Two-Mask Wafer-Level Vacuum Packaging With Bulk-Si 3D Interconnects for MEMS Devices and Its Package Performances

Liang, Hengmao; He, Xiao; Xiong, Bin

doi:10.1109/jsen.2022.3182475

Cited by 8 publications

(4 citation statements)

References 24 publications

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“…Note that wafer-level packaging processes for devices are described in detail in our previous work. (17,18) Specifically, a bonding metal layer (e.g., Ti/Au) was sputtered on the cap wafers adopted with low-resistivity Si (~0.01 Ω•cm) and then patterned by wet etching after the fifth lithography. On the basis of the bonding metal patterns, cap cavities with a certain depth were formed on the cap wafers by DRIE at the same time.…”

Section: Device Fabricationmentioning

confidence: 99%

“…However, there is a lack of in-depth analysis on the slide-film damping caused by cavity depth, which is also crucial for the final performance of in-plane-motion resonant MEMS devices and their wafer-level packaging. Based on the proposed 3D wafer-level packaging technology for MEMS in our previous works, (17,18) we investigated the cavity-depth effect on the packaged MEMS resonators dominated by slide-film damping from the theory calculation, simulation, and experimental test.…”

Section: Introductionmentioning

confidence: 99%

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Cavity-Depth Effect on 3D Wafer-Level-Packaged MEMS Resonators by Slide-Film Damping

Liang,

Lv,

Han

et al. 2024

Sensors and Materials

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The slide-film damping effect caused by cavity structures is easily neglected in the design of bulk-micro-machined resonant MEMS device fabrication and packaging processes. On the basis of theory calculations, simulations, and actual tests, in this study, we investigate the cavity-depth effect on 3D wafer-level packaged MEMS resonators with the in-plane-motion mode, in which slide-film damping is dominant. On the one hand, it is found that the slide-film damping coefficient is inversely proportional to the cavity depth and remains stable for the cavity depth above a specific value. The critical cavity depth acquired from theoretical results is ~10 μm, which is distinct from that of ~30 μm from simulation results. On the other hand, the variation tendency of simulation results is more in agreement with those of test results for fabricated devices than the theoretical prediction. Hence, before the structure fabrication for a resonator dominated by slide-film damping, it is imperative to choose a conservative cavity depth with a relatively high value from the combination of theory and simulation analyses, so as to ensure the high or desired Q-factors of fabricated resonators, particularly in wafer-level packaging with the low-vacuum or atmospheric pressure. Overall, this work provides not only an analysis strategy on device cavities' slide-film damping but also the optimization design of wafer-level packaging structures and processes.

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Section: Device Fabricationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cavity-Depth Effect on 3D Wafer-Level-Packaged MEMS Resonators by Slide-Film Damping

Liang,

Lv,

Han

et al. 2024

Sensors and Materials

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“…Apart from temperature, gas leakage will cause pressure fluctuations in MEMS gyroscopes [21,22]. The internal pressure and leakage rate of the wafer-level packaged gyroscopes can be monitored by FIB and capacitance [23,24].…”

Section: Introductionmentioning

confidence: 99%

Research on Packaging Reliability and Quality Factor Degradation Model for Wafer-Level Vacuum Sealing MEMS Gyroscopes

Xu,

Liu,

et al. 2023

Micromachines

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MEMS gyroscopes are widely applied in consumer electronics, aerospace, missile guidance, and other fields. Reliable packaging is the foundation for ensuring the survivability and performance of the sensor in harsh environments, but gas leakage models of wafer-level MEMS gyroscopes are rarely reported. This paper proposes a gas leakage model for evaluating the packaging reliability of wafer-level MEMS gyroscopes. Based on thermodynamics and hydromechanics, the relationships between the quality factor, gas molecule number, and a quality factor degradation model are derived. The mechanism of the effect of gas leakage on the quality factor is explored at wafer-level packaging. The experimental results show that the reciprocal of the quality factor is exponentially related to gas leakage time, which is in accordance with the theoretical analysis. The coefficients of determination (R2) are all greater than 0.95 by fitting the curves in Matlab R2022b. The stable values of the quality factor for drive mode and sense mode are predicted to be 6609.4 and 1205.1, respectively, and the average degradation characteristic time is 435.84 h. The gas leakage time is at least eight times the average characteristic time, namely 3486.72 h, before a stable condition is achieved in the packaging chamber of the MEMS gyroscopes.

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“…Electrical feedthroughs in MEMS devices can be summarized as being in two classes: vertical feedthrough and lateral feedthrough. Vertical feedthrough usually achieves a conducting channel by drilling a via-hole through a glass [ 4 ] or silicon [ 5 ] substrate and filling it with metal materials. Torunbalci, MM [ 6 ] used two separate SOI wafers to fabricate highly doped TSV and suspended MEMS structures, achieving a chamber with a vacuum of around 1 Torr.…”

Section: Introductionmentioning

confidence: 99%

An On-Chip Microscale Vacuum Chamber with High Sealing Performance Using Graphene as Lateral Feedthrough

Zhan

Rao

et al. 2022

Micromachines

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On-chip microscale vacuum chambers with high sealing performance and electrical feedthroughs are highly desired for microscale vacuum electronic devices and other MEMS devices. In this paper, we report an on-chip microscale vacuum chamber which achieves a high sealing performance by using monolayer graphene as lateral electrical feedthrough. A vacuum chamber with the dimensions of π × 2 mm × 2 mm × 0.5 mm is fabricated by anodically bonding a glass chip with a through-hole between two Si chips in a vacuum, after monolayer graphene electrodes have been transferred to the surface of one of the Si chips. Benefiting from the atomic thickness of monolayer graphene, the leak rate of Si–glass bonding interface with a monolayer graphene feedthrough is measured at less than 2 × 10−11 Pa·m3/s. The monolayer graphene feedthrough exhibits a minor resistance increase from 22.5 Ω to 31 Ω after anodic bonding, showing good electrical conductance. The pressure of the vacuum chamber is estimated to be 185 Pa by measuring the breakdown voltage. Such a vacuum is found to maintain for more than 50 days without obvious degradation, implying a high sealing performance with a leak rate of less than 1.02 × 10−16 Pa·m3/s.

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Two-Mask Wafer-Level Vacuum Packaging With Bulk-Si 3D Interconnects for MEMS Devices and Its Package Performances

Cited by 8 publications

References 24 publications

Cavity-Depth Effect on 3D Wafer-Level-Packaged MEMS Resonators by Slide-Film Damping

Cavity-Depth Effect on 3D Wafer-Level-Packaged MEMS Resonators by Slide-Film Damping

Research on Packaging Reliability and Quality Factor Degradation Model for Wafer-Level Vacuum Sealing MEMS Gyroscopes

An On-Chip Microscale Vacuum Chamber with High Sealing Performance Using Graphene as Lateral Feedthrough

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