JPH02298335A - Prevention of aluminum vacuum chamber from corrosion and contamination - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention is applicable to MBE equipment, ion blating equipment,
This invention relates to a method for preventing corrosion and contamination of aluminum vacuum chambers used in dry etching equipment, CVD equipment, etc.

In this specification, the term "aluminum" refers to
In addition to pure aluminum, aluminum alloys are included. However, the term "aluminum element" does not include aluminum alloys.

BACKGROUND OF THE INVENTION Conventionally, stainless steel vacuum chambers have been widely used in the various devices mentioned above. However, the stainless steel vacuum chamber had problems such as being heavy, having poor thermal conductivity, and having a large surface gas release coefficient, so it was considered to use an aluminum vacuum chamber.

However, aluminum vacuum chambers
GaA containing corrosive components such as gallium in equipment
When forming semiconductor films such as S, or when using etching gases for dry etching and reaction gases for CVD methods that contain corrosive components such as chlorine, there is a problem that the vacuum chamber corrodes. In addition, when forming a semiconductor film containing non-corrosive components such as silicon using an MBE device, or when forming a thin film made of non-corrosive components using an ion blating method, these non-corrosive components are deposited on the inner peripheral surface of the vacuum chamber. There was a problem that the vacuum chamber would be contaminated.

Therefore, in order to solve the problem of corrosion, vacuum chambers have been proposed in which the inner peripheral surface is subjected to various anti-corrosion surface treatments. However, with any anti-corrosion surface treatment, the cost of the treatment is high, and since none of the anti-corrosion surface treatments can completely prevent corrosion, the vacuum chamber must be replaced periodically. However, there is a problem in that the cost is high. Furthermore, regarding the problem of contamination due to the adhesion of non-corrosive components, there is currently no method to prevent this problem.

An object of the present invention is to provide a method for preventing corrosion and contamination of an aluminum vacuum chamber, which can solve the above problems all at once.

Means for Solving the Problems A method for preventing corrosion and contamination of an aluminum vacuum chamber according to the present invention includes removably disposing aluminum aluminum foil along the inner peripheral surface of an aluminum vacuum chamber. It is characterized by coating the inner circumferential surface.

In the above, the parts covered with aluminum foil are the inner circumferential surface of the vacuum chamber, excluding the connection parts of equipment necessary for processing such as dry etching.

When using an aluminum vacuum chamber, inside it,
If corrosive components such as gallium and chlorine as mentioned above are present, apply a corrosion-preventing surface treatment to at least one side of the aluminum foil, and place the aluminum foil on the inner peripheral surface of the vacuum chamber so that the corrosion-preventing surface faces inward. It is preferable to arrange it along. This eliminates the need to replace the aluminum foil every time the vacuum chamber is used. Examples of surface treatment methods for preventing corrosion include the following four methods.

(1) A method in which an anodic oxide film is formed on at least one side of an aluminum foil, and then a heat drying process is performed to evaporate and remove moisture adsorbed on the anodic oxide film.

As the anodic oxide film, an oxalic acid film is preferable in consideration of heat resistance and thermal cycleability. If the film has excellent heat resistance and thermal cycleability, the film can be prevented from cracking or peeling even if baking treatment is performed every time dry etching or the like is performed. If the film cracks or peels off, the aluminum foil will corrode. However, since the oxalic acid film is porous, the amount of moisture absorbed is greater than that of the barrier-type anodic oxide film. Therefore, in consideration of the amount of adsorbed water, a barrier type boric acid film is preferable. Alternatively, a sulfuric acid film may be used. However, in the case of an oxalic acid film, even if the amount of adsorbed water is large, there is no problem as long as the post-process heat drying treatment is performed in the warehouse. Further, the thickness of the anodic oxide film is preferably within the range of 0:5 to 20:0. The reason is that the film thickness is 0. 5/II
If it is less than II, the corrosion resistance of the film against the above-mentioned corrosive components will not be sufficient, and if it exceeds 2C17, the amount of gas released will increase when the vacuum chamber is brought into a vacuum state, and the thermal cycleability will decrease, making it difficult to bake. This is because there is a possibility that the film will be easily cracked when repeated. Also,
Heat drying treatment after forming the anodic oxide film at 100-150℃
It is preferable to carry out the test for 5 to 20 hours. If the temperature and time are below the above lower limit values, the amount of adsorbed moisture will not be reduced sufficiently, and as a result, the amount of gas released when the vacuum chamber is in a vacuum state will not be reduced, and if the above upper limit values are exceeded, the anode This is because cracks may occur in the oxide film. Further, it is desirable that this treatment be performed in a vacuum.

(2) A dispersion liquid in which ceramic particles as a dispersoid are uniformly dispersed in a dispersion medium is applied to at least one side of the aluminum foil, and then dried to adhere the ceramic particles to the surface of the aluminum foil to form a ceramic coating. How to form.

As ceramic particles, SiO□, AiJ203,
Fe20. , Cod, Cr, 0, , MnO2, MgO
, T i 02, etc., which can be uniformly dispersed in a dispersion medium, are used.

Such ceramic particles may be contained in the dispersion liquid as IPl or two or more thereof. The size of the ceramic particles is preferably within the range of 0.5 to 2 mm. If this size is less than 0°5M, gelation tends to occur, and if it exceeds 2M, pinholes are likely to occur in the formed film. As the dispersion medium, it is preferable to use water or alcohols, and among them, it is particularly preferable to use isopropyl alcohol. The reason for this is that during the drying process in the post-process, the amount of adsorption to the ceramic film that is easily evaporated and formed is reduced, and as a result, the amount of gas released from the film when the vacuum chamber is evacuated is reduced. It's getting less,
This is because there is less risk of lowering the degree of vacuum within the vacuum chamber. Moreover, the content of dispersoid in the dispersion liquid is 10 to 7
It is preferably within the range of 0wt%, and particularly preferably within the range of 30 to 60wt%.

This is because if the dispersoid content is less than 10 wt%, pinholes are likely to occur in the formed film, and if it exceeds 70 wt%, the dispersion becomes highly viscous and difficult to process. cormorant)
The dispersion is applied to the aluminum foil by a dipping method, a spraying method, or the like. The applied dispersion was dried at 150
This may be done by heating at ~200°C for 15 to 60 minutes. Then, the ceramic particles are dehydrated and condensed by this heating to form a film. Further, the thickness of the ceramic coating film to be formed is preferably within the range of 1 to 20 mm. The reason is lJ! If it is less than 20/7777, the corrosion resistance against the above-mentioned corrosive components will not be sufficient, and if it exceeds 20/7777, the amount of gas released from the film will increase when the vacuum chamber is brought into a vacuum state, and the thermal cycleability will decrease, resulting in dry etching. This is also because the film may become easily cracked when baking is repeated during the CVD method or the like.

(3) A method of forming a film with excellent corrosion resistance against the above-mentioned corrosive components on at least one side of aluminum foil by ion blating.

As a film with excellent corrosion resistance against the above corrosive components, T
iN, Tic, A/NSA/C.

Examples include AI203 and CrN. TiN5A/
A film made of N and CrN is formed by ion blating using N2 gas as a reactive gas and Ti, AI or C as an evaporated metal. A film made of TiC and AIC is It is formed by ion blasting using acetylene as a reactive gas and Ti or AI as an evaporated metal.A film made of Al2O3 is formed by using an oxygen-containing gas as a reactive gas and using Ti or AI as an evaporated metal. It is formed by performing ion blating using AI.The film thickness of such a film is preferably within the range of 1 to 20/UI.The reason is that if the film thickness is less than 1M, , the corrosion resistance of the film is not sufficient, 20/ffl
Exceeding this will increase the processing time required for ion blating, leading to higher costs, as well as reducing thermal cycle performance, which may make the film more likely to crack when baking is repeated during dry etching and CVD methods. It is from. The film thickness is controlled by controlling the processing time, flow rate and flow rate of reactive gas, vapor deposition rate, etc. during ion blating.

(4) A method of forming a coating layer made of the compound by injecting ions that react with the aluminum element into at least one side of the aluminum foil to form a compound having excellent corrosion resistance against the above-mentioned corrosive components. .

There are many ions that react with the aluminum element to form compounds having excellent corrosion resistance against the above-mentioned corrosive components, among which oxygen ions, nitrogen ions, carbon ions, etc. are used. These ions are made from easily gasified O2, N2, C, etc. The elements produced by the reaction between the above ions and the aluminum element include AN20i, 1)N1ANC, and the like. Moreover, it is preferable that the thickness of the coating layer of the compound is within the range of 0.1 to 1 mm. The reason is that if the thickness is less than 0.1p, the coating layer will not have sufficient corrosion resistance against the above-mentioned corrosive components (and the thickness cannot be made thicker than 1p by ion implantation. The thickness of the coating layer is controlled by controlling the acceleration voltage related to the implantation depth and the ion implantation current related to the implantation amount during ion implantation.
To keep it within the range of I11, set the acceleration voltage to 1, for example, 50
The ion implantation current was controlled to ~500kV and the implantation amount was 1x.
Control is performed so that l Q l 8 to lXl0'' pieces/C-.

Furthermore, if there are corrosive components inside the aluminum vacuum chamber when using it, the inner circumferential surface of the aluminum vacuum chamber should be treated using the same anti-corrosion surface treatment method applied to aluminum foil as described above. It is recommended that the surface be treated to prevent corrosion.

In the above, when the aluminum vacuum chamber is used and there are no corrosive components inside the vacuum chamber, there is no need to perform any special surface treatment on the aluminum foil. However, when the inside of the vacuum chamber is set to an ultra-high vacuum state of 10-' Torr or less, at least one side of the aluminum foil is cleaned and dried to ensure that the aluminum foil is clean and has no hydrated oxide film removed. After forming the aluminum foil into a surface, the aluminum foil is heated in an oxygen-containing gas atmosphere that does not come into contact with moisture-containing air to form a honey oxide film on at least one side of the aluminum foil. It is preferable to arrange it along the inner circumferential surface of the vacuum chamber so that it faces the inside of the vacuum chamber. Specific methods for cleaning and drying at least one side of the aluminum foil to obtain a clean and dry surface from which the hydrated oxide film has been removed include, for example, alkaline cleaning using caustic soda or acid cleaning using sulfuric acid. There is a method of washing away the machining oil and removing the hydrated oxide film formed on the surface of the aluminum material, and then drying it at low temperatures in an inert gas atmosphere, a gas atmosphere inert to aluminum, or in a vacuum. be. Drying after alkaline cleaning or acid cleaning is preferably performed in a vacuum atmosphere. This is because, after the above-mentioned cleaning, it can be placed in a vacuum oven and dried while being evacuated.

Is this dryness normal? It is preferable to carry out at a temperature range of a to 120°C, particularly 70 to 90°C. This is because if the drying temperature exceeds 120°C, a hydrated oxide film may be formed during this drying process. Furthermore, after alkaline cleaning or acid cleaning and before drying, it is preferable to immerse the aluminum foil in a treatment liquid for inhibiting the formation of a hydrated oxide film to perform a treatment for inhibiting the formation of a hydrated oxide film. As a treatment liquid for suppressing hydrated oxide film formation,
For example, chromic acid, silicic acid, vanadic acid, zirconic acid,
An aqueous solution containing phosphoric acid (polyphosphoric acid), permanganic acid, tungstic acid and molybdic acid, and one of these salts is used. The solute concentration in the treatment solution is 0.
0000001-5vt%, preferably 0.00000
It is preferably within the range of 1 to 0.0005 wt%. After cleaning and drying at least one side of the aluminum foil to obtain a clean and dry surface from which the hydrated oxide film has been removed, the aluminum foil is heated in an oxygen-containing gas atmosphere so as not to come into contact with the moisture-containing atmosphere. However, as methods for forming an oxide film on one side of the aluminum foil, there are, for example, the following three methods.

(2) A method of heating in a mixed gas atmosphere containing 0.5 to 30 vol% oxygen, particularly 1 to 1 vol% oxygen, and the remainder being an inert gas or a gas inert to aluminum. Argon and helium are common inert gases. Nitrogen gas is generally used as a gas inert to aluminum.

■Method of heating in an inert gas atmosphere or nitrogen gas atmosphere. Commercially available inert gases and nitrogen gases or industrially obtained inert gases and nitrogen gases contain trace amounts of oxygen.

■This method involves heating in a vacuum atmosphere. Even a vacuum atmosphere contains trace amounts of oxygen. “In these three methods, the heating temperature is 120 to 500℃, especially 200 to 30℃.
0°C, heating time 0.1 to 24 hours, especially 0.5 to 24 hours.
It is better to set it to 6 hours. The heat treatment at 200 to 300°C serves as an aging treatment when the aluminum foil is an aluminum alloy for heat treatment, and also serves as a stabilization treatment when the aluminum foil is an aluminum alloy for non-heat treatment.

By the way, if the heating temperature is less than 120°C, the formation of the oxide film will not be successful, and if it exceeds 500°C, part of the amorphous film will crystallize, resulting in a mixture of both, and there is a risk that a honeyed oxide film will not be formed. be. According to the above three methods, since the surface of the aluminum foil does not come into contact with the atmosphere containing moisture, a hydrated oxide film will not be generated again. Of the three methods described above, the first method yields an oxide film with a thickness of about 20 to 60 mm, and the second and third methods yield thinner oxide films. Note that in the third method, it is difficult to control the dew point, so the first and second methods are preferable.

Operation When carrying out MBE, ion blating, dry etching and CVD using a vacuum chamber, cover the inner circumferential surface of the vacuum chamber with aluminum foil.
After completing the work, remove the aluminum foil. Then, when carrying out the above operation again, the inner peripheral surface of the vacuum chamber is covered with new aluminum foil. In this way, the inner peripheral surface of the vacuum chamber can be prevented from being corroded or contaminated by the action of the aluminum foil.

Example Examples of this invention will be shown below.

5fO2 in a dispersion medium made of isopropyl alcohol on one side of aluminum foil made of JIS AlN30.
Particle size II consisting of! 1! After applying a dispersion liquid in which ceramic particles of I were uniformly dispersed (dispersoid content 60 νt%), this was heated and dried at 150°C for 30 minutes to form a ceramic film with a thickness of 15/ffi. . Next, this aluminum foil was used to cover the inner peripheral surface of a vacuum chamber for a dry etching device. Then, using this vacuum chamber, the pressure inside the vacuum chamber was increased to 10
−'Torr and CCΩ as a reactive gas.
4 was used to repeatedly perform reactive ion beam etching on the sample. The aluminum foil was replaced every time one reactive ion beam etching process was completed.

As a result, even after using the vacuum chamber for one year, no corrosion was observed on the inner peripheral surface of the vacuum chamber.

Effects of the Invention According to the method of the present invention, as described above, the inner peripheral surface of the vacuum chamber can be prevented from being corroded or stained due to the action of the aluminum foil, thereby extending the life of the vacuum chamber. This results in a significant increase in the number of vacuum chambers, and the cycle for replacing the vacuum chamber becomes extremely long. Moreover, you only need to use aluminum foil. Therefore, the cost is lower than when replacing the vacuum chamber.

that's all

Claims (1)

[Claims] A method for preventing corrosion and contamination of an aluminum vacuum chamber, which comprises removably disposing aluminum foil along the inner circumferential surface of the aluminum vacuum chamber, and covering the inner circumferential surface of the vacuum chamber with the aluminum foil.