Preparation method of back polishing solution for patterned sapphire substrate

Abstract

The invention belongs to the technical field of polishing solutions, and particularly relates to a preparation method of a back polishing solution for a patterned sapphire substrate, which comprises the following steps: step 1, preparation of aluminum oxide slurry: preparing 30-50% solid slurry in a sand mill by using 99.95% aluminum oxide as a raw material and using high-purity water as a solvent, and step 2, preparation of the sapphire polishing solution, and thirdly, the materials are weighed and packaged through an automatic metering and packaging device. The prepared polishing solution is high in polishing efficiency, and the productivity is improved; the cycle life of the polishing solution can reach 40 Run times, and no damage is caused to a machine table in the process; the dilution ratio of the polishing solution is increased by two times compared with silicon oxide, and the single-chip processing cost is reduced; equipment cleanliness is high, and compared with a silicon oxide polishing solution, crystallization or pipeline blockage is avoided, and the effect of fading back thinning marks after grinding wheel thinning is obvious; the polishing efficiency is high, the cycle life of the polishing solution is prolonged, waste of polishing materials is avoided, and the cycle process speed is relatively stable.

Description

Technical Field

[0001] The invention relates to the technical field of polishing liquid, and in particular to a method for preparing a patterned sapphire substrate back polishing liquid. Background Art

[0002] PSS (Patterned Sapphire Substrate) is a process in which a dry etching mask is grown on a sapphire substrate, a pattern is carved out of the mask using a standard photolithography process, the sapphire is etched using ICP etching technology, the mask is removed, and GaN material is grown on it, thereby changing the longitudinal epitaxy of the GaN material into lateral epitaxy.

[0003] LED is a solid-state lighting source, and its principle is to convert electrical energy into light energy. LED has the advantages of long life, easy control, high efficiency, etc., and is a typical green energy source. However, in the existing GaN-LED structure, the light emitted from the active layer undergoes total reflection and absorption losses inside the LED, and the light that finally escapes from the LED surface is less than 5%, which improves the light output efficiency of the LED.

[0004] Patterned sapphire substrates can increase the light output power and luminous efficiency of LEDs. Since the refractive index of GaN material is higher than that of the sapphire substrate and the external packaging resin, the photons generated in the active area are totally reflected multiple times at the upper and lower interfaces of the GaN layer, reducing the light extraction efficiency of the device. Patterned sapphire substrates can also increase the GaN / sapphire interface area and form diffuse reflection at the interface, so that the photons that originally formed total reflection have a chance to be emitted outside the device, thereby improving the light extraction efficiency of the LED.

[0005] The current substrate patterning technology generally requires a high cost; the nanosphere coating dry etching technology requires high-precision thin film coating equipment, the equipment investment cost is high, and the raw material price of the nanosphere itself is also expensive. Moreover, the patterns after etching are all concave-convex columnar patterns with relatively smooth edges. The brightness of the LED made by epitaxial packaging is not significantly improved, which cannot meet the social demand for high-brightness LEDs;

[0006] As a substrate material, the crystal surface is required to be ultra-smooth. Studies have shown that the quality of the device depends largely on the surface processing of the substrate. Therefore, polishing research must be carried out. Summary of the invention

[0007] Based on the problems raised in the background technology, the present invention proposes a method for preparing a polishing liquid for the back of a patterned sapphire substrate, in order to solve the problem of rapid fading of thinning marks on the back of the patterned sapphire substrate after thinning by a grinding wheel; to replace the silicon oxide polishing liquid that is prone to form stubborn crystals during the processing; and to increase the cycle life of the polishing liquid, thereby reducing the overall processing cost.

[0008] The present invention provides a method for preparing a patterned sapphire substrate backside polishing liquid, comprising the following steps:

[0009] Step 1: Preparation of alumina slurry: using 99.95% alumina as raw material, using high-purity water as solvent and preparing 30%-50% solid content slurry in a sand mill for grinding, grinding the slurry to 0.4-0.6 μm, and preparing polishing liquid;

[0010] Step 2: Preparation of sapphire polishing liquid: prepare the above spare alumina slurry in a high-speed dispersing mixer with high-purity water as solvent at a solid content of 5%-10%. The mixing speed is required to be 600-800rpm. Use a 500-mesh filter to filter during the circulation process to ensure that there are no large particles in the system. Add a dispersant, add an alkaline substance to adjust the slurry pH to 11±1, and add an organic suspending agent to ensure that the slurry has good suspension performance and does not precipitate or agglomerate;

[0011] Step 3: Weigh and package the materials using an automatic metering and packaging device.

[0012] Preferably, in step 1, the grinding medium is 0.6 mm alumina balls, the grinding spindle speed is 700-900 r / min, and the alumina particle size D50 after grinding is between 0.40-0.60 um, and D90<1 um.

[0013] Preferably, the dispersant in step 2 is sodium hexametaphosphate.

[0014] Preferably, the alkaline substance in step 2 is a mixed alkali metal salt of one or more of Mg(OH)2, NaOH or Ca(OH)2.

[0015] Preferably, the organic suspending agent in step 2 is bentonite or PVA, and the organic suspending agent is an organic compound with a high molecular weight, and the molecular weight is ≧10000.

[0016] The beneficial effects of the present invention are:

[0017] The patterned sapphire substrate back polishing liquid proposed in the present invention has high polishing efficiency and improved production capacity; the polishing liquid cycle life can reach 40Run cycles, and no damage is caused to the machine during the process; the polishing liquid dilution ratio is increased by 2 times compared with silicon oxide, and the single-wafer processing cost is reduced; the equipment cleanliness is high, compared with silicon oxide polishing liquid, it does not crystallize / block the pipeline, and the thinning mark on the back after the grinding wheel is thinned is obviously faded; the polishing efficiency is high, the polishing liquid cycle life is extended, the waste of polishing materials is eliminated, and the cycle process rate is relatively stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A particle size distribution diagram of a sapphire substrate back polishing liquid of a graphical sapphire substrate back polishing liquid proposed by the present invention;

[0019] Figure 2 This is a back image of a patterned sapphire substrate back polishing liquid after polishing with an aluminum oxide polishing liquid of the present invention. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0021] Reference Figure 1-2 A method for preparing a patterned sapphire substrate backside polishing liquid comprises the following steps:

[0022] Step 1: Preparation of alumina slurry: using 99.95% alumina as raw material, using high-purity water as solvent and preparing 30%-50% solid content slurry in a sand mill for grinding, grinding the slurry to 0.4-0.6 μm, and preparing polishing liquid;

[0023] Step 2: Preparation of sapphire polishing liquid: prepare the above spare alumina slurry in a high-speed dispersing mixer with high-purity water as solvent at a solid content of 5%-10%. The mixing speed is required to be 600-800rpm. Use a 500-mesh filter to filter during the circulation process to ensure that there are no large particles in the system. Add a dispersant, add an alkaline substance to adjust the slurry pH to 11±1, and add an organic suspending agent to ensure that the slurry has good suspension performance and does not precipitate or agglomerate;

[0024] Step 3: Weigh and package the materials using an automatic metering and packaging device.

[0025] Preferably, in step 1, the grinding medium is 0.6 mm alumina balls, the grinding spindle speed is 700-900 r / min, and the alumina particle size D50 after grinding is between 0.40-0.60 um, and D90<1 um.

[0026] Preferably, the dispersant in step 2 is sodium hexametaphosphate.

[0027] Preferably, the alkaline substance in step 2 is a mixed alkali metal salt of one or more of Mg(OH)2, NaOH or Ca(OH)2.

[0028] Preferably, the organic suspending agent in step 2 is bentonite or PVA, and the organic suspending agent is an organic compound with a high molecular weight, and the molecular weight is ≧10000.

[0029] Implementation case 1:

[0030] Raw material preparation: Use high-purity alumina (>99.95%) as raw material, use high-purity water as solvent to prepare 45% solid slurry in a sand mill for grinding, grind the slurry to 0.4-0.6μm (grinding medium is 0.6mm alumina ball), the grinding spindle speed is 700-900r / min, after grinding, the alumina particle size D50 is 0.504um, D90: 0.869 for preparation of polishing liquid.

[0031] Preparation of sapphire polishing liquid: The above spare alumina slurry is mixed in a high-speed dispersing mixer with high-purity water as solvent at 10% solid content. The mixing speed is required to be 720rpm. Use a 500-mesh filter to filter during the circulation process to ensure that there are no large particles in the system. Add 1% sodium hexametaphosphate as a dispersant and add alkaline substance NaOH to adjust the slurry pH to 11.5. Add PVA compound (molecular weight ≧10000) to ensure that the slurry has good suspension performance and does not precipitate or agglomerate. Weigh and package the materials through an automatic metering and packaging device.

[0032] Implementation case 2:

[0033] Raw material preparation: Use high-purity alumina (>99.95%) as raw material, use high-purity water as solvent to prepare % solid slurry in a sand mill for grinding, grind the slurry to 0.4-0.6μm (grinding medium is 0.6mm alumina ball), the grinding spindle speed is 700-900r / min, after grinding, the alumina particle size D50 is 0.497um, D90: 0.856 for preparation of polishing liquid.

[0034] Preparation of sapphire polishing liquid: The above spare alumina slurry is mixed in a high-speed dispersing mixer with high-purity water as solvent at 10% solid content. The mixing speed is required to be 720rpm. Use a 500-mesh filter to filter during the circulation process to ensure that there are no large particles in the system. Add 1.2% of sodium hexametaphosphate as a dispersant and add alkaline substance NaOH to adjust the slurry pH to 11.5. Add PVA compound (molecular weight ≧10000) to ensure that the slurry has good suspension performance and does not precipitate or agglomerate. Weigh and package the materials through an automatic metering and packaging device.

[0035] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a patterned sapphire substrate back polishing liquid, characterized in that: The following steps are involved: Step 1: Preparation of alumina slurry: using 99.95% alumina as raw material, using high-purity water as solvent and preparing 30%-50% solid content slurry in a sand mill for grinding, grinding the slurry to 0.4-0.6 μm, and preparing polishing liquid; Step 2: Preparation of sapphire polishing liquid: prepare the above spare alumina slurry in a high-speed dispersing mixer with high-purity water as solvent at a solid content of 5%-10%. The mixing speed is required to be 600-800rpm. Use a 500-mesh filter to filter during the circulation process to ensure that there are no large particles in the system. Add a dispersant, add an alkaline substance to adjust the slurry pH to 11±1, and add an organic suspending agent to ensure that the slurry has good suspension performance and does not precipitate or agglomerate; Step 3: Weigh and package the materials using an automatic metering and packaging device.

2. The method for preparing a patterned sapphire substrate back polishing liquid according to claim 1, characterized in that: In the step 1, the grinding medium is 0.6 mm alumina ball, the grinding spindle speed is 700-900 r / min, and the alumina particle size D50 after grinding is between 0.40-0.60 um, and D90<1 um.

3. The method for preparing a patterned sapphire substrate back polishing liquid according to claim 1, characterized in that: The dispersant in step 2 is sodium hexametaphosphate.

4. The method for preparing a patterned sapphire substrate back polishing liquid according to claim 1, characterized in that: The alkaline substance in step 2 is one or more mixed alkali metal salts of Mg(OH)2, NaOH or Ca(OH)2.

5. The method for preparing a patterned sapphire substrate back polishing liquid according to claim 1, characterized in that: The organic suspending agent in step 2 is bentonite or PVA, and the organic suspending agent is an organic compound with a high molecular weight, and the molecular weight is ≧10000.

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