Low temperature bonding techniques for MEMS devices
17 Dec 2015-pp 1-4
TL;DR: In this article, low temperature and low cost bonding techniques with commercially available epoxy 320 NC and photoresist SU-8 2010 are done, which gave good shear strength, as measured with an indigenous setup.
Abstract: Conventional bonding techniques like fusion, glass frit, soldering, eutectic, and anodic bonding, have been used in packaging for micro-electro-mechanical systems (MEMS). These bonding techniques require high temperature which results in bending/buckling of MEMS devices especially in case of hanging structures. In this work, low temperature and low cost bonding techniques with commercially available epoxy 320 NC and photoresist SU-8 2010 are done. Bonding with commercially available epoxy 320 NC at room temperature leads to spreading of epoxy in device region and affects the device performance. To define bonding ring dimensions, photoresist SU 8 2010 is used as an adhesive. Sharp dimensions of SU 8 2010 bonding ring are achieved using lithography. Top silicon cap is fabricated using TMAH etching. The bonds made with these techniques gave good shear strength, as measured with an indigenous setup.
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01 May 2017
TL;DR: In this article, an ultra-thin, low-cost 3D glass sensor packaging platform for nearhermeticity with novel feedthrough and encapsulation technologies is described, where glass panels of thicknesses ranging from 50 µm to 300 µm are used which limits overall form factor to 10 MPa.
Abstract: This paper describes an ultra-thin, low cost 3D glass sensor packaging platform for near-hermeticity with novel feedthrough and encapsulation technologies. Glass panels of thicknesses ranging from 50 µm to 300 µm are used which limits overall form factor to 10 MPa) and Dow Chemical's Benzocyclobutene (BCB) 14-P005 is found to be the best candidate for panel level glass-glass bonding. Modelling of the proposed three-layer glass packaging platform was performed in COMSOL Multiphysics. Results show a maximum deformation of about 2.3 µm - 2.5 µm in the BCB and GX-92 bonded package and the least average internal stress of 6.40 MPa in the BCB bonded package. The complete manufacturing cycle starting from cavity formation on bare glass to final 3D assembly to form the lidded/open cavity package including singulation is panel based, enabling significant cost reduction (depending on die dimensions and panel size) compared to ceramic and other substrate technologies.
6 citations
Cites background from "Low temperature bonding techniques ..."
...Specifically, adhesive bonding using a range of polymers like BCB, SU8 PR, S1818 [23-28] has also been explored, but at high temperatures with limited efficiency....
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01 Aug 2020
TL;DR: In this paper, a review of the state of the art in the field of RF-MEMS package for nearly past twenty years is presented, focusing on the wafer-level packaging of RF MEMS switch and comparing different methods of wafer level packaging.
Abstract: Compared with traditional switches, RF MEMS switches are characterized by low power consumption, low insertion loss, high isolation, good linearity and high integration. However, the high cost of packaging process has great impact on the device performance among the RF MEMS processing. This paper overviews the research status of RF MEMS switch, such as the structural design, the wafer-level packaging. The review will focus on the wafer-level packaging of RF MEMS switch and the following conclusions are drawn by comparing the different methods of wafer level packaging: 1) The packaging of RF MEMS switches mainly adopts WLP methods, which are divided into two types, cap packaging and thin film packaging. Thin film packaging is more promising due to it presenting a lower temperature than cap packaging. 2) The low temperature bonding technology is used in the cap packaging for RF MEMS switch, and the cap packaging has gradually matured. 3) The sacrificial layer release technique is needed in the thin film packaging, and the contamination problem caused by clean technology in the packaging process still needs to be solved. 4) As cap materials or sealing ring materials, polymer is a low-temperature encapsulation material, which has great development potential. But, it is too sensitive to humidity, and it still need a deeper study. The reviews are presented to get a better understanding of the state of the art work done in the field RF-MEMS package for nearly past twenty years.
3 citations
Cites background from "Low temperature bonding techniques ..."
...Among them, BCB [29,32], SU-8 [24,39], PerMX [40] are more extensive....
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...Cap materials are mainly LTCC [31], BCB [32], SiO2 [24,30], Si [23,25-28], and sealing ring materials are mainly Au [23,31], BCB[29,32], SU-8[24], SiO2 [25], polyimide polymer[28]....
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References
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TL;DR: In this paper, the authors concentrate on electrostatic switches at 0.1-100 GHz with high reliability (100 million to 10 billion cycles) and wafer-scale manufacturing techniques.
Abstract: MEMS switches are devices that use mechanical movement to achieve a short circuit or an open circuit in the RF transmission line. RF MEMS switches are the specific micromechanical switches that are designed to operate at RF-to-millimeter-wave frequencies (0.1 to 100 GHz). The forces required for the mechanical movement can be obtained using electrostatic, magnetostatic, piezoelectric, or thermal designs. To date, only electrostatic-type switches have been demonstrated at 0.1-100 GHz with high reliability (100 million to 10 billion cycles) and wafer-scale manufacturing techniques. It is for this reason that this article will concentrate on electrostatic switches.
1,066 citations
TL;DR: In this paper, a new process is described which permits the sealing of metals to glass and other insulators at temperatures well below the softening point of the glass, by applying a dc voltage in excess of a few hundred volts between the glass and the metal in such a way that the former is at a negative potential with respect to the latter.
Abstract: A new process is described which permits the sealing of metals to glass and other insulators at temperatures well below the softening point of the glass. Sealing is accomplished in about 1 min by applying a dc voltage in excess of a few hundred volts between the glass and the metal in such a way that the former is at a negative potential with respect to the latter. The process has been applied to a number of glass‐metal combinations. A discussion is presented of some of the mechanisms which are believed to play a role in the bonding process.
800 citations
"Low temperature bonding techniques ..." refers background in this paper
...These bonding processes require high temperature, low roughness and external pressure for proper bonding such as conventional silicon-to-silicon fusion bonding requires high temperature close to 1000°C for bonding energy and surface roughness less than 10nm for intimate contact [11]....
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TL;DR: In this paper, the construction and performance of metal membrane radio frequency MEMS switches at microwave and millimeter-wave frequencies was described. But the authors focused on the performance of the switches in terms of on-off capacitance ratio.
Abstract: 'This letter details the construction and performance of metal membrane radio frequency MEMS switches at microwave and millimeter-wave frequencies. These shunt switches possess a movable metal membrane which pulls down onto a metal/dielectric sandwich to form a capacitive switch. These switches exhibit low loss (<0.25 dB at 35 GHz) with good isolation (35 dB at 35 GHz). These devices possess on-off capacitance ratios in the range of 80-110 with a cutoff frequency (figure of merit) in excess of 9000 GHz, significantly better than that achievable with electronic switching devices.
474 citations
"Low temperature bonding techniques ..." refers methods in this paper
...MEMS devices have already been successfully demonstrated [3-5]....
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TL;DR: In this article, the packaging and assembly challenges of micro-opto-electro-Mechanical (MOEMS) and MEMS for different applications are discussed. But, the authors do not address the issues and challenges facing the assembly of MOEMS.
Abstract: Although MEMS technologies and device structures have made significant progress in the past three decades and have found widespread application in many areas, including Micro-Opto-Electro-Mechanical Systems (MOEMS), packaging and assembly techniques suitable for many of these emerging applications have not kept pace. Packaging is one of the most costly parts of microsystem manufacturing, and it is also often the first to fail or negatively influence the system response. This paper addresses the packaging and assembly challenges of microsystems and MEMS for different applications. Hermetic and vacuum micropackaging, wafer-level packaging and bonding, and miniature sealed interconnection and feedthrough technologies will be reviewed. Results from long-term accelerated testing, and from in-situ tests, especially in biological hosts, will also be discussed. Issues and challenges facing packaging of MOEMS will be discussed.
170 citations
"Low temperature bonding techniques ..." refers background in this paper
...Packaging contributes more than 70% of the device cost [1]....
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...Over last two decades research work has been concentrated on MEMS switch design and fabrication [1]-[8]....
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...Therefore MEMS packaging tends to be customized to the specific application, with emphasis on the cost, performance and reliability [1]....
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TL;DR: Silicon fusion bonding (SFB) is the joining together of two silicon wafers without the use of intermediate adhesives as mentioned in this paper, which has been used to fabricate silicon-on-insulator (SOI) substrates and silicon power devices, and also has wide applications in the fabrication of silicon sensors, actuators and other microstructures.
Abstract: Silicon fusion bonding (SFB) is the joining together of two silicon wafers without the use of intermediate adhesives. The technology has been used to fabricate silicon-on-insulator (SOI) substrates and silicon power devices, and also has wide applications in the fabrication of silicon sensors, actuators and other microstructures. This paper reviews the development and current status of SFB. A history of the technology from the early 1960s to the present is presented. Process techniques necessary to incorporate SFB successfully into silicon micromachining processes are discussed, and examples of successful SFB structures are presented. Comparisons to competing techniques are made, and the potential for future development of SFB structures is discussed. Silicon fusion bonding presents major new possibilities in the design of silicon micromachined structures when combined with other available processing techniques. SFB has already been used in novel accelerometers, high-temperature pressure sensors, ultraminiature pressure sensors and high over-range pressure sensors. SFB does not appear to be the technique of choice for VLSI SOI technology, but it is highly viable for use in silicon microstructures, and it is incumbent on the micromachining community to pursue further development of the technology. With the development of ‘smart’ power devices occurring in parallel with the development of ‘smart’ sensors, it is to be hoped that evolution of SFB for both microstructures and power devices will continue and will provide cross-fertilization between the two fields.
152 citations