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Phase-change properties of GeSbTe thin films deposited by plasma-enchanced atomic layer depositon.

Song S, Yao D, Song Z, Gao L, Zhang Z, Li L, Shen L, Wu L, Liu B, Cheng Y, Feng S - Nanoscale Res Lett (2015)

Bottom Line: Phase-change access memory (PCM) appears to be the strongest candidate for next-generation high-density nonvolatile memory.Compared with GST-based device, GeSb8Te-based device exhibits a faster switching speed and reduced reset voltage, which is attributed to the growth-dominated crystallization mechanism of the Sb-rich GeSb8Te films.These results show that ALD is an attractive method for preparation of phase-change materials.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai, 200050 China.

ABSTRACT
Phase-change access memory (PCM) appears to be the strongest candidate for next-generation high-density nonvolatile memory. The fabrication of ultrahigh-density PCM depends heavily on the thin-film growth technique for the phase-changing chalcogenide material. In this study, Ge2Sb2Te5 (GST) and GeSb8Te thin films were deposited by plasma-enhanced atomic layer deposition (ALD) method using Ge [(CH3)2 N]4, Sb [(CH3)2 N]3, Te(C4H9)2 as precursors and plasma-activated H2 gas as reducing agent of the metallorganic precursors. Compared with GST-based device, GeSb8Te-based device exhibits a faster switching speed and reduced reset voltage, which is attributed to the growth-dominated crystallization mechanism of the Sb-rich GeSb8Te films. These results show that ALD is an attractive method for preparation of phase-change materials.

No MeSH data available.


Resistance voltage characteristics of PCM cell ((a) ALD-deposited GST, (b) PVD-deposited GST films by different voltage pulse widths).
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Fig4: Resistance voltage characteristics of PCM cell ((a) ALD-deposited GST, (b) PVD-deposited GST films by different voltage pulse widths).

Mentions: The phase transition of PCM cell can be characterized from the relation between the cell resistance and the corresponding amplitude of voltage pulse or current pulse (so-called R-V or R-I curve). In order to test the electrical phase-change ability of the ALD-deposited GST films, the SET and RESET operations of the PCM cells based on the ALD-deposited GST materials are realized by a stimulated voltage pulse with different pulse widths, as presented in Figure 4a. As indicated in Figure 4a, the resistance dramatically increases by two orders of magnitude at the reset voltage of around 6.7 V. The R-V curves of the PCM cells using PVD-deposited GST materials are also shown in Figure 4b. For the device based on PVD-deposited GST films with the identical cell architecture, the reset voltage is around 3.6 V, which is lower than that of the device based on ALD-deposited GST. It also can be seen from Figure 4b that a 200-ns-wide voltage pulse is able to set the cells based on PVD-deposited GST materials with the sensing margin (RRESET/RSET) of more than two orders of magnitude. For the device based on ALD-deposited GST, it is noted that a 500-ns-wide pulse fails to set the cell and a pulse width of 800 ns is insufficient for a complete set programming, suggesting that ALD process indeed leads to a slower crystallization process thus longer write time for the set operation. The measured set speed of the ALD-deposited GST films is slower than that of PVD-deposited GST films, which is supposedly due to the impurities. Especially N, C impurities in ALD-deposited GST films are known to increase the crystallization temperature and reduce the crystallization speed of the GST films [17,18].Figure 4


Phase-change properties of GeSbTe thin films deposited by plasma-enchanced atomic layer depositon.

Song S, Yao D, Song Z, Gao L, Zhang Z, Li L, Shen L, Wu L, Liu B, Cheng Y, Feng S - Nanoscale Res Lett (2015)

Resistance voltage characteristics of PCM cell ((a) ALD-deposited GST, (b) PVD-deposited GST films by different voltage pulse widths).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385138&req=5

Fig4: Resistance voltage characteristics of PCM cell ((a) ALD-deposited GST, (b) PVD-deposited GST films by different voltage pulse widths).
Mentions: The phase transition of PCM cell can be characterized from the relation between the cell resistance and the corresponding amplitude of voltage pulse or current pulse (so-called R-V or R-I curve). In order to test the electrical phase-change ability of the ALD-deposited GST films, the SET and RESET operations of the PCM cells based on the ALD-deposited GST materials are realized by a stimulated voltage pulse with different pulse widths, as presented in Figure 4a. As indicated in Figure 4a, the resistance dramatically increases by two orders of magnitude at the reset voltage of around 6.7 V. The R-V curves of the PCM cells using PVD-deposited GST materials are also shown in Figure 4b. For the device based on PVD-deposited GST films with the identical cell architecture, the reset voltage is around 3.6 V, which is lower than that of the device based on ALD-deposited GST. It also can be seen from Figure 4b that a 200-ns-wide voltage pulse is able to set the cells based on PVD-deposited GST materials with the sensing margin (RRESET/RSET) of more than two orders of magnitude. For the device based on ALD-deposited GST, it is noted that a 500-ns-wide pulse fails to set the cell and a pulse width of 800 ns is insufficient for a complete set programming, suggesting that ALD process indeed leads to a slower crystallization process thus longer write time for the set operation. The measured set speed of the ALD-deposited GST films is slower than that of PVD-deposited GST films, which is supposedly due to the impurities. Especially N, C impurities in ALD-deposited GST films are known to increase the crystallization temperature and reduce the crystallization speed of the GST films [17,18].Figure 4

Bottom Line: Phase-change access memory (PCM) appears to be the strongest candidate for next-generation high-density nonvolatile memory.Compared with GST-based device, GeSb8Te-based device exhibits a faster switching speed and reduced reset voltage, which is attributed to the growth-dominated crystallization mechanism of the Sb-rich GeSb8Te films.These results show that ALD is an attractive method for preparation of phase-change materials.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai, 200050 China.

ABSTRACT
Phase-change access memory (PCM) appears to be the strongest candidate for next-generation high-density nonvolatile memory. The fabrication of ultrahigh-density PCM depends heavily on the thin-film growth technique for the phase-changing chalcogenide material. In this study, Ge2Sb2Te5 (GST) and GeSb8Te thin films were deposited by plasma-enhanced atomic layer deposition (ALD) method using Ge [(CH3)2 N]4, Sb [(CH3)2 N]3, Te(C4H9)2 as precursors and plasma-activated H2 gas as reducing agent of the metallorganic precursors. Compared with GST-based device, GeSb8Te-based device exhibits a faster switching speed and reduced reset voltage, which is attributed to the growth-dominated crystallization mechanism of the Sb-rich GeSb8Te films. These results show that ALD is an attractive method for preparation of phase-change materials.

No MeSH data available.