L. Michalas

A study of field emission process in electrostatically actuated MEMS switches

Abstract A study of field emission process in MEMS-based capacitor/switch-like geometries is presented. High resolution current–voltage characteristics up to breakdown have been obtained across micro-gaps in fixed–fixed Metal–Air–Metal and Metal–Air–Insulator–Metal structures. In metallic devices the I–V dependence reveals Fowler–Nordheim theory effects. In the presence of insulator the process is found to be limited by the film conductivity following Poole–Frenkel dependence. The data analysis reveals the major importance of surface asperities on the onset of the field emission process while it is also presented that charge transfer may occur between metal and insulator surfaces even in the presence of micrometer scale gaps.

The effect of temperature on dielectric charging of capacitive MEMS

The present paper investigates the effect of temperature on the charging process in dielectric films of MEMS capacitive switches. The investigation includes the assessment of MIM capacitors and MEMS capacitive switches. The data analysis shows that the dielectric charging is thermally activated and the process can be described by a system with a wide distribution of relaxation times that exhibits power-law relaxation. The activation energies obtained from MIM and MEMS are attributed to different charge collection mechanisms.

Electrical characterization of undoped diamond films for RF MEMS application

Diamond films are considered as superior dielectric in comparison to Si3N4 for MEMS applications. The present paper provides a detail characterization study of electrical properties of undoped microcrystalline diamond films involving dc and charge/discharge transient analysis over a wide temperature range. The aim of the study is to provide a better insight on the physical mechanisms responsible for the charge injection and collection processes under different operation conditions applicable to MEMS capacitive switches.

Gold nanorod array structured silicon nitride films for reliable RF MEMS capacitive switches

The electrical properties of gold rods nanostructured silicon nitride are investigated. The paper aims to determine the advantages of the nanostructured material over conventional dielectrics that will mitigate the dielectric charging and provide a potential candidate for insulating films in MEMS capacitive switches. Different nanorod diameters and densities were grown. A model was implemented to describe both the DC and low frequency electrical properties. Finally, the device performance up to 40GHz was assessed.

Assessment of dielectric charging in RF MEMS capacitive switches with the aid of MIM capacitors

Dielectric charging is an important reliability issue for RF MEMS capacitive switches still preventing their commercialization. Therefore a lot of effort has been spent on the understanding of charging and discharging processes. MIM capacitors are considered as equally important device for the assessment of dielectric charging for RF MEMS. Beside the obvious similarities between MEMS switches in the down state and MIM capacitors there are also some important differences. The present papers aims to reveal the similarities and the differences between the two types of devices by analyzing experimental data obtained on MIM capacitors and MEMS capacitive switches fabricated with the same material.

Electrical properties of nanostructured SiN films for MEMS capacitive switches

The electrical properties of gold nanorods nanostructured silicon nitride films are comprehensively investigated with the aid of metal–insulator–metal capacitors and RF MEMS capacitive switches. Different nanorod diameters and densities were grown on the bottom electrode and with orientation normal to dielectric film surface. A simple physical model, which does not take the effect of electric field fringing into account, was developed to describe both the DC and low frequency electrical properties. It has been shown that the nanorods distribution and dimensions determine the electrical properties as well as the dielectric charging phenomena of the nanostructured films. Finally, in MEMS switches it has been shown that the nanorods presence does not affect the capacitance variance nor the RF characteristics of the device.

Asymmetric dielectric charging phenomena on SiN films used in RF MEMS capacitive switches

The present paper investigates the effect of stressing bias polarity to the discharge process of PECVD SiN films that takes place through the bulk of the dielectric film, with the aid of Kelvin Probe method, and the results are correlated to the materials properties. A new physical model is used in order to gain a better understanding to the processes that are responsible for the appearance of asymmetric dielectric charging on these films. The proposed model can be also used to predict the time evolution of discharging processes on dielectric films with known characteristics and therefore to be included in device reliability modeling.

Advanced dielectric charging characterization in capacitive MEMS

The present work aims to provide a comprehensive view on the available assessment tools to monitor the dielectric charging in MEMS capacitive actuators. A detailed comparison of the up to now employed methods is presented pointing out the strength and weakness of each one. The goal is to obtain a better understanding of the exploitable information drawn from experimental results in an attempt to extract appropriate information on its contribution towards the increase of knowledge on the dielectric charging. Emphasis is given on the comparison of results regarding the effect of electric field intensity, temperature, time window of observation and ambient.

Physics and Electrical Characterization of Excimer Laser Crystallized Polysilicon TFTs

The electrical properties of polycrystalline silicon thin film transistors are investigated. Transfer and transient characteristics have been recorded versus temperature, in the linear operation regime. Basic parameters such as subthreshold swing, leakage current and drain current overshoot transient are found to stem from the same deep states thermally activated carrier generation mechanism

Dielectric charging in MEMS capacitive switches a persisting reliability issue, available models and assessment methods

The reliability issue of dielectric charging in MEMS capacitive switches is discussed taking into account the present knowledge derived from the numerous papers on this topic. The weakness of the available charge injection model is pointed, the dependence of the material stoichiometry with film thickness resulting in lateral charge redistribution is discussed, the available assessment techniques are presented and the discharge process through the dielectric film is analyzed.