Structural members

Abstract

To provide a structural member that has 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 mainly contains ytterbium oxide, and the indentation hardness of the protective film 200 is greater than 8.6 GPa.

Description

Technical Field

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

Background Art

[0002] Members constituting a semiconductor manufacturing apparatus, such as members of the inner wall of a chamber, etc., are required to have durability against plasma. For this reason, as such members, it has generally become common to use a structural member in which a protective film is formed on the surface of a base material, as described in Patent Document 1 below, for example. As the protective film, a material such as yttria is often used.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present inventors have been studying the use of ytterbium oxide as a material for the protective film and further enhancing the durability of the protective film against plasma.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide a structural member having sufficient durability against plasma.

Means for Solving the Problems

[0006] In order to solve the above problems, the structural member according to the present invention includes a base material and a protective film covering the surface of the base material. The protective film contains ytterbium oxide as a main component, and the indentation hardness of the protective film is greater than 8.6 GPa.

[0007] Experiments conducted by the inventors confirmed a correlation between the indentation hardness of a protective film mainly composed of ytterbium oxide and the durability of the protective film against plasma. Furthermore, it was confirmed that the durability of the protective film against plasma can be sufficiently enhanced by forming it such that its indentation hardness is greater than 8.6 GPa. [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 indentation hardness of the protective film and the durability of the protective film against plasma. [Figure 3] This figure shows the relationship between the indentation hardness of 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 component for semiconductor manufacturing equipment, such as a plasma etching apparatus. Specifically, the structural member 10 is a component used as the inner wall of a processing chamber in semiconductor manufacturing equipment. However, this application of the structural member 10 is merely an example. The structural member 10 may also be a component placed inside the processing chamber of semiconductor manufacturing equipment, such as a focus ring.

[0012] 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 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 component that occupies approximately the entirety of the 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 ceramic, or a component other than ceramic (for example, a metal component). Also, in this embodiment, the surface 110 of the base material 100 is a flat surface, but it may be a curved surface or the like. Furthermore, a slope may be provided on a part of the surface 110.

[0014] As mentioned above, 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 protective film 200 is made of a material mainly composed of ytterbium oxide (Yb2O3). The ratio of the number of ytterbium (Yb) atoms and oxygen (O) atoms in the protective film 200 may differ from that described above. In this embodiment, the protective film 200 is a film formed using the aerosol deposition method, but it may also be a film formed using other film formation methods.

[0015] In this specification, the "main component" refers to the compound that is most contained in the object (here, the protective film 200). Specifically, the "main component" refers to a compound that, when quantitative analysis or semi-quantitative analysis using X-ray diffraction (XRD) is performed 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 this 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%.

[0017] The thickness of the protective film 200 is appropriately set according to the length of the period for which durability needs to be maintained, etc. In this 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 decided to use ytterbium oxide as the material for the protective film 200 as in this embodiment, and have been proceeding with studies on further enhancing the durability of the material against plasma. As a result, it was confirmed that there is a correlation between the indentation hardness of the protective film 200 containing ytterbium oxide as the main component and the durability of the protective film 200 against plasma.

[0019] The indentation hardness of the protective film 200 was measured by performing a nanoindentation test on the surface 210 of the protective film 200 formed on the substrate 100. A Berkovich indenter was used, and the indentation depth was fixed at 200 nm. The indentation hardness (indentation hardness) was measured at multiple locations on the surface 210. Each measurement location was a part of the surface 210 that was free of scratches and dents. If the surface 210 is polished and smoothed prior to the measurement of indentation hardness, a more accurate measurement of indentation hardness can be obtained. The number of measurement locations was set to at least 10, and the average value of the indentation hardness measured at each location was calculated as the indentation hardness of the protective film 200. For other specific test methods, analysis methods, procedures for verifying the performance of the test equipment, and conditions required for standard reference samples, the methods specified in ISO 14577 were used.

[0020] The inventors prepared multiple samples of structural members 10 with different deposition conditions for the protective film 200, and then performed indentation hardness measurements and plasma durability evaluations 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.

[0021] Under the first condition, a 4-inch silicon wafer was adsorbed and held by an electrostatic chuck inside 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. Then, by generating plasma inside the chamber, the surface 210 of the protective film 200 was exposed to the plasma atmosphere. SF6 was used as the process gas, and the gas was supplied into 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 magnitude of the power output was set such that the coil output for ICP was 1500 W and the bias output was 750 W. The test of exposing the surface 210 of the protective film 200 to the plasma atmosphere under the first condition as described above is hereinafter also referred to as the "first standard plasma test". In the first standard plasma test, by setting the bias output to 750 W as described above, the plasma is drawn toward the protective film 200 and used for etching the protective film 200.

[0022] Under the second condition, a 4-inch silicon wafer was adsorbed and held by an electrostatic chuck inside 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. Then, by generating plasma inside the chamber, the surface 210 of the protective film 200 was exposed to the plasma atmosphere. SF6 was used as the process gas, and the gas was supplied into 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 magnitude of the power output was set such that the coil output for ICP was 1500 W and the bias output was OFF (that is, 0 W). The test of exposing the surface 210 of the protective film 200 to the plasma atmosphere under the second condition as described above is hereinafter also referred to as the "second standard plasma test". In the second standard plasma test, by setting the bias output to OFF as described above, the plasma is not drawn toward the protective film 200 and is hardly used for etching the protective film 200. The surface 210 of the protective film 200 is simply exposed to the non-directional plasma.

[0023] 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 indentation hardness of the surface 210 of each sample in units of "GPa". The method for measuring indentation hardness is as described above.

[0024] 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.

[0025] 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 that differ in the indentation hardness of the protective film 200.

[0026] As is clear from Figure 2, the etching rate of the protective film 200 generally decreases as the indentation hardness value of the protective film 200 increases. For protective films 200 to the right of the dotted line shown in Figure 2, i.e., with an indentation hardness greater than 8.6 GPa, the etching rate is sufficiently low, confirming sufficient durability against plasma. More preferably, it has been confirmed that the etching rate decreases even further when the indentation hardness of the protective film 200 exceeds 9.8 GPa. The indentation hardness of the protective film 200 may be 20 GPa or less.

[0027] 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, like the horizontal axis in Figure 2, represents the indentation hardness of the surface 210 of each sample in units of "GPa". The samples prepared for the second standard plasma test were prepared using the same method as the samples prepared for the first standard plasma test. Therefore, the indentation hardness values ​​of each sample shown in Figure 3 are the same as the indentation hardness values ​​of each sample shown in Figure 2.

[0028] 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.

[0029] First, the surface 210 of the protective film 200, which had undergone the second standard plasma test, was sputtered with argon, and the amount of fluorine atoms present on the surface 210 was continuously measured using X-ray photoelectron spectroscopy (XPS). The measurement was performed over 145 seconds. At each time point, the percentage (in units: %) of the argon measurement was calculated, and the cumulative 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 fluorination amount calculated as described above. The fluorination amount, like the etching rate mentioned earlier, can be used as one of the indicators of the durability of the protective film 200 against plasma.

[0030] As is clear from Figure 3, the amount of fluoride in the protective film 200 generally decreases as the indentation hardness value of the protective film 200 increases. For protective films 200 to the right of the dotted line shown in Figure 3, i.e., with an indentation hardness greater than 8.6 GPa, it was confirmed that the amount of fluoride is sufficiently small and that they have sufficient durability against plasma. More preferably, it has been confirmed that the amount of fluoride decreases even further when the indentation hardness of the protective film 200 exceeds 9.8 GPa. The indentation hardness of the protective film 200 may be 20 GPa or less.

[0031] The manufacturing methods for each sample used in the above measurements will be explained with reference to Figure 4. The sample shown as "No. 1" in the figure is a sample prepared under conditions that result in an indentation hardness of 4.6 GPa for the protective film 200. "No. 2" is a sample prepared under conditions that result in an indentation hardness of 10.0 GPa for the protective film 200, "No. 3" is a sample prepared under conditions that result in an indentation hardness of 9.9 GPa for the protective film 200, and "No. 4" is a sample prepared under conditions that result in an indentation hardness of 10.1 GPa for the protective film 200.

[0032] 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.

[0033] 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.

[0034] 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 indentation hardness of the protective film 200 also differs from one another.

[0035] 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.

[0036] 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.

[0037] In sample No. 1, i.e., the sample in which the indentation hardness of the protective film 200 is 8.6 GPa or less, the arithmetic mean height of the surface 210 of the protective film 200 after the first standard plasma test is greater than 0.1 μm. On the other hand, in samples No. 2 to 4, i.e., the samples in which the indentation hardness of the protective film 200 is greater than 8.6 GPa, the arithmetic mean height of the surface 210 of the protective film 200 after the first standard plasma test is all less than 0.1 μm. The indentation hardness of the protective film 200 may be 20 GPa or less. 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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 inventors have confirmed that the durability of the protective film 200 against plasma is further increased if the indentation hardness of the protective film 200 is greater than 8.6 GPa and the porosity of the protective film 200 is 3.2% or less. The indentation hardness of the protective film 200 may be 20 GPa or less. The porosity of the protective film 200 may be 0.01% or more.

[0045] 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.

[0046] 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.

[0047] 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]

[0048] 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 ytterbium oxide as its main component, A structural member characterized in that the indentation hardness of the protective film is greater than 8.6 GPa.

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 indentation hardness of the protective film is greater than 9.8 GPa.

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

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

6. 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.

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

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

Images