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Design of multi-actuation RF MEMS switch using CMOS process
Abstract
This work demonstrates a capacitive RF (radio frequency) MEMS (micro-electromechanical systems) switch, which is actuated by electro-thermal force and electrostatic force at the same time, and than latching the switching status by electrostatic force only. Since thermal actuator need relative low voltage compare to electrostatic actuator, for electrostatic force need almost no power to maintain the switching status. The benefit of this mechanism is very low actuation voltage and low power consumption. This RF MEMS switch has considered the issues for integrated circuit compatible including process and package between MEMS device and IC (integrated circuit). So it fabricated by standard 0.35 mum 2P4M (double polysilicon four metal) CMOS (complementary metal oxide semiconductor) process and then post- processed by wet etching. The structure of the switch consists of a set of CPW (coplanar waveguides) transmission lines and a suspended membrane. Both the CPW and the membrane are the metal layers in CMOS structure. Besides, electro-thermal actuators are designed by polysilicon layer because of the higher resistance than metal. So one of the main advantages of the RF switch is only CMOS process layers are needed for both electro-thermal and electrostatic actuations in switch. Moreover, the bimorph thermal actuator is designed by a stacked step structure including two metal layers, so no additional MEMS processes are needed. Measured results show that the actuation voltage of the switch is around 7 V. The insertion loss of the RF switch in the "ON" state is -2.5 dB at 5 GHz, and the isolation of the "OFF" state is -4.1 dB relatively.
... This can avoid the high-power consumption issue in an electrothermal actuator as well as high-voltage issue in an electrostatic actuator [14][15][16][17]. Previously, a similar concept has been used in [18][19][20][21]: these designs utilize electrothermal actuators to bring the switch contacts near to signal lines and then hold the switches in ON state with electrostatic actuation. In another attempt, the switches are also integrated with electrostatic and electromagnetic actuation to achieve similar advantages [22,23]. ...
In this paper, we report a novel laterally actuated Radio Frequency (RF) Microelectromechanical Systems (MEMS) switch, which is based on a combination of electrothermal actuation and electrostatic latching hold. The switch takes the advantages of both actuation mechanisms: large actuation force, low actuation voltage, and high reliability of the thermal actuation for initial movement; and low power consumption of the electrostatic actuation for holding the switch in position in ON state. The switch with an initial switch gap of 7 µm has an electrothermal actuation voltage of 7 V and an electrostatic holding voltage of 21 V. The switch achieves superior RF performances: the measured insertion loss is −0.73 dB at 6 GHz, whereas the isolation is −46 dB at 6 GHz. In addition, the switch shows high reliability and power handling capability: the switch can operate up to 10 million cycles without failure with 1 W power applied to its signal line.
... The power consumption is 3.24 µJ. Similar work can be found in [144][145][146][147][148]. The actuation voltage and power consumption of these multi-drive switches are both decreased. ...
MEMS switch is a movable device manufactured by means of semiconductor technology, possessing many incomparable advantages such as a small volume, low power consumption, high integration, etc. This paper reviews recent research of MEMS switches, pointing out the important performance indexes and systematically summarizing the classification according to driving principles. Then, a comparative study of current MEMS switches stressing their strengths and drawbacks is presented, based on performance requirements such as driven voltage, power consumption, and reliability. The efforts of teams to optimize MEMS switches are introduced and the applications of switches with different driving principles are also briefly reviewed. Furthermore, the development trend of MEMS switch and the research gaps are discussed. Finally, a summary and forecast about MEMS switches is given with the aim of providing a reference for future research in this domain.
The electronic and mechanical characteristic of RF
MEMS switches depends significantly on the structure of the
switch. This article proposes new optimized architectures for
cantilevered beam RF MEMS switches. The modeling approach
is based on nodal analysis to solve coupled non-linear differential
equations that describe the electromechanical system using
Matlab toolbox for MEMS called SUGAR. The model used
SUGAR to calculate; netlist of a cantilever beam subjected to an
external force, Static analysis of deflection, display of structure
and displacement values. The switching voltage of mentioned
construction for MEMS switches is determined and analyzed at
different geometrical parameters. The results investigate the
geometrical parameters of the five MEMS architectures that
control the switching voltage to achieve a maximum frequency
response for the switch at lower driving voltage. The structure of
the proposed cantilever type MEMS switches indicates that the
switch can operate with driving voltage of 4.2 V with maximum
switching frequency of 6.65 GHz.
This paper introduces a use of special design MEMS used as low insertion loss sample and hold (S/H) circuit, replacing the GaAsFET switch with MEMS switch. The use of electrostatic MEMS switches is attractive because of its advantages, such as very low power consumption, low insertion loss and high isolation. The introduced MEMS switch is capable to perform at high speed, since it does not include transistor in its structure, insertion loss in the case of GaAsFET switch is −10.506 dB while its value in the case of MEMS switch is −.086 db at 20GHZ, the proposed circuit have insertion loss reduction 99.2%.
In this paper a quasi-floating-gate charge/discharge method is presented and a novel application for the widely used membrane-like RF-MEMS switches is proposed as well. The design of a four-beam capacitive MEMS structure is described within the 0.5 microns (2P3M) CMOS technology framework. Furthermore, the device is electromechanically simulated in the COMSOL Multiphysics suite and electrically simulated via a custom SPICE model. Finally, the possible use as an electromechanical switch to provide an initial desired electric potential to the floating gate in a flotating-gate MOS transistor (FGMOS) device is discussed.
A four stage model to analyze an AC (alternating current) MEMS (micro-electro-mechanical systems) cantilever switch separated with the DC (direct current) electrode is presented. By using the model to analyze the switch it is found that the position of the signal line not only affects the capacitance between the signal line and the membrane in the switch, but also affects the normal operation of the switch under a stable voltage. Because the applied voltage will decrease at the fourth stage, the switch will be at an unstable state this stage. Aiming at this unstable phenomenon of the switch a design idea to the critical position of the signal line is presented, which is based on the requirement that the applied maximum voltage be equal to the voltage responding to the maximum capacitance ratio in certain position of the signal line. In the example, the relationship between the position of the electrode and the position of the signal line, the relationship between the position of the electrode and the applied maximum voltage, and the relationship between the position of the electrode and the maximum capacitance ratio are computed.
This article introduced Trade-Off is taken as a new measure for MEMS switching to select the most probable frequency - voltage dependence for cantilevered beam RF MEMS switches. The switching voltage of the mentioned structures for MEMS switches is determined and analyzed at different geometrical parameters. The results investigate the geometrical parameters of the eight MEMS structures that control the switching voltage to achieve a maximum frequency response for the switch at lower driving voltage
A complementary metal-oxide semiconductor (CMOS)-compatible, capacitive, shunt-type radio frequency MEMS switch design is demonstrated. The switch is actuated by an electrothermal actuator and an electrostatic actuator at the same time, and the switching status is latched by electrostatic force only. Since thermal actuators require a lower voltage than electrostatic actuators, and since an electrostatic force can maintain switching status with virtually no power, the benefits of the mechanism are a very low actuation voltage and low power consumption. The switch is fabricated by a standard 0.35 - μ m 2P4M CMOS process. The movable membrane can be released by either wet or dry postprocessing etching technologies. The design’s CMOS-process compatibility is important because radio frequency (RF) characteristics are determined not just by the device itself. The design can minimize parasitic capacitance when a packaged RF switch and a packaged IC are wired together. The switch contains a set of coplanar waveguide transmission lines and a suspended membrane. The CPW lines and the membrane are contained in the metal layers of the CMOS process. The electrothermal actuators are contained in the polysilicon layer. Only standard CMOS process layers are needed for both the electrothermal and electrostatic actuations in the RF switch. The measurement results show that the electrothermal or electrostatic actuation requires less than 7 V .
The capacitive type of radio frequency micro-electromechanical systems (RF MEMS) switch is investigated for low driving voltages and low power consumption. The RF MEMS switch is actuated by electro-thermal forces and electrostatic forces at the same time, and then held the status by electrostatic forces only after driving. We also use complementary metal oxide semiconductor (CMOS) technology to integrate MEMS devices and integrated circuits (ICs) into a monolithic chip. The RF MEMS switch is fabricated using standard CMOS process, double poly-silicon four metal (2P4M), and the wet etching of MEMS fabrication is then used for post-processed. Experimental results show that the both actuation mechanisms, electro-thermal and electrostatic forces, are workable. The pull-in voltage of the switch for driving is about 7 volts. The insertion loss and the isolation of RF switch at a frequency of 5 GHz are 2.5 dB and 1.6 dB, respectively.
An innovative parallel gap bistable switch is demonstrated, based on a nickel-plating process with a polymer mold. It combines two different actuator mechanisms to yield extremely low steady state power consumption: thermal actuation is used for the stroke movement, whereas electrostatic actuation is used to latch the on state. This makes it useful for low-power applications where continuous thermal drive is not possible. Strokes of 20 μm can be achieved, with thermal actuation power of 1 W during the switching movement. In a second stage, the position can be electrostatically held with a voltage of 15 V, requiring no further power. The actuator's size is approximately 1.5 mm2.
This article reviews the fundamental characteristics of
micromechanical membrane switches operating at microwave frequencies.
The construction and theory of operation of capacitive membrane switches
is reviewed. Measurement and modeling of the electromechanical and
microwave properties of these switches are presented. The inherent
advantages of these switches relative to semiconductor switches is
discussed
This paper deals with a relatively new area of radio-frequency
(RF) technology based on microelectro-mechanical systems (MEMS). RF MEMS
provides a class of new devices and components which display superior
high-frequency performance relative to conventional (usually
semiconductor) devices, and which enable new system capabilities. In
addition, MEMS devices are designed and fabricated by techniques similar
to those of very large-scale integration, and can be manufactured by
traditional batch-processing methods. In this paper, the only device
addressed is the electrostatic microswitch - perhaps the paradigm
RF-MEMS device. Through its superior performance characteristics, the
microswitch is being developed in a number of existing circuits and
systems, including radio front-ends, capacitor banks, and time-delay
networks. The superior performance combined with ultra-low-power
dissipation and large-scale integration should enable new system
functionality as well. Two possibilities addressed here are
quasi-optical beam steering and electrically reconfigurable antennas
A microelectromechanical microwave switch manufactured by using a complementary metal oxide semiconductor (CMOS) post-process has been implemented. An equivalent circuit model is proposed to analyze the performance of the microwave switch. The components of the microwave switch consist of a coplanar waveguide (CPW), a suspended membrane and supported springs. The post-process requires only one wet etching to etch the sacrificial layer, and to release the suspended structures. Experimental results show that the switch has an insertion loss of −2 dB at 50 GHz and an isolation of −15 dB at 50 GHz. The driving voltage of the switch approximates to 19 V.
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
`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
Addressing reconfiguration of radio frequency (RF) systems might require high performance integrated RF switching capabilities. In this regard, a particular design experience of an integrated circuit (IC) monolithically integrated microelectromechanical systems (MEMS) ohmic switch is reported here. Applications at 2 GHz have been targeted. The MEMS device was processed on top of a 0.25-μm standard BiCMOS wafer including the switch IC driver. An extensive RF characterization has been made. The switch exhibits at 2 GHz a 0.18-dB insertion loss and a 57-dB isolation level. This realization opens the way to further designs of reconfigurable architectures for multiband and multistandard mobile terminals.
Performance of low-loss RF MEMS capacitive switches Figure 1. Capacitance-Voltage curve of electro-thermal IEEE Microwave Guided Wave Lett
- C L Goldsmith
- Z Yao
- S Eshelman
- D Denniston
C.L. Goldsmith, Z. Yao, S. Eshelman, and D. Denniston, "Performance of low-loss RF MEMS capacitive switches," Figure 1. Capacitance-Voltage curve of electro-thermal IEEE Microwave Guided Wave Lett., vol. 8, pp. 269-271, Aug. actuation 1998.
Without an applied voltage, there is no electrostatic force, and the and P. AnceyAn Above IC MEMS RF Switch IEEE membrane of the RF switch stays in the up position. The RF signal Journal ofSolid-State Circuits
- D Saias
- P Robert
- S Boret
- C Billard
- G Bouche
- D Belot
D. Saias, P. Robert, S. Boret, C. Billard, G. Bouche, D. Belot, Without an applied voltage, there is no electrostatic force, and the and P. Ancey, "An Above IC MEMS RF Switch," IEEE membrane of the RF switch stays in the up position. The RF signal Journal ofSolid-State Circuits, VOL. 38, NO. 12, Dec. 2003. via CPW does not couple to membrane theoretically. The RF switch is called in "on" state, and the S-parameter S21 means insertion loss.
Capacitance-Voltage curve of electrostatic actuation
Figure 10. Capacitance-Voltage curve of electrostatic actuation
[3] Gabriel M. Rebeiz, RFMEMS Theory, Design, and Technology,
John Wiley and Sons, 2003.
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RF MEMS Theory, Design, and Technology