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

Ito, Shin Ichi; Ogashiwa, Toshinori; Kanehira, Yukio; Ishida, Hiroyuki; Shoji, Shuichi; Mizuno, Jun

doi:10.1109/isapm.2011.6105749

Cited by 4 publications

(2 citation statements)

References 11 publications

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“…In addition, high temperature (typically 400 • C) and high voltage (several hundred V) in anodic bonding can be a problem for certain devices. 22 There are also wafer bonding methods using solder, [23][24][25] metal nanoparticles, [26][27][28] and other metal pastes. These methods, however, have the same problem of footprint as glass frit bonding; besides, bonding margin formed by a metal paste may affect RF characteristics of feedthrough wiring.…”

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confidence: 99%

Metal‐bonding‐based hermetic wafer‐level MEMS packaging technology using in‐plane feedthrough: Hermeticity and high frequency characteristics of thick gold film feedthrough

Moriyama

Suzuki

Totsu

et al. 2019

Electrical Engineering Japan

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Au-Au-bonding-based wafer-level vacuum packaging technology using in-plane feedthrough of thick Au signal lines was developed for high-frequency micro electromechanical system (RF MEMS). Compared with conventional technology based on glass frit bonding, the developed technology is advantageous in terms of smaller width of sealing frames, lower process temperature, and smaller amount of degas. To guarantee the hermetic sealing, the adhesion between the thick Au lines and a SiOx dielectric frame is improved by an Al 2 O 3 interlayer by atomic layer deposition. The steps of the dielectric frame above the thick Au lines are absorbed by an electroplated Au seal ring planarized by fly cutting. The thermocompression bonding of the Au seal rings of 20-100 m width was done at 300 ºC. A cavity pressure of about 500 Pa or lower was measured by "zero balance method" using Si diaphragms. Vacuum sealing was maintained for more than 19 months, and the leak rate is less than 8×10-16Pa m3/s. The isolation of open signal lines was measured up to 10 GHz for different designs of the sealing ring and SiOx dielectric frame. The influence of the in-plane feed through to the isolation is as low as 2-3 dB, if the width of the sealing ring is 20 m and the thickness of SiOx dielectric frame is larger than 10 m. The developed wafer-level packaging technology is ready for applications to an radio frequency (RF) MEMS switch. K E Y W O R D SALD (Atomic Layer Deposition), feedthrough, metal bonding, RF MEMS, wafer-level packaging FOREWORDThe main feature of wafer-level packaging of MEMS (micro electromechanical system) is hermetic or vacuum sealing while retaining internal space. 1 With high-frequency (RF) MEMS switches, internal space is usually retained in vacuum to prevent degradation of electric contacts, or to maintain switching speed through suppression of aid damping. [2][3][4][5][6][7][8][9][10][11][12][13][14] In so doing, leads must be drawn while maintaining vacuum, which is a problem especially in RF MEMS using low-resistance thick Au lines.Cap wafer bonding using glass frit, 5,15,16 feedthrough glass substrates, 7,17 anodic bonding of LTCC (Low Temperature Cofired Ceramic) substrates, 19,20 and other methods are long known techniques for wafer-level hermetic packaging of RF MEMS. The technique using glass frit is simple and convenient. Specifically, glass frit fusion allows for some unevenness of bonding surface; therefore, bonding surface (seal ring) may traverse feedthrough wiring, while requirements for surface roughness are not stringent. However, there are concerns that gases generated from glass frit 21 and high temperature during bonding (normally above 450 • C) would adversely affect device performance and reliability. Degree of vacuum in a cavity after glass frit bonding is reported to be 900-2,000 Pa when no getter is used. Besides, the width of seal ring using screen print is normally 100-150 m or greater; taking into 44

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Metal‐bonding‐based hermetic wafer‐level MEMS packaging technology using in‐plane feedthrough: Hermeticity and high frequency characteristics of thick gold film feedthrough

Moriyama

Suzuki

Totsu

et al. 2019

Electrical Engineering Japan

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“…Therefore a TSV dry filling process using a slurry containing submicron Au particles was proposed by our group [8]. The slurry including the Au particles [9] was uniformly filled into vias with a squeegee under low pressure in a short time. It was found that submicron Au particles were a very useful material for high-throughput fabrication of TSVs.…”

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Simultaneous fabrication of a through‐glass interconnect via and a bump using dry film resist and submicron gold particles

Mimatsu¹,

Mizuno

Shoji³

et al. 2014

Micro & Nano Letters

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A process for the simultaneous fabrication of through-glass interconnect vias (TGVs) and gold (Au) bumps using dry film resist and submicron Au particles is proposed. A Ti/Pt/Au layer was sputtered on the top and bottom surfaces of glass vias to improve the adhesion between the glass substrate and submicron Au particles. The submicron Au particles filled the resist holes and glass vias fabricated by photolithography and by the two-electrode method, respectively, and were then sintered. The height and diameter of the fabricated Au bumps were about 20-25 and 200 µm, respectively. The Ti/Pt/Au layer on the surface of the glass substrate was removed by Ar ion milling to isolate each bump electrically. The resistance of a single Au bump and TGV was evaluated using the four-wire ohm method to be about 0.05 Ω. Furthermore, Au bump bonding was demonstrated. Fractured Au bumps and TGVs were observed by scanning electron microscopy after the bonded sample was peeled. It is expected that this fabrication process using a dry film resist and submicron Au particles will be useful in simple packaging processes to form glass interposer substrates or glass integrated circuit chips.

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Simple through silicon interconnect via fabrication using dry filling of sub-micron Au particles for 3D MEMS

Shih

Nimura

Kanehira³

et al. 2013

2013 IEEE 26th International Conference on Micro Electro Mechanical Systems (MEMS)

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

Cited by 4 publications

References 11 publications

Metal‐bonding‐based hermetic wafer‐level MEMS packaging technology using in‐plane feedthrough: Hermeticity and high frequency characteristics of thick gold film feedthrough

Metal‐bonding‐based hermetic wafer‐level MEMS packaging technology using in‐plane feedthrough: Hermeticity and high frequency characteristics of thick gold film feedthrough

Simultaneous fabrication of a through‐glass interconnect via and a bump using dry film resist and submicron gold particles

Simple through silicon interconnect via fabrication using dry filling of sub-micron Au particles for 3D MEMS

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