A single-component capsule for chemical mechanical polishing and its preparation method and application

Abstract

This invention discloses a single-component capsule for chemical mechanical polishing (CMP), its preparation method, and its application. The preparation method employs in-situ polymerization, using one of the raw materials that generates a strong oxidizing substance as the core material. This core material is encapsulated within a chemically stable, well-sealed, and inexpensive melamine-formaldehyde resin shell to form a single-component capsule. This effectively isolates the raw materials that generate the strong oxidizing substance before CMP, preventing premature formation of the strong oxidizing substance and thus reducing its utilization rate. This invention also proposes an application of the above-mentioned single-component capsule in CMP, which facilitates the controllable and efficient removal of strong oxidizing substances from hard and brittle material surfaces at low cost, while ensuring a stable and continuous supply and efficient utilization of the oxidizing substance. Furthermore, it effectively guarantees the processing effect of hard and brittle material surfaces, resulting in a smooth surface with low damage.

Description

Technical Field

[0001] This invention relates to the field of chemical mechanical polishing (CMP) technology, and more particularly to a single-component capsule for CMP, its preparation method, and its application. Background Technology

[0002] With the rapid development of materials science, hard and brittle materials have evolved into third-generation semiconductor materials. Among these, third-generation semiconductor single crystals (such as SiC and GaN) are widely used in extreme environments such as high temperature, high pressure, high frequency, and high power due to their advantages including wide bandgap, high critical breakdown electric field, high thermal conductivity, and high hardness. They have a very broad application prospect in fields such as electronic devices, new energy vehicles, LED semiconductor lighting, and satellite communications. However, the extremely high hardness and brittleness of third-generation semiconductor materials also bring enormous challenges to ultra-precision machining technology. In the ultra-precision machining of hard and brittle materials, chemical mechanical polishing (CMP) is considered one of the most effective and commonly used methods to achieve global planarization and ultra-smooth, damage-free surfaces.

[0003] In conventional chemical mechanical polishing (CMP), the high hardness and brittleness of semiconductor materials make it difficult for abrasives to remove the damage layer left over from the previous process on the workpiece surface. Therefore, when performing ultra-precision machining of semiconductor materials, two chemical reaction components are typically used to generate a strong oxidizing agent. This strong oxidizing agent, generated through a chemical reaction, forms a softer oxide layer with weaker adhesion on the workpiece surface, facilitating subsequent mechanical removal without damaging the workpiece itself. The two chemical components used to generate this strong oxidizing agent are generally an oxidant and a catalyst, with the oxidant typically being hydrogen peroxide (H₂O₂) or persulfate (S₂O₈). 2- The aforementioned oxidants can decompose under specific conditions to produce strong oxidizing substances, namely hydroxyl radicals (·OH) or sulfate radicals (SO4). - Iron ions (Fe2+) possess extremely strong oxidizing power; while catalysts are typically iron ions (Fe3+). 2+ or Fe 3+ These substances can catalyze and accelerate the formation of strong oxidizing agents. Specifically, the Fenton reaction is a typical example, with the chemical equation: Fe... 2+ +H₂O₂→Fe 3+ +·OH+OH - The hydroxyl radicals generated can react with the surface of semiconductor materials to form a softer oxide layer, which can be easily removed by the mechanical action of the abrasive without damaging the workpiece itself.

[0004] In addition, due to the strong oxidizing substances generated by the existing reaction, hydroxyl radicals (·OH) and sulfate radicals (SO4) are produced. -Both chemical mechanical polishing (CMP) and mechanical polishing (CMP) suffer from short lifespans, resulting in most of the strong oxidizing agents generated during the reaction becoming inactive by the time they reach the semiconductor wafer processing interface. Only a small portion is utilized, leading to low utilization rates of these agents. Therefore, to achieve a stable and continuous supply and efficient utilization of strong oxidizing agents, current CMP processes typically employ two feeding methods: First, for components with relatively slow chemical reactions, the two components are mixed before polishing, and then the mixed polishing slurry is delivered to the polishing pad surface. However, due to the slow generation rate of strong oxidizing agents in this method, it is difficult to achieve efficient removal from hard and brittle material surfaces. Second, for components with relatively rapid chemical reactions, two separate feeding systems are used to simultaneously add the two components to the polishing pad surface. Through short-time mixing, a rapid reaction generates strong oxidizing agents that act on the hard and brittle material surface. However, this method still suffers from drawbacks such as insufficient mixing of reacting components and difficulty in controlling the reaction time, leading to a mismatch between the chemical reaction rate and the mechanical removal rate, resulting in unsatisfactory processing results.

[0005] In summary, using existing methods of supplying strong oxidizing substances for chemical mechanical polishing of hard and brittle materials makes it difficult to achieve a combination of advantages such as high efficiency, no hard scratches, and low cost in chemical mechanical polishing. Summary of the Invention

[0006] The purpose of this invention is to provide a single-component capsule for chemical mechanical polishing and its preparation method. The method uses in-situ polymerization to use one of the raw materials that generate strong oxidizing substances as the core material, which is then encapsulated in a chemically stable, well-sealed, and inexpensive melamine-formaldehyde resin shell to form a single-component capsule. This method can effectively isolate the raw materials that generate strong oxidizing substances before chemical mechanical polishing, avoiding the premature generation of strong oxidizing substances that would reduce their utilization rate.

[0007] Another objective of this invention is to propose the application of the above-mentioned single-component capsule in chemical mechanical polishing, which is beneficial to achieve controllable and efficient removal of hard and brittle material surfaces at low cost under the premise of stable and continuous supply and efficient utilization of strong oxidizing substances, and can also effectively ensure the processing effect of hard and brittle material surfaces, and obtain a smooth surface with low damage.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] A method for preparing a single-component capsule for chemical mechanical polishing includes the following steps:

[0010] A. Melamine and formaldehyde solutions are added to deionized water, and then a weakly alkaline organic compound is added until the solution is alkaline. After heating and stirring, a melamine-formaldehyde resin prepolymer solution is obtained.

[0011] B. Add the core material to the cooled melamine-formaldehyde resin prepolymer solution, stir, and then add an acid-base adjuster to adjust the pH of the solution to be acidic, thus obtaining an acidic prepolymer.

[0012] C. Add the emulsifier to the sunflower seed oil, stir, then add the acidic prepolymer, and emulsify to obtain a single-component capsule emulsion;

[0013] D. The single-component capsule emulsion is heated and stirred, and then polymerized in situ to obtain a mixture of single-component capsules and sunflower seed oil.

[0014] E. The mixture of single-component capsules and sunflower seed oil is centrifuged, washed, filtered and vacuum dried in sequence to obtain single-component capsules. The core material of the single-component capsules is any raw material that generates strong oxidizing substances, and the wall material of the single-component capsules is melamine-formaldehyde resin.

[0015] in,

[0016] According to the volume ratio, the mixing ratio of melamine-formaldehyde resin prepolymer solution in step B and sunflower seed oil in step C is (1-3):25;

[0017] In step D, the stirring rate of the in-situ polymerization is 300-600 rpm.

[0018] Preferably, step D specifically includes:

[0019] The single-component capsule emulsion was placed in an Erlenmeyer flask and stirred at a stirring rate of 300–600 rpm for 1.5–2.5 h at room temperature to obtain a melamine-formaldehyde resin polymer generated by polycondensation reaction.

[0020] Melamine-formaldehyde resin polymer was placed in a water bath and stirred at 300-600 rpm for 0.5-1.5 h at 50-60°C, and then stirred at 300-600 rpm for 4-6 h at 70-80°C to obtain a mixture of single-component capsules and sunflower seed oil produced by in-situ polymerization.

[0021] Preferably, in step A, the molar ratio of melamine to formaldehyde solution is 1:(1.5-4), the pH of the solution is 8-9, the heating temperature is 60-80°C, the stirring speed is 150-500 rpm, and the stirring time is 10-20 min.

[0022] In step B, the temperature of the cooled melamine-formaldehyde resin prepolymer solution is 20–30°C.

[0023] Preferably, in step A, the weakly basic organic compound is any one of triethanolamine, ethanolamine, diethanolamine, isopropanolamine, and diisopropanolamine, and the concentration of the formaldehyde solution is 30-40 wt%.

[0024] Preferably, in step B, the pH of the solution is 3-4, and the acid-base regulator is citric acid and sodium hydroxide.

[0025] Preferably, in step C, the amount of emulsifier added is 1-3 wt% of the total amount of the emulsifier and the sunflower seed oil, the emulsification speed is 1000-1500 rpm, the emulsification temperature is 50-70℃, and the emulsification reaction time is 20-40 min.

[0026] Preferably, in step C, the emulsifier is a lipophilic emulsifier, and the lipophilic emulsifier is any one of sorbitan monooleate, propylene glycol monolaurate, sorbitan monostearate, and diethylene glycol fatty acid ester.

[0027] Preferably, step E specifically includes:

[0028] The mixture of single-component capsules and sunflower seed oil was centrifuged at a speed of 1500-2500 rpm for 5-10 min.

[0029] After washing the bottom precipitate obtained after centrifugation at least three times with solvent and deionized water, the precipitate was filtered using an oil-free diaphragm vacuum filter at -0.05 to -0.1 MPa to obtain the washed material.

[0030] The washed material was placed in a vacuum drying oven for drying to obtain single-component capsules. The drying temperature was 50-70°C and the drying time was 12-24 hours.

[0031] The solvent is either ethanol or ethyl acetate.

[0032] A single-component capsule for chemical mechanical polishing is prepared using the above-described method for preparing a single-component capsule for chemical mechanical polishing, wherein the core material of the single-component capsule is any raw material that generates a strong oxidizing substance, and the wall material of the single-component capsule is melamine-formaldehyde resin.

[0033] An application of a single-component capsule for chemical mechanical polishing, comprising the following steps:

[0034] (1) Add the single-component capsules to the polishing slurry to prepare a single-component capsule dispersion;

[0035] (2) During the chemical mechanical polishing process, the single-component capsule dispersion is continuously supplied to the polishing pad in the polishing liquid;

[0036] The polishing slurry includes a polishing base liquid and another raw material that generates a strong oxidizing substance. The core material of the single-component capsule reacts with the other raw material in the polishing slurry that generates a strong oxidizing substance to generate a strong oxidizing substance.

[0037] The polishing fluid includes a polishing base fluid and abrasive.

[0038] The technical solution provided by this invention may include the following beneficial effects:

[0039] 1. This technical solution can obtain single-component capsules with smooth surfaces, clear boundaries, uniform particle size, and good dispersibility. The single-component capsules of this technical solution release a strong oxidizing substance generated by the reaction between the core material inside the capsule and another chemical component in the polishing liquid. This can effectively reduce the surface hardness of the hard and brittle material workpiece to be processed. Combined with the removal characteristics of the abrasive in the polishing liquid, it can effectively improve the material removal effect on the workpiece surface. It can achieve chemical mechanical polishing with multiple effects such as chemical enhancement, high efficiency, and no hard scratches on the surface of hard and brittle material workpieces. It can quickly obtain a low-damage ultra-smooth surface in a shorter time and reduce processing costs.

[0040] 2. The single-component capsule preparation method provided by this technical solution uses in-situ polymerization to encapsulate the core material in a chemically stable, well-sealed, and inexpensive melamine-formaldehyde resin wall material to form a single-component capsule. This effectively isolates two chemically reactive components that generate strong oxidizing substances, preventing the reactive components from reacting prematurely. By utilizing the characteristics of the capsule's sealed container, a stable and continuous supply and efficient utilization of strong oxidizing substances can be achieved.

[0041] 3. This technical solution uses melamine-formaldehyde resin as the wall material of a single-component capsule. It can rupture under the polishing pressure of chemical mechanical polishing. After rupture, the released core material reacts with the reactive components during polishing, causing the generated strong oxidizing substances to react with the hard and brittle workpiece at the processing interface instantly, thereby improving the utilization rate of the strong oxidizing substances. Furthermore, by controlling the capsule concentration, delivery rate, and polishing time, the release rate of the core material components within the capsule can be effectively controlled, thus controlling the generation rate of strong oxidizing substances and achieving controllable and efficient removal from the surface of hard and brittle materials. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the preparation process in Embodiment 1 of the present invention.

[0043] Figure 2 This is a schematic diagram illustrating the formation principle of the single-component capsules prepared in Example 1 of the present invention.

[0044] Figure 3 This is a SEM image of the single-component capsules prepared in Example 1 of the present invention.

[0045] Figure 4 This is a particle size distribution diagram of the single-component capsules prepared in Example 1 of the present invention.

[0046] Figure 5 This is an FT-IR image of the melamine-formaldehyde resin, single-component capsule, and ferrous sulfate heptahydrate core material in Example 1 of this invention.

[0047] Figure 6 This is a schematic diagram of the chemical mechanical polishing process in Embodiment 1 of the present invention.

[0048] Figure 7 This is a SEM image of the single-component capsules prepared in Comparative Example 1 of this invention.

[0049] Figure 8 This is a particle size distribution diagram of the single-component capsules prepared in Comparative Example 1 of this invention.

[0050] Figure 9 This is a particle size distribution diagram of the single-component capsules prepared in Comparative Example 2 of this invention.

[0051] Figure 10 This is a particle size distribution diagram of the single-component capsules prepared in Comparative Example 3 of this invention. Detailed Implementation

[0052] A method for preparing a single-component capsule for chemical mechanical polishing includes the following steps:

[0053] A. Melamine and formaldehyde solutions are added to deionized water, and then a weakly alkaline organic compound is added until the solution is alkaline. After heating and stirring, a melamine-formaldehyde resin prepolymer solution is obtained.

[0054] B. Add the core material to the cooled melamine-formaldehyde resin prepolymer solution, stir, and then add an acid-base adjuster to adjust the pH of the solution to be acidic, thus obtaining an acidic prepolymer.

[0055] C. Add the emulsifier to the sunflower seed oil, stir, then add the acidic prepolymer, and emulsify to obtain a single-component capsule emulsion;

[0056] D. The single-component capsule emulsion is heated and stirred, and then polymerized in situ to obtain a mixture of single-component capsules and sunflower seed oil.

[0057] E. The mixture of single-component capsules and sunflower seed oil is centrifuged, washed, filtered and vacuum dried in sequence to obtain single-component capsules. The core material of the single-component capsules is any raw material that generates strong oxidizing substances, and the wall material of the single-component capsules is melamine-formaldehyde resin.

[0058] in,

[0059] According to the volume ratio, the mixing ratio of melamine-formaldehyde resin prepolymer solution in step B and sunflower seed oil in step C is (1-3):25;

[0060] In step D, the stirring rate of the in-situ polymerization is 300-600 rpm.

[0061] To effectively isolate raw materials that generate strong oxidizing substances before chemical mechanical polishing (CMP) and prevent premature formation of these substances that would reduce their utilization rate, this technical solution proposes a method for preparing single-component capsules. This method employs in-situ polymerization to separate one of the raw materials that generate strong oxidizing substances (such as oxidants like hydrogen peroxide or persulfate, or Fe...). 2+ Fe 3+ Using any one of the catalysts as the core material, a single-component capsule is formed by encapsulating it in a chemically stable, well-sealed, and inexpensive melamine-formaldehyde resin shell. By utilizing the characteristics of the capsule's sealing container, the core material, which is one of the raw materials that generates strong oxidizing substances, is effectively isolated from the capsule, thus preventing the premature generation of the two strong oxidizing substances.

[0062] When performing chemical mechanical polishing (CMP), the single-component capsules can be first mixed with a polishing slurry containing another raw material that generates strong oxidizing substances to obtain a dispersion. This dispersion is then supplied to the polishing pad in the polishing slurry containing abrasive particles, achieving a stable and continuous supply and efficient utilization of the strong oxidizing substance. Under polishing pressure, the melamine-formaldehyde resin wall material of the single-component capsules ruptures, releasing the core material inside. This core material reacts with the other raw material in the polishing slurry to generate the strong oxidizing substance, allowing it to react with the hard and brittle workpiece at the processing interface immediately upon generation, thus improving the utilization rate of the strong oxidizing substance. Combined with the removal characteristics of the abrasive particles in the polishing slurry, this effectively improves the material removal effect on the workpiece surface, achieving multiple effects of chemical enhancement, high efficiency, and no hard scratches in the chemical mechanical polishing process for hard and brittle workpieces. This results in a rapid, low-damage, ultra-smooth surface in a shorter time, reducing processing costs. It should be noted that when using the single-component capsules of this solution for chemical mechanical polishing, the release rate of the core material components inside the capsule can be effectively controlled by controlling the concentration, delivery rate and polishing time of the single-component capsules, thereby controlling the generation rate of strong oxidizing substances and achieving controllable and efficient removal from the surface of hard and brittle materials.

[0063] Furthermore, since the particle size of the capsule reflects the amount of core material inside the capsule, and the content of the core material directly affects the formation of strong oxidizing substances on the workpiece surface, and these strong oxidizing substances determine the stress state of the workpiece surface material, ultimately affecting the processing quality of the workpiece surface. Therefore, in order to ensure that the workpiece obtains a low-damage, smooth surface, this scheme also strictly limits the following two process parameters in the preparation method of the single-component capsule.

[0064] First, the mixing volume ratio of the melamine-formaldehyde resin prepolymer solution in step B and the sunflower seed oil in step C is optimized. This volume ratio represents the ratio of the volume of the aqueous phase to the volume of the oil phase in the emulsion system of step C, which is also the ratio of the dispersed phase to the continuous phase. If the volume ratio of the aqueous phase to the oil phase is not set properly, some capsules will stick together during the preparation process, causing agglomeration of single-component capsules, which in turn leads to uneven particle size of the capsules.

[0065] Second, during the in-situ polymerization process in step D, due to the stirring action, three forces—shear stress, surface tension, and viscous stress—simultaneously exist between the droplets in the emulsion system. Only when the shear stress is greater than the combined force of the surface tension and viscous stress will the droplets be fully dispersed and form capsules. The magnitude of the shear stress is closely related to the stirring rate. If the stirring rate is too low, it will cause the capsules to stick together and agglomerate; if the stirring rate is too high, it will easily cause the capsules to rupture. Therefore, the stirring rate is an important means of controlling the dispersibility of capsules. Only by reasonably controlling the stirring rate at each stirring stage can single-component capsules with uniform particle size and good dispersibility be obtained.

[0066] It should be further explained that existing technologies commonly use materials such as glass, silica, and metal as capsule wall materials. However, compared to the melamine-formaldehyde resin in this solution, capsules using these wall materials all suffer from complex preparation methods and higher manufacturing costs. Furthermore, if single-component capsules using glass, silica, or metal as wall materials are used for chemical mechanical polishing, on the one hand, greater polishing pressure is required to break the wall material and release the core material; excessive polishing pressure may cause additional damage to the polished surface of the workpiece. On the other hand, broken wall material may also lead to uneven stress on the workpiece surface, thus affecting the polishing effect.

[0067] To elaborate further, step D specifically includes:

[0068] The single-component capsule emulsion was placed in an Erlenmeyer flask and stirred at a stirring rate of 300–600 rpm for 1.5–2.5 h at room temperature to obtain a melamine-formaldehyde resin polymer generated by polycondensation reaction.

[0069] Melamine-formaldehyde resin polymer was placed in a water bath and stirred at 300-600 rpm for 0.5-1.5 h at 50-60°C, and then stirred at 300-600 rpm for 4-6 h at 70-80°C to obtain a mixture of single-component capsules and sunflower seed oil produced by in-situ polymerization.

[0070] In one specific embodiment, this scheme provides the steps of the in-situ polymerization reaction. By further controlling the reaction temperature and time of each stage in the in-situ polymerization reaction, it is more conducive to ensuring the preparation rate and the uniformity and dispersion of the prepared product.

[0071] To further explain, in step A, the molar ratio of melamine to formaldehyde solution is 1:(1.5-4), the pH of the solution is 8-9, the heating temperature is 60-80℃, the stirring speed is 150-500 rpm, and the stirring time is 10-20 min.

[0072] In step B, the temperature of the cooled melamine-formaldehyde resin prepolymer solution is 20–30°C.

[0073] In one embodiment of this technical solution, controlling the molar ratio of melamine to formaldehyde solution can effectively ensure the water resistance of melamine-formaldehyde resin and improve the storage time of the capsule core material. Cooling the melamine-formaldehyde resin prepolymer solution to 20–30°C before use can effectively ensure the stability of the prepolymer solution, thereby better controlling the in-situ polymerization process.

[0074] To further clarify, in step A, the weakly basic organic compound is any one of triethanolamine, ethanolamine, diethanolamine, isopropanolamine, and diisopropanolamine, and the concentration of the formaldehyde solution is 30-40 wt%.

[0075] During the polymerization of melamine with formaldehyde solution, the resulting polymer may easily aggregate, leading to product instability or performance degradation. This method uses a weakly alkaline organic compound to adjust the pH of the solution, which improves the polymer's dispersibility in the aqueous medium and prevents aggregation. Furthermore, the use of a low-concentration formaldehyde solution ensures the safety of the preparation method and avoids unnecessary harm to human health.

[0076] To further clarify, in step B, the pH of the solution is 3-4, and the acid-base regulator is citric acid and sodium hydroxide.

[0077] To further explain, in step C, the amount of emulsifier added is 1 to 3 wt% of the total amount of the emulsifier and the sunflower seed oil, the emulsification speed is 1000 to 1500 rpm, the emulsification temperature is 50 to 70°C, and the emulsification reaction time is 20 to 40 min.

[0078] This is to improve the stability and uniformity of the emulsion system.

[0079] To further clarify, in step C, the emulsifier is a lipophilic emulsifier, and the lipophilic emulsifier is any one of sorbitan monooleate, propylene glycol monolaurate, sorbitan monostearate, and diethylene glycol fatty acid ester.

[0080] This scheme uses a lipophilic emulsifier, which has a good affinity with the oil phase dispersion medium and can stabilize the dispersion of the aqueous phase in the oil phase.

[0081] To elaborate further, step E specifically includes:

[0082] The mixture of single-component capsules and sunflower seed oil was centrifuged at a speed of 1500-2500 rpm for 5-10 min.

[0083] After washing the bottom precipitate obtained after centrifugation at least three times with solvent and deionized water, the precipitate was filtered using an oil-free diaphragm vacuum filter at -0.05 to -0.1 MPa to obtain the washed material.

[0084] The washed material was placed in a vacuum drying oven for drying to obtain single-component capsules. The drying temperature was 50-70°C and the drying time was 12-24 hours.

[0085] The solvent is either ethanol or ethyl acetate.

[0086] It is worth noting that this solution specifically optimizes the filtration pressure of the vacuum filter, which effectively ensures the yield of single-component capsules. As a further improvement in this embodiment, the solvent is ethyl acetate, which can better dissolve sunflower seed oil, thereby enhancing the washing effect.

[0087] A single-component capsule for chemical mechanical polishing is prepared using the above-described method for preparing a single-component capsule for chemical mechanical polishing, wherein the core material of the single-component capsule is any raw material that generates a strong oxidizing substance, and the wall material of the single-component capsule is melamine-formaldehyde resin.

[0088] An application of a single-component capsule for chemical mechanical polishing, comprising the following steps:

[0089] (1) Add the single-component capsules to the polishing slurry to prepare a single-component capsule dispersion;

[0090] (2) During the chemical mechanical polishing process, the single-component capsule dispersion is continuously supplied to the polishing pad in the polishing liquid;

[0091] The polishing slurry includes a polishing base liquid and another raw material that generates a strong oxidizing substance. The core material of the single-component capsule reacts with the other raw material in the polishing slurry that generates a strong oxidizing substance to generate a strong oxidizing substance.

[0092] The polishing fluid includes a polishing base fluid and abrasive.

[0093] This solution also proposes an application of the aforementioned single-component capsules in chemical mechanical polishing. This facilitates the low-cost, controllable, and efficient removal of strong oxidizing substances from hard and brittle material surfaces while ensuring a stable and continuous supply and efficient utilization of these substances. It also effectively guarantees the processing effect on hard and brittle material surfaces, resulting in a smooth surface with minimal damage. Furthermore, by controlling the capsule concentration, delivery rate, and polishing time, the release rate of the core material components within the capsule can be effectively controlled, thereby controlling the generation rate of strong oxidizing substances and achieving controllable and efficient removal from hard and brittle material surfaces.

[0094] It should be noted that when using the single-component capsules of this solution to perform chemical mechanical polishing on hard and brittle material workpieces, the aforementioned hard and brittle material workpieces may include silicon carbide, gallium nitride, sapphire, and diamond, and are not limited here.

[0095] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0096] Example 1

[0097] A. Add 0.97g of melamine and 1.87g of 37wt% formaldehyde solution to 7mL of deionized water, then add triethanolamine until the pH of the solution is 8-9. Stir the reaction at 70℃ and 300rpm for 15min to obtain a melamine-formaldehyde resin prepolymer solution, and cool it to 20-30℃ for later use.

[0098] B. Add 1g of ferrous sulfate heptahydrate to the cooled melamine-formaldehyde resin prepolymer solution, stir, and then add citric acid and sodium hydroxide to adjust the pH of the solution to 3-4 to obtain an acidic prepolymer.

[0099] C. Dissolve 3g of the lipophilic emulsifier sorbitan monooleate in sunflower seed oil, stir, and then add the acidic prepolymer. After emulsification, a single-component capsule emulsion is obtained. The emulsification speed is 1200 rpm, the emulsification temperature is 60℃, the emulsification reaction time is 30 min, and the mixing ratio of the melamine-formaldehyde resin prepolymer solution in step B to the sunflower seed oil in step C is 1:25.

[0100] D. Place the single-component capsule emulsion in an Erlenmeyer flask and stir at 450 rpm for 2 hours at room temperature to obtain the melamine-formaldehyde resin polymer generated by polycondensation reaction.

[0101] Melamine-formaldehyde resin polymer was placed in a water bath and stirred at 450 rpm for 1 hour at 55°C, and then stirred at 450 rpm for 5 hours at 75°C to obtain a mixture of single-component capsules and sunflower seed oil produced by in-situ polymerization.

[0102] E. Centrifuge the mixture of single-component capsules and sunflower seed oil at a speed of 2500 rpm for 5 min.

[0103] The bottom precipitate obtained after centrifugation was washed three times with ethyl acetate and deionized water, and then filtered using an oil-free diaphragm vacuum filter at -0.05 MPa to obtain the washed material.

[0104] The washed material was placed in a vacuum drying oven for drying to obtain single-component capsules. The drying temperature was 60°C, and the drying time was 12 hours. The core material of the single-component capsules was ferrous sulfate, and the wall material was melamine-formaldehyde resin.

[0105] like Figure 1 The diagram shows the preparation process of Example 1. The components are: 1-melamine, 2-deionized water, 3-formaldehyde solution, 4-ferrous sulfate heptahydrate, 5-melamine-formaldehyde resin prepolymer solution, 6-acidic prepolymer, 7-sunflower seed oil, 8-lipophilic emulsifier, 9-single-component capsule emulsion, 10-ferrous sulfate, and 11-melamine-formaldehyde resin.

[0106] like Figure 2The diagram illustrates the formation principle of the single-component capsule prepared in Example 1. As shown, melamine reacts with formaldehyde to form trimethylolmelamine. The hydroxymethyl group (-CH2OH) in trimethylolmelamine undergoes a condensation reaction under acidic conditions, forming an ether bond (-O-). Subsequently, under heating conditions, the formaldehyde molecule (-HCHO) is removed, forming a methylene bond (-CH2-). Simultaneously, unreacted active hydrogen atoms in the hydroxymethyl group and imino group (-NH-) of trimethylolmelamine also condense to form a methylene bond. With further polymerization of trimethylolmelamine and the above-mentioned products, the crosslinking index of the polymer gradually increases, the molecular weight gradually increases, and the solubility decreases. At this point, they gradually migrate to the oil-water interface, begin to deposit and grow. Finally, the crosslinked polymer network forms a shell that completely covers the droplet containing the core material, forming a single-component capsule.

[0107] like Figure 3 The image shown is a SEM image of the single-component capsules prepared in Example 1.

[0108] like Figure 4 The figure shown is a particle size distribution diagram of the single-component capsules prepared in Example 1.

[0109] like Figure 5 The image shows the FT-IR spectra of melamine-formaldehyde resin, single-component capsules, and ferrous sulfate heptahydrate core material in Example 1. As can be seen from the image, the infrared spectrum of the prepared FeSO4 capsules also includes the FeSO4 core material at 1105 cm⁻¹. -1 and 614cm -1 The characteristic peaks appearing at [location] and the melamine-formaldehyde resin in the wall material at 3333, 1555, 1331, 814, and 787 cm⁻¹ -1 The characteristic peaks appearing at the point prove that FeSO4 was successfully encapsulated inside the melamine-formaldehyde resin and formed FeSO4 capsules.

[0110] Chemical mechanical polishing experiment:

[0111] (1) Add the single-component capsule with ferrous sulfate as the core material to the polishing slurry containing H2O2 to prepare a single-component capsule dispersion.

[0112] (2) During the chemical mechanical polishing process, the single-component capsule dispersion is continuously supplied to the polishing pad in the polishing slurry containing abrasive.

[0113] like Figure 6 The diagram shows the processing principle of chemical mechanical polishing. In the diagram, 12-polishing pad, 13-hard and brittle workpiece, 14-abrasive, 15-H2O2, 16-ferrous sulfate, 17-broken single-component capsule wall material, 18-strong oxidizing substance produced by the reaction of H2O2 and ferrous sulfate, and 19-oxide layer.

[0114] Under the polishing pressure at the processing interface, the ferrous sulfate capsules break down and release ferrous sulfate, which reacts with H2O2 to generate ·OH, causing the workpiece surface to corrode and oxidize into a softer oxide layer. Then, the oxide layer is mechanically removed by abrasive. By changing the concentration of ferrous sulfate capsules in the polishing slurry, the oxidation corrosion rate and the mechanical removal rate are dynamically balanced, achieving high-efficiency polishing of hard and brittle materials.

[0115] Example 2

[0116] A. Add 0.97g of melamine and 1.87g of 37wt% formaldehyde solution to 7mL of deionized water, then add diethanolamine until the pH of the solution is 8-9. Stir the reaction at 60℃ and 500rpm for 10min to obtain a melamine-formaldehyde resin prepolymer solution, and cool it to 20-30℃ for later use.

[0117] B. Add 1.5g of hydrogen peroxide to the cooled melamine-formaldehyde resin prepolymer solution, stir, and then add citric acid and sodium hydroxide to adjust the pH of the solution to 3-4 to obtain an acidic prepolymer.

[0118] C. Dissolve 4.5g of lipophilic emulsifier propylene glycol monolaurate in sunflower seed oil, stir, and then add acidic prepolymer. After emulsification, a single-component capsule emulsion is obtained. The emulsification speed is 1500rpm, the emulsification temperature is 50℃, the emulsification reaction time is 20min, and the mixing ratio of melamine-formaldehyde resin prepolymer solution in step B to sunflower seed oil in step C is 1:25.

[0119] D. Place the single-component capsule emulsion in an Erlenmeyer flask and stir at 300 rpm for 2.5 h at room temperature to obtain the melamine-formaldehyde resin polymer generated by polycondensation reaction.

[0120] Melamine-formaldehyde resin polymer was placed in a water bath and stirred at 300 rpm for 1.5 h at 60 °C, and then stirred at 300 rpm for 6 h at 80 °C to obtain a mixture of single-component capsules and sunflower seed oil produced by in-situ polymerization.

[0121] E. Centrifuge the mixture of single-component capsules and sunflower seed oil at a speed of 1500 rpm for 10 min.

[0122] The bottom precipitate obtained after centrifugation was washed three times with ethyl acetate and deionized water, and then filtered using an oil-free diaphragm vacuum filter at -0.1 MPa to obtain the washed material.

[0123] The washed material was placed in a vacuum drying oven for drying to obtain single-component capsules. The drying temperature was 50°C, and the drying time was 24 hours. The core material of the single-component capsules was hydrogen peroxide, and the wall material was melamine-formaldehyde resin.

[0124] Chemical mechanical polishing experiment:

[0125] (1) Add a single-component capsule with hydrogen peroxide as the core material to a solution containing Fe 2+ The polishing slurry was prepared into a single-component capsule dispersion;

[0126] (2) During the chemical mechanical polishing process, the single-component capsule dispersion is continuously supplied to the polishing pad in the polishing slurry containing abrasive.

[0127] Under the polishing pressure at the processing interface, the hydrogen peroxide capsule breaks down, releasing hydrogen peroxide and Fe. 2+ The reaction generates ·OH, which causes the workpiece surface to corrode and oxidize into a softer oxide layer. The oxide layer is then mechanically removed using abrasives. By changing the concentration of hydrogen peroxide capsules in the polishing slurry, the oxidation corrosion rate and the mechanical removal rate are dynamically balanced, achieving high-efficiency polishing of hard and brittle materials.

[0128] Comparative Example 1

[0129] Compared to Example 1, in step A, the amount of melamine added was 1.94 g, the amount of 37 wt% formaldehyde solution added was 3.74 g, and the amount of deionized water used to dissolve the melamine and formaldehyde solutions was 14 mL. In step B, the mass of ferrous sulfate heptahydrate core material added was 1.5 g. The mixing ratio of the melamine-formaldehyde resin prepolymer solution in step B and the sunflower seed oil in step C was 4:25. The remaining steps and parameters were the same as in Example 1.

[0130] like Figure 7 The image shown is a SEM image of the single-component capsules prepared in Comparative Example 1. Figure 8 The figure shows the particle size distribution of the single-component capsules prepared in Comparative Example 1. As can be seen from the figure, due to the unreasonable setting of the water-oil ratio, some capsules adhered together and agglomerated, forming some irregular blocky capsules of about 46 μm.

[0131] Comparative Example 2

[0132] Compared to Example 1, the stirring rate of the in-situ polymerization reaction in step D was 200 rpm. The remaining steps and parameters were the same as in Example 1.

[0133] like Figure 9The figure shows the particle size distribution of the single-component capsules prepared in Comparative Example 2. As can be seen from the figure, due to the unreasonable stirring rate, the prepared single-component capsules have two particle sizes of 0.9 μm and 5.9 μm, resulting in particle size gradation.

[0134] Comparative Example 3

[0135] Compared to Example 1, the stirring rate of the in-situ polymerization reaction in step D was 700 rpm. The remaining steps and parameters were the same as in Example 1.

[0136] like Figure 10 The figure shows the particle size distribution of the single-component capsules prepared in Comparative Example 3. As can be seen from the figure, due to the unreasonable stirring rate, the prepared single-component capsules have two particle sizes of 3.6 μm and 21 μm, resulting in particle size gradation.

[0137] In summary, this method can prepare micron-sized single-component capsules through in-situ polymerization. The synthesized capsules have a regular spherical morphology, smooth outer shell surface, no leakage pores, uniform particle size, and good dispersibility, and can be fully dispersed in chemical mechanical polishing slurry.

[0138] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a single-component capsule for chemical mechanical polishing, characterized in that, Includes the following steps: A. Melamine and formaldehyde solutions are added to deionized water, and then a weakly alkaline organic compound is added until the solution is alkaline. After heating and stirring, a melamine-formaldehyde resin prepolymer solution is obtained. B. Add the core material to the cooled melamine-formaldehyde resin prepolymer solution, stir, and then add an acid-base adjuster to adjust the pH of the solution to be acidic, thus obtaining an acidic prepolymer. C. Add the emulsifier to the sunflower seed oil, stir, then add the acidic prepolymer, and emulsify to obtain a single-component capsule emulsion; D. The single-component capsule emulsion is heated and stirred, and then polymerized in situ to obtain a mixture of single-component capsules and sunflower seed oil. E. The mixture of single-component capsules and sunflower seed oil is centrifuged, washed, filtered and vacuum dried in sequence to obtain single-component capsules. The core material of the single-component capsules is any raw material that generates strong oxidizing substances, and the wall material of the single-component capsules is melamine-formaldehyde resin. in, In step A, the molar ratio of melamine to formaldehyde solution is 1:(1.5-4), the pH of the solution is 8-9, the heating temperature is 60-80℃, the stirring speed is 150-500 rpm, and the stirring time is 10-20 min. In step B, the temperature of the cooled melamine-formaldehyde resin prepolymer solution is 20-30°C. According to the volume ratio, the mixing ratio of the melamine-formaldehyde resin prepolymer solution in step B and the sunflower seed oil in step C is (1-3):

25. In step C, the amount of emulsifier added is 1-3 wt% of the total amount of the emulsifier and the sunflower seed oil; the emulsification speed is 1000-1500 rpm; the emulsification temperature is 50-70℃; and the emulsification reaction time is 20-40 min; the emulsifier is a lipophilic emulsifier. Step D specifically includes: The single-component capsule emulsion was placed in an Erlenmeyer flask and stirred at a stirring rate of 300–600 rpm for 1.5–2.5 h at room temperature to obtain a melamine-formaldehyde resin polymer generated by polycondensation reaction. Melamine-formaldehyde resin polymer was placed in a water bath and stirred at 300-600 rpm for 0.5-1.5 h at 50-60°C, and then stirred at 300-600 rpm for 4-6 h at 70-80°C to obtain a mixture of single-component capsules and sunflower seed oil produced by in-situ polymerization.

2. The method for preparing a single-component capsule for chemical mechanical polishing according to claim 1, characterized in that, In step A, the weakly basic organic compound is any one of triethanolamine, ethanolamine, diethanolamine, isopropanolamine, and diisopropanolamine, and the concentration of the formaldehyde solution is 30-40 wt%.

3. The method for preparing a single-component capsule for chemical mechanical polishing according to claim 1, characterized in that, In step B, the pH of the solution is 3-4, and the acid-base regulator is citric acid and sodium hydroxide.

4. The method for preparing a single-component capsule for chemical mechanical polishing according to claim 1, characterized in that, In step C, the lipophilic emulsifier is any one of sorbitan monooleate, propylene glycol monolaurate, sorbitan monostearate, and diethylene glycol fatty acid ester.

5. The method for preparing a single-component capsule for chemical mechanical polishing according to claim 1, characterized in that, Step E specifically includes: The mixture of single-component capsules and sunflower seed oil was centrifuged at a speed of 1500-2500 rpm for 5-10 min. After washing the bottom precipitate obtained after centrifugation at least three times with solvent and deionized water, the precipitate was filtered using an oil-free diaphragm vacuum filter at -0.05 to -0.1 MPa to obtain the washed material. The washed material was placed in a vacuum drying oven for drying to obtain single-component capsules. The drying temperature was 50-70°C and the drying time was 12-24 hours. The solvent is either ethanol or ethyl acetate.

6. A single-component capsule for chemical mechanical polishing, characterized in that, The capsule is prepared using the method for preparing a single-component capsule for chemical mechanical polishing according to any one of claims 1 to 5, wherein the core material of the single-component capsule is any raw material that generates a strong oxidizing substance, and the wall material of the single-component capsule is melamine-formaldehyde resin.

7. The application of a single-component capsule for chemical mechanical polishing, characterized in that, Using the single-component capsule for chemical mechanical polishing as described in claim 6 includes the following steps: (1) Add the single-component capsules to the polishing slurry to prepare a single-component capsule dispersion; (2) During the chemical mechanical polishing process, the single-component capsule dispersion is continuously supplied to the polishing pad in the polishing slurry; The polishing slurry includes a polishing base liquid and another raw material that generates a strong oxidizing substance. The core material of the single-component capsule reacts with the other raw material in the polishing slurry that generates a strong oxidizing substance to generate a strong oxidizing substance. The polishing fluid includes a polishing base fluid and abrasive.

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