Charge accumulation and their relaxation in SiO_2 films containing silicon nanocrystals

摘要

For the first time, a metal-insulator-semiconductor(MIS) device that consists of silicon (Si) nanocrystals embeddedin a silicon oxide film is proposed to investigate how the chargeaccumulation and relaxation can be manipulated by thenanocrystals for high reliable capacitive RF MEMS switch. A tri-layer structure, used as the insulator in our MIS device,comprises a thicker (about 100 nm) rapid thermal oxidation(RTO) silicon dioxide (SiO2) layer, a Si+SiO2 middle layer (about100 nm) deposited by RF sputtering technique, and a RF-sputtered silicon dioxide capping layer. The electrical propertiesof the device have been characterized using capacitance versusvoltage (C-V) measurements. The experiment results show asignificant change of charge trapping and detrappingmechanisms in the composite insulator due to the presence of theSi nanocrystals in the middle layer. This result offers a possibilitythat the trapping or detrapping mechanisms in the dielectric canbe manipulated by embedding nanocrystals in terms of materials(Ge, Si or other), density, size of nanocrystals and theirdistribution. It is anticipated that the charge trapping and theirrelaxation time in the dielectric of capacitive MEMS switch canbe reduced.