change dynamics in chalcogenide-based memories

Cited by 77 publications

References 5 publications

Estimation of amorphous fraction in multilevel phase-change memory cells

Estimation of amorphous fraction in multilevel phase-change memory cells

Evolution of cell resistance, threshold voltage and crystallization temperature during cycling of line-cell phase-change random access memory

Electrical switching dynamics in circular and rectangular Ge2Sb2Te5 nanopillar phase change memory devices

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