Thin-layer Au-Sn solder bonding process for wafer-level packaging, electrical interconnections and MEMS applications

Belov, Nickolai; Chou, T.-K.; Heck, John; Kornelsen, K.; Spicer, D. F.; Akhlaghi, S.; Wang, M.; Zhu, T.

doi:10.1109/iitc.2009.5090361

Cited by 26 publications

(16 citation statements)

References 5 publications

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“…Due to a number of inherent advantages, Au 0.8 Sn 0.2 eutectic bonding has been heavily researched for WLVP packaging and demonstrated using surrogate proxy wafers [31,32,33,34,35,36], RF MEMS switches [37,38], MEMS resonators [39], and infrared imaging smart sensors [40]. In this approach, Au 0.8 Sn 0.2 is deposited on either the lid or device wafer, and a wettable layer, typically Au, is deposited on the other wafer.…”

Section: Bonding Approachesmentioning

confidence: 99%

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Wafer-Level Vacuum Packaging of Smart Sensors

Hilton

Temple

2016

Sensors

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The reach and impact of the Internet of Things will depend on the availability of low-cost, smart sensors—“low cost” for ubiquitous presence, and “smart” for connectivity and autonomy. By using wafer-level processes not only for the smart sensor fabrication and integration, but also for packaging, we can further greatly reduce the cost of sensor components and systems as well as further decrease their size and weight. This paper reviews the state-of-the-art in the wafer-level vacuum packaging technology of smart sensors. We describe the processes needed to create the wafer-scale vacuum microchambers, focusing on approaches that involve metal seals and that are compatible with the thermal budget of complementary metal-oxide semiconductor (CMOS) integrated circuits. We review choices of seal materials and structures that are available to a device designer, and present techniques used for the fabrication of metal seals on device and window wafers. We also analyze the deposition and activation of thin film getters needed to maintain vacuum in the ultra-small chambers, and the wafer-to-wafer bonding processes that form the hermetic seal. We discuss inherent trade-offs and challenges of each seal material set and the corresponding bonding processes. Finally, we identify areas for further research that could help broaden implementations of the wafer-level vacuum packaging technology.

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Section: Bonding Approachesmentioning

confidence: 99%

“…At 81% and 75% Au by weight, the melting temperature is equal to 340 °C and 333 °C, respectively [34]. To realize the melting temperature of 280 °C, the alloy composition must be precisely controlled, which creates process control challenges during deposition and bonding.…”

Section: Bonding Approachesmentioning

confidence: 99%

Wafer-Level Vacuum Packaging of Smart Sensors

Hilton

Temple

2016

Sensors

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“…Metal-to-metal wafer bonding has recently been increasingly attractive in the field of wafer-level MEMS packaging because the technique could significantly decrease the sealing line area which would result in the chip size reduction, realize hermetic sealing, and also enable electrical interconnections between the two bonded wafers [1,2]. Lowtemperature wafer bonding has also become important for various purposes such as reducing the post-bond residual stress at mechanical structures in MEMS devices, and preventing bowing or cracks when bonding two materials with dissimilar coefficients of thermal expansion (CTE).…”

Section: Introductionmentioning

confidence: 99%

Low-temperature, surface-compliant wafer bonding using sub-micron gold particles for wafer-level MEMS packaging

Ishida¹,

Ogashiwa

Kanehira

et al. 2012

2012 IEEE 62nd Electronic Components and Technology Conference

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Low-temperature wafer bonding using sub-micron gold particles was investigated. For more flexible bonding pattern deposition, wafer-level pattern transfer method has been developed to enable patterning on fragile structures such as MEMS devices. Sub-micron Au particle patterns with a width of 20 µm -60 µm and a height around 20 µm were formed on 100mm-diameter glass wafers by means of wafer-level processing using photolithography and a slurry-filling technique, and then successfully transferred onto Si wafers in ambient atmosphere at a temperature of 150°C and an applied pressure of 20 MPa -30 MPa. Finally, wafer bonding was performed at 200°C, 100 MPa and confirmed a sufficient tensile strength of 45.8 MPa. Compression deformation measurement was performed and the performance on a-fewµm surface roughness absorption was demonstrated. A feasibility of further reduction of bonding temperature has been suggested by showing sintering behavior of smallersized Au particles at 150°C.

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“…In MEMS devices as well as electronics devices, wafer level vacuum packaging is one of the most important issues to reduce fabrication cost and to realize easy encapsulation [1][2][3] . For the wafer level packaging, low temperature bonding has an important role to reduce residual stress mainly due to the mismatch of the coefficient of thermal expansion (CTE) between substrates [4][5][6] .…”

Section: Introductionmentioning

confidence: 99%

Evaluations of low temperature bonding using Au sub-micron particles for wafer level MEMS packaging

Ito

Ogashiwa

Kanehira

et al. 2011

2011 International Symposium on Advanced Packaging Materials (APM)

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This paper describes wafer level vacuum packaging with sub-micron Au particles for MEMS (micro electro mechanical systems) applications. Low temperature bonding is indispensable for relevant MEMS packaging, and use of sub-micron Au particles are suitable for hermetic seal bonding. For the fabrication of hermetically sealed wafer level packaging, a base silicon wafer and a cap glass wafer were bonded at around 200ºC. Before bonding, the surface of seal rings was observed with a laser microscope to investigate the effect of surface roughness for hermeticity. After bonding, bonded wafers were dipped in the hydrofluoroether for 30 min. As a result, surface flatness of Au particles contributed to achieve hermetic sealing. Double seal rings structures were also useful to realize hermetic sealing.

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Thin-layer Au-Sn solder bonding process for wafer-level packaging, electrical interconnections and MEMS applications

Cited by 26 publications

References 5 publications

Wafer-Level Vacuum Packaging of Smart Sensors

Wafer-Level Vacuum Packaging of Smart Sensors

Low-temperature, surface-compliant wafer bonding using sub-micron gold particles for wafer-level MEMS packaging

Evaluations of low temperature bonding using Au sub-micron particles for wafer level MEMS packaging

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