Novel High- $Q$ MEMS Curled-Plate Variable Capacitors Fabricated in 0.35- $\mu{\hbox {m}}$ CMOS Technology
01 Feb 2008-IEEE Transactions on Microwave Theory and Techniques (Institute of Electrical and Electronics Engineers (IEEE))-Vol. 56, Iss: 2, pp 530-541
TL;DR: In this article, two microelectromechanical systems (MEMS) curled-plate variable capacitors, built in 0.35mum CMOS technology, are presented.
Abstract: Two microelectromechanical systems (MEMS) curled-plate variable capacitors, built in 0.35-mum CMOS technology, are presented. The plates of the presented capacitors are intentionally curled upward to control the tuning performance. A newly developed maskless post-processing technique that is appropriate for MEMS/CMOS circuits is also presented. This technique consists of dry-and wet-etching steps and is developed to implement the proposed MEMS variable capacitors in CMOS technology. The capacitors are simulated mechanically by using the finite-element method in ANSYS, and the results are compared with the measured results. Two novel structures are presented. The first capacitor is a tri-state structure that exhibits a measured tuning range of 460% at 1 GHz with a flat capacitance response that is superior to that of conventional digital capacitors. The proposed capacitor is simulated in Ansoft's high frequency structure simulator (HFSS) and the capacitance extracted is compared with the measured capacitance over a frequency range of 1-5 GHz. The second capacitor is an analog continuous structure that demonstrates a measured continuous tuning range of 115% at 1 GHz with no pull-in. The measured quality factor is better than 300 at 1.5 GHz. The proposed curled-plate capacitors have a small area and can be realized to build a system-on-chip.
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TL;DR: In this article, the potential applications of RF MEMS switch matrices in the satellite industry, where mass reduction and performance improvement is crucial, are described, and the benefits of MEMS technology be come more pronounced for switch matrix because there is a large number of switching elements and therefore any size and mass reduction would have large overall impact.
Abstract: Microelectromechanical systems (MEMS) technology has the potential of replacing many of the radio frequency (RF) components used in to day's satellite communication systems. In many cases, such RF MEMS components would not only substantially reduce size, weight, and power consumption, but also promise superior performance when compared to that of current technologies. The benefits of MEMS technology be come more pronounced for switch matrices because there is a large number of switching elements and, therefore, any size and mass reduction would have large overall impact. Though there has been some controversy on the reliability and lifetime of RF MEMS switches, significant improvements have been made and RF switches with billions of switching cycles have been demonstrated. This article describes the potential applications of RF MEMS switch matrices in the satellite industry, where mass reduction and performance improvement is crucial.
96 citations
TL;DR: This paper reviews CMOS (complementary metal-oxide-semiconductor) MEMS (micro-electro-mechanical systems) fabrication technologies and enabled micro devices of various sensors and actuators utilizing different physics effects and the fabrication processes introduced.
Abstract: This paper reviews CMOS (complementary metal-oxide-semiconductor) MEMS (micro-electro-mechanical systems) fabrication technologies and enabled micro devices of various sensors and actuators. The technologies are classified based on the sequence of the fabrication of CMOS circuitry and MEMS elements, while SOI (silicon-on-insulator) CMOS MEMS are introduced separately. Introduction of associated devices follows the description of the respective CMOS MEMS technologies. Due to the vast array of CMOS MEMS devices, this review focuses only on the most typical MEMS sensors and actuators including pressure sensors, inertial sensors, frequency reference devices and actuators utilizing different physics effects and the fabrication processes introduced. Moreover, the incorporation of MEMS and CMOS is limited to monolithic integration, meaning wafer-bonding-based stacking and other integration approaches, despite their advantages, are excluded from the discussion. Both competitive industrial products and state-of-the-art research results on CMOS MEMS are covered.
93 citations
TL;DR: The objective of this article is to provide RF researchers with an overview of the potential of integrating MEMS with CMOS for RF MEMS applications.
Abstract: Over the past decades, a great deal of progress has been made in the development of semiconductor manufacturing processes. This in turn has made possible the monolithic integration of microelectromechanical systems (MEMS) devices with driving, controlling, and signal processing CMOS electronics [1][4]. There have been several successful well known commercial examples of integrated MEMS-CMOS devices, including the Analog Devices ADXL accelerometers [5], the Texas Instruments digital micromirror device (DMD) [6], the STMicroelectronics accelerometers and gyroscopes [6], and SiTime vacuum-encapsulated resonators [7]. More recently, Cavendish Kinetic [8] and WiSpry [9] launched their RF MEMS switches fabricated through MEMS-CMOS integration. While several techniques for MEMS-CMOS integrations have been widely employed for sensor and accelerometer applications, most of the work reported in literatures on RF MEMS has focused on devices fabricated using conventional surface micromachining techniques. It is the objective of this article to provide RF researchers with an overview of the potential of integrating MEMS with CMOS for RF MEMS applications.
75 citations
Cites methods from "Novel High- $Q$ MEMS Curled-Plate V..."
...Post-processing of the CMOS BEOL layers [29], [31]....
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...SEM images of MEMS structures fabricated using the post-processing approach illustrated in Figure 6 [29]....
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...The University of Waterloo [28]–[29] has extended the ASIMPS process to allow the creation MEMS structures that can have vertical actuation such as parallel plate RF MEMS capacitors [29] and RF MEMS capacitive switches [30]....
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...Figure 6(a) shows the chip after the standard CMOS processing, [29]....
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...The new process [29] builds on the ASIMP’s process and adds few other steps to release metal layers in the metal/ dielectric stack....
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TL;DR: In this paper, a maskless monolithic integration process dedicated to electrostatically actuated capacitive type RF microelectromechanical systems (MEMS) switches is developed and optimized.
Abstract: The objective of this paper is to investigate the integration of capacitive type RF microelectromechanical systems (MEMS) switches in a standard CMOS technology. A maskless monolithic integration process dedicated to electrostatically actuated capacitive type RF MEMS switches is developed and optimized. The fabricated switches consist of composite metal-dielectric warped membranes. The warped-plate structure is used to increase the capacitance ratio of the switch. The switches are fabricated using the interconnect metal and dielectric layers available in a standard 0.35-μm CMOS process. Measurement results for the first switch show an insertion loss less than 0.98 dB, a return loss below 13 dB up to 20 GHz in the up-state, and a down-state isolation of 12.4-17.9 dB from 10 to 20 GHz. The capacitance ratio is enhanced up to 91:1 using the warped-plate structure. A second cascaded switch consisting of two shunt capacitive switches and a slow-wave high-impedance transmission line section is designed and fabricated for high-isolation applications. The measured insertion loss for this switch is less than 1.41 dB up to 20 GHz, the return loss is below 19 dB, and the isolation is 19-40 dB across the frequency band from 10 to 20 GHz. The proposed RF MEMS switches can be used in millimeter-wave CMOS RF front-ends where multiband functionality and reconfigurability is required.
66 citations
Cites methods from "Novel High- $Q$ MEMS Curled-Plate V..."
...CMOS RF MEMS switches are fabricated using the standard 2P4M 0.35- m CMOS process from TSMC, Taipei, Taiwan, and then post-processed by optimizing the technique previously reported by the authors for the fabrication of RF MEMS variable capacitors [ 18 ], [19]....
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27 Apr 2015
TL;DR: A tunable RF product platform based on RF-MEMS integrated within CMOS that enables programmable front-ends and early products based on that platform are presented.
Abstract: The evolution of mobile air interface standards continues to proliferate the modes and bands that must be supported in mobile devices. The mobile RF front-end has seen limited integration due to the diverse technologies required to meet the stringent performance requirements and poor scaling due to physical power and wavelength limitations. Programmable/tunable RF front-ends have been considered for many years but technologies providing sufficient performance at low cost were not available. We present a tunable RF product platform based on RF-MEMS integrated within CMOS that enables programmable front-ends and early products based on that platform.
35 citations
References
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Book•
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TL;DR: This first book to explore the computation of electromagnetic fields by the most popular method for the numerical solution to electromagnetic field problems presents a unified approach to moment methods by employing the concepts of linear spaces and functional analysis.
Abstract: From the Publisher:
"An IEEE reprinting of this classic 1968 edition, FIELD COMPUTATION BY MOMENT METHODS is the first book to explore the computation of electromagnetic fields by the most popular method for the numerical solution to electromagnetic field problems. It presents a unified approach to moment methods by employing the concepts of linear spaces and functional analysis. Written especially for those who have a minimal amount of experience in electromagnetic theory, this book illustrates theoretical and mathematical concepts to prepare all readers with the skills they need to apply the method of moments to new, engineering-related problems.Written especially for those who have a minimal amount of experience in electromagnetic theory, theoretical and mathematical concepts are illustrated by examples that prepare all readers with the skills they need to apply the method of moments to new, engineering-related problems."
6,593 citations
TL;DR: In this paper, the etch rates of 53 materials that are used or potentially can be used or in the fabrication of microelectromechanical systems and integrated circuits were prepared.
Abstract: Samples of 53 materials that are used or potentially can be used or in the fabrication of microelectromechanical systems and integrated circuits were prepared: single-crystal silicon with two doping levels, polycrystalline silicon with two doping levels, polycrystalline germanium, polycrystalline SiGe, graphite, fused quartz, Pyrex 7740, nine other preparations of silicon dioxide, four preparations of silicon nitride, sapphire, two preparations of aluminum oxide, aluminum, Al/2%Si, titanium, vanadium, niobium, two preparations of tantalum, two preparations of chromium, Cr on Au, molybdenum, tungsten, nickel, palladium, platinum, copper, silver, gold, 10 Ti/90 W, 80 Ni/20 Cr, TiN, four types of photoresist, resist pen, Parylene-C, and spin-on polyimide. Selected samples were etched in 35 different etches: isotropic silicon etchant, potassium hydroxide, 10:1 HF, 5:1 BHF, Pad Etch 4, hot phosphoric acid, Aluminum Etchant Type A, titanium wet etchant, CR-7 chromium etchant, CR-14 chromium etchant, molybdenum etchant, warm hydrogen peroxide, Copper Etchant Type CE-200, Copper Etchant APS 100, dilute aqua regia, AU-5 gold etchant, Nichrome Etchant TFN, hot sulfuric+phosphoric acids, Piranha, Microstrip 2001, acetone, methanol, isopropanol, xenon difluoride, HF+H/sub 2/O vapor, oxygen plasma, two deep reactive ion etch recipes with two different types of wafer clamping, SF/sub 6/ plasma, SF/sub 6/+O/sub 2/ plasma, CF/sub 4/ plasma, CF/sub 4/+O/sub 2/ plasma, and argon ion milling. The etch rates of 620 combinations of these were measured. The etch rates of thermal oxide in different dilutions of HF and BHF are also reported. Sample preparation and information about the etches is given.
1,256 citations
Additional excerpts
...However, unlike the two movable plate capacitors in [3], the proposed capacitors are integrated monolithically in a commercially available CMOS technology, and their plates are intentionally curled upward to control the capacitors’ tuning performance....
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29 Jan 1995
TL;DR: In this paper, the design and performance of an electrostatic actuator consisting of a laterally compliant cantilever beam and a fixed curved electrode, both suspended above a ground plane, is described.
Abstract: This paper presents the design and performance of an electrostatic actuator consisting of a laterally compliant cantilever beam and a fixed curved electrode, both suspended above a ground plane. A theoretical description of the static behavior of the cantilever as it is pulled into contact with the rigid fixed-electrode structure is given. Two models are presented: a simplified semi-analytical model based on energy methods, and fully three-dimensional (3-D) coupled electromechanical numerical simulations using CoSolve-EM. The two models are in qualitative agreement with each other, and predict stable actuator behavior when the beam deflection becomes constrained by the curved electrode geometry before electrostatic pull-in can occur. The pull-in behavior depends on the shape of the curved electrode. Test devices have been fabricated by polysilicon surface micromachining techniques. Experimental results confirm the basic theoretical results. Stable behavior with relatively large displacements and forces can be generated by these curved electrode actuators. Depending on the design, or as a result of geometrical imperfections, regions of unstable (pull-in) deflection behavior are also observed.
287 citations
"Novel High- $Q$ MEMS Curled-Plate V..." refers background in this paper
...The difference in the restoring force prevents top sections, and , from collapsing on bottom sections, and , until a dc-bias voltage is increased and a second collapse voltage point is achieved....
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11 Feb 1996
TL;DR: In this paper, self-actuating springs and nested comb-drive lateral resonators are fabricated using a 0.8/spl mu/m 3-metal CMOS process available through MOSIS.
Abstract: Electrostatically actuated microstructures with high-aspect-ratio laminated-beam suspensions have been fabricated using conventional CMOS processing followed by a sequence of maskless dry-etching steps. Laminated structures are etched out of the CMOS silicon oxide, silicon nitride, and aluminum layers. The key to the process is use of the CMOS metallization as an etch-resistant mask to define the microstructures. A minimum beam width and gap of 1.2 /spl mu/m and maximum beam thickness of 4.8 /spl mu/m are fabricated in a 0.8 /spl mu/m 3-metal CMOS process available through MOSIS. Structural features will scale in size as the CMOS technology improves. An effective Young's modulus of 63 GPa is extracted from resonant frequency measurements. Cantilevered structures slightly curl up with a radius of curvature of about 4.2 mm. Multi-conductor electrostatic micromechanisms, such as self-actuating springs and nested comb-drive lateral resonators, are successfully produced. Self-actuating springs are self-aligned multi-conductor electrostatic microactuators that are insensitive to curl. The resonance amplitude is 1 /spl mu/m for an 107 /spl mu/m-wide/spl times/109 /spl mu/m-long spring with an applied 11 V ac signal. Finite-element simulation using the extracted value for Young's modulus predicts the resonant frequency of the springs to within 6% of the measured values.
269 citations
Additional excerpts
...However, unlike the two movable plate capacitors in [3], the proposed capacitors are integrated monolithically in a commercially available CMOS technology, and their plates are intentionally curled upward to control the capacitors’ tuning performance....
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TL;DR: In this article, a 1 mm by 1 mm micromirror is made of an approximately 40 /spl mu/m-thick single-crystal silicon plate coated with aluminum from the CMOS interconnect stack.
Abstract: A micromirror achieves up to /spl plusmn/4.7/spl deg/ angular displacement with 18 Vdc by a comb-drive design that uses vertical angled offset of the comb fingers. Structures are made from a combination of CMOS interconnect layers and a thick underlying silicon layer. Electrical isolation of the silicon fingers is realized with a slight silicon undercut etch, which disconnects sufficiently narrow pieces of silicon under the CMOS microstructures. The 1 mm by 1 mm micromirror is made of an approximately 40 /spl mu/m-thick single-crystal silicon plate coated with aluminum from the CMOS interconnect stack. The mirror has a peak-to-peak curling of 0.5 /spl mu/m. Fabrication starts with a conventional CMOS process followed by dry-etch micromachining steps. There is no need for wafer bonding and accurate front-to-backside alignment. Such capability has potential applications in biomedical imaging, optical switches, optical scanners, interferometric systems, and vibratory gyroscopes.
121 citations
"Novel High- $Q$ MEMS Curled-Plate V..." refers background in this paper
...M. Bakri-Kassem was with the Center for Integrated RF Engineering (CIRFE), Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, ON, Canada N2L 3G1....
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...S. Fouladi and R. R. Mansour are with the Center for Integrated RF Engineering (CIRFE), Electrical and Computer Engineering Department, University of Waterloo, Waterloo, ON, Canada N2L 3G1 (e-mail: siamakf@mems.uwaterloo.ca; raafat.mansour@ece.uwaterloo.ca)....
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...The difference in the restoring force prevents top sections, and , from collapsing on bottom sections, and , until a dc-bias voltage is increased and a second collapse voltage point is achieved....
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