Vapor deposition material, method for producing the same, and die

Abstract

An object of the present disclosure is to provide a vapor deposition material capable of suppressing bumping during vacuum vapor deposition, a method for producing the vapor deposition material, and a die used in the method for producing the vapor deposition material.SOLUTION: A method for producing a vapor deposition material, comprising: melting and casting a raw material; rolling and / or forging an ingot produced by the melting and casting; and drawing a member produced by the rolling and / or forging with a die, wherein the drawing is performed by blowing air or an inert gas without using a lubricating oil. When the surface of the vapor deposition material is analyzed using a scanning electron microscope, there is no deposit of 1 μm or more composed of the same component as the vapor deposition material.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a deposition material, a method for producing the same, and a die. [Background technology]

[0002] Vacuum deposition is a film formation technique that forms thin films by heating the deposition material in a vacuum and attaching the vaporized material in gaseous form to a substrate. Vacuum deposition is widely used to form elements such as electronic components, semiconductor devices, optical thin films, magnetic devices, LEDs, organic EL displays, and LCDs.

[0003] When a vapor deposition material is filled into a crucible and melted with an electron beam or the like, bumping (also called splashing) occurs, causing molten droplets to adhere to the thin film. To address this problem, a technique for preventing bumping by reducing the impurities contained in the vapor deposition material has been disclosed (Patent Document 1). Furthermore, Patent Document 2 describes washing the surface of the vapor deposition material with aqua regia to prevent the adhesion of molten droplets.

[0004] The applicant previously disclosed a technique for suppressing bumping during vacuum deposition of a gold deposition material used in vacuum deposition. For example, Patent Document 3 discloses a deposition material with a surface roughness Ra of 10 μm or less and a reduced number of microcracks with an equivalent circle diameter of 0.1 mm or more. Patent Document 4 also discloses a deposition material with an average crystal grain size of 0.1 mm or more, an oxygen content of 10 wtppm or less, and a hydrogen content of 5 wtppm or less. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 1-180961 [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-123389 [Patent Document 3] International Publication No. 2022 / 070432 [Patent Document 4] International Publication No. 2022 / 070433 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide a vapor deposition material that can suppress bumping during vacuum vapor deposition, a method for producing the same, and a die used in the production method. [Means for solving the problem]

[0007] The gist of the present disclosure is as follows. [1] A method for producing a deposition material, comprising the steps of melting and casting raw materials, rolling and / or forging the ingots produced by melting and casting, and drawing the rolled and / or forged parts using dies, in which the drawing step involves blowing air or an inert gas onto the parts without using lubricating oil. [2] The method for producing a deposition material according to [1], wherein the member is drawn while maintaining a surface temperature of 100°C or less. [3] A method for producing a deposition material according to [1] or [2], which comprises melting and casting in a vacuum or inert gas atmosphere. [4] The method for producing a vapor deposition material according to any one of [1] to [3], wherein the bell portion of the die has a convex curved surface or a multi-step surface. [5] The method for producing a vapor deposition material according to [4], wherein the radius of curvature of the convex curved surface is 20 mm or more and 100 mm or less. [6] The method for producing a vapor deposition material according to [4], wherein the multi-stage surface has a bell angle of the first stage of 60° or more and 80° or less, and a bell angle of the second stage of 30° or more and 50° or less. [7] The method for producing a deposition material according to any one of [1] to [6], wherein the wire drawing speed is 10 to 100 mm / min. [8] A die used in the method for producing a vapor deposition material according to any one of [1] to [7], wherein the bell portion of the die has a convex curved surface or a multi-step surface. [9] The die according to [7], wherein the radius of curvature of the convex curved surface or multi-step surface is 20 mm or more and 100 mm or less.

[10] The die described in [7], wherein the multi-stage surface has at least two stages, the bell angle of the first stage being 60° or more and 80° or less, and the bell angle of the second stage being 30° or more and 50° or less.

[11] A deposition material in which, when the surface of the deposition material is analyzed using a scanning electron microscope, there are no deposits of 1 μm or more that are made of the same components as the deposition material.

[12] The vapor deposition material according to

[11] , which contains one or more noble metals selected from gold, silver, palladium, and platinum. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to suppress the occurrence of bumping (splash) when melting a deposition material with an electron beam or the like. This can reduce adhesion of molten droplets to a substrate or a thin film, contributing to an improvement in product yield. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a cross-sectional schematic view of a die (having a convex curved bell portion) according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional schematic view of a die (having a multi-step bell portion) according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Evaporation materials can usually be produced through the following process: 1) The raw material (also called shot) is melted in the atmosphere, and the molten metal is poured into a mold to produce an ingot. 2) The ingot is forged or rolled to form the desired shape, and then drawn using lubricating oil. 3) The pellet is cut to the desired length to produce wire (rod-shaped). 4) The surface of the pellet is washed with acid or an organic solvent to remove impurities adhering to the surface.

[0011] However, the evaporation material produced by the above process encountered the problem of bumping during vacuum evaporation (when melted with an electron beam, etc.). A detailed investigation into the cause of this problem revealed that black areas were observed on the surface of the evaporation material, and that these black areas were caused by lubricating oil remaining in the processing marks (scratches). Most commonly used lubricating oils have a boiling point of around 600°C, and volatilize or decompose when precious metals such as gold (melting point 1080°C) are melted, which is thought to be the cause of bumping.

[0012] In the wire drawing process, lubricating oil is usually used to reduce friction between the deposition material member and the die. However, as mentioned above, the use of lubricating oil can cause bumping, so its use must be avoided. Here, water cooling and air cooling were considered as means for cooling frictional heat without using lubricating oil. While both means have advantages and disadvantages, water cooling poses a particular risk of corrosion to the equipment, etc., and is also highly susceptible to contamination, so air cooling was adopted in this disclosure.

[0013] The method for producing the vapor deposition material of this embodiment will be described in detail below. Note that the production conditions are merely examples and are not intended to be limiting. In addition, to avoid unnecessarily obscuring the disclosed production method, a description of well-known production steps will be omitted.

[0014] (Melting and casting process) Raw materials with a purity of 99.9% by weight or higher (preferably 99.99% by weight or higher) are melted in air, vacuum, or in an inert gas atmosphere (argon gas or nitrogen gas). In typical melting and casting processes, ceramic or carbon crucibles are used for air melting. However, using these crucibles in air can introduce impurities. Therefore, it is preferable to use less contaminated copper or carbon crucibles and EB (electron beam) or high-frequency melting. The melting temperature is preferably set between 50°C and 200°C above the melting point of the target metal. Below 50°C, the fluidity of the liquid is low, making it impossible to produce the desired cast ingot. Above 200°C above the melting point, metal evaporation loss occurs. Generally, metals melt in air due to their low affinity for oxygen. However, they still entrain gases such as oxygen and nitrogen from the air, which can degrade the ingot's properties and quality. Therefore, it is preferable to melt the raw materials in a vacuum or in an atmosphere containing an inert gas (degree of vacuum: 1000 to 0.001 Pa). The molten metal is then poured into a water-cooled copper mold and then cooled at room temperature to produce an ingot.

[0015] (Rolling process, forging process) To obtain a desired shape that can be processed in the wire drawing process, rolling or forging, or both, is performed. The rolling conditions (reduction ratio, number of passes, etc.) and rolling method (grooved roll rolling, etc.) can be selected as appropriate. Rolling may also be performed while heating. Heating at a predetermined temperature makes it easier to process into a desired shape. The heating temperature is preferably 300°C or higher. On the other hand, since heating at a temperature above the melting point of the target metal will cause part of the metal to melt, it is preferable to use a temperature that is at least 100°C lower than the melting point of the target metal.

[0016] (air-cooled wire drawing) The rolled deposition material member (approximately 10 to 50 mm thick) is drawn (wire-drawn) to a wire with a diameter of approximately 1 to 5 mm. The drawing may be performed only once, or the wire diameter may be gradually reduced using dies of different diameters. In this disclosure, air-cooled wire drawing is performed without using lubricating oil for the reasons mentioned above. Here, air-cooling in this disclosure refers to blowing air or an inert gas such as argon or nitrogen at a temperature of 30°C or less during wire drawing. Air-cooled wire drawing does not provide a lubricating effect, but since precious metals are particularly ductile, lubrication issues such as seizure are not particularly problematic as long as the die temperature rise due to frictional heat can be prevented. Furthermore, air-cooling can also blow away shavings (which have the same components as the deposition material) generated on the metal surface during wire drawing, preventing the shavings from becoming caught in the die and re-adhering to the member. It has been confirmed that air-cooling does not increase the oxygen concentration.

[0017] As an air-cooling method, for example, a cooling gas is preferably blown (compressor pressure: about 1 to 10 MPa) near the entrance side of the die (the side where the wire is inserted) to maintain the surface temperature of the member at 100°C or below. A more preferable method is 80°C or below, and particularly preferably 60°C or below. The wire-drawing speed is preferably 10 mm / min or higher and 100 mm / min or lower. More preferably, it is 30 mm / min or higher and 70 mm / min or lower. By controlling the wire-drawing speed, it is possible to suppress the temperature rise of the die. The air-cooling method is not limited to the above, and other air-cooling methods may also be used. Air-cooled thin wire can also be used with metal materials other than precious metals, as long as the material has excellent ductility.

[0018] (About the dice) Next, we will explain about dies. Dies are components with a roughly conical hole that is wide on the entrance side and narrow on the exit side, and by passing the wire through the die, the diameter can be reduced to the desired wire diameter. Various types of dies can be used. For example, carbide dies and diamond dies can be used. The die has several parts, from the entrance side where the wire is inserted, such as a bell part (to facilitate the inflow of lubricant), an approach part (to stop the vibration of the wire and guide it inside), and a bearing part. It consists of a ring section (which ultimately determines the wire diameter), a release section (which acts as a guide), etc. Of course, it may have other sections, and different names may be used for each section, but even if the names are different, they can be considered the same section as long as they have the same action and function.

[0019] 1 and 2 illustrate examples of the cross-sectional shape of a die according to an embodiment of the present disclosure. FIG. 1 shows an example in which the bell portion has a convex curved surface, and FIG. 2 shows an example in which the bell portion has a multi-step surface (two steps). The bell portion preferably has a convex curved surface or a multi-step surface. This allows for more effective suppression of vibrations when the wire passes through the die hole. Vibrations can cause scratches on the surface of the wire or the inner surface of the die hole, so it is preferable to suppress them as much as possible. When the bell portion has a convex curved surface, the radius of curvature is preferably 2 cm or more and 10 cm or less. Furthermore, when the bell portion has a multi-step surface (e.g., three steps), the first, second, and third steps, from the entrance side, preferably have a bell angle of 60° or more and 80° or less, a bell angle of 30° or more and 50° or less, and a bell angle of the third step that is smaller than that of the second step and larger than the approach angle. When four or more steps are provided, it is preferable that the fourth and subsequent steps have a bell angle that is smaller than the bell angle of the previous step and larger than the approach angle, as with the third step. The multi-step surface has at least two steps, but can also have three or four steps or more.

[0020] In the die according to the embodiment of the present disclosure, there are no particular limitations on the shapes or dimensions of the approach section, bearing section, and release section other than the bell section. For example, the angle of the approach section can be 11° to 17°. The length of the bearing section can be 0.3 to 0.5 times the diameter φ of the bearing section. Furthermore, the length of the release section can be 15% to 25% of the nib height (die height).

[0021] (Cutting and cleaning process) After wire drawing, the wire is cut to a predetermined length. The cutting length varies depending on the specifications, and is not particularly limited, but can be, for example, 10 mm or more and 30 mm or less. After cutting, the deposition material is washed with acid (aqua regia, hydrochloric acid, etc.), acetone, pure water, etc. to remove surface impurities. Note that washing can be performed not only after cutting, but also after the casting process, before and after the rolling process, and before and after the wire drawing process, as appropriate. In this way, the desired deposition material (rod-shaped) can be produced.

[0022] The deposition material according to the present disclosure preferably contains one or more precious metals selected from gold (Au), platinum (Pt), palladium (Pd), and silver (Ag). The content of the precious metal contained in the deposition material is preferably 99.9% by weight or more, and more preferably 99.99% by weight or more. Since impurities are one cause of bumping, bumping can be suppressed to a certain level by using high-purity products. However, since high-purity products are very expensive, it is preferable to select the purity of the precious metal to be used depending on the application and purpose. [Example]

[0023] 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.

[0024] In the examples and comparative examples, the analyses were carried out using the following equipment. (Scanning Electron Microscope: SEM) Analyzer: JSM-7000E (manufactured by JEOL) Measurement conditions: 100x magnification Measurement method: Samples with a diameter of 2 mm and a length of 20 mm were prepared, and 10 samples were randomly selected and analyzed.

[0025] Example 1 Gold raw material with a purity of 99.99 wt% or higher was melted by electron beam in a water-cooled copper crucible at a vacuum of 10 Pa to produce an ingot. The resulting ingot was acid-washed with aqua regia, degreased, and then rolled to a 20 mm square. It was then rolled repeatedly with a grooved roll to a 4.6 mm square. Next, air-cooled wire milling (air-cooling gas: argon) was performed without using lubricant. Wire milling was performed repeatedly using dies with different diameters (bearing section: φ4.7 mm, φ4.3 mm, φ3.9 mm, φ3.5 mm, φ3.2 mm, φ3.0 mm, φ2.7 mm, φ2.4 mm, φ2.2 mm, φ2.06 mm, bell curvature radius: 3 cm), gradually reducing the wire diameter to approximately 2.0 mm.

[0026] Visual inspection of the wired sample surface revealed no black areas, and SEM observation revealed no gold deposits larger than 1 μm. Analysis of the sample surface using energy dispersive X-ray spectroscopy revealed that the carbon content was less than 10 wt. Furthermore, when the sample was EB-melted, it was confirmed that bumping was significantly suppressed compared to wires made using conventional lubricants.

[0027] (Comparative Example 1) The ingot obtained in the same manner as in Example 1 was acid washed with aqua regia, degreased, and then rolled to a 20 mm square. It was then repeatedly rolled with a grooved roll to a 4.6 mm square. Then, thin wire was produced using lubricating oil. Using the same die as in Example 1, thin wire was repeatedly produced, gradually reducing the wire diameter to about 2.0 mm. Note that air cooling was not performed during the thin wire production.

[0028] Visual inspection of the thinned sample surface revealed black areas. Analysis of the sample surface using energy dispersive X-ray spectroscopy revealed that the carbon content was less than 10% by weight. Furthermore, when the sample was melted using EB, bumping occurred frequently.

[0029] (Comparative Example 2) The ingot obtained in the same manner as in Example 1 was acid washed with aqua regia, degreased, and then rolled to a 20 mm square. It was then repeatedly rolled with a grooved roll to a 4.6 mm square. Next, thin wire was produced without using lubricating oil. Using the same die as in Example 1, thin wire was repeatedly produced, gradually reducing the wire diameter to about 2.0 mm. Note that air cooling was not performed during the thin wire production.

[0030] When the surface of the thinned sample was visually inspected, no black areas were found, but when observed with an SEM, gold deposits of 1 μm or more were found. This is thought to be due to the inclusion of shavings (gold powder) from the thinning process. Furthermore, when the sample was melted with EB, more bumping occurred than in Comparative Example 1. [Industrial Applicability]

[0031] According to the present disclosure, bumping can be suppressed when dissolving a vapor deposition material. This is expected to reduce particles adhering to a substrate. This can contribute to improving product yield. The vapor deposition material of the present disclosure is useful for forming elements such as electronic components, semiconductor devices, optical thin films, magnetic devices, LEDs, organic EL displays, and LCDs.

Claims

1. A method for producing a deposition material, comprising the steps of: melting and casting raw materials; rolling and / or forging the ingot produced by melting and casting; and drawing the rolled and / or forged member using a die, wherein the wiredrawing step involves blowing air or an inert gas onto the member without using a lubricant.

2. The method for producing a deposition material according to claim 1 , wherein the member is drawn while maintaining a surface temperature of 100° C. or less.

3. The method for producing a deposition material according to claim 1, wherein the melting and casting are carried out in a vacuum or inert gas atmosphere.

4. The method for producing a deposition material according to claim 1 , wherein the bell portion of the die has a convex curved surface or a multi-step surface.

5. The method for producing a deposition material according to claim 4 , wherein the convex curved surface has a radius of curvature of 20 mm or more and 100 mm or less.

6. 5. The method for producing a vapor deposition material according to claim 4, wherein the multi-step surface has at least two or more steps, the bell angle of a first step being 60° or more and 80° or less, and the bell angle of a second step being 30° or more and 50° or less.

7. The method for producing a deposition material according to claim 1, wherein the wire drawing speed is 10 to 100 mm / min.

8. A die used in the method for producing a vapor deposition material according to any one of claims 1 to 7, wherein a bell portion of the die has a convex curved surface or a multi-step surface.

9. 9. The die according to claim 8, wherein the radius of curvature of the convex curved surface is 20 mm or more and 100 mm or less.

10. 9. The die according to claim 8, wherein the multi-step surface has at least two or more steps, the bell angle of the first step being 60° or more and 80° or less, and the bell angle of the second step being 30° or more and 50° or less.

11. A deposition material in which, when the surface of the deposition material is analyzed using a scanning electron microscope, there is no deposit of 1 μm or more made of the same components as the deposition material.

12. The vapor deposition material according to claim 11, which contains one or more noble metals selected from gold, silver, palladium, and platinum.

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