Research Of Microstructure, Electrical And Mechanical Properties Of The Nanoporous SiO₂ Thin Film

For reducing parasitic capacitance and resistance capacitance (RC) delay ,it is certain choice to use low dielectric constant materials, along with the development of the high speed and high density for integrate circuit. So low dielectric constant materials become researchful hotspot in micro-electronic domain.In this paper, through Sol-gel method with spin-on technology, we deposited nanoporous SiO₂ thin film using the HCl as the catalyst. Then we replaced HCl by HF as catalyst to deposite nanoporous SiOF thin film. We systematically studied the properties of the film, such as microstructure, electrical property and mechanical property.The results of the testing indicate that nanoporous SiO₂ thin films have network structure, the pore size is between 70-80nm. We improved the microstructure of the films by modification and anneal. The dielectric constant is 2.0, the leakage current density is 1.5×10^-7A/cm², and the break down field is 1.9MV/cm. For the nanoporous SiOF thin film, because of the strongly electronegative F, the microstructure of the siof thin film is optimized. The results of SEM and AFM indicate that the surface of the thin film is more uniform, the grain is smaller, and the pore size is in the range of 10-20nm. The dielectric constant is about 1.5, the leakage current density is 6.12×10^-9A/cm².The dielectric constant of the nanoporous thin film is reduced with the increase of the numberof the pore, but at the same time, hardness and elastic module of the film will become smallness. We tested the hardness and elastic module of samples, the result indicate that the load-displacement curve of the nanoporous SiO₂ thin film is dentate. We analysed that this refer to the nanoporous structure of the sample. Studying indicate that if the pressing deep is more than the ten percent of the thickness of the thin film, the error of testing may be bigger. The result indicate that the hardness of SiOF thin film is 3.45GPa,and the elastic module is 47.19GPa. This result can meet the request of micro-electronics technics basically.