Application of Silica Sol as Polishing Fluid

In the field of optical communication, sapphire crystals are not only used as short-wavelength active devices, but also as passive devices for polarized light. The excellent blocking effect can reduce the capacitive effect of the transistor, and its operation speed can become faster and the power consumption becomes lower. In optoelectronics, sapphire crystals are the substrate material of choice for GaN lightemitting diodes (LEDs). Before growing a thin film on a sapphire substrate, the scratches, pits, stress areas, etc. generated during slicing must be removed first, and then the surface roughness must

be reduced. The greater the roughness of the surface, the more dangling bonds on the surface, the easier it is to adsorb other impurities, and it has a poorer lattice match with the above film.

Traditional pure mechanical polishing uses polishing powder to continuously grind the surface of the material to be polished, which is prone to deep scratches. CMP (ChemicalMechanical Polishing) is to remove chemical reactants through mechanical action in the environment of chemical action, which improves the removal rate of materials and

obtains good surface morphology at the same time.

At present, the commonly used CMP is silica sol, which is a hard and brittle ceramic

material, and its surface chemical activity is very low. SiO2 hydrosol has a double-electron layer structure, and the outer electrons are negatively charged. The surface of

the colloidal SiO2 particles prepared by the coagulation method is rich in silicon

hydroxyl groups. The study also found that the interior of the silica sol prepared by the coagulation method is also rich in silicon hydroxyl groups. This feature makes the SiO2 colloid prepared by the coagulation method have low viscosity, moderate hardness,

no edges and corners, and no scratches during CMP.