A method for preparing a low-carbon-content zinc oxide film

Abstract

This invention discloses a method for preparing low-carbon zinc oxide thin films, belonging to the field of nanotechnology. Using β-diketone zinc as a precursor and H₂O as an oxygen source precursor, a continuous and uniform zinc oxide thin film can be deposited using thermal atomic layer deposition (TLD). This invention uses a precursor free of metal-carbon bonds, solving the safety hazards and high carbon content issues associated with precursors in existing thin film deposition processes. The zinc oxide thin film deposited by this invention exhibits excellent uniformity and good step coverage; furthermore, it is more convenient, safer, and easier to operate during use.

Description

Technical Field

[0001] This invention relates to a method for preparing zinc oxide thin films with low carbon content, belonging to the field of nanotechnology. Background Technology

[0002] Zinc oxide (ZnO) is an electronic conductor with a wide band gap (3.37 eV), high exciton binding energy (60 meV), and high mobility. Meanwhile, ZnO thin films are widely used in the semiconductor field as a flexible, high-throughput material. In recent years, with advancements in ZnO thin film fabrication processes, its applications in touch panels, sensors, solar cells, thin-film transistors (TFTs), light-emitting diodes (LEDs), electrochemical photovoltaic cells, nanogenerators, and optical waveguides have been extensively studied. To meet the diverse application needs of ZnO thin film materials, numerous methods for preparing ZnO thin films have been developed, including molecular beam epitaxy, magnetron sputtering, spray pyrolysis, pulsed laser deposition (PLD), chemical solution deposition, and chemical vapor deposition (MOCVD).

[0003] Atomic layer deposition (ALD) offers significant advantages over the methods described above. Its principle is a dense thin film growth technique based on self-limiting surface chemistry, involving alternating reactions between a gaseous precursor and the substrate surface to deposit materials in atomic layers. This technique can be performed at relatively low temperatures, yielding films with high crystallinity and excellent control over film thickness, composition, and uniformity.

[0004] Currently, among organozinc precursors, diethylzinc (DEZ) is the most representative, offering a high growth rate due to its good volatility and high reactivity. DEZ has long been the dominant precursor for depositing ZnO thin films. However, DEZ contains metallic carbon bonds, which are flammable and extremely sensitive to air, posing a significant safety hazard. Furthermore, its deposition temperature ranges from approximately 110℃ to 170℃, making the stable high-temperature ALD process above 200℃ unsuitable. In addition, the carbon content in the grown films is relatively high. Therefore, it is essential to prepare a relatively safe ZnO precursor with a low carbon content in the film. Summary of the Invention

[0005] [Technical Issues]

[0006] Precursors containing metal carbon bonds are extremely sensitive to air, posing significant safety hazards during use. Furthermore, excessively high temperatures can cause the precursor to decompose, leading to a higher carbon content in the thin film and reducing its quality. As semiconductor process dimensions shrink, existing technologies are no longer adequate for the requirements of new processes.

[0007] [Technical Solution]

[0008] To address the aforementioned issues, this invention utilizes β-diketone zinc as a precursor and H₂O as an oxygen source precursor to deposit continuous and uniform zinc oxide films using thermal atomic layer deposition (TLD). This invention employs a precursor free of metal-carbon bonds, resolving the safety hazards and high carbon content issues associated with precursors in existing film deposition processes. The zinc oxide films deposited using this invention exhibit excellent uniformity and good step coverage. Furthermore, it is more convenient, safer, and easier to operate during use.

[0009] The first objective of this application is to provide a method for preparing low-carbon zinc oxide thin films, using β-diketone zinc as a zinc source precursor and H2O as a reducing precursor, and preparing zinc oxide thin films using thermal atomic layer deposition technology.

[0010] In one embodiment, the structural formula of β-diketone zinc is shown in any one of Formula I, Formula II, or Formula III:

[0011]

[0012] In one embodiment, β-diketone zinc as shown in Formula I is a complex Zn(thd)2; β-diketone zinc as shown in Formula II is a complex Zn(tmod)2; and β-diketone zinc as shown in Formula III is a complex Zn(ibpm)2.

[0013] In one embodiment, a method for preparing zinc oxide thin films using thermal atomic layer deposition technology includes the following steps:

[0014] (1) Place the Si(100) substrate in the reaction chamber and introduce the gaseous zinc source into the reaction chamber in a pulsed manner to perform deposition, thereby obtaining a substrate with deposited zinc source;

[0015] (2) Purge the system with inert gas;

[0016] (3) A gaseous oxygen source precursor is introduced into the reaction chamber in a pulsed manner to react with the zinc source deposited on the substrate.

[0017] (4) Purge the system with inert gas to complete one atomic layer deposition (ALD) growth cycle;

[0018] (5) Repeat steps (1) to (4) to obtain zinc oxide film.

[0019] In one embodiment, the duration of a single pulse of the gaseous zinc source introduced into the reaction chamber in step (1) is 1 to 4 seconds; the gaseous zinc source is introduced in pulse form in the presence of a carrier gas, and the flow rate of the carrier gas is 150 to 200 sccm; the carrier gas is one of high-purity nitrogen.

[0020] In one embodiment, the substrate in step (1) is Si (100), and the substrate is pretreated before entering the reaction chamber to remove surface impurities and oxide layers.

[0021] In one embodiment, the duration of a single pulse of the gaseous zinc source introduced into the reaction chamber in step (1) is 1-4 s, preferably 2 s.

[0022] In one embodiment, in step (1), the gaseous zinc source is introduced in a pulsed manner in the presence of a carrier gas, the flow rate of which is 150 sccm, and the carrier gas is high-purity nitrogen.

[0023] In one embodiment, the gaseous zinc source in step (1) is obtained by heating a zinc source to vaporize it, and the heating temperature of the zinc source is 120°C.

[0024] In one embodiment, the deposition temperature in step (1) is 150–250°C, preferably 190–210°C.

[0025] In one embodiment, the duration of a single pulse in step (3) that introduces the oxygen source precursor into the reaction chamber in a pulsed manner is 0.5 to 2 s, preferably 0.8 s.

[0026] In one embodiment, the gaseous oxygen source precursor in step (3) is produced by vacuuming at room temperature.

[0027] In one implementation, step (5) is repeated 1 to 3000 times.

[0028] A second object of the present invention is to provide a zinc oxide film prepared by any of the above methods.

[0029] A third objective of this invention is to provide the application of the aforementioned zinc oxide thin film in the field of integrated circuit fabrication or nanomaterials.

[0030] A fourth object of the present invention is to provide a product containing the aforementioned zinc oxide film; the product includes electronic devices, optoelectronic devices, transparent conductive films, varistors and piezoelectric devices, antibacterial and packaging materials, coatings and rubber additives.

[0031] The fifth objective of this invention is to provide a method for reducing the carbon content in zinc oxide films, using β-diketone zinc as a zinc source precursor and H2O as a reducing precursor, and preparing zinc oxide films using thermal atomic layer deposition technology.

[0032] In one embodiment, the structural formula of β-diketone zinc is shown in any one of Formula I, Formula II, or Formula III:

[0033]

[0034]

[0035] In one embodiment, the growth temperature of the zinc oxide thin film in the thermal atomic layer deposition technique is 150–250°C.

[0036] In one embodiment, a method for preparing zinc oxide thin films using thermal atomic layer deposition technology includes the following steps:

[0037] (1) Place the Si(100) substrate in the reaction chamber and introduce the gaseous zinc source into the reaction chamber in a pulsed manner to perform deposition, thereby obtaining a substrate with deposited zinc source;

[0038] (2) Purge the system with inert gas;

[0039] (3) A gaseous oxygen source precursor is introduced into the reaction chamber in a pulsed manner to react with the zinc source deposited on the substrate.

[0040] (4) Purge the system with inert gas to complete one atomic layer deposition (ALD) growth cycle;

[0041] (5) Repeat steps (1) to (4) several times to obtain zinc oxide film.

[0042] In one embodiment, the duration of a single pulse of the gaseous zinc source introduced into the reaction chamber in step (1) is 1 to 4 seconds; the gaseous zinc source is introduced in pulse form in the presence of a carrier gas, and the flow rate of the carrier gas is 150 sccm; the carrier gas is one of high-purity nitrogen.

[0043] In one embodiment, the duration of a single pulse of the gaseous zinc source introduced into the reaction chamber in step (1) is 1 to 4 seconds; the gaseous zinc source is introduced in pulse form in the presence of a carrier gas, and the flow rate of the carrier gas is 150 sccm; the carrier gas is one of high-purity nitrogen.

[0044] In one embodiment, the substrate in step (1) is Si (100), and the substrate is pretreated before entering the reaction chamber to remove surface impurities and oxide layers.

[0045] In one embodiment, the duration of a single pulse of the gaseous zinc source introduced into the reaction chamber in step (1) is 1-4 s, preferably 2 s.

[0046] In one embodiment, in step (1), the gaseous zinc source is introduced in a pulsed manner in the presence of a carrier gas, the flow rate of which is 150-200 sccm, and the carrier gas is high-purity nitrogen.

[0047] In one embodiment, the gaseous zinc source in step (1) is obtained by heating a zinc source to vaporize it, and the heating temperature of the zinc source is 120°C.

[0048] In one embodiment, the deposition temperature in step (1) is 150–250°C, preferably 190–210°C.

[0049] In one embodiment, the duration of a single pulse in step (3) that introduces the oxygen source precursor into the reaction chamber in a pulsed manner is 0.5 to 2 s, preferably 0.8 s.

[0050] In one embodiment, the gaseous oxygen source precursor in step (3) is produced by vacuuming at room temperature.

[0051] In one implementation, step (5) is repeated 1 to 3000 times.

[0052] Beneficial effects of the present invention

[0053] This invention uses β-diketone zinc as a precursor and H2O as an oxygen source precursor to deposit continuous and uniform zinc oxide films using thermal atomic layer deposition (TLD). This invention uses a precursor free of metal-carbon bonds, solving the safety hazards and high carbon content issues associated with precursors in existing film deposition processes. The zinc oxide films deposited by this invention exhibit excellent uniformity and good step coverage. Furthermore, it is more convenient, safer, and easier to operate during use. Specifically:

[0054] (1) The β-diketone zinc precursor used in this invention does not contain metal carbon bonds, thus avoiding safety hazards and problems of excessive C content in the preparation process, and improving the deposition quality and effect of zinc oxide film.

[0055] (2) The method of the present invention can be used to prepare small-sized semiconductors.

[0056] (3) The zinc oxide film deposited by the present invention has excellent uniformity and good step coverage.

[0057] (4) The present invention is more convenient, safer and easier to operate during use, simplifies the preparation process of elemental thin films and saves costs. Attached Figure Description

[0058] Figure 1 The 1H NMR spectrum of the complex Zn(thd)2;

[0059] Figure 2 The 1H NMR spectrum of the complex Zn(tmod)2;

[0060] Figure 3 The carbon magnetic hydrogen spectrum of the complex Zn(tmod)2;

[0061] Figure 4 The 1H NMR spectrum of the complex Zn(ibpm)2;

[0062] Figure 5 The carbon magnetic hydrogen spectrum of the complex Zn(ibpm)2;

[0063] Figure 6 The surface roughness of the zinc oxide thin film prepared by the complex Zn(thd)2;

[0064] Figure 7 The surface roughness of the zinc oxide thin film prepared by the complex Zn(tmod)2;

[0065] Figure 8 The surface roughness of the zinc oxide thin film prepared by the complex Zn(ibpm)2;

[0066] Figure 9 The zinc oxide film prepared in Example 1 was subjected to Ar at 200°C. + XPS spectrum before and after 60 seconds of etching;

[0067] Figure 10 The thin film prepared for Comparative Example 2 was subjected to Ar at 200°C. + XPS spectrum before and after 60 seconds of etching;

[0068] Figure 11 The thin film prepared for Comparative Example 3 was subjected to Ar at 200°C. + XPS spectrum before and after 60 seconds of etching;

[0069] Figure 12 The thin film prepared in Example 6 was subjected to Ar at 200°C. + XPS spectrum before and after 60 seconds of etching;

[0070] Figure 13 The thin film prepared in Example 7 was subjected to Ar at 200°C. + XPS spectrum before and after 60 seconds of etching. Detailed Implementation

[0071] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0072] Raw materials used in the examples:

[0073] 3,3-Dimethyl-2-butanone, 2,2-dimethylbutyryl chloride, and methyl trimethylacetate were purchased from Maclean Chemical Reagent Co., Ltd.; the remaining raw materials were all purchased from Sinopharm Chemical Reagent Co., Ltd.

[0074] Preparation method

[0075] 1. The synthetic route of the complex Zn(thd)2 used in the examples is shown below:

[0076]

[0077] 2. The synthetic route of the complex Zn(tmod)2 used in the examples is shown below:

[0078]

[0079] 3. The synthetic route of the complex Zn(ibpm)2 used in the examples is shown below:

[0080]

[0081] Example 1: A method for preparing a low-carbon zinc oxide thin film

[0082] 1. Preparation of the complex Zn(thd)2

[0083] The steps for preparing the complex Zn(thd)2 include:

[0084] (1) Weigh 4.0 g (100 mmol) of NaOH and add it to a 250 mL round-bottom flask. Add 60 mL of H2O and 60 mL of ethanol and stir to dissolve. Weigh 18.4 g (100 mmol) of 2,2,6,6-tetramethyl-3,5-heptadecane and slowly add it to the NaOH solution using a constant pressure funnel. The system changes from a colorless transparent solution to a light yellow transparent solution. Stir at room temperature for 5 h to obtain a mixed solution.

[0085] Weigh 6.8 g of ZnCl2 (50 mmol) and dissolve it in 60 mL of 50% ethanol solution. Slowly add the ZnCl2 solution to the mixed solution using a constant pressure funnel. After adding the ZnCl2 solution, a white solid is rapidly formed and dissolves quickly. After adding 30 mL, the white solid no longer dissolves. With continued addition, the system gradually changes from a clear liquid to a milky white suspension. Stir at room temperature for 8 h; allow to stand, filter to obtain a white solid, and dry at 90 °C for 12 h.

[0086] The dried material was sublimated at 125 °C to obtain a white crystalline solid (34.6 g, yield 80%). The complex Zn(thd)₂ was prepared, and its melting range was determined to be 132.1 °C–134.0 °C. The 1H NMR spectrum is shown below. Figure 1 As shown, 1 H NMR (400MHz, (CD3)2SO, ppm,): δ5.52(s,2H,COCHCO),1.06(s,36H,(CH3)3C).

[0087] The structural formula of the complex Zn(thd)2 is shown below:

[0088]

[0089] 2. Preparation method of zinc oxide thin film

[0090] A method for preparing a low-carbon-content zinc oxide thin film includes the following steps:

[0091] (1) Using Si(100) as a substrate, place it in the reaction chamber; heat the complex Zn(thd)2 to 125℃ to vaporize it and form a gaseous zinc source; introduce the gaseous zinc source into the reaction chamber in the presence of a carrier gas (high-purity nitrogen, flow rate of 150 sccm) in a pulsed manner (pulse time of 2s), and deposit it at 200℃ to obtain a substrate with deposited zinc source;

[0092] (2) After completing one pulse, purge with high-purity nitrogen for 2 seconds;

[0093] (3) Vacuum H2O to vaporize it and form a gaseous oxygen source precursor; introduce the oxygen source precursor into the reaction chamber in a pulsed form (pulse time is 0.8s) and react with the zinc source deposited on the substrate at 200°C in a self-limiting reaction.

[0094] (4) After completing one pulse, purge with high-purity nitrogen for 10 seconds;

[0095] (5) Repeat steps (1) to (4) 500 times to obtain a zinc oxide film with a thickness of 11.09 nm.

[0096] Example 2: A method for preparing a low-carbon zinc oxide thin film

[0097] Based on Example 1, the pulse time in step (1) of step 2 was changed to 1.5s, while the remaining steps were the same as in Example 1, and a zinc oxide film with a thickness of 7.51nm was prepared.

[0098] Example 3: A method for preparing a low-carbon zinc oxide thin film

[0099] Based on Example 1, the pulse time in step (3) of step 2 was changed to 0.5s, while the remaining steps were the same as in Example 1, and a zinc oxide film with a thickness of 8.73nm was prepared.

[0100] Example 4: A method for preparing a low-carbon zinc oxide thin film

[0101] Based on Example 1, the pulse time in step (1) of step 2 was changed to 2.5s, and the remaining steps were the same as in Example 1, and a zinc oxide film with a thickness of 11.12nm was prepared.

[0102] Example 5: A method for preparing a low-carbon zinc oxide thin film

[0103] Based on Example 1, the pulse time in step (3) of step 2 was changed to 1.5s, and the remaining steps were the same as in Example 1, and a zinc oxide film with a thickness of 10.98nm was prepared.

[0104] Comparative Example 1: Changing the substrate material

[0105] Based on Example 1, the substrate material was changed to SiO2, and the remaining steps were the same as in Example 1.

[0106] The results showed that a thin film could not be formed.

[0107] Comparative Example 2: Changing the oxygen source precursor material

[0108] Based on Example 1, O3 was used instead of H2O as the oxygen source precursor, and the remaining steps were the same as in Example 1.

[0109] The results showed that a small amount of film thickness appeared, about 2 nm to 3 nm, and the film growth process did not conform to the characteristics of ALD self-limiting growth.

[0110] Comparative Example 3: Changing the oxygen source precursor material

[0111] Based on Example 1, MBO was used to replace H2O as the oxygen source precursor, and the remaining steps were the same as in Example 1.

[0112] The results showed that a small amount of film thickness appeared, about 2 nm to 3 nm, and the film growth process did not conform to the characteristics of ALD self-limiting growth.

[0113] Example 6: A method for preparing a low-carbon content zinc oxide thin film

[0114] 1. Preparation of the complex Zn(tmod)2·H2O

[0115] The preparation steps for the complex Zn(tmod)2 are as follows:

[0116] 17.6 g (600 mmol) of NaH was weighed into a 500 mL Schelenk flask in a glove box, and 360 mL of anhydrous tetrahydrofuran was added. 52.8 g (528 mmol) of 3,3-dimethyl-2-butanone was weighed and added dropwise to the system using a constant pressure funnel. During the addition, bubbles were generated. The mixture was slowly heated to 70 °C. After the addition was completed, the system changed from a grayish-white turbid liquid to a light green. The reaction was carried out at 70 °C for 1 h. During the reaction, the system gradually changed from light green to bright yellow, and the rate of bubble generation in the oil bubble gas accelerated.

[0117] The reaction continued for 3 hours, during which the system gradually changed from bright yellow to dark yellow. The rate of bubble formation in the oil vapor slowed down and gradually stabilized. The reaction continued for 16 hours, during which the rate of bubble formation in the oil vapor began to slow down. The reaction continued for 20 hours, during which no more bubbles were formed in the oil vapor, and heating was stopped. The mixture was allowed to stand and separate into layers. The upper layer was a dark yellow clear liquid, and the lower layer was a dark gray precipitate. The mixture was filtered through a sand filter to obtain the upper dark yellow clear liquid. 35.4 g (264 mmol) of 2,2-dimethylbutyryl chloride was weighed and added dropwise to the yellow clear liquid under ice bath conditions. A white precipitate was quickly formed. After the addition was complete, the mixture became a dark yellow turbid liquid. After returning to room temperature, the system gradually changed from dark yellow to pale yellow. The color of the system remained unchanged after stirring for 4 hours. 27.0 mL of concentrated hydrochloric acid was added dropwise under ice bath conditions. A large amount of white precipitate was quickly formed. After the addition was complete, the mixture was stirred for 2 hours, and the system gradually separated into layers from a pale yellow turbid liquid, with a pale yellow clear liquid on top and a white precipitate on the bottom. The filtrate was filtered and extracted three times with n-hexane (100 mL × 50 mL × 50 mL), and the organic phases were combined. 40 g of anhydrous sodium sulfate was added to the organic phase, and the filtrate was filtered again. Volatile solvents were removed by rotary evaporation, yielding 60 mL of a clear yellow liquid. The clear yellow liquid was evacuated to 4.0 mm Hg and slowly heated. The fraction obtained by vacuum distillation at an oil temperature of 90 °C and a vapor temperature of 71 °C was collected, yielding 30 mL of a colorless, transparent liquid, which is the ligand Htmod. The purity of the ligand Htmod was verified by gas chromatography, ensuring that the purity was above 96%.

[0118] Weigh 4.0 g (100 mmol) of NaOH and add it to a 250 mL round-bottom flask. Add 120 mL of methanol and stir until the solid dissolves. Weigh 19.8 g of Htmod (100 mmol) and slowly add it to the NaOH solution using a constant-pressure funnel. The system changes from a colorless transparent liquid to a pale yellow transparent liquid. Stir for 5 h. Weigh 14.9 g of Zn(NO3)2·6H2O (50 mmol) and dissolve it in 60 mL of methanol solution. Slowly add the Zn(NO3)2·6H2O solution to the system. After adding Zn(NO3)2·6H2O, a white solid is rapidly formed and dissolves quickly. Continue adding dropwise to 30 mL. The white solid no longer dissolves, and the system gradually becomes turbid and a white precipitate forms. After the addition is complete, the system becomes a milky white suspension. Stir for 8 h. Allow to stand and separate into layers. The upper layer is a pale yellow clear liquid, and the lower layer is a white precipitate. Filter and collect the filtrate. Adding 60 mL of H₂O to the filtrate quickly produces a viscous substance in the lower layer of the clear liquid. Adding 60 mL of n-hexane and stirring dissolves the viscous substance, causing the system to separate into layers. The upper n-hexane phase is collected. Adding 20 g of anhydrous sodium sulfate and filtering yields a pale yellow n-hexane solution. Concentrating this solution to 10 mL and recrystallizing at -30 °C yields 18.4 g of colorless crystals, which is the complex Zn(tmod)₂·H₂O. The yield of the complex Zn(tmod)₂·H₂O is 80%, with a melting range of 71.9 °C–73.0 °C.

[0119] The hydrogen NMR spectrum of Zn(tmod)2·H2O is: 1 HNMR(400MHz,C2D6SO,ppm)δ,0.75(t,3H,CH2CH3),δ1.42(m,2H,((CH3)2CCH2CH3 )), δ1.01(s,6H((CH3)2CCH2CH3)), δ1.06(s,9H((CH3)3C)δ5.47(s,O=C-CH-C=O);

[0120] The carbon NMR spectrum is as follows: 13 C NMR(600MHz,C2D6SO,ppm)tδ200.58(C=O),89.55(O=C-CH-C=O)44.58(-C(CH3)2-CH2-CH3),41.08(-C(CH3) 3), 34.22(-C(CH3)2-CH2-CH3), 28.65(-C(CH3)2-CH2-CH3), 26.12(-C(CH3)3), 9.65(-C(CH3)2-CH2-CH3).

[0121] 2. Preparation of the complex Zn(tmod)2

[0122] 85.0 g (178 mmol) of Zn(tmod)₂·H₂O crystals were added to Schlenk flask A. Another Schlenk flask B was assembled using a U-tube, and 40 g of phosphorus pentoxide was added to Schlenk flask B. The crystal mixture in Schlenk flask A was evacuated and slowly heated. At approximately 85 °C, the crystals melted, and the system became a white, turbid liquid. Heating was continued until 120 °C, after which a white, powdery solid began to slowly appear on the flask wall. The mixture was kept at this temperature for 12 h. During this holding period, the system remained a white, turbid liquid without any significant changes.

[0123] A small amount of liquid appeared in the U-tube after about 4 hours, reaching its peak at 10 hours. After incubation at this temperature for 12 hours, the mixture was brought back to room temperature, and 100 mL of anhydrous n-hexane was added. After standing, the mixture separated into layers: a yellow clear liquid on top and a white precipitate on the bottom. The mixture was filtered through a sand filter, separating a white powdery solid and approximately 120 mL of pale yellow clear liquid. The solution was concentrated to 50 mL and recrystallized at -30°C to obtain 40.0 g of pale yellow crystals, which is the complex Zn(tmod)2.

[0124] The yield of the complex Zn(tmod)2 was 49%, and the melting range was 41.8℃-43.0℃.

[0125] The 1H NMR spectrum of Zn(tmod)2 Figure 2 )for: 1H NMR(400MHz,C2D6SO,ppm)δ,0.73(t,3H,CH2CH3),δ1.44(m,2H,((CH3)2CCH2CH3) ), δ1.02(s,6H((CH3)2CCH2CH3)), δ1.06(s,9H((CH3)3C)δ5.48(s,O=C-CH-C=O);

[0126] Its carbon NMR spectrum ( Figure 3 )for: 13 C NMR(600MHz,C2D6SO,ppm)tδ200.12(C=O),90.86(O=C-CH-C=O)43.85(-C(CH3)2-CH2-CH3),41.09(-C(CH3) 3), 34.22(-C(CH3)2-CH2-CH3), 28.64(-C(CH3)2-CH2-CH3), 26.12(-C(CH3)3), 9.67(-C(CH3)2-CH2-CH3).

[0127] The structural formula of the complex Zn(tmod)2 is shown below:

[0128]

[0129] 3. Preparation method of zinc oxide thin film

[0130] Zinc oxide films were prepared by replacing complex Zn(thd)2 with complex Zn(tmod)2, including the following steps:

[0131] (1) Using Si(100) as a substrate, place it in the reaction chamber; heat the complex Zn(tmod)2 to 120℃ to vaporize it and form a gaseous zinc source; introduce the gaseous zinc source into the reaction chamber in the presence of a carrier gas (high-purity nitrogen, flow rate of 150 sccm) in a pulsed manner (pulse time of 4s), and deposit it at 200℃ to obtain a substrate with deposited zinc source;

[0132] (2) After completing one pulse, purge with high-purity nitrogen for 2 seconds;

[0133] (3) Vacuum H2O to vaporize it and form a gaseous oxygen source precursor; introduce the oxygen source precursor into the reaction chamber in a pulsed form (pulse time is 0.8s) and react with the zinc source deposited on the substrate at 200°C in a self-limiting reaction.

[0134] (4) After completing one pulse, purge with high-purity nitrogen for 10 seconds;

[0135] (5) Repeat steps (1) to (4) 500 times to obtain a zinc oxide film with a thickness of 12.03 nm.

[0136] Example 7: A method for preparing a low-carbon content zinc oxide thin film

[0137] Based on Example 6, the pulse time in step (1) of 3 was changed to 3s, and the remaining steps were the same as in Example 1, and a zinc oxide film with a thickness of 8.11nm was prepared.

[0138] Example 8: A method for preparing a low-carbon zinc oxide thin film

[0139] Based on Example 6, the pulse time in step (3) of 3 was changed to 0.5s, and the remaining steps were the same as in Example 1, and a zinc oxide film with a thickness of 7.51nm was prepared.

[0140] Example 9: A method for preparing a low-carbon content zinc oxide thin film

[0141] Based on Example 6, the pulse time in step (1) of 3 was changed to 2.5s, and the remaining steps were the same as in Example 1, to prepare a zinc oxide film with a thickness of 12.10nm.

[0142] Example 10: A method for preparing a low-carbon content zinc oxide thin film

[0143] Based on Example 6, the pulse time in step (3) of Example 6 was changed to 1.5s, and the remaining steps were the same as in Example 1, and a zinc oxide film with a thickness of 11.97nm was prepared.

[0144] Example 11: A method for preparing a low-carbon content zinc oxide thin film

[0145] 1. Preparation of complex 3(Zn(ibpm)2)·2H2O

[0146] The preparation steps for complex 3(Zn(ibpm)2)·2H2O are as follows:

[0147] Weigh 67.2 g (600 mmol) of potassium tert-butoxide into a 1000 mL Schelenk flask. Construct a constant-pressure dropping funnel and add 300 mL of DMF to the funnel. Use a vacuum pump to remove oxygen from the DMF until no more bubbles emerge. Transfer the solution to the Schelenk flask. Heat to 50 °C and stir until the solid is completely dissolved, resulting in a pale blue turbid solution. Add 42.0 g (3600 mmol) of trimethylacetate dropwise. After the addition is complete, a pale yellow turbid solution appears. Continue adding 21.0 g (240 mmol) of 3-methyl-2-butanone dropwise. After the addition is complete, a bright yellow turbid solution appears. After stirring for 4 hours, the system turns dark brown. Add dilute sulfuric acid (290 mL deionized water + 29 mL concentrated sulfuric acid) to the system all at once and stir vigorously. Upon addition of sulfuric acid, a precipitate forms rapidly, and the system slowly changes from dark brown to dark red, and finally rapidly to bright yellow. After standing and separating, the upper layer was a bright yellow clear liquid, and the lower layer was a white precipitate. Filtering yielded the upper pale yellow clear liquid, which was extracted three times with n-hexane (100 mL × 50 mL × 50 mL). The upper n-hexane phase was collected, and 20 g of anhydrous sodium sulfate was added. The mixture was filtered, and the solvent was removed by rotary evaporation. 60 mL of the yellow clear liquid was obtained. The yellow clear liquid was then evacuated to 4.0 mmHg and slowly heated. The fraction obtained by vacuum distillation at an oil temperature of 80 °C and a vapor temperature of 65 °C yielded 30 mL of a colorless, transparent liquid. The purity of the ligand Hibpm was verified by gas chromatography, ensuring that the purity of the ligand was above 96%.

[0148] Weigh 4.0 g (100 mmol) of NaOH and add it to a 250 mL round-bottom flask. Add 120 mL of methanol and stir until the solid dissolves. Weigh 17.0 g (100 mmol) of Hibpm and slowly add it to the NaOH solution using a constant-pressure funnel. The system changes from a colorless transparent liquid to a pale yellow transparent liquid. Stir for 5 hours. Weigh 14.9 g (50 mmol) of Zn(NO3)2·6H2O and dissolve it in 60 mL of methanol solution. Slowly add the Zn(NO3)2·6H2O solution to the system. After adding Zn(NO3)2·6H2O, a white solid is rapidly formed and dissolves quickly. Continue adding dropwise to 30 mL. The white solid no longer dissolves, and the system gradually becomes turbid and a white precipitate forms. After the addition is complete, the system becomes a milky white suspension. Stir for 8 hours. Allow to stand and separate into layers. The upper layer is a pale yellow clear liquid, and the lower layer is a white precipitate. Filter and collect the filtrate. Add 60 mL of H₂O to the filtrate. A viscous substance is quickly formed in the lower layer of the clear liquid. Add 60 mL of n-hexane and stir. The viscous substance dissolves, and the system separates into layers. Separate the liquid and collect the upper n-hexane phase. Add 20 g of anhydrous sodium sulfate, filter, and obtain a pale yellow n-hexane solution. Concentrate to 10 mL and recrystallize at -30 °C to obtain 18.2 g of colorless crystals, i.e., 3(Zn(ibpm)₂)·2H₂O. The yield of 3(Zn(ibpm)₂)·2H₂O is 91%, and the melting range is 57.8 °C-59.1 °C.

[0149] The 1H NMR spectrum of 3(Zn(ibpm)2)·2H2O is as follows: 1 HNMR (400MHz, C2D6SO, ppm)5.36(s,1H,O=C-CH-C=O),2.28(m,1H,-CH-(CH3)2),1.06(s,9H,-C(CH3)3),0.99(d,6H,-CH-(CH3)2);

[0150] The carbon NMR spectrum is as follows: 13 C-NMR (101MHz, CDCl3, 25℃, ppm) δ199.39(C=O), 91.27(O=C-CH-C=O), 49.57(-C(CH3)3), 40.87(-CH-(CH3)2), 28.58(-C(CH3)3), 20.74(-CH-(CH3)2).

[0151] 2. Preparation of the complex Zn(ibpm)2

[0152] 80.0 g (64.3 mmol) of Zn(ibpm)₂·2H₂O crystals were added to Schlenk flask A. Another Schlenk flask B was assembled using a U-tube, and 40 g of phosphorus pentoxide was added to Schlenk flask B. The crystal mixture in Schlenk flask A was slowly heated under vacuum. The crystals melted at approximately 85 °C, and the system became a white, turbid liquid. Heating continued to 120 °C, after which a white powdery solid began to slowly appear on the flask wall. The mixture was kept at this temperature for 12 h. During this period, the system remained a white, turbid liquid without significant change. A small amount of liquid appeared in the U-tube at approximately 4 h, reaching a peak at 10 h. After 12 h of heating, the mixture was allowed to return to room temperature, and 100 mL of anhydrous n-hexane was added. The mixture was allowed to stand, and after standing, it separated into layers: a yellow clear liquid on top and a white precipitate on the bottom. The mixture was filtered through a sand filter, separating the white powdery solid and approximately 120 mL of pale yellow clear liquid. The volatile solvent was removed under vacuum, yielding 40 mL of a pale yellow viscous liquid. The pale yellow viscous liquid was subjected to vacuum distillation, and the fraction obtained by collecting the oil bath at 190℃ and the vapor temperature at 170℃ was 15 mL of pale yellow transparent liquid (about 20 g), namely Zn(ibpm)2, with a yield of 27%.

[0153] The 1H NMR spectrum of Zn(ibpm)2 Figure 4 )for: 1 HNMR (400MHz, C2D6SO, ppm)5.35(s,1H,O=C-CH-C=O),2.27(m,1H,-CH-(CH3)2),1.05(s,9H,-C(CH3)3),0.98(d,6H,-CH-(CH3)2);

[0154] Its carbon NMR spectrum of Zn(ibpm)2 ( Figure 5 )for: 13 C-NMR (101MHz, CDCl3, 25℃, ppm) δ199.36(C=O), 91.26(O=C-CH-C=O), 49.57(-C(CH3)3), 40.50(-CH-(CH3)2), 28.59(-C(CH3)3), 20.75(-CH-(CH3)2).

[0155] The structural formula of the complex Zn(ibpm)2 is shown below:

[0156]

[0157] 3. Preparation method of zinc oxide thin film

[0158] Zinc oxide films were prepared by replacing complex Zn(thd)2 with complex Zn(ibpm)2, including the following steps:

[0159] (1) Using Si(100) as a substrate, place it in the reaction chamber; heat the complex Zn(ibpm)2 to 140℃ to vaporize it and form a gaseous zinc source; introduce the gaseous zinc source into the reaction chamber in the presence of a carrier gas (high-purity nitrogen, flow rate of 150 sccm) in a pulsed manner (pulse time of 3s), and deposit it at 200℃ to obtain a substrate with deposited zinc source;

[0160] (2) After completing one pulse, purge with high-purity nitrogen for 2 seconds;

[0161] (3) Vacuum H2O to vaporize it and form a gaseous oxygen source precursor; introduce the oxygen source precursor into the reaction chamber in a pulsed form (pulse time is 0.8s) and react with the zinc source deposited on the substrate at 200°C in a self-limiting reaction.

[0162] (4) After completing one pulse, purge with high-purity nitrogen for 10 seconds;

[0163] (5) Repeat steps (1) to (4) 500 times to obtain a zinc oxide film with a thickness of 7.41 nm.

[0164] Example 12: A method for preparing a low-carbon zinc oxide thin film

[0165] Based on Example 11, the pulse time in step (1) of step 3 was changed to 2s, and the remaining steps were the same as in Example 7, to prepare a zinc oxide film with a thickness of 6.56nm.

[0166] Example 13: A method for preparing a low-carbon zinc oxide thin film

[0167] Based on Example 11, the pulse time in step (3) of step 3 was changed to 0.8s, and the remaining steps were the same as in Example 7, to prepare a zinc oxide film with a thickness of 6.91nm.

[0168] Example 14: A method for preparing a low-carbon zinc oxide thin film

[0169] Based on Example 11, the pulse time in step (1) of step 3 was changed to 4s, and the remaining steps were the same as in Example 1, and a zinc oxide film with a thickness of 7.39nm was prepared.

[0170] Example 15: A method for preparing a low-carbon zinc oxide thin film

[0171] Based on Example 11, the pulse time in step (3) of step 3 was changed to 1.0s, and the remaining steps were the same as in Example 1, and a zinc oxide film with a thickness of 7.60nm was prepared.

[0172] Example 16: Membrane Performance Testing

[0173] Following the methods of Examples 1, 6, and 11, the number of repetitions in step (5) was changed to 1000 times to prepare a zinc oxide film.

[0174] (1) Surface roughness

[0175] The zinc oxide thin film was subjected to SEM and AFM tests to detect the average thickness and surface roughness of the film. The results are as follows: Figure 6 (Combination Zn(thd)2), Figure 7 (complex Zn(tmod)2), Figure 8 (Zn(ibpm)2) and Table 1 are shown.

[0176] Table 1 Film thickness and roughness

[0177] Average film thickness (nm) Roughness (nm) <![CDATA[Example 1 - Complex Zn(thd)2]]> 21.81 0.89 <![CDATA[Example 6 - Complex Zn(tmod)2]]> 24.02 0.72 <![CDATA[Example 11 - Complex Zn(ibpm)2]]> 14.94 0.91

[0178] (2) Element content of thin films

[0179] Test at 200℃ using Ar + XPS spectra before and after 60 seconds of etching are shown below. Figure 9 (Combination Zn(thd)2, Figure 10 (Comparative Example 2) Figure 11 (Comparative Example 3) Figure 12 (Zn(tmod)2、 Figure 13 As shown in (Zn(ibpm)2), the elemental contents are shown in Table 2.

[0180] Table 2 Elemental composition of thin films

[0181] carbon element Zinc oxygen element Zinc: Oxygen <![CDATA[Example 1 - Complex Zn(thd)2]]> 5.6％ 46.48％ 47.92％ 0.97 <![CDATA[Example 6 - Complex Zn(tmod)2]]> 3.4％ 47.8％ 48.8％ 0.98 <![CDATA[Example 7 - Complex Zn(ibpm)2]]> 6.5％ 45.5％ 48.0％ 0.94 <![CDATA[Comparative Example 2 - O3 Oxygen Source Precursor]]> 61.58％ 2.48％ 35.93％ - Comparative Example 3-MBO Oxygen Source Precursor 6.8％ 15.4％ 77.8％ -

[0182] The results in summary show that the zinc oxide films prepared by the complexes Zn(thd)2, Zn(tmod)2, and Zn(ibpm)2 have high carbon content and smooth surfaces, overcoming the safety hazards and high carbon content of the precursors in the original thin film deposition process.

[0183] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing low-carbon content zinc oxide thin films, characterized in that, Zinc oxide films were prepared using β-diketone zinc as the zinc source precursor and H2O as the reducing precursor, and the growth temperature of the zinc oxide films in the thermal atomic layer deposition technique was 150~250℃. The structural formula of β-diketone zinc is shown in any one of Formula I, Formula II, or Formula III: Formula I; Formula II; Formula III.

2. The method according to claim 1, characterized in that, The method for preparing zinc oxide thin films using thermal atomic layer deposition technology includes the following steps: (1) Place the Si(100) substrate in the reaction chamber and introduce the gaseous zinc source into the reaction chamber in a pulsed manner to perform deposition, thereby obtaining a substrate with deposited zinc source; (2) Purge the system with inert gas; (3) A gaseous oxygen source precursor is introduced into the reaction chamber in a pulsed manner to react with the zinc source deposited on the substrate; (4) Purge the system with inert gas to complete one atomic layer deposition (ALD) growth cycle; (5) Repeat steps (1) to (4) to obtain zinc oxide film.

3. The method according to claim 2, characterized in that, In step (1), the duration of a single pulse of the gaseous zinc source introduced into the reaction chamber in the form of a pulse is 1 to 4 seconds; the gaseous zinc source is introduced in the form of a pulse in the presence of a carrier gas, and the flow rate of the carrier gas is 150 to 200 sccm; the carrier gas is one of the high-purity nitrogen gases.

4. The zinc oxide film prepared by the method according to any one of claims 1 to 3.

5. The application of the zinc oxide thin film according to claim 4 in the field of integrated circuit fabrication or nanomaterials.

6. A product characterized in that, The product contains the zinc oxide film as described in claim 4; the product includes electronic devices, optoelectronic devices, transparent conductive films, varistors and piezoelectric devices, antibacterial and packaging materials, coatings and rubber additives.

Images