Low-Temperature Dip-Based All-Copper Interconnects Formed by Pressure-Assisted Sintering of Copper Nanoparticles

Carro, Luca Del; Zürcher, Jonas; Drechsler, Ute; Clark, I. E.; Ramos, Gustavo; Brunschwiler, Thomas

doi:10.1109/tcpmt.2019.2891111

Cited by 19 publications

(4 citation statements)

References 22 publications

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“…33−35 As a good example, nanostructured Cu has been shown to form densified joints with desirable electrical and mechanical properties after sintering at 300 °C. 28,36 Banking on that, researchers from Georgia Tech reported the sintering of nano-Cu pillars or caps to form a direct Cu−Cu bonding. 25,26,28,37,38 They have demonstrated sintering of np-Cu with an effective pressure of 20 MPa for 30 min at 300 °C in a FG atmosphere, after pretreating in dilute acid to remove native oxides.…”

Section: New Trendsmentioning

confidence: 99%

“…A closer look at the cross-section in Figure 13a reveals a relatively minimal porosity observed in our joints compared to that of joints obtained by sintering Cu nanoparticulate pastes or purely np-Cu films under similar sintering conditions. 23,36 This is an important characteristic of the bonding outcome as a high level of porosity in said joints leads to poor electrical, thermal, and reliability performance. In addition, EDX composition results of the sintered sample cross-sections are listed in Table 3.…”

Section: Bonding Quality and Elemental Contentmentioning

confidence: 99%

“…The use of np metals eliminates the need for organic capping and binding agents which have been seen to cause property deterioration when used to form joints . Finally, as all other nanomaterials, np metals also feature a substantial melting point depression. − As a good example, nanostructured Cu has been shown to form densified joints with desirable electrical and mechanical properties after sintering at 300 °C. , Banking on that, researchers from Georgia Tech reported the sintering of nano-Cu pillars or caps to form a direct Cu–Cu bonding. ,,,, They have demonstrated sintering of np-Cu with an effective pressure of 20 MPa for 30 min at 300 °C in a FG atmosphere, after pretreating in dilute acid to remove native oxides . They formed an all-Cu chip-to-substrate interconnection, which demonstrated joints with limited residual porosity, improved manufacturability, and solder-like compliance to assembly. , However, this approach seems to offer limited current throughput and requires specialized manufacturing equipment.…”

Section: New Trendsmentioning

confidence: 99%

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Copper-Based Nanomaterials for Fine-Pitch Interconnects in Microelectronics

et al. 2023

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Conspectus Nanostructured copper-based materials have emerged as a new generation of robust architectures for realizing high-performing and reliable interconnection in modern electronic packaging. As opposed to traditional interconnects, nanostructured materials offer better compliance during the packaging assembly process. Due to the high surface area-to-volume ratio of nanomaterials, they also enable joint formation by sintering through thermal compression at much lower temperatures compared to bulk counterparts. Nanoporous Cu (np-Cu) films have been employed in electronic packaging as materials that facilitate a chip-to-substrate interconnection, realized by a Cu-on-Cu bonding after sintering. In this Account, we discuss the use of self-supported np-Cu films for low-temperature joint formation. The novelty of this work comes from the incorporation of tin (Sn) into the np-Cu structure, thus ensuring lower sintering temperatures with a goal of producing Cu–Sn intermetallic alloy-based joints between two Cu substrates. The incorporation of Sn is done using an all-electrochemical bottom-up approach that involves the conformal coating of fine-structured np-Cu (initially formed by dealloying of Cu–Zn alloys) with a thin layer of Sn. This Account provides insight on existing technologies for using nanostructured films as materials for interconnects as well as the optimization studies for the Sn-coating processes as a new alternative approach. The applicability of the synthesized Cu–Sn nanomaterials for low-temperature joint formation is also discussed. To realize this new approach, the Sn-coating process is administered by a galvanic pulse plating technique, which is optimized to preserve the porosity in the structure with a Cu/Sn atomic ratio that allows for the formation of the Cu6Sn5 intermetallic compound (IMC). Nanomaterials obtained using this approach are subjected to joint formation by sintering at temperatures between 300 and 200 °C under 20 MPa pressure in forming gas atmosphere. Cross-section characterization of the formed joints postsintering reveals densified bonds with minimal porosity that consist predominantly of the Cu3Sn IMC. Furthermore, these joints are less prone to structural inconsistencies compared to existing joints formed using purely np-Cu. The results presented in this Account provide a glimpse into a facile and cost-effective approach for synthesizing nanostructured Cu–Sn films and illustrate their applicability as new interconnect materials.

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Section: New Trendsmentioning

confidence: 99%

Section: Bonding Quality and Elemental Contentmentioning

confidence: 99%

Section: New Trendsmentioning

confidence: 99%

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Copper-Based Nanomaterials for Fine-Pitch Interconnects in Microelectronics

et al. 2023

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“…Currently, dip based interconnect formation have been studied using copper paste for all-copper interconnects by sintering between 200 °C and 250 °C in a batch oven under formic atmosphere. [18] Whereas sintering without pressure is considered, the best performances are obtained with a bonding pressure up to 50 MPa. The consequence of this bonding pressure is thinner sintered joints (1-3 µm) that would hardly compensate the inhomogeneity of the pillar height.…”

Section: Introductionmentioning

confidence: 99%

Development and Characterizations of Fine Pitch Flip-Chip Interconnection Using Silver Sintering

Gougeon,

Souriau,

Mendizabal

et al. 2024

IMAPSource Proceedings

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Flip-chip interconnects made of silver are promising candidates to overcome the intrinsic limits of solderbased interconnects and match the demand for increased current densities of high-performance microprocessors. Dipbased interconnects have been demonstrated to be a promising approach to form electrical interconnects by sintering paste between copper pillars and pads. However, the quality of the process is limited by residual porosity and poor performances of the sintered joint formed between the pillar and the pad during sintering if a pressure > 50 MPa is not applied in order to decrease the final porosity. In this study, development has been focused on varying key dipping process parameters allowing a pressureless sintering process. Dip-transfer process was optimized on test vehicle and has shown electrical continuity over 700 interconnections with diameter down to 50 μm. We demonstrate high reliability of the process with microstructural observations, tomography X and thermal cycle up to 200 cycles without breakdown.

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Microstructural evolution, fracture behavior and bonding mechanisms study of copper sintering on bare DBC substrate for SiC power electronics packaging

Liu

Fan

et al. 2022

Journal of Materials Research and Technology

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Low-Temperature Dip-Based All-Copper Interconnects Formed by Pressure-Assisted Sintering of Copper Nanoparticles

Cited by 19 publications

References 22 publications

Copper-Based Nanomaterials for Fine-Pitch Interconnects in Microelectronics

Copper-Based Nanomaterials for Fine-Pitch Interconnects in Microelectronics

Development and Characterizations of Fine Pitch Flip-Chip Interconnection Using Silver Sintering

Microstructural evolution, fracture behavior and bonding mechanisms study of copper sintering on bare DBC substrate for SiC power electronics packaging

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