A preparation method of an ALD precursor lanthanum complex

Abstract

The application discloses a preparation method of an ALD precursor lanthanum complex, and comprises the following steps: mixing and reacting a lanthanum chloride tetrahydrofuran complex LaCl3.xTHF and a hexamethyldisilazane metal salt MN(SiMe3)2 to obtain an intermediate 1; wherein M is a monovalent metal; mixing and reacting the intermediate 1 and lithium N,N'-diisopropylformamidine Li(iPrNC=NiPr) to obtain an intermediate 2; and mixing and reacting the intermediate 2 and N,N'-diisopropylformamidine to obtain the ALD precursor lanthanum complex. The application adopts a multi-step method of 'in-situ generation / ligand exchange', controls steric hindrance and reaction kinetics to reduce dimer impurities in the final product, and obtains high-purity tri(N,N'-diisopropylformamidinate) lanthanum.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, specifically to a method for preparing lanthanum complexes, precursors of ALD. Background Technology

[0002] The background of lanthanum oxide thin films is closely related to the development of the electronics industry. With the continuous increase in the integration of circuit devices, researchers are committed to improving the performance of electronic devices and reducing manufacturing costs. In this process, the feature size of metal-oxide-semiconductor field-effect transistors (MOSFETs) is gradually shrinking, and the requirements for the gate dielectric layer are becoming increasingly stringent.

[0003] Traditional silicon dioxide gate dielectrics require an equivalent oxide layer thickness of less than 10 nm when MOSFET feature sizes shrink to below the 22 nm process node, which silicon dioxide cannot meet. While HfO2 dielectrics have been considered, they suffer from drawbacks such as low crystallization temperature and insufficient dielectric constant. Therefore, lanthanum oxide, as a novel candidate material for high-dielectric-constant gate dielectrics, has attracted attention due to its higher crystallization temperature and higher dielectric constant.

[0004] Currently, there are various methods for preparing lanthanum oxide thin films, mainly including two categories: gas-phase methods and liquid-phase methods. These films are widely used as substrate materials and electronic isolation layers in electronic devices, such as field emission displays and field electron emitters. In addition, lanthanum oxide thin films can also be used to prepare electronic components such as solid oxide fuel cells, capacitors, and electrolytic capacitors.

[0005] Tris(N,N'-diisopropylformamido)lanthanum, a class of lanthanide organometallic compounds with good volatility and high thermal stability, can be used as an electronic chemical in the fields of atomic layer deposition (ALD) or chemical vapor deposition (CVD) to prepare lanthanum oxide thin films.

[0006] Traditional methods for preparing tris(N,N'-diisopropylformamido)lanthanum often result in the presence of dimers in the final product, leading to vapor pressure instability and poor reproducibility. Therefore, developing a method for preparing the high-purity ALD precursor lanthanum complex tris(N,N'-diisopropylformamido)lanthanum is of great significance. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for preparing lanthanum complexes that are precursors to ALD. The method employs a multi-step approach of "in-situ generation / ligand exchange" and reduces dimer impurities in the final product by controlling steric hindrance and reaction kinetics, thereby obtaining high-purity tris(N,N'-diisopropylformamido)lanthanum.

[0008] To address the aforementioned technical problems, this invention provides a method for preparing lanthanum complexes, precursors of ALD, comprising the following steps:

[0009] S1. Lanthanum chloride tetrahydrofuran complex LaCl3·xTHF and hexamethyldisilazane metal salt MN(SiMe3)2 are mixed and reacted to obtain intermediate 1; wherein, M is a monovalent metal;

[0010] S2. The intermediate 1 and N,N'-diisopropylformamidinium lithium (iPrNC=NiPr) are mixed and reacted to obtain intermediate 2;

[0011] S3. The intermediate 2 is mixed and reacted with N,N'-diisopropylformamidinium to obtain the ALD precursor lanthanum complex tris(N,N'-diisopropylformamido)lanthanum.

[0012] This invention employs a multi-step method of "in-situ generation / ligand exchange," which reduces dimer impurities in the final product by controlling steric hindrance and reaction kinetics. Specifically, in S1, one chloride ion in the lanthanum chloride tetrahydrofuran complex is replaced by a hexamethyldisilazane metal salt; in S2, the remaining two chloride ions in intermediate 1 are replaced by lithium N,N'-diisopropylformamidinium; and in S3, the -N(SiMe3)2 group is replaced by N,N'-diisopropylformamidinium, yielding the target product tris(N,N'-diisopropylformamido)lanthanum with a purity of up to 99%.

[0013] This invention prepares high-purity tris(N,N'-diisopropylformamido)lanthanum, which can be applied to MOCVD / ALD to prepare lanthanum oxide or other lanthanum-containing thin films. Process parameters (such as vaporization temperature, carrier gas flow rate, and deposition temperature) do not need to be adjusted to compensate for vapor pressure fluctuations caused by the presence of dimers. The deposited lanthanum oxide or other lanthanum-containing thin films have better uniformity, density, and fewer defects. The high-purity monomer compound does not exhibit selective residue during sublimation (dimers remain at the bottom of the vial due to their low volatility). The precursor can be stably and completely transported until it is used up, improving the service life and utilization rate of the precursor source vial.

[0014] Furthermore, the molar ratio of the lanthanum chloride tetrahydrofuran complex, hexamethyldisilazane potassium salt, lithium N,N'-diisopropylformamidinium, and N,N'-diisopropylformamidinium is 1:(0.9-1.1):(1.9-2.1):(0.9-1.1).

[0015] Furthermore, the reaction temperature for S1-S3 is 100-120℃.

[0016] Furthermore, the method for preparing the N,N'-diisopropylformamidinium lithium is as follows: N,N'-diisopropylformamidinium is mixed and reacted with n-butyllithium to obtain the N,N'-diisopropylformamidinium lithium.

[0017] Furthermore, the reaction temperature of the N,N,-diisopropylformamidinium and n-butyllithium mixture is -35℃ to -25℃.

[0018] Furthermore, the molar ratio of N,N,-diisopropylformamidinium to n-butyllithium is 1:(0.9-1.1).

[0019] Furthermore, the preparation method of the lanthanum chloride tetrahydrofuran complex is as follows: lanthanum chloride and tetrahydrofuran are mixed and heated, and the solution is removed under reduced pressure to obtain the lanthanum chloride tetrahydrofuran complex.

[0020] Furthermore, the temperature at which the lanthanum chloride and tetrahydrofuran are mixed and heated is 65-75°C.

[0021] Furthermore, in the LaCl3·xTHF, x = 1-1.5.

[0022] Furthermore, the metal of the hexamethyldisilazane metal salt is Li, K, or Na.

[0023] The beneficial effects of this invention are:

[0024] This invention employs a multi-step method of "in-situ generation / ligand exchange" to reduce dimer impurities in the final product by controlling steric hindrance and reaction kinetics, thereby obtaining high-purity tris(N,N'-diisopropylformamido)lanthanum with a purity of up to 99%. Attached Figure Description

[0025] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is the NMR spectrum of the product obtained in Example 1 of the present invention;

[0027] Figure 2 This is the NMR spectrum of the intermediate obtained in Comparative Example 1 of the present invention;

[0028] Figure 3 This is the NMR spectrum of the product obtained in Comparative Example 1 of the present invention. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. 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.

[0030] This embodiment provides a method for preparing lanthanum complexes, which are precursors to ALD, including the following steps:

[0031] S1. Lanthanum chloride tetrahydrofuran complex LaCl3·xTHF and hexamethyldisilazane metal salt MN(SiMe3)2 are mixed and reacted to obtain intermediate 1; wherein, M is a monovalent metal;

[0032] S2. The intermediate 1 and N,N'-diisopropylformamidinium lithium (iPrNC=NiPr) are mixed and reacted to obtain intermediate 2;

[0033] S3. The intermediate 2 is mixed and reacted with N,N'-diisopropylformamidinium to obtain the ALD precursor lanthanum complex tris(N,N'-diisopropylformamido)lanthanum.

[0034] This embodiment employs a multi-step "in-situ generation / ligand exchange" method. By controlling steric hindrance and reaction kinetics, dimer impurities in the final product are reduced. Specifically, in S1, one chloride ion in the lanthanum chloride tetrahydrofuran complex is replaced by a hexamethyldisilazane metal salt; in S2, the remaining two chloride ions in intermediate 1 are replaced by lithium N,N'-diisopropylformamidinium; and in S3, the -N(SiMe3)2 group is replaced by N,N'-diisopropylformamidinium to obtain the target product tris(N,N'-diisopropylformamido)lanthanum with a purity of up to 99%. High-purity tris(N,N'-diisopropylformamido)lanthanum is thus obtained. N'-Diisopropylformamido)lanthanum is used in MOCVD / ALD to prepare lanthanum oxide or other lanthanum-containing thin films. Process parameters (such as vaporization temperature, carrier gas flow rate, and deposition temperature) do not need to be adjusted to compensate for vapor pressure fluctuations caused by the presence of dimers. The deposited lanthanum oxide or other lanthanum-containing thin films have better uniformity, density, and fewer defects. High-purity monomer compounds do not exhibit selective residues during sublimation (dimers remain at the bottom of the vial due to their low volatility). The precursor can be stably and completely transported until it is used up, improving the lifespan and utilization rate of the precursor source vial.

[0035] In a preferred embodiment, the molar ratio of the lanthanum chloride tetrahydrofuran complex, potassium hexamethyldisilazane, lithium N,N'-diisopropylformamidinium, and N,N'-diisopropylformamidinium is 1:(0.9-1.1):(1.9-2.1):(0.9-1.1); and the reaction temperature of S1-S3 is 100-120℃.

[0036] As a preferred embodiment, the method for preparing the N,N'-diisopropylformamidinium lithium is as follows: N,N'-diisopropylformamidinium and n-butyllithium are mixed and reacted to obtain the N,N'-diisopropylformamidinium lithium; the temperature for the mixing and reaction of N,N'-diisopropylformamidinium and n-butyllithium is -35℃ to -25℃; the molar ratio of N,N'-diisopropylformamidinium to n-butyllithium is 1:(0.9-1.1).

[0037] As a preferred embodiment, the method for preparing the lanthanum chloride tetrahydrofuran complex is as follows: lanthanum chloride and tetrahydrofuran are mixed and heated, and the solution is removed under reduced pressure to obtain the lanthanum chloride tetrahydrofuran complex; the heating temperature for mixing lanthanum chloride and tetrahydrofuran is 65-75℃; and x = 1-1.5 in the LaCl3·xTHF.

[0038] In a preferred embodiment, the metal of the hexamethyldisilazane metal salt is Li, K or Na.

[0039] Example 1

[0040] This embodiment relates to a method for preparing tris(N,N'-diisopropylformamido)lanthanum, comprising the following steps:

[0041] (1) Weigh lanthanum chloride LaCl3 (9.32 g, 0.038 mol) into reaction flask 1, add 45 ml of tetrahydrofuran and heat at 70 °C for 2 h, then desolvent under reduced pressure to obtain LaCl3·xTHF; take 38 ml of potassium hexamethyldisilazane KN(SiMe3)21.0 M (7.58 g, 0.038 mol) into reaction flask 2, desolvent and replace with toluene solution, transfer the solution in reaction flask 2 to reaction flask 1, heat at 110 °C for 2 h to obtain intermediate 1.

[0042] (2) Weigh N,N,-diisopropylformamidinium (10.23 g, 0.08 mol) into reaction flask 3, add 60 ml of n-hexane to dissolve it, add n-butyllithium (5.11 g, 0.08 mol) at -30℃, after desolvation, add 60 ml of toluene to obtain a toluene solution of Li (iPrNC=NiPr), transfer the solution in reaction flask 3 to reaction flask 1, heat at 110℃ for 2 h to obtain intermediate 2.

[0043] (2) Weigh N,N,-diisopropylformamidinium (5.12 g, 0.04 mol) into reaction flask 4, add toluene to dissolve it, and then transfer it to reaction flask 1. React at 110 °C for 2 h, remove solvent under reduced pressure, and sublimate at 120 °C under reduced pressure of 0.2 Torr to obtain 18.19 g of tris(N,N'-diisopropylformamido)lanthanum La(ipr2-FMD)3, with a yield of 92% and a purity of 99%, and no dimers were found as impurities.

[0044] The NMR spectrum of the product is as follows Figure 1 As shown, the NMR results are: 1 HNMR (400 MHz, C6D6): δ (ppm) = 8.30, (3H, -CH-), 3.16, 3.18, 3.19, 3.21, 3.23 (6H, -CH(CH3)2), 1.21, 1.23 (36H, -CH3).

[0045] Comparative Example 1

[0046] This comparative design presents a method for preparing tris(N,N'-diisopropylformamido)lanthanum, comprising the following steps:

[0047] (1) Take LaCl3 (9.32g, 0.038mol) into reaction flask 1, add 45ml THF and heat at 70℃ for 2h, then desolvate under reduced pressure to obtain LaCl3·xTHF;

[0048] (2) Take 38 ml of KN(SiMe3)2 3.0M (22.74 g, 0.114 mol) into reaction flask 2, replace the solvent with toluene solution, transfer the solution from reaction flask 2 to reaction flask 1, heat at 110℃ for 2 h, filter to remove solvent, and sublimate at 170℃ under reduced pressure for 2 torr to obtain the intermediate product La(N(TMS)2)3 21.2 g, with a yield of 90% and a purity of 98%.

[0049] The NMR spectrum of the intermediate product La(N(TMS)2) is as follows: Figure 2 As shown, the NMR results are: 1 HNMR (400 MHz, C6D6): δ (ppm) = 0.28 (54H, -CH3).

[0050] (3) Take La(N(TMS)2) (24.8g, 0.04mol) into reaction flask 3, weigh N,N'-diisopropylformamidin (15.38g, 0.12mol) into reaction flask 4, add toluene to dissolve, transfer the solution from reaction flask 4 to reaction flask 3, heat at 110℃ for 2h, after desolvation, sublimate at 140℃ under reduced pressure for 2 torr to obtain La(ipr2-FMD)3 17.69g, yield 85%, purity 92%, dimer content 7%.

[0051] Product NMR spectrum as follows Figure 3As shown, the NMR values ​​of the product were δ (ppm) = 8.08 (3H, -CH-), 3.16, 3.18, 3.19, 3.21, 3.23 (6H, -CH(CH3)2), 1.21, 1.23 (36H, -CH3); the values ​​of the dimer impurities were δ (ppm) = 8.3, 8.63 (3H, -CH-), 3.8, 3.53 (6H, -CH(CH3)2), 1.53, 1.52 (36H, -CH3). It is evident that the method in Comparative Example 1 prepared tris(N,N'-diisopropylformamido)lanthanum with poor purity and a high concentration of dimers.

[0052] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for preparing lanthanum complexes, precursors of ALD, characterized in that, Includes the following steps: S1. Lanthanum chloride tetrahydrofuran complex LaCl3·xTHF and hexamethyldisilazane metal salt MN(SiMe3)2 are mixed and reacted to obtain intermediate 1; wherein, M is a monovalent metal; S2. The intermediate 1 and N,N'-diisopropylformamidinium lithium (iPrNC=NiPr) are mixed and reacted to obtain intermediate 2; S3. The intermediate 2 is mixed and reacted with N,N'-diisopropylformamidinium to obtain the ALD precursor lanthanum complex tris(N,N'-diisopropylformamido)lanthanum.

2. The method for preparing the lanthanum complex, a precursor of ALD, as described in claim 1, is characterized in that, The molar ratio of the lanthanum chloride tetrahydrofuran complex, hexamethyldisilazane potassium salt, N,N'-diisopropylformamidinium lithium, and N,N'-diisopropylformamidinium is 1:(0.9-1.1):(1.9-2.1):(0.9-1.1).

3. The method for preparing the lanthanum complex, a precursor of ALD, as described in claim 1, is characterized in that, The reaction temperature for S1-S3 is 100-120℃.

4. The method for preparing the lanthanum complex, a precursor of ALD, as described in claim 1, is characterized in that, The method for preparing the N,N'-diisopropylformamidinium lithium is as follows: N,N'-diisopropylformamidinium is mixed and reacted with n-butyllithium to obtain the N,N'-diisopropylformamidinium lithium.

5. The method for preparing the lanthanum complex, a precursor of ALD, as described in claim 1, is characterized in that, The reaction temperature of the mixture of N,N,-diisopropylformamidinium and n-butyllithium is -35℃ to -25℃.

6. The method for preparing the lanthanum complex, a precursor of ALD, as described in claim 1, is characterized in that, The molar ratio of N,N,-diisopropylformamidinium to n-butyllithium is 1:(0.9-1.1).

7. The method for preparing the lanthanum complex, a precursor of ALD, as described in claim 1, is characterized in that, The method for preparing the lanthanum chloride tetrahydrofuran complex is as follows: lanthanum chloride and tetrahydrofuran are mixed and heated, and the solution is removed under reduced pressure to obtain the lanthanum chloride tetrahydrofuran complex.

8. The method for preparing the lanthanum complex, a precursor of ALD, as described in claim 1, is characterized in that, The lanthanum chloride and tetrahydrofuran mixture is heated at a temperature of 65-75°C.

9. The method for preparing the lanthanum complex of the ALD precursor as described in claim 1, characterized in that, In the LaCl3·xTHF, x = 1-1.

5.

10. The method for preparing the lanthanum complex, a precursor of ALD, as described in claim 1, is characterized in that, The metal of the hexamethyldisilazane metal salt is Li, K or Na.

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