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This paper presents a novel lateral series microwave switch fabricated on a silicon-on-insulator (SOI) substrate with a finite ground coplanar waveguide (FGCPW) configuration which is laterally actuated by the electrostatic force. The switch is built with a cantilever beam in the direction of the signal line and a fixed electrode is located opposite the cantilever beam. The mechanical structures are fabricated using SOI deep reactive ion etching (DRIE) and shadow mask technology. The fabricated lateral RF MEMS switch has an isolation of 16 dB at 20 GHz. The insertion loss of the switch is 1 dB and return loss is 15 dB at 20 GHz. The threshold voltage is 19.2 V and switching time is 30 μs.

World University root node

Department of Electrical Engineering

Analog Integrated Circuits and Signal Processing

A new approach of lateral RF MEMS switch

In this paper, a single-pole double-throw (SPDT) switching circuit that employs lateral metal-contact micromachined switches fabricated or silieon-on-insulator (SOI) wafer is demonstrated to operate from DC to 6 GHz. The size of the fabricated SPDT switch is about 1.2 mm × 1.5 mm. The lateral metal-contact micromnchined switches are formed on the quasi-finite ground coplanar waveguide (FGCPW) transmission lines and actuated by electrostatic force. The fabricated single-pole single-throw (SPST) lateral micromachined switch has an insertion loss of 0.2 dB and a return loss of 24 dB at 15 GHz. The isolation is 23 dB at 15 GHz. As for the fabricated SPDT switch, the measured insertion loss is below 0.75 dB and the return loss is higher than 19 dB at 5 GHz. The isolation at 5 GHz is above 33 dB. The threshold voltage of these switches is 22.5 volts, and these SOI switches are fabricated using deep reactive ion etching (DME) and shadow mask technology.

IEEE MTT-S International Microwave Symposium Digest

A single-pole double-throw (SPDT) circuit using deep etching lateral metal-contact switches

This paper presents a novel type of lateral series microwave switch on a silicon-on-insulator (SOI) substrate with a coplanar waveguide (CPW) configuration. It is built with a cantilever beam at the side of the gap of the microwave t-line and laterally driven by electrostatic force. The mechanical structures are made of single-crystal-silicon and fabricated by deep reactive ion etch (DRIE) technology. Evaporated aluminum serves as contact material. The fabrication process only needs one mask. The measured result shows up to 26.5 GHz the isolation of the switch is over 18 dB. The threshold voltage is about 12 volts. © 2003 IEEE.

DTIP 2003 - Design, Test, Integration and Packaging of MEMS/MOEMS 2003

An approach of lateral RF MEMS switch for high performance

Effects of trace levels of Ge transferred to Si surfaces during thermal processing of SiGe wafers are presented here. Si wafers were coprocessed in an oxidation furnace with SiGe relaxed graded buffer layers grown on Si. Total X-ray fluorescence measurements on Si wafers showed Ge concentrations in varying degrees depending on oxidation temperature, time, and the number of coprocessed SiGe wafers. The Ge concentration level increases with increase of oxidation time, temperature, and SiGe wafer quantity. It was also observed that the furnace shows "memory" of the process during subsequent process runs. A chlorine-based purge of the oxidation tube after processing SiGe wafers helps reduce the Ge concentration remarkably. Metal oxide semiconductor capacitance and gate leakage characterization were used to evaluate the effects of transferred Ge on the gate oxide. The interface state density is marginally higher on Si wafers with transferred Ge. © 2003 The Electrochemical Society. All rights reserved.

Electrochemical and Solid-State Letters

Analysis of trace levels of Ge transferred to Si wafer surfaces during SiGe wafer processing

It is shown that the LPCVD deposition technique and annealing of polysilicon effect the mechanical properties of the released structures, for micromachined sensors. Tensile residual stress is often required for a stable polysilicon MEMS structure after final release process. © 2002 IEEE.

Proceedings of the International Symposium on the Physical and Failure Analysis of Integrated Circuits, IPFA

A process technique to engineer the stress of thick doped polysilicon films for MEMS applications

Effects arising from the intercalation of excess oxygen in Bi-O layer has been observed at room temperature using atomic force microscopy. The excess oxygen is incorporated by oxygenating the pure sample. The oxygen is trapped between the alternating Bi-O layers along the b direction. This leads to a change in the local interatomic bond length along the b axis, while the periodicity remained invariant along the a axis. In addition, in-plane atomically resolved structure of single crystal has been imaged at room temperature using AFM. The lattice spacings indicate that the observed structure corresponds to the in-plane bismuth and oxygen positions. Furthermore, high-resolution scanning tunneling spectroscopy measurements show that oxygen doping increases the Bi-O layer density of states near the Fermi level giving rise to metallicity, whereas the pure sample reveals a semiconducting energy gap in the tunneling spectrum.© 1995 American Institute of Physics.

Fulltext

Applied Physics Letters

Observation of intercalation of excess oxygen in Bi2Sr 2CaCu2O8+y single crystal

Surface topography of as-grown films of YBa2Cu3O 7-delta (YBCO) deposited by off-axis RF magnetron sputtering on MgO and SrTiO3 single-crystal (100) substrates, has been investigated by scanning tunnelling microscopy (STM)/scanning tunnelling spectroscopy (STS) operated in air at ambient temperature. Both c-axis- and a-axis-oriented YBCO films have been investigated. In the case of c axis thin films, we have directly observed spiral-shaped growth terraces, which emanate from screw dislocations of this layered superconducting oxide. The growth steps are generally seen to possess a step height close to or multiples of the unit cell height of the YBCO crystalline structure. In the case of a axis growth, the substrate as well as the deposition temperature determines the grain orientation. Furthermore, our STS data revealed that the surface layer of the film is semiconducting and the tunnelling spectrum varies its shape depending on the tip-to-sample distance. A superconducting gap appears clearly in the spectra when the STM tip is placed closer to the surface than the normal position of the scanning mode. This suggests that the semiconducting layer is confined in the topmost surface region of the as-prepared film, while the layer beneath it is superconducting in character.

Superconductor Science and Technology

The effect of sputter deposition conditions on the growth mechanism of YBa2Cu3O7-delta thin films studied by scanning tunnelling microscopy

In this article, recent results employing scanning tunneling microscopy-based techniques for the generation of nanometer-scale patterns on hydrofluoric acid treated silicon(100) and YBa2Cu3O x superconducting thin films are presented. Furthermore, we were able to extract silicon (Si) atoms from Si(100)-1×1 surfaces, thereby producing silicon vacancies in the surface. These results thus demonstrate a possible approach for the construction of an atomic scale data memory as well as fabrication of artificial nucleation sites. The emission mechanism is believed to be field assisted evaporation due to the close proximity of the surface and the probe of the microscope. © 1995 American Institute of Physics.

Journal of Applied Physics

Pattern generation on silicon surfaces and YBa2Cu 3Ox thin films by a scanning tunneling microscope

A thermodynamic criterion has been applied to determine the reliability of contact metals such as silver, aluminium, gold, chromium, and titanium on bismuth and yttrium based high temperature superconductors (HTSC). The chemical stability is presumed for positive heat of reactions, i.e., ΔHreaction &gt; 0, when a metal reacts with all the possible oxides present in the superconducting material. Based on these calculations, metals for reliable contacts to HTSCs are proposed. © 1994.

Microelectronics Reliability

Reliability of high temperature superconductor metal contacts

X-ray photoemission measurements were performed on Au deposited on a Bi(2212) single crystal after progressively sputtering it with Ar ions. This was to see whether changes such as diffusion of Au, segregation of a particular element or clustering effects take place at the interface. Spectra of different core levels reveal no elemental diffusion at the interface and an absence of Au interaction with the crystal at room temperature.

A photoemission study of the influence of sputtering on the Au-Bi(2212) interface

The paper reports a new approach, based on low-pressure on-axis sputter deposition followed by high-pressure plasma treatment (OPT) for the preparation of in situ superconducting Bi-Sr-Ca-Cu-O (BSCCO) films with a high-Tc phase. It was observed that OPT is essential to lower the room-temperature resistance and to achieve superconduction in the films.

A new approach for the preparation of in situ superconducting BSCCO films

This work investigates the effect of Bragg’s reflector configuration stages and its material on the performance of flexible FBAR sensor. Bragg’s reflector configuration has been formed with various high and low acoustic Impedance layers such as Mo/SiO2, W/SiO2, and W/Al. The detailed investigation of flexible FBAR sensor has been done using 2-D finite element method (FEM) simulations performed on COMSOL Multiphysics software. Acoustic impedance versus frequency and frequency versus quality factor plots were drawn for the detailed investigation of material and number of Bragg’s reflector configuration stages on the performance of the flexible FBAR sensor. The comparative results for various Bragg’s reflector configurations have been summarized and reported. It is reported that spurious modes were present while using even number of stages to form Bragg’s reflector configuration. Thus, to remove spurious harmonic modes odd number of Bragg’s reflector configuration stages are required. The present work also states that W/SiO2-based Bragg’s reflector configurations are best suited to achieve enhanced performance in terms of enhanced coupling coefficient and figure of merit. This investigation offers new framework for the design of a flexible FBAR sensor with high performance.