Co/Ni based p-MTJ stack for sub-20nm high density stand alone and high performance embedded memory application

Kar, Gouri Sankar; Kim, W.; Tahmasebi, T.; Swerts, Johan; Mertens, S.; Heylen, N.; Min, Tai

doi:10.1109/iedm.2014.7047080

Cited by 35 publications

(46 citation statements)

References 6 publications

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“…Note that for the [Co/Ni] on NiCr, the M s loss is large and the hysteresis loop becomes bow-tie like with coercivity (µ 0 H c ) increase (Fig.4(a)). The large µ 0 H c enables [Co/Ni] on NiCr seed to function as hard layer in MTJ stacks [12][13][14] . Fig.5 Commonly, highly fcc(111) textured [Co/Ni] films result in large PMA.…”

Section: Resultsmentioning

confidence: 99%

“…Besides, [Co/Ni] has been researched as alternative PMA material and has been employed in p-MTJ because of its high spin polarization and low Gilbert damping constant [8][9][10][11] . Also, [Co/Ni] has been incorporated in an ultrathin SAF [12][13][14] . Recently, the use of [Co/Ni] in the free layer material was proposed to enable free layers with high thermal stability needed at CD below 20nm 15 .…”

Section: Introductionmentioning

confidence: 99%

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Seed layer impact on structural and magnetic properties of [Co/Ni] multilayers with perpendicular magnetic anisotropy

Liu

Swerts

Devolder

et al. 2017

Journal of Applied Physics

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[Co/Ni] multilayers with perpendicular magnetic anisotropy (PMA) have been researched and applied in various spintronic applications. Typically the seed layer material is studied to provide the desired facecentered cubic (fcc) texture to the [Co/Ni] to obtain PMA. The integration of [Co/Ni] in back-end-of-line (BEOL) processes also requires the PMA to survive post-annealing. In this paper, the impact of NiCr, Pt, Ru, and Ta seed layers on the structural and magnetic properties of [Co(0.3 nm)/Ni(0.6 nm)] multilayers is investigated before and after annealing. The multilayers were deposited in-situ on different seeds via physical vapor deposition at room temperature. The as-deposited [Co/Ni] films show the required fcc(111) texture on all seeds, but PMA is only observed on Pt and Ru. In-plane magnetic anisotropy (IMA) is obtained on NiCr and Ta seeds, which is attributed to strain-induced PMA loss. PMA is maintained on all seeds after post-annealing up to 400 • C. The largest effective perpendicular anisotropy energy (K eff U ≈ 2 × 10 5 J/m 3 ) after annealing is achieved on NiCr seed. The evolution of PMA upon annealing cannot be explained by further crystallization during annealing or strain-induced PMA, nor can the observed magnetization loss and the increased damping after annealing. Here we identify the diffusion of the non-magnetic materials from the seed into [Co/Ni] as the major driver of the changes in the magnetic properties. By selecting the seed and post-annealing temperature, the [Co/Ni] can be tuned in a broad range for both PMA and damping.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Seed layer impact on structural and magnetic properties of [Co/Ni] multilayers with perpendicular magnetic anisotropy

Liu

Swerts

Devolder

et al. 2017

Journal of Applied Physics

Self Cite

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“…STT-RAM and RRAM are good candidates for implementing this type of hybrid multibit SRAM as recent reports indicate that these memories are close to commercial availability [4][5][6][7][8][9]. In fact, the differential design of our memory cell, e.g.…”

Section: Multibit Hybrid Sram Cellsmentioning

confidence: 99%

“…Fortunately most of the candidate memories fit this requirement. Both STT-RAM and RRAM memories have projected cell size of ~6F 2 , much smaller than the area (60-120 F 2 ) of the traditional SRAM cell [4][5][6][7][8][9]. Similarly embedded DRAM cells can be as small as 1/6 of the equivalent SRAM cells [10,11].…”

Section: Multibit Hybrid Sram Cellsmentioning

confidence: 99%

Nonvolatile multibit SRAM, bit level caching, and multi-context computing for IoT

2015

2015 15th Non-Volatile Memory Technology Symposium (NVMTS)

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We propose a new memory hierarchy for energy conscious internet of things (IoT) integrated circuits. In this scheme a new type of SRAM cell -hybrid of SRAM/DRAM or SRAM/NVM memory -that is capable of storing multiple bits are used to bring caching to the bit level, near processor cores. This new scheme is expected to have energy efficiency advantage over traditional memory hierarchy for multi-context computation, especially suitable for many IoT applications.

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“…[13][14][15] Notably, the TMR ratio decreases rapidly as the BEOL temperature increases, so a TMR ratio of 4100% at the BEOL temperature of 400°C is extremely difficult to achieve. [16][17][18] In this study, we investigated the effect of nanoscale-thick bridging and capping materials ((Tantalum (Ta) or Tungsten (W)) on the TMR ratio at the BEOL temperature of 400°C for the p-MTJ spinvalve with a top Co 2 Fe 6 B 2 free layer. A bridging layer ferro-couples the Co 2 Fe 6 B 2 pinned layer with an upper synthetic anti-ferromagnetic (SyAF) layer in the p-MTJ spin-valve, and a capping layer is sputtered on the Co 2 Fe 6 B 2 free layer, as shown in Figure 1a and b.…”

Section: Introductionmentioning

confidence: 99%

Perpendicular magnetic tunnel junction (p-MTJ) spin-valves designed with a top Co2Fe6B2 free layer and a nanoscale-thick tungsten bridging and capping layer

2016

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Recently, p-MTJ spin-valves with top Co 2 Fe 6 B 2 free layers have been widely studied. They potentially experience crystallinity degradation in the face-centered-cubic (fcc) structure of the MgO tunneling barrier as a result of the diffusion of Ta atoms and a significant amount of Fe atoms from the Co 2 Fe 6 B 2 free and pinned layers. A new design of the p-MTJ spin-valve using a nanoscale-thick W bridging and capping layer demonstrated the absence of significant crystallinity degradation in the fcc structure and showed a limited diffusion of Fe atoms, thus achieving a TMR ratio of~143% at an ex-situ annealing temperature of 400°C.

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Co/Ni based p-MTJ stack for sub-20nm high density stand alone and high performance embedded memory application

Abstract: Excellent tunnel magneto resistance (TMR

Cited by 35 publications

References 6 publications

Seed layer impact on structural and magnetic properties of [Co/Ni] multilayers with perpendicular magnetic anisotropy

Seed layer impact on structural and magnetic properties of [Co/Ni] multilayers with perpendicular magnetic anisotropy

Nonvolatile multibit SRAM, bit level caching, and multi-context computing for IoT

Perpendicular magnetic tunnel junction (p-MTJ) spin-valves designed with a top Co2Fe6B2 free layer and a nanoscale-thick tungsten bridging and capping layer

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