Olivier Vendier

Reliability modeling of capacitive RF MEMS

The kinetic of dielectric charging in capacitive RF microelectromechanical systems (RF MEMS) is investigated using an original method of stress and monitoring. This effect is investigated through a new parameter: the shift rate of the actuation voltages. We demonstrate that this lifetime parameter has to be considered as a function of the applied voltage normalized by the contact quality between the bridge and the dielectric. We also demonstrate that this phenomenon is related to Frenkel-Poole conduction, which takes place into the dielectric. We finally propose a model that describes the dielectric charging kinetic in capacitive RF MEMS. This model is used to extract a figure-of-merit of capacitive switches lifetime.

A DC to 100 GHz high performance ohmic shunt switch

This paper presents a wideband ohmic shunt switch implemented on a coplanar waveguide (CPW). The switch is fabricated using a dielectric membrane with patterned metallic contacts that short the CPW line when it is electrostatically actuated. The switch has been extrapolated from measurements. It exhibits low insertion loss, good matching, high isolation from DC to W band (>20 dB up to 100 GHz) and very good mechanical properties with switching time <1/spl mu/s.

A surface-mountable membrane supported filter

A silicon micro-machined filter with a simple planar integration on an other substrate is proposed in this article. The excitation is made from the top of the shielding substrate of a membrane supported micro-machined filter. Packaging and inter-connection are included in the design. Experimental results are presented on a two pole 30 GHz, 4% fractional bandwidth filter with a quality factor of 602 and insertion loss of 1.8 dB. Such a filter can be easily integrated in any circuit using flip-chip technology.

GaN for space application: almost ready for flight

On the last years, gallium nitride (GaN) technology has made a remarked breakthrough in the world of microwave electronics. Power transistors are now available. How this GaN technology would impact space-borne units is now a priority concern. Although the power capability of GaN technology is the first obvious profit, GaN could also be used for other applications like low noise amplifiers, mixers, and probably more. The high sustainable temperature of GaN transistors is most striking advantage for in-flight use. This is connected to packaging design which is also experiencing a lot of activities and quick progresses. Of course, space application is dependent upon the full demonstration of reliability and this constitutes another field of investigation. Finally, after 8 years of GaN studies, experimental results are presented: they open wide the road a revolution inside space-borne electronics: the rise of GaN.

Colloidal Solutions of Organic Conductive Nanoparticles

Although molecular metals have been known for decades, their insolubility, low vapor pressure, and synthesis routes have prevented them from being integrated into electronic devices. We have prepared stable colloidal solutions of the organic metal TTF-TCNQ that overcome such difficulties. The solutions contain well-dispersed nanoparticles stabilized by long alkyl chain amines. They afford soluble powders by evaporation and homogeneous thin films by drop-casting. Powders and films show room temperature conductivities in the 0.01-0.1 S cm(-1) range.

Sub-hundred nanosecond electrostatic actuated RF MEMS switched capacitors

This paper presents a new mechanical architecture for RF MEMS components that are able to achieve reconfiguration faster than conventional MEMS switches. For most MEMS switches, the electrical switching speed is generally limited to a few microseconds, inherently restricted by the delay required to mechanically move their mobile membrane up and down. By using a proper mechanical design and the structural material fabrication process, this paper will show miniature bridges that are able to exhibit mechanical resonance frequencies over 10 MHz range to be compared to the few tens of kHz for conventional RF MEMS switches. As a result, the switching speed of these miniature components is greatly improved and reaches 50 to 100 ns. Such performance has been achieved using composite micro-beams based on the multilayer material assembly of alumina/aluminum/alumina. To our knowledge, this is the fastest switching speed reported for RF MEMS components so far.

Improved thermal management for GaN power electronics: Silver diamond composite packages

A novel packaging solution for GaN power electronics for efficient heat extraction in high power devices is presented. The benefits of using silver diamond composites as base plate in packages for GaN power bars are demonstrated. Micro-Raman thermography measurements were carried out to probe the device temperature for devices mounted on different base plates, silver diamond composites and standard CuW, at a range of operating power levels. A significant improvement in terms of thermal management, achieving a reduction in GaN power electronics temperature by up to a factor of two, was obtained when using silver diamond composites base plates with respect to the existing packaging technologies such as of CuW. Bare silver diamond and Cu-plated silver diamond base plates were compared. The influence of die attach to the base plates on thermal performance of GaN power electronics is also discussed. Finite element thermal model was built to correlate to the experiments, and good agreement was achieved.

RF MEMS ohmic switches for matrix configurations

Two different topologies of radio frequency micro-electro-mechanical system (RF MEMS) series ohmic switches (cantilever and clamped–clamped beams) in coplanar waveguide (CPW) configuration have been characterized by means of DC, environmental, and RF measurements. In particular, on-wafer checks have been followed by RF test after vibration, thermal shocks, and temperature cycles. The devices have been manufactured on high resistivity silicon substrates, as building blocks to be implemented in different single-pole 4-throw (SP4 T), double-pole double-throw (DPDT) configurations, and then integrated in Low Temperature Co-fired Ceramics (LTCC) technology for the realization of large-order Clos 3D networks.

Reliability of Dielectric Less Electrostatic Actuators in RF-MEMS Ohmic Switches

This paper presents the effects of residual charging in dielectric less actuators of RF-MEMS ohmic switches. Indeed, in order to strongly reduce component sensitivity to charging, a dielectric less electrostatic actuator has been introduced in a conventional DC contact series MEMS relay design, resulting both in strong improvement in reliability and preservation of its intrinsic RF performance. Under various stress applied, the pull-in and pull-out voltages drift over time of these components have been observed and analyzed. Hence, based on component pull-in and pull-out voltage measurements during only few minutes of a given stress, an efficient model able to accurately predict the actuator reliability up to 60 days with good agreement will be presented.

MEMS DC contact micro relays on ceramic substrate for space communication switching network

This paper presented several examples of MEMS ohmic micro relay integration applied to the design of wide band and very low loss basic switching functions. These functions form basic blocks which can be implemented to design more complex networks like switching matrixes. Both CPW and microstrip implementation have been studied and optimized to appraise the most favorable configuration. These devices are fabricated on ceramic alumina substrate, and illustrate the high potential of MEMS technology for reconfigurable space communication systems.