Structural members

Abstract

To provide a structural member with sufficient durability against plasma. [Solution] The structural member 10 comprises a base material 100 and a protective film 200 covering the surface 110 of the base material 100. The protective film 200 contains crystals mainly composed of ytterbium oxide, and the lattice constant of these crystals is 10.530 × 10 -10 It is m or greater.

Description

[Technical Field]

[0001] This invention relates to a structural member. [Background technology]

[0002] Components of semiconductor manufacturing equipment, such as the inner walls of chambers, require durability against plasma. Therefore, it is common practice to use structural components with a protective film formed on the surface of a substrate, as described in Patent Document 1 below. For the protective film, materials such as yttria are often used. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-166808 [Overview of the project] [Problems that the invention aims to solve]

[0004] The inventors have been investigating the use of ytterbium oxide as a material for the protective film, and how to further improve the durability of the protective film against plasma.

[0005] 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. [Means for solving the problem]

[0006] To solve the above problems, the structural member according to the present invention comprises a base material and a protective film covering the surface of the base material. The protective film contains crystals mainly composed of ytterbium oxide, and the lattice constant of these crystals is 10.530 × 10 -10 It is m or greater.

[0007] Experiments conducted by the inventors confirmed a correlation between the lattice constant of a protective film containing crystals mainly composed of ytterbium oxide and the durability of the protective film against plasma. Furthermore, the lattice constant of the crystals in the protective film was 10.530 × 10⁻¹⁰. -10 It was also confirmed that forming the film to be greater than m sufficiently increases the durability of the protective film against plasma. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a structural member that has sufficient durability against plasma. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing a cross-section of a structural member. [Figure 2] This figure shows the relationship between the lattice constant of the crystal in the protective film and the durability of the protective film against plasma. [Figure 3] This figure shows the relationship between the lattice constant of the crystal in the protective film and the durability of the protective film against plasma. [Figure 4] This table shows a list of film formation conditions and other factors used when forming a protective film. [Figure 5] This is a diagram illustrating the surface shape of the protective film. [Figure 6] This is a diagram illustrating the porosity of the protective film. [Modes for carrying out the invention]

[0010] 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.

[0011] The structural member 10 according to this embodiment is configured as a member for a semiconductor manufacturing apparatus such as a plasma etching apparatus. Specifically, the structural member 10 is a member used as the inner wall of a processing chamber included in a semiconductor manufacturing apparatus. Note that the use of such a structural member 10 is merely an example. The structural member 10 may be a member disposed inside a processing chamber included in a semiconductor manufacturing apparatus, such as a focus ring.

[0012] As shown in FIG. 1, the structural member 10 includes a base material 100 and a protective film 200. In a plasma etching apparatus or the like, the surface 210 of the protective film 200 is exposed toward the space inside the processing chamber. The protective film 200 is provided for the purpose of protecting the surface 110 of the base material 100 from plasma.

[0013] The base material 100 is a member that generally occupies the entire structural member 10. In this embodiment, the base material 100 is a ceramic sintered body containing high-purity aluminum oxide (Al2O3), but it may be a different type of ceramics or a member other than ceramics (for example, a metal member). Further, the surface 110 of the base material 100 is a flat surface in this embodiment, but it may be a curved surface or the like. Also, a slope may be provided on a part of the surface 110.

[0014] As described above, the protective film 200 is a film formed to protect the base material 100 from plasma. The protective film 200 is formed so as to cover the entire surface 110 of the base material 100. The protective film 200 is formed of a material containing ytterbium oxide (Yb2O3) as a main component. Specifically, the protective film 200 contains crystals having ytterbium oxide (Yb2O3) as a main component, and the crystals occupy most of the protective film 200. The ratio of the number of ytterbium (Yb) atoms and the number of oxygen (O) atoms contained in the protective film 200 may be different from the above. The protective film 200 of this embodiment is a film formed using the aerosol deposition method, but it may be a film formed using another film formation method.

[0015] As used herein, the "main component" refers to the compound most contained in the object (here, the protective film 200). Specifically, the "main component" refers to a compound that, when subjected to quantitative analysis or semi-quantitative analysis using X-ray diffraction (XRD) on the object, is confirmed to be relatively more contained in terms of volume ratio or mass ratio than any other compound contained in the object.

[0016] In the protective film 200 of the present embodiment, the proportion occupied by the main component (ytterbium oxide) is greater than 50% in terms of volume ratio or mass ratio. This proportion may be greater than 70%, may be greater than 90%, or may be 100%. Further, in the protective film 200, the proportion occupied by the crystal having ytterbium oxide as the main component may be greater than 50% in terms of volume ratio or mass ratio, may be greater than 70%, may be greater than 90%, or may be 100%.

[0017] The thickness of the protective film 200 is appropriately set according to the length of the period for which durability is required, etc. In the present embodiment, the thickness of the protective film 200 is 15 μm or less. The thickness of the protective film 200 may be 1 μm or more.

[0018] The inventors of the present invention decided to use ytterbium oxide as the material of the protective film 200 as in the present embodiment, and have been proceeding with studies on further enhancing the durability of the material against plasma. As a result, it has been confirmed that there is a correlation between the lattice constant of the protective film 200 containing a crystal having ytterbium oxide as the main component and the durability of the protective film 200 against plasma.

[0019] Generally, the crystal of ytterbium oxide is a cubic crystal, with a = b = c and α = β = γ = 90°. According to the ICDD card reference code: 01-077-0458, the value of a (= b = c) in the crystal of ytterbium oxide is usually 10.522×10 -10 m and is known.

[0020] In the following explanation, "lattice constant of protective film 200" refers to the interatomic distance (a, b, or c) of the crystal contained in protective film 200 and whose main component is ytterbium oxide.

[0021] The lattice constant of the protective film 200 was measured using the following method. First, X-ray diffraction (XRD) was performed on the protective film 200 formed on the substrate 100 using an out-of-plane θ-2θ scan. From the obtained peak intensity distribution, the first peak appearing near the diffraction angle 2θ = 29.38°, the second peak appearing near the diffraction angle 2θ = 34.05°, and the third peak appearing near the diffraction angle 2θ = 48.93° were extracted, and the lattice constant corresponding to each peak was calculated individually. Subsequently, the average value of each lattice constant was calculated, and the obtained value was calculated as the lattice constant of the protective film 200. For other specific test methods and methods for calculating lattice constants, methods specified in JIS K0131 were used.

[0022] Furthermore, the peak attributed to Miller index (hkl) = (222) is generally the peak at the diffraction angle 2θ = 29.38°, but it shifts by 0.1 to 0.6° depending on the crystal structure of protective film 200. Therefore, the first peak mentioned above is a peak that is highly likely to be attributed to Miller index (hkl) = (222).

[0023] Furthermore, the peak attributed to Miller index (hkl) = (400) is generally the peak at the diffraction angle 2θ = 34.05°, but it shifts by 0.1 to 0.6° depending on the crystal structure of the protective film 200. Therefore, the second peak mentioned above is a peak that is highly likely to be attributed to Miller index (hkl) = (400).

[0024] Similarly, the peak attributed to Miller index (hkl) = (440) is generally the peak at diffraction angle 2θ = 48.93°, but it shifts by 0.1 to 0.6° depending on the crystal structure of protective film 200. Therefore, the third peak mentioned above is a peak that is highly likely to be attributed to Miller index (hkl) = (440).

[0025] The inventors prepared multiple samples of structural members 10 with different deposition conditions for the protective film 200, and then performed measurements of the lattice constant and evaluation of the plasma durability for each protective film 200. To evaluate the plasma durability of the protective film 200, the surface 210 of each protective film 200 was exposed to a plasma atmosphere using an inductively coupled reactive ion etching (ICP-RIE) apparatus (not shown). Two conditions were used for exposing the surface 210 to the plasma atmosphere, as described below.

[0026] Under the first condition, a 4-inch silicon wafer was held by electrostatic chuck within the chamber of an inductively coupled reactive ion etching apparatus. A sample of the structural member 10 to be evaluated was placed on the silicon wafer. Subsequently, plasma was generated in the chamber to expose the surface 210 of the protective film 200 to a plasma atmosphere. SF6 was used as the process gas and supplied to the chamber at a flow rate of 100 sccm. The pressure inside the chamber was adjusted to 0.5 Pa. The exposure time was 30 minutes. The power output was set to 1500W for the ICP coil output and 750W for the bias output. The test in which the surface 210 of the protective film 200 is exposed to a plasma atmosphere under the first condition described above will also be referred to as the "first standard plasma test" below. In the first standard plasma test, as described above, the bias output was set to 750W, causing the plasma to be drawn towards the protective film 200 and subjected to etching of the protective film 200.

[0027] Under the second condition, a 4-inch silicon wafer was held by electrostatic chuck within the chamber of an inductively coupled reactive ion etching apparatus. A sample of the structural component 10 to be evaluated was placed on the silicon wafer. Subsequently, plasma was generated in the chamber to expose the surface 210 of the protective film 200 to a plasma atmosphere. SF6 was used as the process gas and supplied to the chamber at a flow rate of 100 sccm. The pressure inside the chamber was adjusted to 0.5 Pa. The exposure time was 60 minutes. The power output was set to 1500W for the ICP coil output and the bias output was turned OFF (i.e., 0W). The test in which the surface 210 of the protective film 200 is exposed to a plasma atmosphere under the second condition described above will also be referred to as the "second standard plasma test" below. In the second standard plasma test, as described above, the bias output was turned OFF, so the plasma was not drawn towards the protective film 200 and was hardly used for etching the protective film 200. The surface 210 of the protective film 200 is simply exposed to a non-directional plasma.

[0028] Figure 2 shows the results of the first standard plasma test performed on each of the multiple structural members 10. The horizontal axis of the graph in Figure 2 represents the lattice constant of the protective film 200 for each sample in units of "Å" (i.e., 10⁻¹⁰ Å). -10 It is expressed in units of m. The method for measuring the lattice constant is as described above.

[0029] The vertical axis of the graph in Figure 2 represents the etching rate in the first standard plasma test, i.e., the depth to which the protective film 200 is etched per unit time, expressed in units of "μm / h". The higher the durability of the protective film 200 against the plasma, the lower its etching rate. The etching rate can be used as one indicator of the durability of the protective film 200 against the plasma.

[0030] Figure 2 shows the etching rate values, along with the error range, measured after the first standard plasma test for four structural member 10 samples with different lattice constants in the protective film 200.

[0031] As is clear from Figure 2, the larger the lattice constant of the protective film 200, the smaller the etching rate of the protective film 200 generally becomes. To the right of the dotted line shown in Figure 2, i.e., when the lattice constant is 10.530 × 10⁻¹⁰ -10 For protective film 200 with a lattice constant of m or more, it was confirmed that the etching rate was sufficiently low and that it had sufficient durability against plasma. The lattice constant of protective film 200 is 10.650 × 10⁻⁶. -10 It is also acceptable if it is less than or equal to m.

[0032] Figure 3 shows the results of the second standard plasma test performed on each of the multiple structural members 10. The horizontal axis of the graph in Figure 3 is the same as the horizontal axis in Figure 2, representing the lattice constant of the protective film 200 of each sample in units of "Å" (i.e., 10 -10 This is expressed in units of m. Furthermore, each sample prepared for the second standard plasma test was prepared using the same method as each sample prepared for the first standard plasma test described above. Therefore, the lattice constant values ​​of each sample shown in Figure 3 are the same as the lattice constant values ​​of each sample shown in Figure 2.

[0033] The vertical axis of the graph in Figure 3 represents the fluorination amount of protective film 200 after the second standard plasma test. "Fluorination amount" is an indicator of how much fluorine atoms, which are part of the plasma, have penetrated into the protective film 200. The specific method for calculating the fluorination amount is as follows.

[0034] First, while sputtering the surface 210 of the protective film 200 that had undergone the second standard plasma test using argon, the amount of fluorine atoms present on the surface 210 was continuously measured using X-ray photoelectron spectroscopy (XPS). The measurement was carried out over 145 seconds. At that time, the ratio (unit: %) occupied by the measured value of argon overall was calculated at each moment, and the integrated value of the obtained values was calculated as the "fluorination amount" of the sample. The higher the durability of the protective film 200 against plasma, the smaller the value of the fluorination amount calculated as described above. The fluorination amount can be used as one of the indicators showing the durability of the protective film 200 against plasma, similar to the etching rate described above.

[0035] As is clear from looking at FIG. 3, as the value of the lattice constant of the protective film 200 increases, the fluorination amount of the protective film 200 generally decreases. For the protective film 200 on the right side of the dotted line shown in FIG. 3, that is, the lattice constant is 10.530×10 -10 m or more, it was confirmed that the fluorination amount was sufficiently small and that it had sufficient durability against plasma. The lattice constant of the protective film 200 may be 10.650×10 -10 m or less.

[0036] The manufacturing method and the like of each sample used in the above measurement will be described while referring to FIG. 4. The sample shown as "No. 1" in the figure is a sample created under conditions such that the lattice constant of the protective film 200 is 10.465×10 -10 m. "No. 2" is a sample created under conditions such that the lattice constant of the protective film 200 is 10.556×10 -10 m, "No. 3" is a sample created under conditions such that the lattice constant of the protective film 200 is 10.537×10 -10 m, and "No. 4" is a sample created under conditions such that the lattice constant of the protective film 200 is 10.532×10 -10 m.

[0037] The protective films 200 for samples No. 1 to 4 were all deposited using the aerosol deposition method. 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 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 bond together, they gradually accumulate to form the protective film 200. Figure 4 shows the type of "gas" used during the deposition of each sample, and the flow rate at which the gas was sprayed from the nozzle.

[0038] The "fine particles" used in the above study were Yb2O3 powder. The average particle size of this powder was 3.0 μm, and the median diameter was 2.4 μm.

[0039] As shown in Figure 4, each of the samples from No. 1 to 4 differs from the others in terms of the deposition conditions (specifically, the gas flow rate) for the protective film 200, and as a result, the lattice constants of the protective film 200 also differ from each other.

[0040] Samples No. 1 through 4 were each prepared in pairs. One sample underwent the first standard plasma test, yielding the results shown in Figure 2. The other sample underwent the second standard plasma test, yielding the results shown in Figure 3.

[0041] The inventors measured the arithmetic mean height (Sa) of surface 210 for each sample No. 1 to 4 before and after performing the first standard plasma test. In the table in Figure 4, the "Before Etching" column shows the arithmetic mean height of surface 210 measured before the first standard plasma test, in units of μm. The "After Etching" column shows the arithmetic mean height of surface 210 measured after the first standard plasma test, in units of μm. The "ΔSa" column shows the difference between the two arithmetic mean heights. That is, it shows the change in the arithmetic mean height of surface 210 due to the first standard plasma test, in units of μm. The method for measuring the arithmetic mean height was the method specified in ISO 25178.

[0042] Sample No. 1, i.e., protective film 200, has a lattice constant of 10.530 × 10⁻¹⁰. -10 In samples where the value is less than m, the arithmetic mean height of the surface 210 of the protective film 200 after the first standard plasma test exceeds 0.1 μm. On the other hand, in samples No. 2 to 4, i.e., the lattice constant of the protective film 200 is 10.530 × 10⁻¹⁰. -10 In samples where the value was m or greater, the arithmetic mean height of the surface 210 of the protective film 200 after the first standard plasma test was all below 0.1 μm. The lattice constant of the protective film 200 is 10.650 × 10⁻¹⁰. -10 It may be less than or equal to m. The arithmetic mean height of the surface 210 of the protective film 200 after the first standard plasma test may be 0.005 μm or more.

[0043] The inventors observed the surface 210 of each sample No. 1 to 4 using a scanning electron microscope (SEM) before and after performing the first standard plasma test. Figure 5 shows the images obtained from this observation. Each image is a so-called "secondary electron image" and was taken under an accelerating voltage of 3 kV. The magnification of the image was 5000x. The "Before Etching" column in Figure 5 shows the image obtained from observation before the first standard plasma test. The "After Etching" column shows the image obtained from observation after the first standard plasma test.

[0044] The inventors also measured the porosity of the protective film 200. Here, "porosity" refers to the percentage of the cross-section of the protective film 200 when it is cut along a plane perpendicular to the surface 210, where the cross-section is occupied by voids.

[0045] The method for measuring porosity is as follows. First, the above cross-section was observed using a scanning electron microscope (SEM) to obtain a secondary electron image. The acceleration voltage was set to 3kV and the magnification was set to 30,000x. Figure 6(A) shows an example of an image obtained using the above procedure. The sample used for measurement is sample No. 2 in the table in Figure 4.

[0046] Next, the porosity of the protective film 200 was calculated by analyzing the images obtained as described above. The image analysis was performed using the OpenCV module for the Python language. First, the captured images were cropped to include only the cross-section of the protective film 200. Specifically, the part of the image in Figure 6(A) outside the dotted line DL was cropped and excluded.

[0047] Figure 6(B) shows the image after the above cropping process has been performed. The entire image is a cross-section of the protective film 200. The multiple black dots visible in the image of Figure 6(B) (one of which is indicated by arrow AR) are cross-sections of voids contained in the protective film 200.

[0048] After cropping, the image in Figure 6(B) was binarized so that the cross-sections of the voids were black and the other cross-sections were white. The binarization was performed using the "Variable Threshold Binarization Method" described in the Journal of the Institute of Image Electronics Engineers of Japan, Vol. 36 (2007), No. 3 (pp. 204-209). Subsequently, noisy areas were removed by dilation processing, etc., to obtain the binary image shown in Figure 6(C). In this figure, the black dots labeled "250" correspond to the cross-sections of the voids contained in the protective film 200.

[0049] The ratio of black pixels to the total number of pixels in the image in Figure 6(C) was calculated as the porosity of the protective film 200. In the example shown in Figure 6(C), the total number of pixels in the image was 1,100,800, and the number of black pixels was 35,180. Therefore, the porosity was calculated to be approximately 3.19%. The lattice constant of the protective film 200 is 10.530 × 10⁻¹⁰. -10 The inventors have confirmed that the durability of the protective film 200 against plasma is further enhanced if the lattice constant is 10.650 × 10⁻¹⁰ or greater and the porosity of the protective film 200 is 3.2% or less. -10 It may be less than m. The porosity of the protective film 200 may be 0.01% or more.

[0050] Furthermore, the inventors have confirmed that forming the protective film 200 such that the average crystallite size is 50 nm or less further increases the durability of the protective film 200 against plasma. "Average crystallite size" refers to a value obtained, for example, by performing a circular approximation on each of the multiple (at least 15) crystallites appearing on the surface 210 of the protective film 200 and taking the average value of the diameter of each circle. To calculate the average crystallite size of the protective film 200, the surface 210 of the protective film 200 is photographed using a transmission electron microscope (TEM), and the average crystallite size is calculated based on the obtained image. In this case, it is preferable to use a magnification of 400,000 times or more. The average crystallite size of the protective film 200 may be 5 nm or more.

[0051] The durability of the protective film 200 can be further improved by setting the average crystallite size of the protective film 200 to more preferably 30 nm or less, and even more preferably 15 nm or less.

[0052] 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]

[0053] 10: Structural members 100: Base material 110: Surface 200: Protective film

Claims

1. Substrate and The substrate comprises a protective film covering the surface of the substrate, The protective film contains crystals mainly composed of ytterbium oxide. The lattice constant of the aforementioned crystal is 10.530 × 10 －１０ A structural member characterized by being m or larger.

2. The structural member according to claim 1, characterized in that the protective film is a film formed using the aerosol deposition method.

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

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

5. The structural member according to claim 1, characterized in that the arithmetic mean height of the surface of the protective film after the first standard plasma test is less than 0.1 μm.

6. The structural member according to claim 1, characterized in that the porosity of the protective film is 3.2% or less.

7. The structural member according to claim 1, characterized in that it is configured as a component for semiconductor manufacturing equipment.

Images