Effects Of Doping On The Characteristic Of Silicon Nitride For The Capacitive RF MEMS Switches

Compared with the traditional circuit switches devices, RF MEMS switchesare gradually developing into the key infrastructure components because ofexcellent electrical properties in the next generation of communication systems.But during the commercial processing, the failure caused by dielectric charginghas been hampered the pace of large-scale industrial applications. Although thedielectric charging has been studied by many research institutions, the problem isstill not completely solved. As so in this paper, based on the study of how to designinnovative and robust Capacitive RF MEMS switches, the dielectric charging isinvestigated by doping modification method with donor or acceptor impurity forcreating energy gradients to speed up the relaxation process.First of all, after the analysis of the mechanism and characteristic of dielectriccharging in RF MEMS switches, and the analysis and summary of currentdomestic and foreign research status, the ion implantation doping method isproposed to investigate the dielectric charging. Second in order to realize the fastrelaxation of trapped charge through the composite fast state introduced by doping,the first principles doping calculation was carried out based on density functionaltheory by quantum mechanics CASTEP (Material Studio), such as Boron,Phosphorus, and Arsenic (As). And then the metal-insulator-semiconductor (MIS)samples were fabricated and doped with the optimal As dopant by ionimplantation technology. The space charges are finally introduced into thedielectric by stressing the MIS structure with a dc bias. Furthermore, the chargerelaxation kinetics are monitored by capacitance-voltage (C-V) measurement. The influence of several parameters on the dielectric charging has been studied:different bias voltage, electrode area, pressing time, and doping concentration.The results from the investigation show that the releasing velocity of thetrapped charges in the deep energy level could be greatly accelerated and themount of accumulated charges can be also patently reduced by As doping. Theion implantation doping method proposed in this paper provides effectiveexperimental reference and theoretical basis in order to further reveal and controlthe RF MEMS switches dielectric charging. The research in this paper would helpus to develop a novel and robust RF MEMS switch for upcoming military andcommercial applications in wireless communication.