Polishing silica sol for LED sapphire substrates and preparation method thereof

Abstract

The invention provides polishing silica sol for LED sapphire substrates. The silica sol comprises a silicon oxide source ethyl orthosilicate, a surfactant octylphenylpolyethylene glycol, a cosurfactant 4-methyl-2-amyl alcohol, an organic solvent cyclohexane, a pH regulator potassium tert-butoxide, a metal ion chelating agent ethylene diamine tetraacetic acid and the rest of deionized water, wherein size of obtained silicon oxide particle is 10-20 nm; at normal temperature, viscosity of silica sol is less than or equal to 10 mm<2> / s, pH value is 10.5-12.5, and specific weight is 1.1-1.2 g / cm<3>. According to the silica sol, usage period is long, shelf-life is greater than 1.5 years, polishing efficiency is high, and hydroxy utilization rate is high.

Description

technical field [0001] The invention relates to the technical field of LED sapphire substrate polishing, in particular to a polishing silica sol and a preparation method thereof. Background technique [0002] With the rapid development of optoelectronic technology, the demand for LED optoelectronic product materials is increasing. Currently, there are many substrate materials that can be used for GaN chip LEDs, but there are still relatively few substrate materials that can be used for commercialization. Generally, only Two, namely sapphire and SiC, have not yet had a third substrate for commercial production of GaN-based LEDs. SiC is a very important substrate material. Compared with sapphire, SiC is a low-resistance material and can be used to make electrodes. Its lattice constant and thermal expansion coefficient of the material are closer to GaN materials, and it is easy to dissolve, and it has blue light. However, the SiC material also has its disadvantages, mainly bec...

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Problems solved by technology

[0005] However, the silica sol reported in domestic patents has the following problems: (1) The particle size is too large. For example, CN106966399A prepares a silica sol with a large particle size of 105nm-120nm by using a 10nm silica seed crystal. The higher the concentration of silicon oxide on the surface, the larger the size, the more conducive to the improvement of the polishing rate, but it is undeniable that in the case of the same silicon content, the number of hydroxyl groups on the surface of silicon sol with large particle size is much lower than that of small particle size. The number of hydroxyl groups on the surface of silica sol, and the number of hydroxyl groups is very important in the polishing process of silica sol. Secondly, the preparation method of this invention is simply grown silicon oxide. Since the growth process of silicon oxide is complicated and the mechanism is not yet clear, in actual production It is difficult to prepare silica sol with uniform size, which is not conducive to the polishing stability in the CMP process

[0006] CN106700942A discloses a sapphire polishing composition and a preparation method thereof. In the method, 0.1 to 5% of saccharides are added to the silica sol, the saccharides can effectively inhibit the generation of corrosion pits, and can maintain the polishing rate. However, this polished silica sol ignores an extremely important factor, that is, the stability and shelf life of silica sol. Usually, the shelf life of commercially available silica sol is more than half a year. When sugar substances are added to silica sol, it is easy to breed Bacteria and fungi will eventually reduce the pH value of the silica sol, which will seriously affect the polishing efficiency of the silica sol or directly cause the product to be scrapped

[0007] CN106978088A discloses a preparation method of a silica sol polishing solution. The silica sol prepared by the method comprises a silica sol with a particle diameter of 100-120nm and a solid content of 43%-45% and a particle diameter of 20-30nm with a solid content of 43%-45% silica sol, and the applicant claims that the double-sized silica sol has a higher polishing rate, but it is not actually the case, because during the polishing process, the large silica particles interact with the surface of the sapphire substrate There are more opportunities for contact, and the possibility of reaction is greater, so it becomes larger and larger until reaching the equilibrium state of solid-solid reaction between the two, while the possibility of reaction of small particles becomes smaller and smaller with the increase of polishing times, so the particle size Basically unchanged, that is, the large particles are getting bigger and more irregular, and the small particles cannot be fully utilized, which is not conducive to the improvement of polishing efficiency.

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