Recrystallization purification process of high-purity ALD precursor penta (dimethylamino) tantalum

Abstract

The invention relates to a purification method of penta (dimethylamino) tantalum, and relates to the technical field of purification of amino metal compounds. In a standard glove box with the oxygen content lower than 2 ppm and the water content lower than 0.01 ppm, taking a proper amount of sublimated crude product penta (dimethylamino) tantalum, putting the sublimated crude product penta (dimethylamino) tantalum into a dry and clean sample bottle, adding a solvent after water and oxygen removal to dissolve the penta (dimethylamino) tantalum, and filtering; and then cooling and crystallizing, slowly reducing the temperature until crystals are separated out, and slowly crystallizing to generate faint yellow micro-transparent crystals. After crystallization is completed, filtering is conducted again in a low-temperature state, and crystals are dried in vacuum. And after the mother liquor is desolventized to evaporate out the solvent, the recovered crude product penta (dimethylamino) tantalum can be sublimated and recycled again.

Description

Technical Field

[0001] The present invention relates to the field of fine chemicals. In particular, the present invention relates to a recrystallization purification process for pentakis(dimethylamino)tantalum. Background Art

[0002] According to Moore's Law, with the continuous development of semiconductor technology, the feature size of the core device of integrated circuits, the Metal Oxide Semiconductor Filed Effect Transitors (MOSFET), will become smaller and smaller, and correspondingly, the thickness of SiO2 as the gate dielectric layer will become thinner and thinner. When the CMOS process develops to the 45 nm technology node, the thickness of SiO2 has been reduced to its physical limit. Then, the method to increase the gate oxide capacitance is to increase the relative dielectric constant of the gate oxide dielectric material, that is, to use a dielectric material with a larger dielectric constant (High-k material, such as Ta2O5, TaN, etc.) to replace the SiO2 gate dielectric. With the requirements of the semiconductor industry for high-performance and low-power devices, the demand for High-k materials is also increasing year by year. The ALD / CVD reaction of amino metal compounds has been used to prepare these materials.

[0003] Pentakis(dimethylamino)tantalum, with the molecular formula C 10 H 30 N5Ta, is a white to light yellow solid at room temperature and is a compound very sensitive to air and water vapor. It can dissolve in organic solvents such as saturated alkanes, benzene, and dichloromethane. The physical and chemical properties of pentakis(dimethylamino)tantalum are suitable for being used as a precursor to deposit tantalum oxide films through the ALD reaction, and it is a hot spot in the current ALD research field; for actual production, an ideal precursor material needs to have good stability, high reactivity, and also have a high enough purity to ensure that the obtained film will not cause device problems (such as halogen corrosion, current leakage, etc.).

[0004] CN201710492823.4 discloses a synthesis method of pentakis(dimethylamino)tantalum. Under the protection of an inert atmosphere, an organolithium reagent and a hydrocarbon solvent are added to a reactor, and then dimethylamine gas is introduced into the system to prepare lithium dimethylamide; tantalum pentachloride is added to the system, and after adding, the reaction is stirred under the protection of an inert atmosphere; after the reaction is completed, filtration is carried out, and the obtained filtrate is distilled to remove the hydrocarbon solvent; after all the solvent is removed, the solid is sublimated to obtain the pentakis(dimethylamino)tantalum product. Without any ether solvents, only a single hydrocarbon solvent is required, which reduces the synthesis cost and the toxicity of the reaction, has better operability, and the by-products during the reaction are relatively few, and the yield is relatively high.

[0005] CN 201911061946.8 discloses a purification method of tantalum pentakis(dimethylamide), which is carried out by vacuum sublimation in a horizontal sublimation refining tower. The refining tower includes a heating unit, an adsorption unit and a collection unit. The heat for the sublimation of tantalum pentakis(dimethylamide) is provided by a precise temperature control heating method using magnetic induction. At the same time, a metal-organic framework ceramic is added to the adsorption unit, which can further adsorb impurities in the tantalum pentakis(dimethylamide) vapor, thereby improving the purity of the product.

[0006] Although tantalum pentakis(dimethylamide) has a high enough vapor pressure to sublime, sublimation can only remove residual halides, impurity metal ions and solvents to a certain extent, and some impurities will also sublime together. For example, tantalum pentakis(dimethylamide) is extremely sensitive to trace amounts of water and oxygen. During the sublimation process, it will inevitably contact trace amounts of oxygen, producing a small amount of by-product Ta(NMe2)4(η 2 -MeNCH2NMe2). The by-product Ta(NMe2)4(η 2 -MeNCH2NMe2) has a similar structure and properties to the product Ta(NMe2)5, and some by-products will sublime together with the product during the sublimation process. The characteristic peaks of the by-product can always be observed at 2.16, 3.13, 3.30 and 3.98 ppm by NMR detection, resulting in the organic NMR purity being difficult to reach 99%. Summary of the Invention

[0007] The purpose of the present invention is to make up for the defects of the prior art. First, the crude tantalum pentakis(dimethylamide) is separated by sublimation to remove chlorides and metal impurities, and then the sublimated product is recrystallized to achieve complete separation of the product and the by-product.

[0008] The recrystallization method utilizes the difference in solubility for a specific solvent. Therefore, even trace amounts of impurities with similar properties can be removed. Especially when tantalum pentakis(dimethylamide) and the by-product Ta(NMe2)4(η 2 -MeNCH2NMe2) cannot be completely purified by the sublimation method, considering using the recrystallization method with a suitable solvent to achieve complete separation of the product and the by-product.

[0009] Therefore, the inventors studied the purification of tantalum pentakis(dimethylamide) by the recrystallization method. However, if only the conventional recrystallization method is used for crystallization, it is found that orange oily particles will appear after recrystallization, and a new impurity peak appears at 3.39 ppm by 1H NMR detection.

[0010] The inventors have fully explored the nature and formation reasons of new impurities in the recrystallization process. Experiments have found that even after the sublimation is completed, this kind of impurity will still be generated after the crude pentakis(dimethylamino)tantalum is subjected to conventional recrystallization operations. The inventors believe that this by-product is caused by the reaction of pentakis(dimethylamino)tantalum with water and oxygen in the solvent during the recrystallization step, and has the characteristic of co-dissolving and precipitating with pentakis(dimethylamino)tantalum during the recrystallization process.

[0011] The technical solution proposed by the present invention is as follows: A recrystallization purification process for pentakis(dimethylamino)tantalum specifically includes the following steps: (1) In a standard glove box, add an appropriate amount of n-butyllithium to the solvent used for recrystallizing pentakis(dimethylamino)tantalum and heat under reflux for 2 - 5 h to ensure that the water and oxygen in the solvent are completely removed (water < 0.1 ppm, oxygen < 0.1 ppm), and then distill out the solvent.

[0012] (2) Dissolution of pentakis(dimethylamino)tantalum: In a standard glove box, dissolve the sublimated crude pentakis(dimethylamino)tantalum in the water- and oxygen-free solvent at room temperature.

[0013] (3) Recrystallization: Filter the prepared solution to remove undissolved solid impurities to obtain a clear solution, and slowly cool it to -15 to 0 °C for freeze crystallization. After 1 - 5 hours, the crystals of pentakis(dimethylamino)tantalum will precipitate.

[0014] (4) Separation: Filter the solution after crystallization is completed at a low temperature to obtain crystals.

[0015] (5) Drying: Use vacuum drying for the crystals obtained in step (4) to obtain pure pentakis(dimethylamino)tantalum.

[0016] Further, the atmosphere requirement of the standard glove box used for recrystallization and purification of pentakis(dimethylamino)tantalum in step (1) is that the oxygen content is lower than 2 ppm and the water content is lower than 0.01 ppm. Using n-butyllithium solution to remove water and oxygen from the solvent in a standard glove box can ensure operation safety; n-butyllithium solution is used as a raw material for synthesizing pentakis(dimethylamino)tantalum, and using n-butyllithium solution to remove water and oxygen can ensure that no new impurity ions are introduced; n-butyllithium is a strong alkaline and reactive reagent sensitive to water and oxygen, and using n-butyllithium solution to remove water and oxygen from the solvent can ensure that the water and oxygen in the solvent are completely removed.

[0017] Further, the solvent in step (2) is in an anhydrous and anoxic state (water < 0.1 ppm, oxygen < 0.1 ppm). By this method, even if pentakis(dimethylamino)tantalum contains trace impurities, complete separation can be achieved, and no new by-products are generated after recrystallization.

[0018] Furthermore, the solvents for recrystallization purification of pentakis(dimethylamino)tantalum include halogenated alkanes, nitriles, ethers, and alkanes. It is preferably selected from alkanes.

[0019] When selecting the amount of organic solvent, the following factors need to be considered: on the one hand, the amount of organic solvent should be able to fully dissolve the crude pentakis(dimethylamino)tantalum, and it is appropriate that no crystals precipitate from the solution during aging; on the other hand. The organic solvent does not react chemically with pentakis(dimethylamino)tantalum. When ensuring complete dissolution, too little amount of organic solvent will lead to crystal precipitation and impurity encapsulation during the aging process, reducing the product purity and yield; too much amount of organic solvent will lead to a decrease in crystal precipitation during recrystallization and reduce the product yield.

[0020] Furthermore, the mass ratio of the crude pentakis(dimethylamino)tantalum to the solvent in step (2) is: (1 - 5):1.

[0021] Furthermore, in step (3) during the cooling crystallization stage, it is also necessary to ensure that the solvent is always in an anhydrous and anoxic state (water < 0.1 ppm, oxygen < 0.1 ppm).

[0022] Furthermore, the temperature of the cooling crystallization for recrystallization purification of pentakis(dimethylamino)tantalum in step (3) is controlled at -15 to 0 °C, and the time for each freeze crystallization is controlled at 1 to 5 h.

[0023] Furthermore, the temperature for vacuum drying of the recrystallized pentakis(dimethylamino)tantalum crystals in step (5) is 60 - 80 °C, and it is ensured that the recrystallization process is carried out in a standard glove box (water < 0.01 ppm, oxygen < 2 ppm).

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention proposes a new method for recrystallization purification of pentakis(dimethylamino)tantalum. The equipment is simple, the conditions are simple and easy to control, and the solvent can be recycled. Compared with the conventional sublimation method, it can achieve complete separation of the product and by-products, obtain a high-purity product, the recovery rate can reach more than 78%, and the organic purity can reach more than 99%.

[0025] (2) The purification cost of this method is low, the overall purification yield is high, and theoretically there is no generation of waste gas and waste liquid, which is safe, environmentally friendly, and suitable for industrial production.

[0026] (3) After the mother liquor after recrystallization is desolvated to evaporate the solvent, the product with more impurities obtained can be sublimated and recycled for reuse. Description of the Drawings

[0028] Figure 1 For the product obtained after sublimation 11H NMR spectrum.

[0029] Figure 2 1H NMR spectrum of the product obtained by conventional recrystallization operation 1 1H NMR spectrum.

[0030] Figure 3 1H NMR spectrum of the high-purity tantalum pentakis(dimethylamino) product prepared in Example 1 1 1H NMR spectrum. Detailed implementation manners

[0032] The present invention will be further described below in conjunction with specific embodiments for better understanding, but the present invention is not limited to these embodiments. The experimental methods in the following embodiments are all conventional methods unless otherwise specified. The present invention places no particular limitation on the crude tantalum pentakis(dimethylamino) used herein, including tantalum pentakis(dimethylamino) prepared by known methods or commercially available tantalum pentakis(dimethylamino).

[0033] Example 1 In a standard glove box with an oxygen content of less than 2 ppm and a water content of less than 0.01 ppm, 5 g of crude tantalum pentakis(dimethylamino) with a purity of 96.15% was taken. It was placed in a dry and clean sample bottle, and 4 g of anhydrous and oxygen-free n-hexane after distillation of n-butyllithium was added to the sample bottle until the tantalum pentakis(dimethylamino) was completely dissolved, obtaining a highly concentrated saturated yellow clear solution.

[0034] The prepared solution was filtered to remove solid impurities, and then cooled for crystallization, with the temperature decreasing at 2 °C / min to -15 °C, and slowly crystallized for 2 h to form light yellow slightly transparent crystals. After the crystallization was completed, the solution was filtered at low temperature to obtain the crystals, and the crystals were dried in vacuo and heated to 60 °C for drying.

[0035] 3.85 g of pure tantalum pentakis(dimethylamino) was obtained, and the yield of the obtained tantalum pentakis(dimethylamino) finished product was 77%. The purified tantalum pentakis(dimethylamino) was subjected to purity detection, and the nuclear magnetic resonance hydrogen spectrum is as Figure 3 shown, and the nuclear magnetic purity of the finished tantalum pentakis(dimethylamino) is 99.24%.

[0036] Example 2 In a standard glove box with an oxygen content of less than 2 ppm and a water content of less than 0.01 ppm, 5 g of crude tantalum pentakis(dimethylamino) with a purity of 96.15% was taken. It was placed in a dry and clean sample bottle, and 2.5 g of n-hexane was added to the sample bottle until the tantalum pentakis(dimethylamino) was completely dissolved, obtaining a highly concentrated yellow clear solution state.

[0037] Filter the prepared solution to remove solid impurities, and then carry out cooling crystallization. Let the temperature drop to -5°C at a rate of 2 °C / min, and slowly crystallize for 4 h to form light yellow slightly transparent crystals. Filter the solution after crystallization is completed at low temperature to obtain crystals, and vacuum dry the crystals and heat them to 60°C for drying.

[0038] 3.92 g of pure pentakis(dimethylamino)tantalum was obtained. The yield of the obtained pentakis(dimethylamino)tantalum product was 78.4%, and the nuclear magnetic purity of the product pentakis(dimethylamino)tantalum was 99.31%.

[0039] Example 3 In a standard glove box with an oxygen content lower than 2 ppm and a water content lower than 0.01 ppm, take 5 g of crude pentakis(dimethylamino)tantalum with a purity of 96.15%. Place it in a dry and clean sample bottle, and add 3.3 g of anhydrous and oxygen-free toluene after distilling n-butyllithium to the sample bottle until the pentakis(dimethylamino)tantalum is fully dissolved to obtain a high-concentration yellow clear liquid state.

[0040] Filter the prepared solution to remove solid impurities, and then carry out cooling crystallization. Let the temperature drop to -15°C at a rate of 2 °C / min, and slowly crystallize for 2 h to form light yellow slightly transparent crystals. Filter the solution after crystallization is completed at low temperature to obtain crystals, and vacuum dry the crystals and heat them to 60°C for drying.

[0041] 3.35 g of pure pentakis(dimethylamino)tantalum was obtained. The yield of the obtained pentakis(dimethylamino)tantalum product was 67%, and the nuclear magnetic purity of the product pentakis(dimethylamino)tantalum was 99.58%.

[0042] Example 4 In a standard glove box with an oxygen content lower than 2 ppm and a water content lower than 0.01 ppm, take 5 g of crude pentakis(dimethylamino)tantalum with a purity of 96.15%. Place it in a dry and clean sample bottle, and add 3.5 g of anhydrous and oxygen-free n-pentane after distilling n-butyllithium to the sample bottle until the pentakis(dimethylamino)tantalum is fully dissolved to obtain a high-concentration yellow clear liquid state.

[0043] Filter the prepared solution to remove solid impurities, and then carry out cooling crystallization. Let the temperature drop to 0°C at a rate of 1 °C / min, and slowly crystallize for 4 h to form light yellow slightly transparent crystals. Filter the solution after crystallization is completed at low temperature to obtain crystals, and vacuum dry the crystals and heat them to 80°C for drying.

[0044] 3.62 g of pure pentakis(dimethylamino)tantalum was obtained. The yield of the obtained pentakis(dimethylamino)tantalum product was 72.4%, and the nuclear magnetic purity of the product pentakis(dimethylamino)tantalum was 99.62%.

[0045] Example 5 In a standard glove box with an oxygen content of less than 2 ppm and a water content of less than 0.01 ppm, 15 g of crude pentakis(dimethylamino)tantalum with a purity of 96.15% was taken. It was placed in a dry and clean sample bottle, and 10.5 g of anhydrous and oxygen-free n-pentane after distillation of n-butyllithium was added to the sample bottle until the pentakis(dimethylamino)tantalum was completely and fully dissolved, obtaining a high-concentration yellow clear liquid state.

[0046] The prepared solution was filtered to remove solid impurities, and then cooled for crystallization. The temperature was decreased to -10 °C at a rate of 1 °C / min and slowly crystallized for 2 h to form light yellow slightly transparent crystals. The solution after crystallization was filtered at low temperature to obtain the crystals, and the crystals were dried in vacuum and heated to 80 °C for drying.

[0047] 11.58 g of pure pentakis(dimethylamino)tantalum was obtained. The yield of the obtained pentakis(dimethylamino)tantalum product was 77.2%, and the nuclear magnetic purity of the finished product pentakis(dimethylamino)tantalum was 99.68%.

[0048] Example 6 In a standard glove box with an oxygen content of less than 2 ppm and a water content of less than 0.01 ppm, 15 g of crude pentakis(dimethylamino)tantalum with a purity of 96.15% was taken. It was placed in a dry and clean sample bottle, and 10.5 g of anhydrous and oxygen-free n-pentane after distillation of n-butyllithium was added to the sample bottle until the pentakis(dimethylamino)tantalum was completely and fully dissolved, obtaining a high-concentration yellow clear liquid state.

[0049] The prepared solution was filtered to remove solid impurities, and then cooled for crystallization. The temperature was decreased to -10 °C at a rate of 0.5 °C / min and slowly crystallized for 4 h to form light yellow slightly transparent crystals. The solution after crystallization was filtered at low temperature to obtain the crystals, and the crystals were dried in vacuum and heated to 80 °C for drying.

[0050] 11.67 g of pure pentakis(dimethylamino)tantalum was obtained. The yield of the obtained pentakis(dimethylamino)tantalum product was 77.8%, and the nuclear magnetic purity of the finished product pentakis(dimethylamino)tantalum was 99.85%.

[0051] Comparative Example 1 In a standard glove box with an oxygen content of less than 2 ppm and a water content of less than 0.01 ppm, 15 g of crude pentakis(dimethylamino)tantalum with a purity of 96.15% was taken. It was placed in a dry and clean sample bottle, and 10.5 g of conventional n-pentane without water and oxygen removal was added to the sample bottle until the pentakis(dimethylamino)tantalum was completely and fully dissolved, obtaining a high-concentration yellow clear liquid state.

[0052] Filter the prepared solution to remove solid impurities, and then perform cooling crystallization. Slowly lower the temperature to -10°C and slowly crystallize for 2 h to form light yellow slightly transparent crystals. Filter the solution after crystallization is completed at low temperature to obtain the crystals, and vacuum dry the crystals and heat them to 80°C for drying.

[0053] 10.87 g of pure pentakis(dimethylamino)tantalum was obtained. The yield of the obtained pentakis(dimethylamino)tantalum product was 72.4%. The nuclear magnetic purity of the product pentakis(dimethylamino)tantalum was 97.88%, and there was a new impurity peak at 3.96 ppm. According to the above experiments, it can be confirmed that new by-products are generated during purification in the presence of trace water and oxygen.

[0054] Comparative Example 2 In a standard glove box with an oxygen content lower than 2 ppm and a water content lower than 0.01 ppm, take 15 g of crude pentakis(dimethylamino)tantalum with a purity of 96.15%. Place it in a dry and clean sample bottle, and add 10.5 g of n-pentane after distilling to remove water and oxygen with metallic sodium to the sample bottle until the pentakis(dimethylamino)tantalum is completely and fully dissolved to obtain a high-concentration yellow clear liquid state.

[0055] Filter the prepared solution to remove solid impurities, and then perform cooling crystallization. Lower the temperature to -10°C at a rate of 0.5°C / min and slowly crystallize for 2 h to form light yellow slightly transparent crystals. Filter the solution after crystallization is completed at low temperature to obtain the crystals, and vacuum dry the crystals and heat them to 80°C for drying.

[0056] 11.24 g of pure pentakis(dimethylamino)tantalum was obtained. The yield of the obtained pentakis(dimethylamino)tantalum product was 74.9%. The nuclear magnetic purity of the product pentakis(dimethylamino)tantalum was 98.63%, and there was a new impurity peak at 3.96 ppm. According to the above experiments, it can be confirmed that new by-products are generated during purification in the presence of trace water and oxygen. And the effect of removing water and oxygen from the solvent by refluxing with metallic sodium is worse than that of n-butyllithium solution.

[0057] Although the present invention has been described in detail with reference to exemplary embodiments herein, it should be understood that the present invention is not limited to the described embodiments. Any modifications, equivalent substitutions, improvements, etc. made to the above embodiments based on the technical essence of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for recrystallization purification of pentakis(dimethylamino)tantalum, characterized in that, It includes the following steps: Dissolution step: Dissolve the crude pentakis(dimethylamino)tantalum in the pretreated solvent sufficiently to obtain a recrystallization solution, where the solvent is a polar organic solvent; Filtration step: Filter the solid impurities in the recrystallization solution; Recrystallization step: Lower the temperature of the recrystallization solution to precipitate pentakis(dimethylamino)tantalum crystals.

2. The recrystallization purification method according to claim 1, characterized in that The solvent is one of halogenated alkanes, nitriles, ethers, alkanes.

3. The recrystallization purification method according to claim 1, characterized in that, In the dissolution step, the mass ratio of the crude pentakis(dimethylamino)tantalum to the solvent is (1 - 5):1, and the organic purity requirement of the crude product is >95%.

4. The recrystallization purification method according to claim 1, characterized in that In the dissolution step, the water content of the solvent is less than 0.1 ppm, and the oxygen content is less than 0.1 ppm.

5. The recrystallization purification method according to claim 1, characterized in that In the dissolution step, the solvent pretreatment method is to add a n-butyllithium solution to the solvent, heat and reflux the solvent, and then distill to obtain the solvent.

6. The recrystallization purification method according to claim 1, wherein In the recrystallization step, the ambient temperature is -15 - 0°C, and the cooling rate is 0.5 - 3°C / min.

7. The recrystallization purification method according to claim 6, wherein In the recrystallization step, maintain for 1 - 5 h at the ambient temperature.

8. The recrystallization purification method according to claim 1, characterized in that Both the filtration step and the recrystallization step are carried out in an environment with an oxygen content lower than 2 ppm and a water content lower than 0.01 ppm.

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