Self-assembly and mass reflow of copper bumps for flip-chip hybridization in photonic applications

Mourier, Thierry; Auffret, J.; Boutafa, Laura; Miloud-Ali, Nadia; Mendizabal, L.; Peray, Patrick; Castany, Olivier

doi:10.1109/ectc32696.2021.00046

Cited by 3 publications

(4 citation statements)

References 4 publications

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“…Hybrid integration of different photonic components is challenging since the components are typically more fragile than electrical components and have extremely tight optical alignment tolerances, often <1 µm to minimize losses between devices/chips [630]. This is exacerbated by CTE mismatches as low noise detection in astronomy is typically conducted at 70 K for near infrared observations.…”

Section: Current and Future Challengesmentioning

confidence: 99%

“…Finally, advances in heterogeneous integration are critical to minimize the losses, attain high stability and scalability, and thereby, maximize the integration advantage in astrophotonics. The key challenges of heterogeneous integration approaches are the necessity of high alignment accuracy (<0.5 µm) and the high pressures (200 mg/bump) that may be needed for bonding [630,639]. However, new approaches such as mass-reflow of copper bumps have demonstrated a final self-alignment with ∼0.5 µm accuracy in flip-chip assembly of SOI grating couplers and a microlens die, with an initial misalignment tolerance of 10 µm with only 5.5 mg/bump of applied pressure [630].…”

Section: Advances In Science and Technology To Meet Challengesmentioning

confidence: 99%

“…The key challenges of heterogeneous integration approaches are the necessity of high alignment accuracy (<0.5 µm) and the high pressures (200 mg/bump) that may be needed for bonding [630,639]. However, new approaches such as mass-reflow of copper bumps have demonstrated a final self-alignment with ∼0.5 µm accuracy in flip-chip assembly of SOI grating couplers and a microlens die, with an initial misalignment tolerance of 10 µm with only 5.5 mg/bump of applied pressure [630]. To achieve the highest possible coupling efficiencies with small waveguide modes (∼3 µm) in high-contrast materials, alignment accuracies of ∼0.1 µm will be needed.…”

Section: Advances In Science and Technology To Meet Challengesmentioning

confidence: 99%

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2023 Astrophotonics Roadmap: pathways to realizing multi-functional integrated astrophotonic instruments

Jovanovic,

Gatkine,

Anugu

et al. 2023

J. Phys. Photonics

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Photonic technologies offer numerous functionalities that can be used to realize astrophotonic instruments. The most spectacular example to date is the ESO Gravity instrument at the Very Large Telescope in Chile that combines the light-gathering power of four 8-m telescopes through a complex photonic interferometer. Fully integrated astrophotonic devices offer critical advantages for instrument development, including extreme miniaturization when operating at the diffraction-limit, plus integration, superior thermal and mechanical stabilization owing to the small footprint, and high replicability offering significant cost savings. Numerous astrophotonic technologies have been developed to address shortcomings of conventional instruments to date, including the development of photonic lanterns to convert from multimode inputs to single mode outputs, complex aperiodic fiber Bragg gratings to filter OH emission from the atmosphere, beam combiners enabling long baseline interferometry with for example, ESO Gravity, and laser frequency combs for high precision spectral calibration of spectrometers. Despite these successes, the facility implementation of photonic solutions in astronomical instrumentation is currently limited because of 1) low throughputs from coupling to fibers, coupling fibers to chips, propagation and bend losses, device losses, etc., 2) difficulties with scaling to large channel count devices needed for large bandwidths and high resolutions, and 3) efficient integration of photonics with detectors. In this roadmap, we identify 23 key areas that need further development. We outline the challenges and advances needed across those areas covering design tools, simulation capabilities, fabrication processes, the need for entirely new components, integration and hybridization and the characterization of devices. To realize these advances the astrophotonics community will have to work cooperatively with industrial partners who have more advanced manufacturing capabilities. With the advances described herein, multi-functional integrated instruments will be realized leading to novel observing capabilities for both ground and space based platforms, enabling new scientific studies and discoveries.

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Section: Current and Future Challengesmentioning

confidence: 99%

Section: Advances In Science and Technology To Meet Challengesmentioning

confidence: 99%

Section: Advances In Science and Technology To Meet Challengesmentioning

confidence: 99%

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2023 Astrophotonics Roadmap: pathways to realizing multi-functional integrated astrophotonic instruments

Jovanovic,

Gatkine,

Anugu

et al. 2023

J. Phys. Photonics

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“…Copper bonding under suitable process parameters is usually challenging due to the presence of unavoidable native oxides. Various copper-bonding techniques have been reported in the literature that focus on low-temperature and low-pressure processes [ 11 , 12 ]. The usability of a specific bonding technique and its cost effectiveness depend on the characteristics of the mating chips, the bonding process and the production volume.…”

Section: Introductionmentioning

confidence: 99%

Laser-Assisted Micro-Solder Bumping for Copper and Nickel–Gold Pad Finish

2022

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Flip-chip bonding is a key packaging technology to achieve the smallest form factor possible. Using copper as a direct under-bump metal and performing bonding under little force and at a low temperature eliminates the processing step for the deposition of a suitable wetting metal and offers an economical solution for electronic chip packaging. In this paper, various samples with copper and nickel–gold surface finishes are used to apply an in-house solder bumping, flip-chip bonding and reflow process to exhibit the bump-bond feasibility. Native oxides are reduced using process gases, and copper surface protection and solder wetting are achieved using copper formate. Lead-free 40 µm solder balls were bumped on 80 µm copper pads and 120 µm copper pillars to demonstrate a full intermetallic Cu–Cu bond as a base study for stacking applications. Using a low-force bonding technique, various chips with different dimensions were bonded at 0.5–16 MPa, followed by a reflow step at a maximum temperature of 270 ∘C. Then, 30 µm solder balls are utilized to bump the samples with NiAu and Cu bond pads at 50 µm pitch. A mean shear strength of 44 MPa was obtained for the 30 µm Cu samples. To the best of our knowledge, 30 µm solder bumping directly on the copper pads by producing copper formate is a novel research contribution.

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Advanced 3D integration TSV and flip chip technologies evaluation for the packaging of a mobile LiDAR 256 channels beam steering device designed for autonomous driving application

Mourier,

Berchet,

Auffret

et al. 2023

2023 IEEE 73rd Electronic Components and Technology Conference (ECTC)

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Self-assembly and mass reflow of copper bumps for flip-chip hybridization in photonic applications

Cited by 3 publications

References 4 publications

2023 Astrophotonics Roadmap: pathways to realizing multi-functional integrated astrophotonic instruments

2023 Astrophotonics Roadmap: pathways to realizing multi-functional integrated astrophotonic instruments

Laser-Assisted Micro-Solder Bumping for Copper and Nickel–Gold Pad Finish

Advanced 3D integration TSV and flip chip technologies evaluation for the packaging of a mobile LiDAR 256 channels beam steering device designed for autonomous driving application

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