Method for producing vapor deposition material
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Filing Date
- 2026-03-03
- Publication Date
- 2026-06-03
Abstract
Description
Method for producing deposition material
[0001] The present disclosure relates to a method for producing a vapor deposition material used in a vacuum vapor deposition method.
[0002] Vacuum evaporation is a film-forming technique in which evaporation material is heated in a vacuum, and the evaporation material turns into gas molecules that adhere to a substrate, forming a thin film. Vacuum evaporation is widely used to form elements such as electronic components, semiconductor devices, optical thin films, magnetic devices, LEDs, organic EL, and LCDs. Vacuum evaporation can also be used to form non-metallic films such as oxides, in addition to metal films.
[0003] Conventionally, when a deposition material is filled in a crucible and melted using an electron beam (EB) or the like, impurities contained in the deposition material volatilize, causing bumping, resulting in the adhesion of particles to a substrate. Regarding the problem of bumping, Patent Document 1 proposes a method for reducing impurities. Patent Document 2 proposes a method of adding an additive metal, and Patent Document 3 proposes a method of controlling the amount of oxygen on the outermost surface.
[0004] Japanese Patent Application Laid-Open No. 1-180961 International Publication No. 2017 / 199873 Japanese Patent Application Laid-Open No. 2000-212728 Japanese Patent No. 7175456
[0005] The present disclosure provides a method for producing a vapor deposition material used in a vacuum vapor deposition method, and an object of the present disclosure is to provide a vapor deposition material that can suppress bumping and splashing when the vapor deposition material is melted.
[0006] One aspect of the present disclosure is a method for producing a vapor deposition material made of a precious metal or a precious metal alloy, the method including the steps of melting and casting a raw material of the precious metal or precious metal alloy, forging and / or rolling, drawing, stripping, and cutting.
[0007] According to the present invention, both bumping and splashing can be suppressed when dissolving a deposition material. This can reduce particles adhering to a substrate and reduce raw material loss due to splashing. Therefore, it is expected that the product yield will improve and the product cost will be reduced.
[0008] The deposition material used in vacuum deposition is made by melting the raw material in a ceramic crucible such as alumina or a carbon crucible, and pouring the molten metal into a mold to produce an ingot. The resulting ingot is then machined into an appropriate shape (e.g., pellet), and the surface is washed with acid or an organic solvent to produce the desired product. The raw material used must have a purity of 3N (99.9 wt%) or higher, and after machining, the surface is chemically cleaned to remove any adhering materials.
[0009] Even when such high-purity raw materials and cleaned deposition materials are used, bumping (also called spitting) occurs during melting (deposition), causing particles to adhere to the substrate and reducing product yield. Furthermore, bumping contaminates the deposition equipment and the crucible, resulting in increased frequency of cleaning the equipment. Regarding this problem, the present applicant previously provided a technology (Patent Document 4) that can solve the above problem.
[0010] Patent Document 4 describes an excellent technique that can suppress bumping by removing nonmetallic inclusions such as hydrogen, carbon, oxygen, phosphorus, and sulfur, which are not usually included in the calculation of purity. Patent Document 4 also describes heat treatment (degassing) during wiredrawing (wire drawing). While this degassing is effective in removing the nonmetallic inclusions described above, it also forms micropores on the surface, which can cause splashing (droplet scattering).
[0011] Splashing differs from the bumping phenomenon in that it occurs when evaporation material melts and falls (when heated and melted before evaporation) and scatters as droplets into the surroundings. Because it occurs before evaporation, unlike the bumping phenomenon, particles do not adhere to the substrate, but splashing into the surroundings can lead to a loss of raw material. In particular, evaporation materials for precious metals (Au, Ag, Pt, Pd) are very expensive, and loss of raw material due to splashing immediately increases costs, so it is necessary to suppress splashing.
[0012] In view of the above problems, an embodiment of the present invention provides a method for producing a vapor deposition material that can suppress both bumping and splashing when dissolving the vapor deposition material. The method for producing a vapor deposition material according to this embodiment will be described in detail below.
[0013] <Raw Materials> In the present disclosure, "noble metal" refers to Au, Ag, Pt, or Pd, and "noble metal alloy" refers to an alloy of a noble metal with another metal. In particular, alloys with Ge, Sn, As, or Sb (e.g., Au—Sn, Au—Ge, Au—As, Au—Sb, Ag—Sn, Ag—Ge, Ag—As, Ag—Sb, Pt—Ge, Pt—Sn, Pt—As, Ag—Sb, Pd—Ge, Pd—As, Pd—Sb). These materials are relatively widely used in electronic components, semiconductor devices, magnetic devices, LEDs, organic electroluminescence (EL), LCDs, and the like. In particular, since noble metals are expensive, preventing unnecessary scattering due to bumping or splashing can offer cost benefits.
[0014] The vapor deposition material according to this embodiment preferably has a purity of 3N (99.9 wt%) or higher. A more preferred purity is 4N (99.99 wt%) or higher. By reducing the impurity content, the associated bumping phenomenon can be suppressed. However, even if a high-purity raw material is used, gas components such as carbon may not be considered as impurities in the purity calculation. Furthermore, since impurities may be mixed in during the manufacturing process, bumping cannot be prevented even when a high-purity raw material is used directly as a vapor deposition material. Carbon, in particular, covers the surface of the vapor deposition material (molten metal) during vapor deposition, causing bumping.
[0015] <Melting and Casting> A raw material (noble metal or noble metal alloy) with a purity of 3N (99.9 wt%) or higher is melted in air, vacuum, or an inert gas atmosphere (preferably in vacuum), and then cast to produce an ingot. Crucibles include ceramic crucibles, carbon crucibles, and copper crucibles, but it is preferable to use a high-purity copper crucible to avoid the incorporation of impurities. Furthermore, since carbon and other substances contained in the raw material float on the surface during melting, it is preferable to visually observe the ingot and remove the surface layer containing a large amount of carbon by acid washing or cutting. The amount of the surface layer removed depends on the total amount, but it is preferable to remove a thickness of 1 μm or more.
[0016] During melting, it is preferable to cast from the bottom of the crucible and not pour out the entire amount, leaving a portion in the crucible, or to remove the last molten metal, so as to avoid entraining carbon floating on the surface of the molten metal. Furthermore, when pouring the molten metal by tilting the crucible, foreign matter can be removed by providing a weir at the top of the crucible. The proportion of molten metal remaining unused in the crucible is preferably 0.1 wt % or more, more preferably 1 wt % or more. Furthermore, carbon and other floating particles can be removed by a zone melting method or the like.
[0017] <Forging and rolling> The ingot is forged and / or rolled. The purpose of forging and rolling is to form the ingot into a shape that can be fed into a wire drawing machine in the subsequent process. Therefore, either one or both of forging and rolling may be performed, and each process may be repeated. In addition, the order of the forging and rolling processes does not matter. For example, forging and rolling may be repeated multiple times, such as forging → rolling → forging → rolling.
[0018] <Wiredrawing> Wire drawing is performed to obtain the desired wire diameter. The cross-sectional shape may be round or rectangular. Note that using processing oil during wire drawing can cause contamination such as carbon, so it is preferable to avoid using processing oil. On the other hand, processing oil can be used if contamination caused by the processing oil can be removed in a subsequent process.
[0019] <Scalping> Scalping is performed. The purpose of the scalping is to remove impurities that have been mixed in during processes such as forging, rolling, and wiredrawing. In the scalping process, the deposition material member after wiredrawing is chemically etched with aqua regia or the like, or physically machined by cutting, polishing, or the like, to remove the surface layer of the processed deposition material. Since impurities such as carbon are not present only on the outermost surface of the deposition material member but are also embedded inside, it is preferable to scalp the surface layer 1 to 200 μm from the outermost surface. Although the scalping process is preferably performed after wiredrawing, it can also be performed in a step before wiredrawing, or after heat treatment or cutting, which will be described later.
[0020] <Heat Treatment Step> Heat treatment (degassing or softening treatment) may be performed before, during, or after wire drawing, or after scalping. Heat treatment is an optional step. The heat treatment temperature varies depending on the material, but it is usually preferable to perform the heat treatment at a temperature of 700°C or higher and below the melting point.
[0021] <Cutting and Cleaning> The film is cut to the desired length. After cutting, the surface can be cleaned using an acid or organic solvent to remove any foreign matter adhering to the surface. However, if an acid or organic solvent is used, it is necessary to thoroughly clean the film with pure water or a volatile component to remove any surface oxidation or residual carbon.
[0022] Next, examples of the present invention and comparative examples will be described. Note that the following examples are representative examples, and the present invention is not necessarily limited by these examples, and should be interpreted within the scope of the technical ideas described in the specification.
[0023] Example 1: A gold raw material with a purity of 4N (99.99 wt%) or higher was melted and cast into a gold ingot. This ingot was then rolled and drawn to obtain a gold wire with a diameter of 2.02 mm. This gold wire was then ground to a thickness of 10 μm as a scalping process. The diameter of the ground gold wire was approximately 2.00 mm. After scalping, the gold wire was cut into gold granules, 40 g of which were sampled and subjected to ultrasonic cleaning using ethanol to remove surface impurities. When the obtained gold granules (evaporation material) were subjected to electron beam (EB) melting, almost no bumping or splashing was observed, and almost no carbon film was observed on the surface of the ingot (evaporation material) after melting.
[0024] (Comparative Example 1) Except for not performing the skinning process, gold particles (evaporation material) were produced by the same manufacturing method as in Example 1. When these gold particles (evaporation material) were subjected to electron beam (EB) melting, a small amount of splashing was confirmed, and the surface of the ingot (evaporation material) after melting was covered with a carbon film.
[0025] Example 2: A gold raw material with a purity of 4N (99.99 wt%) or higher was melted and a gold ingot was cast. This ingot was rolled and drawn to obtain a gold wire with a diameter of 2.00 mm. This gold wire was then subjected to a 120 μm aqua regia etching (surface dissolution) as a scalping process. The diameter of the gold wire after etching was approximately 1.76 mm. After the scalping process, the gold wire was cut into gold granules, 40 g of which were sampled and subjected to ultrasonic cleaning using ethanol to remove surface impurities. When the obtained gold granules (evaporation material) were subjected to electron beam (EB) melting, almost no bumping or splashing was observed, and almost no carbon film was observed on the surface of the ingot (evaporation material) after melting.
[0026] (Comparative Example 2) Except for not performing the skinning process, gold particles (evaporation material) were produced by the same manufacturing method as in Example 2. When these gold particles (evaporation material) were subjected to electron beam (EB) melting, a small amount of splashing was confirmed, and the surface of the ingot (evaporation material) after melting was covered with a carbon film.
[0027] According to the present invention, both bumping and splashing can be suppressed when dissolving a deposition material. This can reduce particles adhering to a substrate and raw material loss due to splashing. The present invention is useful as a material for vacuum deposition, which is widely used in forming elements such as electronic components, semiconductor devices, optical thin films, magnetic devices, LEDs, organic EL displays, and LCDs.
Claims
1. A method for manufacturing a vapor deposition material made of a precious metal or a precious metal alloy, comprising the steps of melting and casting the raw material of the precious metal or precious metal alloy, forging and / or rolling it, drawing it, deskinning it, cutting it, and washing it, wherein the deskinning process is followed by a heat treatment step.
2. The method for manufacturing a vapor-deposited material according to claim 1, characterized in that the peeling process is performed by etching or machining.
3. The method for producing a vapor-deposited material according to claim 1 or 2, characterized in that the peeling process removes a surface layer of 1 to 200 μm from the outermost surface.
4. The method for producing a vapor-deposited material according to claim 1, characterized in that it includes a heat treatment step before, during, or after the wire drawing process.