Method for producing ceria nanoparticles for semiconductor CMP processes using room temperature liquid-phase precipitation method

Abstract

This invention relates to a method for producing ceria nanoparticles. [Solution] The present invention relates to a method for producing ceria nanoparticles, comprising the steps of (a) stirring a ceria precursor and distilled water to produce a first mixture, (b) adding a basic catalyst to the first mixture and stirring to obtain a precipitate, (c) washing the precipitate and then drying it, and (d) heat-treating the dried precipitate to produce ceria nanoparticles.

Description

Technical Field

[0001] The present invention relates to a method for producing ceria nanoparticles, and more particularly to a method for producing ceria nanoparticles comprising: (a) stirring a ceria precursor and distilled water to prepare a first mixture; (b) adding a basic catalyst to the first mixture and then stirring to obtain a precipitate; (c) washing the precipitate and then drying it; and (d) heat-treating the dried precipitate to produce ceria nanoparticles.

Background Art

[0002] Due to the high integration and high performance of semiconductor devices, the line width of wiring patterns is becoming finer and the structure is becoming more multilayered. Therefore, in order to improve the accuracy of photolithography, planarization between layers in each process is very important.

[0003] Currently, the most spotlighted planarization technology is the CMP (chemical-mechanical polishing) process. The CMP process is classified into an oxide CMP process, a metal CMP process, a polysilicon (poly-Si) CMP process, etc. according to the material to be polished.

[0004] In order to polish an oxide film, initially, a CMP slurry composition containing silica particles was mainly used. However, as the design rule becomes smaller and the device becomes thinner and requires high planarization, a CMP slurry composition containing cerium oxide (ceria) particles having a high polishing selectivity ratio for wafers having different types of films has been increasingly used.

[0005] On the other hand, the slurry composition containing ceria particles has a higher polishing rate than the slurry composition containing silica particles, but scratches occur on the polished surface.

[0006] Therefore, there is a need for technological development regarding polishing slurry compositions containing ceria nanoparticles that exhibit excellent thermal stability, dispersion stability, aging stability, polishing speed, polishing efficiency, and selective polishing properties, and that can minimize scratches on the polished surface.

[0007] [Related Issues] - Issue number: RS-2023-00281517 - Project ID: 1711199385 - French name: Department of Science, Technology and Information Communications - Research project name: National Semiconductor Research Laboratory Support Core Technology Development Project (R&D) - Research project title: Development of core technologies and classes for next-generation semiconductor materials and processes for CMP processes Training of personnel specializing in conductors - Research period: August 1, 2023 to December 31, 2027. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Korean Published Patent Publication No. 10-2013-0078791 [Patent Document 2] Korean Published Patent Publication No. 10-2024-0138745 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The present invention has been made to solve the aforementioned problems and aims to provide a method for producing ceria nanoparticles for polishing slurry compositions that are excellent in thermal stability, dispersion stability, aging stability, polishing speed, polishing efficiency, and selective polishing properties, and that can minimize scratches on the polished surface. [Means for solving the problem]

[0010] To achieve the above objective, the present invention provides a method for producing ceria nanoparticles, comprising the steps of (a) stirring a ceria precursor and distilled water to produce a first mixture, (b) adding a basic catalyst to the first mixture and stirring to obtain a precipitate, (c) washing the precipitate and then drying it, and (d) heat-treating the dried precipitate to produce ceria nanoparticles.

[0011] In one embodiment of the present invention, the ceria precursor is characterized by using at least one selected from cerium carbonate, cerium sulfate, cerium acetate, cerium nitrate, and cerium chloride.

[0012] In one embodiment of the present invention, the basic catalyst is characterized by using at least one selected from ammonia, sodium hydroxide, potassium hydroxide, and amine compounds.

[0013] In one embodiment of the present invention, step (c) is characterized by drying the precipitate at 50 to 200°C.

[0014] In one embodiment of the present invention, step (d) is characterized by heat-treating the dried precipitate at 400 to 800°C for 1 to 20 hours.

[0015] Furthermore, the present invention provides ceria nanoparticles produced by the above-described manufacturing method. [Effects of the Invention]

[0016] The present invention provides a method for producing ceria nanoparticles for polishing slurry compositions that are excellent in thermal stability, dispersion stability, aging stability, polishing speed, polishing efficiency, and selective polishing properties, and that can minimize scratches on the polished surface. [Brief explanation of the drawing]

[0017] [Figure 1] This figure shows the TGA and DTA results for cerium nitrate according to the present invention. [Figure 2] SEM image of the ceria nanoparticles of the present invention. [Figure 3] TEM image of the ceria nanoparticles of the present invention. [Figure 4] Diagram showing DLS and zeta potential of the slurry composition containing the ceria nanoparticles of the present invention. [Figure 5] Diagram showing the XRD results of the ceria nanoparticles of the present invention.

Mode for Carrying Out the Invention

[0018] Hereinafter, the present invention will be described in detail based on embodiments. Terms, examples, etc. used in the present invention are merely shown to explain the present invention more specifically and to assist the understanding of an ordinary technician, and the scope of rights of the present invention etc. are not limited thereto.

[0019] Technical terms and scientific terms used in the present invention are used in the meanings usually understood by those having ordinary knowledge in the technical field to which the present invention pertains, unless otherwise specified.

[0020] The present invention relates to a method for producing ceria nanoparticles, comprising: (a) a step of stirring a ceria precursor and distilled water to prepare a first mixture; (b) a step of adding a basic catalyst to the first mixture and then stirring to obtain a precipitate; (c) a step of washing the precipitate and then drying it; and (d) a step of heat-treating the dried precipitate to produce ceria nanoparticles.

[0021] The step (a) may be one of stirring a ceria precursor and distilled water to prepare a first mixture.

[0022] The ceria precursor may be at least one selected from cerium carbonate, cerium sulfate, cerium acetate, cerium nitrate, and cerium chloride.

[0023] The present invention may also use a mixture of cerium nitrate and cerium acetate as the ceria precursor.

[0024] Here, the weight ratio of cerium nitrate to cerium acetate is preferably 60-80:20-40, and when the weight ratio satisfies this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0025] Furthermore, the present invention may also use a mixture of cerium nitrate, cerium acetate, and cerium carbonate as the ceria precursor.

[0026] Here, the weight ratio of cerium nitrate, cerium acetate, and cerium carbonate is preferably 100:20 to 40:5 to 20, and when the weight ratio satisfies this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0027] Step (b) may involve adding a basic catalyst to the first mixture and then stirring to obtain a precipitate.

[0028] The basic catalyst may be at least one selected from ammonia, ammonia solution, sodium hydroxide, potassium hydroxide, and amine compounds.

[0029] Step (c) is a step of washing the precipitate with distilled water or the like, and then drying it, and the precipitate may be dried at 50 to 200°C for 1 to 50 hours.

[0030] Step (d) may involve heat-treating the dried precipitate to produce spherical ceria nanoparticles.

[0031] Here, the size (diameter) of the ceria nanoparticles is preferably 20 nm or less.

[0032] In this invention, it is preferable to heat-treat the dried precipitate in an air or oxygen atmosphere at 400 to 800°C for 1 to 20 hours, and when the heat treatment conditions meet this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0033] Furthermore, step (d) may include a primary heat treatment step of heating the dried precipitate to produce a primary product, a secondary heat treatment step of heating the primary product to produce a secondary product, a tertiary heat treatment step of heating the secondary product to produce a tertiary product, and a quaternary heat treatment step of heating the tertiary product to produce a quaternary product.

[0034] By performing the aforementioned heat treatment step in multiple stages, the size, distribution, shape, density, and crystallinity of the produced ceria particles become uniform, thereby improving dispersibility, polishing speed, and polishing efficiency.

[0035] The aforementioned primary heat treatment step may involve heat treatment at 400-500°C for 1-5 hours to produce the primary product.

[0036] When the heat treatment conditions meet this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0037] The secondary heat treatment step may involve heat treatment at 510-600°C for 1-5 hours to produce the secondary product.

[0038] When the heat treatment conditions meet this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0039] The aforementioned tertiary heat treatment step may involve heat treatment at 610-700°C for 1-5 hours to produce the tertiary product.

[0040] When the heat treatment conditions meet this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0041] The aforementioned quaternary heat treatment step may involve heat treatment at 710-800°C for 1-5 hours to produce the quaternary product.

[0042] When the heat treatment conditions meet this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0043] Furthermore, the present invention may further include the step of pulverizing the ceria nanoparticles.

[0044] This may involve grinding ceria nanoparticles in at least one selected from a ball mill, rod mill, pebble mill, barstone mill, and pulverizer.

[0045] Furthermore, the present invention relates to ceria nanoparticles produced by the above-described manufacturing method.

[0046] The aforementioned ceria nanoparticles exhibit excellent thermal stability, dispersion stability, aging stability, polishing speed, polishing efficiency, and selective polishing properties, and can minimize scratches on the polished surface, making them suitable for use in polishing slurry compositions.

[0047] Furthermore, the ceria nanoparticles may be surface-treated with a copolymer of an acrylate group-containing silane coupling agent, 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl methacrylate (HEMA), and glycidyl methacrylate.

[0048] By using the surface-treated ceria nanoparticles described above, dispersibility, polishing speed, and polishing efficiency are improved.

[0049] Examples of the acrylate group-containing silane coupling agent include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, methacryloxymethyltriethoxysilane, and methacryloxymethyltrimethoxysilane.

[0050] The weight ratio of the acrylate group-containing silane coupling agent, 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl methacrylate (HEMA), and glycidyl methacrylate is preferably 2-10:100:20-50:10-30.

[0051] The copolymer content is preferably 1 to 10 parts by weight per 100 parts by weight of ceria nanoparticles. When the content meets this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0052] Furthermore, the ceria nanoparticles may be surface-treated with an acrylic mixture containing methyl methacrylate, acrylic acid, and 2-hydroxyethyl acrylate (HEA).

[0053] By using the surface-treated ceria nanoparticles described above, dispersibility, polishing speed, and polishing efficiency are improved.

[0054] The weight ratio of methyl methacrylate, acrylic acid, and 2-hydroxyethyl acrylate (HEA) is preferably 100:20 to 50:10 to 30.

[0055] The content of the acrylic mixture is preferably 1 to 10 parts by weight per 100 parts by weight of ceria nanoparticles. When the content is within this range, the dispersibility, polishing speed, and polishing efficiency are maximized.

[0056] Furthermore, the ceria nanoparticles may be surface-treated with a silane compound.

[0057] As the silane compound, any alkoxysilane such as tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS), sodium silicate, potassium silicate, silicon tetrachloride, etc. may be used.

[0058] The content of the silane compound is preferably 1 to 10 parts by weight per 100 parts by weight of ceria nanoparticles. When the content is within this range, the dispersibility, polishing speed, and polishing efficiency are maximized.

[0059] In this invention, a mixture of tetramethoxysilane and tetraethoxysilane may be used as the silane compound.

[0060] Here, the weight ratio of tetramethoxysilane to tetraethoxysilane is preferably 60-80:20-40, and when the weight ratio satisfies this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0061] Furthermore, the ceria nanoparticles may be surface-treated with a composition prepared by mixing the acrylic mixture and the silane compound.

[0062] Here, the weight ratio of the acrylic mixture to the silane compound is preferably 60-80:20-40, and when the weight ratio satisfies this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0063] The content of the aforementioned composition is preferably 1 to 10 parts by weight per 100 parts by weight of ceria nanoparticles. When the content satisfies this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0064] The present invention will be described in detail below with reference to examples and comparative examples. These examples are merely illustrative of the present invention, and the present invention is not limited to these examples. [Examples]

[0065] A first mixture was prepared by stirring cerium nitrate and distilled water.

[0066] A 10% ammonia solution was added to the first mixture, and the mixture was then stirred to obtain a precipitate.

[0067] The precipitate was filtered, washed with distilled water, and then dried at 110°C for 24 hours.

[0068] The dried precipitate was heat-treated at 500°C for 6 hours in an air atmosphere to produce ceria nanoparticles.

[0069] Figure 1 shows the TGA and DTA results for cerium nitrate according to the present invention.

[0070] The weight loss of cerium nitrate occurs in two stages. The first stage occurs at approximately 135°C, where the water absorbed by the cerium nitrate evaporates. The second stage occurs at 200-300°C, which is due to the separation of NO and NO2 from the cerium nitrate.

[0071] In differential thermal analysis, two exothermic peaks were observed. The first was generated by the evaporation of water absorbed by cerium nitrate, and the second, broader exothermic peak was a phenomenon caused by the separation of NO and NO2. Subsequently, crystallization occurred within the ceria particles, and it was confirmed that the separation of nitrate was almost complete at 400°C.

[0072] Figure 2 is an SEM image of the ceria nanoparticles of the present invention.

[0073] The ceria nanoparticles of the present invention were found to be spherical, and their particle size was confirmed to be 15-20 nm.

[0074] Figure 3 is a TEM image of the ceria nanoparticles of the present invention.

[0075] The ceria nanoparticles of the present invention were found to be spherical, and their particle size was confirmed to be 15-20 nm.

[0076] Figure 4 shows the DLS and zeta potential of the slurry composition containing ceria nanoparticles according to the present invention.

[0077] Milling tests to evaluate the applicability of ceria nanoparticles to slurries revealed that the particle size of the ceria slurry composition of the present invention was 810.5 nm (D50), which is smaller than the particle size of 1,744.1 nm of commonly used ceria slurry compositions.

[0078] Furthermore, the ceria slurry composition of the present invention exhibited a zeta potential comparable to that of commonly used ceria slurry compositions.

[0079] Figure 5 shows the XRD results of the ceria nanoparticles of the present invention.

[0080] The ceria nanoparticles of the present invention exhibit peaks on the (111), (200), (220), (331), and (222) planes, which are typical lattice structures of ceria, thus confirming the formation of a ceria crystal structure.

[0081] Furthermore, the surface area, pore volume, and pore size of ceria nanoparticles prepared using the room-temperature liquid-phase precipitation method of the present invention were analyzed.

[0082] The specific surface area of ​​ceria nanoparticles is 60.2 m². 2 The pore volume was 0.092 cc / g, the pore size was 6.14 nm, and the volume was 0.092 cc / g. [Examples]

[0083] Ceria nanoparticles were prepared in the same manner as in Example 1, except that they were heat-treated at 300°C. [Examples]

[0084] Ceria nanoparticles were prepared in the same manner as in Example 1, except that they were heat-treated at 900°C. [Examples]

[0085] Ceria nanoparticles were prepared in the same manner as in Example 1, except that a mixture of cerium nitrate and cerium acetate was used instead of cerium nitrate.

[0086] Here, the weight ratio of cerium nitrate to cerium acetate was adjusted to 70:30. [Examples]

[0087] Ceria nanoparticles were prepared in the same manner as in Example 1, except that instead of heat-treating the dried precipitate at 500°C for 6 hours, a primary heat treatment step was used in which the dried precipitate was heated at 450°C for 1.5 hours to produce a primary product; a secondary heat treatment step was used in which the primary product was heated at 550°C for 1.5 hours to produce a secondary product; a tertiary heat treatment step was used in which the secondary product was heated at 650°C for 1.5 hours to produce a tertiary product; and a quaternary heat treatment step was used in which the tertiary product was heated at 750°C for 1.5 hours to produce a quaternary product. [Examples]

[0088] An acrylic mixture was prepared by mixing methyl methacrylate, acrylic acid, and 2-hydroxyethyl acrylate (HEA).

[0089] Here, the weight ratio of methyl methacrylate, acrylic acid, and 2-hydroxyethyl acrylate (HEA) was adjusted to 100:30:20.

[0090] The ceria nanoparticles prepared in Example 1 were surface-treated with the acrylic mixture.

[0091] Here, the content of the acrylic mixture was adjusted to 5 parts by weight per 100 parts by weight of ceria nanoparticles.

[0092] (Comparative Example 1) Ceria nanoparticles were prepared by heat-treating cerium nitrate at 300°C for 6 hours in an air atmosphere.

[0093] (Item to be polished) As wafers, flat silicon oxide films and silicon nitride films were used.

[0094] (CMP process conditions) The polishing process conditions are shown in Table 1.

[0095] [Table 1]

[0096] (polishing speed) The thickness of the sample wafers before and after polishing was confirmed using ST-5030 (K-MAC Corp.). To prevent measurement errors, measurements were taken at 49 identical points along the X-axis from the center to the edge for each wafer, and the results were averaged (unit: Å / min).

[0097] (uniformity) After polishing, the uniformity of the wafer sample was measured.

[0098] (Presence or absence of scratches) After polishing, the substrate was cleaned, and then examined for defects and scratches using an optical microscope, with the results categorized as excellent, good, average, and poor.

[0099] The properties of the polishing slurry compositions containing ceria nanoparticles prepared in the examples and comparative examples described above were evaluated. The results are shown in Table 2.

[0100] [Table 2]

[0101] The results in Table 2 show that Examples 1-6 exhibit excellent selective polishing characteristics, as they have a high polishing rate for silicon oxide films and a low polishing rate for silicon nitride films.

[0102] In other words, the compositions of Examples 1 to 6 are judged to have excellent stopping layer formation function for silicon nitride films.

[0103] Furthermore, it can be seen that Examples 1 to 6 exhibit excellent uniformity and scratch-generating characteristics.

[0104] Examples 1, 4-6, in particular, exhibit the most excellent characteristics.

[0105] In contrast, Comparative Example 1 is found to be inferior to the example in terms of the aforementioned characteristics.

Claims

1. (a) A step of stirring the ceria precursor and distilled water to prepare a first mixture, (b) Adding a basic catalyst to the first mixture, and then stirring to obtain a precipitate, (c) The step of washing the precipitate and then drying it, A method for producing ceria nanoparticles, comprising the step of (d) heat-treating the dried precipitate to produce ceria nanoparticles.

2. The method for producing ceria nanoparticles according to claim 1, characterized in that the ceria precursor is at least one selected from cerium carbonate, cerium sulfate, cerium acetate, cerium nitrate, and cerium chloride.

3. The method for producing ceria nanoparticles according to claim 2, characterized in that the basic catalyst is at least one selected from ammonia, sodium hydroxide, potassium hydroxide, and amine compounds.

4. The method for producing ceria nanoparticles according to claim 3, characterized in that step (c) is drying the precipitate at 50 to 200°C.

5. The method for producing ceria nanoparticles according to claim 4, characterized in that step (d) is heat-treated at 400 to 800°C for 1 to 20 hours.

6. Ceria nanoparticles produced by the manufacturing method described in claim 1.

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