Flat-surface-assisted and self-regulated oxidation resistance of Cu(111)

Kim, Su Jae; Kim, Yong In; Lamichhane, Bipin; Lee, Yousil; Cho, Chae Ryong; Cheon, M.; Kim, Jong Chan; Jeong, Hu Young; Ha, Taewoo; Kim, Jungdae; Lee, Young Hee; Kim, Seong‐Gon; Kim, Young Min; Jeong, Se–Young

doi:10.1038/s41586-021-04375-5

Cited by 70 publications

(63 citation statements)

References 43 publications

(39 reference statements)

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“…Approximate 50% of 〈111〉 orientation was observed by orientation imaging microscopy (OIM), as illustrated in Fig. 2 c. Note that the roughness of the joints also plays a key role on bonding quality and oxidation resistance 36 , 37 . Thus, we planarized the Cu joints using CMP.…”

Section: Resultsmentioning

confidence: 94%

Enhancement of fatigue resistance by recrystallization and grain growth to eliminate bonding interfaces in Cu–Cu joints

Ong

Tran

Lan

et al. 2022

Sci Rep

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Cu–Cu joints have been adopted for ultra-high density of packaging for high-end devices. However, cracks may form and propagate along the bonding interfaces during fatigue tests. In this study, Cu–Cu joints were fabricated at 300 °C by bonding 〈111〉-oriented nanotwinned Cu microbumps with 30 μm in diameter. After temperature cycling tests (TCTs) for 1000 cycles, cracks were observed to propagate along the original bonding interface. However, with additional 300 °C-1 h annealing, recrystallization and grain growth took place in the joints and thus the bonding interfaces were eliminated. The fatigue resistance of the Cu–Cu joints is enhanced significantly. Failure analysis shows that cracks propagation was retarded in the Cu joints without the original bonding interface, and the electrical resistance of the joints did not increase even after 1000 cycles of TCT. Finite element analysis was carried to simulate the stress distribution during the TCTs. The results can be correlated to the failure mechanism observed by experimental failure analysis.

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Section: Resultsmentioning

confidence: 94%

Enhancement of fatigue resistance by recrystallization and grain growth to eliminate bonding interfaces in Cu–Cu joints

Ong

Tran

Lan

et al. 2022

Sci Rep

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“…Microstrain analysis was thus performed on the HRTEM image by geometric phase analysis (GPA). 33,34 The variation of strain was analyzed along the [11−1] and the [−200] directions (Fig. 4(f)).…”

Section: Resultsmentioning

confidence: 99%

Atomic-level flatness on oxygen-free copper surface in lapping and chemical mechanical polishing

et al. 2022

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“…Ideally, a single-crystal thin film, such as that grown homoepitaxially, can be obtained via heteroepitaxy near the surface when the thickness exceeds ~80 nm. Homoepitaxy-like heteroepitaxy of a Cu thin film on a hetero substrate is only possible when it is deposited by ASE, and the long-distance periodicity by the calculation of extended atomic distance mismatch 21 is considered.…”

Section: Coherent Consolidation Into a Coplanar Layermentioning

confidence: 99%

Coherent consolidation of trillions of nucleations for mono-atom step-level flat surfaces

Seo

Kim

et al. 2022

Preprint

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Constructing a mono-atom step-level ultra-flat material surface is challenging, especially for thin films, because it is prohibitively difficult for trillions of clusters to coherently merge. Even though a rough metal surface, as well as the scattering of carriers at grain boundaries, limits electron transport and obscures their intrinsic properties, the importance of the flat surface has not been emphasised sufficiently. In this study, we describe in detail the initial growth of copper thin films required for mono-atom step-level flat surfaces (MSFSs). Deposition using atomic sputtering epitaxy leads to the coherent merging of trillions of islands into a coplanar layer, eventually forming an MSFS, for which the key factor is suggested to be the individual deposition of single atoms.Theoretical calculations support that single sputtered atoms ensure the formation of highly aligned nanodroplets and help them to merge into a coplanar layer. The realisation of the ultra-flat surfaces is expected to greatly assist efforts to improve quantum behaviour by increasing the coherency of electrons. Keywords: Coherent merging; coplanar layer; initial growth stages; mono-atom step-level flat surface; single-crystal thin films Ultrathin metal films are indispensable in modern electronics and nanotechnology 1-3 . During the past few decades, conventional metals have been studied extensively because the performance of metal-based devices is intimately related to their physical properties. [4][5][6] Efforts to produce single-crystal (SC) copper (Cu) from Cu foil have been driven by competition 7,8 and interest in their nanocrystalline nature and potential applications in large two-dimensional (2D) components consisting of materials such as graphene and hexagonal boron nitride (h-BN). [9][10][11] However, despite the importance of metal thin-film flatness, there have been few reports because it is challenging to control flatness. Since the contact between the metal electrode and the semiconductor material decisively affects the properties of electronic and optoelectronic devices, 12,13 a flat metal surface is proposed as a good solution to reduce contact resistance. The motion of electrons without scattering at surfaces and grain boundaries can also affect the carrier transport properties. 14 Single-crystal Cu thin films (SCCFs) on sapphire have recently been reported, and the formation of twin boundaries (TBs) have been investigated intensively. [15][16][17] Two orientations (ORs) adjacent to a TB are rotated by a certain angle in-plane and satisfy the symmetry operation exactly, while two ORs adjacent to a grain boundary (GB) are tilted both in out-of-plane and in-plane directions. However, in view of electronic motion, a much clearer distinction between TB and GB must be followed by precise microscopic analysis. Twin

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Flat-surface-assisted and self-regulated oxidation resistance of Cu(111)

Cited by 70 publications

References 43 publications

Enhancement of fatigue resistance by recrystallization and grain growth to eliminate bonding interfaces in Cu–Cu joints

Enhancement of fatigue resistance by recrystallization and grain growth to eliminate bonding interfaces in Cu–Cu joints

Atomic-level flatness on oxygen-free copper surface in lapping and chemical mechanical polishing

Coherent consolidation of trillions of nucleations for mono-atom step-level flat surfaces

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