Preparation method of lanthanum precursor
A one-pot method was used to prepare lanthanum precursors by reacting alkyl diimines with LaCl3·(THF)x to prepare N,N'-dialkylformamidinium lithium salts. This method solved the problems of difficult synthesis, low yield, and high cost of lanthanum precursors, and achieved efficient and low-cost preparation of lanthanum precursors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-04-14
AI Technical Summary
The synthesis of existing lanthanum precursors is difficult, has low yield, high cost, and complex process.
Lanthanum precursors were prepared using a one-pot method, and N,N'-dialkylformamidinium lithium salts were prepared by reacting alkyldiimides with LaCl3·(THF)x. No purification was required during the reaction process.
This study achieved the preparation of lanthanum precursors with simple process, high yield, and high purity, solving the problems of difficult synthesis and high cost.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor materials, and more specifically to a method for preparing a lanthanum precursor. Background Technology
[0002] Lanthanum oxide (La₂O₃) is a white solid powder with a melting point of 2315℃ and a boiling point of 4200℃, classifying it as a high-melting-point and high-boiling-point substance. With ongoing research, La₂O₃ and La-based oxides have been applied in various fields, including optical coatings and fuel cells. Due to its high dielectric constant (High-K) and wide bandgap (5.5 eV), lanthanum oxide has found widespread use in the semiconductor industry. La₂O₃ can be used to fabricate gate oxide thin films and as a high-dielectric-constant (High-K) layer in memory chips. Therefore, the importance of lanthanum precursors is self-evident.
[0003] Cyclopentadienyl La complexes are the most common and earliest used La precursors. These precursors suffer from easy polymerization and poor thermal stability. Later, with further research, in 2005, JANI et al. reported amidine-based La precursors. These precursors have high melting points and low volatility, making them excellent precursors. Subsequently, ROHM and Haas Electronic Materials reported N,N'-diisopropylmethylamidine precursors and obtained the corresponding lanthanum oxide films using ALD with O3 as an auxiliary source. However, the synthesis of these amidine-based complexes still faces challenges, including low yield and high cost.
[0004] Therefore, providing a method for producing a lanthanum precursor that is simple to process, has a high yield, and high purity is a problem that those skilled in the art should continue to solve. Summary of the Invention
[0005] In view of this, the present invention provides a one-pot method for preparing lanthanum precursors. The reaction process requires no additional purification and is simple.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a lanthanum precursor, wherein the lanthanum precursor is obtained by reacting a substrate with an alkyldiimide and then further reacting it with LaCl3·(THF)x, the reaction process being as follows: ; The substrate is an alkyl metal complex or a metal hydride, and the substrate has the general formula R3-M, where M is any one of an alkali metal or an alkaline earth metal, preferably Li, Na, K or Mg; R3 is independently selected from hydrogen, C1 to C5 straight-chain or branched alkyl groups; R1 and R2 are each independently selected from at least one of hydrogen, C1 to C10 straight-chain or branched alkyl, C3-C8 cycloalkyl or cycloalkenyl.
[0007] In LaCl3(THF)x, x takes values from 0.7 to 2.
[0008] Furthermore, the preparation method for the above-mentioned lanthanum precursor includes the following steps: (1) Under a protective atmosphere, alkyldiimide is added to the reaction solvent, and then the substrate is added to react and a reaction solution is obtained; (2) Add LaCl3·(THF)x to the reaction solution to carry out the reaction and obtain the lanthanum precursor.
[0009] Furthermore, the protective atmosphere described in step (1) is a nitrogen atmosphere or an argon atmosphere.
[0010] Furthermore, in step (1), the reaction temperature between the substrate and the alkyldiimide is -40℃ to 0℃, and the reaction time is 0.5-6h.
[0011] The beneficial effect of adopting the above-mentioned further solutions is that the above-mentioned solutions of the present invention can effectively prevent the reaction from being too violent, while ensuring that the reaction is sufficient.
[0012] Furthermore, the reaction solvent is any one or a mixture of n-hexane, tetrahydrofuran, diethyl ether, and dioxane.
[0013] The beneficial effect of adopting the above-mentioned further solution is that the solvent of the present invention can stabilize the LaCl3 intermediate.
[0014] Furthermore, the molar ratio of LaCl3·(THF)x, substrate, and alkyldiimide is 1:(2.4-4.5):(3.6-6).
[0015] The beneficial effect of adopting the above-described further scheme is that the above-described proportions of the present invention can effectively improve the reaction yield.
[0016] Furthermore, in step (2), the reaction temperature is 20-50℃ and the reaction time is 12-24h.
[0017] Furthermore, the reaction process in step (1) is shown in Equation 1:
[0018] Formula 1 Furthermore, the reaction process in step (2) is shown in Equation 2:
[0019] Formula 2 Furthermore, after the reaction is complete, the reaction includes filtration using a sand filter and sublimation at 0.001-20 Tor and 50-200°C.
[0020] The beneficial effects of this invention are as follows: This invention uses alkyl metal complexes or metal hydrides to react with alkyl diimine to prepare N,N'-dialkylformamidinium lithium salt, and further reacts it with LaCl3·THF to obtain lanthanum complexes. The preparation is carried out in a one-pot method, without the need for purification in the intermediate process, and the reaction is simple, which solves the problem of complex synthesis process of lanthanum complexes. Detailed Implementation
[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0022] Example 1 A method for preparing a lanthanum precursor, in this embodiment, LaCl3(THF)x was titrated to obtain x=1.5, that is, this embodiment specifically describes a method for preparing tris(N,N'-diisopropylmethylamidinyl)lanthanum(III), including the following steps: (1) Under nitrogen atmosphere protection, weigh diisopropyl diimine (206.0 g, 1.6 mol), dissolve it in 3 L of diethyl ether, add lithium hydride (11.3 g, 1.4 mol) at -30 °C, react for 4 h to obtain amidine salt reaction solution.
[0023] (2) LaCl3(THF) 1.5 (143.9 g, 0.4 mol) was added to the reaction solution, reacted at 25 °C for 12 h, filtered, and the filtrate was dried under vacuum to obtain 192 g of white solid. The white solid was sublimated under vacuum to obtain 166 g of white solid, and the yield was calculated to be 79.3%. The purity was 5N according to ICP test.
[0024] The product obtained in Example 1 was subjected to 1H NMR spectroscopy, and the results are as follows: 1H NMR (400 MHz, DMSO-d6) 8.19 (s, 1H), 3.08 (p, J = 6.4 Hz, 2H), 1.03 (d, J = 6.5 Hz, 12H).
[0025] Example 2 A method for preparing a lanthanum precursor, in this embodiment, LaCl3(THF)x was titrated to obtain x=1.5, that is, this embodiment specifically describes a method for preparing tris(N,N'-diisopropylacetamidine)lanthanum(III), including the following steps: (1) Under nitrogen atmosphere protection, weigh diisopropyl diimine (206.0 g, 1.6 mol), dissolve it in 3 L of diethyl ether, add methyl lithium (1.6 M in Et2O, 875 mL, 1.4 mol) at -30 °C, react for 4 h to obtain amidine salt reaction solution.
[0026] (2) LaCl3(THF) 1.5 (143.9g, 0.4mol) was added to the reaction solution, reacted at 25℃ for 12h, filtered, and the filtrate was dried under vacuum to obtain 204g of white solid. The white solid was sublimated under vacuum to obtain 183g of white solid. The calculated yield was 80.9%, and the purity was 5N according to ICP test.
[0027] The product obtained in Example 2 was subjected to 1H NMR spectroscopy, and the results are as follows: 1H NMR (C6D6, 25℃): 1.20 (d, 12H), 1.67 (s, 3H), 3.46 (m, 2H).
[0028] Example 3 A method for preparing a lanthanum precursor, in this embodiment, LaCl3(THF)x was titrated to obtain x=1.5, that is, this embodiment specifically describes a method for preparing tris(N,N'-diisopropylbutamidine)lanthanum(III), including the following steps: (1) Under nitrogen atmosphere protection, weigh diisopropyl diimide (206.0 g, 1.6 mol), dissolve it in 3 L of diethyl ether, add n-butyllithium (1.6 M in Et2O, 875 mL, 1.4 mol) at -30 °C, react for 4 h to obtain amidine salt reaction solution.
[0029] (2) LaCl3(THF) 1.5 (143.9g, 0.4mol) was added to the reaction solution, reacted at 25℃ for 12h, filtered, and the filtrate was dried under vacuum to obtain 252g of white solid. The white solid was sublimated under vacuum to obtain 205g of white solid. The calculated yield was 74.3%, and the purity was 5N according to ICP test.
[0030] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.
Claims
1. A method for preparing a lanthanum precursor, characterized in that, The lanthanum precursor is obtained by reacting the substrate with an alkyldiimide, followed by a further reaction with LaCl3·(THF)x. The reaction process is as follows: ； The substrate is an alkyl metal complex or a metal hydride, and the substrate has the general formula R3-M, where M is any one of an alkali metal or an alkaline earth metal, and R3 is independently selected from hydrogen, C1 to C5 straight-chain or branched alkyl groups. R1 and R2 are each independently selected from at least one of hydrogen, C1 to C10 straight-chain or branched alkyl, C3-C8 cycloalkyl or cycloalkenyl; In LaCl3(THF)x, x takes values from 0.7 to 2.
2. The method for preparing a lanthanum precursor according to claim 1, characterized in that, The preparation steps are as follows: (1) Under a protective atmosphere, alkyldiimide is added to the reaction solvent, and then the substrate is added to react and a reaction solution is obtained; (2) Add LaCl3·(THF)x to the reaction solution to carry out the reaction and obtain the lanthanum precursor.
3. The method for preparing a lanthanum precursor according to claim 2, characterized in that, The protective atmosphere mentioned in step (1) is a nitrogen atmosphere or an argon atmosphere.
4. The method for preparing a lanthanum precursor according to claim 3, characterized in that, In step (1), the reaction temperature of the substrate with the alkyldiimide is -40℃ to 0℃, and the reaction time is 0.5-6h.
5. The method for preparing a lanthanum precursor according to claim 4, characterized in that, The reaction solvent is any one or a mixture of n-hexane, tetrahydrofuran, diethyl ether, and dioxane.
6. The method for preparing a lanthanum precursor according to claim 2, characterized in that, The molar ratio of LaCl3·(THF)x, substrate, and alkyldiimide is 1:(2.4-4.5):(3.6-6).
7. The method for preparing a lanthanum precursor according to claim 2, characterized in that, In step (2), the reaction temperature is 20-50℃ and the reaction time is 12-24h.
8. The method for preparing a lanthanum precursor according to claim 2, characterized in that, After the reaction is complete, the process includes filtration using a sand core filter and sublimation at 0.001-20 Tor and 50-200°C.