Superlattice Phase Change Memory Fabrication Process for Back End of Line Devices

Ohyanagi, Takasumi; Takaura, N.; Kitamura, M.; Tai, Masayuki; Kinoshita, Masaharu; Akita, Katsushi; Morikawa, Takahiro; Tominaga, Junji

doi:10.7567/jjap.52.05ff01

Cited by 23 publications

(21 citation statements)

References 17 publications

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“…There have been a number of experimental demonstrations of the CSL memory567891011, but the switching mechanism is so far not fully defined at an atomic level. There have been several suggestions to explain how the atoms are manipulated, including charge injection12, electric field613, magnetic field6, thermal activation7 and polarization dependent optical control14.…”

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confidence: 99%

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Modeling of switching mechanism in GeSbTe chalcogenide superlattices

Robertson

2015

Sci Rep

100

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We study the switching process in chalcogenide superlattice (CSL) phase-change memory materials by describing the motion of an atomic layer between the low and high resistance states. Two models have been proposed by different groups based on high-resolution electron microscope images. Model 1 proposes a transition from Ferro to Inverted Petrov state. Model 2 proposes a switch between Petrov and Inverted Petrov states. For each case, we note that the main transition is actually a vertical displacement of a Ge layer through a Te layer, followed by a lateral motion of GeTe sublayer to the final, low energy structure. Through calculating energy barriers, the rate-determining step is the displacive transition.

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confidence: 99%

“…Some schematics are shown at an angle to suggest a relation to an umbrella-flip transition20. However, the so-called 4-fold Ge site in Ohyanagi9 actually breaks bonds under energy minimization to become the IP_1 state. F_0 is the only state that has primary and secondary Ge-Te bonds in sequence as in rhombohedral GeTe.…”

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confidence: 99%

Modeling of switching mechanism in GeSbTe chalcogenide superlattices

Robertson

2015

Sci Rep

100

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“…GeTe/Sb 2 Te 3 SL films were made by using two sputtering targets ( GeTe and Sb 2 Te 3 ) with multi-cathode physical vapor deposition (PVD). The SL in a crystalline state was fabricated when the sputtering temperature was higher than 190°C [7]. The deposition rate of the GeTe/Sb 2 Te 3 SL film in this work was 0.114 nm/s (Fig.…”

Section: A Physical Vapor Depositionmentioning

confidence: 97%

“…Figure 4 shows the etching rate for the thin films of Ge 2 Sb 2 Te 5 and GeTe/Sb 2 Te 3 SL. HBr/Ar gas mixtures were used for dry etching [7]. The etching rates for GeTe/Sb 2 Te 3 SL were lower than those for Ge 2 Sb 2 Te 5 because the byproducts produced by dry etching these two materials are different.…”

Section: B Etchingmentioning

confidence: 99%

Fabrication of topological-switching RAM (TRAM)

Takaura

Ohyanagi

Tai

et al. 2014

2014 14th Annual Non-Volatile Memory Technology Symposium (NVMTS)

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The fabrication of topological-switching randomaccess memory (TRAM), a new type of phase change memory, was investigated. The deposition and etching process technologies of a GeTe/Sb 2 Te 3 superlattice memory cell were developed and micro test structures of TRAM were fabricated. Analysis of the fabricated structures revealed that the electrical properties of TRAM were different from those of conventional phase change memory and the reset voltage of TRAM, 0.6 V, was less than that of PRAM, 1 V. The non-melting behaviors of resistance change in TRAM were clarified via thermal-conductivity measurements and device simulation.

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“…The detailed fabrication processes of the superlattice PCM were described in our previous paper. 18 We fabricated six types of superlattice PCM structures to clarify the region responsible for switching and to enable low-current switching. These six structures are listed in Table I and numbered (I) to (VI).…”

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confidence: 99%

Investigation of switching region in superlattice phase change memories

Ohyanagi

Takaura

2016

AIP Advances

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We investigated superlattice phase change memories (PCMs) to clarify which regions were responsible for switching. We observed atomic structures in a superlattice PCM film with a stack of GeTe / Sb2Te3 layers using atomically resolved EDX maps, and we found an intermixed region with three atom species of the Ge, Sb and Te around the top GeTe layer under the top electrode. We also found that a device with a GeTe layer on an Sb2Te3 layer without superlattice structure had the same switching characteristics as a device with a superlattice PCM, that had the same top GeTe layer. We developed and fabricated a modified superlattice PCM that attained ultra low Reset / Set currents under 60 μA.

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Superlattice Phase Change Memory Fabrication Process for Back End of Line Devices

Cited by 23 publications

References 17 publications

Modeling of switching mechanism in GeSbTe chalcogenide superlattices

Modeling of switching mechanism in GeSbTe chalcogenide superlattices

Fabrication of topological-switching RAM (TRAM)

Investigation of switching region in superlattice phase change memories

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