Sequential Plasma-Activated Bonding Mechanism of Silicon/Silicon Wafers

Howlader, M. M. R.; Kagami, G; Lee, Sang Ho; Wang, Jinguo G.; Kim, Moon J.; Yamauchi, Akira

doi:10.1109/jmems.2010.2049731

Cited by 17 publications

(18 citation statements)

References 28 publications

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“…Because gold (Au) nanoantennas will be embedded into the nanofluidics, bonding performed at complementary metal-oxide-semiconductor (CMOS)-compatible temperatures is necessary to protect the metal shapes. According to the previous studies, fluorine (F)- − or nitrogen (N)- ,− contained plasma can be more effective in modifying surfaces and strength bonding interfaces. Here, we developed an NH 3 /O 2 /H 2 O plasma-activated low-temperature direct bonding method for Al 2 O 3 and SiO 2 .…”

Section: Results and Discussionmentioning

confidence: 99%

Nanometer-Scale Heterogeneous Interfacial Sapphire Wafer Bonding for Enabling Plasmonic-Enhanced Nanofluidic Mid-Infrared Spectroscopy

Ren

Dong

et al. 2020

ACS Nano

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As one of the most effective surface-enhanced infrared absorption (SEIRA) techniques, metal–insulator–metal structured metamaterial perfect absorbers possess an ultrahigh sensitivity and selectivity in molecular infrared fingerprint detection. However, most of the localized electromagnetic fields (i.e., hotspots) are confined in the dielectric layer, hindering the interaction between analytes and hotspots. By replacing the dielectric layer with the nanofluidic channel, we develop a sapphire (Al2O3)-based mid-infrared (MIR) hybrid nanofluidic-SEIRA (HN-SEIRA) platform for liquid sensors with the aid of a low-temperature interfacial heterogeneous sapphire wafer direct bonding technique. The robust atomic bonding interface is confirmed by transmission electron microscope observation. We also establish a design methodology for the HN-SEIRA sensor using coupled-mode theory to carry out the loss engineering and experimentally validate its feasibility through the accurate nanogap control. Thanks to the capillary force, liquid analytes can be driven into sensing hotspots without external actuation systems. Besides, we demonstrate an in situ real-time dynamic monitoring process for the acetone molecular diffusion in deionized water. A small concentration change of 0.29% is distinguished and an ultrahigh sensitivity (0.8364 pmol–1 %) is achieved. With the aid of IR fingerprint absorption, our HN-SEIRA platform brings the selectivity of liquid molecules with similar refractive indexes. It also resolves water absorption issues in traditional IR liquid sensors thanks to the sub-nm long light path. Considering the wide transparency window of Al2O3 in MIR (up to 5.2 μm), the HN-SEIRA platform covers more IR absorption range for liquid sensing compared to fused glass commonly used in micro/nanofluidics. Leveraging the aforementioned advantages, our work provides insights into developing a MIR real-time liquid sensing platform with intrinsic IR fingerprint selectivity, label-free ultrahigh sensitivity, and ultralow analyte volume, demonstrating a way toward quantitative molecule identification and dynamic analysis for the chemical and biological reaction processes.

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Section: Results and Discussionmentioning

confidence: 99%

Nanometer-Scale Heterogeneous Interfacial Sapphire Wafer Bonding for Enabling Plasmonic-Enhanced Nanofluidic Mid-Infrared Spectroscopy

Ren

Dong

et al. 2020

ACS Nano

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“…Figure 6 shows the HRTEM interface images of a specimen, treated with identical plasma parameters of the specimen A3, except the O 2 RIE power (50 W) and pressure (50 Pa), after annealing at 50, 100, 150, and 225 • C for 1 h in air. 18 The HRTEM images showed intermediate amorphous layers across all the interfaces. The thicknesses of the amorphous layer after annealing at 50, 100, 150, and 225 • C were 3.8, 3.4, 2.8, and 3.3 nm, respectively.…”

Section: Nanointerfacial Behavior At Low Temperaturementioning

confidence: 96%

“…The sequential activation consists of a 50-W oxygen RIE plasma with time of 60 s at 50 Pa and a 2500-W MW nitrogen radical with time of 30 s at 60 Pa 18. …”

mentioning

confidence: 99%

Comparative annealing effect on bonded wafers in air and ultrahigh vacuum for microelectromechanical systems/microfluidics packaging

Howlader

Suga

2010

J. Micro/Nanolith. MEMS MOEMS

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The fundamentals of room temperature bonding methodssurface activated bonding (SAB) and sequentially plasma-activated bonding (SPAB)-are reviewed with applications for packaging of microelectromechanical systems (MEMS) and microfluidic devices. The room temperature bonding strength of the silicon/silicon interface in the SAB and SPAB is as high as that of the hydrophilic bonding method, which requires annealing as high as 1000 • C to achieve covalent bonding. After heating, voids are not observed and bonding strengths are not changed in the SAB. In the SPAB, interfacial voids are increased and decreased the bonding strength. Water rearrangement such as absorption and desorption across the bonded interface is found below 225 • C. While voids are not significant up to 400 • C, a considerable amount of thermal voids above 600 • C is found due to viscous flow of oxides. Before heating, interfacial amorphous layers are observed both in the SAB (8.3 nm) and SPAB (4.8 nm), but after heating these disappear and enlarge in the SAB and SPAB, respectively. This enlarged amorphous layer is SiO 2 , which is due to the oxidation of silicon/silicon interface after sequential heating. The bonding strength, sealing, and chemical performances of the interfaces meet the requirements for MEMS and microfluidics applications. C 2010 Society of Photo-Optical Instrumentation Engineers.

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“…In contrast, a lower contact angle indicates a hydrophilic surface. 43 In general the demarcation line between these two surfaces is the contact angle in the ranges of 301-451. 31,44 Our results show that the contact angle for Ti electrodes is 541.…”

Section: Surface Wettability Of the Electrodesmentioning

confidence: 99%

Materials analyses and electrochemical impedance of implantable metal electrodes

Howlader

Alam

Sharma

et al. 2015

Phys. Chem. Chem. Phys.

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Implantable electrodes with high flexibility, high mechanical fixation and low electrochemical impedance are desirable for neuromuscular activation because they provide safe, effective and stable stimulation. In this paper, we report on detailed materials and electrical analyses of three metal implantable electrodes - gold (Au), platinum (Pt) and titanium (Ti) - using X-ray photoelectron spectroscopy (XPS), scanning acoustic microscopy, drop shape analysis and electrochemical impedance spectroscopy. We investigated the cause of changes in electrochemical impedance of long-term immersed Au, Pt and Ti electrodes on liquid crystal polymers (LCPs) in phosphate buffered saline (PBS). We analyzed the surface wettability, surface and interface defects and the elemental depth profile of the electrode-adhesion layers on the LCP. The impedance of the electrodes decreased at lower frequencies, but increased at higher frequencies compared with that of the short-term immersion. The increase of impedances was influenced by the oxidation of the electrode/adhesion-layers that affected the double layer capacitance behavior of the electrode/PBS. The oxidation of the adhesion layer for all the electrodes was confirmed by XPS. Alkali ions (sodium) were adsorbed on the Au and Pt surfaces, but diffused into the Ti electrode and LCPs. The Pt electrode showed a higher sensitivity to surface and interface defects than that of Ti and Au electrodes. These findings may be useful when designing electrodes for long-term implantable devices.

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Sequential Plasma-Activated Bonding Mechanism of Silicon/Silicon Wafers

Cited by 17 publications

References 28 publications

Nanometer-Scale Heterogeneous Interfacial Sapphire Wafer Bonding for Enabling Plasmonic-Enhanced Nanofluidic Mid-Infrared Spectroscopy

Nanometer-Scale Heterogeneous Interfacial Sapphire Wafer Bonding for Enabling Plasmonic-Enhanced Nanofluidic Mid-Infrared Spectroscopy

Comparative annealing effect on bonded wafers in air and ultrahigh vacuum for microelectromechanical systems/microfluidics packaging

Materials analyses and electrochemical impedance of implantable metal electrodes

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