Preparation method and application of nano cerium oxide used in CMP (chemical mechanical polishing)

Abstract

The invention relates to the technical field of semiconductors, and discloses a preparation method and application of nano cerium oxide used in CMP (chemical mechanical polishing), comprising the following steps: step 1, dissolving cerium nitrate in an aqueous solution or an ethanol solution, mixing and stirring to obtain a precursor solution, adding lanthanum nitrate and neodymium nitrate during mixing, and stirring to obtain a precursor solution; a mixed precursor solution is obtained; 2, adding a surfactant into the precursor solution, and uniformly stirring to obtain a mixed solution; by adding rare earth elements such as lanthanum nitrate and neodymium nitrate, the mechanical property and chemical stability of cerium oxide can be improved, the polishing efficiency of cerium oxide on materials such as glass and silicon wafers is enhanced, the doped rare earth elements can also regulate and control the distribution of oxygen vacancies, the activity of cerium oxide is improved, and the service life of cerium oxide is prolonged. The crystal structure of cerium oxide can be further adjusted through doping of boron or phosphorus, the hardness and durability of polishing particles are improved, and the polishing particles are suitable for polishing high-hardness materials.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, in particular to a preparation method of nano cerium oxide used in CMP and application thereof. Background Art

[0002] Cerium oxide is used as an abrasive in the semiconductor preparation process. Its widespread attention is mainly due to the high polishing activity of cerium oxide on silicon dioxide, and it can achieve a high polishing effect at a lower solid content. Therefore, chemical mechanical polishing liquid with cerium oxide as abrasive has greater application prospects and market advantages in terms of performance and cost compared with traditional silicon oxide or aluminum oxide materials.

[0003] The cerium oxide synthesized domestically is obtained by sintering cerium carbonate at high temperature. It has a small specific surface area, which makes the cerium oxide lose its activity. At the same time, the grinding rate is very low, and the polishing effect is low. Most of them still need imported materials. In the public document CN108249469 A, a hydrothermal method is proposed to prepare cerium oxide particles. The synthesized cerium oxide does not require other special treatments, has good dispersibility and polishing activity, and can be used as an abrasive for STI polishing. However, its durability and hardness are not improved. At the same time, there is no obvious improvement in the activity of cerium oxide, which cannot further meet the use requirements. Therefore, a preparation method and application of nano cerium oxide used in CMP are proposed.

[0004] The above information disclosed in the background technology is only used to increase the understanding of the background technology of the present application, and therefore, it may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method of nano-cerium oxide used in CMP and its application, so as to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: comprising the following steps:

[0007] Step 1: Take cerium nitrate and dissolve it in an aqueous solution or an ethanol solution, mix and stir to obtain a precursor solution, and lanthanum nitrate and neodymium nitrate may also be added during the mixing to obtain a mixed precursor solution;

[0008] Step 2: adding a surfactant to the precursor solution, stirring evenly to obtain a mixed solution, or taking trimethoxyborane as a boron source, adding it to the precursor solution, or taking nitrate phosphorus or other phosphorus source compounds as a phosphorus source, adding them to the precursor solution, mixing and stirring evenly to obtain a mixed solution;

[0009] Step 3: adding appropriate amount of water and citric acid as chelating agent while stirring the mixed solution, and controlling the reaction conditions so that the solution gradually forms a gel;

[0010] Step 4: Dry the formed gel at 80-100° C., and then calcine it in air or an inert atmosphere at a temperature between 500-700° C. for 2-4 hours to obtain cerium oxide particles.

[0011] Preferably, when preparing the mixed precursor solution, the total amount of lanthanum nitrate and neodymium nitrate added is 1:10 of cerium nitrate, wherein the ratio between lanthanum nitrate and neodymium nitrate is 1:1.

[0012] Preferably, the added surfactant may be cetyltrimethylammonium bromide or a high molecular weight substance (such as polyethylene glycol (PEG)) and stirred at a mild temperature of 60-80°C.

[0013] Preferably, when adding water and citric acid, the stirring time is 30-60 minutes and the temperature condition is 50-80°C.

[0014] The application of nano cerium oxide includes the following steps:

[0015] (1) Pre-preparation of cerium oxide particles:

[0016] The cerium oxide particles are placed in deionized water, ethanol or other solvents as a dispersion medium, and an appropriate amount of dispersant (such as polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG), etc.) is added during the dispersion process to prevent the particles from agglomerating;

[0017] Use an ultrasonic oscillator to treat for 30 minutes to several hours until the particles are evenly dispersed. The ultrasonic power and time need to be adjusted according to the properties of the particles and the dispersion effect. Use mechanical stirring or ball milling for further treatment after treatment;

[0018] According to the total weight of the polishing liquid, add an appropriate amount of stabilizer (usually 1-5% of the particle weight). After adding the stabilizer, continue ultrasonic treatment or stirring to ensure that the stabilizer is evenly distributed.

[0019] (2) Preparation of polishing liquid:

[0020] Concentration adjustment: Determine the concentration of cerium oxide particles in the polishing solution according to application requirements. Usually the concentration is in the range of 1-10wt%, and the solution is adjusted to the required concentration by dilution or concentration;

[0021] Use a pH adjuster (such as ammonia) to adjust the pH value of the polishing solution to the required range, between 7-10, to ensure good polishing effect and particle stability;

[0022] Mix the polishing liquid well under stirring to ensure that all ingredients are evenly distributed;

[0023] The polishing liquid is filtered through a 0.45 micron microporous filter membrane to remove large particles and impurities, ensuring the uniformity and purity of the polishing liquid.

[0024] In summary, this application includes the following beneficial technical effects:

[0025] By adding rare earth elements such as lanthanum nitrate and neodymium nitrate, the mechanical properties and chemical stability of cerium oxide can be improved, and its polishing efficiency for materials such as glass and silicon wafers can be enhanced. Doping with rare earth elements can also regulate the distribution of oxygen vacancies and improve the activity of cerium oxide. Doping with boron or phosphorus can further adjust the crystal structure of cerium oxide, increase the hardness and durability of its polishing particles, and make it suitable for polishing high-hardness materials. The preparation of cerium oxide particles with a mesoporous structure can increase its specific surface area, thereby improving its activity and polishing efficiency, and is particularly suitable for materials with high surface accuracy requirements. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] Embodiment 1

[0028] The present invention provides a technical solution comprising the following steps:

[0029] Step 1: dissolving cerium nitrate in an aqueous solution or an ethanol solution and mixing and stirring to obtain a precursor solution;

[0030] Step 2: adding hexadecyltrimethylammonium bromide or a polymer substance (such as polyethylene glycol (PEG)) to the precursor solution and stirring at a mild temperature of 60-80° C. to allow the surfactant or polymer substance to form an ordered self-assembled structure to obtain a mixed solution;

[0031] Step 3: adding appropriate amount of water and citric acid as chelating agent while stirring the mixed solution, and controlling the reaction conditions so that the solution gradually forms a gel;

[0032] Step 4: drying the formed gel at 80-100° C., and then calcining it in air or an inert atmosphere at a temperature between 500-700° C. for 2-4 hours. During the calcination process, the soft template material decomposes to form cerium oxide particles with a mesoporous structure.

[0033] Embodiment 2

[0034] The present invention provides a technical solution comprising the following steps:

[0035] Step 1: Take 10% cerium nitrate, 0.5% lanthanum nitrate and 0.5% neodymium nitrate, dissolve them in an aqueous solution or an ethanol solution, mix and stir, and obtain a mixed precursor solution;

[0036] Step 2: taking trimethoxyborane as a boron source, adding it to the precursor solution, or taking phosphorus nitrate or other phosphorus source compounds as a phosphorus source, adding them to the precursor solution, mixing and stirring evenly to obtain a mixed solution;

[0037] Step 3: adding appropriate amount of water and citric acid as chelating agent while stirring the mixed solution, and controlling the reaction conditions so that the solution gradually forms a gel;

[0038] Step 4: Dry the formed gel at 80-100° C., and then calcine it in air or an inert atmosphere at a temperature between 500-700° C. for 2-4 hours to obtain cerium oxide particles.

[0039] Embodiment 3

[0040] The present invention provides a technical solution comprising the following steps:

[0041] Step 1: Take cerium nitrate and dissolve it in an aqueous solution or an ethanol solution, mix and stir to obtain a precursor solution, and lanthanum nitrate and neodymium nitrate may also be added during the mixing to obtain a mixed precursor solution;

[0042] Step 2: adding a surfactant to the precursor solution, stirring evenly to obtain a mixed solution, or taking trimethoxyborane as a boron source, adding it to the precursor solution, and then taking phosphorus nitrate or other phosphorus source compounds as a phosphorus source, adding them to the precursor solution, mixing and stirring evenly to obtain a mixed solution;

[0043] Step 3: adding appropriate amount of water and citric acid as chelating agent while stirring the mixed solution, and controlling the reaction conditions so that the solution gradually forms a gel;

[0044] Step 4: Dry the formed gel at 80-100° C., and then calcine it in air or an inert atmosphere at a temperature between 500-700° C. for 2-4 hours to obtain cerium oxide particles.

[0045] Pre-preparation of cerium oxide particles:

[0046] The cerium oxide particles are placed in deionized water, ethanol or other solvents as a dispersion medium, and an appropriate amount of dispersant (such as polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG), etc.) is added during the dispersion process to prevent the particles from agglomerating;

[0047] Use an ultrasonic oscillator to treat for 30 minutes to several hours until the particles are evenly dispersed. The ultrasonic power and time need to be adjusted according to the properties of the particles and the dispersion effect. Use mechanical stirring or ball milling for further treatment after treatment;

[0048] According to the total weight of the polishing liquid, add an appropriate amount of stabilizer (usually 1-5% of the particle weight). After adding the stabilizer, continue ultrasonic treatment or stirring to ensure that the stabilizer is evenly distributed.

[0049] Preparation of polishing liquid:

[0050] Concentration adjustment: Determine the concentration of cerium oxide particles in the polishing solution according to application requirements. Usually the concentration is in the range of 1-10wt%, and the solution is adjusted to the required concentration by dilution or concentration;

[0051] Use a pH adjuster (such as ammonia) to adjust the pH value of the polishing solution to the required range, between 7-10, to ensure good polishing effect and particle stability;

[0052] Mix the polishing liquid well under stirring to ensure that all ingredients are evenly distributed;

[0053] The polishing liquid is filtered using a 0.45 micron microporous membrane to remove large particles and impurities to ensure the uniformity and purity of the polishing liquid. It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0054] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. The preparation method of nano cerium oxide used in CMP comprises the following steps: Step 1: Take cerium nitrate and dissolve it in an aqueous solution or an ethanol solution, mix and stir to obtain a precursor solution, and lanthanum nitrate and neodymium nitrate may also be added during the mixing to obtain a mixed precursor solution; Step 2: adding a surfactant to the precursor solution, stirring evenly to obtain a mixed solution, or taking trimethoxyborane as a boron source, adding it to the precursor solution, or taking nitrate phosphorus or other phosphorus source compounds as a phosphorus source, adding them to the precursor solution, mixing and stirring evenly to obtain a mixed solution; Step 3: adding appropriate amount of water and citric acid as chelating agent while stirring the mixed solution, and controlling the reaction conditions so that the solution gradually forms a gel; Step 4: Dry the formed gel at 80-100° C., and then calcine it in air or an inert atmosphere at a temperature between 500-700° C. for 2-4 hours to obtain cerium oxide particles.

2. The method for preparing nano-cerium oxide used in CMP according to claim 1, characterized in that: When preparing the mixed precursor solution, the total amount of lanthanum nitrate and neodymium nitrate added is 1:10 of cerium nitrate, wherein the ratio between lanthanum nitrate and neodymium nitrate is 1:

1.

3. The method for preparing nano-cerium oxide used in CMP according to claim 1, characterized in that: The added surfactant may be hexadecyltrimethylammonium bromide or a high molecular weight substance (such as polyethylene glycol (PEG)) and stirred at a mild temperature of 60-80°C.

4. The method for preparing nano-cerium oxide used in CMP according to claim 1, characterized in that: When adding water and citric acid, the stirring time is 30-60 minutes and the temperature condition is 50-80°C.

5. The use of nano cerium oxide according to claim 1, comprising the following steps: (1) Pre-preparation of cerium oxide particles: The cerium oxide particles are placed in deionized water, ethanol or other solvents as a dispersion medium, and an appropriate amount of dispersant (such as polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG), etc.) is added during the dispersion process to prevent the particles from agglomerating; Use an ultrasonic oscillator to treat for 30 minutes to several hours until the particles are evenly dispersed. The ultrasonic power and time need to be adjusted according to the properties of the particles and the dispersion effect. Use mechanical stirring or ball milling for further treatment after treatment; According to the total weight of the polishing liquid, add an appropriate amount of stabilizer (usually 1-5% of the particle weight). After adding the stabilizer, continue ultrasonic treatment or stirring to ensure that the stabilizer is evenly distributed. (2) Preparation of polishing liquid: Concentration adjustment: Determine the concentration of cerium oxide particles in the polishing solution according to application requirements. Usually the concentration is in the range of 1-10wt%, and the solution is adjusted to the required concentration by dilution or concentration; Use a pH adjuster (such as ammonia) to adjust the pH value of the polishing solution to the required range, between 7-10, to ensure good polishing effect and particle stability; Mix the polishing liquid well under stirring to ensure that all ingredients are evenly distributed; The polishing liquid is filtered through a 0.45 micron microporous filter membrane to remove large particles and impurities, ensuring the uniformity and purity of the polishing liquid.