JP2024006589A - Electrode plate and electrode structure for plasma processing equipment - Google Patents

Abstract

To provide a plasma treatment apparatus electrode plate capable of improving the function of a plasma treatment apparatus.SOLUTION: An electrode plate 3 arranged on the side of the electrode contact surface of a cold plate 14 includes a downstream gas passage 11 communicating with an upstream gas passage 15 penetrating from one surface of the cold plate 14 to the electrode contact surface. A corrosion resistant film 210 to process gas flowing through the upstream gas passage 15 of the cold plate 14 is formed on the side of a first surface 31 having an entrance 111 of the downstream gas passage 11 and contacting the cold plate 14. Even when the process gas enters and stays in a gap between the electrode plate 3 and the cold plate 14, the electrode plate 3 can be prevented from corroding with the process gas; the corrosion resistant film 210 is preferably any of a fluoride film, a C containing film and a noble metal film; and the thickness of the corrosion resistant film 210 is preferably 30 nm or more and 5000 nm or less.SELECTED DRAWING: Figure 2

Description

The present invention relates to an electrode plate for a plasma processing apparatus and an electrode structure for the plasma processing apparatus.

In plasma processing equipment such as plasma etching equipment and plasma CVD equipment used in semiconductor device manufacturing processes, an upper electrode and a lower electrode connected to a high-frequency power source are arranged vertically facing each other in a chamber, and the upper electrode is placed above the lower electrode. Plasma is generated by applying a high frequency voltage between both electrodes while flowing a process gas for plasma generation toward the substrate to be processed through a through hole formed in the upper electrode. , it is configured to perform processing such as etching on the substrate to be processed.

Conventionally, in plasma processing apparatuses, anti-corrosion treatment has been applied to the surfaces of members constituting the apparatus in order to suppress corrosion of the members due to process gas.
In Patent Document 1, with an upper electrode, a lower electrode, etc. arranged inside a chamber of a plasma processing apparatus, a protective film forming gas is introduced into the chamber from a process gas inlet, and the protective film forming gas is A protective film is formed at a location where the process gas is brought out of the chamber through the exhaust port and comes into contact with the process gas within the chamber of the plasma processing apparatus.
In Patent Document 2, a sprayed film is formed in a plasma processing apparatus at a location that is exposed to a processing gas.

International Publication No. 2006/137541 Japanese Patent Application Publication No. 2006-265619

According to the method for forming a protective film disclosed in Patent Document 1, a protective film is formed on the upper electrode plate by introducing a protective film forming gas into a chamber. For example, when this method of forming a protective film is applied to a plasma etching apparatus assembled by stacking an aluminum cooling plate on an upper electrode plate, the protective film can be formed by introducing a protective film forming gas into the chamber. Although particles may be formed on the upper electrode plate and the cooling plate, there is a possibility that more particles will be generated.

In addition, in the method for forming a thermal sprayed film in Patent Document 2, it is necessary to roughen the surface of the base material in order to improve adhesion to the base material before forming the sprayed film. When surface roughening is performed, cracks are formed on the surface of the base material, which causes generation of particles in the plasma processing apparatus, which is not preferable.

Therefore, the present invention was created to solve the above problems, and provides an electrode plate for a plasma processing device and an electrode structure for the plasma processing device, which improve the functions of the plasma processing device. The purpose is to

The present invention provides an electrode plate provided with a downstream gas flow path that is disposed on the electrode contact surface side of a cooling plate and communicates with an upstream gas flow path that penetrates from one surface of the cooling plate to the electrode contact surface, A corrosion-resistant film against process gas flowing through the upstream gas flow path of the cooling plate is formed on a first surface side that provides an inlet of the downstream gas flow path and contacts the cooling plate.

The electrode plate of the present invention has the first surface and a second surface located opposite to the first surface. Formed on the side. Here, "formed on the first surface side" refers to cases where the corrosion-resistant film is formed directly on the first surface of the electrode plate, and cases where the corrosion-resistant film is formed between the first surface of the electrode plate and the case where the corrosion-resistant film is formed directly on the first surface of the electrode plate. This includes the case where it is formed on the first surface with a base film interposed therebetween.
In the electrode plate of the present invention, preferably, the corrosion-resistant film is any one of a fluoride film, a C-containing film, and a noble metal film. The fluoride film contains any one of the following elements: Al, Zr, Zn, Mg, Ce, Ag, Y, Fe, Cu, Cr, and Ni, and the C-containing film consists only of C or C and The noble metal film contains an Ag alloy.

In the electrode plate of the present invention, preferably, the corrosion-resistant film has a thickness of 30 nm or more and 5000 nm or less.
If the film thickness is thinner than 30 nm, the corrosion-resistant film will contain many defects such as pinholes, and there is a risk that those parts will corrode and flake off, becoming particles, so it is desirable that the film thickness is 30 nm or more. . If the film thickness is thicker than 5000 nm, the film stress may increase and the corrosion-resistant film may peel off over a wide range, so it is desirable that the film thickness is 5000 nm or less.

The electrode plate of the present invention preferably has a base film between the first surface and the corrosion-resistant film.
When a base film is provided, the adhesion between the corrosion-resistant film and the electrode plate is improved. Furthermore, it is possible to prevent the corrosion-resistant film components from diffusing into the electrode plate and contaminating the substrate to be processed.

In the electrode plate of the present invention, preferably, the corrosion-resistant film is heat-treated.
When heat-treated, the corrosion-resistant film becomes denser and its adhesion to the electrode plate becomes stronger, thereby improving corrosion resistance.

The electrode structure for a plasma processing apparatus of the present invention includes the electrode plate for the plasma processing apparatus, and the cooling member having an electrode contact surface that is provided with an outlet of the upstream gas flow path and contacts the first surface of the electrode plate. It is equipped with a board and.
In the electrode structure for a plasma processing apparatus of the present invention, preferably, the corrosion-resistant film is also formed on the electrode contact surface of the cooling plate.

According to the present invention, even if the process gas enters the gap between the electrode plate and the cooling plate and stagnates therein, it is possible to prevent the electrode plate from being corroded by the process gas. This makes it possible to reduce the generation of particles caused by corrosion products peeling off or falling off the electrode plate.

FIG. 1 is a diagram showing an etching apparatus according to a first embodiment of the present invention. (a) is a diagram showing a part of the electrode structure of the etching apparatus of FIG. 1, (b) is a diagram showing part of the cooling plate of (a), and (c) is a diagram of the electrode plate of (a). FIG. It is a figure which shows the modification of the electrode structure of FIG.2(c). (a) is a diagram showing a part of the electrode structure of an etching apparatus according to a second embodiment of the present invention, (b) is a diagram showing a part of the cooling plate of (a), and (c) is a diagram showing a part of the cooling plate of (a). It is a figure which shows a part of electrode plate of (a). It is a figure for explaining the procedure of the first test of an example. (a) is X-ray Photoelectron Spectrometry (hereinafter referred to as XPS) data of Example 6 (C film), (b) is XPS data of Example 10 (SiC film), (c ) is a diagram showing XPS data of Comparative Example 1 (Al ₂ O ₃ film). (a) is a diagram showing X-ray diffraction (XRD) data of Example 6 (C film), and (b) is a diagram showing XRD data of Example 10 (SiC film). . (a) is a diagram showing XRD data of Example 1 (MgF ₂ film), and (b) is a diagram showing XRD data of Example 2 (YF ₃ film). It is a figure for explaining the procedure of the second test of an example.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
As shown in FIG. 1, the plasma etching apparatus 1 according to the first embodiment of the present invention is provided with an electrode plate 3 serving as an upper electrode in the upper part of a vacuum chamber 2, and upper and lower electrodes serving as lower electrodes in the lower part. A movable pedestal 4 is provided parallel to and spaced apart from the electrode plate 3.

The upper electrode plate 3 is insulated and supported by an insulator 5 against the wall of the vacuum chamber 2, and on the pedestal 4 is an electrostatic chuck 6 and a support ring made of silicon surrounding it. A wafer (substrate to be processed) 8 is placed on the electrostatic chuck 6 with its peripheral edge supported by a support ring 7 . Further, an etching gas supply pipe 9 is provided in the upper part of the vacuum chamber 2, and the etching gas sent from the etching gas supply pipe 9 is diffused by a diffusion member 10, and then passed through an upstream gas flow provided on a cooling plate 14. The gas flows through the passage 15 and the downstream gas flow passage 11 provided in the electrode plate 3, and is directed toward the wafer 8 and is discharged to the outside through the outlet 12 on the side of the vacuum chamber 2.

This plasma etching apparatus 1 is provided with a high frequency power source 13 that applies a high frequency voltage between the electrode plate 3 and the pedestal 4. Etching gas is emitted into the space S between the electrode plate 3 and the pedestal 4, and when a high frequency voltage is applied from the high frequency power supply 13, it turns into plasma in the space S and hits the wafer 8. The surface of the wafer 8 is etched by sputtering, that is, a physical reaction by this plasma and a chemical reaction by the etching gas.
In addition, in order to uniformly etch the wafer 8, the generated plasma is concentrated in the center of the wafer 8 and prevented from spreading to the outer periphery, thereby creating a uniform plasma between the electrode plate 3 and the wafer 8. In order to generate plasma, the plasma generation region 16 is usually surrounded by a shield link 17 made of silicon.

In the plasma etching apparatus 1, as shown in FIG. 2(a), an electrode structure 20 is composed of an electrode plate 3 and a cooling plate 14 that is in close contact with the electrode plate 3 and cools the heat of the electrode plate 3. The electrode plate 3 and the cooling plate 14 of the electrode structure 20 are provided separably, and the cooling plate 14 is shown in FIG. 2(b), and the electrode plate 3 is shown in FIG. 2(c).

(Electrode plate 3)
The electrode plate 3 of the electrode structure 20 is formed into a disk shape of single crystal silicon, columnar silicon, or polycrystalline silicon.
Further, a cooling plate 14 is fixed to the first surface 31, which is the upper surface of the electrode plate 3. The first surface 31 of the electrode plate 3 is mirror-treated to improve adhesion and bonding with the cooling plate 14. The second surface 32 of the electrode plate 3, which serves as the plasma emission surface, is also mirror-finished to prevent abnormal discharge. The degree of these mirror surfaces is, for example, approximately 0.001 μm in center line average roughness Ra, but it is sufficient if Ra is substantially 0.3 μm or less.
As shown in FIG. 2(c), the electrode plate 3 has an inlet 111 for the downstream gas flow path 11 on the first surface 31 and a downstream gas flow path on the second surface 32 located opposite to the first surface 31. A downstream gas flow path 11 passes through the electrode plate 3 with eleven outlets 112 provided. A plurality of downstream gas channels 11 are formed in the electrode plate 3 .

(Cooling plate 14)
The cooling plate 14 of the electrode structure 20 is made of aluminum or the like having excellent thermal conductivity, and one surface 141 faces the diffusion member 10 and the other surface (hereinafter referred to as the electrode contact surface) 142 faces the third surface of the electrode plate 3. Closely adheres to one side 31.
As shown in FIG. 2(b), the cooling plate 14 has an inlet 151 of the upstream gas flow path 15 on the surface 141 and an outlet 152 of the upstream gas flow path 15 on the electrode contact surface 142, so that the upstream gas flow path 15 passes through the cooling plate 14. A plurality of upstream gas flow paths 15 are formed in the cooling plate 14 . In this way, the electrode plate 3 is arranged on the electrode contact surface side of the cooling plate 14, and the downstream gas flow path 11 communicates with the upstream gas flow path 15 penetrating from one surface 141 of the cooling plate 14 to the electrode contact surface 142. and a corrosion-resistant film 210, which will be described later.

(corrosion resistant film)
The corrosion-resistant film 210 is formed on the first surface 31 of the electrode plate 3, and is not formed on the second surface 32. The corrosion-resistant film 210 is a protective film that protects the electrode plate 3 from corrosion caused by process gas, and is formed as a fluoride film, a C-containing film, or a noble metal film. The fluoride film is preferably a film containing any of the elements Al, Zr, Zn, Mg, Ce, Ag, Y, Fe, Cu, Cr, and Ni, and the C-containing film is preferably a film consisting only of C, or A film containing C and Si is preferred, and the noble metal film is preferably a film made of an Ag alloy. Furthermore, the corrosion-resistant film 210 is preferably formed as an amorphous film. Furthermore, the corrosion-resistant film 210 is preferably a highly hard film with a dense structure. The thickness of the corrosion-resistant film 210 is preferably 30 nm or more and 5000 nm or less. The corrosion-resistant film 210 preferably has a defect density such as pinholes and cracks of 1.24 pieces/mm ² or less. Here, the defect density is the number of defects such as pinholes and cracks existing in a certain area (square millimeter), and is the average value of the number of defects at multiple locations.

The corrosion-resistant film 210 may be formed on the first surface 31 of the electrode plate 3 via the base film 220, as shown in FIG. As the base film 220, a film containing Si and/or C can be used, and the base film 220 is configured as a single layer film or a multilayer structure. By providing the base film 220, the adhesion between the corrosion-resistant film 210 and the first surface 31 of the electrode plate 3 is improved.

In the electrode structure 20, the corrosion-resistant film 210 of the electrode plate 3 is in close contact with the electrode contact surface 142 of the cooling plate 14.

(Method for manufacturing electrode plate)
The method for manufacturing an electrode plate includes an electrode plate forming step of forming the electrode plate 3, and a film forming step of forming a corrosion-resistant film 210 on the cooling surface of the electrode plate.
In the electrode plate forming step, a through hole (downstream gas flow path 11) is formed in the Si substrate using a drill, and burrs around the through hole on both sides of the Si substrate are removed by an etching process. After removing the burr, both sides of the Si substrate are polished.
In the film forming step, the corrosion-resistant film 210 is formed on the first surface 31 (cooling surface) of the electrode plate 3 by sputtering or vacuum deposition. In addition, in the film forming process, film formation can be performed while heating the electrode plate 3, so that the corrosion-resistant film 210 can be formed as a heat-treated film. After the film forming step, the electrode plate 3 with the film formed on the first surface 31 may be heated. By the heat treatment, the corrosion-resistant film 210 becomes denser and its adhesion to the first surface 31 of the electrode plate 3 becomes stronger.

According to the electrode structure 20 of the plasma etching apparatus 1, even if process gas enters and stagnates between the electrode plate 3 and the cooling plate 14, the first surface 31 of the electrode plate 3 is covered with the corrosion-resistant film 210. By doing so, corrosion of the first surface 31 of the electrode plate 3 can be prevented and generation of particles can be reduced.

When the first surface 31 of the electrode plate 3 is not covered with the anti-corrosion film 210, when the process gas used in the plasma etching apparatus 1 enters between the electrode plate 3 and the cooling plate 14, the process gas causes the electrode to The plate corrodes, and the corrosion products peel off and become particles, contaminating the wafer (substrate to be processed) 8.
When the anti-corrosion film 210 is formed on the first surface 31 of the electrode plate 3 via the base film 220, the components of the anti-corrosion film diffuse into the electrode plate 3, are emitted from the plasma emission surface into the chamber, and are exposed to the wafer. (substrate to be processed) can be prevented from being contaminated. Furthermore, since the adhesion of the corrosion-resistant film 210 to the electrode plate 3 is improved, peeling becomes less likely to occur, and particle generation can be further reduced.

When the corrosion-resistant film 210 is amorphous, corrosion resistance can be further exhibited. On the other hand, if there is a grain boundary in the corrosion-resistant film, it becomes a high-speed diffusion path for corrosive gas, and corrosion of the electrode plate may progress from that part.
When the corrosion-resistant film 210 is a highly hard film, corrosion resistance can be further exhibited. It is believed that the hardness of a film generally has a correlation with its density, and that the higher the density, the higher the hardness. A high film density makes it difficult for corrosive gases to penetrate into the film. On the other hand, if the corrosion-resistant film has low hardness and is easily scratched, corrosion may proceed from the scratched portion.
When the corrosion-resistant film 210 is a flat film with small surface roughness, corrosion resistance can be further exhibited. It is thought that a flat film with a small surface roughness tends to have a tendency for corrosive gases to be more difficult to adsorb and desorb than a film with a highly rough and complexly shaped surface.

If the thickness of the corrosion-resistant film 210 is thinner than 30 nm, the corrosion-resistant film 210 will have many defects such as pinholes, corrosive gas will enter through the defects, and the first surface 31 of the electrode plate 3 will corrode. If corrosion products flake off, they may become particles.
If the film thickness of the corrosion-resistant film 210 is thicker than 5000 nm, film stress becomes large, and there is a possibility that the corrosion-resistant film 210 will peel off over a wide range.

When the defect density of the corrosion-resistant film 210 becomes larger than 1.24 pieces/ ^mm2 , corrosive gas enters through defects such as pinholes, causing local corrosion of the first surface 31 of the electrode plate 3, resulting in corrosion. The product gas may rupture the membrane and generate particles.

(Second embodiment)
A plasma etching apparatus 1A according to the second embodiment differs from the plasma etching apparatus 1 according to the first embodiment in an electrode structure 20A. In FIGS. 1 and 4, the same components as in the first embodiment are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

4(a) shows the electrode structure 20A, FIG. 4(b) shows the cooling plate 14, and FIG. 4(c) shows the electrode plate 3. In the electrode plate 3 of the electrode structure 20A, a corrosion-resistant film 210 is also formed on the inner peripheral surface 11A of the downstream gas flow path 11, compared to the electrode plate 3 of the first embodiment. The cooling plate 14 is different from the cooling plate 14 of the first embodiment in that the corrosion-resistant film 230 is formed on the inner peripheral surface 15A of the upstream gas flow path 15 and on the electrode contact surface 142 where the outlet 152 of the upstream gas flow path 15 is formed. is also formed.

Like the corrosion-resistant film 210, the corrosion-resistant film 230 is formed as a fluoride film, a C-containing film, or a noble metal film, and protects the cooling plate 14 from corrosion caused by process gas. The fluoride film is preferably a film containing any of the elements Al, Zr, Zn, Mg, Ce, Ag, Y, Fe, Cu, Cr, and Ni, and the C-containing film is preferably a film consisting only of C, or A film containing C and Si is preferred, and the noble metal film is preferably a film made of an Ag alloy.
The thickness of the corrosion-resistant film 230 is preferably 30 nm or more and 5000 nm or less.
The corrosion-resistant film 230 preferably has a defect density such as pinholes and cracks of 1.24 pieces/mm ² or less.

Film formation on the electrode plate 3 and the cooling plate 14, including the inner peripheral surface 11A of the downstream gas flow path 11 and the inner peripheral surface 15A of the upstream gas flow path 15, is performed using chemical vapor deposition (hereinafter referred to as CVD). ) or atomic layer deposition.

Although not shown, the corrosion-resistant film 230 may also be formed on the electrode contact surface 142 of the cooling plate 14 via a base film. By providing the base film, the adhesion between the corrosion-resistant film 230 and the electrode contact surface 142 of the cooling plate 14 is improved.

In the electrode structure 20A, the corrosion-resistant film 210 of the electrode plate 3 is in close contact with the corrosion-resistant film 230 of the cooling plate 14.

In the electrode structure 20A of the plasma etching apparatus 1A, even if the process gas enters and stagnates between the electrode plate 3 and the cooling plate 14, the first surface 31 of the electrode plate 3 is covered with the anti-corrosion film 210, and further cooling is prevented. Since the electrode contact surface 142 of the plate 14 is covered with the corrosion-resistant film 230, corrosion of the first surface 31 of the electrode plate 3 and the electrode contact surface 142 of the cooling plate 14 can be prevented. In addition, since the inner peripheral surface 11A of the downstream gas flow path 11 is covered with the corrosion-resistant film 210 and the inner peripheral surface 15A of the upstream gas flow path 15 is covered with the corrosion-resistant film 230, the inner peripheral surface of the downstream gas flow path 11 is Corrosion of the surface 11A and the inner peripheral surface 15A of the upstream gas flow path 15 can be prevented. According to the electrode structure 20A, generation of particles can be further prevented.

Furthermore, the inner peripheral surface 11A of the downstream gas flow path 11 is covered with the corrosion-resistant film 210, and the inner peripheral surface 15A of the upstream gas flow path 15 is covered with the corrosion-resistant film 230, so that the inner peripheral surface 11A and the inner peripheral surface 15A is corroded by the process gas, increasing the inner diameter of the gas flow path and shortening the service life.

The present invention can be implemented without being limited to the above-described embodiments.
In the electrode structure 20A, the corrosion-resistant film 230 covers the inner peripheral surface 15A of the upstream gas flow path 15, but the corrosion-resistant film 230 on the inner peripheral surface 15A may be omitted.

In the electrode structures 20 and 20A, a corrosion-resistant film may be formed on the inner peripheral surface 15A of the upstream gas flow path 15 and the inner peripheral surface 11A of the downstream gas flow path 11, and a corrosion-resistant film may be formed on the inner peripheral surface 15A and the inner peripheral surface 11A. Whether or not to form a corrosion film can be selected as required. The corrosion-resistant film on the inner circumferential surface 11A of the gas flow passage may also be formed with the base film 220 interposed therebetween.
When the inner circumferential surface 15A of the upstream gas flow path 15 and the inner circumferential surface 11A of the downstream gas flow path 11 are covered with anti-corrosion films 210 and 230, when used for a long time, process gas There is a risk that the surfaces of the corrosion-resistant films 210, 230 may be altered and the altered areas may peel off and become particles, but this can be avoided by omitting the corrosion-resistant films 210, 230.

A. First test (1) Corrosive gas exposure test (1-1) Test details A sample consisting of a substrate on which various films have been formed is exposed to corrosive gas, and the appearance of the film after exposure and the defects in the film after exposure are measured. The number of particles, the degree of corrosion on the surface of the substrate after exposure, and the number of particles generated on the sample after exposure were confirmed.

(1-2) Sample As a substrate, a Si wafer cut to a size of 2 cm in length and 2 cm in width was used for appearance evaluation, defect density evaluation, and surface corrosion evaluation, and a 4-inch Si wafer was used for particle generation evaluation. there was.
Examples 1 to 14 used samples with different film thicknesses of 30 nm or more and 5000 nm or less, and Al ₂ O ₃ with a film thickness of 200 nm and poor corrosion resistance. Comparative Example 1 was prepared with a film formed thereon, Comparative Example 2 and Comparative Example 3 were prepared with a film thickness of less than 30 nm and greater than 5000 nm, and Comparative Example 4 was prepared without a film. The structure, film formation conditions, and film formation method of each sample are described below.

(1-2-1) Examples 1 to 4
The membrane of Example 1 was composed of _MgF2 , the membrane of Example 2 was composed of _YF3 , the membrane of Example 3 was composed of _AlF3 , and the membrane of Example 4 was composed of _CeF3 . There is.
Film forming method: Vacuum deposition Film forming conditions Vapor deposition material: MgF ₂ , YF _3, AlF ₃ , CeF ₃
Film formation start pressure: 2×10 ^-3 Pa
Automatic pressure control (APC): None Substrate temperature: 300℃
Substrate dome rotation speed: 20 rpm

(1-2-2) Example 5 to Example 11, Comparative Example 2 to Comparative Example 3
The films of Examples 5 to 8 are made of C, the films of Examples 9 to 11 are made of SiC, and the films of Comparative Examples 2 to 3 are made of C.
Film forming method: Sputtering Film forming conditions Target: C, SiC
Target size: φ125mm, thickness 5mm
Discharge power (power density): Pulse DC 1000W (8.1W/cm ² )
Pulse conditions: frequency 50kHz, duty ratio 20%
Film formation start pressure: 7×10 ^-4 Pa
Sputtering gas total pressure: 0.67Pa
Ar flow rate: 50sccm
Substrate temperature: Room temperature (no heating or cooling)

(1-2-3) Example 12
The film of Example 12 is made of Ag alloy.
Film forming method: Sputtering Film forming conditions Target: Ag alloy Target size: 126 mm long, 178 mm wide, 6 mm thick
Discharge power (power density): DC 300W (1.3W/cm ² )
Film formation start pressure: 7×10 ^-4 Pa
Sputtering gas total pressure: 0.3Pa
Ar flow rate: 50sccm
Substrate temperature: Room temperature (no heating or cooling)

(1-2-4) Example 13 (C film)
Example 13 is composed of C.
Film forming method: RF plasma CVD
Film-forming conditions Reactive gas: CH ₄ , H ₂
Gas total pressure: 25Pa
RF power: 2W/ ^cm2
Substrate temperature: 250℃

(1-2-5) Example 14 (SiC film)
Embodiment 14 is made of SiC.
Film forming method: RF plasma CVD
Film-forming conditions Reactive gas: SiH ₄ , CH ₄ , H ₂
Gas total pressure: 100Pa
RF power density: 2W/ ^cm2
Substrate temperature: 400℃

(1-2-6) Comparative example 1 (Al ₂ O ₃ film)
Comparative Example 1 is composed of Al ₂ O ₃ .
Film formation method: Vacuum deposition Film formation conditions Vapor deposition material: Al ₂ O ₃ (1 to 3 mm)
Film formation start pressure: 5×10 ^-3 Pa
Automatic pressure control (APC): Yes ( _O2 introduction)
Substrate temperature: 300℃
Substrate dome rotation speed: 20 rpm

(1-3) Test procedure Perform the following first step A1 to fourth step A4 in order.
First step A1: As shown in FIG. 5, a gas generation tank 410 that contains anhydrous hydrofluoric acid and generates corrosive gas (HF gas) by flowing nitrogen gas into the anhydrous hydrofluoric acid as a carrier gas, and a sample 300 are installed. A test apparatus 400 is assembled, including a reaction tank 420 housed at the bottom and used to expose the sample 300 to the corrosive gas from the gas generation tank 410. As the gas generation tank 410 and the reaction tank 420, containers made of PFA (fluororesin) are used, respectively.
Second step A2: Place the sample into the reaction tank with the film forming side facing up.
Third step A3: HF gas is passed through the reaction tank under the following test conditions to expose the membrane surface to the gas. Note that a highly corrosive gas used for plasma etching of semiconductor products can be used as the corrosive gas for testing. In this example, HF gas, which is particularly corrosive, was used. The size of the reaction tank can be adjusted depending on the size and number of samples.
<Test condition>
Nitrogen gas flow rate: 60ml/min
Corrosive gas (HF) source: Anhydrous hydrofluoric acid HF concentration in circulating gas: 40-60%
Exposure time: 24 hours Test temperature: Room temperature Fourth step A4: After being exposed for a predetermined time, the sample is taken out and washed with water, and the appearance, number of defects, degree of surface corrosion, and number of particles generated are evaluated.

(2) Evaluation The appearance of the film after exposure, the number of defects on the film after exposure, the degree of corrosion on the surface of the substrate after exposure, and the number of particles generated on the sample after exposure were evaluated as follows.

(2-1) Method for evaluating the appearance of samples subjected to corrosive gas exposure tests Visually observe the surface condition of the film, such as peeling, discoloration, deformation, etc., and compare it with the state before the corrosive gas exposure test. If there is no change in the surface condition, the test is passed; if there is, it is judged to be a fail. Table 1 shows the appearance evaluation. In Table 1, passing is indicated as "OK" and failing is indicated as "NG".

(2-2) Method for evaluating the number of defects in a corrosion-resistant film When a corrosion-resistant film contains many defects such as pinholes, corrosive gas enters through the defects, causing local corrosion of the substrate. The locations on the board that are corroded by the corrosive gas are called corrosion points. Furthermore, the corrosion-resistant film may be broken by the gas of the corrosion product, and particles may be generated. This phenomenon can occur if there are defects even if the membrane material itself has corrosion resistance.
If we define that the density of corrosion points on the substrate generated by the corrosive gas exposure test corresponds to the density of defects such as pinholes that originally existed in the corrosion-resistant film, then Defect density can be obtained.
According to this definition, using a sample subjected to a corrosive gas exposure test, corrosion points originally existing in the corrosion-resistant film can be detected by counting corrosion points with a diameter of 40 μm or more on an optical micrograph taken with a field of view of 4 mm in length and 4 mm in width. The number of defects that were considered to have occurred was calculated.
If the number of defects was less than 20, it was judged as "pass", and if there were 20 or more defects, it was judged as "fail". Table 1 shows the evaluation of the number of defects. In Table 1, among the passes, those with fewer than 5 defects are expressed as "excellent," those with 5 or more and less than 20 defects are expressed as "good," and those that fail are expressed as "NG."

(2-3) Method for evaluating the degree of surface corrosion of samples that have undergone corrosive gas exposure tests Samples that pass the appearance evaluation are targeted. Depth direction elemental analysis is performed using XPS to examine the degree of corrosion on the sample surface. The analysis conditions in the depth direction by XPS are shown below.
<Analysis conditions>
Sputter ion: Ar ⁺
Total sputtering time: 60 minutes Sputtering speed: 0.3nm/min (0 to 30 minutes after starting sputtering)
1.1nm/min (after 30 minutes to 60 minutes)
Analysis interval: Analysis is performed every minute of sputtering.
Analyzed element type: F, constituent elements of each corrosion-resistant film material. Since the sample surface changes greatly due to exposure tests, the sputtering speed is sputtered slowly to dig in the depth direction, and the speed is increased from a certain depth. It is expressed by the conditions and the film formation rate when sputtering the SiO ₂ film of the reference sample.
Regarding the degree of surface corrosion, a case where no corrosion products are detected is considered as "pass", a case where corrosion products are detected only on the outermost surface is also considered as "pass", and anything else is considered as "fail".
In FIG. 6, (a) shows the XPS data of Example 6 (C film), (b) shows the XPS data of Example 10 (SiC film), and (c) shows the XPS data of Comparative Example 1 (Al ₂ O ₃ film). shows. Since no F was detected in the C film, and F was present only on the outermost surface of the SiC film, both were passed. Although the Al ₂ O ₃ film failed in the visual appearance evaluation stage, XPS data is shown for reference. Since most of the Al ₂ O ₃ film was peeled off, almost no Al was detected and a large amount of Si was detected, confirming that the Si substrate was exposed.
Table 1 shows the evaluation of the degree of surface corrosion. In Table 1, of the passes, those in which no corrosion products were detected are designated as "excellent," those in which corrosion products were detected only on the outermost surface are designated as "good," and those that failed are designated as "NG."

(2-4) Test procedure and evaluation method for the number of particles generated in a sample subjected to a corrosive gas exposure test (2-4-1) Test procedure Perform the following first step B1 to fourth step B6 in order.
First step B1: A sample (Si wafer) that was subjected to a corrosive gas exposure test in a device with a vacuum chamber such as a plasma etching device, and another clean sample (Si wafer: dummy wafer) that has not been subjected to any treatment. ) are placed side by side.
Second step B2: The chamber is evacuated until the degree of vacuum reaches 5×10 ⁻³ Pa.
Third step B3: Maintain a vacuum level of 5×10 ⁻³ Pa for 10 minutes.
Fourth step B4: Introduce dry air, nitrogen gas, etc. to return the chamber to atmospheric pressure.
Fifth step B5: Repeat the second step B2 to fourth step B4 10 times.
Sixth step B6: Take out the dummy wafer, measure the number of particles on the dummy wafer with a particle counter, or analyze the dark field image of an optical microscope, calculate the total area of bright spots (particles), and calculate the number of particles n1. do.
(2-4-2) Evaluation method The number of particles n1 on the dummy wafer is the number n2 of particles generated when the above particle generation test is performed only with the dummy wafer without placing the Si wafer that was subjected to the corrosive gas exposure test. If it is smaller than the number n3 (hereinafter referred to as reference value) multiplied by 10, it is judged as "pass", and if the number of particles n1 is larger than reference value n3, it is judged as "fail". Table 1 shows the evaluation of the number of particles n1. In addition, in Table 1, if the number of particles n1 is less than 3 times the number of particles generated n2, it is judged as "excellent", and if the number of particles n1 is 3 times or more and less than 10 times the number of particles generated, n2, it is judged as "good". Also, failure is indicated as "NG".

(3) Summary of the first test The corrosion-resistant films of Examples 1 to 14 passed the appearance evaluation, defect density evaluation, and surface corrosion evaluation, and the number of particles generated also passed. It was confirmed that this film is suitable as a film to protect the cooling surface.
The corrosion-resistant films of Comparative Examples 1 to 3 failed both the appearance evaluation and the defect density evaluation, and also failed in the number of particles generated, confirming that they are not suitable for use on the cooling surface of electrode plates. .

(Defect in corrosion-resistant film)
If a corrosion-resistant film contains many defects such as pinholes, corrosive gases may enter through them, causing local corrosion of the base material, and the film may be ruptured by corrosion product gas, generating particles. Therefore, fewer defects are more advantageous as a corrosion-resistant film. When there are 20 defects in a visual field of 4 mm in length and 4 mm in width, the defect density is 1.25 defects/ ^mm2 , and the corresponding number of particles generated in Comparative Examples 1 to 3 is rejected. Therefore, it is desirable that the corrosion-resistant film provided on the electrode plate or the cooling plate has a defect density of 1.24 pieces/mm ² or less.

(Crystallinity of corrosion-resistant film)
Grain boundaries may serve as high-speed diffusion paths for corrosive gases, but since amorphous materials do not have these, they are advantageous as corrosion-resistant films. As shown in FIG. 7(a) is the XRD data of Example 6 (C film), and FIG. 7(b) is the XRD data of Example 10 (SiC film). No. 10 (SiC film) has no crystal peak observed and is amorphous. On the other hand, the XRD data _of Example 1 (MgF ₂ film) shown in FIG. 8(a) and the XRD data of Example ₂ (YF ₃ film) shown in FIG. The MgF ₂ film of Example 1 and the YF ₃ film of Example 2 are crystalline films. Note that the XRD measurement was performed using a thin film X-ray diffraction method, and the incident angle of X-rays was 1 degree. Although the MgF ₂ film of Example 1, the YF ₃ film of Example 2, and the Ag alloy film of Example 12 are crystalline films, they have good corrosion resistance because they are dense films.

(Hardness of corrosion-resistant film)
If the film has low hardness and is easily scratched, corrosion of the first surface 31 of the electrode plate 3 may progress from the scratched portion, but a high hardness film can avoid this and is therefore advantageous as a corrosion-resistant film.
Further, the hardness of a film generally has a correlation with its density, and the higher the density, the higher the hardness often tends to be. A high film density can be expected to make it difficult for corrosive gases to penetrate into the film, which is advantageous as a corrosion-resistant film. Table 2 shows the indentation hardness of the corrosion-resistant film as the hardness of the film of the present invention. The indentation hardness was measured by the nanoindentation method, using a Berkovich indenter, and the maximum load was set so that the indentation depth was within 1/10 of the film thickness. In addition, the corrosion-resistant film is manufactured by "A. The film structure, film forming method, and film forming conditions are the same as those of "A.1 Test". The same membrane as ``First Test'' has ``A. The sample numbers of "First Test" are used in Table 2.

<Surface roughness>
A flat film with a small surface roughness tends to have a tendency for corrosive gases to be more easily adsorbed and desorbed than a film with a highly rough and complexly shaped surface. This is advantageous as a corrosion-resistant film. Table 3 shows the surface roughness of the corrosion-resistant film. An area of 1 μm square was observed using an atomic force microscope, and the average surface roughness Ra and maximum height difference PV were measured.

B. Second test (1) Corrosion-resistant film on the gas flow path (inner peripheral surface) of the electrode plate (1-1) Test details An electrode plate with various corrosion-resistant films formed on the first surface on the cooling plate side was used as a sample. The presence or absence of a corrosion-resistant film on the gas flow path (inner peripheral surface) was confirmed.

(1-2) Sample The electrode plate is a Si electrode plate with multiple gas channels passing through it from the first surface to the second surface and a corrosion-resistant film formed on the first surface that contacts the cooling plate. Using. The size of the Si electrode plate is 418 mm in diameter and 14 mm in thickness, and the thickness of the corrosion-resistant film is 200 nm.
In addition, the corrosion-resistant film is manufactured by "A. The film structure, film forming method, and film forming conditions are the same as those of "A.1 Test". The same membrane as ``First Test'' has ``A. Use the sample number from ``First Test''.

(1-3) Method for analyzing corrosion-resistant film on gas flow path (inner peripheral surface) of electrode plate The following first step C1 to third step C3 are performed in order.
First step C1: A corrosion-resistant film with a thickness of 200 nm is formed on the first surface of the Si electrode plate (the cooling surface in contact with the cooling plate).
Second step C2: Cut the electrode plate so that the cross section of the gas flow path is exposed, and embed it in resin to prepare an observation sample.
Third step C3: Scanning Electron Microscope - Energy Dispersive X-ray Spectrometry (hereinafter referred to as SEM-EDX) is applied to the area from the entrance of the inner peripheral surface of the gas flow path to a depth of 1 mm. ) to perform line analysis. Line analysis conditions by SEM-EDX are shown below.
Analysis position: Analyze points P1 to P5 shown in Figure 9(b). P1 is set near the first surface 512.
Line analysis scanning direction: Scan in the direction shown by the arrow in FIG. 9(b) so as to cross the position corresponding to the inner peripheral surface of the gas flow path.
Incident voltage: 15kV
WD: Around 10mm Magnification: About 5000x Analyzed element types: Elements constituting each corrosion-resistant film, Si (component of electrode plate), C (component of embedding resin)
Note that FIG. 9B is an enlarged view of the part surrounded by the broken line in FIG. 511A is the inner circumferential surface of the gas flow path 510, 512 is the first surface that is provided with the inlet 511 and comes into contact with the cooling plate, 513 is the outlet of the gas flow path 510, and 514 is the first surface that is provided with the outlet 513 and is in contact with the cooling plate. (Cooling surface) A second surface 520 located on the opposite side of 512 is a corrosion-resistant film.

(2) Method for evaluating the corrosion-resistant film on the gas flow path (inner peripheral surface) of the electrode plate If the elements constituting the corrosion-resistant film are detected from the inner peripheral surface of the gas flow path within a range of 1 mm deep from the film formation surface. The evaluation results are shown in Table 4 as "present" and "absent" if not detected.

(3) Summary of the second test In the samples of Examples 13 and 14, it was confirmed that the corrosion-resistant film 520 was formed on the inner peripheral surface 511A of the gas flow path 510.
In the samples of Examples 1 to 12 and Comparative Examples 1 to 3, it was confirmed that the corrosion-resistant film 520 was not formed on the inner peripheral surface 511A of the gas flow path 510.
When the corrosion-resistant film 520 is formed on the inner circumferential surface 511A of the gas flow path 510, the surface of the corrosion-resistant film 520 is altered by the process gas or plasma when used for a long period of time, causing particles to peel off. Although this may occur, this can be avoided if the corrosion-resistant film 520 is not formed on the inner circumferential surface 511A.
If the corrosion-resistant film 520 is not formed on the inner peripheral surface 511A of the gas flow path 510, there is a risk that the inner peripheral surface 511A will be corroded by the process gas and the inner diameter of the gas flow path 510 will increase, resulting in a shortened service life. This can be avoided if the corrosion-resistant film 520 is formed on the inner circumferential surface 511A.

1,1A Etching device 3 Electrode plate 31 First surface 32 Second surface 11 Downstream gas flow path 111 Inlet 112 Outlet 11A Inner peripheral surface 14 Cooling plate 141 Surface 142 Electrode contact surface 15 Upstream gas flow path 151 Inlet 152 Outlet 15A Inner circumference Surfaces 20, 20A Electrode structures 210, 230 Corrosion-resistant film 220 Base film

Claims (8)

An electrode plate provided with a downstream gas flow path disposed on the electrode contact surface side of the cooling plate and communicating with an upstream gas flow path penetrating from one surface of the cooling plate to the electrode contact surface,
A corrosion-resistant film against process gas flowing through the upstream gas flow path of the cooling plate is formed on a first surface side that provides an inlet of the downstream gas flow path and contacts the cooling plate. Electrode plate for plasma processing equipment. The electrode plate for a plasma processing apparatus according to claim 1, wherein the corrosion-resistant film is any one of a fluoride film, a C-containing film, and a noble metal film. The fluoride film contains any element of Al, Zr, Zn, Mg, Ce, Ag, Y, Fe, Cu, Cr, and Ni,
The C-containing film consists only of C, or contains C and Si,
3. The electrode plate for a plasma processing apparatus according to claim 2, wherein the noble metal film contains an Ag alloy. The electrode plate for a plasma processing apparatus according to claim 1, wherein the corrosion-resistant film has a thickness of 30 nm or more and 5000 nm or less. The electrode plate for a plasma processing apparatus according to claim 1, further comprising a base film between the first surface and the corrosion-resistant film. The electrode plate for a plasma processing apparatus according to claim 1, wherein the corrosion-resistant film is heat-treated. An electrode plate for a plasma processing apparatus according to any one of claims 1 to 6,
An electrode structure for a plasma processing apparatus, comprising: the cooling plate having an electrode contact surface that provides an outlet of the upstream gas flow path and contacts the first surface of the electrode plate. 8. The electrode structure for a plasma processing apparatus according to claim 7, wherein the corrosion-resistant film is also formed on the electrode contact surface of the cooling plate.

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