Structural component

Abstract

Provided is a structural member having sufficient durability to plasma. Specifically, a structural member (10) is provided with a base material (100) and a protective film (200) that covers the surface (110) of the base material (100). The protective film (200) contains a crystal having a lanthanum zirconium oxide as a main component, and the crystal has a lattice constant of 10.830 * 10-10 m or more.

Description

Technical Field

[0001] This invention relates to a structural component. Background Technology

[0002] Components constituting semiconductor manufacturing apparatuses, such as the inner walls of chambers, require resistance to plasma. Therefore, as such components, for example as described in Patent Document 1 below, structural components with a protective film formed on the surface of a substrate are typically used. As the protective film, oxide ceramics such as yttrium oxide are often used, for example.

[0003] Patent documents Patent Document 1: Japanese Patent Publication No. 2019-507962 Summary of the Invention

[0004] The inventors have investigated the use of lanthanum zirconium oxide as a material for a protective film and how to further improve the durability of this protective film against plasma.

[0005] The present invention is based on the following problem: the technical problem to be solved is to provide a structural component with sufficient durability against plasma.

[0006] To address the aforementioned issues, the structural component of this invention comprises a substrate and a protective film covering the surface of the substrate. The protective film contains crystals primarily composed of lanthanum zirconium oxide, with a lattice constant of 10.830 × 10⁻⁶. -10 m or more.

[0007] According to experiments conducted by the inventors, a correlation was confirmed between the lattice constant of a protective film containing crystals primarily composed of lanthanum zirconium oxide and the plasma durability of the protective film. Furthermore, it was confirmed that if the lattice constant of the crystals in the protective film is pre-formed to 10.830 × 10⁻⁶, the plasma durability of the protective film will improve. -10 If the thickness is above m, the durability of the protective film against plasma can be significantly improved.

[0008] According to the present invention, a structural component with sufficient durability against plasma can be provided. Attached Figure Description

[0009] Figure 1 It is a diagram that represents the cross-section of a structural component in a stylized way. Figure 2 This is a graph showing the relationship between the lattice constant of the crystals in the protective film and the durability of the protective film against plasma. Figure 3 This is a graph showing the relationship between the lattice constant of the crystals in the protective film and the durability of the protective film against plasma. Figure 4It is a table showing the film-forming conditions, etc., when a protective film is formed. Figure 5 It is a diagram used to illustrate the surface shape of the protective film. Figure 6 This is a graph used to illustrate the porosity of the protective film. Symbol Explanation 10 - Structural component; 100 - Substrate; 110 - Surface; 200 - Protective film. Detailed Implementation

[0010] The present embodiment will now be described with reference to the accompanying drawings. To facilitate understanding, the same reference numerals are used as much as possible to represent the same constituent elements in the drawings, and repeated descriptions are omitted.

[0011] The structural component 10 involved in this embodiment is configured, for example, as a component for a semiconductor manufacturing apparatus such as a plasma etching apparatus. Specifically, the structural component 10 is used as the inner wall of a processing chamber provided in a semiconductor manufacturing apparatus. Furthermore, the application of such a structural component 10 is merely one example. The structural component 10 may also be, for example, a component such as a focusing ring disposed inside the processing chamber provided in a semiconductor manufacturing apparatus.

[0012] like Figure 1 As shown, structural component 10 includes a substrate 100 and a protective film 200. In plasma etching apparatuses, the surface 210 of the protective film 200 is exposed to the space within the processing chamber. The purpose of providing the protective film 200 is to protect the surface 110 of the substrate 100 from the effects of plasma.

[0013] The substrate 100 is a component that occupies approximately the entirety of the structural component 10. In this embodiment, the substrate 100 is a sintered ceramic body containing high-purity alumina (Al2O3), but it may also be a different type of ceramic, or a component other than ceramic (e.g., a metal component). Furthermore, although the surface 110 of the substrate 100 is flat in this embodiment, it may also be curved or the like. Additionally, a slope may be provided on a portion of the surface 110.

[0014] As previously described, the protective film 200 is a film formed to protect the substrate 100 from the effects of plasma. The protective film 200 is formed to cover the entire surface 110 of the substrate 100. The protective film 200 is formed from a material comprising lanthanum zirconium oxide as a main component. Specifically, the protective film 200 comprises crystals with lanthanum zirconium oxide as the main component, which constitute the majority of the protective film 200.

[0015] Specifically, the aforementioned lanthanum zirconium oxide refers to La₂Zr₂O₇. The ratio of the number of lanthanum (La) atoms, zirconium (Zr) atoms, and oxygen (O) atoms in the protective film 200 may also differ from the above. Although the protective film 200 of this embodiment is formed using aerosol deposition, it may also be formed using other film-forming methods.

[0016] In this specification, "principal component" refers to the compound most abundant in the object (here, protective film 200). Specifically, "principal component" refers to the compound that, when quantitative or quasi-quantitatively analyzed using X-ray diffraction (XRD) of the object, is found to be present in greater quantities than any other compound contained in the object in volume or mass ratio.

[0017] In the protective film 200 of this embodiment, the proportion of the main component (lanthanum zirconium oxide) is greater than 50% in volume or mass. This proportion can be greater than 70%, greater than 90%, or 100%. Furthermore, in the protective film 200, the proportion of crystals with lanthanum zirconium oxide as the main component can be greater than 50%, greater than 70%, greater than 90%, or 100% in volume or mass.

[0018] The thickness of the protective film 200 can be appropriately set according to the length of the period required to maintain durability. In this embodiment, the thickness of the protective film 200 is 15 μm or less.

[0019] Based on the use of lanthanum zirconium oxide as the material for the protective film 200 in this embodiment, the inventors have conducted research to further improve the plasma durability of this material. As a result, a correlation was confirmed between the lattice constant of the protective film 200, which comprises crystals mainly composed of lanthanum zirconium oxide, and the plasma durability of the protective film 200.

[0020] Typically, lanthanum zirconium oxide crystals are cubic, with a=b=c and α=β=γ=90°. According to ICDD reference code 01-090-3310, the value of a (=b=c) in lanthanum zirconium oxide crystals is usually 10.7460 × 10⁻⁶. -10 m.

[0021] In the following description, "lattice constant of protective film 200" refers to the interatomic distance (a, b, or c) of the crystal contained in protective film 200 and mainly composed of lanthanum zirconium oxide.

[0022] The lattice constant of the protective film 200 can be determined using the following method. First, X-ray diffraction (XRD) analysis 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 a diffraction angle of 2θ = 28.8°, the second peak appearing near a diffraction angle of 2θ = 33.3°, and the third peak appearing near a diffraction angle of 2θ = 47.8° were extracted, and the lattice constant corresponding to each peak was calculated individually. Then, the average value of each lattice constant was calculated, and this value was used as the lattice constant of the protective film 200. For other specific experimental methods and methods for calculating the lattice constant, the methods specified in Japanese Industrial Standard JIS K0131 were used.

[0023] Furthermore, the peak attributed to the Miller index (hkl) = (222) is usually the peak at a diffraction angle of 2θ = 28.8°, but depending on the crystal structure of the protective film 200, it will shift within the range of 0.1 to 0.6°. Therefore, the first peak mentioned above is the peak most likely to be attributed to the Miller index (hkl) = (222).

[0024] Furthermore, the peak attributed to the Miller index (hkl) = (400) is usually the peak at a diffraction angle of 2θ = 33.3°, but depending on the crystal structure of the protective film 200, it may shift within the range of 0.1 to 0.6°. Therefore, the second peak mentioned above is the peak most likely attributed to the Miller index (hkl) = (400).

[0025] Similarly, the peak attributed to the Miller index (hkl) = (440) is usually the peak at a diffraction angle of 2θ = 47.8°, but depending on the crystal structure of the protective film 200, it will shift within the range of 0.1 to 0.6°. Therefore, the third peak mentioned above is the peak most likely to be attributed to the Miller index (hkl) = (440).

[0026] The inventors fabricated multiple samples of structural components 10 with different film formation conditions for the protective film 200, and then measured the lattice constant and evaluated the plasma durability of each protective film 200. Furthermore, in evaluating the plasma durability of the protective film 200, an inductively coupled reactive ion etching (ICP-RIE) apparatus (not shown) was used, and the surface 210 of each protective film 200 was exposed to a plasma atmosphere. The following two conditions were used as conditions for exposing the surface 210 to the plasma atmosphere.

[0027] In the first condition, a 4-inch silicon wafer is held in place by an electrostatic chuck within the chamber of an inductively coupled reactive ion etching apparatus. The sample of the evaluation object, namely structural component 10, is placed on this silicon wafer. Subsequently, the surface 210 of the protective film 200 is exposed to a plasma atmosphere by generating plasma within the chamber. SF6 is used as the process gas and is supplied to the chamber at a flow rate of 100 sccm. The pressure within the chamber is adjusted to 0.5 Pa. The exposure time is 30 minutes. The power output is set to 1500 W for the ICP coil and 750 W for the bias output. Hereinafter, 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". In the first standard plasma test, as described above, plasma is introduced toward the protective film 200 by setting the bias output to 750 W and is used for etching the protective film 200.

[0028] Under the second condition, a 4-inch silicon wafer is held in place by an electrostatic chuck within the chamber of an inductively coupled reactive ion etching apparatus. The sample of the evaluation object, namely structural component 10, is placed on this silicon wafer. Subsequently, the surface 210 of the protective film 200 is exposed to a plasma atmosphere by generating plasma within the chamber. SF6 is used as the process gas and supplied to the chamber at a flow rate of 100 sccm. The pressure within the chamber is adjusted to 0.5 Pa. The exposure time is 60 minutes. The power output is set to 1500 W for the ICP coil and OFF (i.e., 0 W) for the bias output. Hereinafter, the test exposing the surface 210 of the protective film 200 to a plasma atmosphere under the second condition described above will also be referred to as the "Second Standard Plasma Test." In the Second Standard Plasma Test, as described above, by setting the bias output to OFF, the plasma is not introduced towards the protective film 200 and is hardly used for etching the protective film 200. The surface 210 of the protective film 200 is only exposed to non-directional plasma.

[0029] exist Figure 2 The results of the first standard plasma test performed on multiple structural components 10 are shown. Figure 2 The horizontal axis of the graph is in Å (i.e., 10 Å). -10 The lattice constant of the protective film 200 for each sample is expressed in m. The method for determining the lattice constant is as described above.

[0030] Figure 2The vertical axis of the graph represents the etching rate in the first standard plasma test, expressed in μm / h, which is the depth to which the protective film 200 is etched per unit time. The higher the plasma durability of the protective film 200, the lower its etching rate. The etching rate can be used as one of the indicators of the plasma durability of the protective film 200.

[0031] exist Figure 2 In the sample, for five structural components 10 that have different lattice constants in the protective film 200, the values ​​and error ranges of the etching rate determined by the first standard plasma test are shown.

[0032] observe Figure 2 It can be seen that the larger the lattice constant of the protective film 200, the smaller the etching rate of the protective film 200. For Figure 2 The part shown further to the right than the dashed line has a lattice constant of 10.830 × 10⁻⁶. -10 For the protective film 200 with a thickness of m or more, the etching rate is sufficiently reduced, thus confirming sufficient durability against plasma. It is known that if the lattice constant of the protective film 200 is made 10.850 × 10⁻⁶... -10 m or more, preferably 10.870 × 10 -10 For depths above m, the etching rate will decrease further.

[0033] exist Figure 3 The image shows the results of the aforementioned second standard plasma test performed on multiple structural components 10. (Compared to...) Figure 2 The horizontal axis is the same. Figure 3 The horizontal axis of the graph is in Å (i.e., 10 Å). -10 The lattice constant of the protective film 200 for each sample is represented by the unit m. Furthermore, the samples prepared for the second standard plasma test were prepared using the same method as those prepared for the first standard plasma test. Therefore, Figure 3 The values ​​of the lattice constants of each sample shown are... Figure 2 The lattice constant values ​​of all the samples shown are the same.

[0034] Figure 3 The vertical axis of the graph represents the fluorination level of the protective film 200 after the second standard plasma test. "Fluorination level" refers to the degree to which a portion of the plasma, i.e., fluorine atoms, penetrates into the interior of the protective film 200. The specific calculation method for fluorination level is as follows.

[0035] First, while sputtering the surface 210 of the protective film 200, which has undergone the second standard plasma test, with argon, the amount of fluorine atoms present on the surface 210 is continuously measured using X-ray photoelectron spectrometry (XPS). The measurement lasts for 145 seconds. At this point, the proportion (in %) of the measured value of argon at each time point is calculated, and the cumulative value obtained is calculated as the "fluorination amount" of the sample. The higher the plasma durability of the protective film 200, the lower the value of the fluorination amount calculated as described above. Similar to the etching rate mentioned above, the fluorination amount can be used as one of the indicators of the plasma durability of the protective film 200.

[0036] observe Figure 3 It can be seen that the larger the lattice constant of the protective film 200, the smaller the fluorination content of the protective film 200. For Figure 3 The part shown further to the right than the dashed line has a lattice constant of 10.830 × 10⁻⁶. -10 For the protective film 200 with a lattice constant of m or more, the fluorination amount is sufficiently reduced, thus confirming sufficient durability against plasma. It is known that if the lattice constant of the protective film 200 is made 10.850 × 10⁻⁶... -10 m or more, preferably 10.870 × 10 -10 For values ​​above m, the amount of fluorination will decrease further.

[0037] Reference Figure 4 The manufacturing methods of each sample used in the above measurements are explained. In this figure, the sample labeled "No.1" has a lattice constant of 10.823 × 10⁻⁶ for the protective film 200. -10 Sample No. 2 was prepared under conditions where the lattice constant of the protective film 200 was 10.816 × 10⁻⁶ m. -10 Sample No. 3 was prepared under conditions of m, with a lattice constant of 10.829 × 10⁻⁶ for the protective film 200. -10 Sample No. 4 was prepared under conditions of m, with a lattice constant of 10.860 × 10⁻⁶ for the protective film 200. -10 Sample No. 5 was prepared under conditions of m, with a lattice constant of 10.887 × 10⁻⁶ for the protective film 200. -10 Samples prepared under conditions of m.

[0038] The protective films 200 of samples No. 1 to 5 were all formed using aerosol deposition. As is well known, in aerosol deposition, the material of the protective film 200, i.e., microparticles, is dispersed into a gas to form an "aerosol," which is then sprayed from a nozzle toward surface 110 and impacted. On surface 110, due to the deformation and breakage caused by the impact on the microparticles, the microparticles gradually accumulate and combine with each other to form the protective film 200. Figure 4 The diagram shows the types of the aforementioned "gas" used in the film formation of each sample and the flow rate of the gas when it is injected from the nozzle.

[0039] The aforementioned "microparticles" were made of La2Zr2O7 powder. The average particle size of this powder was 2.3 μm, and the median particle size was 2.1 μm.

[0040] like Figure 4 As shown, the samples No.1 to No.5 have different film-forming conditions (specifically, the type and flow rate of the gas) for the protective film 200, and as a result, their lattice constants are also different.

[0041] Samples No. 1 through No. 5 were each prepared in pairs. One sample was subjected to the first standard plasma test, and the results were obtained. Figure 2 The results are shown. A second standard plasma test was performed on the other sample, and the results were... Figure 3 The results are shown.

[0042] Before and after conducting the first standard plasma test, the inventors measured the arithmetic mean height (Sa) of surface 210 of each of the samples No.1 to No.5. Figure 4 In the table, the arithmetic mean height of surface 210, measured before the implementation of the first standard plasma test, is shown in μm in the "Before Etching" column. The arithmetic mean height of surface 210, measured after the implementation of the first standard plasma test, is shown in μm in the "After Etching" column. The difference between the two arithmetic mean heights is shown in the "ΔSa" column. That is, the change in the arithmetic mean height of surface 210 caused by the implementation of the first standard plasma test is shown in μm. Furthermore, the method for measuring the arithmetic mean height uses the method specified in the international standard ISO 25178.

[0043] The lattice constants of samples No. 1 to No. 3, i.e., protective film 200, are less than 10.830 × 10⁻⁶. -10For each sample of size m, the arithmetic mean height of the surface 210 of the protective film 200 after the first standard plasma test was greater than 0.05 μm. On the other hand, the lattice constant of the protective film 200 in samples No. 4 to 5 was 10.830 × 10⁻⁶. -10 On samples with a diameter of m or more, the arithmetic mean height of the surface 210 of the protective film 200 after the first standard plasma test is less than 0.05 μm.

[0044] The inventors observed the surface 210 of samples No. 1 to No. 5 using a scanning electron microscope (SEM) before and after conducting the first standard plasma test. Figure 5 The image shown is the result of this observation. Each image is a so-called "secondary electron image," taken at an accelerating voltage of 3 kV. The magnification is 5000x. Figure 5 The "Before Etching" section shows images obtained through observation before the implementation of the first standard plasma test. The "After Etching" section shows images obtained through observation after the implementation of the first standard plasma test.

[0045] The inventors also measured the porosity of the protective film 200. The term "porosity" here refers to the percentage of the cross-section of the protective film 200 when it is cut along a surface perpendicular to surface 210, expressed as a percentage.

[0046] The porosity was determined as follows. First, the cross-section was observed using a scanning electron microscope (SEM) to obtain a secondary electron image. The accelerating voltage was 3 kV, and the magnification was 30,000x. Figure 6 (A) shows an example of an image obtained through the steps described above. Additionally, the sample to be measured is... Figure 4 Sample No. 4 in the table.

[0047] Next, the porosity of the protective film 200 is calculated by analyzing the image obtained as described above. Image analysis is performed using the OpenCV module for Python. First, the captured image is cropped to form an image containing only the cross-section of the protective film 200. Specifically, in Figure 6 In image (A), the portion that is further out than the dashed line DL is trimmed and excluded.

[0048] exist Figure 6 (B) shows an image after the aforementioned trimming process. The image as a whole is a cross-section of the protective film 200. Figure 6In the image (B), the multiple black dot-like portions (one of which is indicated by arrow AR) are cross-sections of the voids contained in the protective film 200.

[0049] After trimming, the sections with gaps are shown in black and the other sections in white. Figure 6 Image (B) is binarized. The binarization process is performed using the "dynamic thresholding binarization method" described in the Journal of the Chinese Society for Imaging and Electronics, Vol. 36 (2007), No. 3 (pp. 204-209). Subsequently, dilation and other methods are used to remove noise, resulting in... Figure 6 (C) shows a binary image. In this image, the black dot marked with the symbol "250" corresponds to the cross-section of the void contained in the protective film 200.

[0050] Calculate Figure 6 (C) The ratio of the number of black pixels to the total number of pixels in the image is used as the porosity of the protective film 200. Figure 6 In the example shown in (C), the total number of pixels in the image is 947,200, and the number of black pixels is 981. Therefore, the porosity is calculated to be approximately 0.10%. The inventors have confirmed that if the lattice constant of the protective film 200 is 10.830 × 10⁻⁶, the porosity will be approximately 0.10%. -10 If the diameter of the protective film 200 is greater than m and the porosity of the protective film 200 is less than 0.15%, then the durability of the protective film 200 against plasma will be further improved.

[0051] Furthermore, the inventors have confirmed that when the protective film 200 is formed with an average grain size of 50 nm or less, the plasma resistance of the protective film 200 is further improved. "Average grain size" refers to, for example, the average diameter of a plurality (at least 15) of grains appearing on the surface 210 of the protective film 200, approximated as circular. To calculate the average grain size of the protective film 200, the surface 210 of the protective film 200 can be imaged using a transmission electron microscope (TEM), and the average grain size can be calculated based on the obtained image. Preferably, the magnification is 400,000 times or more.

[0052] The average grain size of the protective film 200 is more preferably 30 nm or less, and even more preferably 15 nm or less, thereby further improving the durability of the protective film 200.

[0053] The above description of this embodiment refers to specific examples. However, this disclosure is not limited to these specific examples. As long as the features of this disclosure are present, products with appropriate design modifications to these specific examples by those skilled in the art are also included within the scope of this disclosure. The elements, configurations, conditions, shapes, etc., of the aforementioned specific examples are not limited to the illustrated contents and can be appropriately modified. As long as no technical contradiction arises, the elements of the aforementioned specific examples can be appropriately changed and combined.

Claims

1. A structural component comprising a substrate and a protective film covering the surface of the substrate, characterized in that, The protective film comprises crystals with lanthanum zirconium oxide as the main component. The lattice constant of the crystal is 10.830 × 10⁻⁶. -10 m or more.

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

3. The structural component according to claim 1, characterized in that, The lanthanum zirconium oxide is La2Zr2O7.

4. The structural component according to claim 1, characterized in that, The lattice constant of the crystal is 10.850 × 10⁻⁶. -10 m or more.

5. The structural component according to claim 1, characterized in that, The lattice constant of the crystal is 10.870 × 10⁻⁶. -10 m or more.

6. The structural component according to claim 1, characterized in that, The average grain size of the protective film is below 50 nm.

7. The structural component according to claim 1, characterized in that, The thickness of the protective film is less than 15 μm.

8. The structural component according to claim 1, characterized in that, The arithmetic mean height of the protective film surface after the first standard plasma test is less than 0.05 μm.

9. The structural component according to claim 1, characterized in that, The porosity of the protective film is less than 0.15%.

10. The structural component according to claim 1, characterized in that, Components used in semiconductor manufacturing equipment.

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