Low-temperature Metal Bonding for Optical Device Packaging

Golim, Obert P.; Vuorinen, Vesa; Tiwary, Nikhilendu; Ross, Glenn; Paulasto‐Kröckel, Mervi

doi:10.23919/empc53418.2021.9585007

Cited by 4 publications

(3 citation statements)

References 16 publications

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“…However, when the bonding temperature is ≤200°C the bond is composed of single phase Cu 6 (Sn,In) 5 , which doesn't transform to Cu 3 (Sn,In) even after extensive solid state annealing (>500h at 150°C) (3). In order to demonstrate that small µ-bonds can be manufactured at temperatures as low as 150°C Si wafers containing 10 µm-sized microbumps based on the Cu-Sn-In ternary system were fabricated with wafer-level bonding (5,6). The test wafers had symmetrical metallization structure of 4 µm Cu| 1,5 µm Sn|1,5 µm In.…”

Section: Auin Bondingmentioning

confidence: 99%

Recent Developments in Low Temperature Wafer Level Metal Bonding for Heterogenous Integration

Wernicke,

Rebhan,

Vuorinen

et al. 2023

ECS Trans.

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An overview of various low temperature (<200°C) wafer bonding processes using metal interlayers is presented. Such processes are very attractive for novel applications in 3D heterogenous packaging as the allow for simultaneous formation of electrical interconnects, as well as hermetic encapsulation of various sensors and microelectromechanical systems-based devices. Metal wafer bonding is a generic category of processes consisting of various sub-categories, each one defined by the different principles governing the process. One can differentiate between eutectic wafer bonding (a eutectic alloy is formed as bonding layer during the process by liquid-solid interdiffusion), intermetallic wafer bonding (an intermetallic alloy is formed as bonding layer during the process by solid-liquid interdiffusion, process known also as Solid Liquid Intermetallic Diffusion – SLID or Transient Liquid Phase – TLP), and metal thermo-compression (TC) wafer bonding. Different critical/gating parameters were investigated and their impact for generally reducing processing temperatures for the different metal bonding systems was studied.

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Section: Auin Bondingmentioning

confidence: 99%

Recent Developments in Low Temperature Wafer Level Metal Bonding for Heterogenous Integration

Wernicke,

Rebhan,

Vuorinen

et al. 2023

ECS Trans.

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“…With excellent wetting properties on glass, quartz, and ceramic materials, they could be ideal for metal-to-non-metal joining [30]. Furthermore, the bonding temperature can be as low as 150 °C [34], and the remelting temperature exceeds 600 °C [21], as the bonding results in a fully formed IMC bond-line without any traces of unreacted low melting point material [34], [35], [36]. Two IMCs (Cu3(In,Sn) and Cu6(In,Sn)5) have been reported to form in reactions of InSn alloys with Cu at temperatures between 150 °C and 400 °C [37].…”

Section: Introductionmentioning

confidence: 99%

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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“…They reported that the bonding temperature impacts the reaction products and the number of de-fects: 1) Cu3Sn phase and Cu6(Sn,In)5 with several voids at Cu3Sn/Cu interface at a bonding temperature of 250°C, and 2) void-free single Cu6(Sn,In)5 at 150°C and 170°C. O. Golim et al [20] bonded Si wafer to different optically transparent mate-rials at 200°C. The bond was composed of the single Cu6(Sn,In)5 phase.…”

Section: Introductionmentioning

confidence: 99%

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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Low-temperature Metal Bonding for Optical Device Packaging

Cited by 4 publications

References 16 publications

Recent Developments in Low Temperature Wafer Level Metal Bonding for Heterogenous Integration

Recent Developments in Low Temperature Wafer Level Metal Bonding for Heterogenous Integration

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

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

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