RF transmission member

Abstract

Provided is an RF transmission member that makes it possible to homogenize the concentration distribution of plasma that is supplied toward a substrate side. The RF transmission member 10 comprises a cylindrical body 100 and a protective film 200 that covers an inner surface 130 of the cylindrical body 100. A first opening 111 is formed at one end of the cylindrical body 100, and a second opening 121 that has an inner diameter larger than that of the first opening 111 is formed at the other end of the cylindrical body 100. The inner surface 130 of the cylindrical body 100 includes a first region D1 and a second region D2 that is closer to the second opening 121 than the first region D1. In the RF transmission member 10, the surface roughness of the protective film 200 that covers the second region D2 is rougher than the surface roughness of the protective film 200 that covers the first region D1.

Description

RF transmission member

[0001] The present invention relates to an RF transmission member.

[0002] For example, in a semiconductor manufacturing apparatus such as an etching apparatus, an RF transmission member is provided. The RF transmission member is a member that transmits high-frequency radio waves (RF) generated by an outer coil to an inner space and generates plasma in the space. As described in Patent Document 1 below, in recent years, an RF transmission member having a cylindrical shape has also been proposed and has already been put into practical use.

[0003] In such an RF transmission member, an opening formed at one end of the cylindrical body is used as a gas inlet, and an opening formed at the other end is used as a plasma outlet. The inner surface of the cylindrical body is covered with a protective film for protecting the cylindrical body from plasma. As the material of the cylindrical body, for example, alumina or the like is used. As the material of the protective film, for example, yttria or the like is used.

[0004] Japanese Patent Application Laid-Open No. 2023-2673

[0005] A shower plate is disposed between the chamber in which the substrate to be processed is disposed and the RF transmission member. The shower plate is a plate-like member in which a large number of through holes are formed, and is disposed so as to cover the opening on the outlet side of the RF transmission member. Plasma generated inside the RF transmission member, specifically, particles such as radicals contained in the plasma are supplied to the lower chamber through the through holes formed in the shower plate, and then subjected to processes such as etching.

[0006] In the internal space of the RF transmission member, in the portion near the lower end of the cylindrical body, particles such as radicals tend to accumulate, so the plasma concentration tends to be high. That is, in the space above the shower plate, the plasma concentration in the outer peripheral portion tends to be higher than that in the inner peripheral portion when viewed from above. If plasma is supplied to the substrate side through the shower plate while there is a plasma concentration difference between the inner peripheral side and the outer peripheral side, the etching rate for each location may become uneven.

[0007] This invention has been made in view of these problems, and its objective is to provide an RF-transmitting member that can homogenize the concentration distribution of plasma supplied toward the substrate.

[0008] To solve the above problems, the RF-transmitting member according to the present invention comprises a cylindrical body and a protective film covering the inner surface of the cylindrical body. A first opening is formed at one end of the cylindrical body, and a second opening with a larger inner diameter than the first opening is formed at the other end of the cylindrical body. The inner surface of the cylindrical body includes a first region and a second region located on the second opening side of the first region. In this RF-transmitting member, the surface roughness of the protective film covering the second region is rougher than the surface roughness of the protective film covering the first region.

[0009] If the surface of the protective film is roughened in the second region, which is the outer peripheral region on the inner surface of the cylindrical body (i.e., the outer peripheral region when viewed from above), the frequency of radical collisions with that surface increases. As a result, the plasma concentration in the surrounding space decreases locally. Consequently, the difference in plasma concentration between the inner and outer peripheral sides becomes smaller, making it possible to make the etching rate more uniform across different locations.

[0010] According to the present invention, it is possible to provide an RF-transmitting member that can homogenize the concentration distribution of plasma supplied toward the substrate.

[0011] This is a schematic diagram showing the configuration of a semiconductor manufacturing apparatus. This is a diagram showing a cross-section of the RF-transmitting member according to this embodiment.

[0012] 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.

[0013] The RF-transmitting member 10 according to this embodiment is used in semiconductor manufacturing equipment such as a plasma etching apparatus. Before describing the RF-transmitting member 10, the configuration of the semiconductor manufacturing equipment will be described first.

[0014] Figure 1 schematically shows the configuration of an etching apparatus EQ, which is an example of semiconductor manufacturing equipment. The etching apparatus EQ is a device for selectively removing a portion of a film that has been pre-formed on the surface of a substrate W to be processed, using plasma. The etching apparatus EQ comprises a chamber CM, a pump PM, a chuck section EC, a gas supply section GS, and an RF-transmitting member 10.

[0015] The chamber CM is a container that houses the chuck portion EC and the like inside. The etching process on the substrate W is performed inside the chamber CM. Among the components that make up the chamber CM, the upper component (top plate) in Figure 1 has an opening OP formed therein, and the shower plate SH and RF-transmitting member 10, which will be described later, are provided to cover the opening OP from above.

[0016] Pump PM is a device for reducing the pressure inside the chamber CM. By using Pump PM to expel the gas from inside the chamber CM, the pressure inside the chamber CM is reduced to a pressure suitable for plasma generation and etching.

[0017] The chuck unit EC is a device that supports the substrate W from below. For example, an electrostatic chuck that uses electrostatic force to attract and fix the substrate W is used as the chuck unit EC. The chuck unit EC is installed on a support base SB located inside the chamber CM.

[0018] The gas supply unit GS is a device that supplies the gas necessary for plasma generation. The gas from the gas supply unit GS is supplied into the RF permeable member 10, which will be described below, and becomes plasma which is then supplied into the chamber CM.

[0019] The RF permeable member 10 is a cylindrical member that connects the gas supply unit GS and the chamber CM. As shown in Figure 2, the RF permeable member 10 comprises a cylindrical body 100 and a protective film 200.

[0020] The cylindrical body 100 is a component that makes up the majority of the RF-transmitting member 10. The cylindrical body 100 is made of a material that can transmit high-frequency radio waves (RF) generated by the coil CL described later, such as a ceramic material such as alumina. The cross-section of the cylindrical body 100 shown in Figure 2 is the cross-section obtained when the cylindrical body 100 is cut by a plane containing its central axis AX. The shape of the cylindrical body 100 is obtained by rotating the cross-section shown in Figure 2 360 degrees around the central axis AX. Therefore, the cross-sectional shape when the cylindrical body 100 is cut perpendicular to the central axis AX is circular regardless of the height position of the cut surface.

[0021] A circular first opening 111 is formed at one end 110 of the cylindrical body 100, along the central axis AX (the upper side in Figure 2). A circular second opening 121 is formed at the other end 120 of the cylindrical body 100, along the central axis AX (the lower side in Figure 2). The inner diameter of the second opening 121 is larger than the inner diameter of the first opening 111.

[0022] As shown in Figure 1, end 110 is connected to the end of the supply piping extending from the gas supply unit GS. End 120 is connected to the chamber CM via a shower plate SH. The shower plate SH is a plate-shaped member made of metal, provided to cover the entire opening OP. The shower plate SH covers the entire second opening 121 from below and the entire opening OP from above. Multiple through holes HL are formed in the shower plate SH. The internal space of the cylindrical body 100 and the internal space of the chamber CM are in communication with each other via the through holes HL.

[0023] A coil CL is positioned on the outside of the cylindrical body 100. The coil CL is for generating high-frequency radio waves necessary for plasma generation. When an AC voltage is applied between the coil CL and the support base SB, the generated high-frequency radio waves pass through the cylindrical body 100 and enter its internal space. The gas supplied to the inside of the cylindrical body 100 from the gas supply unit GS is ionized by the high-frequency radio waves and becomes a plasma containing numerous particles such as radicals. The plasma enters the chamber CM through the through-hole HL of the shower plate SH and is used for processes such as etching on the substrate W. Some of the supplied gas may also become plasma after entering the chamber CM through the through-hole HL.

[0024] As shown in Figure 2, the cylindrical body 100 is a dome-shaped member such that its entire inner surface 130 is generally a concave curved surface. In the cross-section of Figure 2, the portion of the curve representing the shape of the inner surface 130 labeled "131" protrudes inward in an arc shape. The portion of the same curve labeled "132" protrudes outward in an arc shape. The shape of the cylindrical body 100 is not limited to this shape, and various other shapes can be adopted.

[0025] The protective film 200 is a film formed to cover the entire inner surface 130 of the cylindrical body 100. The protective film 200 is provided as a film to protect the inner surface 130 of the cylindrical body 100 from plasma. The protective film 200 is formed of a material that has resistance to plasma, for example, a material mainly composed of yttria. The thickness of the protective film 200 is appropriately set according to the length of time for which resistance to plasma is required. In this embodiment, the thickness of the protective film 200 is approximately 10 μm. The protective film 200 can be formed, for example, using the aerosol deposition method. The protective film 200 may also be formed using physical vapor deposition (PVD) or chemical vapor deposition (CVD).

[0026] Incidentally, within the space inside the RF-transmitting member 10, particles such as radicals tend to accumulate in the area near the lower end of the cylindrical body 100. For this reason, the plasma concentration tends to be higher in that area. In other words, in the space above the shower plate SH, the plasma concentration tends to be higher in the outer peripheral area compared to the inner peripheral area when viewed from above. If plasma is supplied to the substrate side through the shower plate SH while there is such a difference in plasma concentration between the inner and outer peripheral areas, there is a possibility that the etching rate will become uneven from place to place.

[0027] Therefore, in the RF-transmitting member 10 of this embodiment, the above problem is solved by devising the distribution of surface roughness in the protective film 200.

[0028] The region of the inner surface 130 of the cylindrical body 100 that is above the dashed-dotted line DL shown in Figure 2 will hereafter be referred to as the "first region D1". The region of the inner surface 130 that is below the dashed-dotted line DL (i.e., on the side of the second opening 121) will hereafter be referred to as the "second region D2".

[0029] The second region D2 is located on the outer periphery of the first region D1 when viewed from above, and is also close to the shower plate SH. As described above, the phenomenon of particles such as radicals accumulating is likely to occur in the part of the internal space of the cylindrical body 100 that is near the second region D2.

[0030] As shown in the enlarged view labeled "A" in Figure 2, the surface S1 of the protective film 200 covering the first region D1 is a relatively smooth surface. On the other hand, as shown in the enlarged view labeled "B" in Figure 2, the surface S2 of the protective film 200 covering the second region D2 is a relatively rough surface. In other words, in this embodiment, the distribution of surface roughness in each part of the protective film 200 is adjusted so that the surface roughness of the protective film 200 covering the second region D2 is rougher than the surface roughness of the protective film 200 covering the first region D1. Surface roughness can be adjusted, for example, by varying the method of polishing the surface of the protective film 200 in different locations after the film formation is complete.

[0031] If the surface S2 of the protective film 200 is made rough in the second region D2, which is the outer peripheral portion of the inner surface 130 of the cylindrical body 100, the frequency of radical collisions with the surface S2 increases. Many of the radicals that collide with the surface S2 become reaction products and deposit on the surface S2. In other words, radicals are more easily consumed in the space near the second region D2 due to the rough surface S2. As a result, the plasma concentration tends to decrease locally near the second region D2.

[0032] Therefore, the plasma concentration difference mentioned earlier, that is, the tendency for the plasma concentration to be higher in the outer peripheral area when viewed from above, is mitigated by roughening the surface S2. This reduces the plasma concentration difference supplied to each part of the substrate W, making it possible to make the etching rate at each location more uniform.

[0033] Furthermore, it is conceivable to make the surface roughness of the entire protective film 200, including the portion covering the first region D1, similar to the portion covering the second region D2. However, if the surface of the protective film 200 is made rough, there is a tendency for more reaction products to be generated on that surface due to radical collisions, etc. Therefore, if the entire surface of the protective film 200 is made rough as described above, there is a possibility that reaction products generated at a position directly above the substrate W may fall and reach the substrate W. To prevent this, it is preferable to make the surface roughness of the protective film 200 smooth in the first region D1, which is on the central side when viewed from above, as in this embodiment.

[0034] It is preferable that the arithmetic surface roughness (Ra) of the surface S2 of the protective film 200 covering the second region D2 be 0.06 μm or more. Experiments conducted by the inventors have confirmed that setting the surface S2 to such a surface roughness sufficiently increases the frequency of radical collisions with the surface S2.

[0035] It is preferable that the arithmetic surface roughness of the surface S1 of the protective film 200 covering the first region D1 be 0.15 μm or less. Experiments conducted by the inventors have confirmed that, under the condition that surface S2 is rougher than surface S1, setting surface S1 to such a surface roughness sufficiently suppresses the generation of reaction products on surface S1.

[0036] The surface roughness of the portion of the protective film 200 covering the first region D1 and the surface roughness of the portion covering the second region D2 may change discontinuously at the position of the dashed line DL, or they may change smoothly.

[0037] Furthermore, the first region D1 may be the entire region above the dashed-dotted line DL in Figure 2, or it may be a portion of the region above the dashed-dotted line DL. Similarly, the second region D2 may be the entire region below the dashed-dotted line DL in Figure 2, or it may be a portion of the region below the dashed-dotted line DL.

[0038] However, given that the phenomenon of particles such as radicals accumulating is particularly likely to occur in the space near the lower end of the inner surface 130, it is preferable to set the second region D2 to be the region of the inner surface 130 that is closest to the second opening 121, as in this embodiment.

[0039] 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.

[0040] 10: RF-transmitting member 100: Cylindrical body 111: First opening 121: Second opening 130: Inner surface 200: Protective film D1: First region D2: Second region

Claims

1. An RF-transmitting member comprising a cylindrical body and a protective film covering the inner surface of the cylindrical body, wherein a first opening is formed at one end of the cylindrical body, a second opening having a larger inner diameter than the first opening is formed at the other end of the cylindrical body, the inner surface of the cylindrical body includes a first region and a second region located on the second opening side of the first region, and the surface roughness of the protective film covering the second region is rougher than the surface roughness of the protective film covering the first region.

2. The RF-transmitting member according to claim 1, characterized in that the second region is the region on the inner surface of the cylindrical body that is closest to the second opening.

3. The RF-transmitting member according to claim 1, characterized in that the arithmetic surface roughness of the protective film covering the second region is 0.06 μm or more.

4. The RF-transmitting member according to claim 1, characterized in that the arithmetic surface roughness of the protective film covering the first region is 0.15 μm or less.

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