Scaling Package Interconnects Below 20µm Pitch with Hybrid Bonding

Gao, Guanghai; Mirkarimi, Laura; Fountain, G. G.; Wang, Liang; Uzoh, Cyprian; Workman, Thomas; Guevara, Gabe; Mandalapu, Chandrasekhar; Lee, Bongsub; Katkar, Rajesh

doi:10.1109/ectc.2018.00055

Cited by 30 publications

(9 citation statements)

References 4 publications

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“…Hybrid bonding interconnects show excellent reliability, which was already published in recent studies by Xperi [8,11]. According to [8] all tested samples passed the temperature cycling test (-40 °C / 150 °C, 2000 cycles, 45 samples) and the high temperature storage (225 °C, 1000 h, 22 samples) with a resistance drop of approx. 1.2 to 3.4 %.…”

Section: Introductionmentioning

confidence: 59%

“…The successful development of wafer-to-wafer bonding by hybrid bonding or direct bond interconnects led to a fast introduction of this technology to high volume manufacturing [7]. Recent process development focuses on pitch scaling, decreasing of the processing temperature and die-to-wafer as well as die-to-die stacking technologies [3,8,9]. Those investigations also focus on surface readiness level by optimizing the chemicalmechanical polishing (CMP) process and the overall surface cleanliness.…”

Section: Introductionmentioning

confidence: 99%

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Microstructure Development of Cu/SiO₂ Hybrid Bond Interconnects After Reliability Tests

Panchenko

Wambera

Mueller

et al. 2022

IEEE Trans. Compon., Packag. Manufact. Technol.

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The focus of this study is a detailed characterization of hybrid Cu/SiO2 wafer-to-wafer bonding interconnects after reliability testing. Hybrid bonding (or direct bond interconnect) is a technology of choice for fine pitch bonding without microbumps. The main challenge of the hybrid bonding technology is the preparation of a clean Cu/SiO2 surface with controlled Cu dishing. The Cu/Cu interface after hybrid bonding and after reliability testing was investigated by electron backscatter diffraction (EBSD) in this study. The Cu interconnects (diameter 4 μm and pitch 18 μm) enclosed by SiO2 were formed by wafer-to-wafer bonding. The small diced stacks were used for subsequent reliability tests. Three types of tests were carried out: temperature shock test (TST) at -40 °C / 125 °C up to 1000 cycles, isothermal storage at 150 °C, 300 °C, and 400 °C as well as multiple bonding cycles. The results include a comprehensive estimation of the changes in grain diameter, grain boundaries and texture of the interconnects. All samples showed good reliability and stayed intact after all tests. Grain refinement was observed after TST, storage at 150 °C, and multiple bonding cycles compared to the state after bonding. Grain growth was found for the storage at 300/400 °C (up to 6 h). No significant changes in texture were found after the reliability tests. The <111> direction with its characteristic <115> twin orientation are the dominating orientations perpendicular to the bonding interface. The migration of 60 ° twin boundaries has been observed after reliability testing. The results indicate a rotation towards nearby high angle grain boundaries (60 to 45 °).

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Section: Introductionmentioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Microstructure Development of Cu/SiO₂ Hybrid Bond Interconnects After Reliability Tests

Panchenko

Wambera

Mueller

et al. 2022

IEEE Trans. Compon., Packag. Manufact. Technol.

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“…To suppress such a crack formation, longer bonding is needed for bonding interface elimination. The dielectrics have a potential for hybrid bonding using instant bonding [ 39 ] and postannealing [ 49 ] to enhance its reliability.…”

Section: Resultsmentioning

confidence: 99%

Failure Mechanisms of Cu–Cu Bumps under Thermal Cycling

Shie

Hsu

et al. 2021

Materials

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The failure mechanisms of Cu–Cu bumps under thermal cycling test (TCT) were investigated. The resistance change of Cu–Cu bumps in chip corners was less than 20% after 1000 thermal cycles. Many cracks were found at the center of the bonding interface, assumed to be a result of weak grain boundaries. Finite element analysis (FEA) was performed to simulate the stress distribution under thermal cycling. The results show that the maximum stress was located close to the Cu redistribution lines (RDLs). With the TiW adhesion layer between the Cu–Cu bumps and RDLs, the bonding strength was strong enough to sustain the thermal stress. Additionally, the middle of the Cu–Cu bumps was subjected to tension. Some triple junctions with zig-zag grain boundaries after TCT were observed. From the pre-existing tiny voids at the bonding interface, cracks might initiate and propagate along the weak bonding interface. In order to avoid such failures, a postannealing bonding process was adopted to completely eliminate the bonding interface of Cu–Cu bumps. This study delivers a deep understanding of the thermal cycling reliability of Cu–Cu hybrid joints.

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“…One is the scaling-down of electronic devices. The direct bonding of metals can enable such an effort [ 4 ]. It is noted that the reliability of joints is greatly affected by bonding temperature and pressure.…”

Section: Introductionmentioning

confidence: 99%

Failures of Cu-Cu Joints under Temperature Cycling Tests

et al. 2022

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In this study, the failure mechanisms of Cu-Cu joints under thermal cycling were investigated. Two structures of dielectrics (PBO/underfill/PBO and SiO2) were employed to seal the joints. Stress gradients induced in the joints with the different dielectrics were simulated using a finite element method (FEM) and correlated with experimental observations. We found that interfacial voids were forced to move in the direction from high stress regions to low stress ones. The locations of migrated voids varied with the dielectric structures. Under thermal cycling, such voids were likely to move forward to the regions with a small stress change. They relocated and merged with their neighboring voids to lower the interfacial energy.

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Scaling Package Interconnects Below 20µm Pitch with Hybrid Bonding

Cited by 30 publications

References 4 publications

Microstructure Development of Cu/SiO₂ Hybrid Bond Interconnects After Reliability Tests

Microstructure Development of Cu/SiO₂ Hybrid Bond Interconnects After Reliability Tests

Failure Mechanisms of Cu–Cu Bumps under Thermal Cycling

Failures of Cu-Cu Joints under Temperature Cycling Tests

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