Titanium precursors, methods of making and using the same

Abstract

This invention relates to a titanium precursor, its preparation method, and its application. The preparation method of the titanium precursor includes the following steps: under a protective atmosphere, titanium tetrachloride, ethylene glycol, and dialkylamine are reacted first, and then cyclopentadiene is added to continue the reaction to prepare the titanium precursor; the structural formula of the titanium precursor is as follows: Among them, R 1 and R 2 Each component is an alkyl group. The above-described method for preparing titanium precursors ensures high purity while being easy to synthesize industrially and highly safe.

Description

Titanium precursors, their preparation methods and applications Technical Field

[0001] This invention relates to the field of semiconductor materials, and in particular to a titanium precursor, its preparation method, and its application. Background Technology

[0002] Nanoscale titanium dioxide (TiO2) films possess many excellent physical properties, such as high dielectric constant, high thermal conductivity, strong resistance to radiation damage, strong resistance to alkali ion penetration, and good transparency over a wide wavelength range. Therefore, nanoscale titanium dioxide films have wide applications in microelectronics, information technology, sensors, and optics. Traditional preparation methods mainly include electroplating, thermal oxidation, chemical vapor deposition, and physical vapor deposition, but these methods generally suffer from drawbacks such as low repeatability, poor film uniformity, and complex fabrication processes. Atomic layer deposition (ALD), as a cutting-edge nanostructure manufacturing technology, forms smooth, uniform, and controllable high-quality films through ordered, self-limiting saturated chemical reactions on the substrate surface. Its high repeatability makes it widely applicable in microelectronics, optical thin films, and nanotechnology.

[0003] Furthermore, with the development of the very large-scale integrated circuit (VLSI) industry, more stringent requirements have been placed on the properties of semiconductor materials and their fabrication processes. The process of obtaining oxide thin films using ALD technology typically involves first introducing a gaseous precursor, which then undergoes a chemical reaction on the wafer surface. For successful production, an ideal precursor needs to possess the following characteristics: sufficient reactivity, sufficient stability to ensure reaction safety, suitable vapor pressure, and high precursor purity. Since the purity of the precursor is crucial to the performance of the thin film in atomic layer deposition (ALD), the semiconductor industry has extremely stringent requirements for precursor purity, generally requiring a metal purity of 4N or higher to ensure that the resulting thin film does not lead to device problems such as current leakage and threshold voltage drift.

[0004] Commonly used precursor sources for preparing TiO2 thin films via atomic layer deposition include titanium tetrachloride (40℃ / 25mmHg), tetrabutyl titanate (142℃ / 0.1mmHg), titanium tetraisopropoxide (58℃ / 1mmHg), tetradimethylaminotitanium (50℃ / 0.1mmHg), tetradiethylaminotitanium (112℃ / 0.1mmHg), and tetramethylethylaminotitanium (80℃ / 0.1mmHg). On the one hand, these high-purity precursor sources are expensive and mostly need to be imported. On the other hand, conventional methods for preparing some precursors, such as tetradimethylaminotitanium, require n-butyllithium, which is an extremely dangerous chemical reagent that spontaneously combusts when exposed to air, posing a significant safety hazard. Summary of the Invention

[0005] Therefore, it is necessary to provide a titanium precursor that is easy to synthesize and has high safety while ensuring high purity, as well as its preparation method.

[0006] In addition, it is necessary to provide an application of the aforementioned titanium precursor.

[0007] A method for preparing a titanium precursor, characterized by comprising the following steps:

[0008] Under a protective atmosphere, titanium tetrachloride, ethylene glycol and dialkylamine are reacted first, and then cyclopentadiene is added to continue the reaction to prepare a titanium precursor.

[0009] The structural formula of the titanium precursor is as follows:

[0010] R1 and R2 are each independently an alkyl group.

[0011] In one embodiment, the dialkylamine is selected from one or more of dimethylamine, diethylamine, and methyl ethylamine.

[0012] In one embodiment, the step of reacting titanium tetrachloride, ethylene glycol and dialkylamine includes: adding ethylene glycol and dialkylamine to an anhydrous solvent containing titanium tetrachloride at -15°C to 0°C, and then refluxing for 3 to 5 hours after the addition is completed.

[0013] In one embodiment, the anhydrous solvent includes alkane solvents.

[0014] In one embodiment, the molar ratio of the titanium tetrachloride, the ethylene glycol, and the dialkylamine is 1:(0.4-0.6):(7-8).

[0015] In one embodiment, the step of adding cyclopentadiene to continue the reaction includes: adding the cyclopentadiene to the reaction system at -15°C to 0°C, and continuing the reaction at 10°C to 30°C for 12 to 18 hours after the addition is completed.

[0016] In one embodiment, after the reaction is complete, the process further includes: removing the solvent and distilling under reduced pressure.

[0017] In one embodiment, the molar ratio of titanium tetrachloride to cyclopentadiene is 1:(1 to 1.3).

[0018] A titanium precursor, the structural formula of which is as follows:

[0019]

[0020] R1 and R2 are each an alkyl group.

[0021] The application of a titanium precursor in the preparation of titanium dioxide thin films, wherein the titanium precursor is prepared by the above-described method for preparing titanium precursors or the titanium precursor is the above-described titanium precursor.

[0022] The above-mentioned method for preparing titanium precursors involves reacting titanium tetrachloride, ethylene glycol, and dialkylamine under a protective atmosphere, followed by the addition of cyclopentadiene to continue the reaction. This method is simple to synthesize, uses readily available raw materials, avoids the use of n-butyllithium required in traditional processes, and offers high safety, making it suitable for industrial-scale production. Furthermore, experiments have demonstrated that the titanium precursors prepared by this method have high metal purity, meeting the requirements of ALD technology. Attached Figure Description

[0023] Figure 1 is a schematic diagram of the titanium dioxide thin film preparation process in some embodiments of the present invention. Detailed Implementation

[0024] To facilitate understanding of the present invention, a more comprehensive description of the invention will be provided below in conjunction with specific embodiments. Preferred embodiments of the invention are given in the specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0025] 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 invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0026] In this invention, "one or several" refers to any one, any two, or any two or more of the listed items. "Several" refers to any two or more.

[0027] In this invention, unless otherwise specified, all percentage concentrations refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0028] The terms "preferred," "more preferably," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0029] When a numerical range is disclosed in this invention, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Further, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Moreover, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed in this invention should be understood to include any and all subranges to which they are incorporated.

[0030] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0031] The terms "comprising" and "having," and any variations thereof, used in embodiments of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or components inherent to such processes, methods, products, or devices.

[0032] In this invention, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0033] As described in the background section, traditional high-purity titanium precursors are expensive, and their preparation may involve the use of highly hazardous chemical reagents such as n-butyllithium. Furthermore, commercially available n-butyllithium is typically diluted in alkane solvents, generating substantial amounts of waste liquid during its use. Therefore, this invention provides a titanium precursor and its preparation method that are simple to synthesize, have high reaction safety, good stability, and high purity.

[0034] A method for preparing a titanium precursor according to an embodiment of the present invention includes the following steps:

[0035] Under a protective atmosphere, titanium tetrachloride, ethylene glycol, and dialkylamine are reacted first, and then cyclopentadiene is added to continue the reaction to prepare a titanium precursor.

[0036] In some embodiments, the molar ratio of titanium tetrachloride to ethylene glycol is 1:(0.4 to 0.6). In a specific example, the molar ratio of titanium tetrachloride to ethylene glycol is 1:0.4, 1:0.42, 1:0.45, 1:0.48, 1:0.5, 1:0.52, 1:0.55, 1:0.58, 1:0.6, or a range of any two of these values.

[0037] In some embodiments, the molar ratio of titanium tetrachloride to dialkylamine is 1:(7-8). In a specific example, the molar ratio of titanium tetrachloride to dialkylamine is 1:7, 1:7.1, 1:7.2, 1:7.3, 1:7.4, 1:7.5, 1:7.6, 1:7.7, 1:7.8, 1:7.9, 1:8, or any range of two of these values.

[0038] In some embodiments, the dialkylamine is selected from one or more of dimethylamine, diethylamine, and methyl ethylamine.

[0039] In some embodiments, the reaction time in the step of reacting titanium tetrachloride, ethylene glycol and dialkylamine is 3h to 5h.

[0040] In some embodiments, the step of reacting titanium tetrachloride, ethylene glycol, and dialkylamine includes: adding ethylene glycol and dialkylamine to an anhydrous solvent containing titanium tetrachloride at -15°C to 0°C, and then refluxing the reaction for 3 to 5 hours after the addition is complete. Since dialkylamine has a low boiling point and is usually stored at low temperatures, if the temperature at which it is added is too high, the dialkylamine will evaporate as a gas, resulting in inaccurate amounts of dialkylamine added. Therefore, in this embodiment, it is preferable to add ethylene glycol and dialkylamine to an anhydrous solvent containing titanium tetrachloride at -15°C to 0°C.

[0041] In some embodiments, the anhydrous solvent includes alkane solvents. In a specific example, the anhydrous solvent may be, but is not limited to, n-hexane, n-pentane, n-heptane, etc. The use of an anhydrous solvent serves two purposes: firstly, to avoid the hydrolysis of titanium tetrachloride; and secondly, the fact that the anhydrous solvent is primarily an alkane solvent, and the raw material is also an alkane liquid of dialkylamine, ensures that the reaction system uses the same type of solvent, which facilitates industrial recycling.

[0042] In some embodiments, the protective atmosphere may be, but is not limited to, a nitrogen atmosphere or an argon atmosphere. In a specific example, the protective atmosphere is high-purity nitrogen or high-purity argon.

[0043] In some embodiments, the molar ratio of titanium tetrachloride to cyclopentadiene is 1:(1 to 1.3). In a specific example, the molar ratio of titanium tetrachloride to cyclopentadiene is 1:1, 1:1.02, 1:1.05, 1:1.08, 1:1.1, 1:1.12, 1:1.15, 1:1.18, 1:1.2, 1:1.22, 1:1.25, 1:1.28, 1:1.3, or a range of any two of these values.

[0044] In some embodiments, the step of adding cyclopentadiene to continue the reaction includes: adding cyclopentadiene to the reaction system at -15°C to 0°C, and continuing the reaction at 10°C to 30°C for 12h to 18h after the addition is completed.

[0045] In some embodiments, the temperature of the reaction system is -15°C to 0°C during the addition of cyclopentadiene to the reaction system. In a specific example, the temperature of the reaction system is -15°C, -14°C, -12°C, -10°C, -8°C, -6°C, -5°C, -4°C, -2°C, 0°C, or any combination of these values. If the reaction temperature is too high, the cyclopentadiene monomer will polymerize; therefore, in this embodiment, cyclopentadiene is added at a low temperature.

[0046] Furthermore, after the reaction is complete, the process also includes the steps of removing the solvent and distilling under reduced pressure.

[0047] In some embodiments, the preparation method of the titanium precursor includes the following steps: Ethylene glycol and dialkylamine are added to an anhydrous solvent containing titanium tetrachloride at -15°C to 0°C, and the mixture is refluxed for 3 to 5 hours after the addition is complete. After the reaction is complete, the mixture is filtered, and the filtrate is cooled to -15°C to 0°C. Cyclopentadiene is added to the filtrate under a protective atmosphere, and the reaction is continued at 10°C to 30°C for 12 to 18 hours after the addition is complete. After the reaction is complete, the solvent is removed, and the mixture is distilled under reduced pressure to prepare the titanium precursor.

[0048] The synthetic route for preparing the above-mentioned titanium precursor is shown below:

[0049]

[0050] The target product can be obtained by reacting titanium tetrachloride, ethylene glycol, and dialkylamine first, followed by the addition of cyclopentadiene. However, if ethylene glycol, dialkylamine, and cyclopentadiene are added to titanium tetrachloride simultaneously, the target product cannot be obtained; instead, titanium dichloropentane is produced. In the above reaction, ethylene glycol participates in the reaction. If ethanol or propylene glycol is used instead of ethylene glycol, ethanol, being more reactive, will preferentially yield tetraethyl titanate, while 1,3-propanediol, being less reactive, will not be detected. Similarly, dialkylamine also participates in the reaction and is involved in the construction of the target product molecule. However, if organic amines such as n-propylamine or n-butylamine are used, they are only used for acid binding, i.e., forming hydrochloride salts, and cannot participate in molecule construction, thus failing to obtain the target product.

[0051] The above-mentioned method for preparing titanium precursors has at least the following advantages:

[0052] (1) The above-mentioned method for preparing titanium precursor involves reacting titanium tetrachloride, ethylene glycol, and dialkylamine under a protective atmosphere, followed by the addition of cyclopentadiene to continue the reaction. This method is simple to synthesize and uses readily available raw materials, avoiding the use of n-butyllithium required in traditional processes, thus ensuring high safety and suitability for industrial-scale production. Furthermore, experiments have shown that the titanium precursor obtained by the above-mentioned method has high metal purity, meeting the requirements of ALD technology.

[0053] (2) The above-mentioned method for preparing titanium precursors has a mild reaction process, low energy consumption, no need for intermediate synthesis, simple post-processing, and high product yield, making it suitable for industrial-scale production.

[0054] (3) The titanium precursor prepared by the above method has a suitable vapor pressure and good stability.

[0055] The present invention also provides a titanium precursor according to one embodiment, with the following structural formula:

[0056]

[0057] R1 and R2 are each an alkyl group.

[0058] Furthermore, R1 and R2 are each independently a C1 to C6 alkyl group. In one specific example, R1 and R2 are both methyl; in another specific example, R1 and R2 are both ethyl; and in yet another specific example, R1 is methyl and R2 is ethyl.

[0059] The aforementioned titanium precursor has high purity, suitable vapor pressure, and good stability, and can be used to prepare titanium dioxide thin films using ALD technology.

[0060] The present invention also provides an embodiment of the application of a titanium precursor in the preparation of titanium dioxide thin films.

[0061] In some embodiments, the application of titanium precursors in the preparation of titanium dioxide thin films includes: cleaning and drying an undoped silicon substrate and placing it in an atomic layer deposition (ALD) chamber; adjusting the ALD chamber to 230°C–250°C and evacuating it; heating the titanium source to 150°C; and using high-purity argon gas to introduce evaporated titanium source molecules into the ALD chamber (pulse time 0.2 s). After the titanium source molecules have finished being introduced, argon gas is continued to be introduced for 10 s to clean residual titanium source and reaction byproducts. Then, oxygen source H2O is pulsed into the ALD chamber using argon gas (pulse time 0.3 s). After the pulsed H2O molecules have finished being introduced, argon gas is continued to be introduced for 10 s to clean residual H2O molecules and reaction byproducts. The above process is repeated to prepare a titanium dioxide thin film.

[0062] Please refer to Figure 1 for a schematic diagram of the specific preparation process.

[0063] In some embodiments, during the cleaning of the undoped silicon substrate, acetone, anhydrous ethanol, deionized water, RCA solution, deionized water and anhydrous ethanol are used for ultrasonic cleaning in sequence.

[0064] In some embodiments, nitrogen gas is used to dry the product during the drying process.

[0065] Experiments have shown that the titanium dioxide thin films prepared above are of good quality and have high uniformity.

[0066] To make the objectives and advantages of the present invention clearer, the preparation method and effects of the titanium precursor of the present invention are further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and should not be used to limit the present invention. Unless otherwise specified, the following embodiments do not include components other than unavoidable impurities. Unless otherwise specified, the drugs and instruments used in the embodiments are conventional choices in the art. Experimental methods in the embodiments that do not specify specific conditions are implemented according to conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.

[0067] It is understood that the instruments and raw materials used in the following embodiments are relatively specific, and may not be limited to these in other specific embodiments; the weight of the relevant components mentioned in the embodiments of this invention may not only refer to the specific content of each component, but also to the weight ratio between the components. Therefore, as long as the content of the relevant components is scaled up or down proportionally according to the embodiments of this invention, it is within the scope disclosed in the embodiments of this invention.

[0068] Example 1

[0069] This embodiment provides a method for preparing a titanium precursor, which specifically includes the following steps:

[0070] Under a nitrogen atmosphere, titanium tetrachloride (37.9 g, 0.2 mol) and n-hexane were added to a 2000 mL Schlenk flask. The mixture was cooled to approximately -10 °C, and ethylene glycol (6.2 g, 0.1 mol) was added dropwise. Subsequently, a 20% (w / w) dimethylamine solution in n-hexane (315.6 g, 1.4 mol) was added dropwise. After reflux for 3 hours, the mixture was slowly brought back to room temperature and filtered. The filtrate was then cooled to -10 °C again, and freshly depolymerized cyclopentadiene (13.2 g, 0.2 mol) was slowly added under nitrogen protection. The mixture was brought back to room temperature and stirred for 12 hours. The solvent was removed, and the residue was distilled under reduced pressure (64 °C / 0.1 mm Hg) to obtain 37.9 g of the titanium precursor Ti1 in this example, with a yield of 82%. The characterization data of the titanium precursor are as follows:

[0071] 1 HNMR(C6D6):6.04(s,10H),3.60(t,4H),2.96(s,24H).

[0072] Elemental analysis of the product yielded the following results: theoretical values: C: 51.96, H: 8.29, N: 12.12; measured values: C: 51.84, H: 8.37, N: 12.51.

[0073] The metal purity was determined to be 5N using ICP-MS analysis.

[0074] Example 2

[0075] This embodiment provides a method for preparing a titanium precursor, which is similar to the preparation method in Example 1, except that the amount of dimethylamine n-hexane solution in Example 1 is changed to 337.8 grams. The specific preparation process is as follows:

[0076] Under a nitrogen atmosphere, titanium tetrachloride (37.9 g, 0.2 mol) and n-hexane were added to a 2000 mL Schlenk flask. The mixture was cooled to approximately -10 °C, and ethylene glycol (6.2 g, 0.1 mol) was added dropwise. Subsequently, a 20% (w / w) dimethylamine solution in n-hexane (337.8 g, 1.5 mol) was added dropwise. After reflux for 3 hours, the mixture was slowly brought back to room temperature and filtered. The filtrate was cooled to -10 °C again, and freshly depolymerized cyclopentadiene (13.2 g, 0.2 mol) was slowly added under nitrogen protection. The mixture was brought back to room temperature and stirred for 12 hours. The solvent was removed, and the residue was distilled under reduced pressure to obtain 40.7 g of the titanium precursor Ti1 in this embodiment, with a yield of 88%.

[0077] Example 3

[0078] This embodiment provides a method for preparing a titanium precursor, which is similar to the preparation method in Example 2, except that the amount of cyclopentadiene in Example 2 is changed to 16.5 grams. The specific process is as follows:

[0079] Under a nitrogen atmosphere, titanium tetrachloride (37.9 g, 0.2 mol) and n-hexane were added to a 2000 mL Schlenk flask. The mixture was cooled to approximately -10 °C, and ethylene glycol (6.2 g, 0.1 mol) was added dropwise. Subsequently, a 20% dimethylamine n-hexane solution (337.8 g, 1.5 mol) was added dropwise. After reflux for 3 hours, the mixture was slowly brought back to room temperature and filtered. The filtrate was cooled to -10 °C again, and freshly depolymerized cyclopentadiene (16.5 g, 0.25 mol) was slowly added under nitrogen protection. The mixture was brought back to room temperature and stirred for 12 hours. The solvent was removed, and the residue was distilled under reduced pressure to obtain 42.5 g of the titanium precursor Ti1 in this embodiment, with a yield of 92%.

[0080] Example 4

[0081] This embodiment provides a method for preparing a titanium precursor, which is similar to the preparation method in Example 3, except that the dimethylamine in Example 3 is replaced with an equivalent amount of diethylamine. The specific process is as follows:

[0082] Under a nitrogen atmosphere, titanium tetrachloride (37.9 g, 0.2 mol) and n-hexane were added to a 2000 mL Schlenk flask. The mixture was cooled to approximately -10 °C, and ethylene glycol (6.2 g, 0.1 mol) was added dropwise, followed by diethylamine (109.6 g, 1.5 mol). After reflux for 3 hours, the mixture was slowly brought back to room temperature and filtered. The filtrate was then cooled to -10 °C again, and freshly depolymerized cyclopentadiene (16.5 g, 0.25 mol) was slowly added under nitrogen protection. The mixture was brought back to room temperature and stirred for 12 hours. The solvent was removed, and the residue was distilled under reduced pressure (79 °C / 0.1 mm Hg) to obtain 51.1 g of the titanium precursor Ti2 in this example, with a yield of 89%. The characterization data of the titanium precursor Ti2 in this example are as follows:

[0083] 1 HNMR(C6D6):6.04(s,10H),3.61(t,4H),3.58(q,16H),1.12(t,24H).

[0084] Elemental analysis of the product yielded the following results: theoretical values: C: 58.54, H: 9.47, N: 9.75; measured values: C: 58.12, H: 9.21, N: 9.69.

[0085] The metal purity was determined to be 5N using ICP-MS analysis.

[0086] Example 5

[0087] This embodiment provides a method for preparing a titanium precursor, which is similar to the preparation method in Example 3, except that the dimethylamine in Example 3 is replaced with an equivalent amount of methyl ethylamine. The specific process is as follows:

[0088] Under a nitrogen atmosphere, titanium tetrachloride (37.9 g, 0.2 mol) and n-hexane were added to a 2000 mL Schlenk flask. The mixture was cooled to approximately -10 °C, and ethylene glycol (6.2 g, 0.1 mol) was added dropwise, followed by methyl ethylamine (88.6 g, 1.5 mol). After reflux for 3 hours, the mixture was slowly brought back to room temperature and filtered. The filtrate was then cooled again to -10 °C, and freshly depolymerized cyclopentadiene (16.5 g, 0.25 mol) was slowly added under nitrogen protection. The mixture was brought back to room temperature and stirred for 12 hours. The solvent was removed, and the residue was distilled under reduced pressure (71 °C / 0.1 mm Hg) to obtain 47.2 g of the titanium precursor Ti3 in this example, with a yield of 91%. The characterization data of the titanium precursor Ti3 in this example are as follows:

[0089] 1 HNMR(C6D6):6.03(s,10H),3.59(t,4H),3.45(q,8H),3.13(s,12H),1.12(t,12H).

[0090] Elemental analysis of the product yielded the following results: theoretical values: C: 55.61, H: 8.94, N: 10.81; measured values: C: 54.92, H: 8.78, N: 10.44.

[0091] The metal purity was determined to be 5N using ICP-MS analysis.

[0092] Comparative Example 1

[0093] This comparative example provides a method for preparing a titanium precursor. Unlike Example 3, this comparative example only changes the order of feeding, using a one-pot feeding method. The specific process is as follows:

[0094] Under a nitrogen atmosphere, titanium tetrachloride (37.9 g, 0.2 mol), 400 mL of n-hexane, ethylene glycol (6.2 g, 0.1 mol), and a 20% dimethylamine n-hexane solution (337.8 g, 1.5 mol) were added sequentially to a 2000 mL Schlenk flask. The mixture was cooled to -10 °C, and freshly depolymerized cyclopentadiene (16.5 g, 0.25 mol) was slowly added under nitrogen protection. The mixture was then brought back to room temperature and stirred for 12 hours. The solvent was removed, and the residue was distilled under reduced pressure. No product was obtained, but the presence of titanium dichlorocerocene was detected by NMR.

[0095] As can be seen from the comparison between Comparative Example 1 and Example 3, changing the feeding order and using a one-pot feeding method cannot obtain the target product.

[0096] Comparative Example 2

[0097] This comparative example provides a method for preparing a titanium precursor, which is similar to the preparation method in Example 3, except that the ethylene glycol in Example 3 is replaced with an equivalent amount of ethanol. The specific preparation process is as follows:

[0098] Under a nitrogen atmosphere, titanium tetrachloride (37.9 g, 0.2 mol) and 400 mL of n-hexane were added to a 2000 mL Schlenk flask. The mixture was cooled to approximately -10 °C, and ethanol (4.6 g, 0.1 mol) was added dropwise. Subsequently, a 20% dimethylamine solution in n-hexane (337.8 g, 1.5 mol) was added dropwise. After reflux for 3 hours, the mixture was slowly brought back to room temperature and filtered. The filtrate was cooled to -10 °C again, and freshly depolymerized cyclopentadiene (16.5 g, 0.25 mol) was slowly added under nitrogen protection. The mixture was brought back to room temperature and stirred for 12 hours. The solvent was removed, and the residue was distilled under reduced pressure, yielding only a small amount of liquid. NMR analysis revealed that the liquid was tetraethyl titanate, which was not the target product.

[0099] Comparative Example 3

[0100] This comparative example provides a method for preparing a titanium precursor, similar to the method in Example 3, except that the ethylene glycol in Example 3 is replaced with an equivalent amount of 1,3-propanediol. The specific process is as follows:

[0101] Under a nitrogen atmosphere, titanium tetrachloride (37.9 g, 0.2 mol) and n-hexane were added to a 2000 mL Schlenk flask. The mixture was cooled to approximately -10 °C, and 1,3-propanediol (7.6 g, 0.1 mol) was added dropwise. Subsequently, a 20% (w / w) dimethylamine solution in n-hexane (337.8 g, 1.5 mol) was added dropwise. After reflux for 3 hours, the mixture was slowly brought back to room temperature and filtered. The filtrate was then cooled to -10 °C again, and freshly depolymerized cyclopentadiene (16.5 g, 0.25 mol) was slowly added under nitrogen protection. The mixture was brought back to room temperature and stirred for 12 hours. The solvent was then removed, yielding a slurry-like residue. The target product was not detected.

[0102] As can be seen from Comparative Examples 2 and 3, using the more reactive ethanol will preferentially yield tetraethyl titanate, while using the less reactive 1,3-propanediol will even result in the undetectable presence of the target product.

[0103] Comparative Example 4

[0104] This comparative example provides a method for preparing a titanium precursor, which is similar to the preparation method in Example 3, except that the dimethylamine in Example 3 is replaced with an equivalent amount of n-propylamine. The specific process is as follows:

[0105] Under a nitrogen atmosphere, titanium tetrachloride (37.9 g, 0.2 mol) and n-hexane were added to a 2000 mL Schlenk flask. The flask was cooled to approximately -10 °C, and ethylene glycol (6.2 g, 0.1 mol) was added dropwise, followed by n-propylamine (88.7 g, 1.5 mol). The mixture was refluxed for 3 hours, then slowly brought to room temperature and filtered. The filtrate was cooled to -10 °C again, and freshly depolymerized cyclopentadiene (16.5 g, 0.25 mol) was slowly added under nitrogen protection. The mixture was brought to room temperature and stirred for 12 hours. The solvent was removed, and the residue was distilled under reduced pressure. The target product was not detected.

[0106] Example 6

[0107] This embodiment provides a method for preparing a titanium dioxide thin film, including the following steps:

[0108] Undoped silicon substrates were sequentially ultrasonically cleaned with acetone, anhydrous ethanol, deionized water, RCA solution, deionized water, and anhydrous ethanol, and then dried with nitrogen. After drying, the substrates were placed in an atomic layer deposition (ALD) chamber, and the ALD chamber was adjusted from room temperature to 230–250°C and evacuated. The titanium precursor Ti1 prepared in Example 3 was heated to 150°C, and the evaporated precursor molecules were introduced into the ALD chamber using high-purity argon gas (pulse time 0.2 s). After the titanium precursor molecules were introduced, argon gas was continued to be introduced for 10 s to clean residual titanium precursor and reaction byproducts. H2O was pulsed into the ALD chamber using argon gas (pulse time 0.3 s). After the pulsed H2O molecules were introduced, argon gas was continued to be introduced for 10 s to clean residual H2O molecules and reaction byproducts. The above process was repeated for 100 cycles to obtain a good titanium dioxide film. The thickness of the titanium dioxide film was measured to be 12.3 nm using an ellipsometry, and the film's inhomogeneity was 0.90%.

[0109] Titanium dioxide thin films were prepared by performing the above deposition operation using the titanium precursor Ti2 prepared in Example 4 and the titanium precursor Ti3 prepared in Example 5, respectively. The thicknesses of the obtained films were 11.6 nm and 12.1 nm, respectively, and the non-uniformity of the films were 0.96% and 1.21%, respectively.

[0110] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] The above-described embodiments are merely illustrative of several implementation methods of the present invention, facilitating a detailed understanding of the technical solutions of the present invention, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided by the present invention through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this invention patent should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A method for preparing a titanium precursor, characterized in that, The process includes the following steps: Under a protective atmosphere, titanium tetrachloride, ethylene glycol, and a dialkylamine are reacted first, and then cyclopentadiene is added to continue the reaction to prepare a titanium precursor; the dialkylamine is selected from any one or more of dimethylamine, diethylamine, and methyl ethylamine; the structural formula of the titanium precursor is as follows: Where R1 and R2 are both methyl; or, R1 and R2 are both ethyl; or, R1 is methyl and R2 is ethyl.

2. The method for preparing the titanium precursor according to claim 1, characterized in that, In the step of reacting titanium tetrachloride, ethylene glycol and dialkylamine, the reaction time is 3h~5h.

3. The method for preparing the titanium precursor according to claim 1, characterized in that, The step of reacting titanium tetrachloride, ethylene glycol and dialkylamine includes: adding ethylene glycol and dialkylamine to an anhydrous solvent containing titanium tetrachloride at -15℃ to 0℃, and refluxing for 3h to 5h after the addition is completed.

4. The method for preparing the titanium precursor according to claim 3, characterized in that, The anhydrous solvent includes alkane solvents.

5. The method for preparing the titanium precursor according to any one of claims 1 to 4, characterized in that, The molar ratio of titanium tetrachloride, ethylene glycol and dialkylamine is 1:(0.4~0.6):(7~8).

6. The method for preparing the titanium precursor according to any one of claims 1 to 4, characterized in that, The step of adding cyclopentadiene to continue the reaction includes: adding the cyclopentadiene to the reaction system at -15℃ to 0℃, and continuing the reaction at 10℃ to 30℃ for 12h to 18h after the addition is completed.

7. The method for preparing the titanium precursor according to claim 6, characterized in that, After the reaction is complete, the steps also include: removing the solvent and distilling under reduced pressure.

8. The method for preparing the titanium precursor according to any one of claims 1 to 4 and 7, characterized in that, The molar ratio of titanium tetrachloride to cyclopentadiene is 1:(1~1.3).

9. A titanium precursor, characterized in that, The structural formula of the titanium precursor is as follows: Where R1 and R2 are both methyl; or R1 and R2 are both ethyl; or R1 is methyl and R2 is ethyl.

10. The application of a titanium precursor in the preparation of titanium dioxide thin films, characterized in that, The titanium precursor is prepared by the method for preparing titanium precursor according to any one of claims 1 to 8, or the titanium precursor is the titanium precursor according to claim 9.

Images