Boron-doped cerium oxide for polishing solution as well as preparation method and application of boron-doped cerium oxide

Abstract

The invention belongs to the field of polishing materials, and relates to boron-doped cerium oxide for a polishing solution as well as a preparation method and application of the boron-doped cerium oxide. In the boron-doped cerium oxide, the molar ratio of the boron element to the cerium element in the cerium oxide is 1: 1-1: 10. The boron-doped cerium oxide is prepared by carrying out co-precipitation reaction on cerium salt and a boron source to generate a precursor, and calcining the precursor. The boron element is introduced into cerium oxide crystal lattices, so that the problems of low chemical activity and poor polishing performance of traditional cerium oxide due to insufficient content of trivalent cerium are effectively solved. After boron is doped, an oxygen coordination environment in a cerium oxide crystal lattice is changed, part of oxygen atoms are converted from tetra-coordination combined with tetravalent cerium into tri-coordination combined with trivalent boron, and the structure change induces generation of more oxygen vacancies, so that the proportion of trivalent cerium in the material is remarkably increased.

Description

A boron-doped cerium oxide for polishing slurry, its preparation method and application Technical Field

[0001] This invention relates to the field of polishing materials technology, specifically to a boron-doped cerium oxide for polishing fluid, its preparation method, and its application. Background Technology

[0002] The rapid development of the information and optoelectronic industries continues to drive innovation in chemical mechanical polishing (CMP) technology. Achieving ultra-high precision surface finishing relies not only on advanced equipment and basic materials, but more importantly on the precise design and large-scale preparation of high-efficiency abrasive particles, as well as the scientific formulation of the corresponding polishing slurry. As the requirements for surface smoothness and processing efficiency become increasingly stringent, the demand for high-performance polishing materials is further increasing. In the manufacture of microelectronic devices and precision optical components, cerium oxide has become a key material for surface finishing.

[0003] Cerium oxide excels in polishing applications due to its unique physicochemical properties: it exhibits both strong chemical reactivity and excellent mechanical grinding performance. During polishing, cerium oxide particles react chemically with silica to form a softened surface layer that is easily removed. This layer is then effectively removed mechanically, achieving global planarization of the substrate surface. Furthermore, due to its specific crystal structure and physicochemical characteristics, cerium oxide can achieve high material removal rates and significantly suppress the formation of surface defects, improving polishing efficiency while ensuring processing quality.

[0004] However, in the conventional calcination preparation process, the content of trivalent cerium in the crystal lattice of traditional cerium oxide materials is relatively low, which makes it difficult to meet the requirements of high-efficiency and high-quality polishing, resulting in problems such as insufficient polishing rate and increased surface scratches.

[0005] Therefore, it is necessary to effectively increase the content of trivalent cerium in cerium oxide to enhance its chemical activity and polishing performance. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the problems of insufficient trivalent cerium content in cerium oxide abrasive grains in existing technologies, which leads to low chemical activity, low polishing rate, and increased surface scratches, this invention provides a boron-doped cerium oxide for polishing fluid, its preparation method, and its application.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0010] In a first aspect, the present invention provides a boron-doped cerium oxide for use in a polishing slurry, wherein the molar ratio of boron to cerium in the boron-doped cerium oxide is 1:1 to 1:10.

[0011] The boron-doped cerium oxide is prepared by co-precipitation reaction of cerium salt and boron source to generate a precursor, followed by calcination of the precursor.

[0012] Secondly, the present invention provides a method for preparing the above-mentioned boron-doped cerium oxide, comprising the following steps:

[0013] S1: Provides soluble cerium salt solution and soluble boron source solution;

[0014] S2: Mix a soluble cerium salt solution with a soluble boron source solution, then add an alkaline solution, and the precursor is obtained after the reaction.

[0015] S3: The precursor is calcined to obtain boron-doped cerium oxide.

[0016] In the preparation method described above, preferably, in step S1, the cerium salt is cerium nitrate, cerium chloride and their hydrates, and the boron source is one or more of boric acid, boron oxide and borate.

[0017] In the preparation method described above, preferably, in step S1, the molar ratio of boron source to cerium salt is (1-10):10.

[0018] In the preparation method described above, preferably, in step S2, the alkaline solution is ammonia.

[0019] In the preparation method described above, preferably, in step S2, after adding the alkali solution, the system is heated to 30-110°C and reacted for 12-16 hours under stirring conditions, with a stirring rate of 800-1000 r / min.

[0020] In the preparation method described above, preferably, in step S3, the calcination atmosphere is air, the calcination temperature is 500-600℃, and the calcination time is 2-4h.

[0021] Thirdly, the present invention provides a polishing liquid comprising water and the boron-doped cerium oxide described above or prepared by the above preparation method;

[0022] The mass percentage of boron-doped cerium oxide in the polishing slurry is 5-9%.

[0023] Fourthly, the present invention also provides an application of the above-mentioned polishing slurry in the chemical mechanical polishing of silica.

[0024] (III) Beneficial Effects

[0025] This invention effectively solves the problems of low chemical activity and poor polishing performance caused by insufficient trivalent cerium content in traditional cerium oxide by introducing boron into the cerium oxide lattice. After boron doping, the oxygen coordination environment in the cerium oxide lattice changes, with some oxygen atoms changing from tetracoordinated with tetravalent cerium to tricoordinated with trivalent boron. This structural change induces more oxygen vacancies, thereby significantly increasing the proportion of trivalent cerium in the material. The increased trivalent cerium content directly enhances the redox ability and surface reactivity of cerium oxide, making its chemical reaction with the silicon dioxide substrate more efficient during chemical mechanical polishing, thus improving the material removal rate and contributing to better surface quality. Attached Figure Description

[0026] Figure 1 is the XPS curve of boron-doped cerium oxide prepared in Example 1;

[0027] Figure 2 shows the X-ray diffraction patterns of cerium oxide prepared in Examples 1, 2, 4 and Comparative Example 1;

[0028] Figure 3 is a transmission electron microscope image of cerium oxide in the polishing solution prepared in Example 1, Example 2 and Comparative Example 1;

[0029] Figure 4 is an EDS image of boron-doped cerium oxide prepared in Example 1. Detailed Implementation

[0030] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] This invention provides a boron-doped cerium oxide for use in polishing slurries, wherein the molar ratio of boron to cerium in the cerium oxide is 1:1 to 1:10. The boron-doped cerium oxide of this invention is prepared by co-precipitation reaction of cerium salt and boron source to generate a precursor, followed by calcination of the precursor.

[0032] In traditional cerium oxide, cerium mainly exists in the tetravalent form, and its polishing activity primarily stems from the limited amount of Ce. 3+ / Ce 4+Redox pairs. This invention induces a significant change in the cerium oxide lattice structure through boron doping. Because boron's ionic radius and coordination characteristics differ from cerium's, its entry into the cerium oxide lattice alters the local oxygen coordination environment. Specifically, some oxygen atoms that were originally tetravalently coordinated with tetravalent cerium transform into trivalently coordinated oxygen atoms. This coordination change introduces structural perturbations into the lattice, spontaneously generating more oxygen vacancies to maintain electroneutrality. The generation of oxygen vacancies directly promotes the reduction of some tetravalent cerium to trivalent cerium, thus significantly increasing the relative content of trivalent cerium in the material. This increased trivalent cerium content greatly enhances the redox ability and surface chemical activity of cerium oxide. When applied to the chemical mechanical polishing of silica, the more reactive trivalent cerium can react more effectively with the silica surface to generate a Ce-O-Si softening layer that is easy to remove mechanically. This not only significantly improves the material removal rate, but also reduces the reliance on pure mechanical grinding due to the enhanced dominance of the chemical reaction. This helps to reduce defects such as surface scratches and obtain a higher quality polished surface.

[0033] The present invention also provides a method for preparing the above-mentioned boron-doped cerium oxide, comprising the following steps:

[0034] S1: Provides soluble cerium salt solution and soluble boron source solution.

[0035] S2: Mix a soluble cerium salt solution with a soluble boron source solution, then add an alkaline solution, and the precursor is obtained after the reaction.

[0036] S3: The precursor is calcined to obtain boron-doped cerium oxide.

[0037] The preparation method of the present invention is simple to operate, can ensure the uniformity of the particle size of the modified cerium oxide abrasive, and has a low cost, which is conducive to its widespread application.

[0038] Preferably, in step S1 above, the cerium salt can be cerium nitrate, cerium chloride and their hydrates, such as cerium nitrate hexahydrate, and the boron source can be one or more of boric acid, boron oxide, and borate, such as triethyl borate, trimethyl borate, boric acid, boron anhydride, and boron tribromide.

[0039] Organic or inorganic boric acids are chosen for doping cerium oxide because, firstly, the selected boron sources can achieve effective doping of cerium oxide under relatively mild conditions. Secondly, these boron sources have a higher success rate in doping cerium oxide and are more easily and uniformly distributed within the cerium oxide lattice, thus ensuring the doping effect. Furthermore, among the many boron sources mentioned above, boric acid, due to its small molecular structure, good water solubility, and suitable thermal stability, can diffuse and dope into the structure of the cerium oxide precursor more uniformly and effectively, thereby achieving the optimal doping effect and the highest trivalent cerium enhancement ratio. Therefore, boric acid is the preferred boron source.

[0040] More preferably, in step S1, the molar ratio of boron source to cerium salt is (1-10):10. Within this range, boron can be fully doped into the crystal lattice, maximizing the content of trivalent cerium. If the boron content is too low, the modification effect is limited; if it is too high, it may destroy the main crystal structure of cerium oxide, which is detrimental to performance improvement.

[0041] Preferably, in step S2 above, the soluble cerium salt solution prepared in step S1 is thoroughly mixed with the soluble boron source solution. Then, an alkaline solution is added to the mixed solution to initiate a co-precipitation reaction. Preferably, the alkaline solution is ammonia water, which provides a uniform alkaline environment, promoting the formation of a uniform co-precipitate between cerium ions and hydroxide ions. After adding the alkaline solution, the temperature of the reaction system is maintained between 30-110°C, preferably 60°C. At this temperature, the reaction is carried out with stirring at a rate of 800-1000 r / min for 12-16 h, followed by overnight aging.

[0042] Specifically, the solution preparation is as follows: Cerium salt is dissolved and dispersed in triethylene glycol, and then heated and stirred in an oil bath. Boron source is dispersed and dissolved in deionized water, and then heated and stirred in an oil bath. Ammonia solution is dispersed and dissolved in deionized water, and then heated and stirred in an oil bath. The ammonia solution can be heated under reflux in a reflux condenser, such as a round-bottom flask and condenser combination, to effectively suppress ammonia volatilization at high temperatures. After thorough mixing and heating, the boron and cerium sources are vigorously stirred with a magnetic stirrer until uniformly mixed, and then heated ammonia solution is added dropwise.

[0043] The aforementioned stirring rate ensures thorough and uniform mixing of the reactants, preventing localized agglomeration due to excessively high concentrations, and promotes uniformity in the nucleation and growth processes, resulting in precursors with a concentrated particle size distribution. Sufficient reaction time ensures complete precipitation and thorough maturation of the precursor particles, making their structure more stable and facilitating the formation of a regular doped lattice during subsequent calcination. During the doping of cerium oxide and boron source, simultaneous stirring and heating are necessary, while maintaining the stirring rate within a reasonable range. Since the solubility of cerium source in triethylene glycol is limited, and the boron source itself is relatively stable and does not readily react rapidly, continuous stirring during heating increases particle motion, thereby improving the mixing and contact rate between the boron source and cerium species, and consequently enhancing the reaction rate and doping uniformity. The stirring rate needs to be moderate, neither too fast nor too slow. Excessive stirring can generate strong eddies and intensify particle collisions, potentially leading to irregular precursor particle morphology or hard agglomeration, thus reducing product quality. Conversely, excessively slow stirring results in insufficient material mixing and a reduced reaction rate, similarly affecting the quality and performance consistency of the final product.

[0044] Preferably, in step S3 above, the obtained precursor is centrifuged, washed, and dried, wherein the centrifugation speed is ≥11000 r / min. It is then transferred to a muffle furnace and calcined in air at a temperature of 500-600℃ for 2-4 hours. In this invention, when the centrifugation speed is below 11000 r / min, incomplete centrifugation occurs, further hindering the dispersion of the modified cerium oxide powder in the subsequent polishing solution preparation step. During calcination, the precursor completely decomposes and crystallizes to form cerium oxide, while boron is stably dissolved into the cerium oxide lattice, completing the doping process. After calcination, boron-doped cerium oxide powder can be obtained by grinding.

[0045] The invention also provides a polishing slurry comprising water and boron-doped cerium oxide. In the polishing slurry, boron-doped cerium oxide serves as the abrasive particles, with a mass percentage of 5-9%. This concentration range is limited based on a comprehensive consideration of dispersion stability and polishing performance. When the content of boron-doped cerium oxide is within this range, the polishing slurry system has a suitable particle concentration. If the content is below 5%, although the dispersion stability is good, there are insufficient effective abrasive particles, and the material removal rate may not meet the process requirements. If the content of boron-doped cerium oxide in the polishing slurry is higher than 9%, the intermolecular forces between particles will increase, making agglomeration and sedimentation more likely, resulting in poor suspension stability of the polishing slurry, and the presence of agglomerates may cause scratches on the polished surface.

[0046] The polishing slurry described in this invention is particularly suitable for chemical mechanical polishing of silicon dioxide substrates or devices. Based on the enhanced chemical reactivity of boron-doped cerium oxide, this polishing slurry achieves a combination of high material removal rate and low surface roughness when polishing SiO2, making it especially suitable for the manufacturing processes of microelectronic devices and precision optical components with extremely high surface quality requirements, demonstrating promising application prospects.

[0047] To further clarify the present invention and its technological advancements, the following description is provided in conjunction with specific embodiments and technical effects.

[0048] Example 1

[0049] This embodiment provides a method for preparing boron-doped cerium oxide, comprising the following steps:

[0050] S1: Cerium nitrate hexahydrate was dissolved and dispersed in triethylene glycol with a stirring rate of 800 r / min. The system was heated to 60 °C in an oil bath for 2 h while maintaining the stirring rate, to obtain a cerium salt solution. Boric acid was dispersed and dissolved in deionized water with a stirring rate of 800 r / min. The system was heated to 60 °C in an oil bath for 2 h while maintaining the stirring rate, to obtain a boric acid solution. Ammonia was dispersed and dissolved in deionized water, placed in a round-bottom flask, and then combined with a condenser. The flask was heated to 60 °C in an oil bath and refluxed for 2 h to obtain ammonia. In this step, the molar ratio of boron to cerium was 1:10.

[0051] S2: At a stirring rate of 800 r / min, the boric acid solution and cerium salt solution, after being thoroughly stirred and heated, were vigorously stirred on a magnetic stirrer for 30 min. After mixing thoroughly, heated ammonia water was added dropwise. After all the water was added, the mixture was stirred continuously at the same rate and reacted for 12 h to obtain the precursor.

[0052] S3: The obtained precursor was centrifuged, washed, and dried at a speed of 11000 r / min. It was then transferred to a muffle furnace for calcination to obtain boron-doped cerium oxide at 550℃ for 3 hours. After calcination, the boron-doped cerium oxide was ground to obtain boron-doped cerium oxide abrasive particles.

[0053] Weigh boron-doped cerium oxide abrasive grains, add a little water to make a slurry, then continue to add water, and after magnetic stirring, let it stand for 4 hours to obtain a polishing liquid with an abrasive grain ratio of 5%.

[0054] Example 2

[0055] This embodiment provides a method for preparing boron-doped cerium oxide, comprising the following steps:

[0056] S1: Cerium nitrate was dissolved and dispersed in triethylene glycol with a stirring rate of 1000 r / min. The system was heated to 110 °C in an oil bath for 2 h while maintaining the stirring rate, to obtain a cerium salt solution. Boric acid was dispersed and dissolved in deionized water with a stirring rate of 1000 r / min. The system was heated to 110 °C in an oil bath for 2 h while maintaining the stirring rate, to obtain a boric acid solution. Ammonia was dispersed and dissolved in deionized water, placed in a round-bottom flask, and then combined with a condenser. The flask was heated to 40 °C in an oil bath and refluxed for 2 h to obtain ammonia. In this step, the molar ratio of boron to cerium was 5:10.

[0057] S2: At a stirring rate of 1000 r / min, the boric acid solution and cerium salt solution, after being thoroughly stirred and heated, were vigorously stirred on a magnetic stirrer for 30 min. After mixing thoroughly, heated ammonia water was added dropwise. After all the water was added, the stirring was maintained continuously, and the reaction was allowed to proceed for 16 h to obtain the precursor.

[0058] S3: The obtained precursor was centrifuged, washed, and dried at a speed of 12000 r / min. It was then transferred to a muffle furnace for calcination to obtain boron-doped cerium oxide at 500℃ for 4 h. After calcination, the boron-doped cerium oxide was ground to obtain boron-doped cerium oxide abrasive grains.

[0059] Weigh boron-doped cerium oxide abrasive grains, add a little water to make a slurry, then continue to add water, and after magnetic stirring, let it stand for 4 hours to obtain a polishing slurry with an abrasive grain content of 9%.

[0060] Example 3

[0061] This embodiment provides a method for preparing boron-doped cerium oxide, comprising the following steps:

[0062] S1: Cerium chloride was dissolved and dispersed in triethylene glycol with a stirring rate of 900 r / min. The system was heated to 30 °C in an oil bath for 2 h while maintaining the stirring rate, to obtain a cerium salt solution. Boric acid was dispersed and dissolved in deionized water with a stirring rate of 900 r / min. The system was heated to 30 °C in an oil bath for 2 h while maintaining the stirring rate, to obtain a boric acid solution. Ammonia was dispersed and dissolved in deionized water, placed in a round-bottom flask, and then combined with a condenser. The flask was heated to 30 °C in an oil bath and refluxed for 2 h to obtain ammonia. In this step, the molar ratio of boron to cerium was 10:10.

[0063] S2: At a stirring rate of 900 r / min, the boric acid solution and cerium salt solution, after being thoroughly stirred and heated, were vigorously stirred on a magnetic stirrer for 30 min. After mixing thoroughly, heated ammonia water was added dropwise. After all the water was added, the mixture was stirred continuously at the same rate and reacted for 14 h to obtain the precursor.

[0064] S3: The obtained precursor was centrifuged, washed, and dried at a speed of 11000 r / min. It was then transferred to a muffle furnace for calcination to obtain boron-doped cerium oxide at 600℃ for 2 hours. After calcination, the boron-doped cerium oxide was ground to obtain boron-doped cerium oxide abrasive particles.

[0065] Weigh boron-doped cerium oxide abrasive grains, add a little water to make a slurry, then continue to add water, and after magnetic stirring, let it stand for 4 hours to obtain a polishing liquid with an abrasive grain ratio of 6%.

[0066] Example 4

[0067] This embodiment provides a method for preparing boron-doped cerium oxide, which differs from Embodiment 1 in that the molar ratio of boron to cerium is 2:10.

[0068] Example 5

[0069] This embodiment provides a method for preparing boron-doped cerium oxide, which differs from Example 1 in that the boron source is triethyl borate.

[0070] Example 6

[0071] This embodiment provides a method for preparing boron-doped cerium oxide, which differs from Example 1 in that the boron source is trimethyl borate.

[0072] Example 7

[0073] A method for preparing boron-doped cerium oxide differs from Example 1 in that the boron source is boron anhydride.

[0074] Example 8

[0075] A method for preparing boron-doped cerium oxide differs from Example 1 in that the boron source is boron tribromide.

[0076] Comparative Example 1

[0077] This comparative example provides a method for preparing boron-doped cerium oxide, which differs from Example 1 in that no boron source is added.

[0078] Comparative Example 2

[0079] This comparative example provides a method for preparing boron-doped cerium oxide, which differs from Example 1 in that the molar ratio of boron to cerium is 1:20.

[0080] Comparative Example 3

[0081] This comparative example provides a method for preparing boron-doped cerium oxide, which differs from Example 1 in that the molar ratio of boron to cerium is 20:10.

[0082] To verify the excellent performance of the boron-doped cerium oxide and its polishing solution prepared in this invention, a series of structural characterization and polishing performance tests were performed on the samples prepared in Examples 1-8 and Comparative Examples 1-3.

[0083] 1. X-ray photoelectron spectroscopy (XPS) test

[0084] XPS analysis was used to determine the Ce content in the cerium oxides prepared in Examples 1-8 and Comparative Examples 1-3. 3+ relative content (Ce) 3+ / (Ce 3+ +Ce 4+ The results are shown in Table 1. Figure 1 is the XPS curve of boron-doped cerium oxide prepared in Example 1.

[0085] Table 1. Ce in cerium oxide prepared in Examples 1-8 and Comparative Examples 1-3 3+ Relative content statistics table

[0086]

[0087] As shown in Table 1, in Examples 1-8, the content of trivalent cerium in boron-doped cerium oxide was significantly higher than that in undoped Comparative Example 1, Comparative Example 2 with too low boron content, and Comparative Example 3 with too high boron content. This proves that boron doping successfully induced the generation of oxygen vacancies, promoted the conversion of tetravalent cerium to trivalent cerium, and the maximum increase in trivalent cerium content and the best polishing performance could only be achieved when the molar ratio of boron to cerium was in the range of 1-10:10.

[0088] Furthermore, under the same feed ratio, boric acid yields a higher content of trivalent cerium. This may be because, compared to boron sources such as triethyl borate, trimethyl borate, boron anhydride, and boron tribromide, boric acid, due to its small molecular size, good water solubility, and moderate thermal stability, can bind more uniformly with the precursor during co-precipitation, thereby achieving more efficient and uniform lattice doping after calcination. Other boron sources may have relatively weaker doping effects due to poor solubility or excessively large lattice structures.

[0089] 2. X-ray diffraction (XRD) analysis

[0090] XRD tests were performed on the cerium oxide prepared in Examples 1, 2, 4, and Comparative Example 1, resulting in Figure 2. Figure 2 shows that all samples exhibited typical fluorite-structured cerium oxide diffraction peaks, with no other impurity phase peaks appearing, indicating that boron doping did not alter the main crystal phase of cerium oxide. Furthermore, the cerium oxide prepared in Examples 3 and 5-8 also showed typical fluorite-structured cerium oxide diffraction peaks.

[0091] 3. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) analysis

[0092] Figure 3, from left to right, shows transmission electron microscope images of cerium oxide in the polishing solutions prepared in Example 1, Example 2, and Comparative Example 1, with the lower image being a magnified view of a portion of the upper image.

[0093] As shown in Figure 3, the boron-doped cerium oxide particles prepared in Examples 1 and 2 exhibit a nanoscale and uniformly distributed morphology with an average particle size of less than 50 nm, good dispersibility, and no obvious hard agglomeration. This structure is beneficial for stable dispersion in the polishing slurry and provides uniform and gentle mechanical action during chemical mechanical polishing, thereby obtaining a polished surface with low roughness and low defects while efficiently removing material. In contrast, Comparative Example 1 showed obvious agglomeration, and the particle size of the cerium oxide particles was significantly higher than 100 nm.

[0094] In addition, the particle size and state of cerium oxide in the polishing liquids prepared in Examples 3-8 were detected. The results showed that the boron-doped cerium oxide particles prepared in Examples 3-8 also exhibited a nanoscale and uniformly distributed morphology, with an average particle size of less than 50 nm, good dispersibility, and no obvious hard agglomeration.

[0095] EDS surface scanning and elemental distribution mapping analysis were performed on the boron-doped cerium oxide prepared in Example 1, as shown in Figure 4. Figure 4 shows that the signals of cerium (Ce), oxygen (O), and boron (B) are uniformly distributed and highly overlapping throughout the observation area, with no boron segregation or enrichment regions observed. This result directly confirms that boron has been successfully and uniformly incorporated into the bulk lattice of the cerium oxide particles, forming a uniform solid solution structure, rather than being merely physically adsorbed on the particle surface or existing at grain boundaries. This uniform bulk doping is fundamental to achieving stable and efficient lattice modification and performance improvement.

[0096] Based on the EDS analysis of Example 1, the same EDS surface scan and elemental distribution mapping analysis were performed on the boron-doped cerium oxide samples prepared in Examples 2-8. The results showed that the EDS spectra of Examples 2-8 all exhibited similar characteristics to those of Example 1: the signals of cerium (Ce), oxygen (O), and boron (B) were uniformly distributed within the observation area, and the elemental distribution maps highly overlapped. No significant segregation or enrichment of boron was observed on the particle surface or at grain boundaries.

[0097] These results collectively confirm that, regardless of the specific boron source used, the co-precipitation-calcination preparation method provided by this invention can achieve effective and uniform doping of boron in the cerium oxide bulk lattice. Boron atoms successfully occupy specific positions in the lattice, forming a homogeneous solid solution, rather than a simple physical mixture or surface modification. This uniform bulk doping structure is the fundamental reason why all the sample examples achieve a consistently increased trivalent cerium content, and consequently exhibit excellent and consistent polishing performance.

[0098] 4. Polishing performance test

[0099] The polishing slurries prepared in Examples 1-8 and Comparative Examples 1-3 were used to conduct comparative polishing performance tests on silicon dioxide wafers under the same chemical mechanical polishing (CMP) process conditions. The material removal rate (MRR) and the surface roughness (Ra) after polishing were evaluated.

[0100] The MRR of the polishing slurries in all embodiments was significantly higher than that in Comparative Examples 1-2. Furthermore, within the range of boron to cerium molar ratios of 1:1 to 1:10, the material removal rate exhibited a trend consistent with the change in boron doping ratio and trivalent cerium content; higher trivalent cerium content resulted in higher material removal rates. This confirms that increasing the trivalent cerium content significantly enhances the chemical reactivity between cerium oxide and the silica surface, thereby improving material removal efficiency.

[0101] Furthermore, while achieving high removal rates, the polishing slurries in all embodiments also obtained superior surface quality. Within a boron to cerium molar ratio range of 1:1 to 1:10, the trend of surface roughness after polishing with varying boron doping ratios was consistent with the trend of trivalent cerium content; the higher the trivalent cerium content, the lower the surface roughness. The surface roughness of the wafers polished in Examples 1-8 was significantly lower than that in Comparative Examples 1-2. This indicates that the chemical action enhanced by boron doping dominated the material removal process, reducing reliance on pure mechanical grinding and effectively lowering the risk of surface scratches and other defects. For Comparative Example 3, although the trivalent cerium content in the prepared cerium oxide was relatively high, the excessively high boron doping content made the sample brittle, resulting in lower mechanical force, a lower polishing rate, and poorer polishing effect.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 boron-doped cerium oxide for use in polishing slurries, characterized in that, In the boron-doped cerium oxide, the molar ratio of boron to cerium in the cerium oxide is 1:1 to 1:10; the boron-doped cerium oxide is prepared by co-precipitation reaction of cerium salt and boron source to generate a precursor, and then calcining the precursor.

2. A method for preparing boron-doped cerium oxide according to claim 1, characterized in that, The process includes the following steps: S1: providing a soluble cerium salt solution and a soluble boron source solution; S2: mixing the soluble cerium salt solution and the soluble boron source solution, then adding an alkaline solution, and reacting to obtain the precursor; S3: The precursor is calcined to obtain boron-doped cerium oxide.

3. The preparation method according to claim 2, characterized in that, In step S1, the cerium salt is cerium nitrate, cerium chloride and their hydrates, and the boron source is one or more of boric acid, boron oxide and borate.

4. The preparation method according to claim 2, characterized in that, In step S1, the molar ratio of boron source to cerium salt is (1-10):

10.

5. The preparation method according to claim 2, characterized in that, In step S2, the alkaline solution is ammonia.

6. The preparation method according to claim 2, characterized in that, In step S2, after adding the alkali solution, the system is heated to 30-110℃ and reacted for 12-16 hours under stirring conditions at a stirring rate of 800-1000 r / min.

7. The preparation method according to claim 2, characterized in that, In step S3, the calcination atmosphere is air, the calcination temperature is 500-600℃, and the calcination time is 2-4h.

8. A polishing slurry comprising water and boron-doped cerium oxide as described in claim 1 or prepared by the method described in any one of claims 2-6; wherein the mass percentage of boron-doped cerium oxide in the polishing slurry is 5-9%.

9. The application of the polishing slurry according to claim 8 in the chemical mechanical polishing of silica.

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