Room-temperature hermetic sealing by ultrasonic bonding with Au compliant rim

Takigawa, Ryo; Iwanabe, Keiichiro; Shuto, Takahide; Takao, Takayuki; Asano, Tanemasa

doi:10.7567/jjap.53.06jm05

Cited by 21 publications

(19 citation statements)

References 34 publications

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“…This test is simple and a good indicator of gas leakage. (32) Figure 6(b) shows an optical microscopy image of a sealed area after immersing it in water. The dark and bright areas represent penetrated water and air, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…(30,31) Recently, RT vacuum packaging has been demonstrated using compliant rims made of Au with ultrasonic assist. (32) A large Au-Au bonding strength could be achieved, and the ability of the compliant rim was experimentally verified. Therefore, we have focused on compliant rims made of Cu.…”

Section: Introductionmentioning

confidence: 90%

“…Next, a photoresist pattern having undercut holes was formed by photolithography. (32) We used a chemically amplified negative-tone photoresist. After that, Cu electroplating was applied to fill these undercut holes.…”

Section: Methodsmentioning

confidence: 99%

“…In this experiment, our flip chip bonder equipped with an ultrasonic bonding tool was used. (30)(31)(32) The ultrasonic amplitude was 1.5 μm and the ultrasonic frequency was 48.5 KHz. The bonding time was 1.5 s and the pressing load was 40 N/rim.…”

Section: Methodsmentioning

confidence: 99%

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Room-temperature Hermetic Packaging Using Ultrasonic Cu?Cu Bonding with Compliant Rim

Takigawa

Iwanabe

Ikeda

et al. 2018

Sensors and Materials

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In this paper, hermetic packaging using room-temperature (RT) Cu-Cu bonding is demonstrated for microsystem packaging. The bonding of the compliant rim made of Cu to electroplated Cu was performed with ultrasonic assist at RT. Owing to the cone-shaped cross section of the compliant rim, it easily deforms under pressing load with ultrasonic assist and bonds to the counter Cu film at RT. As a result of a simple vacuum test, the air leak rate of the cavity inside the bonded sample was approximately 2 × 10 −11 Pa•m 3 /s, which may be sufficiently low for applications of vacuum packaging of microdevices.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 90%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Room-temperature Hermetic Packaging Using Ultrasonic Cu?Cu Bonding with Compliant Rim

Takigawa

Iwanabe

Ikeda

et al. 2018

Sensors and Materials

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“…Low-temperature bonding techniques have been extensively studied for the packaging of MEMS assemblies to suppress thermal damage [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]. Particularly, atomically smooth Au surfaces can form atomic bonds at room temperature [ 8 , 9 , 10 ], which enables the integration of dissimilar materials regardless of the mismatches in the coefficient of thermal expansion. It has been demonstrated that wafers coated with Au/Ti (from top to bottom) bonding layers can form vacuum packaging at room temperature [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

Wafer-Scale Room-Temperature Bonding of Smooth Au/Ti-Based Getter Layer for Vacuum Packaging

Matsumae

Kariya

Kurashima

et al. 2022

Sensors

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This study demonstrates room-temperature bonding using a getter layer for the vacuum packaging of microsystems. A thick Ti layer covered with an Au layer is utilized as a getter layer because it can absorb gas molecules in the package. Additionally, smooth Au surfaces can form direct bonds for hermetic sealing at room temperature. Direct bonding using a getter layer can simplify the vacuum packaging process; however, typical getter layers are rough in bonding formation. This study demonstrates two fabrication techniques for smooth getter layers. In the first approach, the Au/Ti layer is bonded to an Au layer on a smooth SiO2 template, and the Au/SiO2 interface is mechanically exfoliated. Although the root-mean-square roughness was reduced from 2.00 to 0.98 nm, the surface was still extremely rough for direct bonding. In the second approach, an Au/Ti/Au multilayer on a smooth SiO2 template is bonded with a packaging substrate, and the Au/SiO2 interface is exfoliated. The transferred Au/Ti/Au getter layer has a smooth surface with the root-mean-square roughness of 0.54 nm and could form wafer-scale direct bonding at room temperature. We believe that the second approach would allow a simple packaging process using direct bonding of the getter layer.

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