Nutapong Somjit

Power Handling Analysis of High-Power

This paper analyzes the power handling capability and the thermal characteristics of an all-silicon dielectric-block microelectromechanical-system (MEMS) phase-shifter concept, which is the first MEMS phase-shifter type whose power handling is not limited by the MEMS structures but only by the transmission line itself and by the heat-sink capabilities of the substrate, which enables MEMS phase-shifter technology for future high-power high-reliability applications. The power handling measurements of this concept are performed up to 43 dBm (20 W) at 3 GHz with an automatic gain-controlled setup, assisted by a large-signal network analyzer, and the temperature rises of the devices were measured with an infrared microscope camera. The measurement results are extended to 40 dBm at 75 GHz by calibrating electrothermal simulations with the measurements. A comparative study to conventional state-of-the-art MEMS phase-shifter concepts based on thin metallic bridges is carried out. The simulated results show that the all-silicon phase-shifter designs have the maximum temperature rise of only 30°C for 40 dBm at 75 GHz, which is 10-20 times less than conventional MEMS phase shifters of the comparable RF performance.

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In this paper, we demonstrate a novel manufacturing technology for high-aspect-ratio vertical interconnects for high-frequency applications. This novel approach is based on magnetic self-assembly of prefabricated nickel wires that are subsequently insulated with a thermosetting polymer. The highfrequency performance of the through silicon vias (TSVs) is enhanced by depositing a gold layer on the outer surface of the nickel wires and by reducing capacitive parasitics through a low-k polymer liner. As compared with conventional TSV designs, this novel concept offers a more compact design and a simpler, potentially more cost-effective manufacturing process. Moreover, this fabrication concept is very versatile and adaptable to many different applications, such as interposer, micro electromechanical systems, or millimeter wave applications. For evaluation purposes, coplanar waveguides with incorporated TSV interconnections were fabricated and characterized. The experimental results reveal a high bandwidth from dc to 86 GHz and an insertion loss of <;0.53 dB per single TSV interconnection for frequencies up to 75 GHz.

-Band All-Silicon MEMS Phase Shifters

This paper presents an overview on novel microwave micro-electromechanical systems (MEMS) device concepts developed in our research group during the last 5 years, which are specifically designed fo ...

High-Aspect-Ratio Through Silicon Vias for High-Frequency Application Fabricated by Magnetic Assembly of Gold-Coated Nickel Wires

This paper reports on design, fabrication, and characterization of a novel multistage all-silicon microwave MEMS phase-shifter concept, based on multiple-step deep-reactive-ion-etched monocrystalline-silicon dielectric blocks which are transfer bonded to an RF substrate containing a 3-D micromachined coplanar waveguide. The relative phase shift of 45° of a single stage is achieved by vertically moving the ¿/2-long blocks by MEMS electrostatic actuation. The measurement results of the first prototypes show that the return and insertion loss of a 7 × 45° of a single stage is achieved by vertically moving the ¿/2-long blocks by MEMSage phase shifter over the whole frequency spectrum from 1 to 110 GHz are better than -12 and -5.1 dB, respectively. The monocrystalline high-resistivity silicon blocks are acting as a dielectric material from an RF point of view, and at the same time as actuation electrodes for dc electrostatic actuation. The mechanical reliability was investigated by measuring life-time cycles. All tested phase shifters with three-meander 36.67-N/m mechanical spring and a pull-in voltage of 29.9 V survived 1 billion cycles after which the tests were discontinued, no indication of dielectric charging could be found, neither caused by the dielectric block nor by the Si3 N4 distance keepers to the bottom electrodes. Finally, it is investigated that, by varying the fill factor of the etch hole pattern, the effective dielectric constant of the block can be tailor made, resulting in 45°, 30°, and 15° phase-shifter stages fabricated out of the same dielectric material by the same fabrication process flow.

Microwave MEMS devices designed for process robustness and operational reliability

A novel concept of ultra-broadband multi-stage digital-type microwave MEMS phase shifters with the best performance optimized for W-band applications is introduced in this paper. The relative phase shift of 45° of a single stage is achieved by vertically moving a ¿2-long high-resistivity silicon dielectric block above a 3D micromachined coplanar waveguide (3D CPW) by electrostatic actuation, resulting in different propagation constants of the microwave signal for the up-state and the down-state. For full 360° phase-shift capability, seven stages are cascaded. The devices are fabricated and assembled by wafer-scale processes using bulk and surface micromachining. The measurement results of the first prototypes show that the W-band return and insertion loss of a single 45° stage is better than -15 dB and -1.7 dB, respectively, while the 7-stage phase shifter has a return loss better than -12 dB with an insertion loss less than -4 dB. The phase shifters also perform well from 1-110 GHz with the return loss better than -10 dB, an insertion loss of less than -1.5 dB and a fairly linear phase-shift over the whole frequency range and the actuation voltage is 30 V. To the knowledge of the authors this phase shifter is better than all previous works in term of insertion loss, return loss and phase shift per losses (°/dB) from 70-100 GHz.

Deep-Reactive-Ion-Etched Wafer-Scale-Transferred All-Silicon Dielectric-Block Millimeter-Wave MEMS Phase Shifters

Three-dimensional (3D) integration is an emerging technology that vertically interconnects stacked dies of electronics and/or MEMS-based transducers using through silicon vias (TSVs). TSVs enable the realization of devices with shorter signal lengths, smaller packages and lower parasitic capacitances, which can result in higher performance and lower costs of the system. In this paper we demonstrate a new manufacturing technology for high-aspect ratio (>;8) through silicon metal vias using magnetic self-assembly of gold-coated nickel rods inside etched through-silicon-via holes. The presented TSV fabrication technique enables through-wafer vias with high aspect ratios and superior electrical characteristics. This technique eliminates common issues in TSV fabrication using conventional approaches, such as the metal deposition and via insulation and hence it has the potential to reduce significantly the production costs of high-aspect ratio state-of-the-art TSVs for e.g. interposer, MEMS and RF applications.

Novel Concept of Microwave MEMS Reconfigurable 7X45° Multi-Stage Dielectric-Block Phase Shifter

This paper reports on phase error and nonlinearity investigation of a novel binary-coded 7-stage millimeter-wave MEMS reconfigurable dielectric-block phase shifter with best performance optimized for 75–110-GHz W-band. The binary-coded 7-stage phase shifter is constructed on top of a 3D micromachined coplanar waveguide transmission line by placing λ/2-long high-resistivity silicon dielectric blocks which can be displaced vertically by MEMS electrostatic actuators. The dielectric constant of each block is artificially tailor-made by etching a periodic pattern into the structure. Stages of 15°, 30° and 45° are optimized for 75 GHz and put into a coded configuration of a 7-stage phase shifter to create a binary-coded 15°+;30°+5×45° 7-stage phase shifter with a total phase shift of 270° in 19×15° steps. The binary-coded phase shifter shows a return loss better than −17 dB and an insertion loss less than −3.5 dB at the nominal frequency of 75 GHz, and a return loss of −12 dB and insertion loss of −4 dB at 110 GHz. The measurement results also show that the binary-coded phase shifter performs a very linear phase shift from 10–110 GHz. The absolute phase error at 75 GHz from its nominal value has an average of 2.61° at a standard deviation of 1.58° for all possible combinations, and the maximum error is 6° (for 240°). For frequencies from 10–110 GHz, all possible combinations have a relative phase error of less than 3% of the maximum phase shift at the specific frequencies. The 7-stage binary-coded phase shifter performs 71.1°/dB and 490.02°/cm at 75 GHz, and 98.3°/dB and 715.6°/cm at 110 GHz. From the measured self-modulation behavior the third-order intermodulation (IM) products level are derived to −82.35 dBc at a total input power of 40 dBm with the third-order IM intercept point (IIP3) of 49.15 dBm, employing a mechanical spring constant of 40 N/m. In contrast to conventional MEMS phase shifters which employ thin metallic bridges which limit the current handling and show fatigue even at slightly elevated temperatures, this novel phase-shifter concept is only limited by the power handling of the transmission line itself, which is proven by temperature measurements at 40 dBm at 3 GHz and skin effect adapted extrapolation to 75 GHz by electro-thermal FEM analysis.

High aspect ratio TSVs fabricated by magnetic self-assembly of gold-coated nickel wires

This paper presents three variations of novel single-stage digital passive RF MEMS phase shifters. Relative phase shift is achieved by moving a micromachined lambda/2-long dielectric block by a MEMS actuator above a 3 dimensional micromachined coplanar waveguide. The relative phase-shift of a single stage is determined by an artificially tailor-made dielectric constant of the block which is designed by a periodically etched pattern. The devices are fabricated and assembled by wafer-scale processes using bulk and surface micromachining. The measurement results show that already the first prototypes of the phase-shifter designs at the nominal frequency of 77 GHz have both in the up and in the down state a return loss better than -25 dB for 45degand 30deg phase shifter and better than -12 dB for 15deg phase-shifter with an insertion loss better than -0.9 dB at 5 GHz bandwidth. The phase shifters also perform well from 10-100 GHz with the return loss better than -10 dB, an insertion loss of less than -1.5 dB and a fairly linear phase-shift for the whole frequency range.

Phase error and nonlinearity investigation of millimeter-wave MEMS 7-stage dielectric-block phase shifters

Radio-frequency micro-electromechanical systems (RF MEMS) devices and circuits have attracted interest in applications such as car radar systems, particularly in the 76 to 81. GHz frequency band, due to their near-ideal signal performance and compatibility with semiconductor fabrication technology. This chapter gives an introduction to state-of-the-art car radar sensors and architectures, describes the most commonly engaged RF MEMS components and circuits, and gives examples of RF MEMS-based automotive radar prototypes.

Novel RF MEMS mechanically tunable dielectric phase shifter

Radio-frequency microelectromechanical systems (RF MEMS) devices and circuits have attracted interest in applications such as car radar systems, particularly in the 76-81. GHz frequency band, due t ...