Characterization of Die-to-Wafer Hybrid Bonding using Heterogeneous Dielectrics

Kim, Min-Ki; Park, Soojeoung; Jang, Aeni; Lee, Hyuekjae; Baek, Seungduk; Lee, ChungSun; Kim, Il-Hwan; Park, Jumyong; Jee, Youngkun; Kang, Un-Byoung; Kim, Dae Woo

doi:10.1109/ectc51906.2022.00062

Cited by 13 publications

(2 citation statements)

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“…In hybrid bonding, the Cu surface undergoes chemical mechanical polishing (CMP), leading to the dishing effect, which is characterized by Cu dishing and SiO 2 erosion during the over-polishing step [14,15]. The recess of Cu pads, which is typically a few nanometers [16], should be smaller than their expansions to ensure proper contact during annealing. This allows for oxide-oxide bonding to take place at room temperature before raising the temperature to approximately 250-300 • C for Cu-Cu bonding [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

“…In our previous studies, it was proposed that the thickness of the Cu film affects the quality of the bonding interface [22]. Additionally, the depth of copper joints has been widely suggested to affect the extent of Cu expansion [16,23,24]. However, direct confirmation of the effect of compressive stress on the bonding interface is still insufficient.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Compressive Stress on Copper Bonding Quality and Bonding Mechanisms in Advanced Packaging

Lu,

Lee,

2024

Materials

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The thermal expansion behavior of Cu plays a critical role in the bonding mechanism of Cu/SiO2 hybrid joints. In this study, artificial voids, which were observed to evolve using a focused ion beam, were introduced at the bonded interfaces to investigate the influence of compressive stress on bonding quality and mechanisms at elevated temperatures of 250 °C and 300 °C. The evolution of interfacial voids serves as a key indicator for assessing bonding quality. We quantified the bonding fraction and void fraction to characterize the bonding interface and found a notable increase in the bonding fraction and a corresponding decrease in the void fraction with increasing compressive stress levels. This is primarily attributed to the Cu film exhibiting greater creep/elastic deformation under higher compressive stress conditions. Furthermore, these experimental findings are supported by the surface diffusion creep model. Therefore, our study confirms that compressive stress affects the Cu–Cu bonding interface, emphasizing the need to consider the depth of Cu joints during process design.

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