Novel Cu-to-Cu Bonding With Ti Passivation at 180$^{\circ}{\rm C}$ in 3-D Integration

Huang, Yi-Wen; Chien, Yu-San; Tzeng, Ruoh-Ning; Shy, Ming-Shaw; Lin, T.Y.; Chen, Kou-Hua; Chiu, Chi-Tsung; Chiou, Jin-Chern; Chuang, Ching-Te; Hwang, Wei; Tong, Ho‐Ming; Chen, Kuan‐Neng

doi:10.1109/led.2013.2285702

Cited by 90 publications

(32 citation statements)

References 11 publications

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“…Alternatively, Chen et.al. proposed a novel wafer-level Cu-Cu bonding using Ti as the passivation layer on Cu surface at 180 ˚C and 1.91 MPa pressure by keeping eye on CMOS in-line process flow [29]. However, application of such a high pressure condition during bonding may damage the delicate underneath Cu interconnect and seriously affect the system performance.…”

Section: Introductionmentioning

confidence: 99%

Metal-Alloy Cu Surface Passivation Leads to High Quality Fine-Pitch Bump-Less Cu-Cu Bonding for 3D IC and Heterogeneous Integration Applications

Panigrahy¹,

Bonam

et al. 2018

2018 IEEE 68th Electronic Components and Technology Conference (ECTC)

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Abstract-In this paper, we report a low temperature, finepitch, bump-less, damascene compatible Cu-Cu thermocompression bonding, using an optimized ultra-thin passivation layer, Constantan, which is an alloy (CopperNickel) of 55% Cu and 45% Ni. Surface oxidation and its roughness are the major bottlenecks in achieving high quality, low temperature, and fine-pitch Cu-Cu bonding. In this endeavor, we have used Cu rich alloy (Constantan) for passivation of Cu surface prior to bonding. We have systematically optimized the constantan passivation layer thickness for high quality low temperature, low pressure, bump-less Cu-Cu bonding. Also, we have studied systematically the efficacy of Cu surface passivation with optimized ultra-thin constantan alloy passivation layer. After rigorous trial and optimization, we successfully identified 2 nm passivation layer thickness, at which very high quality Cu-Cu bonding could be accomplished at sub 200 ˚C with a nominal contact pressure of 0.4 MPa. Post-bonding, electrical and mechanical characterization were validated using four-probe IV measurement and bond strength measurement respectively. Furthermore, Cu-Cu bonding interface was analyzed using IR wafer bonder inspection tool. Very high bond strength of 163 MPa and defect free interface observed by WBI-IR clearly suggests, Cu-Cu fine-pitch bonding with optimized ultra-thin alloy of 2 nm thick constantan, is of very high quality and reliable. Moreover, this novel bonding approach with alloy based interconnect passivation technique is the prime contestant for future heterogeneous integration.

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Section: Introductionmentioning

confidence: 99%

Metal-Alloy Cu Surface Passivation Leads to High Quality Fine-Pitch Bump-Less Cu-Cu Bonding for 3D IC and Heterogeneous Integration Applications

Panigrahy¹,

Bonam

et al. 2018

2018 IEEE 68th Electronic Components and Technology Conference (ECTC)

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“…In order to lower the bonding temperature, many studies focused on how to improve the planarization of the bonding surface, including ultra-precision cutting proposed by T. Sakai 11 and direct bond interconnect (DBI) proposed by P. Enguist. 12 Other researchers protected Cu bonding surface from oxidation and contamination by Ti passivation, 13 self-assembled monolayer (SAM), 14 or surface activated bonding (SAB) technique. 17,18 However, almost all the low temperature bonding techniques were quite time-consuming (over 30min) at either pre-bonding stage or post-annealing stage.…”

Section: Introductionmentioning

confidence: 99%

Low temperature Cu-Cu bonding using copper nanoparticles fabricated by high pressure PVD

Cai

Wang

et al. 2017

AIP Advances

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Copper nanoparticles (Cu NPs) fabricated by physical vapor deposition (PVD) were introduced in Cu-Cu bonding as surface modification. The bonding structure with Ti adhesive/barrier layer and Cu substrate layer was fabricated on both surfaces first. Loose structure with Cu NPs was then deposited by magnetron sputtering in a high pressure environment. Solid state Cu-Cu bonding process was accomplished at 200°C for 3min under the pressure of 20MPa. Die shear test was carried out and an average bonding strength of 36.75MPa was achieved. The analysis of fracture surface revealed a high-reliability bonding structure. According to cross-sectional observations, a void-free intermediate Cu layer with thickness around 10nm was obtained. These results demonstrated that a reliable low temperature time-saving Cu-Cu bonding was realized by Cu NPs between the bonding pairs. This novel bonding method might be one of the most attractive techniques in the application of ultra-fine pitch 3D integration.

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“…Therefore, it is necessary to develop a low-temperature Cu bonding scheme with excellent and reliable performance. In [7], Ti passivation layer on the Cu surface was proposed to protect Manuscript Cu from oxidation before the bonding process. This bond structure can successfully be achieved at the low temperature of 180°C.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, only chip-level, not wafer-level, Cu bonding with Ti passivation is demonstrated [7]. In this paper, in wafer-level, Pd is used as another passivation material to protect Cu because of its material properties [8], [9].…”

Section: Introductionmentioning

confidence: 99%

Demonstration and Electrical Performance of Cu–Cu Bonding at 150 °C With Pd Passivation

Huang

Chien

Tzeng

et al. 2015

IEEE Trans. Electron Devices

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In this paper, one low-temperature direct Cu bonding structure is demonstrated using metal passivated layers. With the protection of Cu bonding layer, the bonding temperature can be reduced to meet low thermal budget requirement. Direct wafer-level Cu bond scheme with Pd passivation is successfully demonstrated at 150°C. Electrical performance along with the material analysis and reliability tests of passivated Cu bonded structures is presented. Furthermore, reliability assessments, including current stressing, temperature cycling, and unbiased highly accelerated stress test, imply excellent stability without electrical degradation. Diffusion behavior between passivation Pd and Cu layers is surveyed, and the corresponding mechanism is discussed as well. The low-temperature Cu/Pd-Pd/Cu bonded structure presents good bond quality and electrical performance, indicating a great potential for 3-D integration applications. Index Terms-3-D integration, Cu bonding, passivation.0018-9383

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Novel Cu-to-Cu Bonding With Ti Passivation at 180$^{\circ}{\rm C}$ in 3-D Integration

Cited by 90 publications

References 11 publications

Metal-Alloy Cu Surface Passivation Leads to High Quality Fine-Pitch Bump-Less Cu-Cu Bonding for 3D IC and Heterogeneous Integration Applications

Metal-Alloy Cu Surface Passivation Leads to High Quality Fine-Pitch Bump-Less Cu-Cu Bonding for 3D IC and Heterogeneous Integration Applications

Low temperature Cu-Cu bonding using copper nanoparticles fabricated by high pressure PVD

Demonstration and Electrical Performance of Cu–Cu Bonding at 150 °C With Pd Passivation

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