Method for removing coating film of tool, and coating film removing device

Abstract

A coating removal method for removing a coating formed on the surface of a tool by generating plasma in a vacuum container in which a tool having a peak-valley structure in which peaks and valleys are alternately arranged on the surface thereof is disposed, and performing plasma treatment using the plasma, the method for removing the coating film is characterized by switching, once or more, the following steps: a high-pressure plasma processing step in which plasma processing is performed by setting the pressure in the vacuum container to a predetermined first pressure value, and the removal speed of the coating film at the bottom of the valley portion is made higher than the removal speed of the coating film at the edge of the valley portion, and a high-pressure plasma processing step in which plasma processing is performed by setting the pressure in the vacuum container to a predetermined first pressure value; and a low-pressure plasma processing step in which plasma processing is performed by setting the pressure in the vacuum container to a second pressure value smaller than the first pressure value, and the removal speed of the film at the edge part of the valley part is set to be greater than the removal speed of the film at the bottom part of the valley part.

Description

Technical Field

[0001] The present invention relates to a coating removal method and a coating removal device for removing a coating from a tool using plasma. Background Art

[0002] Previously, there were tools called coated tools, or tools referred to as coated tools, that were made by applying a coating treatment (coating) to the surface of a base material made of tool steel or super-hard alloy, imparting properties such as wear resistance or heat resistance in addition to the base material's inherent properties. With use, the coating formed on the surface of such tools wears away or peels off, reaching the end of their lifespan. Previously, such used tools could not be directly reused and were often discarded. However, in recent years, the coating on the surface of used tools has been cleanly removed (de-coating) and re-coated, allowing them to be recycled.

[0003] As a method for removing film from the surface of a tool, Patent Document 1, for example, describes a method in which the film is removed by irradiating the tool with an ion beam emitted from an ion source. However, this method using an ion beam has a problem in that the number of tools that can be processed at one time is small due to the narrow processing area, resulting in poor efficiency of the film removal process.

[0004] Another known method for removing coatings from tool surfaces is a method in which plasma is generated within a vacuum chamber in which the tool is located, and plasma treatment using this plasma is used to remove the coating from the tool surface. Plasma-based coating removal methods can generate plasma over a wide area within the vacuum chamber, offering the advantage of being able to treat a wider range of tools compared to methods using ion beams, which have a narrow treatment area.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2016 / 163278 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] However, in the case of the method using plasma as described above, a potential difference is generated between the plasma and the surface of the tool, and a region called a plasma sheath, in which the flow of electrons and ions changes significantly compared to that in the plasma, is formed in a manner covering the surface. The plasma sheath sometimes becomes an obstacle to efficient film removal. For example, when removing the film of a tool having a peak-valley structure with alternating peaks and valleys (convex and concave parts) such as drill grooves on the surface, the distance to the plasma sheath layer (the boundary surface between the plasma sheath and the plasma) is different at the bottom and edge of the valley, so the ion incident density is different, and the film removal rate is uneven. As a result, even if the film formed on the edge of the valley can be removed in a short time, it takes time to remove the film formed at the bottom of the valley. Overall, the film cannot be removed efficiently, and sometimes extra power consumption is consumed.

[0010] The present invention is made to solve the above-mentioned problems, and a main object of the present invention is to efficiently remove a film formed on the surface of a tool having a peak-valley structure using plasma.

[0011] Technical means to solve the problem

[0012] To address the aforementioned issues, the present inventors conducted research and discovered that the thickness of the plasma sheath formed around a tool can be adjusted by varying the pressure within the vacuum vessel where the plasma is generated. Further research led the inventors to discover that, for example, when removing coatings from tools with a peak-and-valley (concave-convex) structure, such as drills, end mills, hobs, or taps, increasing the pressure within the vacuum vessel can reduce the thickness of the plasma sheath. This increases the ion incidence density near the bottom of the valleys of the peak-and-valley structure, effectively removing the coating at the bottom. Conversely, decreasing the pressure within the vacuum vessel increases the thickness of the plasma sheath, increasing the ion incidence density near the edges of the valleys, effectively removing the coating at the edges. By combining these multiple pressure conditions for plasma processing, the present inventors achieved the present invention.

[0013] That is, the film removal method of the tool of the present invention is to generate plasma in a vacuum container of a tool provided with a peak-valley structure with peaks and valleys arranged alternately on its surface, and use the plasma to perform plasma treatment, thereby removing the film formed on the surface of the tool. The film removal method is characterized in that the following steps are switched and performed one or more times: a high-pressure plasma treatment step, in which the pressure in the vacuum container is set to a prescribed first pressure value to perform plasma treatment, and the film removal rate at the bottom of the valley is greater than the film removal rate at the edge of the valley; and a low-pressure plasma treatment step, in which the pressure in the vacuum container is set to a second pressure value smaller than the first pressure value to perform plasma treatment, and the film removal rate at the edge is greater than the film removal rate at the bottom.

[0014] If this is the case, for example, in the case of removing the coating of a tool having a peak-valley structure such as a drill groove, in a high-pressure plasma treatment process with a relatively high pressure value, the thickness of the plasma sheath formed on the tool surface is reduced, thereby increasing the ion incidence density near the bottom of the valley of the peak-valley structure, for example, and efficiently removing the coating at the bottom. On the other hand, in a low-pressure plasma treatment process with a relatively low pressure value, the thickness of the plasma sheath is increased, thereby increasing the ion incidence density near the edge of the valley of the peak-valley structure, and efficiently removing the coating at the peak.

[0015] By combining this high-pressure plasma treatment process with a low-pressure plasma treatment process to perform plasma treatment, the area with high ion incidence density in the peak-valley structure of the tool can be changed, and the area where the film is concentratedly removed can be changed. Therefore, compared with the case where the pressure conditions are set to a constant and ions are continuously incident on the same area, the film formed on the peak-valley structure of the tool can be removed efficiently in a short time and power consumption can also be suppressed.

[0016] As a specific form of the film removal method, it can be listed that the thickness of the plasma sheath formed around the tool in the high-pressure plasma treatment step relative to the valley is smaller than the thickness of the plasma sheath formed in the low-pressure plasma treatment step relative to the valley.

[0017] The film removal method preferably includes switching between the high-pressure plasma treatment step and the low-pressure plasma treatment step and performing them two or more times.

[0018] When switching between the high-pressure plasma treatment step and the low-pressure plasma treatment step, each step is performed once. There is a risk that the coating components removed and scattered in the subsequent plasma treatment step may re-adhere to the tool surface exposed by the film removal in the previous plasma treatment step, and remain unremoved. By switching between the high-pressure plasma treatment step and the low-pressure plasma treatment step two or more times, such re-adhered coating components can be more reliably removed.

[0019] In addition, the film removal method preferably includes performing the plasma treatment using inductively coupled plasma.

[0020] In this manner, by using high-density plasma, the film removal rate can be increased, and the film removal can be performed more efficiently.

[0021] In addition, a tool coating removal device of the present invention uses plasma to remove a coating formed on the surface of a tool having a peak-valley structure with alternating peaks and valleys. The coating removal device is characterized by comprising: a vacuum container for accommodating the tool; a plasma source for generating plasma within the vacuum container; and a control device for controlling the pressure within the vacuum container and switching between a high-pressure plasma processing mode and a low-pressure plasma processing mode. The high-pressure plasma processing mode sets the pressure within the vacuum container to a predetermined first pressure value for plasma processing, and removes the coating at the bottom of the valleys faster than the coating at the edges of the valleys. The low-pressure plasma processing mode sets the pressure within the vacuum container to a second pressure value lower than the first pressure value for plasma processing, and removes the coating at the edges of the valleys faster than the coating at the bottom of the valleys. The control device switches between the high-pressure plasma processing mode and the low-pressure plasma processing mode one or more times to remove the coating formed on the tool surface.

[0022] The film removal device having such a structure can achieve the same effects as the film removal method of the present invention described above.

[0023] Effects of the Invention

[0024] According to the present invention thus constituted, a film formed on the surface of a tool having a peak-valley structure can be efficiently removed using plasma. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] [ Figure 1 ] is a longitudinal sectional view schematically showing the structure of a film removal device according to one embodiment of the present invention.

[0026] [ Figure 2] is a cross-sectional view schematically showing the structure of a film removal device according to one embodiment of the present invention.

[0027] [ Figure 3 ] is a diagram showing a tool to be processed by the film removal device as one embodiment of the present invention.

[0028] [ Figure 4 ] is a diagram illustrating the principle of a film removal method performed by a film removal apparatus according to one embodiment of the present invention, and is a diagram showing the relationship between plasma density and the level of the plasma sheath formed around the tool.

[0029] [ Figure 5 ] is a graph showing the position of the end of the remaining portion of the film when the film removal test is performed under various conditions.

[0030] [ Figure 6 ] is a graph showing the amount of power generated by the high-frequency power supply when performing a film removal test under different pressure conditions. DETAILED DESCRIPTION

[0031] Hereinafter, a film removal apparatus according to an embodiment of the present invention and a film removal method using the film removal apparatus will be described with reference to the drawings.

[0032] <Device Structure>

[0033] The film removal apparatus 100 of the present embodiment removes a film formed on the surface of the tool T by plasma processing using inductively coupled plasma.

[0034] Specifically, if Figure 1 and Figure 2 As shown, the film removal apparatus 100 includes a vacuum vessel 1 forming a processing chamber S that is evacuated and into which gas is introduced; an antenna 2 disposed outside the vacuum vessel 1; and a high-frequency power supply 3 that applies high-frequency waves to the antenna 2. In this configuration, the high-frequency waves applied to the antenna 2 by the high-frequency power supply 3 cause a high-frequency current to flow through the antenna 2, generating an induced electric field within the vacuum vessel 1 and generating an inductively coupled plasma. In this embodiment, the antenna 2 and the high-frequency power supply 3 that applies the high-frequency waves constitute a plasma source.

[0035] The tool T to be processed by the film removal device 100 of this embodiment is a so-called coated tool or a tool called a coated tool, for example, a tool having a film (also called a coating) formed on the surface of a substrate comprising tool steel or super-hard alloy. The film is formed on the surface of the substrate of the tool by chemical vapor deposition (chemical vapor deposition (CVD) method) or physical vapor deposition (physical vapor deposition (PVD) method) for the purpose of improving hardness, wear resistance or heat resistance. Specific examples of the film include: Ti-based coatings such as TiN coatings or TiAlN coatings, Cr-based coatings such as CrN coatings or AlCrN coatings, diamond-like carbon (DLC) (amorphous hard carbon) coatings, etc. The tool T has a peak-valley structure Z on the surface of the substrate, such as a drill groove, in which peaks M and valleys V (also called convex and concave portions) are alternately arranged, and a film is formed on the surface of the peak-valley structure. Specifically, the tool T is preferably a cutting tool such as a drill or an end mill, but is not limited thereto. Figure 3 As shown, the tool T to be processed in this embodiment is a drill having a spiral groove, that is, a peak-valley structure Z, on its surface.

[0036] The vacuum container 1 is, for example, a metal container and, in this embodiment, is cylindrical. An opening is formed in the wall (here, the side wall 1a) of the vacuum container 1, extending through the wall in the thickness direction. The vacuum container 1 is electrically grounded, and the processing chamber S within it is evacuated by a vacuum exhaust device 4.

[0037] The plasma generating gas is introduced into the vacuum container 1, for example, via a flow regulator 11 or one or more gas inlet ports 12 provided in the vacuum container 1. The plasma generating gas is, for example, a rare gas such as argon gas, a halogen gas, or a mixed gas thereof, and can be appropriately changed according to the material of the film to be removed. The gas inlet port 12 is provided in the vacuum container 1, for example, near the other side wall 1b facing the side wall 1a having an opening, and is provided in a manner that blows the plasma generating gas laterally toward the opening. In addition, the gas inlet port 12 is not limited to a position facing the opening formed in the side wall 1a, and can be provided at any position. In this embodiment, a plurality of gas inlet ports 12 are provided along the axial direction (up and down direction) of the vacuum container 1.

[0038] like Figure 1 and Figure 2As shown, the antenna 2 is arranged to face the opening formed in the vacuum container 1. The number of antennas 2 is not limited to one, and multiple antennas 2 may be provided. The antenna 2 of this embodiment is rod-shaped and is arranged upright along the axial direction (vertical direction) of the vacuum container 1.

[0039] The antenna 2 has one end, a power supply end 2a, connected to a high-frequency power source 3 via a matching circuit 31, and the other end, a terminal 2b, directly grounded. Alternatively, the terminal 2b may be grounded via a capacitor or a coil.

[0040] The high-frequency power supply 3 can flow a high-frequency current into the antenna 2 via the matching circuit 31. The frequency of the high-frequency current is generally 13.56 MHz, for example, but is not limited thereto and can be changed as appropriate.

[0041] The film removal device 100 has a magnetic field transmission window W that transmits the magnetic field generated by the antenna 2. Specifically, the film removal device 100 includes a slit plate 7 that blocks an opening formed in the wall (side wall 1a) of the vacuum container 1 from the outside of the vacuum container 1; and a dielectric plate 8 that blocks the slit formed in the slit plate 7 from the outside of the vacuum container 1. The slit plate 7 and the dielectric plate 8 form the magnetic field transmission window W.

[0042] The slit plate 7 allows the high-frequency magnetic field generated by the antenna 2 to pass into the vacuum vessel 1 while preventing the electric field from entering the vacuum vessel 1 from outside. Specifically, the slit plate 7 is a metal slit plate having a rectangular flat plate shape and having a plurality of slits arranged at equal intervals along the length of the antenna 2 and extending through the slit plate 7 in the thickness direction.

[0043] The slit plate 7 is larger than the opening of the vacuum container in a plan view and blocks the opening while being supported by the side wall 1a. A sealing member such as an O-ring or a gasket is interposed between the slit plate 7 and the side wall 1a, and the space therebetween is vacuum-sealed.

[0044] The dielectric plate 8 is disposed on the outwardly facing surface of the slit plate 7, which faces the outside of the vacuum container 1, and closes the slit of the slit plate 7. The dielectric plate 8 is generally a flat plate made of a dielectric material, such as ceramics such as alumina, silicon carbide, and silicon nitride; inorganic materials such as quartz glass and alkali-free glass; or resin materials such as fluororesins (e.g., Teflon). A sealing member such as an O-ring or gasket is interposed between the dielectric plate 8 and the slit plate 7, providing a vacuum seal.

[0045] With the above configuration, when a high-frequency wave is applied to antenna 2 from high-frequency power supply 3, the high-frequency magnetic field generated by antenna 2 is formed (supplied) within vacuum vessel 1 through magnetic field transmission window W including slit plate 7 and dielectric plate 8. This generates an induced electric field in the space within vacuum vessel 1, generating inductively coupled plasma.

[0046] The film removal apparatus 100 is further provided with a tool holder 5 for holding tools T within the vacuum chamber 1. The tool holder 5 is configured to hold a plurality of tools T and to rotate and move the tools T within the vacuum chamber 1. Specifically, the tool holder 5 includes a disk-shaped rotating table 51 that rotates within the vacuum chamber 1; a rotating shaft 52 connected to the central axis (rotational axis) of the rotating table 51; and a driving device 53 (specifically, a motor) that rotates the rotating shaft 52.

[0047] The turntable 51 is installed near the bottom wall 1c of the vacuum chamber 1, with its central axis (rotational axis) aligned with the axial direction (vertical direction) of the vacuum chamber 1. A plurality of (here, six) holding portions 511 are provided on the top surface of the turntable 51, which hold the tool T upright with its tip facing upward. The holding portions 511 are arranged rotationally symmetrically with respect to the central axis of the turntable 51, when viewed from the top and bottom.

[0048] The rotating shaft 52 is a rod-shaped metal shaft with one end connected to the bottom surface of the rotating table 51. It is arranged so as to align with the axial direction of the vacuum chamber 1. The rotating shaft 52 passes through the bottom wall 1c of the vacuum chamber 1 and one end is connected to a driving device 53 disposed outside the vacuum chamber 1. The rotating shaft 52 and the bottom wall 1c are sealed by an insulating sealing member.

[0049] The rotating shaft 52 is rotated by the driving device 53, thereby rotating the rotating table 51. As a result, the plurality of tools T held by the plurality of holding portions 511 of the rotating table 51 are rotated about the rotating shaft 52. In this embodiment, the rotating shaft 52 is rotated by the driving device 53, and the holding portions 511 themselves are also rotated on the rotating table 51.

[0050] The film removal apparatus 100 includes a bias power supply 6 that applies a bias voltage to the tool holder 5. The bias voltage is, for example, a negative DC voltage, but is not limited thereto. This bias voltage controls the energy of positive ions in the plasma when they strike the film on the surface of the tool T, thereby controlling the film removal rate.

[0051] The film removal apparatus 100 also includes a control device 9 for controlling film treatment conditions. This control device 9 is, for example, a computer comprising analog circuits including buffers and amplifiers, digital circuits including a central processing unit (CPU), memory, or a digital signal processor (DSP), and an analog-to-digital (A / D) converter interposed between these components. The control device 9 functions as an antenna power control unit 91, a bias voltage control unit 92, a pressure control unit 93, and a stent control unit 94 by operating in conjunction with the CPU and its peripherals according to a predetermined program stored in memory.

[0052] The antenna power control unit 91 controls the output of the high-frequency power supply 3, thereby controlling the high-frequency current flowing through the antenna 2. The bias voltage control unit 92 controls the bias power supply 6, thereby controlling the bias voltage value applied to the tool holder 5. The pressure control unit 93 controls the flow rate of the plasma generation gas supplied to the processing chamber S by controlling the flow regulator, and controls the pressure within the processing chamber S by adjusting the opening of the vacuum exhaust valve (not shown) located above the vacuum pump 4. The holder control unit 94 controls the rotation of the turntable 51 by controlling the drive device 53.

[0053] Moreover, the film removal device 100 of this embodiment is configured to adopt a high-pressure plasma processing mode and a low-pressure processing mode, and alternately switch between these two plasma processing modes to perform plasma processing to remove the film formed on the surface of the tool T. In the high-pressure plasma processing mode, the pressure control unit 93 adjusts the flow rate of the plasma generating gas supplied to the processing chamber S and the opening of the vacuum exhaust valve, and sets the pressure in the vacuum container 1 to a specified first pressure value to perform plasma processing. In the low-pressure processing mode, the pressure in the vacuum container 1 is set to a second pressure value smaller than the first pressure value to perform plasma processing.

[0054] The film removal device 100 of this embodiment changes the shape of the plasma sheath layer formed between the plasma formed in the processing chamber S and the surface of the tool T by switching between the high-pressure processing mode and the low-pressure processing mode, and can efficiently remove the film formed on the peak-valley structure Z of the tool T.

[0055] The first pressure value is set to a value such that a plasma sheath layer is formed along the surface of the valley V of the tool T and ions in the plasma can be incident on the bottom V1 of the valley V. In other words, the first pressure value is set to a value such that the film removal rate (or ion incidence density) at the bottom V1 of the valley V is greater than the film removal rate (or ion incidence density) at the edge V2 of the valley V during plasma processing. In a plasma processing step based on a high-pressure plasma processing mode (also referred to as a high-pressure plasma processing step), as Figure 4 As shown in (a), the plasma treatment is continued for a predetermined time at the first pressure value, thereby preferentially removing the film formed on the bottom V1 of the valley V of the tool T (i.e., the inner area of the valley V), and the exposed area of the substrate surface gradually expands from the bottom V1 of the valley V to the edge V2. In addition, Figure 4 (a) shows a cross section of the tool T. Figure 4 The same applies to (b). In the high-pressure plasma treatment step, the rate of removing the film at the bottom V1 of the valley V is higher than the rate of removing the film at the bottom V1 of the valley V in the low-pressure plasma treatment step described later.

[0056] On the other hand, the second pressure value is set to a value such that the plasma sheath layer is formed at a position away from the surface of the tool T (that is, the plasma sheath is formed thicker) and the ions in the plasma are more easily incident on the edge portion V2 than on the bottom portion V1 of the valley portion V, compared to the case of the first pressure value. In other words, the second pressure value is set so that the removal rate of the film at the edge portion V2 of the valley portion V (or the ion incidence density) is greater than the removal rate of the film at the bottom portion V1 of the valley portion V during plasma treatment. In the low-pressure plasma treatment mode (also referred to as the low-pressure plasma treatment process), as Figure 4 As shown in (b), plasma treatment is continued for a predetermined time at the second pressure value, thereby preferentially removing the film formed on the edge portion V2 of the valley V of the tool T (i.e., the area outside the valley V), and the exposed area of the substrate surface gradually expands from the edge portion V2 of the valley V toward the bottom portion V1. In the low-pressure plasma treatment step, the film removal rate at the edge portion V2 of the valley V is greater than the film removal rate at the edge portion V2 of the valley V in the high-pressure plasma treatment step.

[0057] The film removal apparatus 100 preferably performs the high-pressure plasma treatment process and the low-pressure plasma treatment process alternately at a predetermined timing once or more, preferably twice or more, to remove the film from the tool T. Either the high-pressure plasma treatment process or the low-pressure plasma treatment process may be performed first.

[0058] In the high-pressure plasma treatment process and the low-pressure plasma treatment process, the amount of high-frequency power supplied to the antenna 2 may be the same or different. The amount of high-frequency power supplied to the antenna 2 is, for example, 400W to 1000W, but is not limited thereto.

[0059] <Effects of this embodiment>

[0060] According to the film removal device 100 of this embodiment constructed in this way, for example, when removing the film of a tool T having a peak-valley structure Z in which peaks M and valleys V such as spiral grooves are alternately arranged, in a high-pressure plasma treatment process with a relatively high pressure value, the thickness of the plasma sheath formed on the surface of the tool T is reduced, thereby increasing the ion incidence density near the inner side (bottom V1, etc.) of the valley V of the peak-valley structure, and efficiently removing the film at the bottom V1. On the other hand, in a low-pressure plasma treatment process with a relatively low pressure value, the thickness of the plasma sheath is increased, thereby increasing the ion incidence density near the outer side (edge V2) of the valley V of the peak-valley structure Z, and efficiently removing the film at the edge V2. By combining this high-pressure plasma treatment process with a low-pressure plasma treatment process to perform plasma treatment, the area with high ion incidence density can be changed in the peak-valley structure of the tool T showing an intricate shape, and the area where the film is concentratedly removed can be changed. Therefore, compared with the case where the pressure conditions are set to a constant and ions are continuously incident on the same area, the entire film of the tool T can be removed efficiently in a short time and power consumption can be suppressed.

[0061] <Other Modified Embodiments>

[0062] In addition, the present invention is not limited to the above-described embodiments.

[0063] For example, the film removal apparatus 100 of the embodiment described above switches between a high-pressure plasma treatment process and a low-pressure plasma treatment process to perform plasma treatment under two different pressure conditions, but the present invention is not limited thereto. The film removal apparatus 100 of other embodiments may also perform plasma treatment at a third pressure value different from the first and second pressure values, thereby switching between three different pressure conditions.

[0064] The film removal apparatus 100 of the above embodiment employs a so-called external antenna system, in which high-frequency waves are applied to an antenna 2 disposed outside the vacuum chamber 1 to generate plasma within the vacuum chamber 1. However, the present invention is not limited thereto. In other embodiments, a so-called internal antenna system may be employed, in which the antenna 2 is disposed within the vacuum chamber 1 to generate plasma.

[0065] Furthermore, in the above embodiment, plasma treatment is performed using inductively coupled plasma, but the present invention is not limited thereto. In other embodiments, plasma treatment may be performed using plasma generated by other methods, such as capacitively coupled plasma. In other embodiments, the plasma source may be configured without using an antenna or a high-frequency power supply.

[0066] In the above embodiment, the tool T is a drill bit, and the peak-valley structure Z is a spiral groove, but the present invention is not limited to this. In other embodiments, the tool T may be an end mill, a hob, or a tap, and the peak-valley structure Z may be any concave-convex shape formed on the working portion of the tool, such as a thread groove or a cutting edge.

[0067] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit and scope of the invention.

[0068] Example

[0069] The present invention is not limited to the following examples, and can be implemented by appropriately adding modifications within the scope of the above and below-mentioned gist, and all such modifications are included in the technical scope of the present invention.

[0070] Using the film removal device 100, three 4mmφ drill bits (tool T) were prepared, and the film removal treatment was performed under different plasma treatment conditions (samples 1 to 3). For sample 1, the high-frequency power applied to the antenna 2 was set to 500W, the pressure condition in the vacuum container 1 during plasma treatment was set to 5Pa, and the film was removed by plasma treatment. For sample 2, the high-frequency power applied to the antenna 2 was set to 500W, the pressure condition in the vacuum container 1 during plasma treatment was set to 15Pa, and the film was removed by plasma treatment. For sample 3, the high-frequency power applied to the antenna 2 was set to 800W, the pressure condition in the vacuum container 1 during plasma treatment was set to 5Pa, and the film was removed by plasma treatment. The results are shown in Figure 5 In addition, Figure 5 The vertical axis represents the position of the end portion of the remaining portion of the film on the tool during the plasma processing (ie, the boundary position between the exposed surface of the tool and the film).

[0071] like Figure 5 As shown, it can be confirmed that in sample 1 in which the pressure of the vacuum container 1 was set to 5 Pa and plasma treatment was performed, the position of the end of the residual part of the film moved from the outside (edge V2) of the valley V to the inside (bottom V1) as time passed, and the film could be removed sequentially from the outside of the valley V.

[0072] On the other hand, it can be confirmed that in sample 2 in which the pressure of the vacuum container 1 was set to 15 Pa and plasma treatment was performed, the position of the end of the residual portion moved from the inside (bottom V1) of the valley V to the outside (edge V2) over time, and the film could be removed sequentially starting from the inside of the valley V.

[0073] Furthermore, it was confirmed that in Sample 3, which underwent plasma treatment with the vacuum container 1 at a pressure of 5 Pa and a high-frequency power of 800 W, the position of the end of the residual portion shifted from the outside (edge V2) of the valley V to the inside (bottom V1) over time, allowing the film to be removed sequentially from the outside of the valley V. It was confirmed that Sample 3 achieved a faster film removal rate than Sample 1, which was treated under the same pressure conditions and with a lower high-frequency power.

[0074] Furthermore, it was confirmed that, under any conditions, all the films formed on the surfaces of the valley portions V could be removed by continuously performing the treatment.

[0075] Figure 6 This is a graph showing the relationship between the amount of high-frequency power consumed for film processing when plasma processing is performed under a single pressure condition (high-frequency power is set to 800W and the pressure in the vacuum container is set to 5Pa) and the amount of high-frequency power consumed for film processing when plasma processing is performed by switching the pressure conditions between high pressure (500W, 15Pa) and low pressure (500W, 5Pa). Figure 6 As such, it was confirmed that, in terms of the amount of power used by the high-frequency power source, switching the pressure conditions can reduce the amount of high-frequency power by up to 15%, thereby improving efficiency.

[0076] Industrial applicability

[0077] According to the film removal apparatus of the present invention configured in this manner, a film formed on the surface of a tool having a peak-valley structure can be efficiently removed using plasma.

[0078] Explanation of Figure Numbers

[0079] 100: Film removal device

[0080] 1: Vacuum container

[0081] 2: Antenna

[0082] 3: High frequency power supply

[0083] 5: Tool holder

[0084] 9: Control device

[0085] T: Tools

[0086] Z: Peak-valley structure

[0087] V: Yabe

[0088] V1: bottom

[0089] V2: Edge

[0090] M: Peak

Claims

1. A film removal method comprising generating plasma in a vacuum container containing a tool having a peak-valley structure with alternating peaks and valleys on its surface, and performing plasma treatment using the plasma to remove a film formed on the surface of the tool, the method comprising switching and performing the following steps one or more times: a high-pressure plasma treatment step, wherein the pressure in the vacuum container is set to a predetermined first pressure value to perform plasma treatment, and a film removal rate at the bottom of the valley portion is set to be higher than a film removal rate at the edge of the valley portion; and The low-pressure plasma treatment step includes setting the pressure in the vacuum container to a second pressure value lower than the first pressure value to perform plasma treatment, and making the film removal rate at the edge of the valley portion higher than the film removal rate at the bottom of the valley portion.

2. The film removal method according to claim 1, wherein A thickness of a plasma sheath formed around the tool in the high-pressure plasma treatment process relative to the valley portion is smaller than a thickness of a plasma sheath formed in the low-pressure plasma treatment process relative to the valley portion.

3. The film removal method according to claim 1, wherein: The high-pressure plasma treatment step and the low-pressure plasma treatment step are switched and performed two or more times.

4. The film removal method according to claim 1, wherein The plasma treatment is performed using inductively coupled plasma.

5. A film removal device for removing a film formed on the surface of a tool having a peak-valley structure in which peaks and valleys are alternately arranged, using plasma. The film removal device comprises: A vacuum container for configuring the tool; a plasma source for generating plasma in the vacuum container; as well as A control device controls the pressure in the vacuum container and switches between a high-pressure plasma processing mode and a low-pressure plasma processing mode. In the high-pressure plasma processing mode, the pressure in the vacuum container is set to a predetermined first pressure value to perform plasma processing, and a film removal rate at the bottom of the valley portion is higher than a film removal rate at the edge of the valley portion. In the low-pressure plasma processing mode, the pressure in the vacuum container is set to a second pressure value lower than the first pressure value to perform plasma processing, and the film removal rate at the edge of the valley portion is higher than the film removal rate at the bottom of the valley portion. The high-pressure plasma processing mode and the low-pressure plasma processing mode are switched and performed one or more times by the control device to remove a film formed on the surface of the tool.

Images