Crystallization behavior of N -doped Ge-rich GST thin films and nanostructures: An in-situ synchrotron X-ray diffraction study

Thomas, Olivier; Mocuta, Cristian; Putero, Magali; Richard, M.-I.; Boivin, P.; Arnaud, F.

doi:10.1016/j.mee.2021.111573

Cited by 11 publications

(16 citation statements)

References 21 publications

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“…Increasing the Ge content in the GST alloys shows an increase in the crystallization temperature, promoting high data retention and endurance [ 10 , 21 , 22 ]. Moreover, in addition to Ge enriching, nitrogen doping of Ge-rich GST alloys has also been studied for increased thermal stability and higher crystallization temperatures, which are attractive for future memory devices [ 9 , 23 , 24 ].…”

Section: Introductionmentioning

confidence: 99%

Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films

et al. 2022

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Integration of the prototypical GeSbTe (GST) ternary alloys, especially on the GeTe-Sb2Te3 tie-line, into non-volatile memory and nanophotonic devices is a relatively mature field of study. Nevertheless, the search for the next best active material with outstanding properties is still ongoing. This search is relatively crucial for embedded memory applications where the crystallization temperature of the active material has to be higher to surpass the soldering threshold. Increasing the Ge content in the GST alloys seems promising due to the associated higher crystallization temperatures. However, homogeneous Ge-rich GST in the as-deposited condition is thermodynamically unstable, and phase separation upon annealing is unavoidable. This phase separation reduces endurance and is detrimental in fully integrating the alloys into active memory devices. This work investigated the phase separation of Ge-rich GST alloys, specifically Ge5Sb2Te3 or GST523, into multiple (meta)stable phases at different length scales in melt-quenched bulk and annealed thin film. Electron microscopy-based techniques were used in our work for chemical mapping and elemental composition analysis to show the formation of multiple phases. Our results show the formation of alloys such as GST213 and GST324 in all length scales. Furthermore, the alloy compositions and the observed phase separation pathways agree to a large extent with theoretical results from density functional theory calculations.

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Section: Introductionmentioning

confidence: 99%

Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films

et al. 2022

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“…5) In patterned and metallized specimens a) Ge and Ge 2 Sb 2 Te 5 preexist (explainable by thermal pretreatments) and b) the onsets of crystallization are shifted for both phases to much higher temperatures (approximately 60AE10 ∘ C). As that T-shift is not observed in patterned samples with no metallization ( [7]) and hydrogen treatment appears to lower the crystallization onsets, the conclusion is drawn that preprocessing steps or stress induced by the metallization layers might be the reason for the strong shift of T x .…”

Section: Pmu Pmt D 500 C 500 Cmentioning

confidence: 93%

“…This composition optimized Ge-rich material within the Ge-Sb-Te ternary system will be named GGST herein. Previous studies on 50 nm thin films have shown [7] that the crystallization proceeds in two steps with Ge crystallization preceding the crystallization To passivate Si À SiO 2 dangling bonds, metal-oxide-semiconductor field-effect transistor devices are usually treated with hydrogen. Herein, the effects of such a treatment on the crystallization behavior on N-doped, Ge-rich Ge 2 Sb 2 Te 5 phasechange materials for memory applications are investigated using synchrotron X-ray diffraction (XRD) in situ during heat treatment.…”

Section: Introductionmentioning

confidence: 99%

“…An increased N-content reduces mechanical stresses related to crystallization, and strongly reduces Ge crystallization, probably by the formation of a GeN x compound. [7][8][9][10][11] It is state of the art to reduce the density of interface states in metal-oxide-semiconductor (MOS) transistors, resulting in, e.g., neutralized Si À SiO 2 dangling bonds, by hydrogen treatment in devices. [12] As H is known to be a very fast diffuser, it is expected that it will reach the PCM.…”

Section: Introductionmentioning

confidence: 99%

“…This composition optimized Ge‐rich material within the Ge–Sb–Te ternary system will be named GGST herein. Previous studies on 50 nm thin films have shown [ 7 ] that the crystallization proceeds in two steps with Ge crystallization preceding the crystallization of cubic, metastable

{Ge}_{2} {Sb}_{2} {Te}_{5}

). [ 1 ] Another variable that allows tuning the properties of GST‐based PCMs is N‐doping.…”

Section: Introductionmentioning

confidence: 99%

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An In Situ Synchrotron X‐Ray Diffraction Study on the Influence of Hydrogen on the Crystallization of Ge‐Rich Ge2Sb2Te5

Hans

Mocuta

Marie-Ingrid

et al. 2022

Physica Rapid Research Ltrs

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To passivate Si − SiO 2 dangling bonds, metal–oxide–semiconductor field‐effect transistor devices are usually treated with hydrogen. Herein, the effects of such a treatment on the crystallization behavior on N‐doped, Ge‐rich Ge 2 Sb 2 Te 5 phase‐change materials for memory applications are investigated using synchrotron X‐ray diffraction (XRD) in situ during heat treatment. Uniform thin films, and laterally confined, metallized ones (simulating devices of different complexity) of initially amorphous N‐doped GGST are investigated. The specimens are heated up to 450–500 °C at a rate of 2 °C/min. Some of the specimens are treated with H/D; the equivalent untreated specimen is investigated for each of them. Crystallization onsets are estimated by quantification of the crystallized quantity during material transformation from the XRD patterns. In thin films, the hydrogen treatment results in lowered crystallization temperatures of the emerging cubic, metastable Ge 2 Sb 2 Te 5 phase. Its trigonal, thermodynamically stable polymorph always forms, but its crystallization temperature is unchanged. Patterned and metallized samples show less differences, are strongly textured, and no trigonal phase is observed. It is shown that certain questions might only be answered at large‐scale facilities where high energy photons are available at high flux, allowing data acquisition during the annealing process with a temperature resolution sufficient for a fine description of the sample transformation.

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Advanced Metrics for Quantification of By‐Process Segregation beyond Ternary Systems

Petroni

Patelmo

Serafini

et al. 2023

Physica Rapid Research Ltrs

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Ge‐rich GST (GGST) alloys have been shown to fulfill the tough temperature specifications required by automotive applications. Thus, they are the most promising materials for the embedded phase‐change memory market. In this respect, the characterization of the material properties once patterned and fully integrated is instrumental to improve the process and optimize the device performance. A description of the material behavior through a realistic sequence of process steps is still missing. Herein, a statistical‐based methodology capable to extract advanced metrics for the quantification of by‐process segregation beyond ternary systems is presented, capable to quantify thermal evolution of any out‐of‐stoichiometry and segregated material beyond ternary systems. The methodology to study the physical behavior of GGST as a function of a typical back‐end‐of‐line (BEOL) process is exploited, providing a further comparison between three different BEOL‐ended GGST.

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Crystallization behavior of N -doped Ge-rich GST thin films and nanostructures: An in-situ synchrotron X-ray diffraction study

Cited by 11 publications

References 21 publications

Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films

Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films

An In Situ Synchrotron X‐Ray Diffraction Study on the Influence of Hydrogen on the Crystallization of Ge‐Rich Ge2Sb2Te5

Advanced Metrics for Quantification of By‐Process Segregation beyond Ternary Systems

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