Tesis doctoral de David Molinero Giles
The microelectromechanical systems, known as mems, have been in the past few years an authentic revolution in the microelectronics area, based on the interaction between mobile parts and electrical signals in the micron scale. Furthermore, mems can be fabricated with the same technology as conventional cmos devices, making them interesting in the technology market. There are many types of mems devices, but in this work we have concentrated on microelectromechanical switches. The main applications of mems switches are in the radio frequency range, as filters and phase shifters, or more recently in the optic area, such as mobile display. The microelectromechanical switches have many advantages with respect to conventional cmos devices, such as low power consumption, linearity and low loss, but their commercialization is hindered by reliability problems. The mems lifetime is determined by mechanical and electrical problems, which dielectric charging is the most important, based on the charge trapped inside the dielectric that avoids a short-circuit when the switch is actuated. in order to study the dielectric charging problem, several types of microelectromechanical switches have been designed and fabricated with two different dielectric materials: thermally grown silicon dioxide and deposited silicon nitride by plasma assisted. These dielectrics show different physical properties that help to quantify the switches reliability. The fabrication process is based on surface technology by placing different layers patterned to provide the final device. The mems process is limited by the sacrificial layer that forms the final beam shape, which is considered as a critical point. Thus, a new process based on a commercial photoresist has been developed that makes easy the fabrication itself and reduce costs. the charge effects showed in the microelectromechanical switches are similar to those related to mos gate problems investigated years ago. Thus, by using the same physical theory, we have developed a novel theory based on a dynamic model that uses the transient current to extract the dielectric physical properties and quantify the microelectromechanical switch. Furthermore, this theory is also used to study the reliability concerning different actuation modes. The test procedure consists in applying different voltage and current values and measuring the charging and discharging current. The discharge current provides information about the amount of charge trapped in the dielectric, trap energy level and the dielectric conductivity. These parameters have been used to create a novel figure of merit that provides a reliability parameter based on the dielectric and type of actuation used.
Datos académicos de la tesis doctoral «Study of dielectric charging effects on mems switches«
- Título de la tesis: Study of dielectric charging effects on mems switches
- Autor: David Molinero Giles
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 13/05/2009
Dirección y tribunal
- Director de la tesis
- Luis Castañer Muñoz
- Tribunal
- Presidente del tribunal: james c. m. Hwang
- carles Cané ballart (vocal)
- ingrid De wolf (vocal)
- Luis José Fernández ledesma (vocal)