JP2000297368A - Sputtering method and sputtering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the intrusion of sputtering gas cracked and excited by plasma and high in reactivity into the back face side of a substrate and to prevent the formation of discharge at the back face side of the substrate as well. SOLUTION: In a sputtering device in which a target 7 is sputtered in a vacuum chamber 1, and a thin film is formed onto a substrate 8 fitted to a rotating substrate holder 9, a purge chamber 17 in which the back face or bottom face of the substrate holder roles as a cover and surrounded for preventing the deposition of sputtering particles is formed, and, a purge gas introducing means 4 introducing purge gas into the purge chamber via a purge gas introducing part of the rotary shaft 12 of the substrate holder, a gas analyzing means 25 in the purge chamber and a controlling means 27 controlling the amt. of the purge gas to be introduced by the purge gas introducing means by the result of gas analysis are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering method and a sputtering apparatus for forming a thin film on a substrate attached to a rotating substrate holder by sputtering a target, and particularly to introducing a fluoride-based gas into a sputtering gas. TECHNICAL FIELD The present invention relates to a reactive sputtering method and a reactive sputtering apparatus for forming an optical thin film by performing the method.

[0002]

2. Description of the Related Art Parallel plate type magnetron sputtering, which has been widely used in the past, is a method in which a target to be a thin film material and a substrate attached to a substrate holder are arranged in a vacuum chamber so as to face each other. By generating a plasma and sputtering a target, and depositing sputter particles hit by the sputter on a substrate,
An apparatus for forming a thin film on a substrate, which is simpler than other methods, and has features such as excellent high-speed film formation, large-area film formation, and excellent target life.

In such a sputtering apparatus, recently, in the field of optical films, aluminum fluoride (Al) which is a low refractive index material is used.
F ₃ ) and fluoride sputtering of magnesium fluoride (MgF ₂ ) have been studied.

However, nitrogen fluoride NF ₃ and fluorine
(F ₂ ) When a reactive gas such as a gas is introduced to form a film of a fluoride material on a lens or the like, a plasma discharge formed between a target and a vacuum chamber or a space between a substrate holder and a substrate is circulated. The reactive gas is excited or decomposed by plasma discharge to become a highly reactive gas, and the back surface of the lens substrate attached to the substrate holder is etched and roughened, or when forming a multilayer film on both surfaces of the lens substrate In addition, when a multilayer film is formed on the back surface side by reversing the surface on which the film formation is completed at the beginning, there is a problem that the film of the final layer formed at the beginning is etched and optical characteristics are changed.

Although slightly different from the above problem, the following solutions have been conventionally proposed to prevent the sputtered particles from reaching the back surface of the substrate. 1) The back surface of the substrate is brought into contact with the surface of the substrate holder to prevent sneaking around. 2) A method of introducing a purge gas into the gap between the back surface of the substrate and the substrate holder. In particular, Japanese Patent Application Laid-Open No. Hei 6-120145 discloses a film forming apparatus and the like characterized in that a purge gas is caused to flow in the outer peripheral direction of a substrate support and a direction control mechanism for controlling the direction so that the purge gas does not flow on the substrate is provided. Has been proposed.

[0006] These solutions, however, involve fluorides.
Fluoride NF in material sputtering _ThreeAnd F_TwoReaction of gas etc.
Introduce a very high sputter gas into the lens
Solving the problems caused by the deposition of nitride materials
I couldn't. In 1), since the base is a lens, the substrate holder
Contact between the lens and the effective beam diameter area will cause scratches on the lens surface.
I can't do that. In 2), a small gap between the back of the base and the substrate holder
A method of introducing a purge gas into the lens
This cannot be done because the surface is damaged. Furthermore, the substrate is a lens
It is necessary to correspond to various lens shapes
Therefore, sufficient space is required on the back side of the film deposition surface.
You.

Japanese Patent Application Laid-Open No. 6-120145 discloses a structure in which a purge gas is caused to flow in the outer peripheral direction of a substrate support table and a structure in which a gas direction control mechanism is provided on a film forming surface of a substrate so that the purge gas does not flow onto a substrate plate. This has a great effect on a highly dependent CVD apparatus in which the flow of the source gas greatly affects the film characteristics.

[0008]

As described above, the prior art could not sufficiently solve the problem caused when a fluoride material was formed on a lens substrate.

An object of the present invention is to prevent a raw material gas, a highly reactive gas in which the raw material gas is excited or decomposed, and a plasma discharge from flowing into a sufficient space on the back surface of the lens substrate.

[0010] An object of the present invention is to overcome the drawbacks of the prior art described above, and in sputtering for forming an optical thin film or the like on both surfaces of a substrate, highly reactive sputtering gas decomposed and excited by plasma is directed to the back surface of the substrate. An object of the present invention is to provide a sputtering method and apparatus capable of preventing penetration of the substrate and preventing formation of a discharge on the rear surface of the substrate, thereby preventing etching of the rear surface of the substrate and obtaining a good-quality thin film on both surfaces of the substrate. .

[0011]

In order to achieve the above object, a sputtering apparatus according to the present invention sputters a target in a vacuum chamber and forms a thin film on a substrate attached to a rotating substrate holder. In the sputtering apparatus, the back surface or the bottom surface of the substrate holder serves as a lid, a purge chamber surrounded for the purpose of preventing deposition of sputter particles is formed, and a purge gas introduction unit of a rotation axis of the substrate holder is provided in the purge chamber. A purge gas introduction unit for introducing a purge gas through the purge chamber, a gas analysis unit in the purge chamber, and a control unit for controlling a purge gas introduction amount by the purge gas introduction unit based on a gas analysis result.

Further, the sputtering apparatus is characterized in that a purge gas is introduced through a porous alumina plate between the purge introduction section of the rotation shaft of the substrate holder and the purge chamber of the space.

As a sputtering method, a purge chamber surrounded for the purpose of preventing sputter particles is provided in a vacuum chamber in which the back or bottom surface of a substrate holder functions as a lid, and a target is sputtered and rotated. A sputtering method for forming a thin film on a substrate attached to a substrate holder to be performed, comprising: introducing a purge gas, which is a helium gas, into the purge chamber, and then introducing a sputter gas, a fluoride-based gas, into the vacuum chamber. And sputtering.

According to the present invention, it is an object of the present invention to prevent sputtered particles whose back surface serves as a lid during sputtering for forming a thin film on a substrate attached to a rotating substrate holder. A closed purge chamber,
By introducing the purge gas into the purge chamber through the rotation shaft of the substrate holder, sputter particles formed by sputtering, which are likely to enter the purge chamber, and sputter gas having high reactivity that is decomposed and excited are suppressed.

Accordingly, in the formation of a fluoride sputtered film having a higher reactivity than in the prior art, it is possible to reduce the damage on the backside of the substrate by performing a structure and a sputtering method for minimizing the penetration of the reactive gas into the backside of the substrate. And a high-quality fluoride film can be obtained.

[0016]

Embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 is a sectional view of a sputtering apparatus according to a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a vacuum chamber, 2 denotes an exhaust system including a vacuum pump for exhausting the chamber 1, and the like.
3 is a sputtering gas introduction system, and 4 is a purge gas introduction system. As shown in the drawing, a target holder 6 fixed to the chamber 1 via an insulating member 5 is provided in the vacuum chamber 1, and a target 7 is provided in the holder 6. On the opposite side of the target 7, a substrate holder 9 for holding a substrate 8 on which a thin film is formed is provided. The substrate holder 9 is connected to a clamp drive system 15 via a clamp arm 10, a clamp drive shaft 11, a substrate rotation shaft 12, and magnet couplings 13 and 14.

The substrate holder 9 to which the substrate 8 is attached has a transport system for transporting and reversing the substrate holder because it is necessary to replace the substrate and change the film formation surface. The substrate holder that has been conveyed or turned over is clamped so that the substrate holder covers the space surrounded by the deposition-preventing plate 16 for the purpose of preventing deposition of sputtered particles on the back surface of the substrate, thereby forming a purge chamber 17. Is done. A gap of 2 to 3 mm is provided between the deposition-preventing plate and the substrate holder to suppress generation of dust due to contact. In this state, the plasma formed between the cathode and the ground excites and decomposes the fluorine-based sputtering gas from this gap to form a highly reactive gas that is excited and decomposed. The back surface of the substrate will be damaged by etching or the like.

In this embodiment, in order to prevent invasion of highly reactive gas from the gap between the deposition-preventing plate and the substrate holder,
This can be achieved by introducing a purge gas such that the pressure in the purge chamber becomes higher than the sputtering pressure.

Therefore, a porous plate 18 made of alumina is attached to the inside of the purge chamber. As the size of the substrate increases, the space inside the purge chamber increases, and turbulence and stagnation occur when the purge gas is introduced from a single location. In order to eliminate the turbulence and stagnation, an alumina having substantially the same size as the substrate holder and having corrosion resistance to fluorine-based gas is provided between the purge inlet of the rotating shaft in the purge chamber and the substrate holder 9 to which the substrate 8 is attached. By forming a flow by introducing a purge gas through the porous plate 18, turbulence and stagnation can be reduced, and the purge chamber space having a large volume can be quickly turned into a purge atmosphere.

The purge gas introduced from the purge gas introduction system 4 is introduced into the substrate rotating shaft 12 via the rotating shaft coupling 20 through a pipe. The purge gas introduced into the inside of the substrate rotating shaft is supplied to the back space of the porous alumina plate 18 through the through hole 21 of the clamp drive shaft 11.
Further, it is uniformly supplied into the purge chamber through the entire surface of the porous plate. The gas supplied to the purge chamber flows through the gap between the substrate holder 9 and the deposition-preventing plate 16 and from the inside of the chamber 1 to the exhaust system
Exhausted through

A suction pipe 19 for sampling gas in the purge chamber is provided in the purge chamber, and the suction pipe penetrates the porous alumina plate 18 and is connected to the clamp drive shaft 11. The sampling gas in the purge chamber passes through the suction pipe 19 and passes through the clamp drive shaft 11.
It is introduced into the space between the clamp drive shaft 11 and the substrate rotating shaft 12 through a second through hole 22 provided therein, and further passes through a sampling gas suction hole 23 and a rotating shaft magnetic seal 24 provided on the rotating shaft. The gas is supplied to the gas analysis tube 25.
The gas analysis tube has a differential exhaust system 2 for exhausting the inside of the analysis tube.
6 are connected.

The reaction gas data signal detected by the gas analysis tube is sent to the process control circuit 27, and the control signal is sent to the purge gas supply system 4 so that the gas having the set mass becomes equal to or less than the set value, and can be controlled. It has become.

The operation of the sputtering apparatus according to the first embodiment will be described.

Actually, aluminum fluoride is formed by the following process. Spare room not shown (load lock room)
The substrate holder 9 holding the substrate 8 that has been sufficiently evacuated is transferred into the chamber 1 by the holder transfer system, and is clamped and held by the clamp arm 10. After the clamping, the rotation is transmitted from the rotation drive system 28 to the substrate rotation shaft 12 via the gear, and the rotation of the substrate is started. Next, He gas is supplied at a constant rate of 300 sccm into the purge chamber from the purge gas introduction system 4.

After the He gas has been sufficiently supplied into the purge chamber, a NF3 gas, which is a sputtering reaction gas, is uniformly supplied to the vicinity of the Al target 7 at 50 sccm. After supplying the sputtering gas, sampling of the gas in the purge chamber is started. Sampling gas is sucked in and gas analysis is performed using a Q mass or a sputter process monitor. Since the mass of the fragmentation coefficient of the nitrogen trifluoride NF3, which is the sputtering reaction gas, is 52, the mass signal of this mass is detected and fed back to the mass flow controller of the purge gas supply system so that the mass becomes smaller than the set value. multiply.

Atmosphere gas near the gap between the deposition-preventing plate and the substrate holder is sampled and measured using an analysis means such as a sputter process monitor, and feedback control is performed on the flow rate of the purge gas. For example, in the case of using a sputter process monitor, in order to increase the detection sensitivity, the mass of the fragmentation coefficient of the sputtering reaction gas is large (for example, in the case of argon gas (Ar), the fragmentation coefficient of mass 40 is 0.88, and the mass is 40). It is more preferable to select the fragmentation coefficient of 20 as 0.12) and measure the amount of invading gas. By feeding back to the purge gas flow rate controller so that the measured value becomes equal to or less than the set value, the amount of reactant gas entering the purge chamber can be suppressed even when the sputtering process conditions are changed.

Simultaneously with the control operation, a 1 KW electric power is supplied from the sputtering power supply 29 to the target 7 to generate plasma discharge. After the discharge is stabilized, a shutter plate (shown in FIG. Open) to start film formation. During the film formation, the He gas that has passed through the minute holes of the porous plate 18 is supplied to the back surface of the substrate holder and the inside of the purge chamber. The supplied purge gas He is applied to the deposition preventing plate 1.
The sputter reactant gas flows into the discharge space through the gap between the substrate holder 6 and the substrate holder 9 so that the sputter reaction gas activated in the discharge space cannot enter the purge chamber 17 on the back surface of the substrate holder.

Further, a projection having a diameter slightly smaller than that of the deposition prevention plate on the outer periphery of the purge chamber is formed on the surface of the substrate holder so that the sputter reaction gas activated in the discharge space cannot enter the purge chamber 17 on the back of the substrate holder. (Shown) can increase the conductance, and the effect of preventing invasion gas is enhanced, which is more preferable.

On the other hand, when the inert gas argon Ar was used as the purge gas in the same process as described above, the effect of the purge gas was equivalent to that of helium He. It was confirmed that a thin discharge occurred. Further, when the purge gas of argon flows into the discharge space, the fluctuation of the flow rate of the purge gas has a great influence on the film quality and the film formation rate. Further, it was found that the energy incident on the substrate was increased due to the heavy mass of the argon gas, and the fluoride film during the film formation was damaged, resulting in a film having a large absorption.

Accordingly, the purge gas is an inert gas such as He gas, which has a high ionization energy and does not cause a discharge in the purge chamber, and has a modest value which does not cause damage to the film when flowing into the discharge space. He gas, which assists the fluoride film with energy, is optimal.

After the specified amount of film is formed, the rotation of the sputtering power supply 29, the sputtering gas and the substrate is stopped. After closing the shutter and exhausting the sputter reaction gas sufficiently,
Stop the purge gas.

Next, in order to form a film on the back surface, the holder 9 is transported from the inside of the chamber to the preliminary chamber by the holder transport system from the preliminary chamber (load lock chamber). The holder is turned upside down in the preparatory room, and is again transferred into the chamber by the holder transfer system. Then, a film is formed on the back surface of the substrate by performing the same operation as above, and the film formation is completed.

On the other hand, in the sputtering method according to the present invention, as described above, the space in the purge chamber increases as the size of the substrate increases. Particularly, in the high-frequency sputtering using a high frequency of 13.56 MHz, the sputtering chamber depends on the conditions. A discharge may be formed. As a countermeasure, discharge can be prevented by using a gas having higher ionization energy than the sputtering gas as the purge gas. For example, when argon (Ar), oxygen (O), nitrogen (N), and fluorine (F) are introduced into the sputtering gas, the ionization energies are 15.8 eV and 13.6, respectively.
By introducing a helium (He) gas of 24.6 eV, which has an ionization energy higher than that of the sputtering gas at eV, 14.5 eV, and 17.4 eV, discharge formation in the purge chamber can be prevented. Preventing this discharge suppresses plasma damage, impurity contamination, and substrate temperature rise due to discharge on the back surface, desorption of adsorbed gas adsorbed on the surface of the substrate holder and the inside of the purge chamber, and activation of the desorbed gas. Is to suppress the conversion. Further, at the time of introducing the sputtering gas, after introducing the purge gas, in order to prevent contamination by the sputtering gas in the purge chamber,
A good sputtering method is to introduce a sputtering gas and perform sputtering.

(Second Embodiment) The present embodiment is also applicable to a so-called carousel type sputtering apparatus in which a substrate holder has a substantially cylindrical shape and can form a film on many substrates simultaneously.

FIG. 2 is a sectional view of a carousel type sputtering apparatus according to a second embodiment of the present invention.

As shown in FIG. 2, the carousel type sputtering apparatus of this embodiment has a substantially cylindrical substrate holder 9 rotating in a circumferential direction inside a film forming chamber chamber 1 and a substrate holder 9 facing the substrate holder. (Rectangular) target holder 6 and target 7 connected to a high frequency power supply or DC power supply 29 disposed between the substrate holder 9 and the rectangular (rectangular) target 7 having the same rotation center axis as the substrate holder 9. A film forming chamber is constituted by a cylindrical shutter 30 having an opened opening, a sputtering gas introducing system 3 such as fluorine, and an exhaust system 2, and a load lock chamber exhaust system 31 and a substrate A front chamber (load lock chamber) 33 having a transport system 32 is provided.

A gate valve 3 through which a substantially cylindrical substrate holder can pass is provided between the film forming chamber and the load lock chamber 33.
4 is provided.

Inside the substantially cylindrical substrate holder 9 (purge chamber)
Is a purge gas inlet pipe 35 formed of porous alumina.
The purge gas introduced from the purge gas introduction system 4 is introduced into the purge gas introduction pipe 35 in the substrate rotating shaft through the rotating shaft coupling 20 through the piping, and is uniformly introduced into the substantially cylindrical substrate holder 9. be introduced. A suction pipe 19 for sampling the gas in the purge chamber is provided inside the substantially cylindrical substrate holder 9 (purge chamber), and the suction pipe 19 is connected to the substrate rotation shaft. The sampling gas passes through the inside of the suction pipe, passes through the hole provided inside the substrate rotation shaft, and is supplied to the gas analysis tube 25 through the sampling gas suction hole 23 provided on the rotation shaft and the rotation shaft magnetic seal 24. . The gas analysis tube 25 is connected to a differential exhaust system 26 for exhausting the inside of the analysis tube.

The reaction gas data signal detected by the gas analysis tube 25 is sent to the process control circuit 27 and the purge gas introduction system 4 is operated so that the gas having the set mass becomes equal to or less than the set value.
A control signal is sent to the controller to control it.

When a thin film is formed on a substrate by using such a carousel type sputtering apparatus, first, the substrates 8 are fixed on a plurality of substrate supporting surfaces of the substrate holder 9 and then the upper part of the film forming chamber is formed. Exhaust is performed in the load lock chamber 33 (the inside of the substrate holder 9 is exhausted through an alignment hole on the cylindrical bottom). After the evacuation is sufficiently completed, the gate valve 34 provided between the front chamber and the film forming chamber is opened, and the substrate holder 9 is moved by the substrate transport system 32 to the substrate rotating table 36 in the film forming chamber.
Put on. The surface of the substrate rotating table that contacts the substrate holder is tapered so that the substrate holder can be positioned.

With the substrate holder 9 placed on the rotary table 36, the substrate holder 9 is rotated by the driving force of the rotary drive unit 28, and a set amount of He purge gas is introduced into the substrate holder.

Next, with the shutter 30 closed, He
After the gas is sufficiently supplied to the inside of the substrate holder (inside of the purge chamber 17), NF3 gas, which is a sputtering reaction gas, is uniformly supplied to the Al target 7 in the vicinity of 50 sccm. After supplying the sputtering gas, the sampling, measurement, and control of the gas in the purge chamber 17 are started as in the first embodiment.
At the same time as the control operation, the sputtering power supply 2
Then, a power of 1 KW is supplied from 9 to start plasma discharge and perform pre-sputtering. After that, when the discharge is stabilized, the shutter plate 3 installed between the target 7 and the substrate holder 9 is used.
Open 0 to start film formation. During the film formation, the He gas that has passed through the minute holes of the porous purge gas introduction pipe 35 is provided inside the back side purge chamber 17 of the substrate holder 9. The supplied gas flows into the discharge space through gaps (not shown) of the substrate holder 9 fixed on the plurality of substrate support surfaces. At this time, it is preferable that the gap between the substrate holders 9 is sufficiently small because the effect of preventing the reaction gas from entering the inside of the substrate holder is high.

After a lapse of a predetermined time, the shutter 30 is closed again, the sputter reaction gas system 3 and the sputter power supply 29 are stopped, and after the sputter reaction gas is sufficiently exhausted, the purge gas is stopped to terminate the film formation.

As is apparent from the above description, the sputtering apparatus according to the present invention has a structure and a sputtering apparatus for minimizing the penetration of the reaction gas to the back side in forming a fluoride sputtered film having a higher reactivity than the conventional one. By performing the method, damage on the back surface side can be reduced, and a high-quality fluoride film can be obtained.

[0047]

As described above, the present invention has the following effects. 1) In a sputtering apparatus for forming a thin film on a substrate attached to a rotating substrate holder, a purge chamber is provided in an enclosed space in which the back surface of the substrate holder serves as a lid for preventing sputter particles from depositing. The sputtering gas is introduced into the space by introducing a purge gas into the space through the rotation axis of the substrate holder. It has become possible to reduce the damage on the back side. 2) By introducing helium (He) gas as a purge gas, discharge formation in the purge chamber can be prevented. Preventing this discharge suppresses plasma damage, impurity contamination, and substrate temperature rise due to discharge on the back surface, desorption of adsorbed gas adsorbed on the surface of the substrate holder and the inside of the purge chamber, and activation of the desorbed gas. And the damage on the rear surface side of the substrate can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a sputtering apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a carousel type sputtering apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Exhaust system 3 Sputter gas introduction system 4 Purge gas introduction system 5 Insulating member 6 Target holder 7 Target 8 Substrate 9 Substrate holder 10 Clamp arm 11 Clamp drive shaft 12 Substrate rotation shaft 13, 14 Magnet coupling 15 Clamp drive system 16 Deposition plate 17 Purge chamber 18 Alumina porous plate 19 Suction pipe 20 Rotary shaft coupling 21, 22 Through hole 23 Sampling gas suction hole 24 Rotary shaft magnetic seal 25 Gas analysis tube 26 Differential exhaust system 27 Process control circuit 28 Rotary drive System 29 Sputtering power supply 30 Cylindrical shutter 31 Load lock chamber exhaust system 32 Substrate transfer system 33 Front chamber (load lock chamber) 34 Gate valve 35 Purge gas introduction pipe 36 Substrate rotation table

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasuyuki Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Ryuji Bilo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Hidehiro Kanazawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. F-term (reference) 2K009 CC06 DD04 4K029 BA42 BC08 CA06 DA04 DA09 JA02

Claims (6)

[Claims] 1. A vacuum chamber, in which a back or bottom surface of a substrate holder functions as a lid, is provided with a purge chamber surrounded for the purpose of preventing sputtered particles, and a target is sputtered and attached to a rotating substrate holder. A sputtering method for forming a thin film on a substrate obtained by introducing a purge gas that is a helium gas into the purge chamber, and then introducing a sputtering gas that is a fluoride-based gas into the vacuum chamber and performing sputtering. Characteristic sputtering method. 2. A sputtering apparatus for sputtering a target in a vacuum chamber to form a thin film on a substrate attached to a rotating substrate holder, wherein a back surface or a bottom surface of the substrate holder serves as a lid. A purge chamber surrounded for the purpose of preventing deposition of sputter particles is formed, a purge gas introduction unit that introduces a purge gas into the purge chamber via a purge gas introduction unit of a rotation shaft of the substrate holder, a gas analysis unit in the purge chamber, A sputtering apparatus comprising a control means for controlling an amount of purge gas introduced by said purge gas introduction means based on a gas analysis result. 3. The sputtering apparatus according to claim 2, wherein a purge gas is introduced through a porous plate between the purge gas introduction section of the rotation shaft of the substrate holder and the purge chamber. 4. The sputtering apparatus according to claim 2, wherein a purge gas is introduced from a purge gas introduction portion of a rotating shaft of the substrate holder into the purge chamber through a porous purge gas introduction pipe. 5. The purge gas introduced into the purge chamber,
The sputtering apparatus according to claim 2, wherein the sputtering apparatus flows out toward the vacuum chamber. 6. The sputtering apparatus according to claim 3, wherein the material of the porous plate or the purge gas introduction pipe is alumina.