CN104877633A - Magnesium-element-doped silicon dioxide sol compound abrasive grains, polishing solution and preparation method thereof - Google Patents

Abstract

The invention relates to a magnesium-doped silica sol composite abrasive grain, a polishing liquid composition and a preparation method thereof. The preparation method of the composite abrasive grains is as follows: 1.1wt% magnesium nitrate solution and 2.5wt% silicic acid solution are mixed at a mass ratio of 1:1, and precipitated on the silica seed by coprecipitation method. The composite particles in the sol are uniform spherical, and the doping amount of magnesium hydroxide relative to silicon oxide is 0.1wt%-5wt%. A polishing liquid is prepared by using the composite abrasive grains of the present invention. Magnesium is doped into silicon dioxide particles in the form of magnesium hydroxide, which can chemically react with the surface layer of sapphire during the polishing process, increasing the polishing rate. The composite abrasive particles in the sol are uniformly spherical, and the spherical structure can reduce the scratching of the sapphire substrate during the polishing process and maintain the smoothness of the surface. Therefore, polishing the sapphire substrate by using the polishing liquid provided by the invention can effectively improve the removal rate of the sapphire substrate and reduce the roughness of the sapphire surface.

Description

Magnesium doped silica sol composite abrasive grain, polishing liquid and preparation method thereof

technical field

The invention relates to a polishing abrasive grain, a polishing liquid and a preparation method thereof, in particular to a composite abrasive grain doped with magnesium element silica sol, a polishing liquid and a preparation method thereof.

Background technique

Single crystal sapphire has excellent optical, electrical, mechanical, chemical and physical properties. Good light transmission and mechanical properties make it important in aerospace and national defense. Infrared optical glass windows and fairings made of sapphire single crystal have been widely used in airborne, spaceborne, airborne and submarine, Ground-based optoelectronic equipment. It is worth mentioning that the c(0001) surface of single crystal sapphire has become the main substrate material of light-emitting diodes and is used as the sapphire surface of the substrate because of its small lattice coefficient mismatch rate with semiconductor GaN, high mechanical strength, and low price. Must be smooth enough for defect-free growth of GaN. However, single crystal sapphire poses new challenges to precision polishing because of its high hardness and good chemical stability.

At present, chemical mechanical polishing (CMP) is widely used in precision polishing of device surfaces because of its low cost and fast polishing speed. Polishing liquid is the most important element in chemical mechanical polishing, and factors such as the type and dispersion of abrasive particles in the polishing liquid have a great influence on the polishing effect. At present, in the practical application of sapphire polishing, traditional inorganic abrasive grains such as silicon oxide and aluminum oxide are usually used. The polishing rate of sapphire is low, and the polishing rate and surface roughness cannot well meet the industrial needs. Most of the reported composite abrasive grains are obtained through high-temperature calcination and redissolution to obtain composite oxide abrasive grains. During the calcination and redispersion process, the particles will form irregularly shaped agglomerates, thereby increasing the surface roughness of the polished substrate. Spend. The surface of traditional inorganic abrasive grains is grafted with organic core-shell composite abrasive grains, which can reduce the hardness of inorganic abrasive grains, but because the surface organic matter is an inert system, it cannot chemically react well with the substrate surface, thereby reducing the polishing rate .

Contents of the invention

One of the objectives of the present invention is to provide composite abrasive grains of magnesium-doped silica sol and a preparation method thereof.

The second object of the present invention is to provide a polishing liquid containing composite abrasive grains.

To achieve the above object, the present invention adopts the following technical solutions:

The present invention is a composite abrasive particle doped with magnesium element silica sol, which is characterized in that it has the following composition:

Magnesium compound (magnesium hydroxide) 0.1-5 wt.%;

Silica sol 99.9-95 wt.%.

A method for preparing magnesium element-doped silica sol composite abrasive grains of the present invention is characterized in that it has the following processes and steps:

a. prepare pH value as 2.5 with cation exchange method earlier, the silicic acid that mass fraction is 2.5%;

b. Under the condition of stirring at 100 ℃, add 2.5% silicic acid, 1.1% Mg(NO ₃ ) ₂ solution and 1 wt% sodium hydroxide to 750g 10% In the silicon seed crystal; sodium hydroxide controls the pH value of the whole sol system to remain at 10.5, and controls the dropping rate of the mixture of magnesium nitrate and silicic acid to keep the evaporation rate and the dropping rate in the sol system in balance; the silicic acid solution and the described The mass ratio of magnesium nitrate solution is 1:1.

c. Add dropwise for 120 minutes, 240 minutes, and 360 minutes respectively to obtain a composite particle sol system with a magnesium doping amount of 0.5 wt%, 1.0 wt%, and 1.5 wt%, that is, a magnesium-doped silica sol composite mill grain.

A kind of polishing fluid composition of the present invention is characterized in that having following composition:

Magnesium-doped silica composite abrasive grains 10-10.5%,

Dispersant sodium tripolyphosphate 0.2-3%,

Surfactant sodium dodecylbenzenesulfonate 0.01-1%,

deionized water balance;

The sum of the mass percentages of the above components is 100 wt%.

A kind of preparation method of polishing fluid composition of the present invention is characterized in that having following process and step:

a. Pass the above-mentioned magnesium element-doped silica sol composite abrasive solution through a 350-mesh filter to remove large particles;

b. Adjust the pH value to 10.5 with sodium hydroxide;

c. Add 0.2-3% dispersant sodium tripolyphosphate, 0.01-1% surfactant sodium dodecylbenzene sulfonate, and mix evenly to obtain a polishing liquid composition.

The structure of the composite abrasive grain of the present invention is pure silicon dioxide seed crystal inside, and the grown part of the outer layer is the part where magnesium hydroxide and silicon dioxide are doped together. The outer layer of magnesium hydroxide reacts chemically with the aluminum oxide on the sapphire surface, thereby improving the removal rate of sapphire. At the same time, the hardness of magnesium hydroxide is lower than that of silicon oxide, which can reduce the wear on the sapphire surface and reduce the surface roughness. The abrasive grains designed in this way can achieve the purpose of "high speed, low roughness" polishing at the same time.

The polishing liquid provided by the invention is used to polish the sapphire substrate, which can effectively improve the removal rate of the sapphire surface and reduce the roughness of the sapphire surface.

Detailed ways

Embodiments of the present invention will be further described below with some examples. ,

Example.

The magnesium-doped silicon oxide composite abrasive sol of the present invention is prepared by coprecipitation method. The preparation process is as follows: first prepare silicic acid with a pH value of 2.5 and a mass fraction of 2.5 wt % by cation exchange method. Under stirring conditions at 100°C, 620g of silicic acid with a mass fraction of 2.5%, 620g of a Mg(NO ₃ ) ₂ solution with a mass fraction of 1.1%, and 1% sodium hydroxide were added to 750g of 10% in silica seeds. Sodium hydroxide controls the pH value of the whole sol system to remain at 10.5, and controls the drop rate of the mixture of magnesium nitrate and silicic acid to keep the evaporation rate and drop rate in the sol system in balance. A composite particle sol system with a magnesium doping amount of 0.5 wt% was prepared. The particle size of the composite abrasive particle of magnesium-doped silica is 101 nm, and the final pH value of the sol is 10.5. After filtering with a 350-mesh sieve, add 1.0% dispersant sodium tripolyphosphate and 0.5% surfactant sodium dodecylbenzenesulfonate to obtain a polishing solution.

The composition and mass percent of the magnesium-doped silicon oxide composite abrasive polishing fluid are as follows:

Magnesium-doped silica composite abrasive grains 10.05%

Dispersant sodium tripolyphosphate 1.0%

Surfactant sodium dodecylbenzenesulfonate 0.5%,

Deionized water 88.45%;

Example 2.

The magnesium-doped silicon oxide composite abrasive sol of the present invention is prepared by coprecipitation method. The preparation process is as follows: first prepare silicic acid with a pH value of 2.5 and a mass fraction of 2.5 wt % by cation exchange method. Under stirring conditions at 100°C, 1239g of silicic acid with a mass fraction of 2.5%, 1239g of a Mg(NO ₃ ) ₂ solution with a mass fraction of 1.1%, and sodium hydroxide with a mass fraction of 1% were added to 750g of 10% in silica seeds. Sodium hydroxide controls the pH value of the whole sol system to remain at 10.5, and controls the drop rate of the mixture of magnesium nitrate and silicic acid to keep the evaporation rate and drop rate in the sol system in balance. A composite particle sol system with a magnesium doping amount of 1.0 wt% was prepared. The particle size of the composite abrasive particle of magnesium-doped silica is 105 nanometers, and the final pH value of the sol is 10.5. After filtering with a 350-mesh sieve, add 1.0% dispersant sodium tripolyphosphate and 0.5% surfactant sodium dodecylbenzenesulfonate to obtain a polishing solution.

The composition and mass percent of the magnesium-doped silicon oxide composite abrasive polishing fluid are as follows:

Magnesium-doped silica composite abrasive grains 10.1%

Dispersant sodium tripolyphosphate 1.0%

Surfactant sodium dodecylbenzenesulfonate 0.5%,

Deionized water 88.4%;

Example 3.

The magnesium-doped silicon oxide composite abrasive sol of the present invention is prepared by coprecipitation method. The preparation process is as follows: first prepare silicic acid with a pH value of 2.5 and a mass fraction of 2.5 wt % by cation exchange method. Under the condition of stirring at 100°C, 1860g of silicic acid with a mass fraction of 2.5%, 1860g of a Mg(NO ₃ ) ₂ solution with a mass fraction of 1.1% and sodium hydroxide with a mass fraction of 1% were added to 750g of 10% in silica seeds. Sodium hydroxide controls the pH value of the whole sol system to remain at 10.5, and controls the drop rate of the mixture of magnesium nitrate and silicic acid to keep the evaporation rate and drop rate in the sol system in balance. A composite particle sol system with a magnesium doping amount of 1.5 wt% was prepared. The particle size of the composite abrasive particle of magnesium-doped silica is 129 nanometers, and the final pH value of the sol is 10.5. After filtering with a 350-mesh sieve, add 1.0% dispersant sodium tripolyphosphate and 0.5% surfactant sodium dodecylbenzenesulfonate to obtain a polishing solution.

The composition and mass percent of the magnesium-doped silicon oxide composite abrasive polishing fluid are as follows:

Magnesium-doped silica composite abrasive grains 10.15%

Dispersant sodium tripolyphosphate 1.0%

Surfactant sodium dodecylbenzenesulfonate 0.5%,

Deionized water 88.35%;

Comparative example 1.

Pure silica sol polishing solution not doped with magnesium; that is, no magnesium nitrate solution is added in the preparation process; the particle size is 95 nanometers, and the pH value is adjusted to 10.5. After filtering with a 350-mesh sieve, add 1.0% sodium tripolyphosphate as a dispersant and 0.5% sodium dodecylbenzenesulfonate as a surfactant to obtain a pure silica sol polishing solution without doping magnesium.

The composition and mass percent of silicon dioxide abrasive polishing fluid are as follows:

Silica abrasive grains 10%

Dispersant sodium tripolyphosphate 1.0%

Surfactant sodium dodecylbenzenesulfonate 0.5%,

Deionized water 88.5%;

Polishing test: use each of the above-mentioned polishing solutions to perform a polishing test on the sapphire substrate under certain polishing conditions. The polishing conditions are as follows:

Polishing machine: UNIPOL-1502 single-sided polishing machine

Workpiece: Sapphire c(0001) facet with a diameter of 50.8 mm

Polishing pad: Polyurethane material, produced by RODEL

Polishing pressure: 6 kg

Bottom plate speed: 60 rpm

Polishing time: 120 minutes

After polishing, the substrate is then washed and dried, and then the surface topographical characteristics of the substrate are measured. The average surface roughness (Ra) was tested with an Ambios XI-100 surface topography instrument with a resolution of 0.1 angstroms. The test range is 93.5μm'93.5μm. The weight of the substrate was weighed with an analytical balance, and the weight difference before and after polishing was divided by the polishing time as the polishing rate.

The polishing effects of the polishing solutions of each embodiment are shown in Table 1 respectively. It can be seen that compared with Comparative Example 1 (pure silica sol), after polishing the sapphire substrate, the sols containing magnesium-doped composite abrasive grains (Example 1, 2, 3) all increased the polishing speed and reduced the surface friction of the sapphire. roughness.

Table 1 The polishing effect of each embodiment of the polishing solution on the sapphire substrate

the Example 1 Example 2 Example 3 Comparative example 1 Polishing rate mg/h 3.70 4.95 4.80 3.00 Ra, nm 1.775 1.695 1.104 2.654

Claims (4)

1. A composite abrasive particle of magnesium element-doped silica sol, characterized in that it has the following composition: a. Magnesium compound (magnesium nitrate) 0.1-5 wt.%; b. Silica sol 99.9-95 wt.%. 2. A preparation method of magnesium element-doped silica sol composite abrasive grains, characterized in that it has the following processes and steps: a. prepare pH value as 2.5 with cation exchange method earlier, the silicic acid that mass fraction is 2.5%, b. Under the condition of stirring at 100 ℃, add 2.5% silicic acid, 1.1% Mg(NO ₃ ) ₂ solution and 1% sodium hydroxide to 750g 10% In silica seeds, Sodium hydroxide controls the pH value of the whole sol system to remain at 10.5, and controls the rate of addition of the mixture of magnesium nitrate and silicic acid to keep the evaporation rate and the rate of addition in the sol system in balance, both of the silicic acid solution and the magnesium nitrate solution The mass ratio is 1:1, c. By adding different amounts of magnesium nitrate solution dropwise, a composite particle sol system with a magnesium doping amount of 0.5 wt%, 1.0 wt%, and 1.5 wt% was prepared, that is, a composite abrasive grain doped with magnesium element silica sol. 3. A polishing fluid composition, characterized in that it has the following composition: Magnesium-doped silica composite abrasive grains 10-10.5% Dispersant sodium tripolyphosphate 0.2-3% Surfactant sodium dodecylbenzenesulfonate 0.01-1%, deionized water balance; The sum of the mass percentages of the above components is 100 wt%. 4. A preparation method of a polishing liquid composition, characterized in that it has the following processes and steps: a. The above-mentioned magnesium element-doped silica sol composite abrasive solution is adjusted to a pH value of 10.5 with sodium hydroxide; b. Pass through a 350-mesh filter to remove large particles; c. Add 0.2-3% dispersant sodium tripolyphosphate, 0.01-1% surfactant sodium dodecylbenzene sulfonate, and mix evenly to obtain a polishing liquid composition.