Neutral antioxidant polishing solution for copper materials and method for preparing the same

Abstract

This invention discloses a neutral antioxidant polishing slurry suitable for copper materials and its preparation method. The polishing slurry has a pH value of 6.5–7.5 and comprises: alkaline lignin, an oxidant, abrasive particles, a pH adjuster, and a carrier. This polishing slurry is not only simple in composition, free of toxic and harmful elements, environmentally friendly, and has minimal corrosive and destructive effects on equipment, but also exhibits high polishing removal efficiency. Furthermore, it allows copper materials to maintain a low oxygen content and good antioxidant properties during polishing, resulting in a low surface roughness after polishing.

Description

Technical Field

[0001] This invention belongs to the field of metal processing, and more specifically, relates to a neutral antioxidant polishing slurry suitable for copper materials and its preparation method. Background Technology

[0002] Chemical mechanical polishing (CMP) is a technique that combines mechanical polishing with the addition of appropriate chemical additives based on the surface shape, achieving enhanced and selective polishing. In the copper planarization industry, CMP is currently the only method that can simultaneously achieve both local and global planarization, and it is also the most widely used planarization method. CMP avoids the surface damage caused by pure mechanical polishing, as well as the problems of slow speed, poor surface smoothness, and poor polishing consistency associated with pure chemical polishing.

[0003] Copper possesses excellent thermal and electrical conductivity, good plasticity, ease of processing, corrosion resistance, non-magnetic properties, and is aesthetically pleasing and durable. Its thermal conductivity is second only to gold and silver. Furthermore, copper exhibits good processing, casting, welding, and machinability, leading to its widespread application. However, as a non-ferrous metal, copper's molecules are relatively reactive and easily oxidized during various production processes. Oxidation during use can severely impact its performance and stability. Currently, the "copper chip" revolution in the microelectronics industry is underway, with high-purity copper widely used in the manufacture of anodes, resonant cavities, slow-wave lines, and collectors for microwave vacuum electronic devices. However, copper readily reacts with oxygen at room temperature. Friction during polishing increases temperature, significantly accelerating the oxidation rate. Without subsequent anti-oxidation measures, surface oxidation intensifies after polishing, severely affecting copper's electrical and thermal conductivity, signal transmission performance, and other properties. Moreover, since copper oxidation in air is unavoidable, copper materials are highly susceptible to oxidation and discoloration during production, storage, and transportation, significantly impacting their electrical and thermal conductivity, plasticity, processing performance, and overall product usability, resulting in substantial negative consequences for practical applications. Therefore, it is crucial to maintain a low level of oxidation in the copper material during the polishing process while improving the oxidation resistance of the copper surface. Summary of the Invention

[0004] This invention is primarily based on the following problems and findings:

[0005] Traditional copper CMP polishing slurries are mainly divided into acidic and alkaline slurries. Among existing acidic copper polishing slurries, some propose using inorganic or organic acids as solvents and hydrogen peroxide to oxidize the copper surface, resulting in a brighter finish. Others propose using slurries containing abrasives, oxidants, deionized water, composite inhibitors, composite complexing agents, and silica sol bridging agents, controlling the pH value to no greater than 4, enabling high copper removal rates and high surface uniformity under pressures below 1 psi. Still others propose using slurries containing abrasives, oxidants, deionized water, inhibitors, complexing agents, and silica sol stabilizers, controlling the pH value to 5–7, achieving efficient copper removal under pressures below 1 psi while maintaining high surface precision and minimizing surface particle residue and contamination. However, acidic polishing slurries are highly corrosive, requiring sophisticated equipment, and generally necessitate the addition of corrosion inhibitors to improve selectivity on the polished surface. However, the addition of corrosion inhibitors increases the toxicity of the slurry, limiting its application scenarios and scope.

[0006] Among existing alkaline polishing slurries, some propose using polishing agents comprising silicon dioxide abrasive particles, hydrogen peroxide, sodium nitrate, and sodium m-nitrobenzenesulfonate, with ethylenediamine as a pH adjuster to control the pH of the polishing slurry at 7-9. The complexation effect of ethylenediamine accelerates copper dissolution, while having no volatilization and minimal corrosiveness to equipment. Other proposals suggest polishing slurries comprising abrasive particles, corrosion inhibitors, complexing agents, wetting agents, pH adjusters, and oxidants. These slurries effectively suppress the polishing rate of copper, and leave almost no organic residue on the copper surface after polishing, overcoming the problem of organic residue associated with benzotriazole corrosion inhibitors and improving the surface quality of the polished wafer. However, the polishing efficiency of alkaline polishing slurries is significantly lower than that of acidic polishing slurries, which also limits their application.

[0007] Although the aforementioned acidic or alkaline polishing slurries have good solubility, a wide range of oxidant options, and high polishing rates, they do not improve the oxidation resistance of copper surfaces, thus affecting the electrical and thermal conductivity or plastic processing properties of copper materials in subsequent use. Regarding the research on the oxidation resistance of polishing slurries, some studies have proposed adding a small amount of triethanolamine antioxidant to the polishing slurry, but they have not explained the role and effect of triethanolamine in the polishing process. Other studies have proposed using polishing slurries that include antioxidant color-changing agents, but these mainly improve the stability and recycling rate of the polishing slurry, ensuring that the polishing slurry does not change color over a long period of recycling, without mentioning any improvement in the oxidation resistance of copper material surfaces.

[0008] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, one objective of this invention is to provide a neutral, antioxidant polishing slurry suitable for copper materials and its preparation method. This polishing slurry not only has a simple composition, does not contain toxic or harmful elements, is environmentally friendly, has minimal corrosive and destructive effects on equipment, and has high polishing removal efficiency, but also allows the copper material to maintain a low oxygen content and good antioxidant properties during the polishing process, resulting in a low surface roughness after polishing.

[0009] In one aspect of the invention, a polishing slurry suitable for copper materials is provided. According to an embodiment of the invention, the polishing slurry comprises: alkaline lignin, an oxidizing agent, abrasive particles, a pH adjuster, and a carrier, wherein the pH value of the polishing slurry is 6.5–7.5.

[0010] The polishing solution according to the above embodiments of the present invention has at least the following beneficial effects: 1) By adding alkaline lignin, it can work synergistically with the oxidant. First, the oxidant reacts with the copper material surface to generate copper oxide. Then, the alkaline lignin chelates with the copper oxide to generate an easily removable complex. This not only reduces the roughness of the copper surface but also improves the polishing efficiency. Simultaneously, during the polishing process, the alkaline lignin and its complexes adhere to the copper material surface, improving the oxidation resistance of the freshly exposed copper surface; 2) Under pH conditions of 6.5–7.5, it facilitates the interaction between alkaline lignin and abrasive particles. This improves the dispersion of abrasive particles in the polishing slurry, reduces the risk of damage to the copper material surface caused by abrasive particle sedimentation or agglomeration during polishing, and enhances the storage and use stability of the polishing slurry as well as the smoothness of the material surface after polishing; 3) By controlling the pH of the polishing slurry to 6.5-7.5, corrosion to equipment can be effectively avoided or reduced, while also reducing its application limitations, increasing application sites, and expanding the application range; 4) The polishing slurry has a simple composition, does not contain toxic or harmful elements, and does not require the addition of corrosion inhibitors. This not only simplifies the process flow and facilitates industrial production, but also further ensures the stability of the polishing equipment.

[0011] In addition, the polishing slurry suitable for copper materials according to the above embodiments of the present invention may also have the following additional technical features:

[0012] In some embodiments of the present invention, the content of alkaline lignin is 1 part by weight to 10 parts by weight; the content of oxidant is 0.1 part by weight to 2 parts by weight; and the content of abrasive particles is 1 part by weight to 30 parts by weight. This is more conducive to enhancing the synergistic effect of alkaline lignin, oxidant and abrasive particles, improving the removal efficiency of polishing liquid, and improving the oxidation resistance and surface quality of polished copper materials.

[0013] In some embodiments of the present invention, the content of alkaline lignin is 2.5 parts by weight to 5 parts by weight; the content of oxidant is 1 part by weight to 1.5 parts by weight; and the content of abrasive particles is 10 parts by weight to 15 parts by weight.

[0014] In some embodiments of the present invention, the mass ratio of the alkaline lignin to the oxidant is (1.5 to 5):1, which is more conducive to improving the synergistic effect of alkaline lignin and oxidant, further improving the surface quality of the polished copper material, and reducing the surface oxygen content.

[0015] In some embodiments of the present invention, the polishing liquid does not contain chlorine, which helps to avoid chloride ions damaging the smoothness of the copper material surface and affecting the appearance quality of the polishing material.

[0016] In some embodiments of the present invention, the pH value of the polishing solution is 6.8 to 7.2.

[0017] In some embodiments of the present invention, the oxidant includes at least one of hydrogen peroxide, ferric nitrate, ammonia, ammonium nitrate, potassium nitrate, potassium persulfate, and potassium permanganate.

[0018] In some embodiments of the present invention, the abrasive particles include at least one of silicon oxide, cerium oxide, aluminum oxide, and silicon carbide.

[0019] In some embodiments of the present invention, the average particle size of the abrasive grains is 30 nm to 150 nm.

[0020] In some embodiments of the present invention, the pH adjuster includes at least one of sulfuric acid, formic acid, acetic acid, oxalic acid, and lactic acid.

[0021] In some embodiments of the present invention, the carrier comprises deionized water.

[0022] In another aspect of the invention, a method for preparing the aforementioned polishing slurry is provided. According to an embodiment of the invention, the method includes: mixing alkaline lignin, abrasive particles, an oxidant, a carrier, and a pH adjuster to obtain a polishing slurry with a pH value of 6.5–7.5. Compared with the prior art, this method is not only simple and suitable for large-scale production, but also produces an environmentally friendly polishing slurry with minimal corrosive damage to equipment and high polishing removal efficiency. Simultaneously, it allows copper materials to maintain a low oxygen content and good oxidation resistance during polishing, resulting in a high surface smoothness after polishing.

[0023] In some embodiments of the present invention, the method includes: (1) performing a first mixing treatment on the alkaline lignin and the carrier to obtain an alkaline lignin solution; (2) performing a second mixing treatment on the abrasive particles and the carrier to obtain an abrasive particle dispersion; (3) performing a third mixing treatment on the alkaline lignin solution and the abrasive particle dispersion to obtain a mixture of alkaline lignin and abrasive particles; (4) performing a fourth mixing treatment on the mixture of alkaline lignin and abrasive particles with the oxidant to obtain a blended dispersion; and (5) mixing the blended dispersion with a pH adjuster to obtain a polishing liquid with a pH value of 6.5 to 7.5.

[0024] In some embodiments of the present invention, in step (1), the pH value of the alkaline lignin solution is not less than 8.5, which is more conducive to improving the solubility of alkaline lignin in the carrier.

[0025] In some embodiments of the present invention, in step (1), the alkaline lignin, the carrier and the alkaline solution are subjected to the first mixing treatment to obtain the alkaline lignin solution.

[0026] In another aspect, the present invention provides a method for polishing copper materials. According to embodiments of the present invention, the method uses the aforementioned polishing slurry or a polishing slurry prepared by the aforementioned method to polish the surface of the copper material. Compared with the prior art, this polishing method has less corrosive and destructive effect on the polishing equipment, higher removal efficiency on the surface of the copper material, and allows the copper material to maintain a low oxygen content during the polishing process, resulting in polished copper material with better oxidation resistance and lower roughness.

[0027] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0029] Figure 1 This is a schematic diagram of the morphology of the surface of a polished copper sheet according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the morphology of the polished copper sheet surface according to Embodiment 1 of the present invention;

[0031] Figure 3 This is a schematic diagram of the morphology of the polished copper sheet surface according to Embodiment 2 of the present invention;

[0032] Figure 4 This is a schematic diagram of the morphology of the polished copper sheet surface according to Embodiment 3 of the present invention. Detailed Implementation

[0033] The embodiments of the present invention are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0034] In one aspect of the invention, a polishing slurry suitable for copper materials is provided. According to embodiments of the invention, the pH value of the polishing slurry is 6.5–7.5, for example, the pH value of the polishing slurry can be 6.7, 7, or 7.3, etc. The polishing slurry includes alkaline lignin, an oxidizing agent, abrasive particles, a pH adjuster, and a carrier. This polishing slurry has a simple composition, contains no toxic or harmful elements, requires no corrosion inhibitors, and is widely applicable. The alkaline lignin synergistically interacts with the oxidant. After the oxidant reacts with the copper surface to form copper oxides, the alkaline lignin chelates with these oxides to form more easily removable complexes, improving polishing efficiency and effect. Simultaneously, during polishing, the alkaline lignin and its complexes adhere to the copper surface, enhancing its oxidation resistance. Furthermore, a pH of 6.5–7.5 facilitates the interaction between alkaline lignin and abrasive particles, improving particle dispersion in the slurry, preventing or reducing sedimentation or agglomeration, and enhancing the storage and stability of the slurry, as well as the smoothness of the polished surface. Additionally, using a near-neutral slurry effectively expands its application range, reduces corrosion to polishing equipment, and makes the use and post-treatment processes more environmentally friendly. Furthermore, according to some specific examples of the present invention, the pH value of the polishing solution can be 6.8 to 7.2, for example, 6.9, 7 or 7.1, which is more conducive to enhancing the interaction between alkaline lignin and abrasive particles, and further reducing the roughness of the copper material surface after polishing.

[0035] According to embodiments of the present invention, the content of alkaline lignin in the polishing solution can be 1 part by weight to 10 parts by weight, for example, 2 parts by weight, 3 parts by weight, 5 parts by weight, 7 parts by weight, or 9 parts by weight; the content of oxidant can be 0.1 parts by weight to 2 parts by weight, for example, 0.3 parts by weight, 0.5 parts by weight, 1.2 parts by weight, 1.5 parts by weight, or 1.8 parts by weight; the content of abrasive particles can be 1 part by weight to 30 parts by weight, for example, 5 parts by weight, 8 parts by weight, 16 parts by weight, 20 parts by weight, 24 parts by weight, or 28 parts by weight. The inventors have found that if the content of oxidant is too low, the polishing efficiency for removing copper materials is low, making it difficult to fully achieve oxidation of the copper material surface; if the content of oxidant is too high, it is easy to cause over-oxidation of the copper material surface, or even... Corrosion and blackening may occur. If the content of alkaline lignin is too low, on the one hand, the chelation with copper oxide may be insufficient, affecting polishing efficiency; on the other hand, the content of alkaline lignin adhering to the freshly exposed copper surface during polishing will be low, affecting the effect of alkaline lignin on improving the antioxidant properties of the polished copper material. If the content of alkaline lignin is too high, it is easy for alkaline lignin to be insufficiently dissolved in the polishing solution, which may not only affect the storage and use stability of the polishing solution, but also easily damage the processing uniformity of the copper material surface. If the content of abrasive grains is too low, it is difficult to produce a good mechanical grinding effect, resulting in a low polishing depth on the copper material surface, affecting the polishing effect and efficiency. If the content of abrasive grains is too high, the abrasive grains are prone to agglomeration, which will increase the risk of scratches or pits on the copper surface. This invention, by controlling the content of alkaline lignin, oxidant and abrasive grains in the polishing solution within the above range, is more conducive to enhancing the synergistic effect of alkaline lignin with oxidant and abrasive grains, improving the removal efficiency of the polishing solution, and improving the antioxidant properties and surface quality of the polished copper material.

[0036] Furthermore, according to embodiments of the present invention, the content of alkaline lignin in the polishing solution can be 2.5 parts by weight to 5 parts by weight, for example, 2.8 parts by weight, 3.2 parts by weight, 3.8 parts by weight, 4.4 parts by weight, or 4.8 parts by weight, which is more conducive to improving the oxidation resistance of the copper material surface while ensuring the polishing effect, and also taking into account the storage and use stability of the polishing solution; the content of oxidant can be 1 part by weight to 1.5 parts by weight, for example, 1.1 parts by weight, 1.2 parts by weight, 1.3 parts by weight, or 1.4 parts by weight, which can further improve the polishing efficiency and reduce the risk of excessive corrosion; the content of abrasive particles can be 10 parts by weight to 15 parts by weight, for example, 11 parts by weight, 12 parts by weight, 13 parts by weight, or 14 parts by weight, which is more conducive to taking into account the dispersion and grinding efficiency of abrasive particles, and further improving the uniformity and stability of mechanical action.

[0037] According to embodiments of the present invention, the mass ratio of alkaline lignin to oxidant in the polishing solution can be (1.5-5):1, for example, it can be 1.8 / 1, 2 / 1, 2.4 / 1, 2.8 / 1, 3.4 / 1, 3.8 / 1, 4.4 / 1, or 4.8 / 1, etc. The inventors have found that if the mass ratio of alkaline lignin to oxidant is too small, on the one hand, after the oxidant oxidizes the surface of the copper material, it is easy to cause insufficient chelation between alkaline lignin and copper oxide, which will not only affect the polishing efficiency and removal effect, but may also lead to an increase in the oxygen content on the surface of the copper material. On the other hand, if the relative content of oxidant is too high, more metallic copper will be removed in the reaction, which may affect the smoothness of the copper material surface and is not conducive to the reduction of surface roughness after polishing. If the mass ratio of alkaline lignin to oxidant is too high, on the one hand, it is easy to cause insufficient dissolution of alkaline lignin, affecting the storage and use stability of the polishing solution. On the other hand, if the relative content of oxidant is too low, the removal efficiency of copper material will decrease, and it will also affect the degree of oxidation of the copper material surface, thereby affecting the polishing quality. By controlling the mass ratio of alkaline lignin to oxidant in the polishing solution within the above-mentioned range, this invention is more conducive to improving the synergistic effect of alkaline lignin and oxidant, further improving the surface quality of the polished copper material, and reducing its surface oxygen content.

[0038] According to embodiments of the present invention, the polishing solution may be chlorine-free. For example, the polishing solution may use chlorine-free oxidants and chlorine-free acidic regulators. The inventors have discovered that because chloride ions are small in size, highly reactive, and have a strong ability to penetrate oxide films, they easily cause damage points in metals. These damage points become active-state pits (anodes), forming a short-circuit cell with the surrounding passive surface (cathode), leading to deep-penetrating corrosion and the formation of small holes. Furthermore, chlorine-containing solutions are also prone to crevice corrosion. The crevice corrosion mechanism is due to the formation of extremely small gaps between materials, hindering the convection of media inside and outside the crevice, thus forming a closed corrosion cell. Therefore, if the polishing solution contains chlorine, it easily damages the surface smoothness of copper materials, affecting the appearance quality of the polished material. Furthermore, the present invention does not impose any particular restrictions on the specific components of the oxidant and pH adjuster. Those skilled in the art can flexibly select them according to actual conditions. For example, the oxidant may include at least one of hydrogen peroxide, ferric nitrate, ammonia, ammonium nitrate, potassium nitrate, potassium persulfate, and potassium permanganate, preferably hydrogen peroxide, which is more conducive to achieving better oxidation effect and faster polishing efficiency. The pH adjuster may include at least one of sulfuric acid, formic acid, acetic acid, oxalic acid, and lactic acid, preferably acetic acid, which is not only conducive to controlling costs, but also conducive to ensuring the controllability and sensitivity of pH adjustment. In addition, the present invention does not impose any particular restrictions on the content of pH adjuster in the polishing solution. For example, the content of pH adjuster may be 0.01 parts by weight to 0.5 parts by weight, preferably 0.1 parts by weight to 0.15 parts by weight, which not only allows for obtaining a polishing solution with a pH in the above range, but also helps to avoid affecting the performance and polishing effect of the polishing solution due to excessive addition of pH adjuster.

[0039] According to embodiments of the present invention, there are no particular limitations on the specific type of abrasive particles. Those skilled in the art can flexibly select the appropriate type based on actual conditions. For example, the abrasive particles may include at least one of silicon oxide, cerium oxide, aluminum oxide, and silicon carbide, preferably silicon oxide, which is more beneficial for improving the grinding and polishing effect on copper materials. Furthermore, according to some specific examples of the present invention, the average particle size of the abrasive particles can be 30nm to 150nm, for example, 40nm, 60nm, 80nm, 120nm, or 140nm. The inventors have found that by controlling the average particle size of the abrasive particles within the above range, it is not only beneficial to avoid scratches or pits on the surface of the copper material due to excessively large abrasive particle size during polishing, but also beneficial to reduce the risk of agglomeration due to excessively small abrasive particle size, thereby improving the long-term stability and polishing effect of the polishing slurry. Additionally, it should be noted that there are no particular limitations on the dispersion form of the abrasive particles in the present invention. Those skilled in the art can flexibly select the appropriate form based on actual conditions. For example, the abrasive particles may be powder or sol.

[0040] According to an embodiment of the present invention, the carrier may include deionized water, which is more environmentally friendly and can further expand the application range of the polishing liquid and reduce the difficulty of preparation and post-processing.

[0041] In another aspect of the invention, a method for preparing the aforementioned polishing slurry is provided. According to an embodiment of the invention, the method includes: mixing alkaline lignin, abrasive particles, an oxidant, a carrier, and a pH adjuster to obtain a polishing slurry with a pH value of 6.5–7.5. Compared with the prior art, this method is not only simple and suitable for large-scale production, but also produces an environmentally friendly polishing slurry with minimal corrosive damage to equipment and high polishing removal efficiency. Simultaneously, it allows copper materials to maintain a low oxygen content and good oxidation resistance during polishing, resulting in a high surface smoothness after polishing.

[0042] According to an embodiment of the present invention, the method for preparing the above-mentioned polishing slurry may specifically include:

[0043] (1) The alkaline lignin is first mixed with the carrier to obtain an alkaline lignin solution. Specifically, the alkaline lignin can be added to deionized water and stirred thoroughly. The first mixing time can be no less than 25 minutes to ensure that the alkaline lignin is fully dissolved in the deionized water. It should be noted that the pH value of the obtained alkaline lignin solution can be no less than 8.5, which is more conducive to improving the solubility of alkaline lignin in deionized water. If the pH value of the obtained alkaline lignin solution is too low, an alkaline solution can be added to adjust the pH value of the alkaline lignin solution. It should be noted that there is no particular limitation on the specific type of alkaline solution in this invention. Those skilled in the art can choose flexibly according to the actual situation, such as sodium hydroxide or potassium hydroxide.

[0044] (2) The abrasive particles and the carrier are subjected to a second mixing treatment to obtain an abrasive particle dispersion. The time of the second mixing treatment can be no less than 2 hours in order to improve the dispersion uniformity of the abrasive particles in deionized water.

[0045] (3) The alkaline lignin solution obtained in step (1) and the abrasive dispersion obtained in step (2) are subjected to a third mixing treatment to obtain a mixture of alkaline lignin and abrasive particles. The time of the third mixing treatment can be no less than 3 hours, preferably 3 hours to 5 hours, for example, 4 hours.

[0046] (4) The mixture of alkaline lignin and abrasive particles obtained in step (3) is subjected to a fourth mixing treatment with an oxidant to obtain a co-mixed dispersion. The time of the fourth mixing treatment can be no less than 5 minutes in order to achieve full mixing of the oxidant with alkaline lignin and abrasive particles.

[0047] (5) Mix the blended dispersion obtained in step (4) with a pH adjuster to obtain a polishing liquid with a pH value of 6.5 to 7.5. Specifically, the pH adjuster can be slowly added to the mixture and stirred to adjust the pH value to 6.5 to 7.5 to obtain the polishing liquid.

[0048] In another aspect, the present invention provides a method for polishing copper materials. According to embodiments of the present invention, the method uses the aforementioned polishing slurry or a polishing slurry prepared by the aforementioned method to polish the surface of the copper material. Compared with the prior art, this polishing method has less corrosive and destructive effect on the polishing equipment, higher removal efficiency on the surface of the copper material, and allows the copper material to maintain a low oxygen content during the polishing process, resulting in polished copper material with better oxidation resistance and lower roughness.

[0049] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0050] Example 1

[0051] A polishing solution with a pH of 7 was obtained by mixing 2.5 wt% alkaline lignin, 15 wt% silica with an average particle size of 60 nm, 5 wt% hydrogen peroxide, 0.15 wt% acetic acid, and the balance water.

[0052] Examples 2-3

[0053] The differences from Comparative Example 1 are shown in Table 1.

[0054] Comparative Examples 1-11

[0055] The differences from Comparative Example 1 are shown in Table 1.

[0056] Table 1. Components and proportions of polishing solutions in Examples 1-3 and Comparative Examples 1-11

[0057]

[0058] Testing and Analysis

[0059] Under the same conditions, the polishing solutions prepared in Examples 1-3 and Comparative Examples 1-11 were used to polish copper sheets. The copper sheets were TU2 oxygen-free copper discs with a diameter of 2 cm and a thickness of 2 mm. Before polishing, 180-grit, 600-grit, and 1200-grit sandpaper were used sequentially on an automatic grinding machine for 30 seconds each. The surface morphology of the copper sheets after polishing is shown below. Figure 1As shown; the polishing pad used in the polishing process was SUBA600, the polishing machine was a Shenyang Kejing UNIPOL-1000S automatic pressure polishing machine, the polishing disc speed was 120 r / min, the polishing head speed was 30 r / min, the polishing time was 5 min, the polishing fluid flow rate was 75 mL / min, and the polishing pressure was 800 g / cm³. 2 The polishing temperature is 25℃. Taking Examples 1-3 as examples, the morphology of the copper sheet surface after polishing is as follows: Figures 2-4 As shown in Table 2, under the same conditions, the surface oxygen content of the copper sheet before and after polishing, the surface roughness of the copper sheet after polishing, and the material removal rate during the polishing process were measured. The test results are as follows: The test and calculation methods are as follows:

[0060] Surface roughness: The surface roughness of the copper sheet before and after polishing was measured using a surface profilometer (ZYGO NexView) manufactured by ZYGO Corporation, USA.

[0061] Surface oxygen content: The oxygen content of the copper sheet surface before and after polishing was measured using an X-ray energy dispersive spectrometer (X-EDS, FlatQuad) manufactured by Bruker GmbH, Germany.

[0062] Material Removal Rate: Three circular TU2 copper sheets with a diameter of 20mm were placed on a suction cup and polished simultaneously. The mass of the copper sheets was measured using a precision balance with a resolution of 0.01mg before and after chemical mechanical polishing (CMP). The material removal rate (MRR) was then calculated using the following formula: MRR = ΔmρSt, where Δm is the mass of the copper sheet before and after CMP; ρ is the density of the TU2 copper sheet, taken as 8.9g / cm³. 3 S is the area of ​​the polished copper sheet; t is the polishing time.

[0063] Table 2. Polishing fluid performance tests of Examples 1-3 and Comparative Examples 1-11

[0064]

[0065] Results and Discussion

[0066] Based on Examples 1-3, Comparative Examples 1-11, and the test results, it can be seen that the polishing solutions prepared in Examples 1-3, compared with Comparative Examples 1-11, not only have higher polishing removal efficiency but also lower surface roughness after polishing, and lower oxygen content on the surface of the polished copper sheet. Specifically, compared with Example 2, Comparative Examples 1-6 had incomplete addition of each component of the polishing solution, resulting in a lower material removal rate, higher surface roughness of the polished copper sheet, and poorer polishing effect. Among them, Comparative Examples 2, 3, and 6 did not add alkaline lignin, resulting in an increased oxygen content on the surface of the polished copper sheet. In addition, compared with Example 2, Comparative Examples 7-11 changed the pH value of the polishing solution. Comparative Examples 7-8 yielded acidic polishing solutions, which, although having a higher material removal rate, resulted in a worse surface roughness. Comparative Examples 9-11 yielded alkaline polishing solutions, which also increased the surface roughness of the polished copper sheet. Therefore, by using the polishing solutions prepared in the above examples of the present invention, the polishing efficiency, surface roughness, and surface oxygen content of copper materials can be balanced.

[0067] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0068] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A polishing slurry suitable for copper materials, characterized in that, include: The polishing solution contains alkaline lignin, an oxidizing agent, abrasive particles, a pH adjuster, and a carrier, wherein the pH value of the polishing solution is 6.5~7.5; The mass ratio of the alkaline lignin to the oxidant is (1.5~5):

1.

2. The polishing slurry according to claim 1, characterized in that, The content of alkaline lignin is 1 part by weight to 10 parts by weight; the content of oxidant is 0.1 part by weight to 2 parts by weight; and the content of abrasive particles is 1 part by weight to 30 parts by weight.

3. The polishing slurry according to claim 1, characterized in that, The content of alkaline lignin is 2.5 parts by weight to 5 parts by weight; the content of oxidant is 1 part by weight to 1.5 parts by weight; and the content of abrasive particles is 10 parts by weight to 15 parts by weight.

4. The polishing liquid according to any one of claims 1 to 3, characterized in that, The polishing solution does not contain chlorine; and / or, The pH value of the polishing solution is 6.8~7.

2.

5. The polishing liquid according to any one of claims 1 to 3, characterized in that, At least one of the following conditions must be met: The oxidant includes at least one of hydrogen peroxide, ferric nitrate, ammonia, ammonium nitrate, potassium nitrate, potassium persulfate, and potassium permanganate. The abrasive particles include at least one of silicon oxide, cerium oxide, aluminum oxide, and silicon carbide; The average particle size of the abrasive grains is 30nm~150nm; The pH adjuster includes at least one of sulfuric acid, formic acid, acetic acid, oxalic acid, and lactic acid; The carrier includes deionized water.

6. A method for preparing the polishing liquid according to any one of claims 1 to 5, characterized in that, include: Alkaline lignin, abrasive particles, oxidant, carrier, and pH adjuster are mixed and treated to obtain a polishing solution with a pH value of 6.5~7.

5.

7. The method according to claim 6, characterized in that, The method includes: (1) The alkaline lignin is subjected to a first mixing treatment with the carrier to obtain an alkaline lignin solution; (2) The abrasive particles and the carrier are subjected to a second mixing treatment to obtain an abrasive particle dispersion; (3) The alkaline lignin solution and the abrasive dispersion are subjected to a third mixing treatment to obtain a mixture of alkaline lignin and abrasive particles; (4) The mixture of alkaline lignin and abrasive particles is subjected to a fourth mixing treatment with the oxidant to obtain a blended dispersion; (5) The blended dispersion is mixed with a pH adjuster to obtain a polishing solution with a pH value of 6.5~7.

5.

8. The method according to claim 7, characterized in that, In step (1), the pH value of the alkaline lignin solution is not less than 8.5; and / or, In step (1), the alkaline lignin, the carrier, and the alkaline solution are subjected to the first mixing treatment to obtain the alkaline lignin solution.

9. A method for polishing copper materials, characterized in that, The surface of the copper material is polished using the polishing liquid according to any one of claims 1 to 5 or the polishing liquid prepared by the method according to any one of claims 6 to 8.

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