Combined surface activated bonding using H-containing HCOOH vapor treatment for Cu/Adhesive hybrid bonding at below 200 °C

He, Rujie; Fujino, Masataka; Akaike, Masatake; Sakai, Taiji; Sakuyama, Seiki; Suga, Tadatomo

doi:10.1016/j.apsusc.2017.03.168

Cited by 19 publications

(13 citation statements)

References 13 publications

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“…It is noted that polyimide and Cu foil failed to achieve bonding at N 2 atmosphere even with a pressure of 30 MPa, while they were robustly bonded at the Ptcatalyzed formic acid atmosphere. It is reported that Pt catalyzes the formic acid to generate H free radicals [20], which reduces Cu oxides to activate surface diffusion and promotes bonding at low temperatures. Additionally, once bonding was achieved, the shear strength of bonded samples increased with increasing pressure, reaching the maximum of 20.31 MPa when the pressure was 30 MPa.…”

Section: Resultsmentioning

confidence: 99%

Low-temperature bonding of surface-activated polyimide to Cu Foil in Pt-catalyzed formic acid atmosphere

Meng

Yang

Gao

et al. 2021

J Mater Sci: Mater Electron

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In this study, a two-step process involving oxygen plasma surface activation and thermos-compression in Pt-catalyzed formic acid gas was used to bond Cu foil and polyimide. The oxygen plasma was used to activate the polyimide surface to achieve strong adhesion with sputtered deposition film, and the Ptcatalyzed formic acid gas removed the oxides on the Cu surface effectively to promote bonding between Cu foil and polyimide. Via this method, a void-less bonding with a maximum shear strength of 20.31 MPa was achieved. The plasma bombardment was found to promote the formation of C-O-Cr and N-Cr bonds between polyimide and deposition metals, which improved their adhesion. After shear test, striped metal films remained on fracture surfaces at both polyimide and Cu foil sides, suggesting the fracture mainly occurred within adhered deposition metals rather than at bonding interface. This low-temperature bonding method is promising to achieve the direct integration between polyimide and copper foil without adhesive, which plays a key role in flexible device integration.

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Section: Resultsmentioning

confidence: 99%

Low-temperature bonding of surface-activated polyimide to Cu Foil in Pt-catalyzed formic acid atmosphere

Meng

Yang

Gao

et al. 2021

J Mater Sci: Mater Electron

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“…According to energy dispersive spectrometer (EDS) analysis, the ratio of the number of Cu atoms to the number of Sn atoms is about 11:3, and then the composition analysis of the cross sections of different bonding bumps is basically close to the atomic ratio of Cu 3 Sn, so the intermediate layer was determined to be Cu 3 Sn [ 23 ]. The Cu 3 Sn and Cu have similar density; when Cu 3 Sn grew on the surface of Cu, the change in volume was very small, so it could generate a dense structure, reasonable metal structure and bonding optimization conditions, there was not too much Cu 6 Sn 5 , avoiding the Kirkendall effect [ 24 , 25 ]. In addition, there were some white bright spots in the IMC layer, but they were not via.…”

Section: Resultsmentioning

confidence: 99%

Research of Wafer Level Bonding Process Based on Cu–Sn Eutectic

Tian

Wang

et al. 2020

Micromachines

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In 3D-system packaging technologies, eutectic bonding is the key technology of multilayer chip stacking and vertical interconnection. Optimized from the aspects of the thickness of the electroplated metal layer, the pretreatment of the wafer surface removes the oxide layer, the mutual alignment between the wafers, the temperature of the wafer bonding, the uniformity of pressure and the deviation of the bonding process. Under the pretreatment conditions of plasma treatment and citric acid cleaning, no oxide layer was obtained on the metal surface. Cu/Sn bumps bonded under the condition of 0.135 Mpa, temperature of 280 °C, Sn thickness of 3–4 μm and a Cu-thickness of five micrometers. Bonded push crystal strength ≥18 kg/cm2, the average contact resistance of the bonding interface is about 3.35 mΩ, and the bonding yield is 100%. All performance indicators meet and exceed the industry standards.

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“…Formic acid (FA, HCOOH) is another acid that erases copper oxide with the special capability that HCOOH converts the oxide to Cu-HCOO and Cu-O-H, which may decompose to Cu. He et al (2017a, 2017b) used H-containing HCOOH vapor and combined the SAB method to bond the Cu/adhesive hybrid samples at 180°C–200°C. Furthermore, the “Cu-first” bonding strategy is confirmed instead of the “adhesive-first” method [schematic diagram is illustrated in Figure 4(c)].…”

Section: Wet Treatment and Plasma-assisted Bondingmentioning

confidence: 99%

“…(a) TEM image of Cu-Cu bonding without a Si layer (He et al , 2016b); (b) cross-sectional FIB analyses of Cu-Cu bonding treated by citric acid (Hung et al , 2021); (c) schematic diagram of the “adhesive-first” bonding strategy (He et al , 2017a); (d) copper bonding temperature-time map (He et al , 2017a); (e) schematic diagram of the PAB method treatment (Chua et al , 2019)…”

Section: Figurementioning

confidence: 99%

Recent progress on bumpless Cu/SiO₂ hybrid bonding for 3D heterogeneous integration

Kang

Niu

et al. 2022

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Purpose Bumpless Cu/SiO2 hybrid bonding, which this paper aims to, is a key technology of three-dimensional (3D) high-density integration to promote the integrated circuits industry’s continuous development, which achieves the stacks of chips vertically connected via through-silicon via. Surface-activated bonding (SAB) and thermal-compression bonding (TCB) are used, but both have some shortcomings. The SAB method is overdemanding in the bonding environment, and the TCB method requires a high temperature to remove copper oxide from surfaces, which increases the thermal budget and grossly damages the fine-pitch device. Design/methodology/approach In this review, methods to prevent and remove copper oxidation in the whole bonding process for a lower bonding temperature, such as wet treatment, plasma surface activation, nanotwinned copper and the metal passivation layer, are investigated. Findings The cooperative bonding method combining wet treatment and plasma activation shows outstanding technological superiority without the high cost and additional necessity of copper passivation in manufacture. Cu/SiO2 hybrid bonding has great potential to effectively enhance the integration density in future 3D packaging for artificial intelligence, the internet of things and other high-density chips. Originality/value To achieve heterogeneous bonding at a lower temperature, the SAB method, chemical treatment and the plasma-assisted bonding method (based on TCB) are used, and surface-enhanced measurements such as nanotwinned copper and the metal passivation layer are also applied to prevent surface copper oxide.

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Combined surface activated bonding using H-containing HCOOH vapor treatment for Cu/Adhesive hybrid bonding at below 200 °C

Cited by 19 publications

References 13 publications

Low-temperature bonding of surface-activated polyimide to Cu Foil in Pt-catalyzed formic acid atmosphere

Low-temperature bonding of surface-activated polyimide to Cu Foil in Pt-catalyzed formic acid atmosphere

Research of Wafer Level Bonding Process Based on Cu–Sn Eutectic

Recent progress on bumpless Cu/SiO₂ hybrid bonding for 3D heterogeneous integration

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Combined surface activated bonding using H-containing HCOOH vapor treatment for Cu/Adhesive hybrid bonding at below 200 °C

Cited by 19 publications

References 13 publications

Low-temperature bonding of surface-activated polyimide to Cu Foil in Pt-catalyzed formic acid atmosphere

Low-temperature bonding of surface-activated polyimide to Cu Foil in Pt-catalyzed formic acid atmosphere

Research of Wafer Level Bonding Process Based on Cu–Sn Eutectic

Recent progress on bumpless Cu/SiO2 hybrid bonding for 3D heterogeneous integration

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Product

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Recent progress on bumpless Cu/SiO₂ hybrid bonding for 3D heterogeneous integration