Microstructural and mechanical characterization of Cu/Sn SLID bonding utilizing Co as contact metallization layer

Emadi, Fahimeh; Vuorinen, Vesa; Mertin, S.; Widell, K.; Paulasto‐Kröckel, Mervi

doi:10.1016/j.jallcom.2022.167228

Cited by 8 publications

(5 citation statements)

References 83 publications

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“…Previous studies have demonstrated that cobalt (Co) is a plausible contact metallization for a Cu-Sn SLID system [16], [17], [38], [39]. Our prior investigations [40] have also shown that when a Co foil is in contact with Cu-Sn-In electroplated chips, it demonstrates favorable wettability, In participates in IMC formation, and a full IMC joint can be achieved within the standard bonding timeframe.…”

Section: Introductionmentioning

confidence: 89%

“…5 This transformation results in a volumetric change in the system, potentially serving as a stress initiation point [42]. On the other hand, Co tends not to dissolve readily into the Cu3Sn phase [16], [17]. Consequently, with more Cu3Sn formation, more Co is dissolved into the remaining Cu6Sn5, potentially leading to a weaker interface between Cu3Sn and (Cu,Co)6Sn5.…”

Section: B Tensile Strength and Fracture Modementioning

confidence: 99%

“…Simultaneously, the low bonding temperature might not compromise the subsequent process steps, and therefore the newly formed interconnect areas should have a high remelting temperature [13], [14]. Additionally, the interconnect metallurgy must be designed such that unnecessary lithography processes and wet chemistry of device wafers can be avoided [15], [16], [17].…”

Section: Introductionmentioning

confidence: 99%

“…It has the potential to simultaneously enable hermetic sealing for MEMS and high-density, short signal path electrical interconnects for the integration of MEMS and integrated circuits (ICs) [3], [7], [18], [19], [20]. However, the process temperature of Cu-Sn SLID bonding exceeds 250 °C, and the typical procedure involves electroplating Cu and Sn on both wafers to be bonded [15], [16], [17]. Consequently, achieving optimal performance with Cu-Sn SLID interconnects in highperformance smart sensor systems requires ongoing improvements in bonding material design.…”

Section: Introductionmentioning

confidence: 99%

“…Specifically, it effectively prevents the formation of Cu3(Sn,In) during the bonding process at temperatures ranging from 160 °C to 250 °C. Consequently, the microjoints consist of a void-free single phase, (Cu,Co)6(Sn,In)5 [16], [40]. However, in a pure Cu-Sn-In system, Cu3Sn still forms at 250 °C [35].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Novel low-temperature interconnects for 2.5/3D MEMS integration: demonstration and reliability

Emadi,

Vuorinen,

Liu

et al. 2024

Preprint

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In response to the evolving demands of microelectromechanical system (MEMS) integration, aiming to achieve high-performance electronic products, innovative interconnect solutions are becoming essential. The interconnects must possess key features, including the capability for miniaturization, low processing temperatures, and the ability to maintain a stable microstructure with optimized electrical, mechanical, and thermomechanical properties. To meet these demands, this study designed a novel Cu-Sn-based solid-liquid interdiffusion (SLID) interconnect. The study involved the implementation of a metallization stack, incorporating Co as a layer to interact with low-temperature Cu-Sn-In SLID and form intermetallic compounds (IMCs). Since Cu6(Sn,In)5 forms at a lower bonding temperature than other phases commonly observed in the Cu-Sn-In system, the study aimed to develop interconnects comprising a stable single-phase (Cu,Co)6(Sn,In)5. Bonding conditions were established for the Cu-Sn-In/Co system and the Cu-Sn/Co system as a reference. Thorough assessments of their thermomechanical reliability were conducted through hightemperature storage (HTS), thermal shock (TS), and tensile tests. The Cu-Sn-In/Co system emerged as a reliable low-temperature solution with the following key attributes: 1) a reduced bonding temperature compared to the Cu-Sn SLID interconnects, 2) the absence of the Cu3Sn phase and resulting void-free interconnects, and 3) high thermomechanical reliability, particularly following thermal annealing after bonding.

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