A hafnium oxide thin film, a preparation method thereof, and an application thereof

Abstract

The present invention belongs to the field of semiconductors, and in particular to a hafnium oxide film and its preparation method and application. The preparation method of the hafnium oxide film comprises the following steps: hafnium tetrachloride and cyclopentadiene are subjected to coordination reaction under the conditions of an organic solvent and an auxiliary agent, and then cyclopentadiene hafnium trichloride is obtained by seed induced crystallization method; dimethylamine is added for substitution reaction, and then cyclopentadiene tris (dimethylamino) hafnium is obtained by vacuum distillation crystallization; cyclopentadiene tris (dimethylamino) hafnium is introduced into the reaction chamber of PE-MOCVD equipment, and metal organic chemical vapor deposition is carried out with plasma gas at a deposition temperature, so that cyclopentadiene tris (dimethylamino) hafnium precursor generates hafnium oxide film on the substrate surface; the auxiliary agent is a strong base weak acid salt. The preparation method provided by the present invention can obtain a hafnium oxide film with high purity, high yield and high dielectric constant.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductors, and in particular relates to a hafnium oxide thin film and a preparation method and application thereof. Background Art

[0002] Metal-organic precursor compounds are high-value-added products and are essential materials in the electronics industry. They are primarily used in semiconductor storage, capacitor electrodes for logic chips, gate transition layers, and isolation materials. In recent years, Group IV metals such as hafnium (Hf), zirconium (Zr), or titanium (Ti) have been widely used in the preparation of high-dielectric-constant thin-film materials due to their relatively wide bandgap energy, high Si integration, and compatibility. Among them, hafnium metal, due to its unique physical and chemical properties, has excellent hafnium oxide films with high dielectric constants, low losses, and good thermal stability. Therefore, they have great potential for application in semiconductor fields such as gate dielectrics, ferroelectric materials, and optical films in integrated circuits.

[0003] The commonly used methods for preparing hafnium oxide thin films in the prior art include: preparing hafnium oxide thin films by chemical vapor deposition (CVD), plasma chemical vapor deposition (PE-CVD), atomic layer deposition (ALD), plasma atomic layer deposition (PE-ALD), metal organic chemical vapor deposition (MOCVD) and other process technologies from an organic precursor compound of metallic hafnium. Among them, ALD technology can provide significant advantages in the preparation of hafnium oxide thin films, such as precise thickness control, uniform film quality, low-temperature deposition, high purity and low impurity content; CVD technology provides high deposition rate, good uniformity, applicability to large-diameter substrates, controllability, scalability, diverse precursor selection, low energy consumption and environmental friendliness, and suitability for deposition of complex structures when preparing hafnium oxide thin films. The above advantages make ALD and CVD ideal choices for preparing high-performance hafnium oxide thin films.

[0004] In the preparation process of hafnium oxide film, the composition and properties of the organic precursor compound of metal hafnium are also key factors affecting the performance (purity, output, dielectric constant) of hafnium oxide film. Among them, cyclopentadiene tris (dimethylamino) hafnium is widely considered to be the preferred metal organic precursor compound for preparing high-performance hafnium oxide film due to its good stability and reactivity. The current preparation method of cyclopentadiene tris (dimethylamino) hafnium is usually to first synthesize tetrakis (dimethylamino) hafnium by hafnium tetrachloride and dimethylamine lithium salt, and then add cyclopentadiene to react to obtain cyclopentadiene tris (dimethylamino) hafnium. This preparation method needs to introduce impurity metal elements and has side reactions, resulting in low yield and purity. It needs to be purified multiple times to obtain a product with higher purity, which increases the complexity and cost of the process. In addition, the purity, yield and dielectric constant of hafnium oxide films prepared using cyclopentadienyltri(dimethylamino)hafnium as a precursor material based on existing technologies (such as CVD, ALD, etc.) have limited improvement effects, which to some extent limits its application in the semiconductor field. Summary of the Invention

[0005] One of the purposes of the present invention is to solve the problem of low yield and purity caused by the need to introduce impurity metal elements and the existence of side reactions when preparing cyclopentadienyltris(dimethylamino)hafnium in the prior art, and to obtain a high-purity, high-yield and high-dielectric-constant hafnium oxide film using cyclopentadienyltris(dimethylamino)hafnium as a precursor. A preparation method for obtaining a high-purity, high-yield and high-dielectric-constant hafnium oxide film based on cyclopentadienyltris(dimethylamino)hafnium as a precursor is provided.

[0006] Specifically, the preparation method includes the following steps: S1. carrying out a coordination reaction between hafnium tetrachloride and cyclopentadiene in the presence of an organic solvent and an auxiliary agent, and then obtaining cyclopentadienyl hafnium trichloride through a seed-induced crystallization method; S2. carrying out a substitution reaction between the cyclopentadienyl hafnium trichloride prepared in step S1 and dimethylamine, and then obtaining cyclopentadienyl tris(dimethylamino) hafnium through vacuum distillation crystallization; S3. introducing the cyclopentadienyl tris(dimethylamino) hafnium prepared in step S2 as a precursor into a reaction chamber of a PE-MOCVD device, and carrying out metal organic chemical vapor deposition with plasma gas at a deposition temperature, so that the cyclopentadienyl tris(dimethylamino) hafnium precursor generates a hafnium oxide film on the surface of a substrate; the auxiliary agent is a strong base and a weak acid salt.

[0007] In a preferred embodiment, in step S1, the conditions of the coordination reaction include a temperature of 20-30° C. and a time of 10-15 h.

[0008] In a preferred embodiment, the molar ratio of hafnium tetrachloride to cyclopentadiene is 1:(1.1-3).

[0009] In a preferred embodiment, the amount of the auxiliary agent used is such that the pH value of the reaction system is 8.5-9.5.

[0010] In a preferred embodiment, in step S1, the induced crystals used in the seed induced crystallization method are selected from at least one of CpFe, CpMn, CpZrCl3, CpZrBr3, and CpZrI3.

[0011] In a preferred embodiment, the temperature of the seed induced crystallization method is 5-10°C.

[0012] In a preferred embodiment, in step S2, the conditions of the substitution reaction include a temperature of 20-30° C. and a time of 3-5 h.

[0013] In a preferred embodiment, the molar ratio of cyclopentadienyl hafnium trichloride to dimethylamine is 1:(3-5).

[0014] In a preferred embodiment, in step S2, the vacuum distillation crystallization conditions include a vacuum degree of 10 -3 -10 -5 Pa, temperature is 25-35℃.

[0015] In a preferred embodiment, in step S3, the process of the metal organic chemical vapor deposition is: (1) heating the substrate to a deposition temperature in a reaction chamber; (2) introducing cyclopentadienyltris(dimethylamino)hafnium and an inert gas into the reaction chamber; (3) introducing plasma gas into the reaction chamber to react with cyclopentadienyltris(dimethylamino)hafnium to form a hafnium oxide film; (4) introducing an inert gas to purge and remove unreacted precursors and by-products; and (5) repeating steps (2) to (4) until the deposition of the hafnium oxide film is completed.

[0016] In a preferred embodiment, the deposition temperature is 100-400°C.

[0017] In a preferred embodiment, the plasma gas is oxygen.

[0018] In a preferred embodiment, the inert gas is selected from at least one of helium, neon, argon and nitrogen.

[0019] In a preferred embodiment, the auxiliary agent is selected from at least one of sodium carbonate, potassium carbonate, sodium acetate, potassium acetate, magnesium acetate, sodium bicarbonate and sodium sulfite.

[0020] In a preferred embodiment, the organic solvent is at least one selected from n-hexane, tetrahydrofuran, diethyl ether and acetone.

[0021] A second object of the present invention is to provide a hafnium oxide thin film prepared by the above method.

[0022] A third object of the present invention is to provide applications of the hafnium oxide film in the semiconductor field.

[0023] The present invention has the following beneficial effects compared to the prior art: first, in the presence of an organic solvent and a specific auxiliary agent (a strong base and a weak acid salt), a cyclopentadiene organic ligand is coordinated with a metal center hafnium, and then a seed-induced crystallization method is used to obtain an intermediate product, cyclopentadiene hafnium trichloride; under the action of the specific auxiliary agent, the generation of by-products can be reduced, and the use of the auxiliary agent and the seed-induced crystallization method are conducive to improving the crystallization efficiency and controlling the crystal morphology and purity, thereby obtaining a high-purity, high-yield intermediate product, cyclopentadiene hafnium trichloride; dimethylamine is used as a ligand, and due to its Lewis base properties, it can replace the chloride ions of cyclopentadiene hafnium trichloride to form a coordination bond with the metal center hafnium, and then a vacuum distillation crystallization method is used to obtain a high-purity, high-yield cyclopentadiene tris (dimethylamino) hafnium; PE-MOCVD equipment is selected to prepare the hafnium oxide film, and a deposition reaction can be carried out at a lower temperature to obtain a uniform, stable, high-purity, high-yield hafnium oxide film with a high dielectric constant (K value).

[0024] Compared to the commonly used cyclopentadiene hafnium trichloride synthesis method in the prior art, which first coordinates hafnium tetrachloride with dimethylamine lithium salt, the present invention first uses cyclopentadiene and hafnium tetrachloride to coordinate, on the one hand, reducing the introduction of other metal impurities and the generation of side reactions, and on the other hand, allowing cyclopentadiene hafnium trichloride to maintain high selectivity for organic ligands in the substitution reaction with dimethylamine, thereby facilitating improving the purity and yield of the intermediate products cyclopentadiene hafnium trichloride and cyclopentadiene tris(dimethylamino) hafnium. In summary, the preparation method of the present invention can obtain a hafnium oxide film with high purity, high yield and high dielectric constant, which can meet its high application requirements in the semiconductor field. DETAILED DESCRIPTION

[0025] The method for preparing a hafnium oxide thin film based on a novel precursor material provided by the present invention comprises the following steps:

[0026] S1. The coordination reaction of hafnium tetrachloride and cyclopentadiene in the presence of an organic solvent and an additive, and then cyclopentadiene hafnium trichloride is obtained by seed-induced crystallization;

[0027] S2. The cyclopentadienyl hafnium trichloride prepared in step S1 is subjected to a substitution reaction with dimethylamine, and then crystallized by vacuum distillation to obtain cyclopentadienyl tris(dimethylamino) hafnium;

[0028] S3. The cyclopentadienyltris(dimethylamino)hafnium prepared in step S2 is introduced into the reaction chamber of the PE-MOCVD equipment as a precursor, and metal organic chemical vapor deposition is carried out with plasma gas at the deposition temperature, so that the cyclopentadienyltris(dimethylamino)hafnium precursor forms a hafnium oxide film on the surface of the substrate.

[0029] The reaction mechanism involved in the above-mentioned hafnium oxide thin film preparation method is as follows:

[0030] C5H6+HfCl4→C5H5·HfCl3+HCl

[0031] C5H5H·HfCl3+3N(CH3)2→C5H5·Hf(N(CH3)2)3+3ClCH3

[0032] In the present invention, in step S1, the conditions of the coordination reaction include a temperature of preferably 20-30°C, such as 20°C, 22°C, 25°C, 28°C, 30°C or any value therebetween. The time is preferably 10-15h, such as 10h, 11h, 12h, 13h, 14h, 15h or any value therebetween. The temperature and / or time of the coordination reaction are controlled within the above-mentioned preferred range, which is more conducive to improving the efficiency of the coordination reaction between hafnium tetrachloride and cyclopentadiene, reducing side reaction products, thereby more capable of improving the yield and purity of cyclopentadiene hafnium trichloride. The molar ratio of the hafnium tetrachloride to cyclopentadiene is preferably 1:(1.1-3), such as 1:1.1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3 or any value therebetween. The amount of the auxiliary agent used can be such that the pH value of the reaction system is 8.5-9.5.

[0033] In the present invention, in step S1, the induced crystals used in the seed-induced crystallization method are selected from at least one of CpFe, CpMn, CpZrCl3, CpZrBr3, and CpZrI3, more preferably CpZrCl3. The temperature of the seed-induced crystallization method is preferably 5-10°C, such as 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, or any value therebetween. Controlling the temperature of the seed-induced crystallization method within the above preferred range is more conducive to increasing the yield of cyclopentadienyl hafnium trichloride and the crystallization rate, thereby improving production efficiency.

[0034] In the present invention, in step S1, the order of adding the hafnium tetrachloride and cyclopentadiene can be to add both simultaneously to the organic solvent and the auxiliary agent for the coordination reaction, or to dissolve one of the hafnium tetrachloride and the cyclopentadiene in the organic solvent and the auxiliary agent first before adding the other raw material for the reaction. In the present invention, the hafnium tetrachloride is preferably dissolved in the organic solvent and the auxiliary agent before adding the cyclopentadiene for the coordination reaction. In a specific embodiment, the preparation process of step S1 can be: (1) under the protection of inert gas, dissolving hafnium tetrachloride in an organic solvent, adding an additive to fix the pH value within a specific range, setting the temperature to 10-20°C, such as 10°C, 12°C, 14°C, 15°C, 16°C, 18°C, 20°C or any value therebetween, stirring for 2-4h, such as 2h, 2.5h, 3h, 3.5h, 4h or any value therebetween, and fully mixing; (2) adjusting the temperature to 25-30°C, slowly adding cyclopentadiene dropwise, stirring the reaction for 10-15h, and obtaining an off-white liquid; (3) under the protection of inert gas, adjusting the temperature to 5-10°C, and using a seed-induced crystallization method to crystallize the off-white liquid into cyclopentadiene hafnium trichloride.

[0035] In a specific embodiment, the preparation process of step S2 can be: gradually adding cyclopentadienyl hafnium trichloride dropwise into dimethylamine to form a light yellow liquid, and then vacuum distilling to obtain cyclopentadienyl tris(dimethylamino) hafnium.

[0036] In the present invention, in step S2, the conditions of the substitution reaction include a temperature of preferably 20-30°C, such as 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, or any value therebetween; a time of preferably 3-5 hours, such as 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, or any value therebetween; and a molar ratio of cyclopentadienyl hafnium trichloride to dimethylamine of preferably 1:(3-5), such as 1:3, 1:3.5, 1:4, 1:4.5, 1:5, or any value therebetween.

[0037] In the present invention, in step S2, the vacuum distillation crystallization conditions include a vacuum degree of preferably 10 -3 -10 -5 Pa, such as 10 -3 Pa, 10 -4 Pa, 10 -5 Pa or any value therebetween; the temperature is preferably 25-35°C, such as 25°C, 28°C, 30°C, 32°C, 35°C or any value therebetween.

[0038] In the present invention, in step S3, the metal organic chemical vapor deposition process is preferably:

[0039] (1) Heating the substrate to the deposition temperature in the reaction chamber;

[0040] (2) introducing cyclopentadienyl tris(dimethylamino) hafnium and an inert gas into a reaction chamber;

[0041] (3) introducing plasma gas into the reaction chamber to react with cyclopentadienyltri(dimethylamino)hafnium to form a hafnium oxide film;

[0042] (4) introducing an inert gas to purge and remove unreacted precursors and by-products;

[0043] (5) Repeat steps (2) to (4) until the deposition of the hafnium oxide film is completed.

[0044] In the above-mentioned metal organic chemical vapor deposition process, the deposition of a hafnium oxide film of a specified thickness can be completed by controlling the number of repetitions of steps (2)-(4) and the growth rate (GPC) of a single deposition. The present invention does not specifically limit the number of repetitions of steps (2)-(4) and the growth rate (GPC) of a single deposition, and can be flexibly controlled in the actual application process of preparing hafnium oxide films.

[0045] In the above-mentioned metal organic chemical vapor deposition process, in step (2), cyclopentadienyl tris(dimethylamino) hafnium can be first loaded into a precursor raw material tank, and cyclopentadienyl tris(dimethylamino) hafnium can be converted into a gas by heating, and then introduced into the reaction chamber with an inert gas instrument.

[0046] In the present invention, the deposition temperature is preferably 100-400°C, such as 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, or any value therebetween. The plasma gas is preferably oxygen. The inert gas is preferably at least one selected from helium, neon, argon, and nitrogen, and more preferably nitrogen.

[0047] In the present invention, the auxiliary agent is a salt of a strong base and a weak acid. Selecting a strong base and a weak acid salt as the auxiliary agent, on the one hand, reduces the corrosive effect of the strong base on the reactor, reduces the generation of by-products, simplifies product separation, and thus helps to improve yield and purity. On the other hand, it cooperates with the seed-induced crystallization method to help improve crystallization efficiency and control crystal morphology and purity. The auxiliary agent is preferably at least one selected from sodium carbonate, potassium carbonate, sodium acetate, potassium acetate, calcium acetate, sodium bicarbonate, and sodium sulfite, and more preferably sodium carbonate.

[0048] In the present invention, the organic solvent is preferably at least one selected from n-hexane, tetrahydrofuran, diethyl ether and acetone, more preferably n-hexane.

[0049] The present invention adopts the PE-MOCVD method (plasma-metal chemical organic vapor deposition) to prepare hafnium oxide thin films. This technology combines the characteristics of MOCVD and plasma excitation. It can adapt to the materials and shapes of different substrates under low temperature conditions, increasing the flexibility of the process. Under plasma excitation conditions, it can improve the quality and structure of the film. Compared with conventional MOCVD technology, it improves production efficiency and film purity, reduces the generation of by-products, and improves the uniformity and retention of the hafnium oxide film.

[0050] The present invention will be described in detail below through specific examples.

[0051] Example 1

[0052] S1. Under nitrogen, 37.25 g of hafnium tetrachloride and 500 mL of n-hexane were added to a 1000 mL three-necked flask. 12.38 g of sodium carbonate solution was added dropwise at 10°C, the pH was adjusted to approximately 9, and the mixture was stirred for 3 h. The temperature was then raised to 25°C, and 13.51 g of cyclopentadiene was slowly added dropwise and stirred for 12 h. Crystallization was then induced at 8°C using CpZrCl3 as a seed to obtain 48.22 g of cyclopentadienyl hafnium trichloride (yield 95%, purity 99%).

[0053] S2. Then 9.52 g of dimethylamine was added to form a light yellow liquid. -4 Pa, 54.27 g of cyclopentadienyltris(dimethylamino)hafnium (yield 94%, purity 98%) was obtained by vacuum crystallization at 30°C;

[0054] S3. Place a specific reaction substrate in a PE-MOCVD device, set the deposition temperature to 250°C, inject cyclopentadienyltri(dimethylamino)hafnium as a precursor together with nitrogen gas onto a specific substrate in the reaction chamber, introduce oxygen plasma into the reaction chamber, and react with cyclopentadienyltri(dimethylamino)hafnium to form a hafnium oxide film. After the oxide layer is formed, nitrogen gas is introduced again to remove unreacted precursor materials and by-products. Repeat the above deposition steps 4 times to obtain a hafnium oxide film on the substrate.

[0055] Example 2

[0056] S1. Under nitrogen, 22.43 g of hafnium tetrachloride and 500 mL of n-hexane were added to a 1000 mL three-necked flask. 12.38 g of sodium carbonate solution was added dropwise at 10°C, the pH was adjusted to approximately 9, and the mixture was stirred for 3 h. The temperature was then raised to 25°C, and 13.51 g of cyclopentadiene was slowly added dropwise and stirred for 12 h. Crystallization was then induced at 8°C using CpZrCl3 as a seed to obtain 33.42 g of cyclopentadienyl hafnium trichloride (yield 93%, purity 96%).

[0057] S2. Then 9.52 g of dimethylamine was added to form a light yellow liquid. -4 Pa, vacuum crystallization at 30 ° C to obtain 39.50 g of cyclopentadienyltris(dimethylamino)hafnium (yield 92%, purity 95%);

[0058] S3. Place a specific reaction substrate in a PE-MOCVD device, set the deposition temperature to 250°C, inject cyclopentadienyltri(dimethylamino)hafnium as a precursor together with nitrogen gas onto a specific substrate in the reaction chamber, introduce oxygen plasma into the reaction chamber, and react with cyclopentadienyltri(dimethylamino)hafnium to form a hafnium oxide film. After the oxide layer is formed, nitrogen gas is introduced again to remove unreacted precursor materials and by-products. Repeat the above deposition steps 4 times to obtain a hafnium oxide film on the substrate.

[0059] Example 3

[0060] S1. Under nitrogen, 37.25 g of hafnium tetrachloride and 500 mL of n-hexane were added to a 1000 mL three-necked flask. 7.26 g of sodium carbonate solution was added dropwise at 15°C, and the pH was adjusted to approximately 8.5. The mixture was stirred for 3 h. The temperature was then raised to 25°C, and 13.51 g of cyclopentadiene was slowly added dropwise and stirred for 12 h. Crystallization was then induced at 8°C using CpZrCl3 as a seed to obtain 47.71 g of cyclopentadienyl hafnium trichloride (yield 94%, purity 97%).

[0061] S2. Then 9.52 g of dimethylamine was added to form a light yellow liquid. -4 Pa, 53.22 g of cyclopentadienyltris(dimethylamino)hafnium (yield 93%, purity 96%) was obtained by vacuum crystallization at 30°C;

[0062] S3. Place a specific reaction substrate in a PE-MOCVD device, set the deposition temperature to 250-300°C, inject cyclopentadienyltri(dimethylamino)hafnium as a precursor together with nitrogen gas onto a specific substrate in the reaction chamber, introduce oxygen plasma into the reaction chamber, and react with cyclopentadienyltri(dimethylamino)hafnium to form a hafnium oxide film. After the oxide layer is formed, nitrogen gas is introduced again to remove unreacted precursor materials and by-products. Repeat the above deposition steps 4 times to obtain a hafnium oxide film on the substrate.

[0063] Example 4

[0064] S1. Under nitrogen, 37.25 g of hafnium tetrachloride and 500 mL of tetrahydrofuran solvent were added to a 1000 mL three-necked flask. 12.38 g of sodium acetate solution was added dropwise at 10°C, the pH was adjusted to approximately 9, and the mixture was stirred for 3 h. The temperature was then raised to 25°C, and 8.69 g of cyclopentadiene was slowly added dropwise and stirred for 12 h. Crystallization was then induced at 5°C using CpZrCl3 as a seed to obtain 41.80 g of cyclopentadienyl hafnium trichloride (yield 91%, purity 92%).

[0065] S2. Then 9.52 g of dimethylamine was added to form a light yellow liquid. -3 Pa, 46.19 g of cyclopentadienyltris(dimethylamino)hafnium (yield 90%, purity 91%) was obtained by vacuum crystallization at 35°C;

[0066] S3. Place a specific reaction substrate in a PE-MOCVD device, set the deposition temperature to 250-300°C, inject cyclopentadienyltri(dimethylamino)hafnium as a precursor and nitrogen gas onto a specific substrate in the reaction chamber, introduce oxygen plasma into the reaction chamber, and react with cyclopentadienyltri(dimethylamino)hafnium to form a hafnium oxide film. After the oxide layer is formed, nitrogen gas is introduced again to remove unreacted precursor materials and by-products. Repeat the above deposition steps 4 times to obtain a hafnium oxide film on the substrate.

[0067] Example 5

[0068] S1. Under nitrogen, 37.25 g of hafnium tetrachloride and 500 mL of acetone were added to a 1000 mL three-necked flask. 12.38 g of sodium carbonate solution was added dropwise at 20°C, and the pH was adjusted to approximately 9. The mixture was stirred for 3 h. The temperature was then raised to 20°C, and 13.51 g of cyclopentadiene was slowly added dropwise and stirred for 15 h. Crystallization was then induced at 10°C using CpZrBr3 as a seed to obtain 46.69 g of cyclopentadienyl hafnium trichloride (yield 92%, purity 95%).

[0069] S2. Then 4.88 g of dimethylamine was added to form a light yellow liquid. -5 Pa, 46.93 g of cyclopentadienyltris(dimethylamino)hafnium (yield 91%, purity 94%) was obtained by vacuum crystallization at 25°C;

[0070] S3. Place a specific reaction substrate in a PE-MOCVD device, set the deposition temperature to 400°C, inject cyclopentadienyltri(dimethylamino)hafnium as a precursor together with nitrogen gas onto a specific substrate in the reaction chamber, introduce oxygen plasma into the reaction chamber, and react with cyclopentadienyltri(dimethylamino)hafnium to form a hafnium oxide film. After the oxide layer is formed, nitrogen gas is introduced again to remove unreacted precursor materials and by-products. Repeat the above deposition steps 4 times to obtain a hafnium oxide film on the substrate.

[0071] Example 6

[0072] S1. Under nitrogen, 37.25 g of hafnium tetrachloride and 500 mL of ether were added to a 1000 mL three-necked flask. 12.38 g of sodium sulfite solution was added dropwise at 10°C, and the pH was adjusted to approximately 9. The mixture was stirred for 3 h. The temperature was then raised to 30°C, and 13.51 g of cyclopentadiene was slowly added dropwise with stirring for 10 h. Crystallization was then induced at 8°C using CpZrI3 as a seed to obtain 46.19 g of cyclopentadienyl hafnium trichloride (yield 91%, purity 94%).

[0073] S2. Then 9.52 g of dimethylamine was added to form a light yellow liquid. -4 Pa, 50.14 g of cyclopentadienyltris(dimethylamino)hafnium (yield 90%, purity 93%) was obtained by vacuum crystallization at 30°C;

[0074] S3. Place a specific reaction substrate in a PE-MOCVD device, set the deposition temperature to 100°C, inject cyclopentadienyltri(dimethylamino)hafnium as a precursor and nitrogen gas onto a specific substrate in the reaction chamber, introduce oxygen plasma into the reaction chamber, and react with cyclopentadienyltri(dimethylamino)hafnium to form a hafnium oxide film. After the oxide layer is formed, nitrogen gas is introduced again to remove unreacted precursor materials and by-products. Repeat the above deposition steps 4 times to obtain a hafnium oxide film on the substrate.

[0075] Example 7

[0076] A hafnium oxide film was prepared according to the method of Example 1, except that the temperature of the coordination reaction in step S1 was controlled at 10°C. The other conditions were the same as those in Example 1. In step S1, 42.13 g of cyclopentadienyl hafnium trichloride (yield 83%, purity 86%) was prepared, and in step S2, 42.35 g of cyclopentadienyl tris(dimethylamino) hafnium (yield 82%, purity 85%) was prepared.

[0077] Example 8

[0078] A hafnium oxide film was prepared according to the method of Example 1, except that the temperature of the coordination reaction in step S1 was controlled at 40°C. The other conditions were the same as those in Example 1. In step S1, 43.14 g of cyclopentadienyl hafnium trichloride (yield 85%, purity 88%) was prepared, and in step S2, 44.23 g of cyclopentadienyl tris(dimethylamino) hafnium (yield 84%, purity 87%) was prepared.

[0079] Example 9

[0080] A hafnium oxide film was prepared according to the method of Example 1, except that the temperature of the seed crystallization method was controlled at 0°C. The other conditions were the same as those in Example 1. Step S1 prepared 42.63 g of cyclopentadienyl hafnium trichloride (yield 84%, purity 85%), and step S2 prepared 43.28 g of cyclopentadienyl tris(dimethylamino) hafnium (yield 83%, purity 84%).

[0081] Example 10

[0082] A hafnium oxide film was prepared according to the method of Example 1, except that the temperature of the seed crystallization method was controlled at 15°C. The other conditions were the same as those in Example 1. Step S1 prepared 41.62 g of cyclopentadienyl hafnium trichloride (yield 82%, purity 83%), and step S2 prepared 41.42 g of cyclopentadienyl tris(dimethylamino) hafnium (yield 81%, purity 82%).

[0083] Comparative Example 1

[0084] S1. Under nitrogen, 37.25 g of hafnium tetrachloride and 500 mL of n-hexane were added to a 1000 mL three-necked flask. 9.38 g of sodium hydroxide solution was added dropwise at 10°C, and the pH was adjusted to approximately 9. The mixture was stirred for 3 h. The temperature was then raised to 25°C, and 13.51 g of cyclopentadiene was slowly added dropwise and stirred for 12 h. Crystallization was then induced at 10°C using CpZrCl3 as a seed to obtain 38.55 g of cyclopentadienyl hafnium trichloride (yield 76%, purity 76%).

[0085] S2. 9.52 g of dimethylamine was then added to form a pale yellow liquid, which was then crystallized in vacuo to give 31.26 g of cyclopentadienyltris(dimethylamino)hafnium (yield 65%, purity 74%).

[0086] S3. Place a specific reaction substrate in a PE-MOCVD device, set the deposition temperature to 250-300°C, inject cyclopentadienyltri(dimethylamino)hafnium as a precursor together with nitrogen gas onto a specific substrate in the reaction chamber, introduce oxygen into the reaction chamber to react with cyclopentadienyltri(dimethylamino)hafnium to form a hafnium oxide film, and after the oxide layer is formed, introduce nitrogen gas again to remove unreacted precursor materials and by-products. Repeat the above deposition steps four times to obtain a hafnium oxide film on the substrate.

[0087] Comparative Example 2

[0088] S1. Under nitrogen, 37.25 g of hafnium tetrachloride and 500 mL of n-hexane were added to a 1000 mL three-necked flask. 12.38 g of sodium carbonate solution was added dropwise at 10°C, and the pH was adjusted to approximately 9. The mixture was stirred for 3 h. The temperature was then raised to 25°C, and 13.51 g of cyclopentadiene was slowly added dropwise and stirred for 12 h. Crystallization was then induced at 10°C using CpZrCl3 as a seed to obtain 34.51 g of cyclopentadienyl hafnium trichloride (yield 68%, purity 79%).

[0089] S2. Then 9.52 g of dimethylamine was added to form a light yellow liquid. -4 Pa, vacuum crystallization at 30 ° C to obtain 34.34 g of cyclopentadienyltris(dimethylamino)hafnium (yield 78%, purity 67%);

[0090] S3. Place a specific reaction substrate in a conventional CVD device, set the deposition temperature to 250°C, inject cyclopentadienyltri(dimethylamino)hafnium as a precursor together with nitrogen gas onto a specific substrate in the reaction chamber, introduce oxygen into the reaction chamber, and react with cyclopentadienyltri(dimethylamino)hafnium to form a hafnium oxide film. After the oxide layer is formed, nitrogen gas is introduced again to remove unreacted precursor materials and by-products. Repeat the above deposition steps 4 times to obtain a hafnium oxide film on the substrate.

[0091] Test Case

[0092] The hafnium oxide films prepared in the above examples and comparative examples were tested for purity, yield, uniformity and dielectric constant according to the following methods. The results are shown in Table 1.

[0093] (1) Purity test: SIMS (secondary ion mass spectrometry) analyzes the concentration changes of each element to calculate the purity.

[0094] (2) Yield test: It is calculated by the ratio between the input amount of reaction raw materials and the output of the obtained product.

[0095] (3) Uniformity test: AFM (atomic force microscope) test shows that the hafnium oxide film has very good uniformity.

[0096] (4) Dielectric constant test (K value): The test method is the resonant cavity method. The sample is cut into 80 mm × 80 mm squares and the dielectric constant is measured using a dielectric constant tester at a frequency of 0.6 GHz.

[0097] Table 1

[0098] purity Yield Uniformity Dielectric constant (K value) Example 1 98％ 94％ excellent 34 Example 2 95％ 92％ excellent 29 Example 3 96％ 93％ excellent 30 Example 4 91％ 90％ excellent 31 Example 5 94％ 91％ excellent 28 Example 6 93％ 90％ excellent 32 Example 7 85％ 82％ good 23 Example 8 87％ 84％ good 24 Example 9 84％ 83％ good 25 Example 10 82％ 81％ good 21 Comparative Example 1 74％ 65％ Difference 18 Comparative Example 2 78％ 67％ Difference 15

[0099] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A method for preparing a hafnium oxide thin film, characterized in that: The preparation method comprises the following steps: S1. Hafnium tetrachloride is reacted with cyclopentadiene in the presence of an organic solvent and an auxiliary agent, and then cyclopentadiene hafnium trichloride is obtained by seed-induced crystallization. S2. subjecting the cyclopentadienyl hafnium trichloride prepared in step S1 to a substitution reaction with dimethylamine, followed by vacuum distillation and crystallization to obtain cyclopentadienyl tris(dimethylamino) hafnium; S3. Introducing the hafnium cyclopentadienyl tris(dimethylamino) prepared in step S2 as a precursor into a reaction chamber of a PE-MOCVD apparatus, and performing metal organic chemical vapor deposition with a plasma gas at a deposition temperature, so that the hafnium cyclopentadienyl tris(dimethylamino) precursor forms a hafnium oxide film on the substrate surface; The auxiliary agent is a strong base and weak acid salt.

2. The method for preparing a hafnium oxide thin film according to claim 1, wherein: In step S1, the conditions of the coordination reaction include a temperature of 20-30° C. and a time of 10-15 h.

3. The method for preparing a hafnium oxide thin film according to claim 1, wherein: The molar ratio of hafnium tetrachloride to cyclopentadiene is 1:(1.1-3).

4. The method for preparing a hafnium oxide thin film according to claim 1, wherein: The amount of the auxiliary agent used is such that the pH value of the reaction system is 8.5-9.

5.

5. The method for preparing a hafnium oxide thin film according to claim 1, wherein: In step S1, the induced crystals used in the seed induced crystallization method are selected from at least one of CpFe, CpMn, CpZrCl3, CpZrBr3, and CpZrI3.

6. The method for preparing a hafnium oxide thin film according to claim 1, wherein: The temperature of the seed induced crystallization method is 5-10°C.

7. The method for preparing a hafnium oxide thin film according to claim 1, wherein: In step S2, the conditions of the substitution reaction include a temperature of 20-30° C. and a time of 3-5 h.

8. The method for preparing a hafnium oxide thin film according to claim 1, wherein: The molar ratio of cyclopentadienyl hafnium trichloride to dimethylamine is 1:(3-5).

9. The method for preparing a hafnium oxide thin film according to claim 1, wherein: In step S2, the vacuum distillation crystallization conditions include a vacuum degree of 10 -3 -10 -5 Pa, temperature is 25-35℃.

10. The method for preparing a hafnium oxide thin film according to claim 1, wherein: In step S3, the process of metal organic chemical vapor deposition is: (1) Heating the substrate to the deposition temperature in the reaction chamber; (2) introducing cyclopentadienyl tris(dimethylamino) hafnium and inert gas into the reaction chamber; (3) Plasma gas is introduced into the reaction chamber to react with cyclopentadienyltri(dimethylamino)hafnium to form a hafnium oxide film; (4) Introducing inert gas to purge and remove unreacted precursors and by-products; (5) Repeat steps (2) to (4) until the deposition of the hafnium oxide film is completed.

11. The method for preparing a hafnium oxide thin film according to claim 10, wherein: The deposition temperature is 100-400° C.; preferably, the plasma gas is oxygen.

12. The method for preparing a hafnium oxide thin film according to claim 10, wherein: The inert gas is selected from at least one of helium, neon, argon and nitrogen.

13. The method for preparing a hafnium oxide thin film according to claim 1, wherein: The auxiliary agent is selected from at least one of sodium carbonate, potassium carbonate, sodium acetate, potassium acetate, calcium acetate, sodium bicarbonate and sodium sulfite.

14. The method for preparing a hafnium oxide thin film according to claim 1, wherein: The organic solvent is selected from at least one of n-hexane, tetrahydrofuran, diethyl ether and acetone.