JPH09303289A - Surface treatment method for molecular pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the coagulation and accumulation of a process gas on an area around a rotor, and improve corrosion resistance by applying the constitution that a film made of a nickel-tin alloy film with tetrafluoroethylene resin coagulated like fine powder is formed on the process gas contact surface of a molecular pump. SOLUTION: Regarding a compound molecular pump to draw process gases through an intake port 12, and discharge the gases from an exhaust port 13, surface treatment is applied to the inner surface of the intake port 12 and the gas contact surface parts of each member of a rotor 1, a stationary blade 7, a distance piece 8, a stator 9 and a lower housing 11, all having process gas contact surfaces. In other words, the surface treatment is applied to the outer surface of each member in such a way as forming a nickel film, a nickel- phosphorous film. and a nickel-tin alloy film with ethylene tetrafluoride resin fine power coagulated. In this case, the nickel film is formed to have thickness between 0.1 and 2μm, and the nickel-phosphorus film to thickness between 1 and 20μm, using the electroless plating method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molecular pump widely used in industrial vacuum devices in the field of thin film industry.

[0002]

2. Description of the Related Art Molecular pumps include turbo molecular pumps, thread groove molecular pumps, and composite molecular pumps in which these are combined.

FIG. 8 shows an example of a vertical sectional view of a composite molecular pump.

That is, a turbo molecular pump part d and a thread groove molecular pump part e are sequentially arranged in a housing c having an intake port a and an exhaust port b, and a process gas is sucked from the intake port a. Exhaust from the exhaust port b.

In addition, f is a rotating shaft, g is a rotor fixed to the rotating shaft f, h is a motor for driving the rotating shaft f, and i and j
Respectively journal magnetic bearing and thrust magnetic bearing,
Further, k indicates a touchdown bearing.

In the field of thin film industry such as semiconductor manufacturing,
Molecular pumps are widely used for dry processes in vacuum such as thin film deposition process and etching process, but the process gas or reaction product sucked by the molecular pump is
Generation or adhesion / deposition is likely to occur inside the molecular pump, especially on the downstream side thereof, and these adhere firmly to the members of the molecular pump unit and cause the rotor to lock.

Therefore, in order to prevent these products from accumulating inside the molecular pump, measures have conventionally been taken such as heating by attaching a heater to the molecular pump.

Aluminum alloys and stainless steels are used in various places as materials for the components of these molecular pumps.

In particular, the rotor is often made of an aluminum alloy from the viewpoint of its lightness, workability and superiority in specific strength.

However, when the process gas is corrosive, the aluminum alloy is easily corroded and the life thereof is shortened.

For this reason, the surface of the aluminum alloy is subjected to alumite treatment, surface treatment with nickel plating or nickel-phosphorus film, or after the surface of the aluminum alloy is subjected to alumite treatment, the porous holes formed on the surface are formed. There is an example in which the surface treatment by Teflon coating in which a tetrafluoroethylene resin is embedded is applied to improve the durability against a corrosive process gas.

[0012]

[Problems to be solved by the invention] Adhesion of process gas
When the molecular pump is heated by a heater or the like in order to avoid deposition, a temperature detector and a temperature control device are required in addition to the heater, which causes a problem of increasing the cost of the device.

Further, due to this heating, there is a problem that the magnetic bearing part may malfunction, the durability of the insulating material and the material of the rotor may be deteriorated to shorten the service life, or the durability of the touchdown bearing may be deteriorated. there were.

Also, in the case where the above-mentioned Teflon coating is applied, since the surface is porous, a large amount of gas is released from it, which is not suitable as a surface treatment method for a molecular pump.

The present invention solves these problems, and the process gas does not adhere to the periphery of the rotor without heating.
It is an object of the present invention to provide a surface treatment method for a molecular pump which can prevent deposition and can sufficiently withstand a corrosive process gas.

[0016]

In order to achieve the above-mentioned object, the present invention uses a nickel-tin alloy film obtained by co-depositing tetrafluoroethylene resin in the form of fine powder on the contact surface with a process gas in a molecular pump. Is formed.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows the structure of a composite molecular pump, 1 is a rotor, 7 is a vane of a turbo molecular pump section, 8 is a distance piece, 9 is a stator of a thread groove molecular pump section, 10
Is an upper housing, 11 is a lower housing, 12 is an intake port, and 13 is an exhaust port. Aluminum alloy-based, iron-based, and stainless steel-based materials are used for these members.

Since the process gas is taken in through the intake port 12 and exhausted through the exhaust port 13, the inner surface of the intake port 12, the rotor 1, the vanes 7, the distance piece 8, the stator 9 and the lower housing 11 are It has a gas contact surface with the process gas, and the surface treatment method according to the present invention was applied to these gas contact surface portions.

FIG. 2 shows a partial cross-sectional view of the rotor 1 of the molecular pump which has been subjected to the surface treatment of the present invention.

The rotor 1 is made of an aluminum alloy and has a zinc film 2, a nickel-phosphorus film 4, and a tetrafluoroethylene resin fine powder (hereinafter referred to as PT) on its outer peripheral surface which comes into contact with the process gas.
A surface treatment of a nickel-tin alloy film 5 in which a FE fine powder) 6 is co-deposited is applied.

The surface treatment method will be described below.

In the case of an aluminum alloy member such as the rotor 1, after degreasing and activating the surface, the surface is modified into a zinc film 2 by a zinc substitution method.

Next, the nickel / phosphorus film 4 is formed by electroless plating. The nickel / phosphorus film 4 is excellent in corrosion resistance, has a micro Vickers hardness (hereinafter abbreviated as H _mv ) of 600 to 700, and has excellent wear resistance.

The composition of the nickel-phosphorus film 4 is such that the phosphorus content is in the range of 1 to 13%, and particularly 8 to 1
A range of 0% is preferred.

The nickel-phosphorus film 4 has a thickness of 1 to 2
The range is 0 μm, and the range of 10 to 20 μm is particularly preferable. This is because if the nickel / phosphorus film 4 is thin,
This is because it does not help to maintain the surface hardness of the surface treatment layer at H _mv 500 or higher.

Next, on the uppermost surface, a nickel-tin alloy film 5 in which PTFE fine powder 6 is co-deposited is formed by electroplating to form a composite film.

The PTFE fine powder 6 has a particle size distribution of 3 to 8 μm.
Those having a uniform particle size in the range of m are preferable. This is because, when the particle size of the PTFE fine powder 6 is as fine as 0.3 to 0.8 μm, the mold release performance of the nickel-tin alloy film 5 co-depositing PTFE is deteriorated.

The thickness of the nickel-tin alloy film 5 is preferably 1 to 50 μm, and particularly preferably 5 to 20 μm.

The composition ratio of nickel and tin of the nickel-tin alloy film 5 is in the range of 5:95 to 95: 5, and preferably in the range of 20:80 to 60:40.

It is generally known that the nickel-tin alloy film 5 is subjected to a heat treatment at a temperature of 100 to 500 ° C. for 1 to 2 hours after the film formation, so that the hardness of the film is increased and the releasing performance is also improved. ing.

However, the melting point of the eutectoid PTFE fine powder 6 is 300 to 330 ° C., and the heat treatment at a temperature exceeding this melting point, on the contrary, lowers the releasing performance.

Furthermore, since the aging treatment temperature of the aluminum alloy is about 150 to 180 ° C., when the present invention is applied to a molecular pump member made of aluminum alloy, it is possible to perform 1 after film formation.
The heat treatment is preferably performed at a temperature of 00 to 150 ° C.

The iron or stainless steel molecular pump member is preferably subjected to heat treatment at a temperature of 250 to 300 ° C. after the film formation.

The surface treatment of the molecular pump member made of iron or stainless steel does not require the zinc coating 2 described above.

That is, the oxide film on the surface of the iron or stainless steel member to be surface-treated is removed by acid cleaning with hydrochloric acid or the like, and the nickel film 3 and the nickel-phosphorus film are formed thereon as shown in FIG. 4, and a coating layer composed of three nickel-tin alloy films 5 co-deposited with the PTFE fine powder 6 is laminated.

This nickel film 3 is formed by the nickel strike method. The nickel film 3 is necessary for maintaining the adhesion of the film formed by the subsequent surface treatment to the base material. The nickel film 3 has a thickness of 0.1 to 2.0 μm, preferably 0.5 to 1.0 μm. This is because as the nickel film 3 becomes thicker, a film having a non-uniform thickness is likely to be formed, which may cause unevenness in the film to be laminated next.

In order to prevent the process gas containing the cohesive suction substance from adhering and depositing around the rotor of the molecular pump, the rotor 1 and its adjacent members are made of a material having a small surface energy. As a result of diligent research, it was found that the nickel-tin alloy film 5 and PTFE fine powder 6 were co-deposited, and the composite film was extremely effective in terms of releasability and corrosion resistance to reaction products. Therefore, the present invention has been achieved.

According to the method for treating the surface of a molecular pump of the present invention, a strong composite film can be formed for various materials such as aluminum alloy-based and stainless steel-based materials. Not only does not easily adhere to the surface of the member, but even if it adheres, the adhesive strength is significantly reduced.

The product does not grow like a film on the surface of the member but grows in a granular form, and when its tip comes into contact with the rotating rotor 1, it easily separates from the surface of the member and falls. It does not accumulate around the rotor part.

Next, the film formed by the surface treatment method of the present invention was evaluated for the following three points.

(1) A comparison test of film characteristics was conducted for the nickel-phosphorus film by the conventional surface treatment and the surface-treated film of the present invention.

FIG. 4 shows an example of the results of the film characteristic comparison test.

According to FIG. 4, the surface-treated film of the present invention is
The corrosion resistance is slightly inferior to that of the nickel-phosphorus film, but the adhesion property to various substances is remarkably low, which indicates that the material adhered to the film is easily peeled off.

Further, although the surface-treated film of the present invention is slightly inferior in wear resistance to the nickel / phosphorus film, it can be seen from the results of the surface tension test that it is superior in water repellent property to the nickel / phosphorus film.

(2) A vacuum vapor deposition apparatus was used to perform a comparative test of the adhesion of vapor deposited films when tungsten was vapor deposited.

The samples for comparison were an aluminum alloy plate, a SUS304 plate, a plate coated with a nickel / phosphorus film, and the surface-treated film-coated plate of the present invention.

The tungsten deposition conditions are as follows. Deposition equipment Showa Vacuum Co., Ltd. SGC-16SA Electron beam 6v 500mA Raw material 3N grain-shaped tungsten Deposition start vacuum degree 2.0 × 10 ^-5 Torr Deposition vacuum degree 7.0 × 10 ^-5 Torr or less Between evaporation source and sample Distance 700mm Deposition time 100min Sample temperature about 180 ℃

A peeling test was performed on the tungsten vapor-deposited on each sample plate under the above conditions using a cellophane tape.

That is, a cellophane tape was attached on vapor-deposited tungsten, and a peeling test was conducted several times. As a result, the vapor-deposited tungsten film was easily peeled from the surface-treated coated plate of the present invention. It was found that the tungsten vapor deposition film of the sample did not come off with the cellophane tape, but adhered firmly.

This indicates that the surface-treated film of the present invention has properties suitable for a vacuum pump of a vacuum evaporation vacuum device such as tungsten.

(3) Various materials and water repellent comparative tests were conducted.

The samples for comparison were aluminum plate, aluminum alloy plate, SUS304 plate, nickel.
They are a phosphorous film coated plate and a surface-treated film coated plate of the present invention.

Pure water, TEOS for these samples
(Tetraetoxysilane) and TMOS (Tetrametoxysilan)
Each example of the contact angle measurement test result by e) is shown in FIGS.
Shown in

From these contact angle measurement results, it can be seen that the surface treatment film of the present invention has the largest contact angle with respect to any liquid, and thus the surface treatment film of the present invention has the highest water repellency.

In this embodiment, the nickel-tin alloy film is a composite film obtained by co-depositing PTFE in the form of fine powder.
This may be another fluororesin having a glass transition point of 260 ° or more co-deposited into a fine powder, for example, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, hexafluoropropylene and the like. Examples thereof include copolymers of tetrafluoroethylene and copolymers of chlorotrifluoroethylene and vinylidene fluoride, and among them, tetrafluoroethylene resin (PTFE)
Is preferred.

[0058]

As described above, according to the present invention, it is possible to prevent the process gas from adhering and depositing around the rotor without heating the molecular pump with a heater or the like, and to withstand the process gas having corrosive properties. It is possible to provide a method for treating the surface of a molecular pump.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing the structure of a composite molecular pump.

FIG. 2 is a partial cross-sectional view of the above.

FIG. 3 is a partial cross-sectional view of another member of the above.

FIG. 4 is an example of the results of a film characteristic comparison test.

FIG. 5 is an example of a contact angle measurement test result.

FIG. 6 is another example of the same.

FIG. 7 is another example of the same.

FIG. 8 is an example of a vertical cross-sectional view of a composite molecular pump.

[Explanation of symbols]

 2 Zinc film 3 Nickel film 4 Nickel / phosphorus film 5 Nickel / tin alloy film 6 PTFE fine powder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takanori Kodama 5-1 Ogimachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Showa Denko KK (72) Hiroyasu Taguchi 5-1 Ogimachi, Kawasaki-ku, Kawasaki, Kanagawa Showa Denko Within the corporation

Claims (6)

[Claims] 1. A surface treatment of a molecular pump, wherein a film made of a nickel-tin alloy film co-deposited with an ethylene tetrafluoride resin in a fine powder form is formed on a contact surface of the molecular pump with a process gas. Method. 2. When the molecular pump member having the contact surface is made of stainless steel or an iron-based material, a nickel film is formed on the first layer, a nickel-phosphorus film is formed on the second layer, and a fourth layer is formed on the third layer. 2. The molecular pump according to claim 1, wherein a composite film made of a nickel-tin alloy film obtained by co-depositing a chlorinated ethylene resin in a fine powder form is formed, and a film layer made of at least these three layers is laminated. Surface treatment method. 3. When the molecular pump member having the contact surface is made of an aluminum alloy, the aluminum alloy surface portion of the molecular pump member is reformed into a zinc film, and then the second layer of nickel. The surface treatment method for a molecular pump according to claim 2, wherein a film layer made of a nickel-tin alloy film obtained by co-depositing a phosphorus film and a third layer of tetrafluoroethylene resin in the form of fine powder is laminated. . 4. The surface treatment method for a molecular pump according to claim 2, wherein the first-layer nickel film is formed by nickel strike to a thickness of 0.1 to 2 μm. 5. The surface treatment method for a molecular pump according to claim 2, wherein the second-layer nickel-phosphorus film is formed to a thickness of 1 to 20 μm by an electroless plating method. 6. The third layer of the nickel-tin alloy film co-deposited with the tetrafluoroethylene resin is formed by electroplating to a thickness of 1 to 50 μm, and fine powder of the tetrafluoroethylene resin is used. Is formed to have a particle size of 3 to 8 μm. 3. The surface treatment method for a molecular pump according to claim 1, wherein