A grinding liquid, preparation method and application thereof

Abstract

The present invention provides a grinding liquid, a preparation method and application thereof. The grinding liquid of the present invention comprises the following components in weight proportion: 60-90 parts of solvent; 1-5 parts of dispersant; 1-5 parts of wetting agent; 1-5 parts of chelating agent; 0.1-1 parts of abrasive; the solvent is a mixture of mineral oil and / or alkane solvent. The present invention also provides a preparation method of the grinding liquid and its use in the field of gallium nitride, silicon carbide, gallium arsenide or indium phosphide grinding. The grinding liquid of the present invention is safe, environmentally friendly and efficient. Grinding gallium nitride with the grinding liquid can effectively improve the surface quality of gallium nitride after grinding, and has high surface quality with low roughness and few scratches.

Description

Technical Field

[0001] The invention relates to grinding liquid technology, and in particular to a grinding liquid, a preparation method and application thereof. Background Art

[0002] With the further development of technology, the performance of second-generation semiconductors is greatly limited due to their physical properties in environments with higher temperatures, faster frequencies and stronger radiation. In addition, due to the small bandgap width, the emitted light can only reach the red light band at most. Therefore, the third-generation semiconductor materials represented by gallium nitride (GaN) came into being. Compared with the first and second generation semiconductor materials, the third generation semiconductor materials have a wider bandgap width, which covers the entire visible spectrum and can be used to make blue, green, and purple light-emitting diodes and semiconductor lasers; in addition, they have higher breakdown electric fields, thermal conductivity, electron saturation rates, and radiation resistance, making them more suitable for making high-temperature, high-frequency, radiation-resistant, and high-power devices.

[0003] Due to the limitations of the GaN preparation process, the surface quality of GaN materials is poor, and the most widely used GaN materials are grown on heteroepitaxial GaN. Due to the lattice mismatch and difference in thermal expansion coefficients between the two, the grown GaN surface is rougher and has a large number of lattice defects.

[0004] Currently, some GaN polishing liquids and polishing methods are disclosed, such as:

[0005] CN106244022A discloses a grinding liquid for gallium nitride semiconductor wafers and a preparation method thereof. The grinding liquid comprises, by weight, 2 to 3 parts of abrasive, 0.5 to 1.5 parts of sodium phosphomolybdate, 0.5 to 1 part of a thickener, 0.5 to 2 parts of a dispersant, 0.5 to 1.5 parts of a pH regulator, 1 to 2 parts of a chelating agent, 5 to 10 parts of a surfactant, and 10 to 20 parts of deionized water; wherein the average particle size of the abrasive is 0.6 to 0.8 μm, and the abrasive is composed of zirconium oxide, aluminum oxide, and cerium oxide, and the weight ratio of the three is 1:2 to 3:1.5 to 2.

[0006] CN111919286A discloses a polishing composition used for polishing a gallium compound semiconductor substrate. The polishing composition comprises silica abrasive grains, a compound Cpho having a phosphate group or a phosphonic acid group, and water. A method for polishing a gallium compound semiconductor substrate is also disclosed, comprising a first polishing step of polishing with a slurry S1 comprising abrasive grains A1 and water, and a second polishing step of polishing with a slurry S2 comprising abrasive grains A2 and water.

[0007] The above-mentioned GaN polishing liquid and polishing method all have problems of low removal rate, deep scratches and high roughness to varying degrees. Therefore, it is crucial to develop a safe, environmentally friendly, efficient and non-corrosive polishing liquid for GaN substrates to improve GaN processing efficiency, surface quality, eliminate deep scratches and improve GaN device performance. Summary of the invention

[0008] The purpose of the present invention is to propose a polishing liquid to address the problems of low removal rate, deep scratches and high roughness of traditional GaN polishing liquid. The polishing liquid is safe, environmentally friendly and efficient. The gallium nitride polished by the polishing liquid has a high removal rate and a high surface quality with low surface roughness and a small number of scratches.

[0009] It should be noted that, in the present invention, unless otherwise specified, the specific meaning of "including" in relation to composition limitations and descriptions includes both open-ended "including", "comprising" and similar meanings, and closed-ended "consisting of..." and similar meanings.

[0010] To achieve the above object, the technical solution adopted by the present invention is: a grinding liquid, comprising the following components in weight proportions:

[0011]

[0012] The solvent is a mixture of mineral oil and / or alkane solvents.

[0013] Furthermore, the solvent is a mixture of mineral oil and alkane solvents with good lubricity. Lubricity is an inherent property of a substance determined by its chemical composition. Generally speaking, alkanes have the worst lubricity, while aromatic hydrocarbons and cycloalkanes have better lubricity. Mineral oil is mainly a mixture of cycloalkanes and aromatic hydrocarbons.

[0014] Furthermore, the mass ratio of the mineral oil to the alkane solvent is 1-6:1.

[0015] Furthermore, the mass ratio of the mineral oil to the alkane solvent is preferably 2-3:1.

[0016] Furthermore, the mineral oil is one or more of white oil, paraffin oil and poly-alpha-olefin synthetic oil.

[0017] Furthermore, the white oil is one or more of 3# white oil, 5# white oil, 10# white oil and 15# white oil.

[0018] Furthermore, the polyalphaolefin synthetic oil is one or more of PAO2, PAO4, PAO5, PAO8 and PAO10.

[0019] Furthermore, the alkane solvent is C8-C14 alkane.

[0020] Furthermore, the C8-C14 alkane is one or more of octane, nonane, decane, undecane, dodecane, tridecane and tetradecane.

[0021] Furthermore, the solvent is preferably polyalphaolefin synthetic oil and C8-C14 alkane.

[0022] Furthermore, the solvent is most preferably PAO8 and dodecane.

[0023] Furthermore, the mass ratio of PAO8 to dodecane is 1-6:1.

[0024] Furthermore, the mass ratio of PAO8 to dodecane is preferably 2-3:1.

[0025] Furthermore, the mass ratio of PAO8 to dodecane is most preferably 3:1.

[0026] Furthermore, the solvent is 70-80 parts.

[0027] Furthermore, the dispersant is a non-ionic dispersant.

[0028] Furthermore, the dispersant is preferably a solvent-based dispersant.

[0029] Furthermore, the dispersant is more preferably a long-chain solvent-type dispersant.

[0030] Furthermore, the long-chain solvent-based dispersant is one or more of polycaprolactone polyol-polyethyleneimine block copolymer, polyacrylate and polyurethane.

[0031] Furthermore, the molecular weight of the polycaprolactone polyol-polyethyleneimine block copolymer is 10 3 -10 7 .

[0032] Furthermore, the molecular weight of the polycaprolactone polyol-polyethyleneimine block copolymer is preferably 10 4 -10 6 .

[0033] Furthermore, the molecular weight of the polyacrylate is 10 4 -10 6 .

[0034] Furthermore, the molecular weight of the polyacrylate is preferably 10 4 -10 5 .

[0035] Furthermore, the molecular weight of the polyurethane is 10 4 -10 6 .

[0036] Furthermore, the molecular weight of the polyurethane is preferably 10 4 -10 5 .

[0037] Furthermore, the dispersant is more preferably polyacrylate.

[0038] Furthermore, the dispersant is 2-4 parts.

[0039] Furthermore, the wetting agent is a surfactant that can significantly reduce surface tension.

[0040] Furthermore, the wetting agent is a non-ionic surfactant.

[0041] Furthermore, the nonionic surfactant is one or more of polyoxyethylene amide, polyoxyethylene castor oil, sorbitan laurate, monoglyceride and diethanolamide.

[0042] Furthermore, the molecular weight of the polyoxyethylene amide is 1000-5000.

[0043] Furthermore, the molecular weight of the polyoxyethylene castor oil is 5000-10000.

[0044] Furthermore, the wetting agent is preferably diethanolamide.

[0045] Furthermore, the wetting agent is 1-3 parts.

[0046] Furthermore, the chelating agent is a chelating agent soluble in a solvent.

[0047] Furthermore, the chelating agent is a ligand containing two or more coordinating atoms.

[0048] Furthermore, the chelating agent is one or more of citric acid monoglyceride, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracarboxylic acid (DOTA), DOTA-tri-tert-butyl ester-maleimide and DOTA-tri-tert-butyl ester-azide.

[0049] Furthermore, the chelating agent is preferably DOTA.

[0050] Furthermore, the chelating agent is 2-4 parts.

[0051] Furthermore, the abrasive is diamond abrasive.

[0052] Furthermore, the abrasive is one or more of polycrystalline diamond abrasive, polycrystalline diamond-like abrasive, polycrystalline diamond abrasive and single crystal diamond abrasive.

[0053] Furthermore, the abrasive is preferably polycrystalline diamond.

[0054] Furthermore, the abrasive particle size ranges from 3 to 8 μm.

[0055] Furthermore, the abrasive particle size is preferably 5-6 μm.

[0056] Polycrystalline diamond abrasives are tough and self-sharpening. During the grinding process, coarse particles will be broken into smaller particles, presenting more sharp surfaces. Not only is the removal rate high, but the surface grinding is also gentler, avoiding scratches on the grinding substrate surface, which not only ensures the surface quality of the substrate but also improves the grinding efficiency.

[0057] Furthermore, the abrasive is 0.5-0.8 parts.

[0058] Another object of the present invention is to disclose a method for preparing a grinding liquid, comprising the following steps:

[0059] Step 1: Weigh each component according to the weight ratio;

[0060] Step 2: Mix and stir the solvent and the chelating agent;

[0061] Step 3: Add dispersant and wetting agent to the above solution and stir;

[0062] Step 4: Add diamond abrasive to the above solution and stir to prepare a grinding liquid.

[0063] Furthermore, the stirring conditions in step 2 are: stirring at 500-800 rpm, 25-30° C. for 5-10 min.

[0064] Furthermore, the stirring conditions in step 3 are: stirring at 500-800 rpm, 25-30° C. for 5-10 min.

[0065] Furthermore, the stirring conditions in step 4 are: stirring at 500-800 rpm, 25-30° C. for 30-60 min.

[0066] Another object of the present invention is to disclose a use of a grinding liquid in the field of grinding gallium nitride, silicon carbide, gallium arsenide or indium phosphide, especially in the field of gallium nitride grinding.

[0067] Another object of the present invention is to disclose an application of a grinding liquid in the field of gallium nitride grinding.

[0068] Furthermore, the method of grinding gallium nitride using a grinding liquid comprises the following steps:

[0069] Step 1: Weigh the GaN wafer (4 inches) (accurate to 4 decimal places), stick it on a ceramic plate, and place it in a grinder for grinding. Grinding conditions: speed 80r / min; pressure: 30kg; time: 900s; flow rate: 4mL / min;

[0070] Step 2: After grinding, heat and remove the GaN wafer, clean the wax with ethanol, wash it twice with pure water, dry it naturally, and weigh it (accurate to 4 decimal places);

[0071] Step 3: Calculate the removal rate using the formula MRR = Δm / ρtS. Where Δm is the difference between the two weighings (g), and ρ is the GaN density (g / cm 3 ), t is the grinding time (min), and S is the area of ​​the GaN wafer.

[0072] The present invention provides a grinding liquid, a preparation method and an application thereof, which have the following advantages compared with the prior art:

[0073] 1. The polyalphaolefin synthetic oil used in the present invention has good lubricity, can effectively reduce the friction coefficient during the grinding process, thereby reducing the generation of deep scratches, and can maintain good thermal stability and chemical stability in a wide temperature range. During the entire grinding process, the performance will not change due to changes in the external environment; the polyalphaolefin synthetic oil has moderate viscosity, and can ensure the fluidity of the grinding liquid system while having good suspension, but its mutual solubility with the wetting agent is poor. After the polyalphaolefin synthetic oil is mixed with C8-C14 alkane (especially dodecane) in a specific ratio, the mutual solubility with the wetting agent is significantly improved, the grinding liquid is clear and transparent, and the stability of the grinding liquid system is effectively improved.

[0074] 2. The present invention uses a polymer dispersant, which takes advantage of its larger steric hindrance to cause a larger steric hindrance, effectively preventing the agglomeration tendency between abrasives, improving the dispersion stability of the grinding liquid, and facilitating further reducing the surface roughness after grinding.

[0075] 3. The present invention utilizes the characteristic of the wetting agent diethanolamide that it has no cloud point, is not easy to precipitate when the temperature rises, has higher stability, and has an anti-rust effect, which can effectively prevent the grinding copper plate from rusting.

[0076] 4. The chelating agent introduced in the present invention can complex the ions on the surface of the substrate and bring the ions out of the grinding contact area in the form of soluble substances, which can not only reduce the generation of defects, but also improve the removal rate and enhance the chemical action in the grinding process. When the chemical action is balanced with the mechanical action, the generation of deep scratches can be minimized. At the same time, DOTA is a twelve-membered tetraazamacrocyclic organic tetradentate ligand that can form stable chelates with a variety of ions.

[0077] 5. The polishing liquid has excellent polishing performance, reduces the number of deep scratches, reduces roughness, and can effectively improve the yield rate of the process. It has no corrosion to the gallium nitride substrate, is environmentally friendly and pollution-free, has low volatile loss, and does no harm to the environment and human body.

[0078] Therefore, the polishing liquid of the present invention has very good application prospects and large-scale industrial promotion potential in the field of semiconductor chip polishing. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 This is a microscope picture of the center of the gallium nitride substrate after being polished with the polishing liquid prepared in Comparative Example 1, magnified 20 times;

[0080] Figure 2 This is a microscope picture of the center of the gallium nitride substrate after being polished with the polishing liquid prepared in Example 1, magnified 20 times. DETAILED DESCRIPTION

[0081] The present invention is further described below in conjunction with embodiments:

[0082] Examples 1-12

[0083] Examples 1-12 disclose a variety of grinding liquids, the components and weight ratios of which are shown in Table 1. The preparation method is as follows: weigh each component according to the weight ratio; first mix and stir the solvent and the chelating agent; then add the dispersant and the wetting agent and stir; finally add the diamond abrasive and stir to prepare the grinding liquid.

[0084] Table 1 Examples 1-12

[0085]

[0086]

[0087] Comparative Examples 1-5

[0088] Comparative Examples 1-5 disclose a variety of polishing liquids, the components and weight ratios of which are shown in Table 2, and the preparation methods thereof are the same as those of Example 1.

[0089] Table 2 Components and weight ratios of the grinding fluids of Comparative Examples 1-5

[0090]

[0091] Performance test and description

[0092] The various properties of the above embodiments or comparative examples are tested as follows:

[0093] Figure 1This is a microscope picture of the center of the gallium nitride substrate after being polished with the polishing liquid prepared in Comparative Example 1, magnified 20 times. Figure 1 It can be seen that a large number of deep scratches appeared after grinding the gallium nitride substrate using the grinding liquid prepared in Comparative Example 1; Figure 2 This is a microscope picture of the center of the gallium nitride substrate after being polished with the polishing liquid prepared in Example 1, magnified 20 times. Figure 2 It can be seen that after the gallium nitride substrate is polished using the polishing liquid prepared in Example 1, no deep scratches are left.

[0094] The depth and number of scratches on the GaN surface after grinding or back thinning have a very important impact on the subsequent processing steps. If the scratch depth after grinding is too deep, there is a high probability that it will directly lead to scrap. Therefore, the depth and number of scratches are important indicators of the surface quality after grinding. The main detection method is to compare the grayscale of the scratches under a microscope, that is, the darker the color, the deeper the scratch depth.

[0095] Table 3 shows the test results of Examples 1-12 and Comparative Examples 1-5. Suspensibility represents the time when delamination is first observed after the system stops stirring; removal rate refers to the thickness of the gallium nitride sheet reduced per minute in the gallium nitride grinding method of the present invention; surface roughness refers to the smaller spacing and tiny peak-to-valley unevenness of the processed surface; the number of deep scratches refers to the comparison of scratch grayscale under the same magnification (the present invention is tested under 20 times magnification) using a microscope. If the grayscale is significantly higher than other scratches, it is defined as a deep scratch and the number of deep scratches is observed.

[0096] Table 3 Test results of Examples 1-12 and Comparative Examples 1-5

[0097]

[0098] in:

[0099] Performance 1 Suspension test method is:

[0100] The grinding liquid was stored at room temperature away from light, and the stratification after different storage times was examined to investigate its stability.

[0101] The test method for performance 2 removal rate is:

[0102] The removal rate test method includes the following steps:

[0103] Step 1: After weighing the GaN wafer (accurate to 4 decimal places), use solid or liquid wax to stick it on a ceramic plate. After cooling to room temperature, place it in a grinder for grinding. Test conditions: speed 80r / min; pressure: 30kg; time: 900s; flow rate: 4mL / min;

[0104] Step 2: After grinding, heat and remove the GaN wafer, clean the wax with ethanol, wash it twice with pure water, dry it completely naturally, and weigh it (accurate to 4 decimal places);

[0105] Step 3: Calculate the removal rate using the formula MRR = Δm / ρtS.

[0106] Δm is the difference between the two weighings (g), ρ is the density of GaN (g / cm 3 ), t is the grinding time (min), S is the area of ​​the GaN wafer (cm 2 ).

[0107] The test method for performance 3 surface roughness is:

[0108] A total of 5 points were selected around the gallium nitride wafer and its center, and a surface roughness tester was used to test the roughness of the 5 points separately. Each point was measured 3 times, and the average roughness value was taken.

[0109] The test method for the number of deep scratches of Performance 4 is:

[0110] The number of deep scratches was observed using a microscope at the same magnification (the present invention was tested at a magnification of 20 times), and the surrounding areas and the center of the gallium nitride wafer were selected for observation, and the average was finally taken.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gallium nitride polishing liquid, It is characterized in that The composition includes the following components in weight ratio: 60-90 parts of solvent; Dispersant 1-5 parts; Wetting agent 1-5 parts; 1-5 parts of chelating agent; Abrasive 0.1-1 part; The solvent is polyalphaolefin synthetic oil and C8-C14 alkane; the mass ratio of the polyalphaolefin synthetic oil to the C8-C14 alkane is 2-3:1; The chelating agent is one or more of citric acid monoglyceride, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracarboxylic acid, DOTA-tri-tert-butyl ester-maleimide and DOTA-tri-tert-butyl ester-azide; The dispersant is a non-ionic dispersant; The wetting agent is a nonionic surfactant; The abrasive is diamond abrasive.

2. A method for preparing the gallium nitride polishing liquid according to claim 1, It is characterized in that The following steps are involved: Step 1: Weigh each component according to the weight ratio; Step 2: Mix and stir the solvent and the chelating agent; Step 3: Add dispersant and wetting agent to the above solution and stir; Step 4: Add diamond abrasive to the above solution and stir to prepare a grinding liquid.

3. Use of the gallium nitride polishing liquid according to claim 1 in the field of gallium nitride polishing.

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