Method for producing ceria nanoparticles for semiconductor CMP processes using a solid-phase 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) preparing a ceria precursor, (b) heat-treating the ceria precursor to produce rod-shaped ceria nanoparticles, and (c) pulverizing the 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) a step of preparing a ceria precursor; (b) a step of heat-treating the ceria precursor to produce rod-shaped ceria nanoparticles; and (c) a step of pulverizing the ceria nanoparticles.

Background Art

[0002] Due to the higher integration and performance of semiconductor devices, the line width of wiring patterns tends to become finer and the structure tends to become 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 technique 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. depending on 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 element 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 films has come to be used.

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

[0006] Therefore, there is a need for technological development regarding a polishing slurry composition containing ceria nanoparticles, which is excellent in thermal stability, dispersion stability, stability over time, polishing rate, polishing efficiency, and selective polishing characteristics, and 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) preparing a ceria precursor, (b) heat-treating the ceria precursor to produce rod-shaped ceria nanoparticles, and (c) pulverizing the ceria nanoparticles.

[0011] In one embodiment of the present invention, the step (a) is characterized by pulverizing and stirring a ceria precursor.

[0012] In one embodiment of the present invention, at least one selected from cerium carbonate, cerium sulfate, cerium acetate, cerium nitrate, and cerium chloride is used as the ceria precursor.

[0013] In one embodiment of the present invention, the step (b) is characterized by heat-treating the ceria precursor at 400 to 800 °C for 1 to 20 hours.

[0014] In one embodiment of the present invention, the step (c) is characterized by pulverizing the ceria nanoparticles with at least one selected from a ball mill, a rod mill, a pebble mill, a burst stone mill, and a crusher.

[0015] Further, the present invention provides ceria nanoparticles produced by the above production method.

Effects of the Invention

[0016] The present invention can provide a method for producing ceria nanoparticles for a polishing slurry composition, which is excellent in thermal stability, dispersion stability, stability over time, polishing rate, polishing efficiency, and selective polishing characteristics, and can minimize scratches on the polished surface.

Brief Description of the Drawings

[0017] [Figure 1] It is a diagram showing the TGA and DTA results of cerium carbonate of the present invention. [Figure 2] It is a SEM image of the ceria nanoparticles of the present invention. [Figure 3] It is a TEM image of the ceria nanoparticles of the present invention. [Figure 4] It is a diagram showing the DLS and zeta potential of a slurry composition containing the ceria nanoparticles of the present invention. [Figure 5] It is a diagram showing the XRD results of the ceria nanoparticles of the present invention.

Best Mode for Carrying Out the Invention

[0018] Hereinafter, the present invention will be described in detail based on embodiments. The terms, examples, etc. used in the present invention are only for more specifically explaining the present invention and assisting the understanding of ordinary technicians, and the scope of rights of the present invention is 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 preparing a ceria precursor; (b) a step of heat-treating the ceria precursor to produce rod-shaped ceria nanoparticles; and (c) a step of pulverizing the ceria nanoparticles.

[0021] The step (a) is a step of preparing a ceria precursor, and the ceria precursor may be pulverized and mixed to produce ceria precursor particles of uniform size.

[0022] The ceria precursor undergoes a reaction in the calcination step by heat treatment and is converted into ceria nanoparticles. Here, when the ceria precursor particles aggregate, the reaction with oxygen during the calcination step occurs not in the whole of the ceria precursor but only in a part of the ceria precursor.

[0023] Then, the size, distribution, shape, density, and crystallinity of the produced ceria particles become non-uniform, so that the dispersibility, polishing rate, polishing efficiency, etc. decrease.

[0024] In this invention, by crushing and mixing the ceria precursor and using ceria precursor particles of uniform size, aggregation of the ceria precursor particles is minimized, and the reaction with oxygen occurs uniformly throughout the ceria precursor during the calcination process. As a result, the size, distribution, shape, density, and crystallinity of the produced ceria particles become uniform, improving dispersibility, polishing speed, and polishing efficiency.

[0025] The ceria precursor may be at least one selected from cerium carbonate, cerium sulfate, cerium acetate, cerium nitrate, and cerium chloride.

[0026] In this invention, a mixture of cerium carbonate and cerium acetate may be used as the ceria precursor.

[0027] Here, the weight ratio of cerium carbonate 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.

[0028] Furthermore, the present invention may also use a mixture of cerium carbonate, cerium acetate, and cerium nitrate as the ceria precursor.

[0029] Here, the weight ratio of cerium carbonate, cerium acetate, and cerium nitrate 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.

[0030] Step (b) may involve heat-treating the ceria precursor to produce rod-shaped ceria nanoparticles.

[0031] In the present invention, it is preferable to heat-treat the ceria precursor in an air or oxygen atmosphere at 400 to 800°C for 1 to 20 hours. When the heat treatment conditions meet this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0032] Furthermore, step (b) may include a primary heat treatment step of heating the ceria precursor 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.

[0033] 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.

[0034] The aforementioned primary heat treatment step may involve heat treatment at 400-500°C for 1-5 hours to produce the primary product.

[0035] When the heat treatment conditions meet this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0036] The secondary heat treatment step may involve heat treatment at 510-600°C for 1-5 hours to produce the secondary product.

[0037] When the heat treatment conditions meet this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0038] The aforementioned tertiary heat treatment step may involve heat treatment at 610-700°C for 1-5 hours to produce the tertiary product.

[0039] When the heat treatment conditions meet this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0040] The aforementioned quaternary heat treatment step may involve heat treatment at 710-800°C for 1-5 hours to produce the quaternary product.

[0041] When the heat treatment conditions meet this numerical range, dispersibility, polishing speed, and polishing efficiency are maximized.

[0042] Step (c) is a step of grinding the ceria nanoparticles, which may be done by grinding the ceria nanoparticles in at least one selected from a ball mill, rod mill, pebble mill, barstone mill and pulverizer.

[0043] The size (diameter) of the pulverized ceria nanoparticles is preferably 10 to 200 nm, and the length is preferably 50 to 700 nm.

[0044] Furthermore, the present invention relates to ceria nanoparticles produced by the above-described manufacturing method.

[0045] 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.

[0046] 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.

[0047] By using the surface-treated ceria nanoparticles described above, dispersibility, polishing speed, and polishing efficiency are improved.

[0048] Examples of the acrylate group-containing silane coupling agent include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, methacryloxymethyltriethoxysilane, and methacryloxymethyltrimethoxysilane.

[0049] 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.

[0050] 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.

[0051] Furthermore, the ceria nanoparticles may be surface-treated with an acrylic mixture containing methyl methacrylate, acrylic acid, and 2-hydroxyethyl acrylate (HEA).

[0052] By using the surface-treated ceria nanoparticles described above, dispersibility, polishing speed, and polishing efficiency are improved.

[0053] The weight ratio of methyl methacrylate, acrylic acid, and 2-hydroxyethyl acrylate (HEA) is preferably 100:20 to 50:10 to 30.

[0054] 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.

[0055] Furthermore, the ceria nanoparticles may be surface-treated with a silane compound.

[0056] As the silane compound, any alkoxysilane such as tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS), sodium silicate, potassium silicate, silicon tetrachloride, etc. may be used.

[0057] 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 meets this numerical range, the dispersibility, polishing speed, and polishing efficiency are maximized.

[0058] In this invention, a mixture of tetramethoxysilane and tetraethoxysilane may be used as the silane compound.

[0059] 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.

[0060] Furthermore, the ceria nanoparticles may be surface-treated with a composition prepared by mixing the acrylic mixture and the silane compound.

[0061] 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.

[0062] The content of the composition is preferably 1 to 10 parts by weight per 100 parts by weight of ceria nanoparticles, and when the content is within this numerical range, the dispersibility, polishing speed, and polishing efficiency are maximized.

[0063] 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]

[0064] Cerium carbonate was crushed and mixed, then dried.

[0065] The dried cerium carbonate was heat-treated at 500°C for 6 hours in an air atmosphere to produce ceria nanoparticles.

[0066] The aforementioned ceria nanoparticles were crushed using a ball mill to produce rod-shaped ceria nanoparticles.

[0067] Figure 1 shows the TGA and DTA results for cerium carbonate according to the present invention.

[0068] The separation of carbonate from cerium carbonate proceeds in two stages. The first stage occurs at approximately 135°C, where the water absorbed by the cerium carbonate evaporates. The second stage occurs at 200-280°C, which is the decarbonization process of cerium carbonate, with the separation almost complete at 300-400°C.

[0069] Differential thermal analysis revealed two exothermic peaks. The first was caused by the evaporation of water absorbed by cerium carbonate, while the second, broader exothermic peak was due to the separation of CO and CO2. Subsequently, crystallization occurred within the ceria particles, and it was confirmed that the separation of carbonate was almost complete at 400°C.

[0070] Figure 2 is an SEM image of the ceria nanoparticles of the present invention.

[0071] The ceria nanoparticles of the present invention have been confirmed to have a rod-shaped, dense structure.

[0072] Figure 3 is a TEM image of the ceria nanoparticles of the present invention.

[0073] The ceria nanoparticles of the present invention have been confirmed to have a rod-shaped, dense structure.

[0074] Figure 4 shows the DLS and zeta potential of the slurry composition containing ceria nanoparticles according to the present invention.

[0075] 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 131.1 nm (D50), which is approximately 13% smaller than that of commonly used ceria slurry compositions.

[0076] Furthermore, the ceria slurry composition of the present invention exhibited pH, electrical conductivity, and zeta potential comparable to those of commonly used ceria slurry compositions.

[0077] Figure 5 shows the XRD results of the ceria nanoparticles of the present invention.

[0078] 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.

[0079] Furthermore, in this invention, the surface area, pore volume, and pore size of ceria nanoparticles were analyzed at each heat treatment temperature.

[0080] The specific surface area of ​​cerium carbonate is 1.6 m². 2 The pore volume was 0.005 cc / g, the pore size was 12.72 nm, and the volume was 0.005 cc / g.

[0081] The specific surface area of ​​ceria nanoparticles fired at 400°C is 117 m². 2 The ceria nanoparticles, calcined at 500°C, had a pore volume of 0.096 cc / g, a pore size of 3.29 nm, and a specific surface area of ​​94.5 m². 2 The ceria nanoparticles, calcined at 600°C, had a pore volume of 0.083 cc / g, a pore size of 3.52 nm, and a specific surface area of ​​61.8 m². 2 The ceria nanoparticles, calcined at 700°C, had a pore volume of 0.062 cc / g, a pore size of 4.06 nm, and a specific surface area of ​​17.6 m².2 The ceria nanoparticles, calcined at 800°C, had a pore volume of 0.036 cc / g, a pore size of 8.19 nm, and a specific surface area of ​​4.1 m². 2 The pore volume was 0.021 cc / g, the pore size was 20.6 nm, and the volume was 0.021 cc / g.

[0082] Heat treatment of cerium carbonate causes the release of H2O and CO2, increasing its surface area. However, as the heat treatment temperature rises, the crystallinity of ceria increases, causing shrinkage and thus reducing the surface area again.

[0083] Furthermore, while the pore volume increases with heat treatment of cerium carbonate, it decreases again as the heat treatment temperature rises. [Examples]

[0084] Ceria nanoparticles were prepared in the same manner as in Example 1, except that they were heat-treated at 300°C. [Examples]

[0085] Ceria nanoparticles were prepared in the same manner as in Example 1, except that they were heat-treated at 900°C. [Examples]

[0086] Ceria nanoparticles were prepared in the same manner as in Example 1, except that a mixture of cerium carbonate and cerium acetate was used instead of cerium carbonate.

[0087] Here, the weight ratio of cerium carbonate to cerium acetate was adjusted to 70:30. [Examples]

[0088] Ceria nanoparticles were prepared in the same manner as in Example 1, except that instead of heat-treating cerium carbonate at 500°C for 6 hours, a primary heat treatment step was used in which cerium carbonate 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]

[0089] An acrylic mixture was prepared by mixing methyl methacrylate, acrylic acid, and 2-hydroxyethyl acrylate (HEA).

[0090] Here, the weight ratio of methyl methacrylate, acrylic acid, and 2-hydroxyethyl acrylate (HEA) was adjusted to 100:30:20.

[0091] The ceria nanoparticles prepared in Example 1 were surface-treated with the acrylic mixture.

[0092] Here, the content of the acrylic mixture was adjusted to 5 parts by weight per 100 parts by weight of ceria nanoparticles.

[0093] (Comparative Example 1) Ceria nanoparticles were prepared in the same manner as in Example 1, except that the step of crushing and mixing cerium carbonate and then drying it was omitted.

[0094] (Item to be polished) As wafers, flat silicon oxide films and silicon nitride films were used.

[0095] (CMP process conditions) The polishing process conditions are shown in Table 1.

[0096] [Table 1]

[0097] (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).

[0098] (uniformity) After polishing, the uniformity of the wafer sample was measured.

[0099] (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.

[0100] 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.

[0101] [Table 2]

[0102] 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.

[0103] In other words, the compositions of Examples 1 to 6 are judged to have excellent stopping layer formation function for silicon nitride films.

[0104] Furthermore, it can be seen that Examples 1 to 6 exhibit excellent uniformity and scratch-generating characteristics.

[0105] Examples 1, 4-6, in particular, exhibit the most excellent characteristics.

[0106] 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 preparing a ceria precursor, (b) A step of heat-treating the ceria precursor to produce rod-shaped ceria nanoparticles, (c) A method for producing ceria nanoparticles, comprising the step of pulverizing the ceria nanoparticles.

2. The method for producing ceria nanoparticles according to claim 1, characterized in that step (a) is to pulverize and stir the ceria precursor.

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

4. The method for producing ceria nanoparticles according to claim 3, characterized in that step (b) involves heat-treating the ceria precursor at 400 to 800°C for 1 to 20 hours.

5. The method for producing ceria nanoparticles according to claim 4, characterized in that step (c) is to grind the ceria nanoparticles in at least one selected from a ball mill, a rod mill, a pebble mill, a barstone mill, and a pulverizer.

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

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