Molten metal holding member and method for manufacturing the same

Abstract

The objective is to provide a molten metal holding member consisting of a deposition boat or crucible with improved wettability of the molten metal, and a method for manufacturing the same. [Solution] A molten metal holding member which is a deposition boat or crucible made of BN ceramics or composite ceramics containing BN, wherein at least the inner bottom surface is provided with a surface treatment film made of a titanium compound containing titanium nitride and titanium boride.

Description

Technical Field

[0001] The present invention relates to a molten metal holding member composed of an evaporation boat or crucible installed in a vacuum chamber and a method for manufacturing the same.

Background Art

[0002] In recent years, copper (Cu) films have been used in a variety of applications such as electrodes or functional thin films of display devices, wirings of printed wiring boards, and thin films for controlling optical properties and molecular permeation. For forming a Cu film, a vacuum evaporation apparatus is used. As an evaporation source installed in the vacuum chamber of the vacuum evaporation apparatus, those provided with a graphite crucible and heating means for induction heating an evaporation material filled in the crucible, and those provided with an evaporation boat and a power source for energizing the evaporation boat are generally used (see, for example, Patent Documents 1 and 2). And when forming a Cu film on a deposition object using such a vacuum evaporation apparatus, not only the quality of the Cu film but also an improvement in the film formation rate (productivity) is strongly demanded.

[0003] In order to improve the film formation rate, it is necessary to form a molten metal in which the evaporation material is melted and spreads wetly over a wide range on the surface of the crucible or evaporation boat. It is known that the wettability of the evaporation material with respect to the surface of the crucible or evaporation boat depends on the reactivity between the surface of the crucible or evaporation boat and the evaporation material, and the cleanliness of the surface of the crucible or evaporation boat. Here, when depositing a Cu film using an evaporation boat, usually, an evaporation boat made of carbon, or a ceramic evaporation boat obtained by sintering a raw material mainly composed of boron nitride and titanium boride for imparting conductivity to the evaporation boat and adding about two kinds of materials is used. However, when trying to deposit a Cu film using a ceramic evaporation boat, there is a problem that the wettability of Cu with respect to the surface of the evaporation boat is poor and it is difficult to form a molten metal that spreads wetly over a wide range. With this, there is a limit to improving the film formation rate.

[0004] Therefore, we previously proposed a vapor deposition source for a vacuum deposition apparatus in which the crucible is composed of ceramics or carbon and contains an additive metal material consisting of at least one metal element from titanium, zirconium, and vanadium, and is configured such that when the deposition material is dissolved in the crucible, the additive metal material dissolves into the molten deposition material (see Patent Document 3). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2011-23376 [Patent Document 2] Japanese Patent Publication No. 2018-176565 [Patent Document 3] Patent No. 7530533 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the technology described in Patent Document 3 does not improve the wettability of Cu to the surface of the vapor-deposited boat.

[0007] In view of the above, the object of the present invention is to provide a molten metal holding member comprising a deposition boat or crucible with improved wettability of molten metal, and a method for manufacturing the same. [Means for solving the problem]

[0008] To solve the above problems, we discovered that by applying a predetermined surface treatment film to the surface of a ceramic deposition boat or crucible, a molten metal holding member can be made from a deposition boat or crucible that improves the wettability of molten metal such as copper, and thus completed the present invention.

[0009] A first aspect of the present invention is a molten metal holding member which is a deposition boat or crucible made of BN ceramics or composite ceramics containing BN, wherein at least the inner bottom surface is provided with a surface treatment film made of a titanium compound containing titanium nitride and titanium boride.

[0010] A second aspect of the present invention is the molten metal holding member according to the above aspect, wherein the composite ceramic is a composite ceramic of BN and TiB2.

[0011] A third aspect of the present invention is a molten metal holding member according to the above aspect, wherein the surface treatment film is a titanium film in which nitrogen and boron of BN ceramics are diffused.

[0012] A fourth aspect of the present invention is the molten metal holding member according to the above aspect, wherein the surface treatment film does not contain titanium oxide and titanium.

[0013] A fifth aspect of the present invention relates to a method for manufacturing a molten metal holding member, comprising the steps of: forming a titanium coating film on at least the inner bottom surface of a molten metal holding member, which is a deposition boat or crucible made of BN ceramics or composite ceramics containing BN; and, after forming the titanium coating film, heat-treating it at 800°C or higher and less than 1668°C in a non-oxidizing atmosphere to make the titanium coating film a surface treatment film made of titanium nitride and titanium boride.

[0014] A sixth aspect of the present invention is a method for manufacturing a molten metal holding member as described above, wherein the heat treatment is performed such that the surface treatment film does not contain titanium oxide and titanium.

[0015] A seventh aspect of the present invention is a method for manufacturing a molten metal holding member as described above, wherein the heat treatment is performed by heating with an external heat source, resistance heating of the molten metal holding member itself, or dry firing in a vapor deposition apparatus. [Effects of the Invention]

[0016] In the present invention described above, by providing a surface treatment film made of a titanium compound containing titanium nitride and titanium boride on the inner bottom surface or the like of the molten metal holding member, the wettability with respect to molten metal such as Cu is remarkably improved, and the film forming rate of the vapor deposition apparatus can be improved.

Brief Description of the Drawings

[0017] [Figure 1] It is a figure which shows the result of the X-ray diffraction analysis of the surface treatment film of the molten metal holding member of Example 1.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, the present invention will be described based on embodiments.

[0019] The molten metal holding member of the present invention is a molten metal holding member which is an evaporation boat or crucible made of BN ceramics or composite ceramics containing BN, and at least on the inner bottom surface, it has a surface treatment film made of titanium nitride and titanium boride.

[0020] The molten metal holding member is an evaporation boat or crucible built into a vapor deposition apparatus or the like, and holds the molten metal of the vapor deposition material.

[0021] Since the molten metal holding member of the present invention has a predetermined surface treatment film, it will spread by wetting from the moment when a vapor deposition material such as Cu is introduced, and Cu can be vapor-deposited, and the film forming rate can be improved. Also, since there is no need to perform preparations such as weighing and introducing Ti or the like into the molten metal holding member, the preparation time for the vapor deposition operation can be significantly shortened.

[0022] The molten metal holding member of the present invention is BN (boron nitride) ceramics or composite ceramics containing BN which have been generally used conventionally. Examples of the composite ceramics include composite ceramics of BN and TiB2 (titanium diboride).

[0023] The surface treatment film of the present invention is obtained by diffusing boron and nitrogen from the underlying ceramics into a pre-applied titanium coating film, resulting in a mixed film of titanium compounds containing titanium nitride and titanium boride. The main components of titanium nitride and titanium boride are titanium diboride (TiB2) and titanium nitride (TiN), but there is a possibility of the presence of titanium nitride and titanium boride of other compositions, compounds containing titanium, nitrogen, and boron, and even titanium compounds containing other elements. As a result, the exact composition is largely unknown, and there is a possibility of a mixture of titanium compounds containing titanium nitride and titanium boride of various compositions.

[0024] In any case, by providing a surface treatment film made of such a titanium compound, the molten metal holding member has significantly improved wettability of molten Cu compared to a deposition boat or crucible made of BN ceramics or composite ceramics containing BN that does not have a surface treatment film.

[0025] The composition of such a surface treatment film is not particularly limited as long as it mainly consists of titanium nitride and titanium boride, but it must not contain titanium oxide or titanium.

[0026] The presence of titanium dioxide or titanium can cause adverse effects by reacting with molten copper (Cu). If titanium dioxide is present in the surface treatment film, it will sublimate at high temperatures due to its high vapor pressure. This sublimation in a vacuum can cause impurities in the product and can also cause bumping of the molten Cu during deposition. Furthermore, if titanium is present in the surface treatment film, it readily forms a Cu-Ti alloy molten metal with the molten Cu. This can result in areas with a thin or no surface treatment film in the deposition boat or crucible, leading to reduced wettability in some areas, hindering the wetting spread of the molten Cu, and ultimately slowing down the film formation rate.

[0027] Although the heat treatment is performed under a non-oxidizing atmosphere to exclude titanium oxide, if the heat treatment is performed under a nitrogen atmosphere instead of a non-oxidizing atmosphere, the nitrogen from the nitrogen atmosphere may diffuse into the surface treatment film and potentially form titanium nitride. However, the inclusion of such titanium nitride in the surface treatment film is not problematic. This is because the diffusion of nitrogen from a nitrogen atmosphere is not very fast and is not expected to have a significant impact on the diffusion of nitrogen and boron from the underlying ceramic layer, and therefore is not expected to affect the adhesion between the surface treatment film and the underlying ceramic layer. Furthermore, a lower titanium boride content on the surface side does not affect the wettability of molten metals such as copper.

[0028] Furthermore, creating a nitrogen atmosphere of a predetermined concentration is quite time-consuming and expensive, and variations in nitrogen partial pressure can lead to variations in the wettability of the molten metal. Therefore, it is preferable to perform the heat treatment in a device that utilizes a vacuum environment, such as a vacuum furnace.

[0029] An example of a method for manufacturing a molten metal holding member of the present invention comprises the steps of: forming a titanium coating film on at least the inner bottom surface of a molten metal holding member, which is a deposition boat or crucible made of BN ceramics or composite ceramics containing BN; and, after forming the titanium coating film, heat-treating it at 800°C or higher and less than 1668°C in a non-oxidizing atmosphere to make the titanium coating film a surface treatment film made of titanium nitride and titanium boride.

[0030] Further details are provided below. For example, a deposition boat or crucible made of composite ceramics consisting of BN and TiB2 is prepared, and a Ti film is formed on the surface where wettability of the molten metal is required, i.e., at least the inner bottom surface, by a known method. The method of forming the Ti film is not particularly limited and includes, for example, deposition, thermal spraying, sputtering, chemical plating, application of a suspension and drying. The thickness of the Ti film is not particularly limited, but is at least 1 to 100 μm, preferably 4 to 25 μm. The thickness of the Ti film corresponds to the thickness of the surface treatment film, but if it is thinner than this, the function as a surface treatment film will not be sufficient, and if it is thicker than this, the diffusion of nitrogen and boron from the ceramic will take time, the formation of the surface treatment layer will take time, and the effect will not improve, so it is not desirable. Furthermore, if the film thickness is too thick, there is a possibility of film peeling due to the difference in thermal expansion coefficients, so it is not desirable.

[0031] Next, the deposition boat or crucible with the Ti film attached in this manner is heated in a non-oxidizing atmosphere, preferably in a vacuum, at a predetermined temperature and for a predetermined time. As a result, the BN contained in the deposition boat or crucible reacts with the Ti in the Ti film, forming a film consisting of a mixture of Ti nitride and Ti boride on the surface of the deposition boat or crucible. This results in a deposition boat or crucible with good metallic wettability on its surface.

[0032] Here, the atmosphere for the heat treatment should be a non-oxidizing atmosphere, that is, an atmosphere that prevents oxidation of the Ti film formed on the deposition boat or crucible. For example, it should be in an inert gas such as nitrogen or argon, and preferably in a vacuum.

[0033] Furthermore, the heating temperature for the heat treatment is between 800°C and 1668°C. Below 800°C, there is a risk that unreacted Ti may remain within the feasible heating time, potentially resulting in areas with a thin or no surface treatment film on the deposition boat or crucible. This could lead to reduced wettability in some areas, which in turn could impair the wetting spread of the molten Cu, potentially resulting in a decrease in the film deposition rate.

[0034] On the other hand, at temperatures above 1668°C, the melting point of Ti is exceeded, causing the Ti film to melt and aggregate due to surface tension. As a result, a film consisting of a mixture of Ti nitride and Ti boride may not form in a portion of the deposition boat or crucible, potentially leading to reduced wettability in that portion.

[0035] The heating method is not particularly limited, and any known method that can heat the deposition boat or crucible to a predetermined temperature and time can be employed. One example is heating with an external heat source, for instance, by placing the deposition boat or crucible coated with a Ti film into a vacuum furnace and heating it using the heater inside the vacuum furnace as the heat source. Another example is utilizing the resistance heating of the deposition boat or crucible itself by passing a direct current or induced current through it. Furthermore, one example is to pre-coat the deposition boat or crucible with a Ti film and heat the empty container immediately before performing the deposition operation in a deposition apparatus to obtain a film consisting of a mixture of Ti nitride and Ti boride.

[0036] The heating time for the heat treatment should be sufficient for the BN in the deposition boat or crucible to diffuse and react with the Ti film, and the required time varies depending on the temperature. For example, the required heating time for each heating temperature can be determined by investigating the time it takes for the XRD peaks originating from Ti in the film to disappear using X-ray diffraction (XRD). Since lower temperatures require longer heating times, it is practically preferable to use a heating temperature of 1000°C or higher.

[0037] While various methods can be considered for forming coating films containing Ti nitrides and Ti borides, the molten metal holding member of the present invention, which forms a titanium coating layer on the surface of a deposition boat or crucible made of BN ceramics or composite ceramics containing BN, and then heat-treats it to diffuse nitrogen and boron from the substrate, thereby creating a surface treatment film containing Ti nitrides and Ti borides, exhibits significantly higher adhesion of the surface treatment film to the substrate compared to other coating films, preventing peeling or damage, and providing the effect of significantly higher wettability to molten metals such as Cu. [Examples]

[0038] The present invention will be described in more detail below based on examples.

[0039] (Example 1) A deposition boat made of BN and TiB2 composite ceramics was prepared, and a titanium film with a thickness of 4 μm was formed on its inner surface by sputtering. This deposition boat was heated under a vacuum atmosphere at 1000°C for 6 hours to obtain the molten metal holding member of the present invention.

[0040] Figure 1 shows the results of analyzing the surface treatment film of this molten metal holding member by X-ray diffraction (XRD). XRD was measured on the untreated surface of the deposition boat, the surface after titanium film formation, and the surface of the surface treatment film of the present invention after vacuum heat treatment. As a result, on the surface of the surface treatment film of the present invention, the peaks caused by Ti disappeared, and TiN, Ti2N, and TiN 0.3 It was found that the surface treatment film consists of Ti-N compounds such as TiB2 and TiB compounds such as TiB2 and TiB.

[0041] (Example 2) A molten metal holding member was prepared in the same manner as in Example 1, except that the titanium film thickness was set to 1 μm and heated at 1000°C for 2 hours.

[0042] Similarly, the surface treatment film of this molten metal holding member was analyzed by X-ray diffraction (XRD), and the peaks caused by Ti disappeared, indicating the presence of TiN, Ti2N, and TiN. 0.3 It was found that the surface treatment film consists of Ti-N compounds such as TiB2 and TiB compounds such as TiB2 and TiB.

[0043] (Comparative example) A commercially available deposition boat made of BN and TiB2 composite ceramics was prepared.

[0044] (Example test) In Examples 1 and 2, after placing Cu, which is the raw material for vapor deposition, into the molten metal holding member, the molten metal holding member was heated to 1800°C, causing the Cu to melt and the molten Cu to spread.

[0045] On the other hand, when the same Cu deposition material was placed in the comparative deposition boat and heated to 1800°C, the Cu melted but remained in droplet form and did not spread out. [Industrial applicability]

[0046] The molten metal holding member of the present invention significantly improves the wettability of molten Cu, but also exhibits excellent wettability for molten metals other than Cu, such as Ag and Al.

[0047] Furthermore, it can be applied not only to molten metal holding members, but also to components of vapor deposition equipment that require wettability of molten copper.

Claims

1. A molten metal holding member which is a deposition boat or crucible made of BN ceramics or composite ceramics of BN and TiB2, A molten metal holding member for molten copper, comprising a surface treatment film made of a titanium compound containing titanium nitride and titanium boride on at least the inner surface of the deposition boat or at least the inner bottom surface of the crucible, which are surfaces where wettability of the molten metal is required.

2. The Cu molten metal holding member according to claim 1, wherein the surface treatment film is a titanium film in which nitrogen and boron of BN ceramics or composite ceramics of BN and TiB2 are diffused, resulting in a titanium compound containing titanium nitride and titanium boride.

3. The molten metal holding member for molten Cu according to claim 1, wherein the surface treatment film does not contain titanium oxide and unreacted titanium.

4. A molten metal holding member is prepared, which is a deposition boat or crucible made of BN ceramics or a composite ceramic of BN and TiB2, and a titanium coating film is formed on at least the inner surface of the deposition boat or at least the inner bottom surface of the crucible, which are surfaces where wettability of the molten metal is required. A method for manufacturing a molten metal holding member for molten copper, comprising the steps of forming the titanium coating film and then heat-treating it at 800°C or higher and less than 1668°C in a non-oxidizing atmosphere to make the titanium coating film a surface treatment film composed of titanium nitride and titanium boride.

5. The method for manufacturing a molten metal holding member for molten Cu according to claim 4, wherein the heat treatment is performed in such a way that the surface treatment film does not contain titanium oxide and unreacted titanium.

6. The method for manufacturing a molten metal holding member for molten Cu according to claim 4, wherein the heat treatment is performed by resistance heating of the molten metal holding member itself, preheating in a vapor deposition apparatus, or heating with an external heat source other than the vapor deposition apparatus.

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