Umer Shah

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

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.

Microwave MEMS devices designed for process robustness and operational reliability

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 ...

Multi-position large tuning-range digitally tuneable capacitors embedded in 3D micromachined transmission lines

This paper reports for the first time on multi-position RF MEMS digitally tuneable capacitors with large tuning range which are integrated inside a coplanar transmission line and whose tuning is achieved by moving the sidewalls of the 3D micromachined transmission line, with the actuators being completely embedded and shielded inside the ground layer. Devices with symmetrical two and three-stage actuators have been fabricated in an SOI RF MEMS process. A tuning range of Cmax/Cmin=2.41 with a total of 7 discrete tuning steps from 44 to 106 fF was achieved for the three-stage tuneable capacitors. The symmetrical integration in the transmission line and a low parasitic inductance result in a high resonance frequency of 77 GHz. Devices with actuator designs of different mechanical stiffness, resulting in actuation voltages of 16 to 73 V, were fabricated and evaluated. The robustness of the actuator to high-power signals has been investigated by a nonlinear electromechanical model, which shows that self actuation occurs for high-stiffness designs (73 N/m) not below 50 dBm, and even very low-stiffness devices (9.5 N/m) do not self-actuate below 40 dBm.

500–750 GHz submillimeter-wave MEMS waveguide switch

This paper presents a 500-750 GHz waveguide based single-pole single-throw (SPST) switch achieving a 40% bandwidth. It is the first ever RF MEMS switch reported to be operating above 220 GHz. The switch is based on a MEMS-reconfigurable surface which can block the wave propagation in the waveguide by short-circuiting the electrical field lines of the TE10 mode. The switch is designed for optimized isolation in the blocking state and for optimized insertion loss in the non-blocking state. The measurement results of the first prototypes show better than 15 dB isolation in the blocking state and better than 3 dB insertion loss in the non-blocking state for 500-750 GHz. The higher insertion loss is mainly attributed to the insufficient metal thickness and surface roughness on the waveguide sidewalls. Two switch designs with different number of blocking elements are fabricated and compared. The overall switch bandwidth is limited by the waveguide only and not by the switch technology itself.

500–600 GHz submillimeter-wave 3.3 bit RF MEMS phase shifter integrated in micromachined waveguide

This paper presents a 500-600 GHz submillimeter-wave MEMS-reconfigurable phase shifter. It is the first ever RF MEMS component reported to be operating above 220 GHz. The phase shifter is based on a micromachined rectangular waveguide which is loaded by 9 E-plane stubs, which can be individually blocked by using MEMS-reconfigurable surfaces. The phase-shifter is composed of three metallized silicon chips which are assembled in H-plane cuts of the waveguide. The measurement results of the first prototypes of the MEMS reconfigurable phase shifter show a linear phase shift of 20° in 10 steps (3.3 bit) and have a return loss better than 15 dB from 500-600 GHz. The insertion loss is better than 3 dB up to 540 GHz, and better than 5 dB up to 600 GHz for all phase states, of which the major part is contributed by the assembly of the microchips between waveguide flanges which has a reproducibility error between 2 and 6 dB measured for reference chips.

Permeability Enhancement by Multilayer Ferromagnetic Composites for Magnetic-Core On-Chip Inductors

This letter reports about unpatterned ferromagnetic NiFe/AlN multilayer composites used as advanced magnetic core materials for on-chip and interposer integrated inductances. The proposed composite structure reduces RF induced currents and thus pushes the permeability cutoff to beyond 3.7 GHz, which is by a factor of 7.1 higher than for homogeneous NiFe layers of same thickness. To the best knowledge of the authors, we achieve the highest effective relative permeability of 28 at 1 GHz, highest ferromagnetic resonance frequency and highest inductance enhancement factor above 1 GHz ever reported for devices based on on-chip unpatterned NiFe magnetic cores. A single loop inductor is also implemented as a technology demonstrator, achieving an inductance enhancement of 4.8 and a quality factor enhancement of 4.5 at 400 MHz.

MEMS reconfigurable millimeter-wave surface for V-band rectangular-waveguide switch

This paper presents for the first time a novel concept of a microelectromechanical systems (MEMS) waveguide switch based on a reconfigurable surface, whose working principle is to block the wave pr ...

500-600 GHz RF MEMS based tunable stub integrated in micromachined rectangular waveguide

This paper presents a 500-600 GHz switchable Eplane waveguide stub tuned MEMS device. It is the first ever RF MEMS component reported to be operating above 220 GHz. The micromachined E-plane stub can be blocked/unblocked from the micromachined waveguide by using a MEMS-reconfigurable surface. The surface is designed so that in the blocking state it is in the H-plane and comprises the roof of the main waveguide, whereas in the non-blocking state it comprises a transmissive Eplane surface for the stub. The measurement results of the first prototypes show a return loss better than 15 dB from 500-600 GHz. The insertion loss is better than 3 dB up to 550 GHz, and better than 4 dB up to 600 GHz. The switchable stub can be utilized as a basic reconfigurable device for tuning/matching of waveguide components under operation; the implemented prototype switchable stub achieves a (measured) tuning of 2.5° at 500 GHz, with a change in S21 better than 0.15 dB for the whole band. The paper further shows that the reconfigurable stub can also be operated in analog tuning mode. This paper also demonstrates that MEMS-reconfigurable E-plane surfaces can be designed and operated deep into the submillimeter-wave frequency range.

Millimeter-wave SPST Waveguide switch based on reconfigurable MEMS surface

This paper presents a concept of a waveguide single-pole single-throw (SPST) switch based on a MEMS-reconfigurable surface. A set of vertical columns, split into two groups of movable and fixed sections which can be actuated laterally by integrated MEMS comb-drive actuators, allows for the transition between the transmissive and the blocking state. In the totally-blocking state, the vertical columns inhibit the wave propagation by short-circuiting the electrical field lines of the predominant TE10 mode. The paper reports on the integration method for fabricated chips into a WR-12 waveguide by using tailor-made flanges. The RF measurement of fabricated chips show that devices have better than 30 dB isolation in the OFF state and better than 0.65 dB insertion loss in the ON state for 60-70 GHz, which is mainly attributed to the integration into the waveguide and the measurement assembly setup. The actuation voltage is 44 V, and life-time measurements were carried out for 14 hours after which 4.3 million cycles were achieved without any indication on degradation.

Multi-Position RF MEMS Tunable Capacitors Using Laterally Moving Sidewalls of 3-D Micromachined Transmission Lines

This paper presents a novel concept of RF microelectromechanical systems (MEMS) tunable capacitors based on the lateral displacement of the sidewalls of a 3-D micromachined coplanar transmission line. The tuning of a single device is achieved in multiple discrete and well-defined tuning steps by integrated multi-stage MEMS electrostatic actuators that are embedded inside the ground layer of the transmission line. Three different design concepts, including devices with up to seven discrete tuning steps up to a tuning range of 58.6 to 144.5 fF