Vapor deposition material, its manufacturing method, and die

Abstract

An object of the present disclosure is to provide a deposition material capable of suppressing bumping during vacuum deposition, a method for producing the same, and a die used in the production method. [Solution] A method for producing a deposition material includes a step of melting and casting raw materials, a step of rolling and / or forging the ingot produced by melting and casting, and a step of drawing the member produced by rolling and / or forging with a die, wherein the drawing step involves drawing the wire by blowing air or an inert gas without using a lubricant. The deposition material is one in which, when the surface of the deposition material is analyzed using a scanning electron microscope, there is no adhesion of 1 μm or more that is made of the same components as the deposition material.

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 gas form to a substrate. Vacuum deposition is widely used to form elements in electronic components, semiconductor devices, optical thin films, magnetic devices, LEDs, organic electroluminescence (EL), LCDs, etc.

[0003] When a deposition material is filled in a crucible and melted by an electron beam or the like, bumping (also called splashing) occurs, causing molten droplets to adhere to the thin film. In response to this problem, a technique has been disclosed for preventing bumping by reducing impurities contained in the deposition material (Patent Document 1). In addition, Patent Document 2 describes how the adhesion of molten droplets can be prevented by cleaning the surface of the deposition material with aqua regia.

[0004] The applicant previously disclosed a technique for suppressing bumping during vacuum deposition of a gold deposition material used in a vacuum deposition method. For example, Patent Document 3 discloses a deposition material having 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 discloses a deposition material having 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] JP 2018-123389 A [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 deposition material capable of suppressing bumping during vacuum 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 ingot produced by melting and casting, and drawing the part produced by rolling and / or forging in a die, in which the drawing step does not use lubricating oil, but instead involves blowing air or an inert gas onto the part to draw the wire. [2] The method for producing a deposition material according to [1], further comprising the steps of: drawing the member while maintaining a surface temperature of the member at 100°C or lower. [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 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 deposition material according to [4], wherein the convex curved surface has a radius of curvature of 20 mm or more and 100 mm or less. [6] The method for producing a deposition material according to [4], wherein the multi-stage surface has a bell angle of a first stage of 60° or more and 80° or less, and a bell angle of a 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 an evaporation material according to any one of [1] to [7], wherein a bell portion of the die is a convex curved surface or a multi-step surface. [9] The die described in [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 that, when its surface is analyzed using a scanning electron microscope, has no deposits larger than 1 μm in size and made of the same components as the deposition material.

[12] The deposition material according to

[11] , which contains one or more precious metals selected from the group consisting of gold, silver, palladium, and platinum. Effect 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 onto a substrate or thin film, which can contribute to improving product yields. [Brief description of the drawings]

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

[0010] Evaporation materials can usually be produced through the following process: 1) The raw material (also called shot) is melted in the air, and the molten metal is poured into a mold to produce an ingot. 2) The ingot is forged or rolled into the desired shape, and then drawn using lubricating oil. 3) It 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 deposition material produced by the above process had a problem of bumping during vacuum deposition (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 deposition 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, a lubricant is usually used to reduce friction between the deposition material member and the die. However, as described above, the use of a lubricant causes bumping, so it is necessary to avoid using the lubricant. Here, water cooling and air cooling were considered as a means of cooling the frictional heat without using a lubricant. Although both means have advantages and disadvantages, water cooling has a particular risk of corrosion of the device, etc., and furthermore, the resulting contamination is high, so air cooling was adopted in this disclosure.

[0013] The manufacturing method of the deposition material of this embodiment will be described in detail below. Note that the manufacturing conditions are merely examples, and are not intended to be limited to these conditions. In addition, in order to avoid unnecessarily obscuring the disclosed manufacturing method, a description of a well-known manufacturing process will be omitted.

[0014] (Melting and Casting Process) Raw materials with a purity of 99.9% by weight or more (preferably 99.99% by weight or more) are melted in the air, or in a vacuum or in an inert gas atmosphere (argon gas or nitrogen gas). In general melting and casting, ceramic crucibles or carbon crucibles are used for air melting, but impurities may be mixed in when these crucibles are used in the air. Therefore, it is preferable to use EB (electron beam) melting or high-frequency melting using copper or carbon crucibles that are less contaminated. The melting temperature is preferably set to 50°C or more and 200°C or less from the melting point of the target metal. If the temperature is less than 50°C of the melting point, the fluidity of the liquid is low and the desired cast ingot cannot be obtained. If the temperature is more than 200°C from the melting point, evaporation loss of the metal occurs. Generally, metals melt in the air because of their low affinity with oxygen, but even so, gases such as oxygen and nitrogen in the air are involved, which deteriorates the properties of the ingot and also deteriorates the quality characteristics. 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) In order to obtain a desired shape that can be processed in the wire drawing process, rolling or forging, or both, are 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, if heating is performed at a temperature above the melting point of the target metal, part of the metal will melt, so the temperature is preferably 100°C or lower than the melting point of the target metal.

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

[0017] As an air-cooling method, for example, it is preferable to blow cooling gas (compressor pressure: about 1 to 10 MPa) near the inlet side (side where the wire is inserted) of the die so that the surface temperature of the member can be maintained at 100°C or less. More preferably, it is 80°C or less, and particularly preferably, it is 60°C or less. The wire-drawing speed is preferably 10 mm / min or more and 100 mm / min or less. More preferably, it is 30 mm / min or more and 70 mm / min or less. 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 be used. The air-cooled thin wire can also be used with metal materials other than precious metal materials as long as the material has excellent ductility.

[0018] (About the dice) Next, the dies will be described. A die is a component with a roughly conical hole that is wider on the entrance side and narrower on the exit side. By passing the wire through the die, the diameter can be narrowed to the desired wire diameter. Various types of dies can be used. For example, carbide dies and diamond dies can be used. The die is made up of the following sections: from the entrance side where the wire is inserted, a bell section (to facilitate the inflow of lubricant), an approach section (to stop the vibration of the wire and guide it inside), a bear section (to stop the vibration of the wire and guide it inside), and a wire feed section (to feed the wire inside). It consists of a ring section (which determines the final 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 show examples of the cross-sectional shape of the die according to the 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 is preferably a convex curved surface or a multi-step surface. This makes it possible to more effectively suppress vibration when the wire passes through the hole of the die. It is preferable to suppress vibration as much as possible because it causes scratches on the surface of the wire and the inner surface of the hole of the die. When the bell portion has a convex curved surface, the radius of curvature is preferably 2 cm or more and 10 cm or less. In addition, when the bell portion has a multi-step surface (e.g., three steps), it is preferable that the bell angle of the first step is 60° or more and 80° or less, the bell angle of the second step is 30° or more and 50° or less, and the bell angle of the third step 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 smaller than that of the previous step and larger than the approach angle, similar to the third step. Note that the multi-step surface has at least two steps, and can 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 and dimensions of the approach section, bearing section, and release section other than the bell section. For example, the angle of the approach section may be 11° to 17°. The length of the bearing section may be 0.3 to 0.5 times the diameter φ of the bearing section. In addition, the length of the release section may be 15% to 25% of the nib height (die height).

[0021] (Cutting and cleaning process) After drawing, the wire is cut to a predetermined length. The length to be cut varies depending on the specifications, and is not particularly limited, and 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 impurities from the surface. 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 drawing process, as appropriate. In this manner, 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, more preferably 99.99% by weight or more. Since impurities are one cause of bumping, bumping can be suppressed to a certain degree by using a high-purity product. On the other hand, 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. EXAMPLES

[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 instruments. (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 A gold raw material with a purity of 99.99 wt% or more was melted by electron beam in a water-cooled copper crucible at a vacuum of 10 Pa to produce an ingot. The obtained ingot was acid washed and degreased with aqua regia, then rolled to a 20 mm square, and further repeatedly rolled with a grooved roll to a 4.6 mm square. Next, air-cooled fine wire (air-cooled gas: argon) was performed without using lubricating oil. Fine wire was repeatedly made using dies with different diameters (bearing part: 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 part curvature radius: 3 cm), and the wire diameter was gradually reduced to about 2.0 mm.

[0026] When the thinned sample surface was visually inspected, no black areas were found, and when it was observed with a SEM, no gold deposits larger than 1 μm were found. In addition, analysis of the sample surface using energy dispersive X-ray spectroscopy revealed that the C content was less than 10 wt.%. In addition, when the sample was EB-melted, it was confirmed that bumping was significantly suppressed compared to when the thinned sample was made using conventional lubricating oil.

[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, and further repeatedly rolled with a grooved roll to a 4.6 mm square. Then, thin wire was made using lubricating oil. Thin wire was repeatedly made using the same die as in Example 1, and the wire diameter was gradually reduced to about 2.0 mm in diameter. Note that air cooling was not performed during thin wire making.

[0028] When the thinned sample surface was visually inspected, black areas were observed. Furthermore, analysis of the sample surface using energy dispersive X-ray spectroscopy revealed that the C 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, and further repeatedly rolled with a grooved roll to a 4.6 mm square. Next, thin wire was made without using lubricating oil. Using the same die as in Example 1, thin wire was repeatedly made, and the wire diameter was gradually reduced to about 2.0 mm in diameter. Note that air cooling was not performed during thin wire making.

[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 to be attached. This is thought to be due to shavings (gold powder) from the thinning process being caught in the sample. In addition, 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 the deposition material. This is expected to reduce particles adhering to the substrate. Therefore, it can contribute to improving the yield of products. The deposition material of the present disclosure is useful for forming elements in electronic components, semiconductor devices, optical thin films, magnetic devices, LEDs, organic EL, LCDs, etc.

Claims

1. A method for producing a deposition material, comprising the steps of: melting and casting a raw material; rolling and / or forging an ingot produced by melting and casting; and drawing, in a die, a member produced by rolling and / or forging, wherein the drawing step does not use a lubricant, and the member is drawn while maintaining a surface temperature of 100°C or less by blowing air or an inert gas onto the member.

2. 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.

3. 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.

4. The method for producing a deposition material according to claim 3 , wherein the convex curved surface has a radius of curvature of 20 mm or more and 100 mm or less.

5. 4. The method for producing a deposition material according to claim 3, wherein the multi-stage surface has at least two stages, a bell angle of a first stage is 60° or more and 80° or less, and a bell angle of a second stage is 30° or more and 50° or less.

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

Images