Structural members

Abstract

The present invention provides a structural member that has sufficient durability against plasma while allowing the protective film to be easily removed from the substrate. [Solution] The structural member 10 comprises a base material 100 which is a sintered ceramic body, and a protective film 200 which covers the surface 110 of the base material 100. The protective film 200 mainly contains one of the following as its main component: an oxide of an alkaline earth metal, a fluoride of an alkaline earth metal, or an acid fluoride of an alkaline earth metal, and the indentation hardness of the protective film 200 is 8 GPa or less.

Description

Technical Field

[0001] The present invention relates to a structural member.

Background Art

[0002] A structural member having a protective film on the surface of a base material is used in various fields such as semiconductor manufacturing equipment. For example, as described in Patent Document 1 below, in a semiconductor manufacturing apparatus, a protective film for protecting the base material from plasma is formed on the surface of the base material constituting the inner wall of the chamber. As the base material, a sintered body of ceramics such as alumina is used. As the protective film, rare earth oxides such as yttria (Y2O3), rare earth fluorides such as yttrium fluoride (YF3), and rare earth oxyfluorides such as yttrium oxyfluoride (YOF) are often used.

[0003] When processes such as etching are repeated in a semiconductor manufacturing apparatus, the protective film gradually wears out. Therefore, it is necessary to periodically replace the structural member including the worn protective film with a new structural member. After removing the worn old protective film from the base material, the structural member removed from the semiconductor manufacturing apparatus is reused after forming a new protective film on the surface of the base material.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The worn protective film is removed from the substrate surface by applying physical force, such as grinding or polishing. In this process, the higher the hardness of the protective film, the greater the force required to remove it, and the greater the damage inflicted on the substrate surface. If the surface properties (roughness, etc.) of the substrate change significantly as a result of removing the protective film, a process to restore the surface properties of the substrate becomes necessary before forming a new protective film. It is possible to minimize the physical force applied to the protective film so as not to alter the surface properties of the substrate, but in this case, the time required to remove the protective film becomes significantly longer.

[0006] Furthermore, it is believed that protective films primarily composed of rare earth oxides and the like exhibit higher plasma resistance the higher their hardness. Patent Document 1 describes using a material with high hardness as the material for the protective film so that it can withstand abrasion during plasma treatment. In recent years, the plasma resistance required for protective films has increased even further, and there is a tendency to adopt materials with even higher hardness for protective films. For this reason, it is expected that removing the protective film while generally maintaining the surface properties of the substrate will become even more difficult in the future.

[0007] This invention has been made in view of these problems, and its objective is to provide a structural member that has sufficient durability against plasma while allowing the protective film to be easily removed from the substrate. [Means for solving the problem]

[0008] To solve the above problems, the structural member according to the present invention comprises a base material which is a sintered ceramic body and a protective film covering the surface of the base material. The protective film mainly contains one of the following as its main component: an oxide of an alkaline earth metal, a fluoride of an alkaline earth metal, or an acid fluoride of an alkaline earth metal, and the indentation hardness of the protective film is 8 GPa or less.

[0009] Conventionally, when rare earth oxides or the like were used as the material for the protective film, it was considered necessary to increase the hardness of the protective film to about 10 GPa, and the protective film was formed under film formation conditions that were necessary to obtain such hardness.

[0010] On the other hand, experiments conducted by the present inventors have revealed a new finding: when an alkaline earth metal oxide, alkaline earth metal fluoride, or alkaline earth metal acid fluoride is used as the material for the protective film, the protective film can exhibit plasma resistance at the same level as conventional films without increasing its hardness as in conventional films.

[0011] Therefore, in the structural members with the above configuration, alkaline earth metal oxides are used as the material for the protective film, while keeping the indentation hardness below 8 GPa. As mentioned earlier, such a protective film has plasma resistance comparable to conventional protective films and can be easily removed while generally maintaining the surface properties of the substrate. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a structural member that has sufficient durability against plasma while allowing the protective film to be easily removed from the substrate. [Brief explanation of the drawing]

[0013] [Figure 1] This figure schematically shows a cross-section of the structural member according to this embodiment. [Figure 2] This diagram illustrates the changes in the surface properties of the substrate. [Figure 3] This table shows a summary of experimental results regarding the surface properties of the substrate after the protective film has been removed. [Modes for carrying out the invention]

[0014] This embodiment will now be described with reference to the attached drawings. To facilitate understanding of the explanation, the same reference numerals are used for identical components in each drawing whenever possible, and redundant explanations are omitted.

[0015] The structural member 10 according to this embodiment is used, for example, as a component that constitutes the inner wall of a processing chamber in semiconductor manufacturing equipment (not shown), such as a plasma etching apparatus. However, the application of such a structural member 10 is merely an example and is not limited to semiconductor manufacturing equipment.

[0016] As shown in Figure 1, the structural member 10 comprises a base material 100 and a protective film 200. In a plasma etching apparatus, the surface 210 of the protective film 200 is exposed to the space inside the chamber. The protective film 200 is provided for the purpose of protecting the surface 110 of the base material 100 from plasma.

[0017] The base material 100 is a component that occupies approximately the entirety of the structural member 10. In this embodiment, the base material 100 is a sintered ceramic body mainly composed of alumina (Al2O3), but it may be a different type of sintered ceramic body. Also, in this embodiment, the surface 110 of the base material 100 is a flat surface, but the surface 110 may be a curved surface or the like, rather than a flat surface. Furthermore, a slope may be provided on a part of the surface 110.

[0018] As mentioned earlier, the protective film 200 is a film formed to protect the substrate 100 from plasma. The protective film 200 is formed to cover the entire surface 110 of the substrate 100. The material used for the protective film 200 is a material mainly composed of one of the following: an alkaline earth metal oxide, an alkaline earth metal fluoride, or an alkaline earth metal acid fluoride. The thickness of the protective film 200 is appropriately set according to the length of time for which durability must be maintained. In this embodiment, the thickness of the protective film 200 is approximately 10 μm.

[0019] In this specification, the "main component" refers to a compound that is relatively more contained in the protective film 200 than other compounds contained in the protective film 200 through quantitative or semi-quantitative analysis by X-ray Diffraction (XRD) of the protective film 200. For example, the main component is the compound most contained in the protective film, and the ratio occupied by the main component in the protective film is greater than 50% in terms of volume ratio or mass ratio. The ratio occupied by the main component is more preferably greater than 70%, and preferably greater than 90%. The ratio occupied by the main component may be 100%.

[0020] Examples of the above "alkaline earth metal oxide" include magnesium oxide and the like. Examples of the "alkaline earth metal fluoride" include calcium fluoride (CaF2), magnesium fluoride (MgF2), and the like. Examples of the "alkaline earth metal fluorooxide" include magnesium fluorooxide, calcium fluorooxide, and the like.

[0021] When forming the protective film 200 using any of the above materials, it is preferable to set the film formation method and film formation conditions so that the indentation hardness of the protective film 200 is 8 GPa or less. The reasons are as follows.

[0022] When processes such as etching are repeated in the semiconductor manufacturing apparatus, the protective film 200 gradually wears out. Therefore, it is necessary to periodically replace the structural member 10 including the worn protective film 200 with a new structural member 10. After removing the worn old protective film 200 from the base material 100, the structural member 10 removed from the semiconductor manufacturing apparatus is reused after forming a new protective film 200 on the surface 110 of the base material 100.

[0023] The worn protective film 200 is removed from the surface 110 of the substrate 100 by applying physical force, such as grinding or polishing. In this case, the higher the hardness of the protective film 200, the greater the force that must be applied to the protective film 200 during the removal process, and the greater the damage inflicted on the surface 110 of the substrate 100. For example, this force may cause some crystallites to fall off the surface 110, potentially resulting in a rough surface, as shown in the example in Figure 2(A).

[0024] If the properties (such as roughness) of the surface 110 change significantly upon removal of the protective film 200, a process to restore the properties of the surface 110 will be necessary before forming a new protective film 200. It is conceivable to keep the physical force applied to the protective film 200 small enough so as not to change the properties of the surface 110, but in this case, the time required to remove the protective film 200 will be significantly longer.

[0025] Therefore, in this embodiment, as described above, the indentation hardness of the protective film 200 is set to 8 GPa or less. By keeping the hardness of the protective film 200 at this level, damage to the surface 110 of the substrate 100 can be sufficiently suppressed when the protective film 200 is removed by applying physical force. Accordingly, as shown in the example in Figure 2(B), for example, the protective film 200 can be easily removed from the surface 110 without significantly changing the properties of the surface 110. Subsequently, when reforming the protective film 200 on the surface 110, the process for restoring the properties of the surface 110 can be simplified or even eliminated compared to conventional methods.

[0026] Traditionally, protective films have been made primarily from materials such as rare earth oxides like yttria. It was believed that the higher the hardness of such protective films, the greater their resistance to plasma. In recent years, however, the plasma resistance required for protective films has increased even further, and there is a trend towards using materials with even higher hardness. Therefore, it was anticipated that removing protective films while largely maintaining the surface properties of the substrate would become increasingly difficult in the future.

[0027] Under these circumstances, the inventors have been investigating the use of materials containing alkaline earth metals instead of rare earth elements as materials for protective films. As a result, they have obtained new findings that when any of alkaline earth metal oxides, alkaline earth metal fluorides, or alkaline earth metal acid fluorides are used as materials for protective films, the protective film can exhibit plasma resistance at the same level as conventional films without increasing its hardness as in conventional films.

[0028] Based on the above findings, the inventors came up with the idea of ​​using an alkaline earth metal oxide or the like as the material for the protective film 200, as in this embodiment, while keeping the indentation hardness of the protective film 200 below 8 GPa. With this configuration, it was possible to obtain a protective film 200 that can be easily removed while maintaining the surface properties of the substrate 100, while ensuring plasma resistance at a level comparable to conventional protective films.

[0029] Furthermore, given the current international situation, there are concerns that it may become difficult to obtain a stable and continuous supply of materials such as rare earth oxides, which have been used as materials for protective films, in the future. As in this embodiment, if alkaline earth metal oxides or the like can be used as an alternative material for the protective film 200, it is preferable from the viewpoint of supply stability.

[0030] The inventors created numerous samples of structural members 10, each differing in the material of the protective film 200, and then experimentally confirmed the surface properties of the substrate 100 after removing the protective film 200 for each sample. Figure 3 shows a summary of some of the experimental results.

[0031] Of the samples No. 1 to 7 shown in Figure 3, No. 1 to 4 are samples of the structural member 10 according to this embodiment. No. 5 to 7 are samples of the structural member 10 according to comparative examples.

[0032] In the table in Figure 3, the "Base Material" column shows the material that each sample's base material 100 contains as its main component. In the example in Figure 3, all samples' base material 100 contains alumina as its main component.

[0033] The "Protective Film" column in the table in Figure 3 shows the main component material of the protective film 200 for each sample. Protective film 200 for No. 1 contains calcium fluoride (CaF2) as its main component. Protective film 200 for No. 2, No. 3, and No. 4 contains magnesium fluoride (MgF2) as its main component. Protective film 200 for No. 5 contains yttria (Y2O3) as its main component. Protective film 200 for No. 6 contains yttrium aluminum garnet (YAG) as its main component. Protective film 200 for No. 7 contains yttrium oxyfluoride (YOF) as its main component. The thickness of the protective film 200 was the same for all samples.

[0034] The "Manufacturing Method" column in the table in Figure 3 shows the film deposition method used to form the protective film 200 for each sample. In the example in Figure 3, the protective film 200 for all samples was deposited using the aerosol deposition method (AD method). Note that various methods other than the aerosol deposition method can be used to form the protective film 200. For example, the protective film 200 may be formed using physical vapor deposition (PVD) or chemical vapor deposition (CVD).

[0035] As is well known, in the aerosol deposition method, fine particles, which are the material for the protective film 200, are dispersed in a gas to form an "aerosol," which is then sprayed from a nozzle onto the surface 110 of the substrate 100 and collided with it. On the surface 110, the impact of the collision causes deformation and fragmentation of the fine particles, and as the fine particles combine with each other, they gradually accumulate to form the protective film 200.

[0036] In the table in Figure 3, the "Film Formation Conditions" column shows the flow rate of helium gas injected from the nozzle per unit time in units of (L / min). The flow rate for forming protective films 200 No. 1 and No. 2 was set to 5 L / min, the flow rate for forming protective film 200 No. 3 was set to 8 L / min, the flow rate for forming protective film 200 No. 4 was set to 10 L / min, the flow rate for forming protective film 200 No. 5 was set to 8 L / min, the flow rate for forming protective film 200 No. 6 was set to 15 L / min, and the flow rate for forming protective film 200 No. 7 was set to 10 L / min.

[0037] In the table in Figure 3, the "Indentation Hardness" column shows the measured indentation hardness of the protective film 200 for each sample in units of "GPa". The indentation hardness of protective film 200 for No. 1 was 2.8 GPa, for No. 2 it was 4.5 GPa, for No. 3 it was 6.8 GPa, for No. 4 it was 3.5 GPa, for No. 5 it was 11.4 GPa, for No. 6 it was 13.8 GPa, and for No. 7 it was 12.1 GPa.

[0038] Furthermore, the indentation hardness of each protective film 200 was determined by a micro-indentation hardness test (nanoindentation) against the surface 210. A Berkovich indenter was used, and the indentation depth was fixed at 200 nm. The indentation hardness (indentation hardness: H) was measured.IT ) was measured. H on surface 210 IT For measurement, a surface excluding scratches and dents was selected. Surface 210 may be pre-polished to create a smooth surface before measurement. The number of measurement points was set to at least 25. At least 25 H points were measured. IT The average value was used as the measured value of the indentation hardness for each sample. Other specific measurement conditions were adopted in accordance with ISO 14577, so their explanation is omitted here.

[0039] In the table in Figure 3, the "film removal force" column indicates the magnitude of the force required to remove the protective film 200 from the substrate 100 by applying physical force, categorized into three levels: "large," "medium," and "small." In setting this force, the magnitude of the force applied to each sample was individually determined so that the time required for the thickness of the protective film 200 to become 0 was the same for each sample.

[0040] For samples No. 5, No. 6, and No. 7, in which the protective film 200 mainly consisted of conventional rare-earth materials, the film removal force was "high," for sample No. 3 it was "medium," and for samples No. 1, No. 2, and No. 4 it was "low." Thus, it was confirmed that in all of the samples No. 1 to 4 according to this embodiment, the protective film 200 could be easily removed with less force than in the conventional method.

[0041] The "Substrate Surface After Film Removal" column in the table in Figure 3 shows the results of observing the properties of the surface 110 after removing the protective film 200 from each sample, as described above. If the exposed surface 110 generally maintained its original properties before the formation of the protective film 200, it was evaluated as "○". If the properties of the surface 110 had changed significantly from its original properties, it was evaluated as "×". The evaluation results for the surface 110 in each of the samples No. 1 to 4 were all "○", and the evaluation results for the surface 110 in each of the samples No. 5 to 7 were all "×". Thus, it was confirmed that in all of the samples No. 1 to 4 according to this embodiment, the surface 110 immediately after the removal of the protective film 200 generally maintained its original properties before the formation of the protective film 200. In other words, it was confirmed that a new protective film 200 can be formed on the surface 110 after the removal of the protective film 200 without any additional processing to restore its properties.

[0042] Furthermore, the inventors evaluated the plasma resistance of each of the samples No. 1 to 7. For this evaluation, the protective film 200 of each sample was exposed to a plasma atmosphere using an inductively coupled reactive ion etching (ICP-RIE) apparatus. The chamber pressure was 0.5 Pa, and the plasma exposure time was 1 hour. The power output was set to 1500 W for the ICP coil output and 750 W for the bias output. Sulfur hexafluoride (SF6) was used as the process gas, and this gas was supplied to the chamber at a flow rate of 100 sccm. After the plasma exposure was complete, the amount of thickness reduction of the protective film 200 in each sample, i.e., the etching rate, was measured. In the table in Figure 3, the "Etching Rate" column shows the etching depth per unit time of the protective film 200 of each sample exposed to plasma under the above conditions, expressed in units of "μm / h".

[0043] As a result, as shown in Figure 3, it was confirmed that the etching rates of all samples No. 1 to 7 were approximately the same. In other words, it was confirmed that the protective film 200 of each sample No. 1 to 4 according to this embodiment has the same level of plasma resistance as the protective film 200 of each sample No. 5 to 7 according to the comparative example.

[0044] As described above, it was confirmed that the protective film 200 has sufficient resistance to plasma when it contains one of the following as its main component: an alkaline earth metal oxide, an alkaline earth metal fluoride, or an alkaline earth metal acid fluoride, and its indentation hardness is 8 GPa or less. It was also confirmed that the protective film 200 can be easily removed from the substrate 100 without significantly altering the properties of the surface 110.

[0045] The thickness of the protective film 200 is preferably 1 μm or more and 15 μm or less. By keeping the thickness of the protective film 200 within this range, it is possible to achieve both the durability of the protective film 200 against plasma and the ease of removing the protective film 200 from the substrate 100.

[0046] The average crystallite size of the crystals constituting the protective film 200 is preferably 50 nm or less. By keeping the average crystallite size this small, the diameter of the particles generated when the protective film 200 is exposed to plasma and degrades can be sufficiently reduced.

[0047] Furthermore, the "average crystallite size" mentioned above refers to the average value of the diameters of multiple crystallites that appear in the cross-section when the protective film 200 is cut. The average crystallite size is calculated, for example, by taking a transmission electron microscope (TEM) image at a magnification of 400,000x or higher, and deriving the value from the average of the diameters of 15 crystallites approximated by a circular pattern in this image. At this time, by making the sample thickness sufficiently thin, to about 30 nm, during focused ion beam (FIB) processing, crystallites can be distinguished more clearly. It is preferable to appropriately select the imaging magnification within the range of 400,000x or higher.

[0048] The embodiments have been described above with reference to specific examples. However, this disclosure is not limited to these specific examples. Modifications made to these specific examples by those skilled in the art are also included within the scope of this disclosure, as long as they retain the features of this disclosure. The elements, their arrangement, conditions, shapes, etc., of each of the aforementioned specific examples are not limited to those illustrated and can be modified as appropriate. The elements of each of the aforementioned specific examples can be combined in different ways as appropriate, as long as no technical inconsistencies arise. [Explanation of Symbols]

[0049] 10: Structural members 100: Base material 110: Surface 200: Protective film

Claims

1. A ceramic sintered body is the base material, The substrate comprises a protective film covering the surface of the substrate, The protective film mainly contains one of the following: an oxide of an alkaline earth metal, a fluoride of an alkaline earth metal, or an acid fluoride of an alkaline earth metal. A structural member characterized in that the indentation hardness of the protective film is 8 GPa or less.

2. The structural member according to claim 1, characterized in that the base material contains alumina as the main component.

3. The structural member according to claim 1, characterized in that the protective film contains either magnesium fluoride or calcium fluoride as its main component.

4. The structural member according to claim 1, characterized in that the thickness of the protective film is 1 μm or more and 15 μm or less.

5. The structural member according to claim 1, characterized in that the average crystallite size of the crystals constituting the protective film is 50 nm or less.

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