JP2000282294A - Formation of anodically oxidized film excellent in thermal crack resistance and corrosion resistance and anodically oxidized film-coated member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the thermal crack resistance and corrosion resistance of a film by applying an AC/DC superposing method in which direct current is applied with alternating current and executing the treatment under an electrolyzing conditions in which the AC components do not contain negative components, and the AC components are contained in the DC components at a specified ratio. SOLUTION: An AC/DC superposing method is applied, and as to the electrolyzing conditions, the AC components do not contain negative components and contain by >=5% of the DC components. By the AC/DC superposing method satisfying the conditions, a structure in which each cell and/or pore composing an anodically oxidized film is fused and branched or a structure in which voids are introduced into a space between the adjacent cells or into the cell walls is formed. In the former structure, stress caused on the film under the environment of a heat cycle, or the like, is dispersed to prevent the generation of cracks. Moreover, in the latter structure, voids enable the relaxation of the stress caused by a heat cycle, or the like, and even if cracks are generated, by the effect similar to pinning, their propagation is suppressed. As a result, the corrosion resistance and wear resistance as the whole of the film can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming an anodic oxide film having excellent heat cycle cracking resistance and corrosiveness on Al or an Al alloy (hereinafter sometimes referred to as an Al alloy), and to such an anodic oxidation. Regarding the member on which the film is formed, specifically, as in a semiconductor manufacturing device or a liquid crystal manufacturing device,
Used in environments where it is heated above or below room temperature, cooled below room temperature, undergoes thermal cycling, or undergoes heat or thermal cycling due to friction or sliding, or is exposed to plasma containing halogen. And a method for forming such an anodic oxide coating. In addition, the anodic oxide coating member targeted by the present invention is not limited to the above-mentioned applications, and various vacuum vessels or components thereof, plasma reaction equipment members, heating equipment members, gas reaction equipment members, electrode materials, etc. Although it can be applied as various members used in such an environment, the description will be given below mainly on a semiconductor manufacturing apparatus.

[0002]

2. Description of the Related Art For example, an aluminum alloy (or Al) is mainly used in a vacuum chamber for a semiconductor manufacturing apparatus. Since it is exposed to various kinds of corrosive gas and plasma (for example, plasma containing halogen), it is difficult to maintain corrosion resistance and wear resistance to such an environment if the aluminum alloy is used as it is.

[0003] In view of the above, for the purpose of improving the corrosion resistance and wear resistance of an aluminum alloy, a portion exposed to the above environment is anodized to form a hard film called an alumite film on the surface of the aluminum alloy. It is generally done.

[0004] The above anodic oxidation treatment comprises oxalic acid, sulfuric acid, phosphoric acid,
An aluminum alloy is immersed in an electrolytic solution of an aqueous solution of boric acid, chromic acid or the like, or a mixed solution thereof, and a voltage is applied to the aluminum alloy surface by utilizing an oxidation phenomenon caused by oxygen generated at an anode. It forms a film. As the anodizing treatment, various methods such as a direct current method, an alternating current method, and an AC / DC superposition method are known as an energizing method. In the past, a direct current electrolysis method using a sulfuric acid aqueous solution was mainstream.

[0005] In recent years, attempts have been made to form a hard film exhibiting desired characteristics by devising various electrolysis conditions in anodizing treatment. For example, JP-A-7-6259
No. 5 proposes an anodized film-coated member with improved abrasion resistance, film adhesion and corrosion resistance by controlling the current density with an AC voltage waveform containing a negative component that generates hydrogen gas during anodization. Have been. Also, Japanese Patent Application Laid-Open No. 5-595
No. 67, after high-temperature processing of Mg-containing Al alloy, by performing alternating current electrolytic treatment by current density control in an alkaline solution to produce a laminated structure of aluminum oxide,
An anodic oxide coating member exhibiting excellent wear resistance, adhesion and corrosion resistance is also disclosed. Like this
In the anodic oxidation treatment performed in recent years, the alternating current method has become mainstream as seen in the above-described technologies, and the characteristics are generally improved by controlling the current density.

[0006]

However, even in the case of the anodic oxide film-coated member obtained by the above-mentioned prior art, an environment which undergoes a large temperature change during use, such as a vacuum chamber for a semiconductor device, is used. When plasma or plasma is exposed to a corrosive environment containing halogen, etc., penetrates from the surface of the anodic oxide film to the base material due to the stress generated due to the difference in linear expansion coefficient between the Al alloy base material and the film. Cracks (cracks) may occur.

[0007] The generated cracks cause deterioration of appearance and peeling of the film. Further, as a result of facilitating the entry of corrosive elements, not only the base material is corroded, but also the members themselves are deteriorated. , Causing contamination in the container. In addition, the peeling of the anodic oxide film makes it impossible to exhibit original properties such as wear resistance. Under these circumstances, there is a demand for an anodic oxide coating member excellent in heat crack resistance and corrosion resistance that can withstand use in the above-described environment.

The present invention has been made under such circumstances, and an object thereof is to provide an anodic oxide film-coated member having excellent heat crack resistance and good corrosion resistance, and an anodic oxide film exhibiting such characteristics. It is an object of the present invention to provide a useful method for forming

[0009]

Means for Solving the Problems The method of the present invention which has attained the above object is to apply an AC / DC superposition method in which an alternating current is applied to a direct current when forming an anodic oxide film on the surface of Al or an Al alloy. This is a method for forming an anodized film having a gist in that treatment is performed under electrolysis conditions in which an AC component does not contain a negative component and an AC component contains 5% or more of a DC component.

Here, "the AC component does not include a negative component" means that the potential of the material to be processed is always higher than the counter electrode.
“The AC component is contained at 5% or more of the DC component” means that the peak value of the AC component of the voltage between the workpiece and the counter electrode is 5% or more of the DC component.

On the other hand, the anodic oxide film-coated member of the present invention that has achieved the above object is an anodic oxide film-coated member having an anodic oxide film formed on the surface of an Al or Al alloy substrate. The film has a gist in that voids are formed between adjacent cells and / or cell walls.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In order to solve the above-mentioned problems, the present inventors have made intensive studies on the influence of electrolytic conditions in anodizing treatment on anodized films. As a result, if the AC / DC superposition method in which AC is applied to DC is applied, and anodization is performed under electrolysis conditions such that the AC component does not contain a negative component and the AC component contains 5% or more of the DC component, The present inventors have found that the heat cracking resistance can be significantly improved, the generation of cracks inevitably generated in the anodic oxide film to the Al alloy substrate can be suppressed, and good corrosion resistance can be maintained, and the present invention has been completed.

In the present invention, the AC / DC superposition method in which AC is applied to DC is applied. However, the AC / DC superposition method is conventionally used under the electrolysis conditions including a negative component and the current control to control the heavy metal element-containing Al. It has been studied from the viewpoint of uniform film formation and coloring performance improvement for alloys (for example,
JIS H9501 "Aluminum Chemistry and Surface Treatment", Kinki Aluminum Surface Treatment Research Group). However, no study has been made on voltage control that does not include a negative component, and the AC / DC superposition method itself has not been studied from the viewpoint of improving the heat cracking resistance and corrosion resistance of an Al alloy coated with an anodic oxide film.

In the present invention, such an AC / DC superposition method is applied, and the electrolysis conditions are specified such that the AC component does not contain a negative component and the AC component contains 5% or more of the DC component. Thus, an anodic oxide film having excellent heat cracking resistance and corrosion resistance was formed. Although not all of the reasons why these effects were obtained by the present invention could be elucidated, they could probably be considered as follows.
The mechanism will be described with reference to the drawings.

FIG. 1 is an explanatory view schematically showing the structure of the anodic oxide film by comparing the structure of the prior art with the present invention.
Fig. 1 shows the structure of the anodic oxide film formed by the conventional method.
(B) and (c) respectively show the structure of the anodic oxide film formed by the method of the present invention. FIG. 2 is a schematic view showing another structural example of the anodic oxide film formed by the present invention.

In the case where the anodic oxide film is formed by the AC / DC superposition method which satisfies the requirements specified in the present invention, the cells and / or the pores constituting the anodic oxide film are fused and branched. [FIG. 1 (b),
(C)], and a structure in which a gap is introduced between adjacent cells or in a cell wall (see FIG. 2). Of these structures,
The branched structure in which the cells and pores are fused is considered to disperse the stress generated in the film under an environment such as a thermal cycle, and reduce the occurrence of cracks. Alternatively, even if cracks occur in any part of the coating, no cells are formed linearly, so that no cracks penetrate and no corrosion components enter. In a film structure in which voids are introduced between adjacent cells or cell walls, the voids can relieve the stress generated during thermal cycling, etc., and even if cracks occur, the effect similar to pinning can be achieved. It is thought that the propagation is suppressed. And
Based on these results, the corrosion resistance and wear resistance of the entire film can be maintained.

On the other hand, in the film structure electrolyzed by the direct current method, the cells have a linear structure [see FIG. 1 (a)], and cracks easily develop between cells having a weak bonding force due to thermal stress. Easily reaches the Al base, so that the Al base is easily attacked by the corrosive gas.

On the other hand, when AC electrolysis including a negative component is performed,
Since the dissolution of aluminum is more likely to occur than the formation of the film, the film becomes too porous and is good in coloring and the like, but the film strength and wear resistance may be significantly reduced. In addition, hydrogen generated at the metal interface of the coating may diffuse into the coating and destroy the coating. Further, when a negative component is included, the space charge disappears due to the polarity change, and a high electric field is instantaneously generated at the time of the positive component to increase the current density.
It is considered that, due to these factors, the dissolution of the Al base material proceeds rapidly to form a linear cell structure, and the heat cracking resistance is reduced.

The specific structure of the anodic oxide film of the present invention is as follows: a portion where a plurality of cells or pores are branched and / or bonded is uniformly dispersed, and the branch portion or the bonded portion has a cell structure. Alternatively, it is preferable that there are five or more pores corresponding to a film thickness of 2 μm per ten pores. With such a film structure, the heat crack resistance of the anodic oxide film is significantly improved. Further, as a component in the anodic oxide film, it is preferable to include one or more of C, S, B, and P, since the film composition is likely to have a crosslinked structure and further performance improvement of the film can be achieved. .

FIG. 3 is a waveform diagram of the voltage (or current density) of the AC / DC superposition method. FIG. 3A shows the case of the present invention in which the AC component does not include a negative component, and FIG. Each of the conventional methods including a negative component in the AC component is shown. In the method of the present invention, when anodizing Al alloy, FIG.
Since the anodic oxidation treatment is characterized by a waveform as shown in (b), conditions such as the type of the electrolytic solution and the bath temperature are not particularly limited, but depend on the type of the electrolytic solution to be selected. It is necessary to appropriately determine the electrolysis conditions. In addition, in consideration of the structure of the generated film, it is necessary to include an AC component of 5% or more of the DC component in order to generate branches and voids.

Specific conditions for practicing the present invention will be exemplified. For example, when a 15% sulfuric acid aqueous solution is used as the electrolytic solution, the electrolysis conditions for forming the anodic oxide film are 5 to 30 V for voltage control and 0.1 to ^{2 A} / dm ² for current control. Preferably, there is. In the electrolysis conditions in the present invention, a DC component and an AC component can be set as follows within the range.

That is, the lower limit is set to the minimum value of the voltage or current density at which an anodic oxide film can be formed as a DC component (for a 15% sulfuric acid aqueous solution, a voltage of 5 V or more or a current density of 0.1 A / dm ² or more). In this case, it is preferable to set an electrolysis condition such that a negative voltage is not applied to the sample or a negative current does not flow to the sample. On the other hand, the upper limit is that the value of (DC component + AC component) is not more than the maximum anodizable voltage (30 V or less for a 15% sulfuric acid aqueous solution) or less than the maximum current density (2 A / dm ^{2 for a} 15% sulfuric acid aqueous solution). It is preferable to set the electrolysis conditions so that a negative voltage is not applied to the sample and no negative current flows. As for the frequency at the time of electrolysis, although the higher frequency side (100 Hz or more) is better than the lower frequency side (0.1 mHz or more), the improvement effect can be sufficiently exerted even at a normal frequency of 60 Hz or less. .

The Al alloy substrate (or Al substrate) targeted in the present invention is not particularly limited, and any Al alloy can be treated by applying the anodic oxidation treatment of the present invention. Although the performance can be improved, the alloy numbers are 1000 series (pure Al system) and 3000 series (Al-Mn).
System), 5000 system (Al-Mg system), 6000 system (Al
-Mg-Si system) or the like is desirable.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples do not limit the present invention, and any design change based on the above and following points is not limited to the present invention. It is included in the technical range of.

[0025]

EXAMPLES Various alloy plates (base material: 30 mm) shown in Table 1 below
× 40 mm) to produce anodic oxide films of various thicknesses under various conditions. The AC frequency was set to 60 Hz for convenience. 250 ° C1 in the atmosphere
After heating for an hour, the occurrence of cracks was visually evaluated according to the following criteria.

(Cracking resistance) ：: No cracking occurred, Δ: Total crack length 5 mm or less, ×: Overall cracking 5 mm or less.

Further, in order to investigate the corrosion resistance of the above sample to a halogen-based gas, the area of the sample was 20 mm.
Masking leaving 20 mm x 5 mm, 5% Cl gas 100
Exposure was performed at 250 ° C. for 2 hours at a flow rate of sccm, and the appearance of cracking was evaluated according to the following criteria.

(Gas corrosion resistance test) ○: No corrosion cracking occurred, ：: Corrosion area less than 5%, ×: Corrosion area 5% or more.

These results were determined based on the film thickness, electrolyte temperature,
The type of the electrolytic solution, the control electrolytic voltage, and the like are also shown in Table 1 below. Those satisfying the requirements specified in the present invention (No.
1 to 13), it is understood that the results of both the heat crack test and the gas corrosion test are good. On the other hand, in the case of no. 14 ~
21 shows that the heat crack resistance and the gas corrosion resistance are inferior.

[0030]

[Table 1] FIG. 4 shows an example of the film structure of the embodiment (micrograph as a substitute for a drawing).
FIG. 5 (micrograph as a substitute for a drawing) shows an example of a film structure of a comparative example. As is clear from FIG. 4, the branched structure can be easily confirmed by observing the cross section of the film with a transmission electron microscope (TEM). That is, in the film structure of FIG. 4, the portions that look white are the pores and the portions that look black are the cells. Unlike the comparative example shown in FIG. 5, the cells and pores are fused and branched. Can be confirmed.

[0031]

According to the present invention, an anodic oxide film-coated member having excellent heat cracking resistance and good corrosion resistance can be obtained as described above. Like a vacuum chamber for an apparatus, it is useful as a material that is exposed to an environment that undergoes a large temperature change during use or a corrosive environment including plasma containing halogen.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram schematically showing the structure of an anodic oxide film by comparing the structure of a conventional one with the present invention.

FIG. 2 is a schematic view showing another structural example of the anodic oxide film formed according to the present invention.

FIG. 3 is a waveform diagram of voltage (or current density) in the AC / DC superposition method.

FIG. 4 is a micrograph instead of a drawing showing an example of a film structure of an example.

FIG. 5 is a micrograph instead of a drawing showing an example of a film structure of a comparative example.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ikuo Hashimoto 1-5-5 Takatsukadai, Nishi-ku, Kobe In the Kobe Research Institute, Kobe Steel Ltd. (72) Inventor Toshiyuki Tanaka 1-chome, Takatsukadai, Nishi-ku, Kobe-shi No. 5-5 Inside Kobe Research Institute, Kobe Steel, Ltd.

Claims (2)

[Claims] In forming an anodic oxide film on the surface of Al or an Al alloy, an AC / DC superposition method in which an alternating current is applied to a direct current is applied, and the alternating current component contains no negative component and the alternating current component has a direct current component. A method for forming an anodic oxide film having excellent heat cracking resistance and corrosiveness, characterized in that the anodic oxide film is treated under electrolytic conditions containing 5% or more. 2. An anodic oxide film-coated member comprising an Al or Al alloy substrate having an anodic oxide film formed on the surface thereof, wherein the anodic oxide film has voids formed between adjacent cells and / or cell walls. An anodized film-coated member excellent in heat cracking resistance and corrosiveness, characterized in that it is a material.