A silicon oxide / silicon nitride acidic polishing liquid based on cerium oxide abrasive and preparation method thereof

Abstract

The present invention provides a silicon oxide / silicon nitride acidic polishing solution based on cerium oxide abrasive and a preparation method thereof. This polishing solution uses a quaternary ammonium salt compound as an ionic active agent. Under acidic conditions, the small-particle cerium oxide abrasive, along with an amino acid, a surfactant, and the ionic active agent, improves the polishing rate of silicon oxide and suppresses the polishing rate of silicon nitride, while achieving a lower surface roughness for silicon oxide / silicon nitride. While achieving a polishing rate for silicon oxide exceeding 0.000 nm and a polishing rate for silicon nitride below 0.000 nm, the surface roughness of both silicon oxide and silicon nitride surfaces is less than 0.1 nm.

Description

Technical Field

[0001] The invention belongs to the field of polishing liquid, and in particular relates to a high-selectivity silicon oxide / silicon nitride acidic polishing liquid based on cerium oxide abrasive and a preparation method thereof. Background Art

[0002] With the continuous development of integrated circuit technology, some leading semiconductor manufacturers have begun mass production or are developing 3nm process technology. These advanced process nodes have further reduced the size of transistors. Higher integration and performance requirements have also placed higher demands on chemical mechanical polishing (CMP) in the shallow trench isolation (STI) process. CMP is a technology that achieves global flattening by combining mechanical and chemical actions. The STI process often uses silicon oxide as the filling material for the trench and silicon nitride as the lining material for the trench sidewalls. During the production process, the silicon oxide layer needs to be polished and stopped on the silicon nitride layer.

[0003] For STI silicon oxide / silicon nitride CMP, in order to improve production efficiency and ensure that low surface roughness can be achieved immediately during the production process, the silicon oxide removal rate should be controlled within In order to maintain the structural integrity of silicon nitride, the removal rate of silicon nitride should be controlled at This is because a lower polishing rate can avoid damage and excessive removal of silicon nitride. At the same time, the surface quality of silicon oxide / silicon nitride will have a great impact on the next process, so a silicon oxide / silicon nitride film with low surface roughness is crucial.

[0004] Because cerium oxide abrasives have a high selectivity for silicon oxide and silicon nitride, they are often used in the second step of the STI CMP process. Currently, large-particle-size (100-300nm) cerium oxide abrasives are more commonly used in the industry. However, large-particle-size abrasives are prone to cause surface defects in silicon oxide / silicon nitride. For example, CN118048109A discloses a method for preparing a cerium oxide polishing liquid containing cerium oxide slurry, an organic acid additive, a pH regulator, a dispersant, and a bactericide. However, the average particle size of cerium oxide used in this technology is 170-200nm. Large-particle-size cerium oxide particles are more likely to cause defects in the actual production process. Therefore, small-particle-size (20-80nm) cerium oxide abrasives are more likely to be used in the STI CMP process. However, in these small particle size solutions (such as Oh M-H, Singh RK, Gupta S, et al. Polishing behaviors of single crystalline ceria abrasives on silicon dioxide and silicon nitride CMP[J]. Microelectronic Engineering, 2010, 87(12): 2633-2637. and Sampurno Y, Sudargho F, Zhuang Y, et al. Effect of Cerium Oxide Particle Sizes in Oxide Chemical Mechanical Planning[J]. Electrochemical and Solid-State Letters, 2009, 12(6): H191.), due to the large specific surface area of ​​small particle size cerium oxide abrasives, there are certain limitations in physical, chemical and mechanical effects compared with large particle size abrasives. During the polishing process, it is more difficult for small particle size cerium oxide abrasives to achieve a high silicon oxide polishing rate and a higher silicon oxide / silicon nitride selectivity than large particle size cerium oxide abrasives. Therefore, using small-particle cerium oxide abrasives to achieve a higher silicon oxide polishing rate while obtaining a higher silicon oxide / silicon nitride rate selectivity and lower silicon oxide / silicon nitride surface roughness is a problem that needs to be solved urgently. Summary of the Invention

[0005] The purpose of the present invention is to address the limitations of current technologies and propose a silicon oxide / silicon nitride acidic polishing liquid based on cerium oxide abrasive and a preparation method thereof. The polishing liquid uses a quaternary ammonium salt compound as an ionic active agent. Under acidic conditions, through the combined action of small-particle cerium oxide abrasives, amino acids, surfactants and ionic active agents, it achieves an improvement in the silicon oxide polishing rate and a suppression in the silicon nitride polishing rate, and obtains a lower silicon oxide / silicon nitride surface roughness. The present invention achieves a silicon oxide polishing rate of Above, silicon nitride polishing rate At the same time, the surface roughness of both silicon oxide and silicon nitride surfaces reached less than 0.1nm.

[0006] The solution of the present invention is:

[0007] A silicon oxide / silicon nitride acidic polishing liquid based on cerium oxide abrasive, the polishing liquid comprising: a mass percentage concentration of cerium oxide in the cerium oxide abrasive of 0.1 to 1%, a molar concentration of an amino acid of 0.001 to 0.1 mol / L, a molar concentration of a surfactant of 0.001 to 0.1 mol / L, a molar concentration of an ionic active agent of 0.001 to 0.1 mol / L, and the balance being water; the pH value of the polishing system being 3 to 7;

[0008] The particle size of the cerium oxide abrasive is 30 to 80 nm.

[0009] The amino acid is one or more of DL-aspartic acid (DL-Asp), arginine (Arg), glutamic acid (Glu), lysine (Lys), and proline (Pro).

[0010] The surfactant is one or more of sodium fatty alcohol ether sulfate (AES), ammonium lauryl sulfate (ADS), sodium α-olefin sulfonate (AOS), fatty alcohol polyoxyethylene ether (AEO-9), polyethylene glycol (PEG), sodium dodecylbenzene sulfonate (SDBS), and alkylphenol polyoxyethylene ether (APEO).

[0011] The ionic active agent is one or more of tetrapropylammonium hydroxide (TPAOH), TEAOH, and 1-adamantyltrimethylammonium hydroxide (ADAOH).

[0012] Preferably, the mass percentage concentration of cerium oxide in the cerium oxide abrasive is 0.4 to 0.6%;

[0013] Preferably, the molar concentration of the amino acid is 0.01 to 0.03 mol / L, and the molar concentration of the surfactant is 0.001 to 0.005 mol / L;

[0014] Preferably, the pH value of the polishing liquid system is 4.5-5.5.

[0015] The method for preparing the silicon oxide / silicon nitride acidic polishing liquid based on cerium oxide abrasive is characterized by comprising the following steps:

[0016] (1) Weighing the required amount of amino acid and adding it to the first portion of deionized water, stirring until completely dissolved to prepare a first premix;

[0017] (2) Weighing the required amount of surfactant and ionic surfactant and adding them to the second portion of deionized water, stirring until completely dissolved to prepare a second premix;

[0018] (3) adding the cerium oxide abrasive to the third portion of deionized water and stirring to obtain a third premixed solution;

[0019] (4) Pour the first premixed liquid and the second premixed liquid into the third premixed liquid while stirring, and add a pH regulator to adjust the pH value of the solution to 3-7. After stirring evenly, dilute to volume with deionized water to obtain a cerium oxide polishing liquid.

[0020] The pH regulator is one or more of sodium hydroxide, potassium hydroxide, ammonia water, phosphoric acid, hydrochloric acid, and nitric acid.

[0021] The first portion of deionized water, the second portion of deionized water and the third portion of deionized water may have the same or different masses, and each of them accounts for 10% to 45% of the mass of the total deionized water.

[0022] The essential features of the present invention are:

[0023] The use of small particle size (30-80nm) cerium oxide abrasives in combination with amino acid additives, ionic active agents, and surfactants achieved a higher silicon oxide polishing rate and a high silicon oxide / silicon nitride rate selectivity, and obtained a lower surface roughness. Carboxyl-rich amino acids carry cerium oxide particles to the silicon oxide surface through electrostatic and hydrogen bonding forces, which improves the utilization rate of cerium oxide abrasives and thereby improves the silicon oxide polishing rate. Amino acids rich in amino groups are adsorbed on the silicon nitride surface through hydrogen bonding to form an adsorption layer, which reduces the contact between the polishing liquid and the silicon nitride surface, thereby inhibiting the silicon nitride polishing rate. Therefore, different types of amino acids are compounded to increase the silicon oxide polishing rate while also reducing the silicon nitride polishing rate. The ionic active agent TEAOH can form complexes with Ce(Ⅲ) and Ce(Ⅳ) under acidic conditions. These complexes have higher reactivity and increase the Ce in cerium oxide. 3+ The utilization rate of TEAOH is high, and it can react more effectively with the silicon oxide surface, promoting the polishing rate of silicon oxide. At the same time, TEAOH can also be adsorbed on the silicon oxide surface, reducing the surface tension of silicon oxide and improving polishing efficiency.

[0024] The beneficial effects of the present invention are:

[0025] (1) The amino groups of DL-Asp and Arg are both protonated at pH 3 to 7. The protonated amino groups can form an adsorption layer on the surface of silicon nitride through hydrogen bonding, thereby reducing the contact between the polishing liquid and the silicon nitride surface and inhibiting the polishing rate of silicon nitride. At the same time, amino acids can also increase the activity of cerium oxide, promote the adsorption of cerium oxide on the surface of silicon oxide, increase the formation of Ce-O-Si bonds, thereby increasing the chemical action of the cerium oxide polishing liquid on the surface of silicon oxide and improving the polishing rate of silicon oxide. When the ratio of the two is 3:2 (Comparative Example 5), the polishing rate of silicon oxide can reach At this time, the polishing rate of silicon nitride is Compared with the case without addition, the polishing rate of silicon oxide increased by 19.6%, while the polishing rate of silicon nitride decreased by 68.0%.

[0026] (2) The addition of surfactants improves the dispersion of cerium oxide particles and the wettability of the polishing solution, thereby reducing the surface roughness of silicon oxide and silicon nitride. For example, in Example 1, the surface roughness of silicon oxide and silicon nitride were 0.062 nm and 0.046 nm, respectively. Compared with the comparative example, the surface roughness of the two was reduced by 82.8% and 75.5%, respectively.

[0027] (3) The addition of ionic active agents improves the utilization rate of Ce(III) in cerium oxide, increases the chemical interaction between cerium oxide and silicon oxide surface, and further improves the polishing rate of silicon oxide. As in Example 1, the polishing rates of silicon oxide and silicon nitride are and At this time, the polishing rate of silicon oxide increased by 41.6% compared with the comparative example, while the polishing rate of silicon nitride decreased by 90.1%.

[0028] (4) The polishing liquid of the present invention has a low solid content (0.1-1%), which saves costs, controls particle contamination, and facilitates subsequent cleaning.

[0029] (5) Finally, the present invention achieves a high removal rate of silicon oxide (higher than ) and low surface roughness (less than 0.1nm), low removal rate of silicon nitride (less than ) and low surface roughness (less than 0.1nm). It meets the CMP process requirements of the STI process in low-tech nodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the AFM image of the silicon oxide surface after being treated with the polishing liquid of Comparative Example 1.

[0031] Figure 2This is an AFM image of the silicon nitride surface after treatment with the polishing liquid of Comparative Example 1.

[0032] Figure 3 This is an AFM image of the silicon oxide surface after being treated with the polishing solution of Example 1.

[0033] Figure 4 This is an AFM image of the silicon nitride surface after being treated with the polishing liquid of Example 1.

[0034] Figure 5 This is the SEM image of the silicon oxide surface after being treated with the polishing liquid of Example 2.

[0035] Figure 6 This is an SEM image of the silicon nitride surface after being treated with the polishing liquid of Example 2. DETAILED DESCRIPTION

[0036] The present invention will be further explained below with reference to specific examples. The examples listed here are only used to illustrate the present invention, but not to limit the scope of the present invention.

[0037] The model of the chemical mechanical polisher used in this application is POLI-500 produced by G&P Technology of South Korea, equipped with a Gas_Pad_20in_GP polishing pad. The process conditions are: polishing liquid flow rate is 250ml / min, polishing head speed is 87r / min, polishing disc speed is 93r / min, polishing head pressure is 3.5psi, and holding ring pressure is 4.5psi; the cerium oxide dispersion used in the experiment is VK-Ce02W of Xuancheng Jingrui New Materials Co., Ltd.

[0038] The thickness of silicon oxide and silicon nitride films before and after polishing was measured using an F50-UV dielectric film thickness meter (F50, Filmetrics, USA). Surface roughness was measured using an atomic force microscope (AFM, Agilent 5600LS, USA). Three randomly selected areas on a 4-inch coated wafer were imaged and roughness values ​​were measured. The scanning range was 5 μm × 5 μm, and the scanning rate was 0.5 lines per second. Surface particle residue and the post-polishing surface condition were examined using a scanning electron microscope (SEM, Sigma 500, Zeiss, Germany).

[0039] Example 1

[0040] This embodiment provides a cerium oxide polishing liquid, in which the mass fraction of cerium oxide in the cerium oxide polishing liquid is 0.5% (the particle size of the cerium oxide abrasive is 30 to 80 nm, and the average particle size is 50 nm), the concentration of DL-Asp is 0.02 mol / L, the concentration of Arg is 0.02 mol / L, the concentration of ADS is 0.003 mol / L, the concentration of TEAOH is 0.003 mol / L, the pH value is adjusted to 4.5-5.5 using a pH regulator, and the balance is deionized water.

[0041] This embodiment also provides a method for preparing 1L of the above-mentioned cerium oxide polishing liquid, the preparation method comprising the following steps:

[0042] (1) Weigh 0.02 mol of amino acid DL-Asp and 0.02 mol of amino acid Arg and add them to deionized water, stirring until completely dissolved to prepare premix 1;

[0043] (2) Weigh 0.003 mol of surfactant ADS and 0.003 mol of ionic active agent TEAOH and add them to deionized water, stir evenly, and prepare premix 2;

[0044] (3) Add 25 ml of 20% cerium oxide dispersion to another portion of deionized water and stir evenly;

[0045] (4) Pour premix 1 and premix 2 into the mixture while stirring, and add potassium hydroxide / phosphoric acid to adjust the pH value of the solution to 4.5-5.5. After stirring evenly, dilute the volume to 1 L with deionized water to obtain a cerium oxide polishing solution.

[0046] Example 2

[0047] This embodiment provides a cerium oxide polishing liquid, in which the mass fraction of cerium oxide in the cerium oxide polishing liquid is 0.5% (the particle size of the cerium oxide abrasive is 30 to 80 nm, and the average particle size is 50 nm), the concentration of DL-Asp is 0.02 mol / L, the concentration of Arg is 0.02 mol / L, the concentration of AEO-9 is 0.004 mol / L, the concentration of TEAOH is 0.002 mol / L, the pH value is adjusted to 4.5-5.5 using a pH regulator, and the balance is deionized water.

[0048] This embodiment also provides a method for preparing 1L of the above-mentioned cerium oxide polishing liquid, the preparation method comprising the following steps:

[0049] (1) Weigh 0.02 mol of amino acid DL-Asp and 0.02 mol of amino acid Arg and add them to deionized water, stirring until completely dissolved to prepare premix 1;

[0050] (2) Weigh 0.004 mol of surfactant AEO-9 and 0.002 mol of ionic surfactant TEAOH and add them to deionized water, stirring until completely dissolved to prepare premix 2;

[0051] (3) Add 25 ml of 20% cerium oxide dispersion to another portion of deionized water and stir evenly;

[0052] (4) Pour premix 1 and premix 2 into the mixture while stirring, and add potassium hydroxide / phosphoric acid to adjust the pH value of the solution to 4.5-5.5. After stirring evenly, dilute the volume to 1 L with deionized water to obtain a cerium oxide polishing solution.

[0053] Example 3

[0054] This embodiment provides a cerium oxide polishing liquid, in which the mass fraction of cerium oxide in the cerium oxide polishing liquid is 0.5% (the particle size of the cerium oxide abrasive is 30 to 80 nm, and the average particle size is 50 nm), the concentration of DL-Asp is 0.02 mol / L, the concentration of Arg is 0.02 mol / L, the concentration of PEG is 0.002 mol / L, the concentration of TEAOH is 0.004 mol / L, the pH value is adjusted to 4.5-5.5 using a pH regulator, and the balance is deionized water.

[0055] This embodiment also provides a method for preparing 1L of the above-mentioned cerium oxide polishing liquid, the preparation method comprising the following steps:

[0056] (1) Weigh 0.02 mol of amino acid DL-Asp and 0.02 mol of amino acid Arg and add them to deionized water, stirring until completely dissolved to prepare premix 1;

[0057] (2) Weigh 0.002 mol of the surfactant PEG and 0.004 mol of the ionic active agent TEAOH and add them to deionized water, stirring until completely dissolved to prepare premix 2;

[0058] (3) Add 25 ml of 20% cerium oxide dispersion to another portion of deionized water and stir evenly;

[0059] (4) Pour premix 1 and premix 2 into the mixture while stirring, and add potassium hydroxide / phosphoric acid to adjust the pH value of the solution to 4.5-5.5. After stirring evenly, dilute the volume to 1 L with deionized water to obtain a cerium oxide polishing solution.

[0060] Comparative Example 1

[0061] This comparative example provides a cerium oxide polishing liquid, in which the mass fraction of cerium oxide is 0.5% (the particle size of the cerium oxide abrasive is 30-80 nm, and the average particle size is 50 nm), the pH value is adjusted to 4.5-5.5 using a pH regulator, and the balance is deionized water.

[0062] Comparative Example 2

[0063] This comparative example provides a cerium oxide polishing liquid, in which the mass fraction of cerium oxide in the cerium oxide polishing liquid is 0.5% (the particle size of the cerium oxide abrasive is 30-80 nm, and the average particle size is 50 nm), the concentration of DL-Asp is 0.008 mol / L, the concentration of Arg is 0.032 mol / L, the pH value is adjusted to 4.5-5.5 using a pH regulator, and the balance is deionized water.

[0064] This comparative example also provides a method for preparing 1L of the above-mentioned cerium oxide polishing liquid, which comprises the following steps:

[0065] (1) Weigh 0.008 mol of amino acid DL-Asp and 0.032 mol of amino acid Arg and add them to deionized water, stirring until completely dissolved to prepare a premix solution;

[0066] (2) Add 25 ml of 20% cerium oxide dispersion to another portion of deionized water and stir evenly;

[0067] (3) Pour the premixed solution into the mixture while stirring, and add potassium hydroxide / phosphoric acid to adjust the pH value of the solution to 4.5-5.5. After stirring evenly, dilute the volume to 1 L with deionized water to obtain a cerium oxide polishing solution.

[0068] Comparative Example 3

[0069] The other steps were the same as those in Comparative Example 2, except that the concentration of DL-Asp was 0.016 mol / L and the concentration of Arg was 0.024 mol / L.

[0070] Comparative Example 4

[0071] The other steps were the same as those in Comparative Example 2, except that the concentration of DL-Asp was 0.02 mol / L and the concentration of Arg was 0.02 mol / L.

[0072] Comparative Example 5

[0073] The other steps were the same as those in Comparative Example 2, except that the concentration of DL-Asp was 0.024 mol / L and the concentration of Arg was 0.016 mol / L.

[0074] Comparative Example 6

[0075] The other steps were the same as those in Comparative Example 2, except that the concentration of DL-Asp was 0.032 mol / L and the concentration of Arg was 0.008 mol / L.

[0076] The cerium oxide polishing solutions prepared in Examples 1-3 and Comparative Examples 1-6 were used for STI polishing. The polishing rates of silicon oxide and silicon nitride obtained by CMP of 4-inch silicon oxide and silicon nitride coated wafers were shown in Table 1, as well as the rate selection ratio of silicon oxide / silicon nitride.

[0077] Table 1

[0078]

[0079] The following points can be seen from the data in Table 1:

[0080] (1) A comprehensive comparison of the data of Comparative Examples 2-6 shows that by adjusting the ratio of different types of amino acids, the polishing rate of silicon oxide can be improved to varying degrees, and the polishing rate of silicon nitride can be suppressed to varying degrees, thereby regulating the rate selectivity of silicon oxide / silicon nitride. Under optimal conditions, the polishing rate of silicon oxide can reach above.

[0081] (2) A comprehensive comparison of the data from Examples 1-3 and Comparative Examples 1-6 shows that the addition of surfactants and ionic surfactants can, to a certain extent, increase the polishing rate of silicon oxide while reducing the polishing rate of silicon nitride. The silicon oxide / silicon nitride selectivity can reach above 16, achieving excellent polishing results.

[0082] By comparison Figure 1 and Figure 3 、 Figure 2 and Figure 4 It can be concluded that the present invention, by controlling the ratio of different types of amino acids and combining the effects of surfactants and ionic surfactants, can reduce the surface roughness of silicon oxide from 0.360 nm to 0.062 nm, and the surface roughness of silicon nitride from 0.188 nm to 0.046 nm, thereby achieving good polishing effects.

[0083] pass Figure 5 and Figure 6 It can be concluded that the cerium oxide polishing liquid provided by the present invention can achieve only a few surface particles remaining on the surfaces of silicon oxide and silicon nitride after polishing while satisfying the polishing rate and selectivity, thereby achieving a good polishing effect.

[0084] In summary, the cerium oxide polishing liquid provided by the present invention has a high silicon oxide polishing rate, a low silicon nitride polishing rate, and a high silicon oxide / silicon nitride rate selectivity ratio. The surface roughness of both the polished silicon oxide and silicon nitride is low, and minimal surface particle residue remains after polishing, achieving excellent polishing results.

[0085] The applicant declares that the above detailed description of the preparation method of the cerium oxide polishing liquid for the STI process with reference to the specific embodiment is for illustration only and not for limitation. Any changes or modifications that can be easily conceived by the present invention are within the scope of protection of the present invention.

[0086] Matters not covered by the present invention are known technologies.

Claims

1. A silicon oxide / silicon nitride acidic polishing liquid based on cerium oxide abrasive, characterized by The polishing liquid comprises: a cerium oxide abrasive having a mass percentage concentration of 0.1-1%, amino acids DL-aspartic acid (DL-Asp) and arginine (Arg), both of which have a concentration of 0.02 mol / L in the polishing liquid; a surfactant having a molar concentration of 0.001-0.1 mol / L, an ionic active agent having a molar concentration of 0.001-0.1 mol / L, and deionized water as the balance; and a polishing liquid system having a pH value of 3-7. The surfactant is one or more of sodium fatty alcohol ether sulfate, ammonium lauryl sulfate, sodium α-olefin sulfonate, fatty alcohol polyoxyethylene ether, polyethylene glycol (PEG), sodium dodecylbenzene sulfonate, and alkylphenol polyoxyethylene ether; The ionic active agent is one or more of tetrapropylammonium hydroxide (TPAOH), TEAOH, and 1-adamantyltrimethylammonium hydroxide (ADAOH).

2. The silicon oxide / silicon nitride acidic polishing liquid based on cerium oxide abrasive according to claim 1, characterized in that: The cerium oxide abrasive particle size is 30-80 nm.

3. The silicon oxide / silicon nitride acidic polishing liquid based on cerium oxide abrasive according to claim 1, characterized in that: The molar concentration of the surfactant is 0.001-0.005 mol / L.

4. The silicon oxide / silicon nitride acidic polishing liquid based on cerium oxide abrasive according to claim 1, characterized in that: The pH value of the polishing liquid system is 4.5-5.

5.

5. The method for preparing a silicon oxide / silicon nitride acidic polishing liquid based on cerium oxide abrasive according to claim 1, characterized in that: The following steps are involved: (1) Weigh the required amount of amino acid and add it to the first portion of deionized water, stirring until completely dissolved to prepare the first premix; (2) Weighing the required amount of surfactant and ionic surfactant and adding them to the second portion of deionized water, stirring until completely dissolved to prepare a second premix; (3) adding the cerium oxide abrasive into the third portion of deionized water and stirring to obtain a third premixed solution; (4) Pour the first premixed liquid and the second premixed liquid into the third premixed liquid while stirring, and add a pH regulator to adjust the pH value of the solution to 3-7. After stirring evenly, dilute to volume with deionized water to obtain a cerium oxide polishing liquid.

6. The method for preparing a silicon oxide / silicon nitride acidic polishing liquid based on cerium oxide abrasive according to claim 5, characterized in that: The pH regulator is one or more of sodium hydroxide, potassium hydroxide, ammonia water, phosphoric acid, hydrochloric acid, and nitric acid.

7. The method for preparing a silicon oxide / silicon nitride acidic polishing liquid based on cerium oxide abrasive according to claim 5, characterized in that: The first portion of deionized water, the second portion of deionized water, and the third portion of deionized water may have the same or different masses, and each of the portions is 10% to 45% of the mass of the total deionized water.

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