A kinetic model of copper-to-copper direct bonding under thermal compression

Shie, Kai-Cheng; Гусак, А. М.; Tu, King‐Ning; Chen, Chih

doi:10.1016/j.jmrt.2021.09.071

Cited by 54 publications

(19 citation statements)

References 51 publications

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“…The contact regions were under severe compressive stress while the non-contact regions (voids) were subjected to less severe or no stress. This leads to a stress gradient where Cu atoms diffuse from the high localized to lower stress regions [ 41 , 42 , 43 ]. These Cu atoms slowly fill up voids and eventually form a bonding.…”

Section: Discussionmentioning

confidence: 99%

Interfacial Characterization of Low-Temperature Cu-to-Cu Direct Bonding with Chemical Mechanical Planarized Nanotwinned Cu Films

et al. 2022

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Copper-to-copper (Cu-to-Cu) direct bonding is a promising approach to replace traditional solder joints in three-dimensional integrated circuits (3D ICs) packaging. It has been commonly conducted at a temperature over 300 °C, which is detrimental to integrated electronic devices. In this study, highly (111)-oriented nanotwinned (nt) Cu films were fabricated and polished using chemical mechanical planarization (CMP) and electropolishing. We successfully bonded and remained columnar nt-Cu microstructure at a low temperature of 150 °C thanks to the rapid diffusion of Cu on (111) surface. We employed a new microstructural method to characterize quantitatively the interfacial bonding quality using cross-sectional and plan-view microstructural analyses. We discovered that CMP nt-Cu bonding quality was greater than that of electropolished nt-Cu ones. The CMP nt-Cu films possessed extremely low surface roughness and were virtually free of pre-existing interface voids. Thus, the bonding time of such CMP nt-Cu films could be significantly shortened to 10 min. We expect that these findings may offer a pathway to reduce the thermal budget and manufacturing cost of the current 3D ICs packaging technology.

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Section: Discussionmentioning

confidence: 99%

Interfacial Characterization of Low-Temperature Cu-to-Cu Direct Bonding with Chemical Mechanical Planarized Nanotwinned Cu Films

et al. 2022

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“…More importantly, the (111) surface has the highest diffusivity among all the crystallographic planes in face-centered cubic (FCC) crystals, this is due to the fact that the (111) plane is the most densely packed surface which contributes to high atomic diffusivity [ 13 , 14 ]. The bonding mechanism is attributed to surface creep, which is atomic diffusion under stress gradient at elevated temperatures [ 15 ]. Thus, direct bonding can be completed at low temperatures.…”

Section: Introductionmentioning

confidence: 99%

Low-Temperature Cu/SiO2 Hybrid Bonding with Low Contact Resistance Using (111)-Oriented Cu Surfaces

et al. 2022

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We adopted (111)-oriented Cu with high surface diffusivity to achieve low-temperature and low-pressure Cu/SiO2 hybrid bonding. Electroplating was employed to fabricate arrays of Cu vias with 78% (111) surface grains. The bonding temperature can be lowered to 200 °C, and the pressure is as low as 1.06 MPa. The bonding process can be accomplished by a 12-inch wafer-to-wafer scheme. The measured specific contact resistance is 1.2 × 10−9 Ω·cm2, which is the lowest value reported in related literature for Cu-Cu joints bonded below 300 °C. The joints possess excellent thermal stability up to 375 °C. The bonding mechanism is also presented to provide more understanding on hybrid bonding.

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“…A low-temperature bonding technology and reliable connection interface greatly influence electronic systems’ performance and service life, especially when packaging density dramatically increases with device scaling [ 2 , 3 ]. Traditional surface bonding techniques in electronic assembly rely on high-temperature processes such as reflow soldering [ 4 , 5 ] and thermo-compression bonding [ 6 ], which can lead to undesirable thermal damage, toxic solder materials pollution, and a thermal mismatch at the bonding interface. Recently various nanometal materials such as metal nanowires, nanoparticles, and nanocones-based surface bonding are being studied to lower the bonding temperature and pressure [ 7 , 8 , 9 , 10 ].…”

Section: Introductionmentioning

confidence: 99%

Study on Nanoporous Graphene-Based Hybrid Architecture for Surface Bonding

et al. 2022

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Graphene-copper nanolayered composites have received research interest as promising packaging materials in developing next-generation electronic and optoelectronic devices. The weak van der Waal (vdW) contact between graphene and metal matrix significantly reduces the mechanical performance of such composites. The current study describes a new Cu-nanoporous graphene-Cu based bonding method with a low bonding temperature and good dependability. The deposition of copper atoms onto nanoporous graphene can help to generate nanoislands on the graphene surface, facilitating atomic diffusion bonding to bulk copper bonding surfaces at low temperatures, according to our extensive molecular dynamics (MD) simulations on the bonding process and pull-out verification using the canonical ensemble (NVT). Furthermore, the interfacial mechanical characteristics of graphene/Cu nanocomposites can be greatly improved by the resistance of nanostructure in nanoporous graphene. These findings are useful in designing advanced metallic surface bonding processes and graphene-based composites with tenable performance.

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A kinetic model of copper-to-copper direct bonding under thermal compression

Cited by 54 publications

References 51 publications

Interfacial Characterization of Low-Temperature Cu-to-Cu Direct Bonding with Chemical Mechanical Planarized Nanotwinned Cu Films

Interfacial Characterization of Low-Temperature Cu-to-Cu Direct Bonding with Chemical Mechanical Planarized Nanotwinned Cu Films

Low-Temperature Cu/SiO2 Hybrid Bonding with Low Contact Resistance Using (111)-Oriented Cu Surfaces

Study on Nanoporous Graphene-Based Hybrid Architecture for Surface Bonding

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