A tetra(methylethylamino)hafnium product and its preparation method

Abstract

This invention provides a tetra(methylethylamino)hafnium product and its preparation method. This method prepares high-purity tetra(methylethylamino)hafnium and purifies it by removing metal ions under specific anhydrous, oxygen-free, and dust-free conditions. It features a short reaction time, high safety, high product yield, and simple post-processing. It effectively controls and removes the metal ion content, which has the most stringent quality requirements, resulting in a final product with a total metal ion content not exceeding 0.76 ppm, a purity of ≥99.99992%, and a high yield (≥50%), fully meeting the needs of current advanced integrated circuit manufacturing. This invention not only solves the key problem of improving the purity of tetra(methylethylamino)hafnium during production but also greatly enhances the feasibility and economic benefits of its industrial production. This is crucial for meeting the rapid development needs of the integrated circuit industry and also brings significant practical implications for promoting technological progress in the semiconductor industry.

Description

Technical Field

[0001] This invention relates to the field of electronic chemicals in high-end fine chemicals, specifically to a tetra(methylethylamino)hafnium (TEMAH) product, an important precursor required for depositing HfO2 thin films, and its preparation method. Background Technology

[0002] HfO2 has recently attracted much attention as a dielectric material due to its high dielectric constant and excellent leakage characteristics resulting from its wide bandgap. In particular, HfO2 thin films have been extensively studied as high-κ gate dielectrics in metal-oxide-semiconductor field-effect transistors (MOSFETs) because HfO2 is thermodynamically stable when in contact with Si and exhibits a low trap density at the HfO2 / Si interface. The thermal stability of HfO2 allows it to effectively suppress the formation of low-κ SiOx interface layers even at high temperatures, and its low interface trap density allows for high field-effect mobility of electron carriers in MOSFETs.

[0003] In the scaling down of devices, the physical thickness of HfO2 films should be reduced to less than 10 nm. Among the various growth techniques available for growing such HfO2 films, atomic layer deposition (ALD) is one of the most promising methods. Based on self-limiting growth, ALD allows for excellent thickness control at the atomic scale, uniform film growth over large areas, and excellent conformal properties in three-dimensional structures. Therefore, the ALD process for HfO2 films has been extensively studied.

[0004] Tetra(methylethylamino)hafnium (TEMAH) is an important precursor for depositing HfO2 thin films using atomic layer deposition (ALD) technology. With the rapid development of the integrated circuit industry, the demand for semiconductor precursor materials will continue to increase, and tetra(methylethylamino)hafnium has a very good market prospect.

[0005] However, existing methods for producing tetra(methylethylamino)hafnium have some significant problems. For example, CN106916178A discloses a method for producing tetra(methylethylamino)hafnium, which involves reacting n-BuLi with methylethylamine and then adding hafnium tetrachloride in batches. Hafnium tetrachloride is very sensitive to air, water, and oxygen, and adding it in batches after the reaction is difficult and dangerous. The best feeding method is to pre-add hafnium tetrachloride to the reactor before the subsequent reaction. The disclosed method also describes a solid-liquid separator to remove LiCl, but LiCl is fine and light, so centrifugation is a better treatment method. The method disclosed in CN103601750A is similar to the above method. No purification methods for tetra(methylethylamino)hafnium have been reported to date. As a crucial precursor material in the integrated circuit field, its purity requirements are extremely stringent, and existing technologies are clearly insufficient. Therefore, a new technology is urgently needed to address this issue, requiring the development of a new, efficient, and safe method for producing tetra(methylethylamino)hafnium, particularly addressing how to improve purity during the production process. This is not only crucial for meeting the rapid development needs of the integrated circuit industry but also has significant practical implications for promoting technological advancements in the semiconductor industry. Summary of the Invention

[0006] To address the problems of low product purity, long reaction time, cumbersome operation, and poor safety in the existing tetra(methylethylamino)hafnium (TEMAH) preparation process, and the inability of the obtained product to meet the current needs of advanced integrated circuit manufacturing, this invention provides a tetra(methylethylamino)hafnium preparation method with short reaction time, good safety, high product yield, and simple post-processing operation. At the same time, a purification method for removing metal ions by adsorption is developed, resulting in high product purity that meets the needs of practical applications.

[0007] The specific process route for preparing tetra(methylethylamino)hafnium according to the present invention is as follows:

[0008] Under anhydrous, oxygen-free, and dust-free conditions at -30 to 10°C, hafnium tetrachloride and N-ethylmethylamine were complexed in an organic solvent for 1 to 5 hours, with a molar ratio of N-ethylmethylamine to hafnium tetrachloride of 4.4 to 5.8:1. Subsequently, an n-BuLi solution was slowly added to react with N-ethylmethylamine in a lithium-hydrogen exchange reaction to generate lithium dimethylaminodimethylamine, with a molar ratio of n-BuLi to hafnium tetrachloride of 4.4 to 5.8:1. The reaction was carried out for 2 to 12 hours. The reaction temperature was increased, and lithium dimethylaminodimethylamine and hafnium tetrachloride underwent a nucleophilic reaction for 16 to 72 hours. The solid was removed by centrifugation, and the product was concentrated, solvent removed, and distilled under reduced pressure to obtain tetra(methylamino)hafnium. The product content was greater than 99%, and the yield was greater than 50% (based on hafnium tetrachloride).

[0009] In the preferred embodiment of the above-described technical solution, the molar ratio of N-ethylmethylamine to hafnium tetrachloride is 4.4–5.4:1, and more preferably 4.8–5.2:1.

[0010] In the preferred embodiment of the above-described technical solution, the solvent of the n-BuLi solution is selected from at least one of n-hexane, n-heptane, and cyclohexane, and more preferably an n-BuLi solution in n-hexane, with a concentration preferably of 1.5 to 3 mol / L, and more preferably 2.5 mol / L.

[0011] For the technical solution described above, in a preferred embodiment, the molar ratio of n-BuLi to hafnium tetrachloride is 4.0 to 5.6:1, more preferably 4.4 to 5.2:1, and even more preferably 4.8 to 5.2:1.

[0012] For the technical solution described above, in a preferred embodiment, the n-BuLi solution is added at a rate of 0.5 to 5 mL / min, and more preferably at a rate of 1 to 3 mL / min.

[0013] In the preferred embodiment of the above-described technical solution, the organic solvent is an alkane (C12-C12). n H 2n+2 And / or ethers, wherein n is selected from any integer from 5 to 8, more preferably at least one of n-pentane, n-hexane, and diethyl ether, and even more preferably n-hexane.

[0014] For the technical solution described above, in a preferred embodiment, the reaction temperature for the lithium hydrogen exchange is -30 to -10°C, and more preferably -20 to -10°C.

[0015] For the technical solution described above, in a preferred embodiment, the time for the hydrogen-lithium exchange reaction is 2 to 12 hours, and more preferably 2 to 10 hours.

[0016] In the preferred embodiment of the above-described technical solution, the nucleophilic reaction temperature is 50–65°C.

[0017] For the technical solution described above, in a preferred embodiment, the reaction time of the nucleophilic reaction is 16 to 72 hours, and more preferably 16 to 30 hours.

[0018] In the preferred embodiment of the above-described technical solution, the solid LiCl is separated by high-speed centrifugation at a speed of 1000–4000 rpm for 10–20 minutes.

[0019] In the preferred embodiment of the above-described technical solution, after concentration and solvent removal, the liquid is obtained by vacuum distillation (0.02–0.05 mmHg, 50–60 °C) to obtain a colorless to pale yellow liquid.

[0020] In the preferred embodiment of the above-described technical solution, the process of removing metal ion impurities with an adsorbent is also included. After adsorption, the purified product can be obtained by simple filtration, and the total metal ion content in the product does not exceed 0.03 ppm. The adsorbent is selected from at least one of activated carbon, silica gel, molecular sieve, and ion exchange resin. In the example, crown ether modified silica gel (3) and C107E type acrylic weak acid cation exchange resin (Purolite) described in paragraph 2 of the document 10.3969 / j.issn.1007-9629.2001.01.011 were specifically selected for the experiment, and ideal technical effects were obtained.

[0021] For the technical solution described above, in a preferred case, the adsorption temperature is 0-50℃, and the product is obtained by filtration after adsorption. In a more preferred case, the adsorption temperature is 20-50℃, and even more preferably 20-40℃. Furthermore, the adsorption residence time is 10-24h, and more preferably 12-24h.

[0022] For the technical solution described above, in a preferred embodiment, the amount of adsorbent used is 0.2 to 0.6 g per milliliter of TEMAH, and more preferably 0.2 to 0.4 g per milliliter of TEMAH.

[0023] Another aspect of the present invention is to protect the tetra(methylethylamino)hafnium product obtained by the above method, with a yield of more than 50.0%; more preferably, a yield of more than 90.0% (based on TEMAH), a purity of ≥99.99992%, more preferably a purity of ≥99.999997%, and a total metal ion content of not more than 0.76 ppm, more preferably not more than 0.03 ppm.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) The method of the present invention has a short reaction time and simple post-processing operation, and has a good prospect for industrialization.

[0026] (2) This invention develops a purification method for tetra(methylethylamino)hafnium, which effectively removes and controls the content of metal ions with the most stringent product quality requirements; and conducts testing; the total metal ion content in the final product does not exceed 0.03 ppm;

[0027] (3) Tetra(methylethylamino)hafnium has a high yield (≥50%) and high purity (≥99.99992%), which can meet the needs of current practical applications. Attached Figure Description

[0028] Figure 1 This is a diagram of the TEMAH structure;

[0029] Figure 2 NMR structure spectrum of TEMAH 1 H NMR (400Hz, toluene-d8);

[0030] Figure 3 This is a flowchart of the TEMAH process flow. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present invention, the present invention will be further illustrated by the following embodiments. However, these embodiments do not limit the scope of the present invention. The technical means used in the embodiments are conventional means well known to those skilled in the art.

[0032] The method for detecting trace metal ion content described in the example is as follows: Take 5-50 mg of the purified product, weigh it accurately, and add 0.5 mL of concentrated sulfuric acid (analytical grade) for every 10 mg of sample. Heat to 90°C, and after the liquid turns black, add nitric acid (99.999%). Add 1 mL of nitric acid for every 10 mg of product. Try to evaporate the acid as much as possible during the sample preparation process. After digestion, make up to 100 mL of the sample solution with deionized water. Prepare the control sample simultaneously. The ion concentration is determined by inductively coupled plasma mass spectrometry (Nexion 5000G). The metal impurity content in the tetra(methylethylamino)hafnium product is calculated based on the test results.

[0033] Example 1

[0034] Under anhydrous, oxygen-free, and dust-free conditions, hafnium tetrachloride (0.32 g, 1 mmol) was added to a 10 mL reaction flask, followed by 3.0 mL of n-hexane. The flask was then placed in a -10 °C cold bath, and N-ethylmethylamine (0.296 g) was slowly added. After reacting for 1 h, 2.5 M n-BuLi (2.0 mL) was slowly added, and the reaction was continued for 2 h. The temperature was then slowly increased to 55 °C, and the reaction was continued for 24 h. The solid was removed by centrifugation, and the separated liquid was concentrated to remove the solvent n-hexane. The remaining liquid was then distilled under reduced pressure to obtain a colorless to pale yellow liquid, which was tetra(methylethylamino)hafnium (TEMAH), with a yield of 78.6%.

[0035] Example 2-31

[0036] The preparation method of TEMAH was investigated. Based on the method steps provided in Example 1, five aspects were changed: the solvent type of the n-BuLi solution, the reaction temperature during the slow-rise phase, the stoichiometric amount of reactants, the concentration of the substrate, and the reaction time. The yield of the product was tested under the condition of changing a single factor, and the results are shown in Table 1 below:

[0037] Table 1

[0038]

[0039]

[0040] Conclusion: Examples 5, 6, 7, and 8 had low yields due to the low reaction temperatures. At lower temperatures, the reaction may not proceed fully or the reaction rate may slow down, resulting in a reduction in the amount of the target product. Therefore, it is recommended to appropriately increase the reaction temperature to obtain higher yields.

[0041] In Example 20, the yield was low due to the large amount of solvent and the low substrate concentration; appropriately increasing the substrate concentration is beneficial to improving the reaction yield.

[0042] In Examples 27 and 28, the reaction time was too short, resulting in incomplete conversion of hafnium tetrachloride and thus low yields. During the reaction process, insufficient reaction time may prevent the reactants from reacting completely, leading to a decrease in yield. Therefore, it is recommended to appropriately extend the reaction time to promote complete conversion of hafnium tetrachloride and obtain a higher yield.

[0043] Example 32

[0044] Under anhydrous, oxygen-free, and dust-free conditions, hafnium tetrachloride (6 g, 18.73 mmol) was added to a 10 mL reaction flask, followed by 35 mL of n-hexane. The flask was then placed in a -10 °C cold bath, and N-ethylmethylamine (5.54 g) was slowly added. After reacting for 1 h, 2.5 M n-BuLi (37.46 mL) was slowly added, and the reaction was continued for 2 h. The temperature was then slowly increased to 55 °C, and the reaction was continued for 24 h. The solid was removed by centrifugation, and the separated liquid was concentrated to remove the solvent n-hexane. The remaining liquid was then distilled under reduced pressure to obtain a colorless to pale yellow liquid, which was tetra(methylethylamino)hafnium (TEMAH), with a yield of 76.7%. The scale-up synthesis of the product showed excellent results, and the yield was within the expected range.

[0045] Example 33

[0046] Under anhydrous, oxygen-free, and dust-free conditions, 0.5 mL of tetra(methylethylamino)hafnium (TEMAH) obtained by distillation in Example 1 was placed in a reaction flask equipped with a stir bar. 0.1 g of crown ether modified silica gel (10.3969 / j.issn.1007-9629.2001.01.011.) was added for adsorption purification. The adsorption temperature was 35℃, the stirring speed was 300 rpm, and the adsorption time was 10 h. The product was obtained by vacuum distillation (0.02 mmHg, 55℃). 13.3 mg of TEMAH was taken and a sample was prepared according to the above method. After trace metal ion content detection, the total metal ion content was 0.03 ppm, and the purity was 99.999997%. The content of each metal element in the purified product is shown below:

[0047] Zn 0.004 0.03 Ni 0.000 0.00 Al <DL ND K <DL ND Fe 0.000 0.00 Mn 0.000 0.00 Cr <DL 0.00 Mg <DL ND Cu 0.000 0.00 Ca <DL ND Na <DL ND

[0048] The results of the trace metal ion content test indicate that crown ether modified silica gel is an effective adsorbent that can effectively remove impurity metal ions from TEMAH and improve the purity of the product.

[0049] Example 34

[0050] Under anhydrous, oxygen-free, and dust-free conditions, 0.5 mL of tetra(methylethylamino)hafnium (TEMAH) obtained from the initial distillation in Example 1 was placed in a reaction flask equipped with a stir bar. 0.15 g of C107E type acrylic weak acid cation exchange resin (Purolite) was added for adsorption purification. The adsorption temperature was 10℃, the stirring speed was 300 rpm, and the adsorption time was 16 h. The product was obtained by vacuum distillation. 13.3 mg of TEMAH was taken and a sample was prepared according to the above method. After trace metal ion content detection, the total metal ion content was 0.58 ppm, and the purity was >99.99994%. The content of each metal element in the purified product is shown below:

[0051] Zn 0.000 0.00 Ni 0.002 0.02 Al <DL ND K <DL ND Fe 0.029 0.28 Mn <DL ND Cr 0.000 0.00 Mg 0.011 0.10 Cu 0.017 0.16 Ca <DL ND Na <DL ND

[0052] The trace metal ion content detection results showed that the total metal ion content was 0.58 ppm, with a purity >99.99994%. Although the purity was slightly lower than that obtained using crown ether modified silica gel, it was still very high, and the content of each metal element was also low. This indicates that C107E type acrylic weakly acidic cation exchange resin is also a feasible adsorbent choice that can effectively improve the purity of TEMAH.

[0053] Example 35

[0054] Under anhydrous, oxygen-free, and dust-free conditions, 0.5 mL of tetra(methylethylamino)hafnium (TEMAH) obtained from the initial distillation in Example 1 was placed in a reaction flask equipped with a stir bar. 0.2 g of C107E type acrylic weak acid cation exchange resin (Purolite) was added for adsorption purification. The adsorption temperature was 50℃, the stirring speed was 300 rpm, and the adsorption time was 10 h. The product was obtained by vacuum distillation. 9.5 mg of TEMAH was taken and a sample was prepared according to the above method. After trace metal ion content detection, the total metal ion content was 0.76 ppm, and the purity was >99.99992%. The content of each metal element in the purified product is shown below:

[0055]

[0056]

[0057] In this embodiment, the same C107E type acrylic weakly acidic cation exchange resin as in Example 34 was used as the adsorbent, but the adsorption conditions were changed, including increasing the adsorption temperature to 50°C and shortening the adsorption time to 10 hours. Although the total metal ion content of the purified product was 0.76 ppm and the purity was >99.99992%, which was an increase compared to 0.58 ppm in Example 34, it still maintained a high purity.

[0058] Examples 36-37

[0059] The purification was carried out under the same experimental conditions as in Example 33, using silica gel, ZSM-5 molecular sieve, and activated carbon as adsorbents, respectively, as follows:

[0060] 33 ZSM-5 molecular sieve 20.84 34 Activated carbon 26.77

[0061] In these two examples, silica gel and ZSM-5 molecular sieve were used as adsorbents for purification, respectively. The results showed that the total ion content using ZSM-5 molecular sieve was 20.84 ppm, and the total ion content using activated carbon was 26.77 ppm. Both results are higher than the purification effects using crown ether modified silica gel (Example 33) and C107E type acrylic weak acid cation exchange resin (Examples 34 and 35). This indicates that crown ether modified silica gel, C107E type acrylic weak acid cation exchange resin, silica gel, ZSM-5 molecular sieve, and activated carbon are all effective in removing impurity metal ions from TEMAH.

[0062] Ion content test of the initial product obtained by distillation in Comparative Example 1

[0063] Take 25.0 mg of tetra(methylethylamino)hafnium obtained from the initial distillation in Example 1, prepare a sample according to the above method, and after trace metal ion content detection, the total ion content is 2858 ppm. The content of each metal element in the product is shown below:

[0064]

[0065]

[0066] Comparative Example 1 reveals the limitations of existing tetra(methylethylamino)hafnium production technologies, particularly in purity control. The tetra(methylethylamino)hafnium obtained from the initial distillation has an ion content as high as 2858 ppm and contains various metallic elements, which is far from meeting the stringent purity requirements for precursor materials in the integrated circuit field. Existing technologies clearly cannot solve this problem, and there is an urgent need to develop new, efficient, and safe methods for producing tetra(methylethylamino)hafnium.

[0067] Data from the combined embodiments and comparative examples demonstrate that the present invention not only solves the key problem of improving purity in the production process of tetra(methylethylamino)hafnium, but also greatly enhances the feasibility and economic benefits of its industrial production. This is crucial for meeting the rapidly developing needs of the integrated circuit industry, and also brings significant practical implications for promoting technological progress in the semiconductor industry.

[0068] The above description, in conjunction with specific preferred embodiments of the present invention, further illustrates the invention and should not be construed as limiting the scope of the invention to these descriptions. Any modifications or alterations made by those skilled in the art without departing from the technical scope of the invention will be considered to be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing tetra(methylethylamino)hafnium, characterized in that, Includes the following steps: Under anhydrous, oxygen-free, and dust-free conditions at -30 to 10°C, hafnium tetrachloride and N-ethylmethylamine undergo a complexation reaction in an organic solvent for 1–5 hours, with a molar ratio of N-ethylmethylamine to hafnium tetrachloride of 4.4–5.8:

1. Subsequently, an n-BuLi solution is slowly added to initiate a lithium-hydrogen exchange reaction with N-ethylmethylamine, with a molar ratio of n-BuLi to hafnium tetrachloride of 4.4–5.8:

1. The reaction lasts for 2–12 hours. The reaction temperature is then increased, causing a nucleophilic reaction between lithium methyl ethylamino and hafnium tetrachloride. The reaction lasts for 16–72 hours. The solid is removed by centrifugation, followed by concentration and solvent removal. The process also includes removing metal ion impurities using an adsorbent. The adsorbent is crown ether modified silica gel with the following structural formula: The adsorption temperature is 20~50℃, and the adsorption residence time is 10~24h; the amount of adsorbent used is 0.2~0.6g per milliliter of tetra(methylethylamino)hafnium.

2. The method according to claim 1, characterized in that, The molar ratio of N-ethylmethylamine to hafnium tetrachloride is 4.4–5.4:

1.

3. The method according to claim 1, characterized in that, The solvent of the n-BuLi solution is selected from at least one of n-hexane, n-heptane, and cyclohexane; the concentration of the n-BuLi solution is 1.5–3 mol / L.

4. The method according to claim 1, characterized in that, The n-BuLi was added at a rate of 0.5–5 mL / min.

5. The method according to claim 1, characterized in that, The organic solvent is an alkane (C). n H 2n+2 and / or ethers, where n is any integer selected from 5 to 8.

6. The method according to claim 1, characterized in that, The reaction temperature for the lithium hydrogen exchange is -30 to -10°C; the temperature for the nucleophilic reaction is 50 to 65°C.

7. The method according to claim 1, characterized in that, The tetra(methylethylamino)hafnium product prepared by this method has a purity ≥99.99992% and a total metal ion content not exceeding 0.76 ppm.

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