E. Papandreou

Charging of Radiation Induced Defects in RF MEMS Dielectric Films

The paper investigates the charging of radiation induced defects in Si3N4 and SiO2 dielectric films, which are used in RF-MEMS switches. The radiation has been performed with 5MeV 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.

The Effect of Silicon Nitride Stoichiometry on Charging Mechanisms in RF-MEMS Capacitive Switches

This paper discusses the mechanisms responsible for charging of plasma enhanced chemical vapor deposition (PECVD) silicon nitride films used in the fabrication of RF microelectromechanical (MEMS) switches. Nitride films deposited at different temperatures are characterized in order to better understand the effect of deposition conditions on material stoichiometry and stress. Both RF MEMS switches and metal-semiconductor-metal capacitors with PECVD silicon nitride as the dielectric layer were fabricated and their charging mechanisms were examined. Measurements indicate that charging arises from the formation of a defect band where charge transport occurs through a Poole-Frenkel-like effect. The calculated activation energy exhibits direct relation to material stoichiometry, and therefore to the nitride bandgap. Finally, it is viewed that lower temperature nitride is less prone to dielectric charging.

Properties of contactless and contacted charging in MEMS capacitive switches

Abstract The dielectric charging in MEMS capacitive switches is a complex effect. The high electric field during pull-down causes intrinsic free charge migration and dipole orientation as well as charge injection. The macroscopic dipole moment of the first two mechanisms is opposite to the one arising from charge injection. This causes partial compensation hence mitigates the overall charging and increases the device lifetime. The charging due to intrinsic free charge migration and dipole orientation can be monitored under contactless electric field application in the pull-up state. The paper investigates the characteristics of contactless charging and compares them with the ones of contacted charging. The characteristics of the discharging process that follows each charging procedure are also presented.

Dielectric Discharging processes in RF-MEMS Capacitive Switches

The discharging processes in silicon nitride dielectric film of RF-MEMS capacitive switches are investigated for the first time. The study includes the dependence of discharging as a function of temperature that allows the detection of thermally activated mechanisms. The discharging time constants were found to depend only on temperature and not on the actuation bias polarity.

A correlation of capacitive RF-MEMS reliability to AlN dielectric film spontaneous polarization

This paper investigates the effect of spontaneous polarization of magnetron-sputtered aluminum nitride on the electrical properties and reliability of Radio Frequency – Micro-Electro-Mechanical Systems capacitive switches. The assessment is performed with the aid of application of thermally stimulated polarization currents in metal-insulator-metal capacitors and temperature dependence of device capacitance. The study reveals the presence of a surface charge, which is smaller than that expected from material spontaneous polarization, but definitely is responsible for the low degradation rate under certain bias polarization life tests.

Effect of dielectric film thickness on dielectric charging of RF MEMS capacitive switches

For the first time, the effects of dielectric film thickness in the dielectric charging process of RF MEMS capacitive switches is presented. Both MEMS switches and MIM capacitors are used to investigate charging phenomena. The contribution of charge injection and dipole orientation has been identified. An empirical law that allows the prediction of stored charge on the film thickness was drawn. Above room temperature, the dependence of thermally stimulated depolarization current on a certain activation energy that is independent of dielectric film thickness allows the inclusion of this behavior in modeling tools.

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.

Dielectric Charging in Low Temperature Silicon Nitride for RF-MEMS Capacitive Switches

The paper presents a systematic investigation of dielectric charging in low temperature silicon nitride for RF-MEMS capacitive switches. The investigation takes includes both the effect of dielectric film thickness as well as the effect of metal contacts. The investigation demonstrates that the charging process is asymmetric. It is shown that the amount of stored charge depends significantly on the dielectric film thickness, which is caused from the contribution of the space charge polarization mechanism. Finally, the results are compared with those of higher temperature silicon nitride.

Dielectric charging effects in floating electrode MEMS capacitive switches

Abstract The paper presents a study oriented to the understanding of the floating electrode role on the charging characteristics of floating electrode RF MEMS capacitive switches. Identical devices with and without floating electrode have been stressed under induced charging mode. Biases of different levels and polarities were applied to the transmission line. Reduced and asymmetric, with respect to the bias polarity, charging effects were obtained on devices with floating electrode compared to the conventional ones. The results contribute towards the conclusion that the use of floating electrode in conjunction with the appropriate actuation polarity may reduce the charging effects and thus improving the device lifetime.

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

Abstract Contact-less charging process has been found to constitute a compensation mechanism to dielectric charging of MEMS capacitive switches. The present paper aims to provide a better knowledge of induced charging mechanisms that appear in HF PECVD silicon nitride films. The characteristics of this process as well as the degree of compensation are investigated for different stressing field intensities of both polarities in MEMS capacitive switches. The experimental results indicate that the degree of compensation in HF PECVD SiN x films seems to increase with the intensity of the applied electric field and it is also affected by the polarity of the stressing bias. A new theoretical model that describes the build-up of induced charging is also proposed. Taking into account that the electric field during contact-less charging is quite low, the model assumes that induced charging arises from charge displacement inside the film through hopping conduction processes.