Metal material and plasma generator

Abstract

To provide a metallic material with an insulating oxide film that can sufficiently absorb an internal stress generated due to high temperature, having a sufficient corrosion resistance against plasma generation.SOLUTION: A metallic material of the present invention, whose surface layer has a porous oxide film, includes an insulation protective film with plasma resistance in the inner surfaces of multiple holes included in the porous oxide film.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a metal material having a porous oxide film on its surface and a plasma generator using the same.

Background Art

[0002] A surface treatment apparatus for performing surface treatment of a semiconductor wafer, for example, in order to wash away deposits (contaminants) deposited on the inner surface of the processing chamber after performing surface treatment of the semiconductor wafer, plasma generated by an external plasma generator is injected or irradiated, and the inner surface of the processing chamber may be plasma-treated. A plasma generator used for such applications is known to include, for example, a chamber having a reaction chamber into which a reactive gas is introduced, an electrode for supplying high-frequency power into the reaction chamber, and an outlet for discharging the plasma generated in the reaction chamber.

[0003] The chamber used in such a plasma generator is generally made of a metal material such as an alloy mainly composed of aluminum or magnesium. In the reaction chamber of this chamber, it is known that the inner surface of the reaction chamber is corroded by etching with the generation of plasma. In order to protect the inner surface of the reaction chamber from plasma etching, an insulating layer such as an oxide film formed by anodizing treatment (anodic oxidation treatment) is provided particularly on the inner surface portion of the metal material constituting the chamber.

[0004] As a technique for forming a film (insulating layer) having corrosion resistance and wear resistance on the surface of a metal material made of an aluminum alloy or a magnesium alloy, for example, Patent Document 1 discloses that a plasma electrolytic oxidation treatment (PEO) is performed on the surface of an aluminum substrate to form an oxide film including an amorphous and dense barrier layer and a porous layer composed of a plurality of hollow columnar cells. Although it is said that sufficient corrosion resistance can be obtained by such an oxide film, the thickness of the barrier layer is extremely thin at about several hundred nm, and it cannot be said that it is sufficient to obtain a sufficient effect when applied to the chamber of the plasma generator described above.

[0005] On the other hand, Patent Document 2 discloses a plasma electrolytic oxidation film having a dense layer containing pores with a pore diameter of 0.01 to 1 μm on the surface layer portion of a magnesium or magnesium alloy member. Further, Patent Document 2 also describes the problem that in a conventional plasma electrolytic oxidation film, since there are coarse pores with a pore diameter of about 1 to 30 μm, the corrosion resistance is reduced.

[0006] On the other hand, Patent Document 3 discloses a composite film having a porous oxide-ceramic matrix film formed on the surface of an alloy such as Al, Mg, Ti by a plasma electrolytic oxidation method, and a structure in which a functional compound is incorporated into the pores of the porous film. According to the composite film having such a structure, it is said to exhibit good wear resistance and a low friction coefficient, and have the ability to withstand dynamic contact loads and vibrations.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] The oxide film formed by plasma electrolytic oxidation treatment has a higher hardness than the oxide film formed by anodizing treatment, and also has the property of being able to absorb the internal stress at high temperatures based on the difference in thermal expansion coefficient with the base material by including a porous layer. On the other hand, the oxide film formed by plasma electrolytic oxidation treatment has a problem that since the pores formed inside are continuous with the pores, cavities are formed from the surface of the oxide film to the surface of the base material, resulting in a decrease in the insulation degree of the base material.

[0009] Regarding this point, although Patent Document 2 discloses a method of adjusting the pore diameter of pores to 0.01 to 1 μm, when trying to make the pore diameter of the pores smaller, the film formation rate also decreases, and there are problems in terms of productivity (production cost). Further, making the pores smaller sacrifices the ability to absorb internal stress, which is one of the characteristics of the oxide film formed by the above-described plasma electrolytic oxidation treatment.

[0010] On the other hand, Patent Document 3 discloses a method of allowing a functional compound to penetrate into the pores of the oxide film after forming the oxide film by plasma electrolytic oxidation treatment. However, since the pores for absorbing stress are filled with a functional compound having characteristics such as anti-wear and anti-corrosion, the ability to absorb internal stress, which is one of the characteristics of the oxide film formed by the above-described plasma electrolytic oxidation treatment, is sacrificed as in the case of Patent Document 2.

[0011] The present invention has been made based on these backgrounds, and particularly aims to provide a metal material having an insulating oxide film that has sufficient corrosion resistance against plasma generation and can sufficiently absorb internal stress generated at high temperatures, and a plasma generator using the same.

Means for Solving the Problems

[0012] In order to solve the above problems, one of the representative aspects of the present invention is a metal material having a porous oxide film on its surface layer, characterized in that a protective film made of an insulator having plasma resistance is formed on the inner surfaces of a plurality of pores included in the porous oxide film.

[0013] Another aspect of the present invention is a plasma generating device that applies high-frequency power to a reactive gas to generate plasma, comprising: a chamber having a reaction chamber into which the reactive gas is introduced; an electrode that supplies high-frequency power into the reaction chamber; and an outlet that discharges plasma from the reaction chamber, wherein the chamber is composed of a metal material having a porous oxide film on the surface layer on the reaction chamber side, and a protective film made of an insulator having plasma resistance is formed on the inner surfaces of a plurality of pores included in the porous oxide film.

[0014] According to the present invention having such a configuration, since a protective film made of an insulator having plasma resistance is formed on the inner surfaces of a plurality of pores included in the porous oxide film formed on the surface layer of the metal material, it has sufficient corrosion resistance particularly against plasma generation, and can sufficiently absorb the internal stress generated at high temperatures.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0016] Hereinafter, typical specific examples of the metal material according to the present invention and the plasma generator using the same will be described with reference to FIGS. 1 to 8.

[0017] <Example 1> FIG. 1 is a side view and a cross-sectional view showing an overview of the metal material according to Example 1, which is a typical example of the present invention. Further, FIG. 2 is an enlarged cross-sectional view schematically showing the portion indicated by the region A3 in FIG. 1(b). The metal material according to Example 1 can be applied as the metal material constituting the chamber of the plasma generator according to Example 2 described later.

[0018] As shown in FIG. 1(a), the metal material 10 according to Example 1 includes, as an example, a metal base material 20 and an oxide film 30 formed on at least one surface of the metal base material 20. Here, in FIG. 1(a), the case where the oxide film 30 is formed only on the upper surface of the metal base material 20 is illustrated, but the oxide film 30 may be formed on the entire surface including the side surface and the bottom surface of the metal base material 20.

[0019] The metal base material 20 is formed of a metal that can form a dense film by oxidizing its surface and can constitute the structural members of various structures. Examples of such a metal base material 20 include so-called light metals such as aluminum, titanium, and magnesium, and alloys thereof. In this Example 1, the case where an aluminum alloy of the 5000 series (Al-Mg series) or the 6000 series (Al-Mg-Si series) is applied as the metal base material 20 will be described.

[0020] The oxide film 30 is configured as an oxide having a two-layer structure including a porous layer 32 located on the metal base material 20 side and a dense layer 34 exposed on the surface side, as shown in FIG. 1(b) in which the region A1 in FIG. 1(a) is enlarged. As a method of forming such an oxide film 30, for example, plasma electrolytic oxidation, which forms a film of oxide by plasma electrolysis in an electrolytic solution such as an aqueous solution of potassium hydroxide (KOH), can be exemplified.

[0021] As shown in Fig. 1(c), which is an enlarged view of region A2 in Fig. 1(b), the porous layer 32 is composed of a base portion 32a made of an oxide such as aluminum oxide (Al2O3) and pore portions 32b dispersed between the base portions 32a. Here, the oxide constituting the base portion 32a can be arbitrarily selected according to the type of the above-described metal base material 20. And due to this porous layer 32, the pore portions 32b can absorb the stress caused by the difference in thermal expansion coefficient between the metal base material 20 and the oxide film 30, thereby suppressing the occurrence of cracks in the oxide film 30.

[0022] As shown in Fig. 2, the dense layer 34 is formed as a hard portion 34a made of an oxide such as Al2O3 by adjusting the conditions of plasma electrolysis in plasma electrolytic oxidation treatment. Note that the oxide constituting the hard portion 34a can also be arbitrarily selected according to the type of the above-described metal base material 20.

[0023] In addition, the dense layer 34 is formed with elongated through holes 34b that penetrate the hard portion 34a and reach the exposed surface 34c. These through holes 34b communicate with the pore portions 32b of the porous layer 32. As a result, the surface 20a of the metal base material 20 would be partially exposed to the external atmosphere (especially plasma) as it is.

[0024] Therefore, in the metal material 10 according to Example 1, as shown in Fig. 2, a protective film 36 made of an insulator having plasma resistance is formed on the inner surfaces of the pore portions 32b of the porous layer 32 and the through holes 34b of the dense layer 34. Thereby, for example, when the metal material 10 according to Example 1 is applied as the metal material constituting the chamber (reference numeral 110 in Fig. 7) of the plasma generating device (reference numeral 100 in Fig. 7) according to Example 2 described later, the etching of the inner surface of the chamber 110 by the generated plasma is suppressed.

[0025] As the material of the insulating substance constituting the protective film 36, it is a material having etching resistance by plasma, and is formed of, for example, ceramics such as oxides, nitrides, fluorides, carbides, etc. Among them, ceramics mainly composed of elements of Group 2, Group 3, Group 4, Group 13 or Group 14 of the periodic table are preferable. These ceramics can be selected by adjusting the atmosphere when forming the protective film 36.

[0026] Next, with reference to FIGS. 3 to 6, an outline of a method for manufacturing a metal material according to Example 1, which is a typical example of the present invention, will be described.

[0027] FIG. 3 is a flowchart showing the steps of the method for manufacturing a metal material according to Example 1. FIG. 4 is a partial cross-sectional view showing an outline of the step S2 shown in FIG. 3. FIG. 5 is a partial cross-sectional view showing an outline of the step S3 shown in FIG. 3. Further, FIG. 6 is a partial cross-sectional view showing an outline of the step S4 shown in FIG. 3.

[0028] As shown in FIG. 3, the metal material 10 according to Example 1 of the present invention, as an example, includes a step of preparing a metal base material 20 serving as a base material (step S1), a step of performing an oxidation treatment by plasma electrolysis on the surface of the prepared metal base material 20 (step S2), a step of applying a slurry, which is a precursor of the protective film 36, to the formed oxide film 30 (step S3), and a step of baking the metal material 10 to which the slurry has been applied (step S4).

[0029] In the step of preparing the metal base material 20 (step S1), the above-described 5000 series or 6000 series aluminum alloy is prepared with a predetermined surface property and shape. At this time, a step of previously removing the already formed oxide film or a step of adjusting the surface roughness of at least the surface on which the oxide film 30 is to be formed may be added.

[0030] In the step of performing plasma electrolysis (step S2), a oxide film 30 is formed on the surface of the metal substrate 20 by a known plasma electrolytic oxidation treatment. Specifically, as an example, the metal substrate 20 is immersed in a weakly alkaline electrolyte aqueous solution (potassium hydroxide KOH), and in this state, an alternating pulse current under predetermined conditions is passed through the electrolyte aqueous solution, whereby, as shown in FIG. 4, the oxide film 30 is formed on the surface 20a of the metal substrate 20.

[0031] In the step of applying the slurry (step S3), a slurry of a material that will ultimately become the precursor of the protective film 36 is applied to the exposed surface 34c of the oxide film 30. At this time, as described above, since a plurality of through-holes 34b are formed in the dense layer 34 of the oxide film 30, the applied slurry of the precursor is filled into the pore portions 32b of the porous layer 32 together with the through-holes 34b, as shown in FIG. 5. As an example, the slurry of the precursor of the protective film 36 is configured as a basic aqueous solution containing salts of the above-described Group 2, Group 3, Group 4, or Group 14 elements.

[0032] Subsequently, in the baking step (step S4), as an example, the metal material 10 coated with the slurry in step S3 is baked in a heating furnace under a predetermined gas atmosphere. At this time, due to the heating during the baking process, the basic component volatilizes together with the moisture contained in the slurry, so that, as shown in FIG. 6, the volume of the slurry greatly decreases and contracts in the direction of arrow B in the figure. Then, by the combination of the gas in the heating furnace and the above-described Group 2, Group 3, Group 4, Group 13, or Group 14 elements, a protective film 36 containing ceramics such as oxides and nitrides thereof is formed.

[0033] As described above, by appropriately selecting the atmosphere in the heating furnace (the reactive gas enclosed in the heating furnace) when performing the baking process (step S4), it becomes possible to adjust the material of the ceramics forming the protective film 36. For example, by baking a metal material 10 coated with a slurry containing titanium (Ti) of Group 4 in an atmosphere of nitrogen gas N2, a protective film 36 containing titanium nitride (TiN) is formed on the inner surface of the pore portion 32b in the porous layer 32 of the oxide film 30.

[0034] An example of a specific embodiment of the metal material manufactured by the method for manufacturing a metal material according to the above-described Example 1 will be described below with reference to FIG. 7. FIG. 7 is a graph showing an outline of the results of a plasma exposure test on a metal material according to the prior art and a metal material according to Example 1.

[0035] In conducting the plasma exposure test, using a 6000 series aluminum alloy as the metal substrate, samples were prepared by performing various film-forming treatments on the surface of the metal substrate, and tests were conducted by exposing them to these plasma generation environments. For the purpose of comparison between the present application and the prior art, an "anodized material" in which only anodizing treatment was performed on the surface of the metal substrate, a "PEO-treated material" in which only PEO treatment was performed on the surface, and a "material of the present invention" in which a protective film-forming treatment was performed in addition to PEO treatment on the surface were prepared.

[0036] As shown in FIG. 7, as the amount (thickness) of the film etched by plasma, a tendency for the etching amount to decrease appeared in the order of the "anodized material", the "PEO-treated material", and the "material of the present invention". In particular, as an example, the etching amount of the "material of the present invention" was approximately 40% less than the etching amount of the "PEO-treated material".

[0037] By having the configuration as described above, the metal material 10 according to Example 1 has a protective film 36 made of an insulator having plasma resistance formed on the inner surfaces of a plurality of pore portions 32b included in the porous oxide film 30 formed on its surface layer. As a result, it has sufficient corrosion resistance particularly against plasma generation and can sufficiently absorb internal stress generated at high temperatures.

[0038] <Example 2> In the technical field of manufacturing apparatuses for semiconductor products applied to semiconductor devices, solar panels, flat panel displays, etc., in order to remove contaminants and the like generated in various processing steps for a semiconductor substrate from a processing chamber, a plasma cleaning step of cleaning the wall surface by injecting plasma into the processing chamber may be performed. As an apparatus for generating such plasma, a remote plasma generation apparatus (RPS) that supplies plasma from the outside of the processing chamber is known.

[0039] FIG. 8 is a schematic diagram showing a configuration example of a plasma generation apparatus according to Example 2 of the present invention. Here, when explaining the plasma generation apparatus 100 according to Example 2, those having the same or similar configurations as in Example 1 are given the same reference numerals as in Example 1, and repeated explanations are omitted.

[0040] As shown in FIG. 8, the plasma generation apparatus 100 according to Example 2, as an example, includes a chamber 110 having a reaction chamber R into which a reactive gas is introduced, an electrode 120 that supplies high-frequency power into the reaction chamber R, and a discharge port 130 that discharges the plasma generated in the reaction chamber R. Then, the plasma generation apparatus 100 generates plasma by applying high-frequency power to the introduced reactive gas and discharges the plasma to a processing chamber of a manufacturing apparatus that manufactures a semiconductor device connected downstream from the discharge port 130.

[0041] The chamber 110 is connected at a position where an introduction pipe 112 for introducing a reactive gas therein faces the discharge port 130. And since the internal pressure inside the reaction chamber R increases due to the generation of plasma (the reactive gas expands due to the plasma reaction), the plasma generated from the reactive gas introduced at a predetermined pressure is discharged downstream of the chamber 110.

[0042] Also, as an example, the chamber 110 is formed of an aluminum alloy or a magnesium alloy, and is preferably configured as a columnar member having a circular or regular polygonal cross-section and a hollow interior. And on at least the inner surface of the chamber 110 on the reaction chamber R side, a oxide film 30 including the porous layer 32 described with the metal material 10 according to Example 1 is formed.

[0043] The electrode 120 is, for example, composed of a metal wound in a coil shape. Both ends of the electrode 120 are connected to a high-frequency AC power supply 122 via a pair of terminals 120a and 120b as shown in FIG. 8. By using the electrode 120 having such a shape, since no deviation occurs in distance by arranging the winding center of the electrode 120 at the center of the reaction chamber R of the chamber 110, the generation of plasma can be stabilized.

[0044] In the plasma generation device 100 shown in FIG. 8, a reactive gas is supplied into the reaction chamber R of the chamber 110 from a gas supply source (not shown) connected to the introduction pipe 112 at a predetermined pressure or flow rate. In this state, when a high-frequency alternating current is applied from the high-frequency AC power supply 122 to the electrode 120, plasma is generated inside the reaction chamber R of the chamber 110 by the magnetic field accompanying the current flowing through the electrode 120, and the generated plasma is discharged from the discharge port 130.

[0045] At this time, the inner surface of the reaction chamber R will be etched by the generated plasma. On the other hand, in the plasma generator 100 according to the second embodiment, since the same oxide film 30 as that shown in the first embodiment is formed on the inner surface of the chamber 110 on the reaction chamber R side, there is a protective film 36 made of an insulator having plasma resistance in the pores 32b of the porous layer 32. Therefore, even if the oxide film 30 is exposed to the plasma, it is possible to suppress the oxide film 30 from being etched.

[0046] In addition, since the electrode 120 will also be etched by the plasma generated between the electrode 120 and the chamber 110, it may be configured to be made of an aluminum alloy or a magnesium alloy and have an oxide film 30 formed on its surface in the same manner as the chamber 110. Further, in order to cool the heat generated during energization, the electrode 120 may be configured as a hollow tube made of an aluminum alloy or a magnesium alloy.

[0047] By having the above-described configuration, the plasma generator 100 according to the second embodiment, like in the case of the first embodiment, has a plurality of pores 32b on the surface of the porous oxide film 30 formed on the inner surface of the reaction chamber R side of the metal material constituting the chamber 110. Since the protective film 36 made of an insulator having plasma resistance is formed, it has sufficient corrosion resistance particularly against plasma generation and can sufficiently absorb the internal stress generated at high temperatures.

[0048] Note that the description in the above-described embodiment is an example of the metal material or the plasma generator according to the present invention, and the present invention is not limited to each embodiment. Further, those skilled in the art can make various modifications without departing from the spirit of the present invention, and these are not excluded from the scope of the present invention.

Explanation of Reference Numerals

[0049] 10 Metal material 20 Metal substrate 30 Oxide film 32 Porous layer 32a Base 32b void portion 34 dense layer 34a hard portion 34b through-hole 34c exposed surface 36 protective film 100 plasma generator 110 chamber 112 introduction pipe 120 electrode 120a, 120b terminals 122 high-frequency AC power supply 130 discharge port R reaction chamber

Claims

1. A metallic material having a porous oxide film on its surface layer, wherein the porous oxide film has a two-layer structure composed of a porous layer formed on the side of the metal substrate and a dense layer laminated on the porous layer, and a protective film made of an insulator having plasma resistance is formed on the inner surfaces of a plurality of pores contained in the porous layer while maintaining the internal space of the pores. The metallic material is characterized by this.

2. The metallic material according to Claim 1, wherein the protective film is composed of ceramics.

3. The metallic material according to Claim 2, wherein the ceramics contains oxides mainly composed of elements of Group 2, Group 3, Group 4, Group 13 or Group 14 of the periodic table.

4. A plasma generator that applies high-frequency power to a reactive gas to generate plasma, comprising a chamber having a reaction chamber into which the reactive gas is introduced, an electrode that supplies the high-frequency power into the reaction chamber, and an outlet that discharges the plasma from the reaction chamber, wherein the chamber is composed of a metallic material having a porous oxide film on the surface layer on the reaction chamber side, the porous oxide film has a two-layer structure composed of a porous layer formed on the side of the metal substrate and a dense layer laminated on the porous layer, and a protective film made of an insulator having plasma resistance is formed on the inner surfaces of a plurality of pores contained in the porous layer while maintaining the internal space of the pores. The plasma generator is characterized by this.

5. The plasma generator according to Claim 4, wherein the protective film is composed of ceramics.

6. The plasma generator according to Claim 5, wherein the ceramics contains oxides mainly composed of elements of Group 2, Group 3, Group 4, Group 13 or Group 14 of the periodic table.

Images