Dispersion And Stability Properties Of Nanosized Silicon Dioxide Slurry And Its Electrochemical Effect To Silicon Wafer

Silicon dioxide nanoparticles have been widely used in chemical mechanical polishing (CMP) , coating material, rubber, binding agent, biology, iatrology, catalyst and other fields for their excellent properties. However, because the particle size is ultrafine and specific surface area is enormous, how to solve the aggregation and to make nanosized silicon dioxide slurry disperse stably is a very important premise to achieve the desired results in CMP process. The dispersing and modifying technologies of silicon dioxide nanoparticles are summarized on the basis of the fundamental theory of solid surface chemistry, colloid chemistry, interface chemistry, solution chemistry and other subjects. Based on these knowledge, the dispersion and stability properties of nanosized silicon dioxide slurry in water and the electrochemical corrosion behavior of nanosized silicon dioxide slurry to silicon wafer are investigated systematically, then these can provide theoretical criterion and guidance for formulating merit property of nanosized silicon dioxide slurry in CMP process of silicon wafer.The wettability of silicon dioxide nanoparticals in water is measured with Washburn method; the influence of different aqueous solutions and surfactants to the dispersion and stability properties of nanosized silicon dioxide slurry are discussed with ζ potential, absorbency and adsorbance, the interactions between particles are discussed on the basis of DLVO and EDLVO theories, which can be used to explain the dispersion and aggregation of the ultrafine particles; the electrochemical property of silicon wafer in different pH nanosized silicon dioxide slurry is researched with the electrochemical direct polarization and the alternating impedance.It is shown that the wettability is good when pH 2.45 and is bad when pH 9.52; the isoelectric point is about pH 2, and the absolute value of ζ potential is higher and the dispersion and stability properties of nanosized silicon dioxide slurry is better between pH 9 and 11; silicon dioxide nanoparticles are easy to aggregate in water without dispersive agent, different kinds of surfactants can improve the dispersion and stability properties of nanosized silicon dioxide slurry, when added anionic and nonionic into slurry, the stabilization of solution improve visibly. The theoretical calculation and analysis show that the effect of pH on dispersion is due to the repulsioninteraction of electrical double layer; the action of surfactant is to become saturation adsorption, increase the thickness of electrical double layer and produce steric repulsive action. The electrochemical research show that the corrosive current of the silicon wafer is larger, the corrosive velocity is quicker and the impedance is smaller between pH 9 and 11 in nanosized silicon dioxide slurry.