Effect of arsenic doping on charge relaxation process in silicon nitride film for capacitive RF MEMS switch application

• The dielectric charging/discharging in SiN films have been investigated by C-V response in an analogous MIS structure.
• The arsenic doping was performed to modify the distribution of energy states in the SiN film to see the effects of arsenic doping on dielectric charging/discharging behaviors. The C-V curves show that low dielectric charging has been obtained in the SiN films after arsenic doping, and the generation and recombination centers were effectively introduced into SiN film.
• The I-V curves exhibit that the film conductivity was correspondingly increased after arsenic doping, and the arsenic-doped SiN films still has excellent dielectric characteristic.
• This work confirms that the dielectric discharging process can be accelerated for low charge accumulation by doping technology.

In this work, effects of arsenic doping on dielectric charging/discharging of silicon nitride (SiN) films prepared by low-pressure chemical vapor deposition (LPCVD) have been investigated for the application of capacitive RF MEMS switches. The dielectric charging/discharging processes have been evaluated in an analogous metal–insulator–semiconductor (MIS) structure by capacitance-voltage (C-V) characterization. Arsenic doping was applied to modify the distribution of energy states in the band gap of thin film SiN. The dielectric discharging behaviors were studied with different discharge time under a dc bias. The C-V curves show that low dielectric charging has been observed in the SiN films after arsenic doping. The generation and recombination centers were introduced into the band gap of thin films SiN, and the dielectric charging is modified and further controlled by the doping technology. The arsenic-doped thin films SiN exhibit excellent dielectric properties to meet the application requirement of capacitive RF MEMS switches.

Fig. 4. Residual charges versus discharging time for the three different samples. As shown in Fig. 4, the number of residual charges in the doped samples is much lower than that in the virginal samples after charge injection, and the amount of the residual charges finally remained in the low-doped samples were decreased very close to zero after 60 min discharging. By fitting the experimental data with an exponential equation, we found that the time constants for the doped samples are slightly higher than that for the virginal sample, which indicates that the time reaching steady state for the doped sample is little faster than that for virginal sample. The experimental results generally show that a low dielectric charging can be obtained in silicon nitride films by arsenic doping.Figure optionsDownload as PowerPoint slide