JP5683077B2 - Aluminum alloy member with excellent low contamination - Google Patents

Description

  The present invention is a low-contamination property that is suitably used as a material for vacuum chambers of semiconductor and liquid crystal manufacturing equipment such as dry etching equipment, CVD equipment, ion implantation equipment, and sputtering equipment, or members provided inside the vacuum chamber. The present invention relates to an aluminum alloy member having excellent resistance.

  Anodization treatment that uses an aluminum alloy as a base material and forms an anodic oxide film on the surface to impart corrosion resistance (high-temperature gas corrosion resistance) and wear resistance to the aluminum alloy base material has been widely used. It has been.

  For example, various members such as a vacuum chamber used in a plasma processing apparatus of a semiconductor manufacturing facility and electrodes provided in the vacuum chamber are usually formed using an aluminum alloy. However, if the aluminum alloy is used as it is, corrosion resistance and wear resistance cannot be maintained. Therefore, the surface of the substrate formed of the aluminum alloy is subjected to anodizing treatment and anodized. By forming a film, corrosion resistance, wear resistance, and the like were imparted.

  The reason for forming the anodic oxide film on the surface of the aluminum alloy substrate is that, in the vacuum chamber, the object to be processed such as a silicon wafer is heated to a high temperature of room temperature to 200 ° C. or higher in the pre-processing step or manufacturing step of semiconductor manufacturing Since predetermined processing is performed with various types of corrosive gas and plasma in the environment, various parts such as the inner surface of the vacuum chamber and electrodes provided in the vacuum chamber are also exposed to the above atmosphere. This is because the solid aluminum alloy cannot maintain the corrosion resistance and wear resistance.

  In recent years, various proposals regarding such aluminum alloy members having an anodic oxide film formed on the surface have been made. From the viewpoint of reducing contamination of the workpiece, that is, reducing Fe, Cr, and Cu, Mg and Si are added to high-purity aluminum as a base material to be anodized, and the content of impurities The aluminum alloy base material which limited as much as possible is proposed as patent documents 1-7. When these aluminum alloys described in Patent Documents 1 to 7 are used as a base material, an effect can be expected for reducing the contamination of an object to be processed, and sufficient durability cannot always be obtained.

  As a measure for obtaining this sufficient durability, the anodizing aluminum alloy proposed by the present inventors is an anodizing aluminum alloy having both high durability, low contamination and high productivity described in Patent Document 8. It is. This aluminum alloy for anodic oxidation is an alloy that meets the needs for reducing metal contamination accompanying the recent high integration of devices. Among the members constituting the semiconductor manufacturing facility, the lower electrode member is a member that has a high possibility of becoming a contamination source for the wafer because the wafer is directly mounted thereon. For this reason, it is effective to reduce the metal contamination by adopting the anodizing aluminum alloy having both high durability and low contamination described in Patent Document 8 as the lower electrode member.

  However, the aluminum alloys described in Patent Documents 1 to 8, including the anodizing aluminum alloy described in Patent Document 8, are all aluminum alloys having a special component composition in which the reduction of impurity elements is as much as possible. For this reason, it is difficult to procure as compared with a commercially available aluminum alloy, and in the case of manufacturing, there is a problem that extra cost is required for the manufacturing.

  In addition, aluminum alloys for anodization that are actually used in plasma processing equipment for semiconductor manufacturing equipment are still mostly commercial aluminum alloys, and aluminum alloys with special compositions that require labor are required. Therefore, there is a long-awaited development of a technology that can respond to the recently increasing needs for low contamination even when a commercially available aluminum alloy is used.

JP-A-10-88271 JP 2004-99972 A Japanese Patent Laid-Open No. 2002-241992 JP 2002-256488 A JP 2003-119539 A JP 2003-171727 A JP 2008-70670 A JP 2008-45161

  The present invention has been made in order to solve the above-described conventional problems, and is an anodic oxidation used for various members such as a vacuum chamber used in a plasma processing apparatus of a semiconductor manufacturing facility and an electrode provided in the vacuum chamber. Low contamination that has been increasing in recent years regardless of the composition of the aluminum alloy used for the base material, even if it does not employ an aluminum alloy with a special component composition that requires labor to manufacture as the base material for the aluminum alloy An object of the present invention is to provide an aluminum alloy member excellent in low contamination that can meet the needs.

The invention according to claim 1 is an aluminum alloy member in which an anodized film is formed on a surface of a base material made of an aluminum alloy, and the anodized film has a barrier thickness between pores of 30 nm or less and has a surface side. A surface-side porous layer, and a substrate-side porous layer having a barrier thickness between pores of more than 30 nm and constituting the substrate side, wherein the surface-side porous layer has a layer thickness of 1 μm or more, the substrate side An aluminum alloy member excellent in low contamination, characterized in that the thickness of the porous layer from the substrate interface is 5 μm or more .

  According to the aluminum alloy member excellent in low contamination according to claim 1 of the present invention, it is used for various members such as a vacuum chamber used in a plasma processing apparatus of a semiconductor manufacturing facility and an electrode provided in the vacuum chamber. As a base material for the anodizing aluminum alloy to be produced, it has been increasing in recent years regardless of the composition of the aluminum alloy used for the base material, without employing an aluminum alloy having a special composition that requires labor for manufacturing. Can meet low pollution needs.

Moreover, it can be set as the aluminum alloy member excellent in the scratch resistance in addition to the outstanding low pollution property.

  Maintains corrosion resistance, wear resistance, etc. as materials for vacuum chambers of semiconductor and liquid crystal manufacturing equipment such as dry etching equipment, CVD equipment, ion implantation equipment, sputtering equipment, etc., or members provided inside the vacuum chamber In order to do so, an aluminum alloy member having an anodized film formed on the surface is adopted, but from the viewpoint of responding to the low contamination of needs that have been increasing in recent years, an aluminum alloy in which the content of impurities is limited as much as possible, It is starting to be used for the base material.

  However, it is difficult to produce an aluminum alloy with a special component composition in which the content of impurities is limited as much as possible, and there is a need to introduce a new production facility and the cost increases. The present inventors diligently conducted experiments and studies for the purpose of finding a new technique capable of realizing an aluminum alloy member excellent in low contamination even when an alloy is used.

As a result, by forming at least 1 μm or more from the surface side of the anodized film formed on the surface of the base material made of aluminum alloy as a surface-side porous layer having a barrier thickness between pores (voids) of 30 nm or less, It was found that even if a commercially available aluminum alloy was used, excellent low contamination could be secured, and the present invention was completed.

Further, a portion of the substrate side except for the porous layer of the anodized film, the barrier thickness between pores at 30nm greater, and that its thickness is to 5μm or more base material side porous layer, the low and the It was also confirmed that an aluminum alloy member excellent in scratch resistance in addition to contamination could be realized.

In addition, the barrier thickness between pores defined in the present invention is the distance between the pores closest to each other with respect to 10 or more adjacent pores when the surface of the anodized film is observed with a scanning electron microscope (SEM). Measure the shortest distance (minimum thickness of the solid part), and if the pore and the pore are connected, the barrier thickness between the pores is set to 0, and by calculating the measured average value, did. In addition to the surface of the anodized film, FIB (Focused Ion Beam) processing is also used for the position 1 μm from the surface side of the anodized film and the vicinity of the substrate interface and the position 5 μm from the substrate interface to the surface side. It cut out and observed with SEM. In the present invention, it is a requirement to form a surface-side porous layer having a barrier thickness between pores of 30 nm or less on the surface .

  Hereinafter, the present invention will be described in detail based on embodiments.

  The aluminum alloy member of the present invention comprises a base material made of an aluminum alloy and an anodized film formed on the surface of the base material.

  As a base material made of an aluminum alloy, it is not necessary to use an aluminum alloy having a special component composition, and a commercially available aluminum alloy, for example, a 6061 aluminum alloy defined in JIS can be used as the base material.

Further, the anodized film formed on the surface of the substrate is a surface-side porous layer having a thickness of 1 μm or more from the surface side (outermost surface) and a barrier thickness between pores of 30 nm or less. Although all of the anodic oxide film may be a the porous layer, the portion of the substrate side except for the surface side porous layer, the barrier thickness between pores at 30nm greater than the layer thickness is 5μm or more substrates side It is preferable to use a porous layer.

In the present invention, the barrier thickness between the pores has a requirement to form the following surface-side port Rasu layer 30 nm, the lower limit of the barrier thickness between the pores is not particularly specified. However, it is industrially difficult to control the barrier thickness between pores to less than 5 nm by the method described later, and the lower limit is preferably 5 nm.

Moreover, although the lower limit of the layer thickness of the surface-side porous layer having a barrier thickness between pores of 30 nm or less is defined as 1 μm, the upper limit is not particularly defined. However, from the viewpoint of scratch resistance, which will be described later, it is preferable to make the layer thickness as thin as 1 μm or more.

Furthermore, in the present invention, it was also recommended to form a substrate-side porous layer having a barrier thickness between pores exceeding 30 nm, but the upper limit of the barrier thickness between pores is not particularly defined. However, since it is not realistic to form the substrate-side porous layer having a barrier thickness between pores exceeding 100 nm, the upper limit is preferably set to 100 nm.

Moreover, although the minimum of the layer thickness of the base material side porous layer whose barrier thickness between pores exceeds 30 nm was prescribed | regulated as 5 micrometers, the upper limit in particular is not prescribed | regulated. However, from the viewpoint of scratch resistance, the thickness of the surface-side porous layer having a pore thickness of 30 nm or less between pores is 1 μm or more, and the thickness of the substrate-side porous layer having a barrier thickness between pores of more than 30 nm is The layer thickness is preferably as large as possible.

  In general, the anodized film is subjected to electrolytic treatment by immersing a base material made of an aluminum alloy in a treatment solution such as a sulfuric acid solution, an oxalic acid solution, a chromic acid solution, a phosphoric acid solution, or a mixed solution thereof to form an anode. Thus, it is formed on the surface of the base material made of an aluminum alloy as an anode. However, chromic acid solutions should be avoided because chromium is incorporated into the anodized film and causes contamination.

  The barrier thickness between the pores of the anodized film is determined by the size of the pores and the number density of the pores. The size of the pores and the pore number density vary depending on the temperature and processing voltage of the processing liquid. When a high-temperature processing liquid is used, the size of the pores increases, and when the processing is performed at a low voltage, the pore number density increases. Therefore, in order to reduce the thickness of the barrier between the pores, it is considered that low-voltage processing may be performed with a high-temperature processing liquid.

  However, the actual situation is that low-voltage processing using a high-temperature processing solution is not usually performed. It is necessary to prepare a heater or the like in order to increase the temperature of the processing liquid, and also to take measures to prevent the processing liquid from evaporating. This is because there are various disadvantages in that the formation rate of is slow and the productivity is poor.

Therefore, it is conceivable to employ a method in which an anodized film produced under normal anodizing treatment conditions is immersed in an acid or the like to be chemically dissolved and the pore diameter is expanded. For example, by immersing the anodized film in an aqueous solution containing fluorine such as hydrofluoric acid aqueous solution or buffered hydrofluoric acid solution (mixed aqueous solution of HF and NH ₄ F) and dissolving the vicinity of the surface of the anodized film, It is possible to form a surface side porous layer having a barrier thickness of 30 nm or less.

As an aqueous solution containing fluorine, the higher the fluorine concentration and the higher the temperature, the easier the chemical dissolution of the surface of the anodized film by the treatment solution occurs, and the barrier thickness between the pores can be increased in a short time. This is effective for forming a surface-side porous layer of 30 nm or less. However, on the other hand, if the chemical dissolution is too large, the film thickness becomes thin. Therefore, it is necessary to appropriately set the conditions, and depending on the type of the anodized film, for example, at room temperature (about 25 ° C.), 0.5 It is good to immerse in a ~ 1.0 mol / L hydrofluoric acid aqueous solution for 1-2 minutes.

  In addition, in order to impart wet corrosion resistance, the anodized film may be soaked in hot water or exposed to steam pressurization, so-called sealing treatment may be performed. Since the barrier thickness between the pores increases in the direction of decreasing the pore diameter, it is preferable not to apply them.

A wafer or the like is directly placed on the surface of the anodic oxide film. The surface side of the anodic oxide film that is in direct contact with the wafer or the like is a surface-side porous layer having a barrier thickness between pores of 30 nm or less. In addition, when the thickness of the surface-side porous layer is 1 μm or more, elements that cause metal contamination such as Fe, Cr, and Cu contained in the aluminum alloy diffuse to the wafer and the like through the anodized film. Therefore, it is thought that it can suppress the cause of contamination.

As described above, an aluminum alloy member excellent in low contamination can be obtained by using 1 μm or more from the surface side of the anodized film as a surface side porous layer having a barrier thickness between pores of 30 nm or less. However, it will be an aluminum alloy member with poor scratch resistance. Therefore, in the present invention, a portion of the substrate side except for the surface side porous layer of the anodized film, the barrier thickness between pores at 30nm greater than the layer thickness is set to 5μm or more base material side porous layer.

That is, by making the base material side of the anodized film a base material side porous layer having a layer thickness of 5 μm or more, an aluminum alloy member having excellent scratch resistance can be obtained.

In order to form this barrier layer on the anodized film on which the surface-side porous layer having a barrier thickness between pores of 30 nm or less is formed, the treatment voltage at the later stage of the anodizing treatment is set to This method is particularly effective, but it can also be formed by increasing the treatment time of the anodizing treatment (decreasing the film formation rate).

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, and the present invention is implemented with appropriate modifications within a range that can meet the gist of the present invention. These are all included in the technical scope of the present invention.

  First, 6061 aluminum alloy specified in JIS is melted to form an aluminum alloy ingot (size: 220 mmW × 250 mmL × t100 mm, cooling rate: 15 to 10 ° C.), and the ingot is cut and faced (size: 220 mmW × 150 mmL × t60 mm), and then subjected to soaking (540 ° C. × 4 h). After soaking, the 60 mm thick material was rolled into a 6 mm thick plate by hot rolling, cut (size: 220 mmW × 400 mmL × t6 mm), and then subjected to a solution treatment (510-520 ° C. × 30 min). After the solution treatment, water quenching was performed, and an aging treatment (160 to 180 ° C. × 8 h) was performed to obtain a match metal plate.

A test piece of 25 mm × 35 mm (rolling direction) × t 3 mm was cut out from the game metal plate and the surface thereof was chamfered. Next, after immersing in a 60 ° C.-10% NaOH aqueous solution for 2 minutes and then washing with water, and further immersing in a 30 ° C.-20% HNO ₃ aqueous solution for 2 minutes and then washing with water to clean the surface, Table 1 shows Anodization treatment was performed under each treatment condition to form an anodized film on the surface of the test piece. Here, an anodic oxide film having a thickness of 40 μm was formed, but the actually formed anodic oxide film had a thickness of 39 to 41 μm. Then, No. Except 1, the post-treatment of immersing the anodized film in hydrofluoric acid was performed under the conditions shown in Table 1.

  No. in Table 1 Under the conditions shown in 1 to 7, three test pieces were prepared, and the barrier thickness between pores of the anodized film, low contamination, and scratch resistance were investigated.

  As described above, the barrier thickness between pores of the anodized film formed on the surface of the test piece is obtained by observing the surface of the anodized film with a scanning electron microscope (SEM), and about 10 or more adjacent pores. , Measure the shortest distance (minimum thickness of the solid part) between the nearest pores, and if the pore and the pore are connected, the barrier thickness between the pores is 0, and the average value of the measured values That is. In addition to the surface of the anodized film, FIB (Focused Ion Beam) processing is also used for the position 1 μm from the surface side of the anodized film and the vicinity of the substrate interface and the position 5 μm from the substrate interface to the surface side. It cut out and observed with SEM. The measurement results are shown in Table 2.

The low contamination evaluation test was carried out by placing an Si substrate on each test piece that had been anodized under the conditions shown in Table 1, and simulating the usage environment of the lower electrode at 400 ° C., 1.5 × A vacuum heat treatment was performed for 2 hours under a reduced pressure of 10 ⁻³ Torr (2 Pa). Thereafter, the lower surface of the Si substrate in contact with the test piece was analyzed using total reflection X-ray fluorescence analysis (TXRF).

Since the low contamination required in an actual semiconductor manufacturing apparatus or the like differs depending on each process, use environment, etc., it is difficult to quantitatively set a reference value for low contamination. Therefore, in this evaluation test, the number of Fe atoms per unit area of the Si substrate surface measured using total reflection X-ray fluorescence analysis (TXRF) was 60 × 10 ¹⁰ atoms / cm ² or less. The anodized film of the test piece was judged to be excellent in low contamination. The test results are shown in Table 3.

  In addition, the scratch resistance evaluation test was carried out by a method in which distilled water was soaked into a sheet-like cotton (Asahi Kasei Bencotton) and the surface of the anodized film of the test piece was wiped 100 times. The film thickness of the surface of the anodized film after wiping was measured, and when the base material of the test piece was not exposed, it was judged that the anodized film of the test piece was excellent in scratch resistance. The test results are shown in Table 3.

No. The anodic oxide film 1 is a conventional anodic oxide film that has not been subjected to post-treatment immersed in hydrofluoric acid, and the barrier thickness between pores on the surface side of the anodized film exceeds 30 μm. As a result, the number of Fe atoms per unit area of the Si substrate surface measured using total reflection X-ray fluorescence (TXRF) exceeds 60 × 10 ¹⁰ atoms / cm ² and the Si substrate is contaminated. I was able to confirm.

No. The anodic oxide film 2 is an anodic oxide film formed by post-treatment immersed in hydrofluoric acid, but the barrier thickness between pores on the surface side of the anodic oxide film exceeds 30 μm. As a result, the number of Fe atoms per unit area on the Si substrate surface exceeded 60 × 10 ¹⁰ atoms / cm ^{2 or} more, and it was confirmed that the Si substrate was contaminated. No. 3 is also an anodic oxide film formed by performing post-treatment immersed in hydrofluoric acid, and the barrier thickness between pores on the surface of the anodic oxide film was 30 μm or less, but the position was 1 μm from the surface. The barrier thickness between pores exceeded 30 μm. As a result, the number of Fe atoms per unit area on the Si substrate surface exceeded 60 × 10 ¹⁰ atoms / cm ^{2 or} more, and it was confirmed that the Si substrate was contaminated. No. 2 and No. In No. 3, since it was too short to immerse in hydrofluoric acid, it can be assumed that such a result was obtained.

In contrast, no. In Nos. 4 to 7, since the processing conditions for forming the anodized film were appropriate, 1 μm or more from the surface side of the formed anodized film had a surface-side porous layer having a pore thickness of 30 nm or less between the pores. became. As a result, the number of Fe atoms per unit area of the Si substrate surface measured using total reflection X-ray fluorescence analysis (TXRF) is 60 × 10 ¹⁰ atoms / cm ² or less, and the anodized film of the test piece is Therefore, it can be judged that it is excellent in low pollution.

From this test result, an aluminum alloy member having excellent low contamination can be obtained by using a surface side porous layer having a barrier thickness between pores of 30 nm or less from the surface side of the anodized film to 1 μm or more. It could be confirmed.

  Moreover, it was judged that it was excellent in low pollution property No. 4-7, no. In Nos. 4 to 6, the barrier thickness between pores exceeds 30 nm at a position of 5 μm on the surface side from the substrate interface and in the vicinity of the substrate interface. As a result, in the scratch resistance evaluation test, the base material of the test piece was not exposed, and the scratch resistance was excellent.

  In contrast, no. In No. 7, the barrier thickness between pores was 30 nm or less at a position of 5 μm on the surface side from the substrate interface. As a result, no. In No. 7, the base material of the test piece was exposed in the scratch resistance evaluation test, and the scratch resistance was not excellent.

The test results of the anodized film, a portion of the substrate side except for the surface side porous layer, the barrier thickness between pores at 30nm greater than that thickness is to 5μm or more base material side porous layer It was confirmed that an aluminum alloy member excellent in scratch resistance could be obtained.

Claims (1)

An aluminum alloy member in which an anodized film is formed on the surface of a base material made of an aluminum alloy,
The anodized film has a surface-side porous layer having a barrier thickness between pores of 30 nm or less and constituting the surface side, and a substrate-side porous layer having a barrier thickness between pores exceeding 30 nm and constituting the substrate side And
An aluminum alloy member excellent in low contamination, wherein the surface-side porous layer has a layer thickness of 1 μm or more and the substrate-side porous layer has a layer thickness of 5 μm or more from the substrate interface .