JP2010095774A - Method for producing surface-treated aluminum material for vacuum apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-treated aluminum material for a vacuum apparatus which has reduced defects in a film, and has excellent vacuum properties and corrosion resistance. <P>SOLUTION: In the method for producing the surface-treated aluminum material for the vacuum apparatus where a nonporous anodically oxidized film is formed on the surface of an aluminum material by electrolysis, the voltage to be applied upon the electrolysis is increased relatively at a high voltage increasing rate in the prestage and then increased relatively at a small voltage increasing rate in the poststage, while the voltage increasing rate in the prestage is controlled to 4.0 to 20.0 V/s, and the voltage increasing rate in the poststage is controlled to <4.0 V/s. Preferably, the period till within 20 s directly after the electrolysis (preferably, on and after 3 s directly after the electrolysis) is regarded as the prestage, and the time on and after that is regarded as the poststage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a surface-treated aluminum material for vacuum equipment suitable for vacuum equipment such as molecular beam epitaxy equipment, dry etching equipment, CVD equipment, ion plating equipment, plasma CVD equipment, and sputtering equipment. In particular, the present invention relates to a thermal CVD gas diffusion plate, chamber, valves, etc. that are heated.

In vacuum equipment such as CVD, since the vacuum characteristics are damaged if gas is released from the material constituting the equipment, aluminum materials that are relatively low in gas emission and can be reduced in weight are widely used. However, since aluminum materials have a problem of corrosion due to reaction gases used in vacuum equipment, in general, an anodized film, particularly a non-porous anodized film (barrier type anodized film) is formed to improve corrosion resistance. ing. The anodized film is formed on the surface of the aluminum material by electrolytic treatment of the aluminum material in an electrolyte solution (see, for example, Patent Document 1).
Japanese Patent No. 3152960

  By the way, recently, in a semiconductor manufacturing apparatus or the like, the degree of integration of ICs has increased, and the demand for reducing foreign substances generated from members has been increasing. The nonporous anodic oxide film may have film defects (swelling of the film, local breaking points) formed by electrolysis. The nonporous anodic oxide film is excellent in corrosion resistance at each stage with respect to a general anodic oxide film. However, even when forming a nonporous anodic oxide film, film defects (swelling of the film, local breakage points) may be formed by electrolysis, generating foreign matter in a vacuum environment, corrosion resistance, vacuum It has a problem of deteriorating characteristics.

  The present invention has been made in view of the above circumstances, and provides a surface-treated aluminum material for vacuum equipment that has few defects in the film, hardly generates foreign matter (particles), and is excellent in vacuum characteristics and corrosion resistance. For the purpose.

  That is, the manufacturing method of the surface treatment aluminum material for vacuum equipment of this invention WHEREIN: 1st this invention is the surface treatment aluminum material for vacuum equipment which forms a nonporous anodized film by the electrolysis on the surface of an aluminum material. In the manufacturing method, the applied voltage at the time of electrolysis is increased at a relatively large boosting speed in the previous stage and increased at a relatively small boosting speed in the subsequent stage, and the boosting speed in the preceding stage is set to 4.0 to 20 0.0 V / sec, and the step-up speed in the latter stage is less than 4.0 V / sec.

The nonporous anodic oxide film grows in proportion to the applied voltage. Since the aluminum base is oxidized and grows, the film is formed so that the film formed in the initial stage of electrolysis becomes the surface side, and the film formed after the middle stage of electrolysis becomes the aluminum base side. The properties of the coating surface layer are important for vacuum characteristics and corrosion resistance, and this surface layer is formed in the initial stage of electrolysis.
When the electrolytic treatment is performed at a high voltage increase rate, a dense and low moisture content film is formed. For this reason, a film surface layer with few defects can be obtained by relatively increasing the pressure increase speed V1 in the previous stage.
On the other hand, if electrolysis is continued while increasing the pressure increase rate, heat accumulates near the interface between the film and the aluminum substrate, voids and other defects are formed in the film, and the electrolyte component is taken in, resulting in reduced vacuum characteristics and corrosion resistance. descend. For this reason, it is necessary to relatively reduce the boosting speed V2 in the subsequent stage (V1> V2). According to the present invention, an excellent nonporous anodic oxide film having a dense upper layer and excellent corrosion resistance and no defects in the lower layer can be formed.

The boosting speed V1 at the preceding stage is in the range of 4.0 to 20.0 V / sec, and the boosting speed V2 at the succeeding stage is less than 4.0 V / sec.
When the pressure increase rate in the former stage is less than 4.0 V / sec, it is difficult to form a dense film with a low water content. On the other hand, when the treatment is performed at a pressure increase rate exceeding 20.0 V / sec in the previous stage, the heat generation of the film becomes too large, and defects such as voids are formed in the film. For the same reason, it is desirable that the boosting speed in the previous stage is 5.0 V / second or more, and 18.0 V / second or less.
Further, when the pressure increase rate at the latter stage is 4.0 V / second or more, heat is accumulated at the interface between the film and aluminum, and film defects such as voids are likely to be formed. For the same reason, it is desirable that the boosting speed is 2.5 V / second or less. It should be noted that if the subsequent boosting speed is too small, it takes a long time for electrolysis and is not efficient, so it is desirable to set the boosting speed to 0.1 V / second or more.

  The method for producing a surface-treated aluminum material for vacuum equipment according to the second aspect of the present invention is characterized in that, in the first aspect of the present invention, the first stage is within 20 seconds immediately after electrolysis, and the subsequent stage is the subsequent stage. .

By setting the time before the decrease in the pressure increase rate within 20 seconds immediately after electrolysis, it is possible to effectively avoid the occurrence of film defects thereafter. If the previous time exceeds 20 seconds, the film tends to be defective as described above. For this reason, it is desirable that the time of the previous stage be within 20 seconds immediately after electrolysis. In addition, the time of the front | former stage may be shorter than 20 seconds, and a back | latter stage may be started within the time of 20 seconds.
In addition, it is sufficient that the boosting speed is relatively large in each of the front stage and the rear stage, and the boosting speed may change in multiple stages or continuously change in the area of the front stage or the rear stage. Of course, a constant boosting speed may be maintained.

  In the method for producing a surface-treated aluminum material for vacuum equipment according to the third aspect of the present invention, in the first aspect of the present invention, 3 seconds from immediately after electrolysis and 20 seconds or less are set as the preceding stage, and the subsequent stages are set as the subsequent stage. It is characterized by.

  As described above, it is desirable that the time of the previous stage be within 20 seconds from immediately after electrolysis, but voltage fluctuation may occur transiently immediately after electrolysis, so that a stable boosted state is stopped. It is desirable to determine the magnitude relationship between the boosting speeds. Therefore, it is desirable to set the pre-stage region having the above-mentioned pressure increase speed after 3 seconds immediately after electrolysis.

  As described above, according to the method for producing a surface-treated aluminum material for vacuum equipment of the present invention, a method for producing a surface-treated aluminum material for vacuum equipment, in which a nonporous anodized film is formed by electrolysis on the surface of the aluminum material. , The applied voltage during the electrolysis is increased at a relatively large boosting speed in the previous stage and increased at a relatively small boosting speed in the subsequent stage, and the boosting speed in the preceding stage is set to 4.0 to 20.0 V. Since the pressure increase rate at the latter stage is less than 4.0 V / second, a non-porous anodic oxide film having a dense surface layer and a low water content and no defects on the inner layer side can be formed. In addition to preventing the occurrence of the above, there is an effect of obtaining excellent corrosion resistance and vacuum characteristics.

Hereinafter, an embodiment of the present invention will be described.
As the aluminum material used as the base material, JIS 5000 series and 6000 series aluminum alloys can be used. However, in the present invention, the aluminum material serving as the base material is not limited to a specific component system.
The material is subjected to a homogenization treatment as necessary, and further subjected to processing such as hot rolling and cold rolling. It is also possible to continuously cast and roll the material. In the present invention, these series of steps are not particularly limited. The aluminum material is subjected to cleaning, cutting treatment, etc., and then a nonporous anodic oxide film is formed.
Here, the nonporous anodic oxide film refers to pores that are regularly formed from the surface of the film to the aluminum substrate in the cross-sectional observation of the part where the film is uniformly formed (normally the opening is 1 to 10 nm). It is a nonporous film having a depth of 60% or more with respect to the film thickness, or 5% (ratio of the total area of the pores as viewed from the surface) or less. A non-porous film having a porosity of 0% is more preferable because it has much better corrosion resistance than a film having a porosity of several%.

  An aqueous solution containing boric acid or ammonium borate as an electrolyte is preferably used for producing the nonporous anodic oxide film. This is because the formation of a film using these electrolytes is extremely difficult to form pores, and is suitable for forming a thick film. In electrolysis, the solution concentration is preferably 1 to 30% by mass. The electrolysis temperature is preferably 50 ° C. or more from the viewpoint of crack resistance, and the upper limit is preferably 95 ° C. (the oxide film starts a hydration reaction) from the vacuum characteristics of the film.

As described above, the electrolysis voltage is preferably increased at a relatively high pressure increase rate immediately after electrolysis (and more preferably after 3 seconds immediately after electrolysis) to within 20 seconds at a relatively high pressure increase rate, and thereafter after the subsequent stage. Increase at a small boosting speed. The boosting speed in the former stage is 4.0 to 20.0 V / sec, and the boosting speed in the latter stage is less than 4.0 V / sec.
Depending on the above conditions, a nonporous anodic oxide film having a thickness of 300 to 700 nm and excellent corrosion resistance and vacuum characteristics can be formed. In the present invention, the thickness of the nonporous anodic oxide film is not limited.

Examples of the present invention will be described below.
100mm length x 100mm made of JIS5052 aluminum alloy (Fe 0.38%, Si 0.26%, Mn 0.08%, Cr 0.25%, Cu 0.10%, Mg 2.5%, balance Al and inevitable impurities) as the base material A plate material having a width of 7.0 mm was prepared, and 1.0 mm on both sides in the thickness direction was cut with a mill. Then, the oil was wiped off with acetone.
As pretreatment, first, degreasing with a neutral to weak alkaline degreasing agent or oil removal with an organic solvent was performed. Subsequently, 5% caustic soda was etched at 50 ° C. for 1 minute, and 10% nitric acid was neutralized at room temperature for 3 minutes.

  The sample subjected to the above pretreatment was immersed in the electrolytic solution shown in Table 1, a counter electrode was carbon, a positive direct current was applied, and electrolysis was performed under the following conditions. The applied current was adjusted to control the voltage boost rate as shown in Table 1 and FIG.

The sample after completion of electrolysis was washed with water for 10 minutes and dried at 100 ° C.
(Evaluation methods)
Corrosion resistance evaluation Measuring method: CF ₄ plasma, 500 W, irradiation for 24 hours, SEM observation of arbitrary 30 locations at 500 times (field of view: 0.1 mm × 0.1 mm), and the site where the base aluminum was observed is zero , 1-5 are ◯, 6-10 are Δ, 11 or more are X, and the results are shown in Table 1.
Vacuum characteristic evaluation Measuring method: The amount of gas released (Pa · m) when the specimen was heated to 300 ° C was measured.
Less than 1 Pa · m was marked as ◎, 1 to 10 Pa · m or less as ◯, 11 to 19 Pa · m as Δ, and 20 Pa · m or more as x, and the results are shown in Table 1.

  As shown in Table 1, in the present invention method (Examples 1 to 7) in which the pressure increasing speed was appropriately set in the former stage and the latter stage, results excellent in both vacuum characteristics and corrosion resistance were obtained. On the other hand, it was revealed that both the vacuum characteristics and the corrosion resistance were inferior if the conditions (pressure increase rate) of the present invention were not satisfied in either the former stage or the latter stage.

It is the figure (a figure) which shows the pressure | voltage rise speed change in each Example and comparative example of this invention, and its one part enlarged view (b figure).

Claims (3)

In the method for producing a surface-treated aluminum material for vacuum equipment, in which a nonporous anodic oxide film is formed by electrolysis on the surface of the aluminum material,
The applied voltage during the electrolysis is increased at a relatively large boosting speed in the previous stage and increased at a relatively small boosting speed in the subsequent stage, and the boosting speed in the preceding stage is set to 4.0 to 20.0 V / sec. The method for producing a surface-treated aluminum material for vacuum equipment, wherein the step-up pressure at the latter stage is less than 4.0 V / sec.   2. The method for producing a surface-treated aluminum material for vacuum equipment according to claim 1, wherein the first stage is within 20 seconds immediately after electrolysis, and the subsequent stage is the subsequent stage.   The method for producing a surface-treated aluminum material for vacuum equipment according to claim 1, wherein the first stage is from 3 seconds to 20 seconds immediately after electrolysis, and the subsequent stage is the subsequent stage.

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