MetalMUMPs Process Research Articles

The study of a high-isolation single-pole-double-throw RF MEMS switch

In this paper, design, fabrication and measurements of a novel single-pole-double-throw three-state RF MEMS switch based on silicon substrate are presented. The RF MEMS switch consists of two UV-shaped beam push–pull thermal actuators which have three states of ON, OFF and Deep-OFF by using current actuation. When the switch is at Deep-OFF state, it can provide a higher isolation. The switch is fabricated by MetalMUMPs process. The measurement results show that, to the proposed single-pole-double-throw RF MEMS switch, when Switch I is at the ON state and Switch II is at the OFF state, the return loss is better than −16 dB, the insertion loss of Port1 and Port2 is less than −0.9 dB and the isolation of Port3 and Port1 is better than −22 dB at the frequency range from 8 GHz to 12 GHz. When Switch I is at the ON state and the actuator of Switch II is pulled back, which is called the Deep-OFF state, the return loss of Port1 is better than −15.5 dB, the insertion loss of Port1 and Port2 is better than −0.8 dB, and the isolation of Port3 and Port1 is better than −23.5 dB can be achieved at the frequency range from 8 GHz to 12 GHz.

A low loss and power efficient micro-electro-thermally actuated RF MEMS switch for low power and low loss applications

A novel laterally and micro-electro-thermally actuated RF MEMS switch is presented in this paper. Despite many RF MEMS switches requiring continuous actuation voltage to hold the switch at ON-state, the proposed switch remains ON without any DC power. The mechanical design of the switch is in such a way that, the contact force of the switch is in mN range with zero DC power consumption. The switch is modeled and its operation is comprehensively analyzed. The fabrication process is completely compatible with standard MetalMUMPs process. The switch requires actuation voltages of 0.5 and 0.9 V for U-shaped and V-shaped actuators, respectively. The switch is normally OFF with isolation of ý 20 dB up to 100 GHz. The insertion loss of the switch at ON-state is better than ý 0.1 dB up to 40 GHz and the return loss is below ý 10 dB up to 100 GHz. The power consumption of the switch is confined to the transition time of the switch between OFF and ON states. Based on analytical and numerical simulations, the contact resistance of the switch is 0.028 ý. The proposed switch in this paper is dedicated for applications in mobile front-ends especially antenna switch networks where the signal loss and power consumption are the main constraints.

Single-chip 3D electric field microsensor

This paper presents a single-chip 3D electric field microsensor, in which a sensing element is set at the center to detect the Z-axis component of an electrostatic field. Two pairs of sensing elements with the same structure are arranged in a cross-like configuration to measure the X- and Y-axis electrostatic field components. An in-plane rotary mechanism is used in the microsensor to detect the X-, Y-, and Z-axis electrostatic field components simultaneously. The proposed microsensor is compact and presents high integration. The microsensor is fabricated through a MetalMUMPS process. Experimental results show that in the range of 0–50 kV/m, the linearity errors of the microsensor are within 5.5%, and the total measurement errors of the three electrostatic field components are less than 14.04%.

Wide bandwidth 2-DoF electromagnetic MEMS energy harvester for low g applications

This paper presents the design of a 2-DoF electromagnetic MEMS energy harvester, optimized to be realized using commercially available microfabrication processes. The proposed 2-DoF system consists of two inter-connected vibrating masses to achieve dynamically amplified displacement amplitude, at low-frequency and low-g vibrations with wide operational bandwidth. The vibrating microstructure, with sputtered NdFeB magnets, is designed considering microfabrication constraints of MetalMUMPs process. The stationary planar microcoils are designed using 0.35 μm CMOS MIMOS process. The vibrating microstructure and stationary planar microcoils are bonded together using photoresist with thickness of 30 μm. The magnets are arranged in a Halbach array configuration to concentrate the magnetic field on the stationary microcoils side while cancelling the field nearly zero on the other side. The input acceleration value with respect to overall damping is optimized, for a structurally limited gap of 160 μm between the inner and outer mass of the 2-DoF vibrating system, using design of experiments (DOE) based response surface models. For the proposed design, two resonant frequencies of 40.7 and 89.6 Hz are obtained with an operational bandwidth of 49 Hz. With an input acceleration value of 0.442g, an induced voltage of 18 mV and output power of 0.82 nW is btained at the first resonant frequency while an induced voltage of 14 mV and output power of 0.54 nW is obtained at the second resonant frequency. The normalized power density of the proposed energy harvester design is 7.94 ? 10ź7 (W/cm3/g2) at 40.7 Hz, with an overall device volume of 0.0058 cm3.

ZnO on nickel RF micromechanical resonators for monolithic wireless communication applications

On-chip integrability of high-Q RF passives alongside CMOS transistors is crucial for the implementation of monolithic radio transceivers. One of the most significant bottlenecks in back-end-of-line (BEoL) integration of MEMS devices on CMOS processed wafers is their relatively low thermal budget, which is less than that required for typical MEMS material deposition processes. This paper investigates electroplated nickel as a structural material for piezoelectrically-transduced resonators to demonstrate ZnO-on-nickel resonators with a CMOS-compatible low temperature process for the first time. Aside from the obvious manufacturing cost benefit, electroplated nickel is a reasonable substitute for polycrystalline or single crystal silicon and thin-film microcrystalline diamond device layers, while realizing decent acoustic velocity and moderate Q. Electroplated nickel has been already adopted by MEMSCAP, a multi-user MEMS process foundry, in its MetalMUMPs process. Furthermore, it is observed that a localized annealing process through Joule heating can be exploited to significantly improve the effective mechanical quality factor for the ZnO-on-nickel resonators, which is still lower than the reported AlN resonators. This work demonstrates ZnO-on-nickel piezoelectrically-actuated MEMS resonators and resonator arrays by using an IC compatible low temperature process. There is room for performance improvement by lowering the acoustic energy losses in the ZnO and nickel layers.

A Micro-Test Structure for the Thermal Expansion Coefficient of Metal Materials

An innovative micro-test structure for detecting the thermal expansion coefficient (TEC) of metal materials is presented in this work. Throughout this method, a whole temperature sensing moveable structures are supported by four groups of cascaded chevrons beams and packed together. Thermal expansion of the metal material causes the deflection of the cascaded chevrons, which leads to the capacitance variation. By detecting the capacitance value at different temperatures, the TEC value of the metal materials can be calculated. A finite element model has been established to verify the relationship between the TEC of the material and the displacement of the structure on horizontal and vertical directions, thus a function of temperature for different values of TEC can be deduced. In order to verify the analytical model, a suspended-capacitive micro-test structure has been fabricated by MetalMUMPs process and tested in a climate chamber. Test results show that in the temperature range from 30 °C to 80 °C, the TEC of the test material is 13.4 × 10−6 °C−1 with a maximum relative error of 0.8% compared with the given curve of relationship between displacement and temperature.

A push-pull double-contact MEMS relay fabricated by MetalMUMPs process

This document presents a push-pull double-contact MEMS (Micro ElectroMechanical System) relay. The MEMS relay is electrostatic driven and laterally actuating. Two push-pull structures form two parallel contacts for the proposed MEMS relay, which can make the contact resistance of the MEMS relay be smaller. The push and pull actions of the push-pull actuators can be accomplished simultaneously using only one action signal. In addition, high inductance DC bias line and substrate removal are used for additional electrical and/or thermal isolation. The fabrication of the proposed switch is based on the standard MetalMUMPs process. The measured pull-in voltage is 116 V and the switch-ON delay is 44 μs. Contact resistance of the MEMS relay is less than 1 Ω when the stress voltage exceeds 120 V.

A Reconfigurable Microwave Equalizer With Different Maximum Attenuations Based on RF MEMS Switches

The design, fabrication, and measurements of a novel reconfigurable microwave equalizer based on RF micro-electro-mechanical system (MEMS) switches for adjusting the maximum attenuations of microwave signals are presented in this letter. The reconfigurable equalizer is driven by four lateral dc-contact RF MEMS switches, which can select the different attenuation resistances and obtain various maximum attenuations compared with the traditional microwave equalizer with fixed maximum attenuation. The proposed reconfigurable equalizer is fabricated by MetalMUMPs process. The experimental results show that the reconfigurable equalizer can realize four maximum attenuations of 7, 6.6, 5.9, and 5.6 dB by the actuation of RF MEMS switches, the reflection losses are all below -16 dB at the frequency range from 17 to 19 GHz, the experimental results agree well with the theory.

A Compliant MEMS Device for Out-of-Plane Displacements With Thermo-Electric Actuation

A MEMS actuator for micrometric displacements in the out-of-plane direction is proposed in this paper. The device is based on a compliant micromechanism composed of a thick layer of nickel and two thin layers of silicon nitride ensuring displacements in the out-of-plane direction. Its actuation is thermo-electrically performed, the polysilicon resistor encapsulated between the two thin silicon nitride layers is heated by Joule effect; the obtained thermo-mechanical deformation is therefore converted into an out of plane displacement thanks to the compliant mechanism realized in the device structure. The behavior of the device has been analytically modeled through the pseudo-rigid body model methodology and simulated with finite elements models in order to study and optimize its performance. The results coming from the presented models and the device operation have been experimentally validated by characterizing a prototype of this device micro-fabricated in the MetalMUMPs process from MEMSCAP. The maximum displacement of the device is ~16 μm with a maximum actuation voltage of 90 V and the maximum exerted force is ~17 mN.

Versatility provided by electrostatic torsional microstructure as consequence of its complex dynamics

The results presented show that a simple microstructure involving a plate supported by two tethers can exhibit varied dynamics due to its nonlinearities. The plate vibrates such that the tethers experience a torsional twisting and it is designed within the constraints imposed by the MetalMUMPs process. Each region of operation has different applications and one can traverse through these regions by adjusting the sensing and actuation voltages. As one would expect, the nonlinearities dominate at higher voltages, with the first signs of chaotic trajectories appearing at 75 V. Parameters of the nonlinear model are first determined from finite-element analysis responses, and results from subsequent numerical simulations for each region are presented.

A Novel Three-State RF MEMS Switch for Ultrabroadband (DC-40 GHz) Applications

Design, fabrication, and measurement results of a lateral dc-contact RF microelectromechanical systems switch for ultrabroadband applications are presented in this letter. The switch is driven by a bidirectional cascaded electrothermal actuator, which can generate larger displacements and contact forces at two directions than traditional electrothermal actuators. Because of this bidirectional actuator, the proposed switch can not only realize the off-state to on-state shifting, but also provide an additional deep off-state. The proposed switch is fabricated by MetalMUMPs process, and measurement results show that the insertion loss is less than -0.5 dB and the initial isolation is better than -22.5 dB at 0-40 GHz range. At the deep off-state, the isolation better than -30 dB can be achieved at the whole frequency range 0-40 GHz. The measurement results agree well with the theory and design.

A Novel Bidirectional Z-Shaped Thermally Actuated RF MEMS Switch for Multiple-Beam Antenna Array

In this paper RF MEMS switchis designed for dielectric-embedded electronically switched multiple-beam (DE-ESMB) antenna array. To achieve small stiffness without buckling, a novel bidirectional Z-shaped thermal actuator is used instead of V-shaped thermal actuator, which can generate large displacement and high contact force at low actuation voltage. With the actuation current from-0.6 A to 0.6 A, the electrothermal actuator can achieve a bidirectional motion in a dynamic range of-10.08 μm to 10.17 μm.RF performances are improved by suspending the structure 25 μm from the substrate using MetalMumps process. An ON state insertion loss of-0.14 dB at 10 GHz and an OFF state isolation of-67 dB at 10 GHz are achieved on low resistivity silicon substrate.

Design Optimization of MEMS Based LLC Tunable Resonant Converter for Power Supplies on Chip

In this paper, a novel MEMS based LLC converter is proposed for on chip power supplies. The design is optimized based on commercially available Metal MUMPs process for fabrication. The resonant frequency is optimized at 20MHz and MEMS based variable capacitor is fabricated on the chip to tune the peak resonance frequency of circuit which varies due to the load variations. The Design is simulated in FEM based numerical software COMSOL and Intellisuite. According to analysis the magnetizing inductance of 42nH and leakage inductance of 40nH has been achieved from 16 mm2 rectangular coil transformer. The total capacitance of 1500pF has been achieved from parallel plate capacitors and variation of 3pF has been achieved from variable capacitor.

Design and Characterization of a Fully Differential MEMS Accelerometer Fabricated Using MetalMUMPs Technology

This paper presents a fully differential single-axis accelerometer fabricated using the MetalMUMPs process. The unique structural configuration and common-centriod wiring of the metal electrodes enables a fully differential sensing scheme with robust metal sensing structures. CoventorWare is used in structural and electrical design and simulation of the fully differential accelerometer. The MUMPs foundry fabrication process of the sensor allows for high yield, good process consistency and provides 20 μm structural thickness of the sensing element, which makes the capacitive sensing eligible. In device characterization, surface profile of the fabricated device is measured using a Veeco surface profilometer; and mean and gradient residual stress in the nickel structure are calculated as approximately 94.7 MPa and −5.27 MPa/μm, respectively. Dynamic characterization of the sensor is performed using a vibration shaker with a high-end commercial calibrating accelerometer as reference. The sensitivity of the sensor is measured as 0.52 mV/g prior to off-chip amplification. Temperature dependence of the sensing capacitance is also characterized. A −0.021fF/°C is observed. The findings in the presented work will provide useful information for design of sensors and actuators such as accelerometers, gyroscopes and electrothermal actuators that are to be fabricated using MetalMUMPs technology.

Fatigue Degradation Properties of LIGA Ni Films Using Kilohertz Microresonators

A micrometer-scale ultrasonic fatigue characterization technique is introduced to investigate the fatigue degradation properties of LIGA Ni structural films in the very high cycle fatigue regime. Kilohertz microresonators fabricated with the MetalMUMPs process were driven at resonance (~ 8 kHz) in controlled environments (30 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C , 50% relative humidity (RH); 80 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C, 5% RH; and 80 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C, 90% RH) to perform fatigue tests on 20-μm -thick Ni notched beams subjected to fully reversed bending over a wide range of stress amplitudes. It is shown that the fatigue degradation occurring at the notch, observed with scanning electron microscopy, can be quantified with the measured evolution of the microresonators' resonant frequency. The fatigue damage consists of extrusion formation and microcrack nucleation and does not propagate to form fatal cracks due to the extreme stress gradients at the notch. The resonant frequency evolution for fatigue tests performed at 80 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C, 90% RH suggests that stress-assisted oxidation in the presence of humid environments may accentuate fatigue damage formation. This experimental technique brings critical information regarding the long-term fatigue degradation properties of metallic microelectromechanical systems (MEMS) devices. In particular, this technique can allow controlled studies of the effects of fatigue localization and large stress gradients typically encountered in MEMS components.

Continuously tunable terahertz metamaterial employing a thermal actuator

In order to increase the flexibility of the resonance frequency, a widely and continuously tunable terahertz metamaterial structure that employs a thermal actuator for tuning the resonance frequency of a two-cut split-ring resonator is proposed in this paper. The tunable metamaterial device model is designed and simulated based on the MetalMUMPs process. The use of V-shaped thermal actuators enables continuous tuning of the resonance frequency over a large range from 1.374 to 1.574 THz. The transmission curves have a sharp dip in every resonance frequency, which indicates an excellent performance of strong resonance. The geometrical parameters of the V-shaped thermal actuator are optimized by COMSOL Multiphysics 4.2 in order to obtain enough displacement under minimum driven current. The relationship between driven current and slabs' displacement is also characterized. The reliability of the metamaterial structure array actuated by the thermal actuator is also calculated and discussed.

A MEMS Doubly Decoupled Gyroscope With Wide Driving Frequency Range

This study developed a microelectromechanical systems (MEMS) doubly decoupled gyroscope with a wide driving frequency range. The gyroscope increases the resonance bandwidths of both the drive and sense oscillators without sacrificing their Q factors. This bandwidth enhancement ensures good frequency matching between the drive and sense oscillators even if fabrication imperfections are present. Additionally, no in-operation frequency tuning mechanism is needed. The gyroscope can be driven at any frequency within the overlapping region of the resonance bands of the drive and sense oscillators. Experiments showed that the gyroscope driving voltage can be of any frequency within a ~240-Hz bandwidth. The wide bandwidth provides flexibility and ease of use. The device is fabricated by the MetalMUMPs process developed by MEMSCAP, Inc. Its doubly decoupled structure minimizes the interference/coupling between the drive and sense units. Performance tests under rotation rates equal to or smaller than 18.71 rad/s showed that the gyroscope has a sensitivity of 4.28 mV/(rad/s).

Bidirectional Electrothermal Actuator With Z-Shaped Beams

A bidirectional micro-actuator powered by electrothermal force is successfully demonstrated under both dc and ac operations, without the assistance of magnetic field, using MetalMUMPs process. To achieve small stiffness without buckling, which tends to occur in V-shaped actuators, a new Z-shaped electrothermal actuator is designed. With the actuation current from -13 mA to +13 mA, the electrothermal actuator can achieve a bidirectional motion in a dynamic range from -11.6 μm to +12.8 μm. Experimentally obtained frequency response of the actuator indicates that it has a bandwidth of 49 Hz.

Mechanically Amplified 3-DoF Nonresonant Microelectromechanical Systems Gyroscope Fabricated in Low Cost MetalMUMPs Process

This paper introduces the design implementation of 3-DoF Microelectromechanical Systems (MEMS) based gyroscope concept, which allows shaping up the dynamic response without using advance control system strategies, with less compromise in performance. The proposed architecture utilizes an active–passive mass configuration in order to achieve the dynamic amplification of the oscillation in 2-DoF drive-mode. A comprehensive theoretical description, dynamics, and mechanical design configuration of the proposed gyroscope design are discussed in detail. A complete test methodology has also been devised for the proposed nonresonant 3-DoF gyroscope. A cost effective commercially available metal-multi user MEMS process is used to fabricate a 20 μm thick nickel based micromachined vibratory gyroscope with an overall chip size of 2.2 mm × 2.6 mm. A good agreement is found between the tested and the simulated results. The experimental characterization demonstrated that the wide bandwidth frequency response of the 2-DoF drive-mode oscillator consists of two resonant peaks at 754 Hz and 2.170 kHz, respectively, with a flat region of 1.4 kHz between the peaks, defining the operational frequency region. The sense-mode resonant frequency lies within this region at 1.868 kHz allowing the amplitude of the response to be insensitive to structural parameter and damping variations, with improved robustness against such variations. The passive mass achieved a dynamic amplification of three times at first resonant peak of 754 Hz and five times at the second resonant peak of 2.170 kHz in comparison with the active mass, resulting in improved sensitivity in response to the Coriolis torque induced due to rotation.

Behavioral modeling of a monolithically integrated three-axis capacitive accelerometer based on the MetalMUMPs process

In this paper we present behavioral modeling of a monolithically integrated three-axis capacitive accelerometer using the standard MetalMUMPs process. The behavioral modeling is done in order to verify the design with respect to structural and electrostatic performance of the designed three-axis capacitive accelerometer. The proposed accelerometer is 3.2 mm × 3.5 mm in size, designed for sensing the acceleration of 25 g in three axes. The mechanical noise floor for in-plane ( x and y) and out-of-plane ( z) axes is 0.291, 0.316, and 2.84 µ g/√ (Hz), respectively. The total sense capacitance along the x, y, and z axes is 68.5 fF, 100 fF, and 6.19 pF, respectively. Sensitivity of 2.568 fF/ g, 4 fF/ g, and 0.252 pF/ g is obtained for in-plane ( x and y) and out-of-plane ( z) axes, respectively. The resonance frequency for the designed accelerometer is 800 and 2500 Hz for in-plane and out-of-plane axes, respectively. The results obtained by behavioral modeling are compared with the analytical results, which are approximately the same.