Method for removing coating from tools, and apparatus for removing coating.

Abstract

Provided is a coating removal method for removing a coating formed on the surface of a tool, which is achieved by generating plasma in a vacuum container in which the tool, having a crest-valley structure in which crest and valley parts are alternately arranged on the surface, is disposed and performing plasma treatment with plasma. The coating removal method performs switching once or more between a high-pressure plasma treatment step, in which plasma treatment is performed with the vacuum container pressure set to a predetermined first pressure value, causing the removal speed for the coating at the bottom of the valley parts to be greater than the removal speed for the coating at edges of the valley parts, and a low-pressure plasma treatment step, in which plasma treatment is performed with the vacuum container pressure set to a second pressure value that is less than the predetermined first pressure value, causing the removal speed for the coating at edges of the valley parts to be greater than the removal speed for the coating at the bottom of the valley parts.

Description

Technical Field

[0001] The present invention relates to a film removal method and a film removal apparatus for removing a film on a tool using plasma.

Background Art

[0002] Conventionally, by applying a film treatment (coating treatment) to the surface of a substrate made of tool steel or cemented carbide, in addition to the characteristics inherent to the substrate, characteristics such as wear resistance and heat resistance are further imparted. There is a so-called coated tool or coated tool. Such tools reach their lifespan as the film formed on the surface wears or peels off during use. Conventionally, such used tools are often discarded without being reused as they are, but in recent years, the film on the surface of used tools is removed cleanly (demembraned) and then recoated to be recycled.

[0003] As a method for removing the film on the surface of a tool, for example, Patent Document 1 describes a method of removing the surface film by irradiating the tool with an ion beam emitted from an ion source. However, such a method using ion beam irradiation has a problem that the processing area is narrow, so the amount of tools that can be processed at one time is small, and the efficiency as a demembraning process is poor.

[0004] As another method for removing the film on the surface of a tool, a method of generating plasma in a vacuum container in which the tool is placed and removing the film on the surface of the tool by plasma treatment using the plasma is also known. If it is a method for removing a film using plasma, plasma can be generated over a wide area in the vacuum container, so there is an advantage that more tools can be processed compared to that using an ion beam with a narrow processing area.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, in the case of plasma-based methods as described above, a potential difference is generated between the plasma and the tool surface, and a region called a plasma sheath is formed that covers the surface, where the flow of electrons and ions changes significantly compared to within the plasma. This plasma sheath can become an obstacle to efficient coating removal. For example, when removing a coating from a tool with a surface structure consisting of alternating peaks and valleys (convex and concave sections), the distance to the plasma sheath surface (the interface between the plasma sheath and the plasma) differs between the bottom and edge of the valleys. This results in different ion incidence densities and an uneven coating removal rate. As a result, even if the coating formed on the edge of a valley can be removed quickly, it may take longer to remove the coating formed on the bottom of the valley, making it difficult to remove the coating efficiently overall and resulting in unnecessary power consumption.

[0007] This invention was made to solve the aforementioned problems, and its main objective is to efficiently remove coatings formed on the surface of tools having a peak-and-valley structure using plasma. [Means for solving the problem]

[0008] In order to solve the above problems, the inventors of this invention conducted research and found that the thickness of the plasma sheath formed around the tool could be adjusted by changing the pressure value inside the vacuum vessel that generates the plasma. As a result of further diligent research, the inventors of this invention found that when removing the coating from a tool having a mountain-and-valley (uneven) structure on its surface, such as a drill, end mill, hob, or tap, increasing the pressure inside the vacuum vessel can reduce the thickness of the plasma sheath, thereby increasing the ion incidence density near the bottom of the valleys in the mountain-and-valley structure and efficiently removing the coating at the bottom. On the other hand, lowering the pressure inside the vacuum vessel can increase the thickness of the plasma sheath, increasing the ion incidence density near the edges of the valleys and efficiently removing the coating at the edges. By combining these multiple pressure conditions and performing plasma treatment, the coating on the tool can be efficiently removed, leading to the present invention.

[0009] In other words, the method for removing a coating from a tool according to the present invention is a method for removing a coating formed on the surface of a tool having a surface with alternating peaks and valleys, by generating plasma in a vacuum vessel in which a tool is placed and performing plasma treatment using the plasma, characterized in that the method is performed by switching between one or more steps: a high-pressure plasma treatment step in which the pressure in the vacuum vessel is set to a predetermined first pressure value and plasma treatment is performed, and the rate of coating removal at the bottom of the valleys is greater than the rate of coating removal at the edges of the valleys; and a low-pressure plasma treatment step in which the pressure in the vacuum vessel is set to a second pressure value less than the first pressure value and plasma treatment is performed, and the rate of coating removal at the edges is greater than the rate of coating removal at the bottom.

[0010] In this way, when removing a coating from a tool having a peak-and-valley structure, such as a drill groove, the thickness of the plasma sheath formed on the tool surface can be reduced in a high-pressure plasma treatment process where the pressure value is relatively high. This increases the ion incidence density near the bottom of the valleys in the peak-and-valley structure, allowing for efficient removal of the coating at the bottom. On the other hand, in a low-pressure plasma treatment process where the pressure value is relatively low, the thickness of the plasma sheath can be increased. This increases the ion incidence density near the edges of the valleys in the peak-and-valley structure, allowing for efficient removal of the coating on the peaks. By combining high-pressure and low-pressure plasma treatment processes, it is possible to change the locations with high ion incidence density in the peaks and valleys structure of the tool, thereby changing the locations where the coating is intensively removed. Compared to continuously injecting ions into the same location under constant pressure conditions, this method allows for efficient removal of the coating formed on the peaks and valleys structure of the tool in a shorter time, while also reducing power consumption.

[0011] A specific embodiment of the coating removal method is one in which the thickness of the plasma sheath formed around the tool in the high-pressure plasma treatment step relative to the valleys is smaller than the thickness of the plasma sheath formed in the low-pressure plasma treatment step relative to the valleys.

[0012] The aforementioned coating removal method is preferably performed by switching between the high-pressure plasma treatment step and the low-pressure plasma treatment step two or more times. When switching between high-pressure plasma treatment and low-pressure plasma treatment processes once each, there is a risk that coating components removed and scattered during the subsequent plasma treatment process may re-adhere to the surface of the tool, which was exposed after the first plasma treatment process, and remain without being removed. By switching between high-pressure plasma treatment and low-pressure plasma treatment processes two or more times, it becomes possible to more reliably remove such re-adhered coating components.

[0013] Furthermore, the coating removal method preferably involves performing the plasma treatment using an inductively coupled plasma. In this way, by using high-density plasma, the rate of coating removal can be increased, allowing for more efficient coating removal.

[0014] Furthermore, the present invention relates to a tool coating removal device that removes a coating formed on the surface of a tool having a mountain-valley structure on its surface in which peaks and valleys are arranged alternately, using plasma, and comprises a vacuum vessel in which the tool is placed, a plasma source that generates plasma in the vacuum vessel, and a control device that controls the pressure in the vacuum vessel and performs plasma processing at a predetermined first pressure value, thereby enabling a high-pressure plasma processing mode in which the rate of coating removal at the bottom of the valleys is greater than the rate of coating removal at the edges of the valleys, and a low-pressure plasma processing mode in which the pressure in the vacuum vessel is set to a second pressure value smaller than the first pressure value, thereby enabling plasma processing, thereby enabling the rate of coating removal at the edges of the valleys to be greater than the rate of coating removal at the bottom of the valleys, wherein the control device removes the coating formed on the surface of the tool by switching between the high-pressure plasma processing mode and the low-pressure plasma processing mode one or more times. A coating removal device with such a configuration can achieve the same effects as the coating removal method of the present invention described above. [Effects of the Invention]

[0015] According to the present invention configured in this way, a coating formed on the surface of a tool having a peak-and-valley structure can be efficiently removed using plasma. [Brief explanation of the drawing]

[0016] [Figure 1] A schematic longitudinal cross-sectional view showing the configuration of a coating removal device according to one embodiment of the present invention. [Figure 2] A schematic cross-sectional view showing the configuration of the coating removal device according to the same embodiment. [Figure 3] This figure shows the tool to be processed by the coating removal device of the same embodiment. [Figure 4]It is a diagram for explaining the principle of the film removal method by the film removal apparatus of the same embodiment, and shows the relationship between the plasma density and the plasma sheath surface formed around the tool. [Figure 5] A graph showing the position of the remaining edge of the film when a film removal test is performed under various different conditions. [Figure 6] A graph showing the power amount of the high-frequency power supply when a film removal test is performed under different pressure conditions.

Mode for Carrying Out the Invention

[0017] 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.

[0018] <Device Configuration> The film removal apparatus 100 of the present embodiment removes the film formed on the surface of the tool T by plasma treatment using inductively coupled plasma.

[0019] Specifically, as shown in FIGS. 1 and 2, the film removal apparatus 100 includes a vacuum container 1 that forms a processing chamber S evacuated and into which gas is introduced, an antenna 2 provided outside the vacuum container 1, and a high-frequency power supply 3 that applies a high-frequency wave to the antenna 2. In such a configuration, by applying a high-frequency wave from the high-frequency power supply 3 to the antenna 2, a high-frequency current flows through the antenna 2, an induced electric field is generated in the vacuum container 1, and inductively coupled plasma is generated. In this embodiment, the antenna 2 and the high-frequency power supply 3 that applies a high-frequency wave to the antenna 2 constitute a plasma source.

[0020] The tool T processed by the coating removal device 100 of this embodiment is a so-called coated tool or coated tool, which has a coating (also called a coating film) formed on the surface of a base material made of tool steel or cemented carbide, for example. The coating is formed on the surface of the tool's base material by chemical vapor deposition (CVD) or physical vapor deposition (PVD) for the purpose of improving hardness, wear resistance, or heat resistance, for example. Specific examples of coatings include Ti-based coatings such as TiN coatings and TiAlN coatings, Cr-based coatings such as CrN coatings and AlCrN coatings, and DLC (amorphous hard carbon) coatings. The tool T has a mountain-valley structure Z on the surface of the base material, in which peaks M and valleys V (also called convex and concave parts), such as drill grooves, are arranged alternately, and the coating is formed on the surface of this mountain-valley structure. Specifically, the tool T is preferably a cutting tool such as a drill or end mill, but is not limited to these. The tool T to be processed in this embodiment is a drill having a helical groove structure Z on its surface, as shown in Figure 3.

[0021] The vacuum container 1 is, for example, a metal container, and in this embodiment, it has a cylindrical shape. An opening is formed in the wall of the vacuum container 1 (in this case, the side wall 1a) that penetrates in the thickness direction. This vacuum container 1 is electrically grounded, and the processing chamber S inside it is evacuated by a vacuum exhaust device 4.

[0022] Plasma generation gas is introduced into the vacuum vessel 1, for example, via a flow regulator 11 or one or more gas inlets 12 provided inside the vacuum vessel 1. This plasma generation gas is, for example, a noble gas such as argon, a halogen gas, or a mixture thereof, and may be appropriately changed depending on the material of the coating to be removed. The gas inlets 12 are provided inside the vacuum vessel 1, for example, near the other side wall 1b opposite to the side wall 1a where the opening is formed, and are configured to blow the plasma generation gas sideways toward the opening. Note that the gas inlets 12 are not limited to positions opposite the opening formed in the side wall 1a, but may be provided at any position. In this embodiment, multiple gas inlets 12 are provided along the axial direction (vertical direction) of the vacuum vessel 1.

[0023] As shown in Figures 1 and 2, antenna 2 is positioned to face an opening formed in the vacuum vessel 1. Note that the number of antennas 2 is not limited to one; multiple antennas 2 may be provided. In this embodiment, antenna 2 is rod-shaped and is positioned vertically along the axial direction (up and down) of the vacuum vessel 1.

[0024] Antenna 2 has a feed end 2a connected to a high-frequency power supply 3 via a matching circuit 31, and its other end, the termination 2b, is directly grounded. The termination 2b may also be grounded via a capacitor or coil.

[0025] The high-frequency power supply 3 can supply high-frequency current to the antenna 2 via the matching circuit 31. The high-frequency frequency is, for example, a common 13.56 MHz, but is not limited to this and may be changed as appropriate.

[0026] The coating removal device 100 has a magnetic field-transmitting window W that allows the magnetic field generated from the antenna 2 to pass through. Specifically, the coating removal device 100 includes a slit plate 7 that closes 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 closes a slit formed in the slit plate 7 from the outside of the vacuum container 1. The magnetic field-transmitting window W is formed by the slit plate 7 and the dielectric plate 8.

[0027] The slit plate 7 allows the high-frequency magnetic field generated from the antenna 2 to pass through into the vacuum container 1, while preventing the electric field from entering the vacuum container 1 from the outside. Specifically, the slit plate 7 is a flat, rectangular metal plate with multiple slits that penetrate in the thickness direction and are arranged at equal intervals along the longitudinal direction of the antenna 2.

[0028] The slit plate 7 is larger than the opening of the vacuum vessel in a plan view and closes the opening while being supported by the side wall 1a. A sealing member such as an O-ring or gasket is interposed between the slit plate 7 and the side wall 1a, and the space between them is vacuum-sealed.

[0029] The dielectric plate 8 is provided on the outward-facing surface of the slit plate 7, facing outwards from the vacuum chamber 1, and closes the slits of the slit plate 7. This dielectric plate 8 is a flat plate composed entirely of a dielectric material, such as ceramics like alumina, silicon carbide, or silicon nitride; inorganic materials like quartz glass or alkali-free glass; or resin materials like fluororesin (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, and the space between them is vacuum-sealed.

[0030] With this configuration, when a high frequency is applied from the high-frequency power supply 3 to the antenna 2, the high-frequency magnetic field generated from the antenna 2 passes through the magnetic field transmission window W, which consists of a slit plate 7 and a dielectric plate 8, and is formed (supplied) inside the vacuum vessel 1. As a result, an induced electric field is generated in the space inside the vacuum vessel 1, and an inductively coupled plasma is created.

[0031] The coating removal device 100 is equipped with a tool holder 5 that holds tools T within the vacuum chamber 1. This tool holder 5 is configured to hold multiple tools T and to rotate and move these multiple tools T within the vacuum chamber 1. Specifically, this tool holder 5 comprises a disc-shaped rotary table 51 that rotates within the vacuum chamber 1, a shaft 52 connected to the central axis (rotation axis) of the rotary table 51, and a drive device 53 (specifically a motor) that rotates the shaft 52.

[0032] The rotary table 51 is positioned near the lower wall 1c of the vacuum vessel 1 such that its central axis (axis of rotation) coincides with the axial direction (vertical direction) of the vacuum vessel 1. Multiple (six in this case) holding parts 511 are provided on the upper surface of the rotary table 51 for holding tools T upright with their tips facing upward. The multiple holding parts 511 are positioned so as to be rotationally symmetrical with respect to the central axis of the rotary table 51 when viewed from above or below.

[0033] The shaft 52 is a metal rod with one end connected to the underside of the rotary table 51, and is positioned to align with the axial direction of the vacuum vessel 1. This shaft 52 penetrates the lower wall 1c of the vacuum vessel 1, and one end is connected to a drive unit 53 located outside the vacuum vessel 1. The space between the shaft 52 and the lower wall 1c is sealed by an insulating sealing member.

[0034] The drive unit 53 rotates the shaft 52, causing the rotary table 51 to rotate, which in turn causes the multiple tools T held in the multiple holding parts 511 of the rotary table 51 to rotate around the shaft 52. In this embodiment, the drive unit 53 rotates the shaft 52, causing each holding part 511 itself to rotate on the rotary table 51.

[0035] The coating removal device 100 is equipped with 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 to this. This bias voltage allows control of the energy of positive ions in the plasma when they are incident on the coating on the surface of the tool T, thereby controlling the rate of coating removal.

[0036] The coating removal device 100 is equipped with a control device 9 that controls the conditions for the coating treatment. This control device 9 is a computer that has, for example, an analog electrical circuit having a buffer, an amplifier, etc., a digital electrical circuit having a CPU, memory, or DSP, etc., and an A / D converter interposed between them. The control device 9 performs functions as an antenna power control unit 91, a bias voltage control unit 92, a pressure control unit 93, and a holder control unit 94 by the cooperation of the CPU and its peripheral devices according to a predetermined program stored in memory.

[0037] The antenna power control unit 91 controls the output of the high-frequency power supply 3 and controls the high-frequency current flowing to the antenna 2. The bias voltage control unit 92 controls the bias power supply 6 and controls 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 rate regulator and also controls the pressure inside the processing chamber S by adjusting the opening of a vacuum exhaust valve (not shown) installed on top of the vacuum pump 4. The holder control unit 94 controls the rotation of the rotary table 51 by controlling the drive unit 53.

[0038] In this embodiment, the coating removal device 100 can perform plasma processing in a high-pressure plasma processing mode, where the pressure inside the vacuum vessel 1 is set to a predetermined first pressure value, and in a low-pressure processing mode, where the pressure inside the vacuum vessel 1 is set to a second pressure value lower than the first pressure value, by adjusting the flow rate of the plasma generation gas supplied to the processing chamber S and the opening degree of the vacuum exhaust valve using the pressure control unit 93. The device is configured to perform plasma processing by alternately switching between these two plasma processing modes to remove the coating formed on the surface of the tool T.

[0039] The coating removal apparatus 100 of this embodiment can efficiently remove coatings formed on the peak and valley structure Z of the tool T by switching between a high-pressure processing mode and a low-pressure processing mode, thereby changing the shape of the plasma sheath surface formed between the plasma formed in the processing chamber S and the surface of the tool T.

[0040] The first pressure value is set to a value such that the plasma sheath surface forms 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, this first pressure value is set so that when plasma treatment is performed, the rate of film removal (or ion incidence density) at the bottom V1 of the valley V is greater than the rate of film removal (or ion incidence density) at the edge V2 of the valley V. In the plasma treatment process using the high-pressure plasma treatment mode (also called the high-pressure plasma treatment process), as shown in Figure 4(a), by continuing the plasma treatment at this first pressure value for a predetermined time, the film formed on the bottom V1 of the valley V of the tool T (i.e., the inner region of the valley V) is preferentially removed, and the area where the surface of the substrate is exposed gradually expands from the bottom V1 of the valley V to the edge V2. Figure 4(a) shows a cross-section of the tool T. Figure 4(b) is similar. In this high-pressure plasma treatment process, the rate at which the coating is removed from the bottom V1 of the valley V is greater than the rate at which the coating is removed from the bottom V1 of the valley V in the low-pressure plasma treatment process described later.

[0041] On the other hand, the second pressure value is set such that, compared to the case of the first pressure value, the plasma sheath surface is formed at a position further away from the surface of the tool T (i.e., the plasma sheath is formed thicker), and ions in the plasma are more likely to be incident on the edge V2 of the valley V than on the bottom V1. In other words, this second pressure value is set so that when plasma treatment is performed, the rate of removal of the coating at the edge V2 of the valley V (or the ion incidence density) is greater than the rate of removal of the coating at the bottom V1 of the valley V (or the ion incidence density). In the low-pressure plasma treatment mode (also called the low-pressure plasma treatment process), as shown in Figure 4(b), by continuing the plasma treatment at this second pressure value for a predetermined time, the coating formed on the edge V2 of the valley V of the tool T (i.e., the outer region of the valley V) is preferentially removed, and the area in which the surface of the substrate is exposed gradually expands from the edge V2 of the valley V to the bottom V1. In this low-pressure plasma treatment process, the rate at which the coating is removed from the edges V2 of the valleys V is greater than the rate at which the coating is removed from the edges V2 of the valleys V in the high-pressure plasma treatment process described above.

[0042] The coating removal device 100 preferably removes the coating from the tool T by alternately switching between a high-pressure plasma treatment process and a low-pressure plasma treatment process once or more, preferably twice or more, at predetermined timings. Either the high-pressure plasma treatment process or the low-pressure plasma treatment process may be performed first.

[0043] Furthermore, in the high-pressure plasma processing process and the low-pressure plasma processing process, the amount of high-frequency power supplied to antenna 2 may be the same or different. The amount of high-frequency power supplied to antenna 2 is, for example, 400W to 1000W, but is not limited to this.

[0044] <Effects of this embodiment> According to the coating removal apparatus 100 of this embodiment configured in this way, when removing a coating from a tool T having a mountain-valley structure Z in which peaks M and valleys V, such as spiral grooves, are arranged alternately, in a high-pressure plasma treatment process where the pressure value is relatively high, the thickness of the plasma sheath formed on the surface of the tool T is reduced, thereby increasing the ion incidence density near the inside of the valleys V (bottom V1, etc.) of the mountain-valley structure, allowing for efficient removal of the coating from the bottom V1. On the other hand, in a low-pressure plasma treatment process where the pressure value is relatively low, the thickness of the plasma sheath is increased, thereby increasing the ion incidence density near the outside of the valleys V (edge ​​V2) of the mountain-valley structure Z, allowing for efficient removal of the coating from the edge V2. By combining high-pressure and low-pressure plasma treatment processes, it is possible to change the areas where the ion incidence density is high within the intricate mountain and valley structure of the tool T, thereby changing the areas where the coating is concentrated for removal. Compared to continuously injecting ions into the same area under constant pressure conditions, this method allows for efficient removal of the coating across the entire tool T in a shorter time, while also reducing power consumption.

[0045] <Other modified embodiments> However, the present invention is not limited to the embodiments described above. For example, the coating removal apparatus 100 of the above embodiment 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 it is not limited to this. In other embodiments, the coating removal apparatus 100 may be configured to perform plasma treatment at a third pressure value different from the first and second pressure values, and may perform plasma treatment under three different pressure conditions.

[0046] Furthermore, the coating removal device 100 in the above embodiment was a so-called external antenna type, which generates plasma inside the vacuum container 1 by applying high frequency to an antenna 2 provided outside the vacuum container 1. However, it is not limited to this. In other embodiments, it may be a so-called internal antenna type, which generates plasma by installing the antenna 2 inside the vacuum container 1.

[0047] Furthermore, although the above embodiment uses inductively coupled plasma to perform plasma processing, it is not limited to this. In other embodiments, plasma processing may be performed using plasma generated by other methods, such as capacitively coupled plasma. In other embodiments, the plasma source does not have to be configured using an antenna and a high-frequency power supply.

[0048] In the above embodiment, the tool T was a drill and the peak-and-trench structure Z was a helical groove, but it is not limited to these. In other embodiments, the tool T may be an end mill, hob, or tap, and the peak-and-trench structure Z may be any uneven shape formed on the working part of the tool, such as screw grooves or cutting edges.

[0049] Furthermore, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from its spirit. [Examples]

[0050] The present invention will be described in more detail below with reference to examples. The present invention is not limited by the following examples, and it is certainly possible to implement it with appropriate modifications within the scope that is consistent with the spirit described below, and all such modifications are included within the technical scope of the present invention.

[0051] Using the coating removal apparatus 100 described above, three 4mmφ drills (tool T) were prepared, and coating removal was performed under different plasma treatment conditions (Samples 1-3). In Sample 1, the high-frequency power applied to the antenna 2 was 500W, and the pressure condition inside the vacuum chamber 1 during plasma treatment was 5Pa, and the coating was removed by plasma treatment. In Sample 2, the high-frequency power applied to the antenna 2 was 500W, and the pressure condition inside the vacuum chamber 1 during plasma treatment was 15Pa, and the coating was removed by plasma treatment. In Sample 3, the high-frequency power applied to the antenna 2 was 800W, and the pressure condition inside the vacuum chamber 1 during plasma treatment was 5Pa, and the coating was removed by plasma treatment. The results are shown in Figure 5. The vertical axis in Figure 5 indicates the position of the remaining edge of the coating on the tool during plasma treatment (i.e., the boundary position between the exposed tool surface and the coating).

[0052] As shown in Figure 5, when sample 1 was plasma-treated with a pressure of 5 Pa in the vacuum vessel 1, the position of the remaining edge of the coating moved from the outside (edge ​​V2) to the inside (bottom V1) of the valley V over time, confirming that the coating was being removed sequentially from the outside of the valley V. On the other hand, in sample 2, which was plasma-treated with a pressure of 15 Pa in vacuum vessel 1, the position of the remaining end moved from the inside (bottom V1) to the outside (edge ​​V2) of the valley V over time, confirming that the coating was being removed sequentially from the inside of the valley V. Furthermore, in sample 3, which was plasma-treated with a vacuum chamber 1 pressure of 5 Pa and a high-frequency power of 800 W, it was confirmed that the position of the remaining edge moved from the outside (edge ​​V2) to the inside (bottom V1) of the valley V over time, and that the coating was being removed sequentially from the outside of the valley V. It was confirmed that sample 3 could remove the coating faster than sample 1, which had the same pressure conditions but lower high-frequency power. Furthermore, it was confirmed that under any of the conditions, continuous processing could completely remove the coating formed on the surface of the valley V.

[0053] Figure 6 shows the relationship between the amount of high-frequency power required for coating when plasma processing is performed under a single pressure condition (high-frequency power of 800W and pressure inside the vacuum chamber of 5Pa) and the amount of high-frequency power required for coating when plasma processing is performed by switching between high pressure (500W, 15Pa) and low pressure (500W, 5Pa). As can be seen from Figure 6, it was confirmed that switching the pressure conditions can reduce the amount of high-frequency power used by up to 15%, thereby improving efficiency. [Industrial applicability]

[0054] According to the coating removal apparatus of the present invention configured in this way, coatings formed on the surface of a tool having a peak-and-valley structure can be efficiently removed using plasma. [Explanation of Symbols]

[0055] 100...Film removal equipment 1...vacuum container 2... Antenna 3...High frequency power supply 5 ···Tool holder 9 ···Control device T...Tools Z...Mountain-valley structure V...Tanibe V1...Bottom V2...Edge M ···Yamabe

Claims

1. A method for removing a coating formed on the surface of a tool having a surface with alternating peaks and valleys, wherein plasma is generated in a vacuum vessel in which a tool is placed, and the coating is removed by plasma treatment using the plasma, A high-pressure plasma treatment step is performed by setting the pressure inside the vacuum vessel to a predetermined first pressure value and making the rate of removal of the coating at the bottom of the valley greater than the rate of removal of the coating at the edge of the valley. A coating removal method comprising performing plasma treatment by setting the pressure inside the vacuum vessel to a second pressure value smaller than the first pressure value, thereby performing a low-pressure plasma treatment step, and switching between these steps once or more times, to make the coating removal speed at the edges of the valleys greater than the coating removal speed at the bottom of the valleys.

2. The coating removal method according to claim 1, wherein the thickness of the plasma sheath formed around the tool in the high-pressure plasma treatment step relative to the valleys is smaller than the thickness of the plasma sheath formed in the low-pressure plasma treatment step relative to the valleys.

3. The method for removing a coating according to claim 1, wherein the high-pressure plasma treatment step and the low-pressure plasma treatment step are switched between two or more times.

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

5. A coating removal device that uses plasma to remove a coating formed on the surface of a tool having a surface structure with alternating peaks and valleys, The vacuum container in which the aforementioned tool is placed A plasma source that generates plasma inside the vacuum vessel, Control the pressure inside the vacuum container, A high-pressure plasma treatment mode is performed by setting the pressure inside the vacuum vessel to a predetermined first pressure value and making the rate of removal of the coating at the bottom of the valley greater than the rate of removal of the coating at the edge of the valley. A control device that switches between a low-pressure plasma processing mode, in which plasma processing is performed with the pressure inside the vacuum vessel set to a second pressure value lower than the first pressure value, and the rate of removal of the coating at the edge of the valley is greater than the rate of removal of the coating at the bottom of the valley, Equipped with, A coating removal device that removes a coating formed on the surface of a tool by switching the control device between a high-pressure plasma processing mode and a low-pressure plasma processing mode one or more times.

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