Method for forming bismuth oxide film

Abstract

To provide a method of depositing a bismuth oxide film with good quality while reducing costs by lightening environmental loads, decreasing raw material costs and also reducing energy.SOLUTION: A method of depositing a bismuth oxide film comprises the steps of: generating a first mist by atomizing a raw material solution prepared by dissolving a bismuth-containing compound in a solvent; generating a second mist by atomizing an oxidizer solution; generating a mixed mist by transferring, by a carrier gas, the first mist and the second mist to a mixing container, and then mixing them; and depositing the bismuth oxide film on a substrate placed in a heating reaction area by transferring, by the carrier gas, the mixed mist to the heating reaction area and then subjecting the mixed mist to heating reaction on the substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for forming a bismuth oxide film. [Background technology]

[0002] Bismuth oxide films are expected to be used as infrared reflective coatings (see, for example, Patent Document 1), as insulating films and protective films for BiSrCaCuO-based superconductors (see, for example, Patent Document 1), and as insulating layers for semiconductor devices such as thin-film varistors (see, for example, Patent Document 3 and Non-Patent Document 1).

[0003] Generally, physical vapor deposition (PVD) methods such as sputtering and evaporation, and chemical vapor deposition (CVD) methods are known as methods for depositing oxide films. PVD has the disadvantage that the upper and lower limits of the deposition rate are relatively narrower than those of CVD. PVD requires a high-vacuum atmosphere, which requires an exhaust system, which tends to increase deposition costs, makes it difficult to enlarge the deposition area, and results in low throughput.

[0004] On the other hand, CVD has the potential to solve these problems associated with PVD. However, while many current CVD methods do not require the high level of vacuum required by PVD, they do require a vacuum pumping process, necessitating a large-scale deposition system including an exhaust gas treatment device. Furthermore, CVD requires the transport of metal elements in the gas phase, making raw materials with high vapor pressures suitable. However, these are extremely flammable and dangerous substances, so the deposition system must be equipped with a safety mechanism for safe handling. Most raw materials are relatively expensive. Furthermore, deposition by CVD generally requires relatively high temperatures. Attempts have been made to deposit bismuth oxide films using CVD using organic bismuth complexes containing phenyl or methyl groups as raw materials (see Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 02-055245 [Patent Document 2] Japanese Patent Application Publication No. 05-254995 [Patent Document 3] Japanese Patent Publication No. 58-086702 [Non-patent literature]

[0006] [Non-Patent Document 1] Keng Ming Chang, Chuan Pu Liu & Chon Ming Tsai, MRS Online Proceedings Library volume 786, Article number: 62 (2003), Microstructure and Electrical Properties of Zinc Oxide Thin Film Varistors Prepared by RF Sputtering Summary of the Invention [Problem to be solved by the invention]

[0007] However, triphenylbismuth, which is used as a raw material, is relatively expensive, and the film can be formed at a relatively high temperature of 500°C to 800°C.

[0008] Therefore, an object of the present invention is to provide a method for forming a high-quality bismuth oxide film while reducing costs by reducing the environmental load, reducing raw material costs, and reducing energy consumption. [Means for solving the problem]

[0009] The method for forming a bismuth oxide film of the present invention comprises the steps of: a step of atomizing a first raw material solution obtained by dissolving a bismuth-containing compound in a first solvent to generate a first mist; atomizing a second raw material solution containing an oxidizing agent and a second solvent to generate a second mist; a step of generating a mixed mist by transporting the first mist and the second mist to a mixing container using a carrier gas and mixing them; The mixed mist The aforementioned and transporting the mixed mist to a thermal reaction area by a carrier gas, and causing a thermal reaction of the mixed mist on a substrate placed in the thermal reaction area, thereby forming a bismuth oxide film on the substrate. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an explanatory diagram of a bismuth oxide film manufacturing apparatus according to one embodiment of the present invention; [Figure 2] 1A to 1C are explanatory diagrams relating to a method for producing a bismuth oxide film according to one embodiment of the present invention. [Figure 3] FIG. 1 is an explanatory diagram showing the results of XRD analysis of a bismuth oxide film. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Film forming equipment) The bismuth oxide film manufacturing apparatus according to one embodiment of the present invention shown in FIG. 1 includes a first raw material solution supply device S1, a second raw material solution supply device S2, a first mist generator 10, a second mist generator 20, a mixed mist generator 30, and a heating film-forming device 40.

[0012] (Film forming method) The first raw solution supplying device S1 supplies a bismuth-containing compound solution as a first raw solution to the first mist generator 10. For example, a bismuth halide such as bismuth chloride is used as the bismuth-containing compound. For example, methyl acetate, butyl acetate, methyl salicylate, ethyl formate, and / or ethyl acetate is used as the first solvent of the first raw solution. The first mist generator 10 generates a first mist by atomizing the first raw solution (FIG. 2 / STEP 10). The first mist is diluted with a dilution gas and then supplied to the mixed mist generator 30.

[0013] The second raw solution supply device S2 supplies the oxidizer solution as the second raw solution to the second mist generator 20. For example, H2O2 and / or H2O are used as the oxidizer. For example, methyl acetate, butyl acetate, methyl salicylate, ethyl formate, and / or ethyl acetate are used as the second solvent of the second raw solution. The second solvent may be the same as or different from the first solvent. The second mist generator 20 generates a second mist by atomizing the second raw solution (FIG. 2 / STEP 20). The second mist is diluted with a dilution gas and then supplied to the mixed mist generator 30.

[0014] The mixed mist generator 30 generates a mixed mist by mixing the first mist and the second mist (FIG. 2 / STEP 30). The mixed mist is supplied by the carrier gas to the thermal deposition apparatus 40 and, ultimately, onto a substrate placed in the internal space (deposition area) of the thermal deposition apparatus 40. At this time, in addition to the mixed mist, ozone (O3) and / or oxygen (O2) may be supplied to the thermal deposition apparatus 40 as an oxidation-assisting gas. The temperature of the internal space of the thermal deposition apparatus 40 is controlled to be within a temperature range of 200°C to 500°C, preferably 300°C to 400°C (FIG. 2 / STEP 40). As a result, a bismuth oxide film is formed on the substrate.

[0015] (Example)

[0016] Example 1 Bismuth chloride was used as the bismuth-containing compound, and methyl acetate was used as the first solvent to prepare a first raw material solution, which then generated a first mist. Hydrogen peroxide was used as the oxidizing agent, and methyl acetate was used as the second solvent to prepare a second raw material solution, which then generated a second mist. The first mist and the second mist were each diluted with a dilution gas, which then generated a mixed mist. The mixed mist was transported to the substrate by a carrier gas, and the ambient temperature (film formation temperature) of the substrate was controlled to 400°C. The thin film of Example 1 was formed by controlling the oxidizing agent mist flow rate to 4.0 L / min.

[0017] Example 2 The thin film of Example 2 was formed under the same conditions as Example 1, except that the flow rate of the oxidant mist was controlled to 6.0 L / min.

[0018] Example 3 The thin film of Example 2 was formed under the same conditions as Example 1, except that the flow rate of the oxidant mist was controlled to 8.0 L / min.

[0019] (Comparative Example)

[0020] (Comparative Example 1) A thin film of Comparative Example 1 was formed under the same conditions as in Example 1, except that the flow rate of the oxidant mist was controlled to 2.0 L / min.

[0021] (Comparative Example 2) A thin film of Comparative Example 2 was formed under the same conditions as in Example 1, except that only the first mist was used instead of the mixed mist.

[0022] (XRD analysis results) Figure 3 shows the results of X-ray diffraction analysis of the bismuth oxide films of the examples and comparative examples. The right side of Figure 3 shows an enlarged version of a portion of the left side of Figure 3. The XRD analysis results confirmed that the thin films of Comparative Examples 1 and 2 were not bismuth oxide thin films, but the thin films of Examples 1 to 3 were bismuth oxide thin films.

[0023] (Effects of the present invention) The film formation method of the present invention allows the use of safer and less expensive raw materials than the organometallic compounds used in conventional CVD methods. Furthermore, while conventional CVD methods require a film formation temperature of 500°C to 800°C, the film formation temperature of the present invention is significantly lower, at 200°C to 500°C, making it possible to form bismuth oxide films of sufficient quality for industrial use under relatively energy-saving conditions. Furthermore, the present invention is an atmospheric film formation method that does not require a vacuum atmosphere during film formation, eliminating the need for an exhaust system and making it a more industrially advantageous method for forming bismuth oxide films. In other words, the present invention provides a film formation method that solves the above-mentioned problems. [Explanation of symbols]

[0024] 10: First mist generator, 20: Second mist generator, 30: Mixed mist generator, 40: Heating film forming device, S1: First raw material solution supply device, S2: Second raw material solution supply device.

Claims

1. a step of atomizing a first raw material solution obtained by dissolving a bismuth-containing compound in a first solvent to generate a first mist; atomizing a second raw material solution containing an oxidizing agent and a second solvent to generate a second mist; a step of generating a mixed mist by transporting the first mist and the second mist to a mixing container using a carrier gas and mixing them; transporting the mixed mist to a thermal reaction area by the carrier gas, and causing a thermal reaction of the mixed mist on a substrate placed in the thermal reaction area to form a bismuth oxide film on the substrate. A method for forming a bismuth oxide film.

2. 2. The method for forming a bismuth oxide film according to claim 1, The bismuth-containing compound is a bismuth halide. A method for forming a bismuth oxide film.

3. 3. The method for forming a bismuth oxide film according to claim 1, The oxidizing agent is H 2 O 2 and H 2 At least one of O A method for forming a bismuth oxide film.

4. The method for forming a bismuth oxide film according to any one of claims 1 to 3, The first solvent is at least one of methyl acetate, butyl acetate, methyl salicylate, ethyl formate, and ethyl acetate. A method for forming a bismuth oxide film.

5. The method for forming a bismuth oxide film according to any one of claims 1 to 4, The carrier gas is an inert gas. A method for forming a bismuth oxide film.

6. The method for forming a bismuth oxide film according to any one of claims 1 to 5, The thermal reaction temperature is in the range of 200°C to 500°C. A method for forming a bismuth oxide film.

7. The method for forming a bismuth oxide film according to any one of claims 1 to 6, The mixed mist and O as an oxidation assisting gas 3 Gas and O 2 At least one of the gases is simultaneously transported to the film formation area. A method for forming a bismuth oxide film.

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