| Since the first integrated circuit was invented in 1958, the Si-based microelectronic technology has been developing very quickly. Completely in consistent with the prediction of the so-called "Moore's Law", the transistor feature size is scaling down to a very small value. The conventional thermal grown SiO2, as the insulating layer, is not applicable, because of the resistance-capacitance delay, cross-talk noise and power dissipation. Based on the detailed analysis of the properties and deposition methods for the candidates, we focus our research on the sol-gel derived nanoporous SiO2 thin film, which has low dielectric constant, and compatibility with existent ULSI technology. To the best of our knowledge, we systematically and comparatively studied the properties of the film, such as preparation, microstructure, chemical bond state and electricity, and achieved many new breakthroughs. Moreover, we bring forward a new method to adulterate fluorine.1. Through sol-gel method with spin-on technology, we deposited nanoporous SiO2 thin film. For the first time, we solve the question about the film surface crack through the spinning modification. The results of SEM and AFM indicate that the pore size is between 70-80 nm, and there is almost not collapse in the network structure. The FTIR analysis confirm role of the twice modification and n-hexane washing. The dielectric constant is 2.0, the leakage current density is 1.5×10-7 A/cm2, and the break down field is 1.9 MV/cm.2. In order to reduce the pore size and size distribution, we used the template method to prepare SiO2 thin film. SEM pictures show that the pore size is in the range of 10-20 nm, and the framework is stronger than that prepared by conventional sol-gel method. For the first time, we find that the template has the homing function to the surface modification due to the two polar bonds. Comparing with the annealing in air atmosphere, the protection of nitrogen atmosphere can prevent the decomposition of the -CH3 bond, leadingto the better hydrophobicity and stability. The dielectric constant is 1.66, the leakage current density is 6.6x10"8 A/cm2, and we did not find the break down phenomenon even when the electric field increases to the value of 2,5 MV/cm.3. For the first time, we introduced the fluorine into the SiC>2 thin film by sol-gel method, and prepared the ultra-low k nanoporous SiO2:F film with good properties. As one of the methods to prepare thin film, this method possesses many virtues, such as simple equipment, easy to be controlled, convenient adulteration, and so on, which further widened the potentiality of sol-gel method.In our experiment, we deposited the SiO2:F thin film using the hydrofluoric acid (HF) as the catalyst. The concentration of the HF is very important, and the best ratio is that HF/ H2O=1/5. The existent of the Si-F bond in the FTIR spectra can confirm the introduction of the fluorine. There is only one kind leakage current emission mechanism in the SiC^F film, that is Schottky emission. The pore size is about 1-10 nm in the film. The relationship between the porosity and the dielectric constant belongs to the Rayleigh model, which indicates that most of the pore is closed and isolated, and be more useful in the ULSI.
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