Study of Cu-Sn-In system for low temperature, wafer level solid liquid inter-diffusion bonding

Hotchkiss, Joseph H.; Vuorinen, Vesa; Dong, Hanwu; Ross, Glenn; Kaaos, Jani; Paulasto‐Kröckel, Mervi; Wernicke, Tobias; Pönninger, Anneliese

doi:10.1109/estc48849.2020.9229696

Cited by 7 publications

(9 citation statements)

References 26 publications

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“…The objective is to study the possibilities of low-temperature wafer-level SLID bonding down to 170C utilizing ternary Cu-In-Sn metallurgy at bonding temperatures, that are below currently demonstrated solutions [33][34][35]. Additionally, the effect of bonding temperature on the bond quality, microstructure defect formation, and mechanical reliability will be investigated.…”

Section: Introductionmentioning

confidence: 99%

Demonstrating 170 °C Low-Temperature Cu–In–Sn Wafer-Level Solid Liquid Interdiffusion Bonding

Vuorinen

Ross

Klami

et al. 2022

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

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The wafer-level Solid Liquid Interdiffusion (SLID) bonds carried out for this work take advantage of the Cu-In-Sn ternary system to achieve low temperature interconnections. The 100mm Si wafers had µ-bumps from 250µm down to 10µm fabricated by consecutive electrochemical deposition of Cu, Sn and In layers. The optimized wafer-level bonding processes were carried out by EV Group and Aalto University across a range of temperatures from 250C down to 170C. Even though some process quality related challenges were observed, it could be verified that high strength bonds with low defect content can be achieved even at a low bonding temperature of 170C with an acceptable 1-hour wafer-level bonding duration. The microstructural analysis revealed that the bonding temperature significantly impacts the obtained phase structure as well as the number of defects. A higher (250C) bonding temperature led to the formation of Cu3Sn phase in addition to Cu6(Sn,In)5 and resulted in several voids at Cu3Sn|Cu interface. On the other hand, with lower (200C and 170C) bonding temperatures the interconnection microstructure was composed purely of void free Cu6(Sn,In)5. The mechanical testing results revealed the clear impact of bonding quality on the interconnection strength.

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Section: Introductionmentioning

confidence: 99%

Demonstrating 170 °C Low-Temperature Cu–In–Sn Wafer-Level Solid Liquid Interdiffusion Bonding

Vuorinen

Ross

Klami

et al. 2022

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

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“…At room temperature, the stable phases in Cu-In binary system are Cu, , and In. Based on the previous experimental results and the Cu-In binary phase diagram, various IMCs (Cu7In3 (δ), Cu2In (η), Cu11In9, CuIn2, Cu16In9, and CuIn ) can appear during bonding [2], [3], [10]- [13], [16], [17], and phase transformation can occur during aging. Voids with different sizes appear after aging due to the volume shrinkage between different phases [15].…”

Section: Introductionmentioning

confidence: 89%

“…In the higher bonding temperature, the Cu-Sn-In joints comprise a single Cu3Sn and Cu3(Sn,In) phase, respectively. [1], [3]. It has been demonstrated that indium can stabilize the Cu6Sn5 phase and hinder the Cu3Sn phase formation and correspondingly void formation [1].…”

Section: A Microstructural Evolutionmentioning

confidence: 99%

“…Solid-liquid interdiffusion (SLID) bonding, also known as transient liquid phase (TLP) bonding, is a promising process for wafer-level packaging of MEMS/MOEMS devices providing both hermetic sealing and electrical interconnections [1]- [3]. The process is performed in a sandwiched structure of at least a low-melting temperature (LT) metal between two high-melting temperature (HT) metals or metallization stacks.…”

Section: Introductionmentioning

confidence: 99%

“…Utilizing different metal stacks can benefit various devices and manufacturability requirements. Several different binary SLID systems (such as Au-Sn, Au-In, Cu-Sn, Cu-In, Ag-Sn, and Ni-Sn) have been previously studied [1]- [3], [5]- [8]. Cu-Sn SLID system is one of the most popular material systems utilized in MEMS encapsulation and interconnection due to its low process temperature (250-350 °C), high thermal stability, and excellent mechanical reliability [9].…”

Section: Introductionmentioning

confidence: 99%

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Utilizing Co as a contact metallization for wafer-level Cu-Sn-In SLID bonding used in MEMS and MOEMS packaging

Emadi

Vuorinen

Paulasto‐Kröckel

2022

2022 IEEE 9th Electronics System-Integration Technology Conference (ESTC)

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Many MEMS and MOEMS devices require hermetic packaging with preferably no postprocessing after the MEMS device's releasing. Wafer-level Solid-Liquid Interdiffusion (SLID) bonding can provide simultaneous hermetic packaging and better electrical interconnects. Moreover, employing a physically deposited contact metallization on the device wafer instead of chemically deposited layers (such as electrochemical Cu) is of utmost importance as far as reducing the complexity of the MEMS/MOEMS packaging process integration is concerned. The current work studied the possibility of utilizing Co as a contact metallization layer for the low-temperature Cu-Sn-Inbased SLID bonding. In order to guarantee the long-term reliability of the devices, a fundamental understanding of the formation and evolution of interconnection microstructures and mechanical characterization of the joint is of utmost importance. In this work, Cu-Sn-In electroplated Si chips were bonded to Co substrates at a temperature range 160-250°C. During the bonding process, a single intermetallic compound (IMC) (Cu,Co)6(Sn,In)5 formed at the bonding area, with no detectable Cu3Sn phase that causes voids formation. The Young's modulus and hardness of (Cu,Co)6(Sn,In)5 and Cu6Sn5, as a reference, were measured as 124.8±0.5 and 6.2±0.5, 114±1 and 6.7±0.5 MPa, respectively. Furthermore, the current study was able to produce a fully IMC joint of Cu-Sn-In/Co SLID system at 220°C for bonding time as short as 20 minutes.

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Fabrication of Fine-Pitch Cu-Sn Microbumps Using Electroplating and Wet Seed Layer Etching

Shi,

Wang,

Wang

et al. 2024

2024 IEEE 10th Electronics System-Integration Technology Conference (ESTC)

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Study of Cu-Sn-In system for low temperature, wafer level solid liquid inter-diffusion bonding

Cited by 7 publications

References 26 publications

Demonstrating 170 °C Low-Temperature Cu–In–Sn Wafer-Level Solid Liquid Interdiffusion Bonding

Demonstrating 170 °C Low-Temperature Cu–In–Sn Wafer-Level Solid Liquid Interdiffusion Bonding

Utilizing Co as a contact metallization for wafer-level Cu-Sn-In SLID bonding used in MEMS and MOEMS packaging

Fabrication of Fine-Pitch Cu-Sn Microbumps Using Electroplating and Wet Seed Layer Etching

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