ESD failure signature in capacitive RF MEMS switches

RF MEMS are commonly known as electrostatic devices using high electric field for their actuation. They can be exposed to transient voltages in any environment, and are very sensitive. According to this point of view, it is necessary to understand and analyze the degradations and failure criteria that can make them useless or reduce their lifetime. This paper deals with the investigation of ESD failure signature in capacitive RF MEMS. ESD experiments were carried out using a transmission line pulsing technique. It has been observed that electrical discharges give rise to sparks or electrical arcing and induced DC parameter shift, which can directly lead to changes in RF metrics. The contact-less dielectric charging effects of ESD pulses have been reported in this paper. It has been found that induced charges are predominant compared to injected ones through the trend of slope of the shift in the voltage corresponding to the minimum of capacitance.     

Structure dependent charging process in RF MEMS capacitive switches

The paper investigates the dependence of charging process on the dielectric charging of radiation induced defects in Si₃N₄ and SiO₂ dielectric films, which are used in RF-MEMS switches. The radiation has been performed with 5 MeV alpha particles. The assessment has been carried out in Metal-Insulator-Metal capacitors with the thermally stimulated depolarization currents and discharge current transient methods. This allowed monitoring the defects introduction as a function of radiation fluence. The defects electrical characteristics that are the activation energy and corresponding depolarization time constant were determined from the evolution of the thermally stimulated current spectra and the transient response of discharge currents at different temperatures.     

Alpha particle radiation effects in RF MEMS capacitive switches

The paper investigates the effect of 5 MeV alpha particle irradiation in RF MEMS capacitive switches with silicon nitride dielectric film. The investigation included MIM capacitors in order to obtain a better insight on the irradiation introduced defects in the dielectric film. The assessment employed the thermally stimulated depolarization currents method for MIM capacitors and the capacitance–voltage characteristic for MEMS switches. Asymmetric charging was monitored in MIM capacitors due different contact electrodes and injected charge interactions.     

Gamma radiation effects on RF MEMS capacitive switches

Dielectric-based RF MEMS capacitive switches were fabricated and characterized for their response to dielectric charging, thermal storage and cycling and to total dose gamma irradiations. The evolution of the switch electromechanical and RF characteristics (actuation and releasing voltages, insertion losses, isolation) were evaluated as a function of the applied stress (temperature or total ionizing dose). It is indicated that the thermal stress has a relatively minor impact on the switches (the switches remained functional with nearly the same electrical properties). Under our particular test conditions, C(V) and S-parameters measurements show that gamma radiation has low to moderate effects on the components behavior.     

Electrostatic discharge failure analysis of capacitive RF MEMS switches

This paper reports on the investigation of failure mechanisms of aluminum nitride (AlN)-based capacitive RF MEMS switches. Electrostatic discharge (ESD) experiments have been carried out by means of a transmission line pulsing (TLP) technique and a first experiment under human body model (HBM) stresses has been done. It has been observed that TLP stresses gives rise to electric arcs and the degradations have been analyzed and are reported in this paper. Microwave measurements have shown that TLP stresses impact the quality of the capacitive contact. HBM robustness in upstate configuration and its different failure modes have been also reported.     

Reliability testing of flexible printed circuit-based RF MEMS capacitive switches

In this paper, reliability results of a novel type of electrostatically actuated RF MEMS capacitive switches developed by our group are discussed. The test setup used for reliability testing consists of the capacitive MEMS switch under test connected in series with a resistor. A specified actuation waveform is applied to the switch and the voltage waveform across the resistor is continuously recorded. The recorded waveform aids in identifying short, open, or stiction failure of the switch. Further, the waveform recorded can be analyzed to study the degradation, reliability, and lifetime characteristics of the switch. The proposed method has been used to study the reliability, failure, and hold-down test characteristics of flexible circuit-based RF MEMS switches. Reliability testing up to 75 million operations has been carried out for flexible circuit-based RF MEMS switches.     

Temperature study of the dielectric polarization effects of capacitive RF MEMS switches

This paper investigates both theoretically and experimentally the dielectric charging effects of capacitive RF microelectromechanical system switches with silicon nitride as dielectric layer. Dielectric charging caused by charge injection under voltage stress was observed. The amphoteric nature of traps and its effect on the switch operation were confirmed under both positive and negative control voltages. It has been confirmed that charging is a complicated process, which can be better described through the stretched exponential relaxation. This mechanism is thermally activated with an activation energy being calculated from the temperature dependence of the capacitance transient response. The charging mechanism, which is responsible for the pull-out voltage and the device failure, is also responsible for the temperature-induced shift of the capacitance minimum bias.     

Measurement and analysis of substrate leakage current of RF mems capacitive switches

This paper focused on a new direction of study on leakage current called substrate charge injection. The substrate leakage current of capacitive RF micro-electro-mechanical-system (MEMS) switches was measured, and the conduction mechanism was estimated. The study of the leakage current conduction mechanisms of the substrate dielectric film shows that leakage is mainly induced by hopping conduction at low electric fields, whereas both Schottky emission and hopping conduction may contribute to the leakage current at high fields. The quantitative relationship between the substrate leakage current and the dielectric layer leakage current was also determined for the first time. In the case of low drive voltage (0–30 V), the substrate leakage current significantly contributes to the total leakage current. Results show that the charging properties of the substrate should not be neglected at low drive voltage because such properties could significantly affect the functionality and reliability of RF MEMS switches.     

Fabrication, assembly, and testing of RF MEMS capacitive switches using flexible printed circuit technology

A novel approach for cost effective fabrication, assembly, and packaging of radio-frequency microelectromechanical systems (RF MEMS) capacitive switches using flexible circuit processing techniques is reported. The key feature of this approach is the use of most commonly used flexible circuit film, Kapton-E polyimide film, as the movable switch membrane. The physical dimensions of these switches are in the mesoscale range. For example, electrode area and gap height of a capacitive shunt switch on coplanar waveguide are 2 /spl times/ 1 mm/sup 2/ and 43 /spl mu/m, respectively. Pull-down voltage is in the range of 90-100 V. In the ON state (up-position), the insertion loss is less than 0.3-0.4 dB up to 30 GHz. In OFF state (down-position), the isolation value is about 15 dB at 12 GHz and increases to 36 dB at 30 GHz. These switches are uniquely suitable for batch integration with printed circuits and antennas on laminate substrates.     

GaAs FET RF switches

The device parameter dependences of GaAs FET switch performance have been determined analytically and by two-dimension simulation. FET switch design would maximize the value of the switch quality factor while retaining the power handling capacity. Expressions for both the quality factor and power handling capacity are derived in terms of device parameters, and would enable such optimization to be performed.     

Inline capacitive and DC-contact MEMS shunt switches

This paper presents inline capacitive MEMS shunt switches suitable for X/K-band and Ka/V-band applications. The inline switch allows for a low- or high-inductance connection to the ground plane without changing the mechanical characteristics of the MEMS bridge. Excellent isolation and loss are achieved with this design, and the performance is very similar to the standard capacitive MEMS shunt switch. Also, a new metal-to-metal contact MEMS shunt switch is presented. A novel pull-down electrode is used which applies the electrostatic force at the same location as the metal-to-metal contact area. A contact resistance of 0.15-0.35 Ω is repeatable, and results in an isolation of -40 dB at 0.1-3 GHz. The measured isolation is still better than -20 dB at 40 GHz. The application areas are in high-isolation/low-loss switches for telecommunication and radar systems     

发展中的RF MEM5开关技术

射频MEMS开关是用MEMS技术形成的新的电路元件,与传统的半导体开关器件相比具有插入损耗低、隔离度大、线性度好等优点,将对现有雷达和通信中RF结构产生重大的影响.介绍了射频MEMS开关的工作原理、优化设计,分析了可靠性问题,举例说明了射频MEMS开关的应用,指出了其发展所面临的问题.     

High-power operation of III-N MOSHFET RF switches

We describe a large-signal performance of novel high-power radio frequency (RF) switches based on III-nitride insulated gate metal-oxide semiconductor heterostructure field-effect transistors (MOSHFETs). The maximum switching powers for a single MOSHFET with only 1-mm gate width exceed 50W at 10GHz, more than an order of magnitude higher than those achievable using GaAs transistors. In the ON state, the highest powers are determined by the device peak drain currents, 1-2A/mm for the state-of-the art III-N MOSHFETs; in the OFF state their maximum powers are limited by the breakdown voltage, normally well above 100V. Our experimental data are in close agreement with large-signal simulations and the proposed simple analytical model. We also show that the insulating gate design allows for broader bandwidth and higher switching powers and better stability as compared to conventional Schottky gate transistors.     

基于砷化镓衬底的RF MEMS膜开关

射频微机械开关由于其优越的高频特性在微波和毫米波电路中表现出巨大的应用前景。但是目前的微机械开关都是制作在硅基衬底上的，难于与后面的高频砷化镓处理电路相集成。本文介绍了基于砷化镓衬底的RFMEMS膜开关，着重介绍了开关的工作原理、制作过程和测试结果。     

基于砷化镓衬底的RF MEMS膜开关

射频微机械开关由于其优越的高频特性在微波和毫米波电路中表现出巨大的应用前景。但是目前的微机械开关都是制作在硅基衬底上的 ,难于与后面的高频砷化镓处理电路相集成。本文介绍了基于砷化镓衬底的RFMEMS膜开关 ,着重介绍了开关的工作原理、制作过程和测试结果     

Kelvin probe microscopy for reliability investigation of RF-MEMS capacitive switches

In this work, we investigate the charging and reliability of interlayer dielectric materials that are used in the fabrication process of advanced RF-MEMS switches. In particular, the charge stored on the surface of a dielectric and the dynamic of this charge at nanometric scale are studied. More attention is given to the decay of the deposited charge by a variety of means: (1) surface conduction, (2) surface charge spreading due to self repulsion and (3) charge injection in the bulk of dielectric material. Kelvin force microscopy (KFM) measurements were performed for various injection time and bias voltage. These results suggest a dynamic charge and allow to predict the amount of charge injected into the dielectric.     

Performance of RF MEMS switches at low temperatures

The actuation voltage of microelectromechanical system (MEMS) metal switches was investigated at temperatures ranging from 10 to 290 K. The investigation shows a 50% increase in the actuation voltage at low temperature. A comparison has been made using a published model and showed similar increment of actuation voltage at low temperature     

Thermal and electrostatic reliability characterization in RF MEMS switches

The reliability of RF MEMS switches is closely linked to their operational and environmental conditions. This paper examines the reliability of five different capacitive switch designs by a combined use of modeling and experimental tools. Three-dimensional multiphysics finite element analysis was performed to estimate the actuation voltage and deflection vs. temperature variations of the micro-switches. The effect of temperature and temperature cycles on switch dilatation and pull-in voltage are studied, as well as the influence of different operational signals on switch reliability.     

Uniformity of silicon microcrystallinity in large area RF capacitive reactors

In this work, a controlled, nonuniform RF power distribution is produced across a large area PECVD reactor. The effect of the RF power distribution on the crystallinity of silicon thin films deposited from silane‐hydrogen discharges is studied. Results show that, even with a strongly nonuniform RF distribution (70%), uniform crystallinity can still be achieved for films deposited at the limit between amorphous and microcrystalline silicon provided that the input silane concentration is sufficiently low (nominal concentration lower than ≈︂1˙2%). This work shows that to deposit silicon with a uniform microcrystallinity over large area using high silane concentration, the reactor design must guarantee a highly uniform power distribution. Copyright © 2008 John Wiley & Sons, Ltd.     

Determination of bulk discharge current in the dielectric film of MEMS capacitive switches

The present work presents a new method to calculate the discharge current in the bulk of dielectric films of MEMS capacitive switches. This method takes into account the real MEMS switch with non uniform trapped charge and air gap distributions. The assessment of switches with silicon nitride dielectric film shows that the discharge current transient seems to obey the stretched exponential law. The decay characteristics depend on the polarization field’s polarity, a fact that comes along with experimental results obtained from the thermally stimulated depolarization currents (TSDC) method used in MIM capacitors.