RF transmission member

Abstract

Provided is an RF transmission member capable of stably generating plasma while reducing AC power supplied to an outer coil compared to AC power supplied in conventional technologies. An RF transmission member 10 comprises a cylindrical body 100 and a protective film 200 covering 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 having an inner diameter larger than the inner diameter 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 located 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 covering the first region D1 is greater than the surface roughness of the protective film 200 covering the second region D2.

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 into 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] The coil for generating plasma is often disposed in the vicinity of the cylindrical body, specifically, in the vicinity of the opening that is the gas inlet. When AC power is started to be supplied to the coil, in the vicinity of the inner surface of the cylindrical body, plasma is generated through a process in which (1) the generated radicals collide with the protective film, (2) an electron avalanche occurs due to the collision, and (3) a large amount of radicals are generated by the electron avalanche. The AC power supplied to the coil is preferably made as small as possible within a range where plasma can be stably generated.

[0006] The present invention has been made in view of such problems, and an object thereof is to provide an RF transmission member capable of stably generating plasma while making the AC power supplied to an outer coil smaller than in the conventional case.

[0007] 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 first region is rougher than the surface roughness of the protective film covering the second region.

[0008] In the inner surface of the cylindrical body, the first region, which is the part on the first opening side, is a region where a coil is often placed on its back side. In the RF-transmitting member with the above configuration, the surface of the protective film covering this first region is rough, so the probability and frequency of radicals generated nearby colliding with the surface of the protective film are increased. For this reason, even when the AC power supplied to the coil is reduced compared to conventional designs, plasma can be generated stably.

[0009] According to the present invention, it is possible to provide an RF-transmitting member that can stably generate plasma while using less AC power supplied to the outer coil compared to conventional methods.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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).

[0025] As shown in Figure 2, the coil CL for generating plasma is often positioned near the cylindrical body 100, specifically near the first opening 111, which is the gas inlet. The dashed line DL shown in Figure 2 represents the boundary between the portion of the cylindrical body 100 where the coil CL is located on the outside and the portion where the coil CL is not located on the outside.

[0026] When AC power is supplied to the coil CL, plasma is generated near the inner surface 130 of the cylindrical body 100 through the following process: (1) generated radicals collide with the protective film 200, (2) an electron avalanche occurs as a result of the collision, and (3) a large amount of radicals are generated by the electron avalanche. It is preferable that the AC power supplied to the coil CL be as small as possible within the range that can stably generate plasma.

[0027] Therefore, in the RF-transmitting member 10 of this embodiment, the power required for stable plasma generation is suppressed compared to conventional methods 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 line DL 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 line DL (i.e., towards the second opening 121) will hereafter be referred to as the "second region D2".

[0029] 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 smooth surface. On the other hand, 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 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 first region D1 is rougher than the surface roughness of the protective film 200 covering the second region D2. 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.

[0030] Of the inner surface 130 of the cylindrical body 100, the first region D1, which is the portion on the side of the first opening 111, is a region where a coil CL is often placed on its back side. In the RF-transmitting member 10 with the above configuration, the surface S1 of the protective film 200 covering this first region D1 is rough, so the probability and frequency of radicals generated nearby colliding with the surface S1 increases. As a result, plasma is more easily generated through the processes (1) to (3) described above. For this reason, even if the AC power supplied to the coil CL is reduced compared to conventional methods, plasma can be generated stably.

[0031] Furthermore, reducing the AC power supplied to the coil CL reduces the collision energy of radicals with the protective film 200. This also has the advantage of suppressing the degradation of the protective film 200 associated with sputtering.

[0032] It is preferable that the arithmetic surface roughness (Ra) of the surface S1 of the protective film 200 covering the first region D1 be 0.06 μm or more. Experiments conducted by the inventors have confirmed that setting the surface S1 to such a surface roughness sufficiently suppresses the power required to generate plasma in the vicinity of the surface S1.

[0033] It is preferable that the arithmetic surface roughness of the surface S2 of the protective film 200 covering the second region D2 be 0.15 μm or less. Experiments conducted by the inventors have confirmed that, under the condition that surface S1 is rougher than surface S2, setting surface S2 to such a surface roughness sufficiently suppresses the generation and adhesion of reaction products on surface S2.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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 first region is rougher than the surface roughness of the protective film covering the second region.

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

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 0.15 μm or less.

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