Preparation method of tris (dimethylamino) cyclopentadienyl hafnium

Abstract

According to the preparation method of the tris (dimethylamino) cyclopentadienyl hafnium provided by the invention, the tris (dimethylamino) cyclopentadienyl hafnium is prepared by adopting the method disclosed by the invention, a better yield can be obtained, and a colorless and transparent product with high purity can be obtained. The preparation method comprises the following steps: S1, reacting an n-hexane solution of n-butyllithium with dimethylamine to obtain a lithium dimethylamino emulsion; s2, dropwise adding the lithium dimethylamino emulsion into a suspension containing hafnium tetrachloride, and stirring for reaction; filtering reaction feed liquid obtained by the reaction, performing vacuum concentration on filtrate to obtain concentrate, and sublimating the concentrate at the temperature of between 0.05 and 0.30 torr and the temperature of between 60 and 70 DEG C to obtain tetra (dimethylamino) hafnium; s3, the tetra (dimethylamino) hafnium and cyclopentadiene are subjected to a contact reaction, and a reaction solution is obtained; and carrying out vacuum concentration on the reaction liquid, and then distilling under the conditions that the pressure is less than 0.15 torr and the heating temperature is 70-80 DEG C to obtain the tris (dimethylamino) cyclopentadienyl hafnium.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of organometallic chemistry and high-end electronic material preparation technology, and particularly relates to a preparation method of tris(dimethylamino)cyclopentadienyl hafnium. BACKGROUND

[0002] With the continuous miniaturization of semiconductor devices, the traditional SiO2 gate dielectric layer cannot meet the demand due to the sharp increase in leakage current caused by quantum tunneling effect. HfO2, a high-k dielectric material, can achieve the required equivalent oxide thickness (EOT) at a thinner physical thickness due to its high dielectric constant, and has become a key material for replacing SiO2. Atomic layer deposition (ALD) technology is widely used for depositing HfO2 thin films due to its excellent film uniformity and thickness control capability. The performance (such as purity, volatility, and thermal stability) of the metal organic precursor used in the ALD process directly determines the quality and electrical properties of the thin film.

[0003] Cp-Hf(NMe2)3 combines the stability of cyclopentadienyl ligand and the high reactivity of dimethylamino ligand, and has characteristics such as high volatility, suitable thermal decomposition temperature, and low impurity content, making it an ideal high-k thin film deposition precursor.

[0004] Typical synthesis methods of tris(dimethylamino)cyclopentadienyl hafnium mostly use hafnium tetrachloride and dimethylamino lithium (LiNMe2) to react to form an intermediate, and then undergo coordination reaction with cyclopentadiene. However, the existing methods have some problems, such as: 1) complex process: as described in CN112062792A, an ionic liquid buffer solvent with complex composition is used, which has high cost and causes environmental pollution; 2) low yield and purity: the yield of existing methods is generally about 60%, and the carbon and chlorine impurity content is high; 3) poor safety: a large amount of flammable butane gas is produced during the synthesis process, and the reaction is exothermic, which may cause material overflow.

[0005] Chinese patent application CN119684373A entitled "Tris(dimethylamino)cyclopentadienyl hafnium and its preparation process" discloses a preparation process. In this technical solution, n-hexane is used as a single solvent, dimethylamino lithium is generated by reacting n-butyl lithium with dimethylamine, and then reacts with hafnium tetrachloride to generate a hafnium tetrakis(dimethylamino) concentrate, which finally reacts with cyclopentadiene to obtain the target product. The product purity and yield (about 65%) of this method still have room for improvement, and the economic value of the reactants cannot be fully realized, and there is a safety risk when the process is scaled up. SUMMARY

[0006] In view of at least one deficiency of the prior art, the present application provides a preparation method of tris(dimethylamino) cyclopentadienyl hafnium, which can obtain a better yield and a colorless transparent product with high purity.

[0007] To achieve the purpose, the present application provides the following technical solutions: The present application provides a preparation method of tris(dimethylamino) cyclopentadienyl hafnium, comprising the following steps: S1, reacting n-butyllithium n-hexane solution and dimethylamine to obtain dimethylamino lithium emulsion; S2, adding the dimethylamino lithium emulsion into a suspension containing hafnium tetrachloride, stirring and reacting; filtering the reaction liquid obtained by the reaction, concentrating the filtrate under reduced pressure to obtain a concentrate, and sublimating the concentrate at 0.05 ~ 0.30 torr and 60-70℃ to obtain tetrakis(dimethylamino) hafnium; S3, contacting the tetrakis(dimethylamino) hafnium with cyclopentadiene to obtain a reaction liquid; concentrating the reaction liquid under reduced pressure, and then distilling under the condition of pressure <0.15 torr and heating temperature of 70-80℃ to obtain the tris(dimethylamino) cyclopentadienyl hafnium.

[0008] Preferably, in step S1, the dimethylamine is fed in the form of a solution, and the n-butyllithium n-hexane solution is added dropwise into the dimethylamine solution at a temperature of-78℃ to-30℃ for reaction; In step S2, the dimethylamino lithium emulsion is added dropwise into the suspension containing hafnium tetrachloride at a temperature of-78℃ to-30℃; In step S3, the tetrakis(dimethylamino) hafnium is fed in the form of a tetrakis(dimethylamino) hafnium solution, and the cyclopentadiene is added dropwise into the tetrakis(dimethylamino) hafnium solution at a temperature of-78℃ to 0℃ for contacting reaction.

[0009] Preferably, in step S1, the solvent in the dimethylamine solution is THF; And / or, in step S2, the solvent used in the suspension containing hafnium tetrachloride is one or more of tetrahydrofuran, n-hexane, toluene and diethyl ether, preferably n-hexane; And / or, in step S3, the solvent in the tetrakis(dimethylamino) hafnium solution is one or more of tetrahydrofuran, n-hexane, toluene and diethyl ether, preferably n-hexane; And / or, in step S1, the concentration of the dimethylamine solution is 1.0-3.0 mol / L; and the concentration of the n-butyllithium n-hexane solution is 1.0-4.0 mol / L; And / or, in the step S2, the concentration of the hafnium tetrachloride in the hafnium tetrachloride-containing suspension is 0.08-0.80 mol / L. And / or, in the step S3, the concentration of the hafnium tetrakis(dimethylamide) solution is 0.05-0.50 mol / L.

[0010] Preferably, in the step S1, after the dropwise addition of the n-butyllithium hexane solution is completed, the reaction is stirred at -78℃ to -30℃, preferably for 0.5-3h; and then the reaction is stirred at room temperature, preferably for 0.5-3h.

[0011] Preferably, in the step S2, after the dropwise addition of the lithium dimethylamide emulsion is completed, the reaction is stirred at -78℃ to -30℃, preferably for 0.5-3h; and then the reaction is stirred at a temperature ≥0℃ and <60℃, preferably for 10h or more.

[0012] Preferably, in the step S3, after the dropwise addition of the cyclopentadiene is completed, the reaction is stirred at -78℃ to 0℃, preferably for 0.5-3h; and then the reaction is stirred after the temperature is raised, and the reaction is refluxed when the temperature is raised to 45-60℃, preferably for 10h or more.

[0013] Preferably, the molar ratio of the n-butyllithium to the dimethylamine is 1:1.1-1.6; And / or, the molar ratio of the n-butyllithium to the hafnium tetrachloride is 3.8-4.2:1; And / or, the molar ratio of the cyclopentadiene to the hafnium tetrakis(dimethylamide) is 1.10-1.30:1.

[0014] Preferably, in the step S3, the cyclopentadiene is prepared on site; preferably, the cyclopentadiene is obtained by collecting after thermal cracking and condensation of dicyclopentadiene.

[0015] Further, the steps S1 to S3 are all carried out under inert gas protection.

[0016] In some examples, the inert gas is one or more of nitrogen, argon, and helium.

[0017] The technical solution provided by the present application has the following beneficial effects: The preparation method provided by the present application can significantly improve the yield of hafnium tris(dimethylamide) cyclopentadienyl, and at the same time, a colorless transparent liquid product with better product purity can be obtained; moreover, the method has better reaction controllability and process safety, and is easy to carry out process amplification safely and well. DETAILED DESCRIPTION

[0018] For the convenience of understanding the present application, the present application will be further described below in conjunction with examples. It should be understood that the following examples are only for better understanding the present application, and do not mean that the present application is limited to the following examples only.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The term "and / or", where used herein, includes any and all combinations of one or more of the associated listed items.

[0020] The present application provides a preparation method of tris(dimethylamino)cyclopentadienyl hafnium, comprising the following steps: S1, reacting a n-hexane solution of n-butyllithium (n-BuLi) and dimethylamine (DMA) to obtain a dimethylamino lithium emulsion, and safely discharging butane gas; S2, adding the dimethylamino lithium emulsion dropwise to a suspension containing hafnium tetrachloride, and stirring to react; filtering the reaction liquid obtained by the reaction to remove LiCl, and concentrating the filtrate under reduced pressure to obtain a concentrate to remove the solvent, the obtained concentrate being a viscous oil or a solid concentrate, the reduced pressure concentration being performed, for example, at 35-45°C, 30-100 mbar (about 22-75 Torr); Subliming the concentrate at 0.05 ~ 0.30 torr (for example, 0.05, 0.10, 0.20, 0.30 torr, etc.), 60-70°C (for example, 60, 65, 70°C, etc.) to obtain white crystalline high-purity hafnium tetrakis(dimethylamide) ((Hf(NMe2)4)); S3, contacting the hafnium tetrakis(dimethylamide) with cyclopentadiene to obtain a reaction liquid; concentrating the reaction liquid under reduced pressure to remove the solvent and excess cyclopentadiene, the reduced pressure concentration being performed, for example, at 25-35°C, 10-50 mbar (about 7.5-37.5 Torr); and then distilling under the condition of pressure < 0.15 torr (for example, 0.05-0.10 torr) and heating temperature of 70-80°C (for example, 70, 75, 80°C, etc.) to obtain the tris(dimethylamino)cyclopentadienyl hafnium (Cp-Hf(NMe2)3); specifically, during the distillation, the target product is obtained by collecting the 60-65°C fraction.

[0021] The preparation method provided by the present application, in step S2, the reaction is carried out by adding the lithium dimethylamide emulsion to the suspension containing hafnium tetrachloride, and the reaction product is sublimated at 0.05-0.30 torr and 60-70°C, and in step S3, the product is purified by high vacuum distillation under the condition of <0.15 torr and a heating temperature of 70-80°C, so that the purity and yield of hafnium tris(dimethylamide) cyclopentadienyl can be significantly improved by the method of the present application.

[0022] In step S2 of the present application, the reaction product is sublimated at 0.05-0.30 torr and 60-70°C, under which condition, (Hf(NMe2)4) has a certain volatility, while the by-product LiCl and possible high polymer impurities do not volatilize under this condition. By sublimation under the above condition, the ionic impurity LiCl can be almost completely separated, which fundamentally avoids the introduction of LiCl + into the subsequent reaction, which can significantly improve the yield and purity of the finally prepared hafnium tris(dimethylamide) cyclopentadienyl. Further, in step S3 of the present application, the reaction liquid is concentrated under reduced pressure to remove the solvent and excess cyclopentadiene (CPD), and then the crude product is subjected to high vacuum distillation under the condition of a pressure of <0.15 torr and a heating temperature of 70-80°C. Under this condition, the purification of the crude product can not only effectively remove impurities, but also effectively avoid the thermal decomposition of the target product (thermal decomposition temperature is about 100°C), which is helpful to obtain a product with high yield and purity. In step S2 of the present application, the feeding / reaction method of adding the lithium dimethylamide emulsion to the suspension containing hafnium tetrachloride is used, compared with the feeding / reaction method of adding the hafnium tetrachloride solid to the lithium dimethylamide emulsion in batches in the prior art: on the one hand, the feeding process does not need to open the reaction related containers / equipment for many times, which can greatly reduce the introduction of water and oxygen in the air during the feeding process, which is beneficial to reduce the occurrence of side reactions; on the other hand, such feeding method makes the reactants contact more fully, which is beneficial to improve the reaction efficiency and yield.

[0023] Preferably, in step S1, dimethylamine is fed in the form of a solution, for example dimethylamine solution prepared with a solvent, or commercially available dimethylamine solution, for example commercially available 2.0 mol / L dimethylamine THF solution; the reaction is carried out by slowly dropping the n-butyllithium n-hexane solution into the dimethylamine solution at a temperature of -78 to -30°C; in step S2, the lithium dimethylamide emulsion is slowly dropped into the suspension containing hafnium tetrachloride at a temperature of -78 to -30°C; in step S3, the tetrakis(dimethylamino)hafnium is fed in the form of a tetrakis(dimethylamino)hafnium solution, and the cyclopentadiene is slowly dropped into the tetrakis(dimethylamino)hafnium solution at -78 to 0°C to contact and react. In this preferred manner, the feeding of each stage is carried out under the above-mentioned specific temperature conditions, and the dropping feeding is carried out according to the above-mentioned feeding order. The temperature in the feeding step involving the reaction stage of each nucleophile (n-BuLi, LiNMe2, CPD) is strictly controlled, the material is slowly dropped at the above-mentioned low temperature, which can effectively control the heat release of the reaction, avoid the risk of violent side reactions and material overflow caused by local high concentration during the reaction process, solve the safety hidden danger of scale-up production, and also help to improve the yield and purity; using this preferred process, the safety of the process can be effectively improved, and the process scale-up can also be safely and well carried out. The inventors have found that the order of material addition in steps S1, S2 and S3 is crucial to the control of the reaction, safety and purity of the final product; if the reverse dropping method is used, for example, the hafnium tetrachloride suspension is dropped into the lithium dimethylamide emulsion, or the tetrakis(dimethylamino)hafnium solution is dropped into the cyclopentadiene, a serious risk of material overflow will be caused by the local instantaneous heat release, and the generation of impurities such as dicyclopentadienyl by-products will be significantly aggravated, resulting in a significant decrease in yield and purity. The preferred dropping order used in the present application effectively ensures the controllability of the reaction and the safety of the process by slowly introducing the nucleophile with higher activity into the electrophilic substrate, which is one of the keys to achieving high purity and high yield.

[0024] In some embodiments, in step S1, the dimethylamine solution can use solvents and feeding concentrations commonly used in the art, for example, the solvent is THF (tetrahydrofuran) or the like, and the dimethylamine solution can be self-prepared or commercially available, for example, commercially available 2 mol / L dimethylamine THF solution, which is not particularly limited.

[0025] In some embodiments, in step S2, the solvent used in the suspension containing hafnium tetrachloride is one or more of n-hexane, tetrahydrofuran, toluene and diethyl ether, preferably n-hexane; In some embodiments, in step S3, the solvent in the tetrakis(dimethylamino)hafnium solution is one or more of n-hexane, tetrahydrofuran, toluene and diethyl ether, preferably n-hexane; The dimethylamine solution, the n-butyllithium solution in n-hexane, the hafnium tetrakis(dimethylamide) solution, etc. can be fed at a concentration level common in the art, and there is no particular limitation thereto. In some embodiments, in step S1, the concentration of the dimethylamine solution is 1.0-3.0 mol / L, such as 1.0, 2.0, 3.0 mol / L, etc.; the concentration of the n-butyllithium solution in n-hexane is 1.0-4.0 mol / L, such as 1.0, 2.0, 3.0, 4.0 mol / L, etc.; in some embodiments, in step S2, the concentration of hafnium tetrachloride in the suspension containing hafnium tetrachloride is 0.08-0.80 mol / L, such as 0.08, 0.10, 0.30, 0.50, 0.80 mol / L, etc.; in some embodiments, in step S3, the concentration of the hafnium tetrakis(dimethylamide) solution is 0.05-0.50 mol / L, such as 0.05, 0.10, 0.20, 0.30, 0.40, 0.50 mol / L, etc.

[0026] Preferably, in step S1, after the n-butyllithium solution in n-hexane is completed, the reaction is stirred at -78°C to -30°C (such as -78, -60, -50, -40, -30°C, etc.) for 0.5-3h (such as 0.5, 1, 2, 3h, etc.); then the temperature is raised to room temperature (such as 20-25°C) and the reaction is stirred for 0.5-3h (such as 0.5, 1, 2, 3h, etc.).

[0027] Preferably, in step S2, after the dimethylamino lithium emulsion is completed, the reaction is stirred at -78°C to -30°C (such as -78, -60, -50, -40, -30°C, etc.) for 0.5-3h; then the temperature is raised to a temperature of ≥0°C and <60°C and the reaction is stirred, preferably for 10h or more, such as 10, 15, 20, 24h, etc.

[0028] Preferably, in step S3, after the cyclopentadiene is completed, the reaction is stirred at -78°C to 0°C (such as -78, -60, -50, -40, -30, -20, -10, 0°C, etc.) for 0.5-3h (such as 0.5, 1, 2, 3h, etc.), then the temperature is raised and stirred, and when the temperature is raised to 45-60°C (such as 45, 50, 55, 60°C, etc.), the reaction is refluxed, preferably for 10h or more, such as 10, 15, 20, 24h, etc.

[0029] Preferably, the molar ratio of the n-butyllithium to the dimethylamine is 1:1.1-1.6; Preferably, the molar ratio of the n-butyllithium to the hafnium tetrachloride is 3.8-4.2:1; Preferably, the molar ratio of the cyclopentadiene and the hafnium tetrakis(dimethylamide) is 1.10-1.30:1.

[0030] Preferably, in step S3, the cyclopentadiene is prepared on site, i.e. fresh cyclopentadiene is used. The preparation technique of the cyclopentadiene can use a process known in the art, which is not particularly limited. Preferably, the cyclopentadiene is obtained by pyrolysis of dicyclopentadiene and collection after condensation; wherein the pyrolysis temperature is 170-200°C; during the condensation process, for example, an air condenser can be used to avoid pipe blockage caused by water cooling, and the condensation temperature is <-20°C; a low-temperature receiving bottle (-20°C or below) can be used for collection; on-site preparation can ensure high reactivity of the ligand, and reduce the measurement error and side reactions caused by storage of dicyclopentadiene; the cyclopentadiene used in the examples hereinafter is fresh cyclopentadiene obtained in this way, which will not be described hereinafter.

[0031] Further, steps S1 to S3 are all carried out under inert gas protection, which is one or more of nitrogen, argon, and helium.

[0032] The tris(dimethylamide) hafnium cyclopentadienyl prepared by the method of the present application has a high yield, and can obtain a colorless transparent liquid product with high purity; at the same time, the present application can effectively ensure the controllability of the reaction and the safety of the process, and is easy to carry out process scale-up safely and well.

[0033] The solutions of the present application will be further described below through examples, but should not be understood as limiting the present application to them.

[0034] In the examples, if the specific experimental steps or conditions are not specified, the corresponding conventional experimental steps can be operated according to the operation or conditions in the technical field. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be obtained by market purchase.

[0035] Example 1: (laboratory gram-scale) In this example, the molar ratio of n-butyllithium and dimethylamine is 1:1.2, the molar ratio of n-butyllithium and hafnium tetrachloride is 4.0:1, and the molar ratio of cyclopentadiene and hafnium tetrakis(dimethylamide) is 1.2:1.

[0036] S1: Preparation of LiNMe2 Under nitrogen protection, 124.9 mL n-BuLi solution (2.5 mol / L) in n-hexane was slowly added to 187.3 mL DMA solution (2 mol / L) in THF at -78°C. After the addition was completed, it was stirred at -78°C for 1 h, and then it was stirred at room temperature for 2 h. The butane gas generated in the reaction was safely discharged; a LiNMe2 emulsion was obtained.

[0037] S2: Preparation and purification of Hf(NMe2)4 In a glove box, 25 g of HfCl4 was taken into a flask and suspended in 500 mL of n-hexane to obtain a n-hexane suspension of HfCl4. The above-mentioned LiNMe2 emulsion obtained in step S1 was slowly added dropwise to the suspension at -78°C. After the dropwise addition was completed, stirring was carried out at -78°C for 1 h, and then the temperature was slowly increased to 45°C and stirring was carried out for 24 h. The obtained reaction solution was filtered to remove LiCl; the obtained filtrate was concentrated under reduced pressure at 40°C and 50 mbar to remove the solvents n-hexane and THF, to obtain a crude product. The crude product was sublimed at 0.2 torr and 65°C to obtain white crystalline high-purity Hf(NMe2)4.

[0038] S3: Preparation of Cp-Hf(NMe2)3 In a glove box, 25 g of Hf(NMe2)4 obtained in step S2 was dissolved in 780 mL of n-hexane (concentration: 0.09 mol / L) and cooled in an ice water bath (0°C). Freshly prepared cyclopentadiene 6.95 mL was slowly added dropwise. After the dropwise addition was completed, stirring was carried out at 0°C for 1 h, the ice water bath was removed, the temperature was slowly increased to room temperature and stirring was carried out, and then the temperature was increased to 50°C and refluxed for 24 h. The obtained reaction solution was concentrated under reduced pressure at 30°C and 40 mbar to remove the solvents and excess CPD, to obtain a crude product. The crude product was subjected to high vacuum distillation at <0.1 torr and a heating temperature of 76°C, and a fraction segment of 60-65°C was collected, to obtain tris(dimethylamino)cyclopentadienyl hafnium.

[0039] Yield and characterization: a colorless transparent liquid product was obtained, with a yield of 82%. 1H NMR (400 MHz, C6D6): δ 6.04 (s, 5H, Cp-H), 2.96 (s, 18H, N(CH3)2).

[0040] Example 2: (hundred gram scale) Reference is made to Example 1, except that: All materials in Example 1 were scaled up by 5 times.

[0041] The sublimation conditions of step S2 were: 0.2 torr, 68°C.

[0042] The high vacuum distillation conditions of step S3 were: <0.1 torr, heating temperature of 78°C.

[0043] Result: a colorless transparent liquid product was obtained as the final product, with a yield of 80%. The 1H NMR spectrum was consistent with that of Example 1, and the purity was excellent.

[0044] Example 3 In this example, the molar ratio of n-butyllithium and dimethylamine is 1:1.1, the molar ratio of n-butyllithium and hafnium tetrachloride is 4.1:1, and the molar ratio of cyclopentadiene and tetrakis(dimethylamido)hafnium is approximately 1.18:1.

[0045] S1: Preparation of LiNMe2 Under nitrogen protection, 128 mL of n-BuLi n-hexane solution (2.5 mol / L) was slowly added dropwise into a THF solution (2 mol / L) of 176 mL of DMA at -70°C. After the addition was completed, it was stirred at -70°C for 1.5 h, and then it was stirred at room temperature for 2 h. The butane gas generated by the reaction was safely discharged; a LiNMe2 emulsion was obtained.

[0046] S2: Preparation and purification of Hf(NMe2)4 In the glove box, 25 g of HfCl4 was placed in a flask and suspended in 400 mL of n-hexane to obtain a suspension. The above-mentioned LiNMe2 emulsion obtained in step S1 was slowly added dropwise into the suspension at -70°C. After the addition was completed, it was stirred at -70°C for 1 h, and then it was slowly warmed to 50°C and stirred for 20 h. The obtained reaction liquid was filtered to remove LiCl; the obtained filtrate was concentrated under reduced pressure at 45°C and 60 mbar to obtain a crude product. The crude product was sublimed at 0.15 torr (about 20 mbar) and 68°C to obtain white crystalline high-purity Hf(NMe2)4.

[0047] S3: Preparation of Cp-Hf(NMe2)3 In the glove box, 25 g of HfCl4 was placed in a flask and suspended in 400 mL of n-hexane to obtain a suspension. The above-mentioned LiNMe2 emulsion obtained in step S1 was slowly added dropwise into the suspension at -70°C. After the addition was completed, it was stirred at -70°C for 1 h, and then it was slowly warmed to 50°C and stirred for 20 h. The obtained reaction liquid was filtered to remove LiCl; the obtained filtrate was concentrated under reduced pressure at 45°C and 60 mbar to obtain a crude product. The crude product was sublimed at 0.15 torr (about 20 mbar) and 68°C to obtain white crystalline high-purity Hf(NMe2)4.

[0048] Result: The final product obtained was a colorless transparent liquid product with a yield of 78%. 1H NMR (400 MHz, C6D6): δ 6.04 (s, 5H, Cp-H), 2.96 (s, 18H, N(CH3)2). The purity was comparable to that of Example 1.

[0049] Example 4 In this example, the molar ratio of n-BuLi to dimethylamine was 1 : 1.30, the molar ratio of n-BuLi to hafnium tetrachloride was 3.90: 1, and the molar ratio of cyclopentadiene to tetrakis(dimethylamido)hafnium was approximately 1.28: 1.

[0050] S1: Preparation of LiNMe2 Under nitrogen protection, 124.2 mL of n-BuLi n-hexane solution (2.5 mol / L) was slowly added dropwise to a THF solution (2 mol / L) of 152 mL of DMA at -65 °C. After the addition was complete, stirring was carried out at -65 °C for 1 h, and then the temperature was raised to room temperature and stirring was carried out for 3 h. The butane gas generated by the reaction was safely discharged; a LiNMe2 emulsion was obtained.

[0051] S2: Preparation and purification of Hf(NMe2)4 In a glove box, 25 g of HfCl4 was placed in a flask and suspended in 600 mL of n-hexane to obtain a suspension. The above LiNMe2 emulsion obtained in step S1 was slowly added dropwise to the suspension at -65 °C. After the addition was complete, stirring was carried out at -65 °C for 1 h, and then the temperature was slowly raised to 57 °C and stirring was carried out for 22 h. The reaction liquid obtained was filtered to remove LiCl; the filtrate was concentrated under reduced pressure at 45 °C and 80 mbar to obtain a crude product. The crude product was sublimed at 0.25 torr (approximately 33 mbar) and 62 °C to obtain white crystalline high-purity Hf(NMe2)4.

[0052] S3: Preparation of Cp-Hf(NMe2)3 In a glove box, 25 g of Hf(NMe2)4 obtained in step S2 was dissolved in 195.5 mL of n-hexane (concentration: approximately 0.36 mol / L) and cooled to -65 °C. Fresh cyclopentadiene 7.4 mL (molar ratio CPD:Hf(NMe2)4≈1.28:1) was slowly added dropwise. After the addition was complete, stirring was carried out at -65 °C for 1 h, the temperature was slowly and naturally raised to room temperature, and stirring was carried out, after which the temperature was raised to 52 °C and refluxing was carried out for 22 h. The reaction liquid obtained was concentrated under reduced pressure at 35 °C and 50 mbar to remove the solvent and excess CPD, and a crude product was obtained. The crude product was subjected to high-vacuum distillation at <0.12 torr (approximately <0.16 mbar) and a heating temperature of 78 °C, and a fraction segment at 60-65 °C was collected to obtain tris(dimethylamido)cyclopentadienylhafnium.

[0053] Result: The final product was a colorless transparent liquid with a yield of 76%. 1H NMR (400 MHz, C6D6): δ 6.04 (s, 5H, Cp-H), 2.96 (s, 18H, N(CH3)2). The purity was comparable to Example 1.

[0054] Comparative Example 1 Reference was made to Example 1, except that: In Step S2, the sublimation of the crude product was omitted, and the crude product obtained by vacuum concentration was directly used for the reaction in Step S3. The rest of the operations and conditions were the same as in Example 1.

[0055] Result: The final product was a light yellow liquid with a significantly reduced yield of 45%. The 1H NMR spectrum (400 MHz, C6D6) showed that, in addition to the characteristic peaks of the target product (δ ~ 6.04, 2.96), there were obvious unknown impurity peaks at δ ~ 2.80 and ~ 6.20. Through inductively coupled plasma mass spectrometry (ICP-MS) analysis, the lithium (Li + ) impurity content in the product was as high as ~ 120 ppb, and the chlorine (Cl -) ) impurity content was ~ 85 ppb.

[0056] In the 1H NMR spectrum of the final product obtained in Examples 1-4, in addition to the characteristic peaks of the target product, there were no obvious unknown impurity peaks; in the ICP-MS analysis, the lithium (Li + ) impurity content in the product was < 10 ppb, and the chlorine (Cl -) ) impurity content was < 10 ppb.

[0057] Conclusion: Omitting the sublimation purification step of the intermediate Hf(NMe2)4 will result in the inability to effectively remove the impurities (including LiCl) generated by side reactions. These impurities not only reduce the yield, but more seriously, are brought into the final product, leading to a significant decrease in purity, which cannot meet the requirements of high-end semiconductor processes for precursor purity.

[0058] Comparative Example 2 Reference was made to Example 1, except that: In Step S3, the conditions for high vacuum distillation were changed to 0.5 torr, and the heating temperature was 95°C.

[0059] Result: A dark colored viscous liquid was finally obtained with a yield of 55%. This indicates that the product undergoes significant decomposition at higher temperatures; 1 the HNMR spectrum baseline is raised, and a broad peak appears in the range of δ 1.5-2.0, indicating that the product has undergone significant thermal decomposition to generate polymerization products and other decomposition products.

[0060] Conclusion: Distillation at higher pressure (0.5 torr) and temperature (95 °C) leads to thermal decomposition of the target product Cp-Hf(NMe2)3. This not only results in a lower yield, but also causes fundamental changes in the color, viscosity and composition of the product, which loses its value as a high-purity precursor.

[0061] Comparative Example 3 Reference to Example 1 was made, except that the addition of the materials was changed in Step S2, specifically, the HfCl4 suspension in n-hexane was slowly added dropwise to the above LiNMe2 emulsion obtained in Step S1.

[0062] Result: During the dropwise addition in Step S2, a strong instantaneous heat release was observed, accompanied by the generation of a large amount of white smoke. The final product was a dark yellow liquid, and the yield was greatly reduced to 58%. 1 The H NMR spectrum showed clear characteristic peaks of bis(cyclopentadienyl)bis(dimethylamino)hafnium (Cp2Hf(NMe2)2) at δ 6.30 (s, 10H) and 2.92 (s, 12H), indicating that the side reaction was intensified.

[0063] Conclusion: The reverse feeding method of adding hafnium chloride suspension to lithium dimethylamide emulsion can cause local instantaneous concentration and temperature to be too high. This not only brings serious safety hazards (risk of material overflow), but more importantly, it leads to the loss of reaction selectivity, generating a large amount of non-target dicyclopentadienyl byproducts, thereby significantly reducing the yield and purity of the target product Cp-Hf(NMe2)3.

[0064] Comparative Example 4 Reference to Example 1 was made, except that: In Step S1, the dropwise addition was carried out at -20 °C to -10 °C, and after the dropwise addition was completed, stirring was carried out at -20 °C to -10 °C for 1 h, and then the temperature was raised to room temperature and stirring was carried out for 2 h; In Step S2, the dropwise addition was carried out at -20 °C to -10 °C, and after the dropwise addition was completed, stirring was carried out at -20 °C to -10 °C for 1 h, and then subsequent temperature raising and other operations were carried out.

[0065] Result: During the dropwise addition in Steps S1 and S2, the temperature of the reaction liquid fluctuated significantly, accompanied by a mild heat release phenomenon. The final product was a yellow liquid, and the yield was about 60%. 1H NMR showed a small amount of unknown impurity peaks, and the color of the product indicated that some oxidation or thermal degradation products were generated.

[0066] Conclusion: Increasing the dropwise addition and initial reaction temperature from -78°C to -30°C to -20 to -10°C in steps S1 and S2 makes it difficult to effectively suppress side reactions. This shows that the deep low-temperature control (-78°C to -30°C) of the present application is essential for achieving a highly selective reaction, avoiding the formation of by-products, and ensuring the color of the product.

[0067] Characterization data and effect data of the products of the examples and comparative examples: Application effect data (ALD deposition of HfO2 thin film): The tris(dimethylamino)cyclopentadienyl hafnium obtained in Example 1 and the tris(dimethylamino)cyclopentadienyl hafnium of Comparative Example 1 were respectively used as precursors to deposit HfO2 thin films at 300°C with O3 as the oxidant.

[0068] Thin film growth rate (GPC): 0.85 Å / cycle for the precursor of Example 1; 0.72 Å / cycle for the precursor of Comparative Example 1.

[0069] Thin film carbon content: Elemental analysis of the thin film by X-ray photoelectron spectroscopy (XPS) showed that the HfO2 thin film prepared using the precursor described in Example 1 had a carbon residual content of less than 0.5 at%; while the thin film prepared using the precursor described in Comparative Example 1 (without sublimation purification) had a carbon residual content of about 1.8 at%. This significant difference confirms that the intermediate impurities (such as carbon-containing polymers or incompletely reacted ligands) effectively removed by the sublimation step of the present application are one of the main sources of carbon contamination in the thin film.

[0070] Electrical performance (MOS capacitance): The leakage current density of the thin film prepared in Example 1 was an order of magnitude lower than that of the thin film prepared in Comparative Example 1.

[0071] The above application was investigated for Examples 2-4, and equivalent experimental results to Example 1 were obtained.

[0072] It is easily understood that the above examples are merely illustrative and are not intended to limit the present application. Based on the above description, other different forms of changes or variations can be made by those of ordinary skill in the art. Here, it is not necessary or possible to exhaust all embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A process for the preparation of tris(dimethylamino)cyclopentadienyl hafnium, characterized in that, The method comprises the following steps: S1, reacting n-butyllithium n-hexane solution and dimethylamine to obtain dimethylamine lithium emulsion; S2, adding the dimethylamine lithium emulsion into a suspension containing hafnium tetrachloride, and stirring to react; filtering the reaction solution obtained in the reaction, and concentrating the filtrate under reduced pressure to obtain a concentrate; sublimating the concentrate at 0.05-0.30 torr and 60-70℃ to obtain tetra(dimethylamine)hafnium; S3, contacting the tetra(dimethylamine)hafnium with cyclopentadiene to obtain a reaction solution; concentrating the reaction solution under reduced pressure, and then distilling under the condition of pressure <0.15 torr and heating temperature of 70-80℃ to obtain the tris(dimethylamine)cyclopentadienylhafnium.

2. The preparation method according to claim 1, wherein in step S1, the dimethylamine is fed in the form of a solution, and the n-butyllithium n-hexane solution is added dropwise into the dimethylamine solution at a temperature of-78℃ to-30℃ for reaction; in step S2, the dimethylamine lithium emulsion is added dropwise into the suspension containing hafnium tetrachloride at a temperature of-78℃ to-30℃; in step S3, the tetra(dimethylamine)hafnium is fed in the form of a solution, and the cyclopentadiene is added dropwise into the tetra(dimethylamine)hafnium solution at a temperature of-78℃ to 0℃ for contacting reaction. in step S1, the solvent in the dimethylamine solution is THF; 3. The preparation method according to claim 2, characterized in that, and / or, in step S2, the solvent used in the suspension containing hafnium tetrachloride is one or more of tetrahydrofuran, n-hexane, toluene and diethyl ether, preferably n-hexane; and / or, in step S3, the solvent in the tetra(dimethylamine)hafnium solution is one or more of tetrahydrofuran, n-hexane, toluene and diethyl ether, preferably n-hexane; and / or, in step S1, the concentration of the dimethylamine solution is 1.0-3.0 mol / L; and the concentration of the n-butyllithium n-hexane solution is 1.0-4.0 mol / L; and / or, in step S2, the concentration of hafnium tetrachloride in the suspension containing hafnium tetrachloride is 0.08-0.80 mol / L; and / or, in step S3, the concentration of the tetra(dimethylamine)hafnium solution is 0.05-0.50 mol / L. in step S1, after the n-butyllithium n-hexane solution is added dropwise, the reaction is carried out at-78℃ to-30℃, preferably for 0.5-3h; and then the reaction is carried out at room temperature, preferably for 0.5-3h; 4. The production method according to claim 2, characterized by, in step S2, after the dimethylamine lithium emulsion is added dropwise, the reaction is carried out at-78℃ to-30℃, preferably for 0.5-3h; and then the reaction is carried out at a temperature ≥0℃ and <60℃, preferably for more than 10h; 5. The preparation method according to claim 2, characterized in that, in step S3, after the cyclopentadiene is added dropwise, the reaction is carried out at-78℃ to 0℃, preferably for 0.5-3h; and then the reaction is carried out at an increased temperature, and when the temperature is increased to 45-60℃, the reaction is carried out under reflux, preferably for more than 10h.

6. The preparation method according to claim 2, characterized in that, 7. The preparation method according to any one of claims 1-6, wherein ​ The molar ratio of the n-butyllithium and the dimethylamine is 1:1.1-1.6; And / or, the molar ratio of the n-butyllithium and the hafnium tetrachloride is 3.8-4.2:1; And / or, the molar ratio of the cyclopentadiene and the hafnium tetrakis(dimethylamide) is 1.10-1.30:

1.

8. The method of any one of claims 1-6, wherein, In step S3, the cyclopentadiene is prepared on site; preferably, the cyclopentadiene is obtained by collecting the condensate after thermal cracking of dicyclopentadiene.

9. The method of any one of claims 1-6, wherein, Steps S1 to S3 are all carried out under inert gas protection.

10. The method of claim 9, wherein, The inert gas is one or more of nitrogen, argon, and helium.