Low-loss lateral micromachined switches for high frequency applications
01 Jan 2005-Journal of Micromechanics and Microengineering (IOP Publishing)-Vol. 15, Iss: 1, pp 157-167
TL;DR: In this article, two novel lateral metal-contact radio-frequency microelectromechanical system (RF MEMS) switches are reported, implemented with quasi-finite ground coplanar waveguide (FGCPW) configuration and actuated by applying electrostatic force on a high-aspect-ratio cantilever beam.
Abstract: Two novel lateral metal-contact radio-frequency microelectromechanical system (RF MEMS) switches are reported. These switches are implemented with quasi-finite ground coplanar waveguide (FGCPW) configuration and actuated by applying electrostatic force on a high-aspect-ratio cantilever beam. It is demonstrated that the insertion loss of the switch is less than 0.2 dB up to 15 GHz and the isolation is higher than 20 dB up to 25 GHz. An RF model of the switches is used to analyse the effects of the switch design parameters and RF performance. The optimization of the switch mechanical design is discussed where the threshold voltage can be lower than 25 V. The lateral switches are fabricated by deep reactive ion etching (DRIE) process on a silicon-on-insulator (SOI) wafer with shadow mask technology.
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TL;DR: In this paper, the Euler-Bernoulli equation was used for the miniaturization of flexural beams used in electromechanical devices, and it was shown that the utilization of structural materials with high strain limit, in conjunction with innovations in processes and structures, will be needed to scale nanoelectromechanical systems beam lengths into the sub-100 nanometer regime.
Abstract: Limitations for the miniaturization of flexural beams used in electromechanical devices are examined using the numerical analysis of the Euler-Bernoulli equation. The utilization of structural materials with high strain limit, in conjunction with innovations in processes and structures, will be needed to scale nanoelectromechanical systems beam lengths into the sub-100 nanometer regime.
20 citations
TL;DR: In this article, a dc 6 GHz single-pole double-throw (SPDT) switching circuit that employs lateral metal-contact micromachined switches is investigated, which consists of a set of quasi-finite ground coplanar waveguide (FGCPW) transmission lines and a high-aspect-ratio cantilever beam.
Abstract: A dc 6 GHz single-pole double-throw (SPDT) switching circuit that employs lateral metal-contact micromachined switches is investigated. The lateral metal-contact switch consists of a set of quasi-finite ground coplanar waveguide (FGCPW) transmission lines and a high-aspect-ratio cantilever beam. A single-pole single-throw (SPST) lateral micromachined switch has an insertion loss of 0.08 dB and a return loss of 32 dB at 5 GHz. The isolation is 32 dB at 5 GHz. The measured insertion loss of the SPDT switching circuit is below 0.75 dB, whereas the return loss is higher than 19 dB at 5 GHz. The isolation at 5 GHz is 33 dB. Pull-in voltage of the switch is 23.3 V and switching time is 35 μs. The size of the SPDT switching circuit is 1.2 mm × 1.5 mm. A main advantage of this circuit structure is simple fabrication process with high yield (>90%) based on the deep reactive ion etching (DRIE) technique of silicon-on-insulator (SOI) wafer and shadow mask technology.
20 citations
Cites background from "Low-loss lateral micromachined swit..."
...Recently, lateral switches have also been studied [9–11]....
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TL;DR: In this article, an undoped polysilicon isolation structure was proposed to provide mechanical coupling and electrical isolation between the actuator and the contacts in a thermal actuated lateral switch.
Abstract: The lateral actuated switch requires an isolation structure to provide mechanical coupling and electrical isolation between the actuator and the contacts. This isolation structure usually imposes extra difficulty on the fabrication process. In previous reports, we demonstrated a thermal actuated lateral switch, where the nitride isolation structure was a weak point, leading to reliability problems. In this paper, we developed a modified switch utilizing undoped polysilicon as the isolation material. The undoped-polysilicon isolation structure requires only one extra step of sheltered implantation, and it provides robust mechanical connection. A 20-mum-long undoped-polysilicon isolation structure has a current leakage of less than 2 nA under a 15-V operation voltage. The proposed switch works under a 12-V driving voltage with 60-mW input power. The time response is measured to be 130 mus, and a maximum operation frequency of 4.5 kHz is reached. An ON-state insertion loss of -0.41 dB at 20 GHz and an OFF-state isolation of -20 dB at 20 GHz have been achieved on the normal low-resistivity silicon substrate. The undoped-polysilicon isolation method can be used in other surface-micromachined lateral switches as well.
19 citations
Cites background from "Low-loss lateral micromachined swit..."
...Various actuation approaches are also investigated, including the electrothermal actuation [2]–[4], the electrostatic actuation [8], the piezoelectric actuation [9], and the electromagnetic actuation [10]....
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17 Dec 2009
TL;DR: In this article, the pull-in effect of an electrostatically actuated beam to achieve abrupt switching behavior in the nanoelectro-mechanical field effect transistor (NEMFET) was investigated.
Abstract: : Increasing power density is a daunting challenge for continued MOSFET scaling due to non-scalability of the thermal voltage kBT/q. To circumvent this CMOS power crisis and to allow for aggressive supply voltage reduction alternative switching device designs have been proposed and demonstrated to achieve steeper than 60mV/dec subthreshold swing (S). This dissertation begins with a general overview of the physics and operation of these MOSFET-replacement devices. It then applies circuit-level metrics to establish evaluation guidelines for assessing the promise of these alternative transistor designs. This dissertation then investigates the abrupt "pull-in" effect of an electrostatically actuated beam to achieve abrupt switching behavior in the nanoelectro-mechanical field effect transistor (NEMFET). To facilitate low-voltage NEMFET design, the Euler-Bernoulli beam equation is solved simultaneously with the Poisson equation in order to accurately model the switching behavior of a NEMFET. The impact of various transistor design parameters on the gate pull-in voltage and release voltage are examined. A unified pull-in/release voltage model is developed. Finally, this dissertation proposes the use of micro-relays for zero-standby-power digital logic applications. To mitigate the contact reliability issue, it is demonstrated that since relatively high on-state resistance can be tolerated while extremely high endurance is a necessity, hard contacting electrode materials and operation with low contact force are preferred for reliable circuit operation. Using this contact design approach, a reliable relay technology that employs titanium dioxide (TiO2) coated tungsten (W) electrodes is developed for digital logic applications.
18 citations
TL;DR: In this article, a novel electrochemically assisted wet-etching method for maskless selective removal of metal layers is presented, which has been successfully applied for the fabrication of transmission lines with integrated microswitches, lowering the insertion loss of the waveguide at 10 GHz from 1.3 to 0.3 dB/mm.
Abstract: This paper presents a novel electrochemically assisted wet-etching method for maskless selective removal of metal layers. This method has been developed as the key process step for enabling the fabrication of low-loss 3-D micromachined silicon-on-insulator-based radio-frequency microelectromechanical systems transmission line components, consisting of a silicon core in the device layer covered by a gold metallization layer. For this application, the full-wafer sputtered metallization layer must be locally removed on the handle layer to guarantee for a well-defined and low-loss coplanar-waveguide propagation mode in the slots of the transmission line. It is not possible to use conventional photolithography or shadow masking. Gold areas to be etched are biased by a 1.2-V potential difference to a saturated calomel reference electrode in a NaCl(aq) solution. The measured etch rate of the proposed local electrochemically biased etching process is 520 nm/min, and no detectable etching was observed on unbiased areas even after a 1-h etch. The suitability of different adhesion layers has been investigated, and Ti-based adhesion layers were found to result in the highest yield. The new etching method has been successfully applied for the fabrication of transmission lines with integrated microswitches, lowering the insertion loss of the waveguide at 10 GHz from 1.3 to 0.3 dB/mm. The issue of unwanted thin metallic connections caused by secondary deposition during sputtering is discussed but found not to significantly affect the process yield. Finally, local removal of gold on isolated features even within the device layer is presented for locally removing the metallization on stoppers of laterally moving electrostatic actuators, to drastically reduce the mechanical wear on stopper tips.
17 citations
Cites background from "Low-loss lateral micromachined swit..."
...Micromachined transmission lines in silicon-on-insulator (SOI) have been demonstrated for switches [6], and the authors of this paper have demonstrated coplanar-transmission-lineembedded mechanically multi-stable single-pole-double-throw switch mechanisms [7], [8], as shown in Fig....
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References
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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-loss lateral micromachined swit..." refers background in this paper
...Most of the reported MEMS switches are vertical motion switches, including the fixed–fixed beam switch [1], cantilever beam switch [2], toggle switch [3] and push–pull switch [4]....
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TL;DR: In this paper, the authors evaluate the potential of using high-resistivity silicon as a low-cost low-loss microwave substrate through an experimental comparative study and demonstrate that the losses of a coplanar transmission line (CPW) realized on high resistivity (3 k to 7 k /spl Omega/-cm) silicon substrates are comparable to the losses realized on a GaAs substrate covered with insulators.
Abstract: Silicon has many advantages as a microwave substrate material including low cost and a mature technology. The aim of this paper is to evaluate the potential of using high-resistivity silicon as a low-cost low-loss microwave substrate through an experimental comparative study. Coplanar waveguides fabricated on Si, GaAs, and quartz substrates are tested and their characteristics are compared. Microwave spiral inductors and meander lines are also fabricated on various substrates, and their performance is also analyzed. The results demonstrate that the losses of a coplanar transmission line (CPW) realized on high-resistivity (3 k to 7 k /spl Omega/-cm) silicon substrates are comparable to the losses of a CPW realized on a GaAs substrate covered with insulators. Furthermore, measured unloaded Q's of microwave inductive structures on high-resistivity silicon substrates are comparable to the measured unloaded Q's of the same structures on GaAs and on quartz. This paper demonstrates that high-resistivity Si can be used as a microwave substrate. >
171 citations
"Low-loss lateral micromachined swit..." refers background in this paper
...High resistivity (HR) silicon (Si) has been studied as a substrate material for communication system applications at microwave and millimetre wave frequencies for its mature fabrication process, low cost and acceptable RF performance [13]....
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11 Jun 2000
TL;DR: In this article, a push-pull type microwave switch is proposed, which utilizes torsion springs and leverage for lowvoltage operation, and the actuation voltage is /spl sim/5 V.
Abstract: In this paper, a push-pull type microwave switch is proposed, which utilizes torsion springs and leverage for low-voltage operation. The switching operation up to 4 GHz is demonstrated. The actuation voltage is /spl sim/5 V. The insertion loss of /spl sim/1 dB and the isolation as high as /spl sim/40 dB at 1 GHz are achieved by the push-pull operation.
138 citations