Film formation method

Abstract

A film formation method according to one non-limiting aspect of the present disclosure comprises: a first step for preparing a film formation jig in which a holder having a plate-shaped body rotatable around a first central axis and a plurality of holding parts provided at equal intervals in the circumferential direction around the first central axis on an upper surface of the body and capable of holding a rod-shaped tool is laminated in two or more stages at intervals in the direction along the first central axis; a second step for accommodating the film formation jig inside a vacuum chamber in a state in which the tool is held by each of the plurality of holding parts; and a third step for forming a coating layer on the surface of the tool by a physical vapor deposition method while rotating the body around the first central axis. With L (mm) being the outer diameter of the tool and D (mm) being the distance from the tip of the tool to the lower surface of the body positioned above the tool, L and D are related such that D is greater than 1.5 L and smaller than 1.5 L +40, and D > 15.

Description

Film forming method

[0001] The present disclosure relates to a film formation method.

[0002] Physical vapor deposition (PVD) is a known method for forming a coating layer on the surface of a tool (substrate), and a PVD processing apparatus that performs film formation using the PVD method is also known.

[0003] For example, International Publication No. 2014 / 147979 (Patent Document 1) describes a PVD processing apparatus that includes a vacuum chamber that accommodates a plurality of substrates, a revolution table that is provided within the vacuum chamber and that supports the plurality of substrates while causing these substrates to revolve around an axis of revolution, a plurality of rotation tables that support each of the plurality of substrates and rotate the substrate on the revolution table around an axis of rotation that is parallel to the axis of revolution, a plurality of targets formed from different types of film formation materials, and a table rotation mechanism that rotates each rotation table around its axis of rotation as the revolution table rotates.

[0004] A non-limiting one-sided film formation method of the present disclosure includes: a first step of preparing a film formation jig in which holders, each holder having a plate-shaped main body rotatable about a first central axis and a plurality of holding portions provided on an upper surface of the main body at equal intervals in a circumferential direction of the first central axis and capable of holding a rod-shaped tool, are stacked in two or more stages at intervals along the first central axis; a second step of housing the film formation jig inside a vacuum chamber with the tool held by each of the plurality of holding portions; and a third step of forming a film on a surface of the tool by physical vapor deposition while rotating the main body about the first central axis. When the outer diameter of the tool is L (mm) and the distance from the tip of the tool to the underside of the main body located above it is D (mm), L and D satisfy the relationship D = 1.5L and D = 1.5L + 40, and D > 15.

[0005] FIG. 6 is a side view showing a film formation jig used in the non-limiting one-surface film formation method of the present disclosure. FIG. 7 is a plan view of a holder in the film formation jig shown in FIG. 1. FIG. 8 is a plan view showing a PVD processing apparatus used in the non-limiting one-surface film formation method of the present disclosure. FIG. 9 is a side view of a film formation jig and a table in the PVD processing apparatus shown in FIG. 3. FIG. 10 is a cross-sectional view showing a part of a film formation jig (holder) used in the non-limiting one-surface film formation method of the present disclosure. FIG. 11 is a cross-sectional view showing a part of a film formation jig (holder) used in the non-limiting one-surface film formation method of the present disclosure. FIG. 12 is an enlarged view of the periphery of a holding pin in the film formation jig (holder) shown in FIG. 13. FIG. 14 is a side view showing a film formation jig used in the non-limiting one-surface film formation method of the present disclosure.

[0006] The non-limiting one-surface film formation method of the present disclosure will be described in detail below with reference to the drawings. However, for the sake of convenience, the figures referred to below show only the main components necessary for explaining the embodiment in a simplified form. Furthermore, the dimensions of the components in each figure do not faithfully represent the dimensions of the actual components or the dimensional ratios of each component. Note that, for ease of visual understanding, FIG. 4 omits the film formation jig and other components that overlap with the third central axis when viewed from the side.

[0007] The film forming method may be a method of forming a coating layer on the surface of a rod-shaped tool 201 (see FIG. 1). The tool 201 having a coating layer formed on its surface may also be called a coated tool. The coating layer may also be called a coating film. The coating layer may also be called a film.

[0008] The rod-shaped tool 201 on which the film is formed may be a cutting tool, such as a drill, an end mill, or a reamer.

[0009] The rod-shaped cutting tool may have a shank portion and a cutting portion. The shank portion may be a portion that is gripped by a rotating spindle of a machine tool. The shank portion may be designed according to the shape of the spindle of the machine tool. The cutting portion may be a portion that can come into contact with a workpiece and plays a major role in cutting the workpiece. The cutting portion may be a portion that has a cutting edge.

[0010] Examples of materials for the tool 201 include cemented carbide and cermet. Examples of cemented carbide compositions include WC-Co, WC-TiC-Co, and WC-TiC-TaC-Co. WC, TiC, and TaC may be hard particles, and Co may be a binder phase. Cermet may be a sintered composite material in which a ceramic component is combined with a metal. An example of a cermet is a titanium compound mainly composed of TiC or TiN.

[0011] The composition of the coating layer formed on the surface of the tool 201 may include, for example, titanium aluminum nitride (TiAlN), titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina (Al2O3).

[0012] The coating layer is not limited to a specific thickness. For example, the average thickness of the coating layer may be set to about 0.1 to 12 μm. The thickness of the coating layer may be measured by cross-sectional observation using an electron microscope. For example, the thickness may be measured at 10 or more measurement points at any position on the coating layer, and the average value may be calculated. Examples of electron microscopes include scanning electron microscopes (SEM) and transmission electron microscopes (TEM).

[0013] The method for forming a coating layer on the surface of the tool 201 may include first to third steps. Each step will be described below in order.

[0014] In the first step, a film formation jig 1 may be prepared. The film formation jig 1 may have a holder 3, as shown in a non-limiting example in Figures 1 and 2. The holder 3 may have a main body 5 and a holding portion 7.

[0015] The main body 5 may be a plate-like member that can rotate around the first central axis O1. A motor, gears, or the like may be used to rotate the main body 5. That is, the driving force of the motor may be transmitted to the main body 5 via gears to rotate the main body 5. This also applies to other rotatable members such as a table, which will be described later. The arrow Y1 in FIG. 1 and other figures may indicate the direction of rotation of the main body 5. Note that the main body 5 may rotate in the direction opposite to the arrow Y1.

[0016] The main body 5 may be disk-shaped, and the outer diameter of the main body 5 may be set to, for example, about 100 to 200 mm.

[0017] The holding portion 7 is capable of holding a rod-shaped tool 201. As shown in a non-limiting example in FIG. 1 , the holding portion 7 is capable of holding the rod-shaped tool 201 in a state where a tip 201 a of the rod-shaped tool 201 is exposed.

[0018] Furthermore, there may be a plurality of holding parts 7. The plurality of holding parts 7 may be provided at equal intervals in the circumferential direction of the first central axis O1 on the upper surface 9 of the main body 5, as in a non-limiting example shown in Figure 2. The number of holding parts 7 in one main body 5 may be, for example, about 4 to 36. The number of holding parts 7 may be the same as the number of tools 201 used for film formation.

[0019] 1, the film formation jig 1 may be a member in which holders 3 are stacked in two or more stages at intervals in the direction along the first central axis O1. The number of holders 3 may be, for example, about 2 to 6. The holders 3 may be stacked in a state where they are attached to supports 11 extending along the first central axis O1.

[0020] In the second step, the film formation jig 1 may be housed inside the vacuum chamber 13 with the tool 201 held by each of the multiple holders 7 (see FIG. 3).

[0021] The inside of the vacuum chamber 13 can be depressurized. For example, an exhaust pipe may be connected to the vacuum chamber 13, and a vacuum pump or the like may be connected to the exhaust pipe to evacuate the inside to a vacuum or extremely low pressure. Alternatively, a gas supply pipe may be connected to the vacuum chamber 13 to supply an inert gas, a reactive gas, or the like into the vacuum chamber 13.

[0022] In the third step, a coating layer may be formed on the surface of the tool 201 by a PVD method while rotating the main body 5 around the first central axis O1. Examples of the PVD method include an ion plating method and a sputtering method. The deposition time may be set to 0.1 to 100 minutes. After the third step, a coated tool is obtained in which a coating layer is formed on the surface of the rod-shaped tool 201.

[0023] 1 , the outer diameter of the tool 201 may be L (mm), and the distance from the tip 201a of the tool 201 to the underside 15 of the main body 5 located above it may be D (mm). L and D may be greater than D=1.5L and less than D=1.5L+40, and may satisfy the relationship D>15.

[0024] In these cases, the film formation rate is likely to improve. Furthermore, the uniformity of the formed film is likely to improve. Specifically, the thickness of the formed film can be controlled between 0.1 and 12.0 μm depending on the film specifications. Furthermore, the variation in the formed film can be controlled to within ±1.0 μm. When the film thickness is thin (for example, 0.1 to 0.5 μm), this variation can be controlled to within ±0.05 μm.

[0025] Furthermore, in the above case, the multiple holding portions 7 of the film formation jig 1 allow many tools 201 to be accommodated inside the vacuum chamber 13, making it easy to optimize the capacity. As long as L and D satisfy the above relationship, the outer diameters of the multiple tools 201 may be the same or different. From this perspective, it is also easy to optimize the capacity. Therefore, the above film formation method has excellent film formation properties.

[0026] The outer diameter L of the tool 201 may be set to, for example, 0.1 to 35 mm. If the tool 201 is a cutting tool, the outer diameter of the tool 201 may be the maximum outer diameter of the cutting portion. Furthermore, D may be set to a value greater than 15 mm and smaller than 92.5 mm. The tip 201a of the tool 201 may be the tip of the cutting portion. The holding portion 7 is capable of holding the shank portion in a state where the cutting portion is exposed. Note that, when the length of the cutting portion in the longitudinal direction of the cutting tool is N (mm), N may be set to N = 1L to 20L.

[0027] L and D may have a relationship of 18<D<32 when L<7.0, a relationship of 18<D<52 when 7.0≦L≦11.0, and a relationship of 38<D<52 when 11.0<L. In these cases, it is possible to control the variation in the deposited film to within ±0.8 μm.

[0028] L and D may be greater than D = 2.0L + 6 and less than D = 2.0L + 32, and may satisfy the relationship 18 < D < 52. In these cases, it is possible to control the variation in the deposited film to within ±0.8 μm.

[0029] 1 , the film forming jig 1 may further include a top plate 17. The top plate 17 may be located above the uppermost holder 3 among the multiple holders 3. When the film forming jig 1 includes the top plate 17, the lower surface 19 of the top plate 17 may be regarded as the lower surface 15 of the main body 5. Furthermore, the tool 201 located directly below the top plate 17 and the top plate 17 may have the above-described relationship of L and D.

[0030] That is, the outer diameter of the tool 201 may be L (mm), and the distance from the tip 201a of the tool 201 to the underside 19 of the top plate 17 located above it may be D (mm). These L and D may be greater than 1.5L and less than 1.5L + 40, and satisfy the relationship D > 15. Furthermore, when L < 7.0, L and D may satisfy the relationship 18 < D < 32; when 7.0 ≦ L ≦ 11.0, they may satisfy the relationship 18 < D < 52; and when 11.0 < L, they may satisfy the relationship 38 < D < 52. L and D may be greater than 2.0L + 6 and less than 2.0L + 32, and satisfy the relationship 18 < D < 52.

[0031] The top plate 17 may be disk-shaped. The outer diameter of the top plate 17 may be set to, for example, about 100 to 200 mm. The top plate 17 may be attached to the support 11.

[0032] The plurality of holding units 7 may be cylindrical and extend along the second central axis O2, as in the non-limiting example shown in FIG. 1 . The second central axis O2 may be parallel to the first central axis O1. In these cases, more uniform film formation is possible. The holding units 7 may be cylindrical. The cylindrical shape of the holding units 7 may also be referred to as a cylindrical shape with a bottom.

[0033] In the first step, a table 21 may be further prepared (see FIGS. 3 and 4). The table 21 may be a member that can rotate about a third central axis O3 parallel to the first central axis O1. The arrow Y2 in FIG. 3 and other figures may indicate the rotation direction of the table 21. Note that the table 21 may rotate in the direction opposite to the arrow Y2.

[0034] 3, the film formation jig 1 may be provided on the outer periphery of the third central axis O3 on the upper surface 23 of the table 21. In the second step, the film formation jig 1 may be housed inside the vacuum chamber 13 together with the table 21. In the third step, the table 21 may be rotated around the third central axis O3. In these cases, more uniform film formation is possible.

[0035] 3, multiple film-forming jigs 1 may be provided at equal intervals on the upper surface 23 of the table 21 in the circumferential direction of the third central axis O3. When multiple film-forming jigs 1 are provided, the number of film-forming jigs 1 may be, for example, about 2 to 6. Furthermore, the table 21 may be disk-shaped with an outer diameter larger than that of the main body 5 of the holder 3. The outer diameter of the table 21 may be set to, for example, about 300 to 600 mm.

[0036] The table 21 may also be called a revolution table 21. The third central axis O3 may also be called a revolution axis. When the table 21 is called a revolution table, the film forming jig 1 (main body 5) may also be called a rotation table. The first central axis O1 may also be called a rotation axis.

[0037] The film formation method may use a PVD processing apparatus 101 that performs film formation using a PVD method. As a non-limiting example shown in Fig. 3, the PVD processing apparatus 101 may include a film formation jig 1, a table 21, a target 103, and a vacuum chamber 13. The vacuum chamber 13 may accommodate the target 103 therein in addition to the film formation jig 1 and the table 21.

[0038] The target 103 may be located outside the table 21. Alternatively, the target 103 may be located radially outside the table 21. The target 103 may be located on the inner wall surface of the vacuum chamber 13.

[0039] The target 103 may be formed from a film-forming material that is a raw material for the coating layer. The target 103 may also be called an evaporation source or a vapor deposition source. The target 103 may be in the form of a plate.

[0040] There may be a plurality of targets 103. The plurality of targets 103 may be formed from different types of film formation materials or may be formed from the same type of film formation material. The plurality of targets 103 may be positioned at intervals in the direction along the third central axis O3.

[0041] Furthermore, the multiple targets 103 may be positioned at intervals along the circumferential direction of the table 21. For example, when there are two targets 103, the two targets 103 may be positioned so as to face each other with the table 21 therebetween. When there are multiple targets 103, the number of targets 103 may be, for example, about 2 to 16.

[0042] The above provides examples of the non-limiting film formation method of the present disclosure, but it goes without saying that the present disclosure is not limited to the above embodiments and can be any method as long as it does not deviate from the gist of the present disclosure.

[0043] Next, a non-limiting film formation method for another surface of the present disclosure will be described with reference to the drawings. Below, differences from the above-described film formation method will be mainly described, and detailed description of the same configuration as the above-described film formation method may be omitted. Therefore, the description of the above-described film formation method may be used to understand the configuration of the film formation method for another surface. This also applies to the film formation method for yet another surface described below.

[0044] In another method for forming a film on one surface, a film forming jig 1A may be used. The film forming jig 1A may have a cylindrical holding portion 7, as shown in non-limiting examples in Figures 5 to 7. The holding portion 7 may also be cylindrical.

[0045] The holder 3 may further have a retaining pin 27. The retaining pin 27 may extend from the top surface 9 of the main body 5. The retaining pin 27 may be inserted into the retaining portion 7. The retaining pin 27 may be a member that retains the retaining portion 7. The retaining pin 27 may be fixed to the top surface 9 of the main body 5. The retaining pin 27 may be cylindrical. There may be multiple retaining pins 27. The number of retaining pins 27 may be the same as the number of retaining portions 7.

[0046] The tool 201 and the holder 7 are tiltable relative to the main body 5. In this case, resistance when the tool 201 and the holder 7 rotate relative to the main body 5 tends to be small.

[0047] The film formation method may satisfy the following conditional formula (I): (h + √(h^2 - 4(D1 + d)(δ - d))) / 2(D1 + d) < D1 / H (I) where h is the height of the holding pin 27. D1 is the thickness of the wall portion 25 in the holding portion 7. d is the width of the holding pin 27. δ is the inner diameter of the holding portion 7. H is the amount of protrusion of the tool 201 from the holding portion 7.

[0048] If conditional formula (I) is satisfied, the tool 201 and the holder 7 are unlikely to come into contact with the adjacent tool 201 when they are inclined relative to the main body 5. In other words, contact between the adjacent tools is easily avoided. Therefore, the tool 201 is unlikely to be damaged.

[0049] Conditional formula (I) will be specifically described below. Figures 6 and 7 show a state in which the tool 201 and the holder 7 are inclined at the maximum angle relative to the main body 5. In other words, Figures 6 and 7 show a state in which the tool 201 and the holder 7 are inclined at the maximum angle of inclination θ relative to the main body 5.

[0050] 7 may have the following relationships: h = h1 + h2 + h3 (1), δ = δ1 + δ2 (2), sin θ = h1 / D1, sin θ = h2 / δ1, sin θ = δ2 / h3, cos θ = d / δ1 (3).

[0051] From (3), h1 / D1 = h2 / δ1 = δ2 / h3 ・・・(4)

[0052] From (1) and (4), h = h1 + h2 + h3 = h1 + (δ1 / D1)h1 + (δ2D1)(1 / h1) = D1sinθ + (δ1 / D1)D1sinθ + (δ2D1)(1 / D1sinθ) = D1sinθ + δ1sinθ + δ2 / sinθ ・・・(5)

[0053] From (2) and (3), δ1 = d / cosθ, δ2 = δ - δ1 = δ - d / cosθ ・・・(6)

[0054] From (5) and (6), h = D1sinθ + δ1sinθ + δ2 / sinθ = D1sinθ + (d / cosθ)sinθ + (δ - d / cosθ) / sinθ = D1sinθ + dsinθ / cosθ + δ / sinθ - d / (sinθcosθ) ・・・(7)

[0055] In an actual device, θ and φ are small. In equation (7), they can be approximated as sinθ ≈ θ and cosθ ≈ 1 (Taylor expansion). φ shown in Figure 5 is the ratio between H and D1, and is tanφ = D1 / H. Regarding φ, they can be approximated as tanφ ≈ φ (Taylor expansion).

[0056] From (7), h ≒ D1sinθ + dsinθ / cosθ + δ / sinθ - d / (sinθcosθ) = D1θ + dθ + δ / θ - d / θ = (D1 + d)θ + (δ - d) / θ ・・・(8)

[0057] If the larger solution of θ in (8) is θ+ and the smaller one is θ-, then θ+ = (h + √(h^2 - 4(D1 + d)(δ - d))) / 2(D1 + d) ・・・(9)

[0058] When θ- < θ+ < φ, contact between the tools can be avoided, so the following conditional expression is derived: (h + √(h^2 - 4(D1 + d)(δ - d))) / 2(D1 + d) = θ+ < φ = D1 / H ⇒ (h + √(h^2 - 4(D1 + d)(δ - d))) / 2(D1 + d) < D1 / H ... (I).

[0059] The outer diameter L of the tool 201 may be the same as the inner diameter δ of the holding portion 7. Note that L and δ do not need to be exactly the same. For example, L may be about 5% smaller than δ.

[0060] Next, still another non-limiting method for forming a film on one surface according to the present disclosure will be described with reference to the drawings.

[0061] In yet another method for forming a film on one surface, a film forming jig 1B may be used. As a non-limiting example shown in FIG. 8 , the film forming jig 1B may have an outer diameter L of the tools 201 that is larger than the interval W between adjacent tools 201. In this case, film formation properties are likely to be improved.

[0062] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to the following examples.

[0063] [Sample No. 1-1] A coating layer was formed on the surface of a rod-shaped tool. The film formation conditions were as follows: Number of holding parts per body: 28 Number of stacked holders: 3 Number of film formation jigs: 4 PVD method: arc ion plating Tool: drill Composition of coating layer: TiAlN Average thickness of coating layer: 4.0 μm Film formation time: 40 minutes L: 12 mm D: 19 mm Other than the above, the conditions were as shown in FIGS. 1 to 7.

[0064] As a result of the film formation, the film formation rate was good and the uniformity of the formed film was also good. Specifically, the variation of the formed film was able to be controlled within ±1.0 μm. Furthermore, the capacity was also optimized. Therefore, it can be said that the above film formation method has excellent film formation properties.

[0065] [Sample No. 1-2] A coating layer was formed on the surface of a rod-shaped tool under the same conditions as Sample No. 1-1, except that the value of D was changed from 19 mm to 57 mm. As a result, the coating rate was good and the uniformity of the formed film was also good. Specifically, the variation in the formed film could be controlled within ±1.0 μm.

[0066] [Sample Nos. 2-1 to 2-3] A coating layer was formed on the surface of a rod-shaped tool under the same conditions as Sample No. 1-1 described above, except that L and D were set to the following values. As a result, the deposition rate was good for all samples, and the uniformity of the deposited film was also good. Specifically, the variation in the deposited film was able to be controlled to within ±0.8 μm. (Sample No. 2-1) L: 1.0 mm D: 20.0 mm (Sample No. 2-2) L: 10.0 mm D: 30.0 mm (Sample No. 2-3) L: 25.0 mm D: 50.0 mm

[0067] In addition, for Samples No. 2-1 to 2-3, when L and D are in the range of L<7.0, the relationship is 18<D<32, when 7.0≦L≦11.0, the relationship is 18<D<52, and when 11.0<L, the relationship is 38<D<52.

[0068] [Sample Nos. 3-1 to 3-3] A coating layer was formed on the surface of a rod-shaped tool under the same conditions as Sample No. 1-1 described above, except that L and D were set to the following values. As a result, the deposition rate was good for all samples, and the uniformity of the deposited film was also good. Specifically, the variation in the deposited film was able to be controlled within ±0.8 μm. (Sample No. 3-1) L: 6.0 mm D: 20.0 mm (Sample No. 3-2) L: 10.0 mm D: 30.0 mm (Sample No. 3-3) L: 10.0 mm D: 50.0 mm

[0069] In addition, in Samples No. 3-1 to 3-3, L and D are greater than D=2.0L+6 and smaller than D=2.0L+32, and the relationship is 18<D<52.

[0070] DESCRIPTION OF SYMBOLS 1... Film formation jig (rotation table) 3... Holder 5... Main body 7... Holding part 9... Upper surface 11... Support 13... Vacuum chamber 15... Lower surface 17... Top plate 19... Lower surface 21... Table (revolution table) 23... Upper surface 25... Wall part 27... Holding pin 101... PVD processing apparatus 103... Target 201... Tool 201a... Tip O1... First central axis (rotation axis) O2... Second central axis O3... Third central axis (revolution axis)

Claims

1. A film-forming method comprising: a first step of preparing a film-forming jig in which a holder is stacked in two or more stages at intervals in a direction along the first central axis, the holder having: a plate-shaped main body rotatable about a first central axis; and a plurality of holding parts arranged at equal intervals on an upper surface of the main body in a circumferential direction of the first central axis and capable of holding a rod-shaped tool; a second step of housing the film-forming jig inside a vacuum chamber with the tool held by each of the plurality of holding parts; and a third step of forming a coating layer on a surface of the tool by physical vapor deposition while rotating the main body about the first central axis, wherein, when an outer diameter of the tool is L (mm) and a distance from a tip of the tool to an underside of the main body located above it is D (mm), L and D are greater than D = 1.5L and smaller than D = 1.5L + 40, and the relationship D > 15 is satisfied.

2. The film forming method according to claim 1, wherein L and D have a relationship of 18<D<32 when L<7.0, a relationship of 18<D<52 when 7.0≦L≦11.0, and a relationship of 38<D<52 when 11.0<L.

3. The film forming method according to claim 1, wherein L and D are greater than D=2.0L+6 and smaller than D=2.0L+32, and the relationship 18<D<52 is satisfied.

4. A film forming method according to any one of claims 1 to 3, wherein the plurality of holding portions are cylindrical and extend along a second central axis, and the second central axis is parallel to the first central axis.

5. A film formation method according to any one of claims 1 to 4, further comprising: in the first step, providing a table rotatable around a third central axis parallel to the first central axis; and providing the film formation jig on the upper surface of the table on the outer circumferential side of the third central axis; in the second step, housing the film formation jig together with the table inside the vacuum chamber; and in the third step, rotating the table around the third central axis.

6. The film forming method according to any one of claims 1 to 5, wherein the holding portion is cylindrical, the holder extends from the top surface of the main body and further has a holding pin inserted into the holding portion, the tool and the holding portion are tiltable with respect to the main body, and the following conditional formula (I) is satisfied: (h + √(h^2 - 4(D1 + d)(δ - d))) / 2(D1 + d) < D1 / H ... (I), where h is the height of the holding pin, D1 is the thickness of the wall of the holding portion, d is the width of the holding pin, δ is the inner diameter of the holding portion, and H is the amount of protrusion of the tool from the holding portion.

7. A film forming method according to any one of claims 1 to 6, wherein the outer diameter of the tool is larger than the interval between adjacent tools.

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