Bimorph

About: Bimorph is a research topic. Over the lifetime, 3339 publications have been published within this topic receiving 51880 citations.

Integrated RF-MEMS switch based on a combination of thermal and electrostatic actuation

Abstract: We have demonstrated the feasibility of a fully integrated RF microswitch. It is based on a combination of thermal actuation and electrostatic latching hold. This method enables to combine the advantages of both actuation modes : the low voltage power supply and high reliability of the thermal actuation, and the low power consumption of the electrostatic latching. An analytical model was developed in order to predict the shape of the beam versus the temperature. An algorithm was also developed in order to evaluate the damping behavior of the switch taking the beam shape deflection into account. A design composed of a 400/spl times/50 /spl mu/m silicon nitride clamped beam was selected. The beam includes titanium nitride heating resistors, and aluminum blocks for bimorph actuation. The RF lines and the contacts are made of a 1 /spl mu/m thick gold layer. The 3 /spl mu/m air gap is fabricated using a polymer sacrificial layer. The driver of the switch, for the thermal actuation and the electrostatic latching, was manufactured in a 0.25 /spl mu/m BiCMOS technology. For each activation, the switch requires a 20 mA current under 2 V during /spl sim/200 /spl mu/s. For the electrostatic hold, the MEMS was designed for less than 10 volts. Due to residual stress in the beam material, a 5 V shift of the hold voltage has been experimentally observed on first prototypes. Reliability of thermal actuation has been tested with more than 10/sup 9/ cycles without any failure or contact degradation. Very interesting RF performances were measured, even with standard wafer (15/spl Omega/.cm) : -57 dB isolation and 0.18 dB insertion loss at 2 GHz.

A monolithic variable inductor network using microrelays with combined thermal and electrostatic actuation

Abstract: An adjustable inductor which is digitally controlled by microrelays has been made using combined surface and bulk micromaching technology. The microrelays were fabricated using a TaSi2/SiO2 bimorph cantilever beam, a gold-to-gold electrical contact, aluminum as sacrificial layer and a combined thermal and electrostatic actuation mechanism. The silicon substrate under the inductor region was etched out to reduce the parasitic oxide capacitors and the eddy current power loss in the substrate semiconductor bulk. Sixteen different inductance values ranging from 2.5 nH to 324.8 nH were obtained using a planar rectangular spiral coil and four microrelays. The minimum self-resonant frequency is 1.9 GHz. The lowest measured combined thermal power and electrostatic voltage for the actuation of microrelays are 8.0 mW and 20 V, respectively. The highest operation frequency of microrelays is 10 kHz limited by the mechanical self-resonance. The measured contact resistance typically ranges from 0.6 ohms to 0.8 ohms. The dimensions of the chip measure 3150×930 µm2.

Fabrication and test of thermal vertical bimorph actuators for movement in the wafer plane

Abstract: We have fabricated thermal actuators based on vertical bimorphs, which consist of silicon beams side-coated with aluminium. When they are heated by an electrical current they bend like a bimetal and produce movement in the wafer plane. The fabrication process is based on silicon-on-insulator substrates and uses standard silicon micromachining techniques combined with a special aluminium sidewall deposition process. The displacement has been measured as a function of the input power and the results have been compared with an FEA-simulation.

Review of Electrothermal Actuators and Applications

Abstract: This paper presents a review of electrothermal micro-actuators and applications. Electrothermal micro-actuators have been a significant research interest over the last two decades, and many different designs and applications have been investigated. The electrothermal actuation method offers several advantages when compared with the other types of actuation approaches based on electrostatic and piezoelectric principles. The electrothermal method offers flexibility in the choice of materials, low-cost fabrication, and large displacement capabilities. The three main configurations of electrothermal actuators are discussed: hot-and-cold-arm, chevron, and bimorph types as well as a few other unconventional actuation approaches. Within each type, trends are outlined from the basic concept and design modifications to applications which have been investigated in order to enhance the performance or to overcome the limitations of the previous designs. It provides a grasp of the actuation methodology, design, and fabrication, and the related performance and applications in cell manipulation, micro assembly, and mechanical testing of nanomaterials, Radio Frequency (RF) switches, and optical Micro-Electro-Mechanical Systems (MEMS).

Modelling of a cantilever non-symmetric piezoelectric bimorph

Abstract: The aim of this paper is the modelling of a non-symmetric bimorph constituted by a piezoelectric material deposited on an alumina substrate and used either as an actuator or a sensor. Theoretical modelling based on the flexural modes of the structure is carried out and the influence of the electrode characteristics (geometrical dimensions and elastic parameters) is introduced in the modelling for calculating the bimorph bending displacement. In actuator mode, the electrical admittance of the cantilever non-symmetric bimorph is stated and the intrinsic electromechanical coupling factor linked to the bimorph bending motion is deduced and compared with that defined in IEEE Standards. The analytical modelling was used for characterizing a cantilever bimorph constituted by a piezoelectric thick film deposited on an alumina substrate. A trial and error fitting method is described for determining the elastic, piezoelectric and dielectric constants of the piezoelectric material. The influence of the electrode parameters is calculated and the measurement uncertainty is deduced. In sensor mode the open voltage delivered by the bent piezoelectric layer and the electrical equivalent circuit of the bimorph are given. Theoretical results are compared with those obtained by the finite element method, and discussed.