The influence of residual stress induced by anodic wafer bonding on MEMS membrane properties (original) (raw)
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Sensors
Die attach is a typical process that induces thermal stress in the fabrication of microelectromechanical system (MEMS) devices. One solution to this problem is attaching a portion of the die to the package. In such partial die bonding, the lack of control over the spreading of the adhesive can cause non-uniform attachment. In this case, asymmetric packaging stress could be generated and transferred to the die. The performance of MEMS devices, which employ the differential outputs of the sensing elements, is directly affected by the asymmetric packaging stress. In this paper, we proposed a die-attach structure with a pillar to reduce the asymmetric packaging stress and the changes in packaging stress due to changes in the device temperature. To verify the proposed structure, we fabricated four types of differential resonant accelerometers (DRA) with the silicon-on-glass process. We confirmed experimentally that the pillar can control the spreading of the adhesive and that the asymmet...
Wafer-level SLID bonding for MEMS encapsulation
Advances in Manufacturing, 2013
Hermetic packaging is often an essential requirement to enable proper functionality throughout the device's lifetime and ensure the optimal performance of a micro electronic mechanical system (MEMS) device. Solid-liquid interdiffusion (SLID) bonding is a novel and attractive way to encapsulate MEMS devices at a wafer level. SLID bonding utilizes a low-melting-point metal to reduce the bonding process temperature; and metallic seal rings take out less of the valuable surface area and have a lower gas permeability compared to polymer or glassbased sealing materials. In addition, ductile metals can adopt mechanical and thermo-mechanical stresses during their service lifetime, which improves their reliability. In this study, the principles of Au-Sn and Cu-Sn SLID bonding are presented, which are meant to be used for wafer-level hermetic sealing of MEMS resonators. Seal rings in 15.24 cm silicon wafers were bonded at a width of 60 lm, electroplated, and used with Au-Sn and Cu-Sn layer structures. The wafer bonding temperature varied between 300°C and 350°C, and the bonding force was 3.5 kN under the ambient pressure, that is, it was less than 0.1 Pa. A shear test was used to compare the mechanical properties of the interconnections between both material systems. In addition, important factors pertaining to bond ring design are discussed according to their effects on the failure mechanisms. The results show that the design of metal structures can significantly affect the reliability of bond rings.
Low temperature silicon wafer bonding for MEMS applications
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Abstract This paper reports the investigation of low-temperature silicon wafer fusion bonding for MEMS applications. A bonding process utilizing annealing temperatures between 400 C and 1100 C was characterized. The silicon-silicon bonded interface was analyzed by Infrared Transmission (IT) and Transmission Electron Microscopy (TEM) and the bond strength was quantified by a four-point bending-delamination technique
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Technical Digest. MEMS 2002 IEEE International Conference. Fifteenth IEEE International Conference on Micro Electro Mechanical Systems (Cat. No.02CH37266), 2002
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Wafer bonding - A powerful tool for MEMS
Wafer bonding techniques play a key role in the present day silicon bulk micromachining for MEMS based sensors and actuators. Various silicon wafer bonding techniques and their role on MEMS devices such as pressure sensors, accelerometers and micropump have been discussed. The results on the piezoresistive pressure sensors monolithically integrated with a MOSFET differential amplifier circuit have been presented to demonstrate the important role played by the Silicon Fusion Bonding technique for integration of sensors with electronics on a single chip.
Effect of Process Variables on Glass Frit Wafer Bonding in MEMS Wafer Level Packaging
MRS Proceedings, 2008
Among different MEMS wafer level bonding processes glass frit bonding provides reliable vacuum tight seals in volume production. The quality of the seal is a function of both seal glass materials and the processing parameters used in glass frit bonding. Therefore, in this study Taguchi L18 screening Design of Experiment (DOE) was used to study the effect of materials and process variables on the quality of the glass seal in 6” silicon wafers bonded in EVG520IS bonder. Six bonding process variables at three levels and two types of sealing glass pastes were considered. The seals were characterized by Scanning Acoustic Microscopy (SAM), cross sectional Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX). The results were quantified into four responses for DOE analysis. Key results are a) peak temperature has the strongest influence on seal properties, b) hot melt paste has significantly lower defects compared to liquid paste, and c) peak firing temperatures c...
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Wafer bonding techniques are key technologies for MEMS devices fabrication. Anodic bonding is a very mature technique used for wafers stacking or wafer level packaging. This paper reports results on a process allowing Glass - Si - Glass and Si - Glass - Si triple-stacks bonding in a single process step. The process is performed at a temperature of 420°C by applying a voltage of maximum 600 V. The benefits of such a process will be detailed.
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2013 14th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE), 2013
A three-scale approach to thermo-compression, metallic wafer bonding is here presented. The approach focuses on the purely mechanical side of the process, identifying three different length-scales: the macro-scale, at which the whole wafer is considered, to define the average contact pressure within each single die; the mesoscale, at which the aforementioned average pressure at the die level is applied to the MEMS bonding ring, to study stress diffusion in it; and the micro-scale, at which a micro-mechanically informed morphology of a representative volume of the two metallic rings in contact is considered along with their surface roughness, to get insights into local features of the sealing. The proposed approach can describe local effects due to a space-varying pressure, and can help to enhance and speedup the design phase of the bonding rings.