Surface treatment method

Abstract

To provide a surface treatment method capable of uniformly and rapidly performing plasma treatment over a large area.SOLUTION: A high-density plasma is generated on a portion of a to-be-treated surface of an object by a high-density plasma generation element positioned away from the to-be-treated surface. Plasma treatment is then performed on the entire to-be-treated surface by rotating or moving the object relative to the high-density plasma generation element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a surface treatment method. [Background technology]

[0002] Plasma treatment is used as a method for treating the surfaces of various materials. Patent Document 1 discloses a method for plasma treatment of the surface of the material by generating a discharge between an electrically conductive material to be treated and an electrode and using a treatment gas that has been converted into plasma by the discharge. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-115616 Summary of the Invention [Problem to be solved by the invention]

[0004] Plasma treatment using DC glow discharge does not have a high treatment speed, and from the perspective of improving productivity, a surface treatment method with a higher treatment speed is desired. To increase the treatment speed of plasma treatment, a method using high-density plasma has been proposed. However, it is difficult to generate high-density plasma uniformly over a large area, making it difficult to apply to large surface treatment objects.

[0005] An object of the present disclosure is to provide a surface treatment method that can perform plasma treatment uniformly and quickly over a large area. [Means for solving the problem]

[0006] A surface treatment method according to an embodiment of the present disclosure includes: generating high-density plasma on a portion of the surface to be treated by a high-density plasma generating element provided at a position away from the surface to be treated of the object; The object is rotated or moved relative to the high-density plasma generating element to perform plasma treatment on the entire surface of the object to be treated. [Effects of the Invention]

[0007] According to the surface treatment method of the present disclosure, plasma treatment can be performed uniformly and quickly over a large area. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating an example of a surface treatment apparatus for carrying out a surface treatment method according to an embodiment of the present disclosure. [Figure 2] FIG. 10 is a schematic diagram illustrating an example of a surface treatment apparatus for carrying out a surface treatment method according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, specific embodiments of the surface treatment method of the present disclosure will be described with reference to the drawings.

[0010] [Surface treatment equipment] First, the configuration of a surface treatment apparatus for carrying out the surface treatment method of the present disclosure will be described. Fig. 1 is a schematic diagram of a surface treatment apparatus 101, which is an example of an apparatus for carrying out the surface treatment method of the present disclosure. As shown in Fig. 1, the surface treatment apparatus 101 includes a chamber 10, a fixed rod 20, a moving mechanism 30, a bias power supply 40, and a microwave introduction element 50. Fig. 1 shows a state in which an object W to be surface treated is placed inside the chamber 10.

[0011] The chamber 10 includes an inner wall 11, a gas inlet 12, and a gas outlet 13. Various gases can be introduced into the chamber 10 through the gas inlet 12, and the gases can be discharged from the gas outlet 13. An MFC (Mass Flow Controller, not shown) for adjusting the gas flow rate may be provided upstream of the gas inlet 12. A vacuum pump, not shown, for reducing the pressure inside the chamber 10 may be provided downstream of the gas outlet 13.

[0012] The fixing rod 20 is a rod for fixing the object W inside the chamber 10, and fixes the object W using a fixing device (not shown). In the example shown, the fixing rod 20 is a rod-shaped member extending in the vertical direction. The fixing rod 20 is inserted into the chamber 10 from above. The object W is fixed to the lower end of the fixing rod 20. The upper end of the fixing rod 20 is fixed to the moving mechanism 30 outside the chamber 10.

[0013] The moving mechanism 30 moves the object W. In the illustrated example, the moving mechanism 30 is provided outside the chamber 10. The moving mechanism 30 moves the object W via the fixed rod 20. The moving mechanism 30 is connected to the fixed rod 20 and can move the fixed rod 20 in the vertical direction (in the direction of arrow A1) and rotate it around a vertical axis (in the direction of arrow A2). By moving or rotating the fixed rod 20 with the moving mechanism 30, the object W fixed to the fixed rod 20 can be moved or rotated. The moving mechanism 30 can be configured, for example, by combining a rotary motor and a linear actuator. The operation of the moving mechanism 30 is controlled, for example, by a control device not shown.

[0014] The bias power supply 40 is a DC power supply for applying a voltage between the inner wall 11 of the chamber 10 and the object W. For example, by setting the object W to a negative potential and the inner wall 11 to the ground, plasma can be generated in the chamber 10 by glow discharge.

[0015] The microwave introduction element 50 introduces microwaves into the chamber 10. The microwave introduction element 50 includes a microwave oscillator 51, a waveguide 52, a quartz window 53, and an electrode 54. Specifically, the microwave introduction element 50 can transmit microwaves emitted from the microwave oscillator 51 to the electrode 54 via the waveguide 52 and the quartz window 53. As shown in FIG. 1, the electrode 54 is a plate-shaped electrode in contact with the quartz window 53 and is disposed so as to face the target object W. The electrode 54 is an example of a high-density plasma generation element of the present disclosure. As shown in FIG. 1, the electrode 54 is disposed in a position not in contact with the target object W but in close proximity to the target object W. Typically, the electrode 54 and the target object W are electrically connected so as to be at the same potential. The frequency of the microwaves emitted by the microwave introduction element 50 can be, for example, 2.45 GHz, but is not particularly limited as long as it is an industrially applicable frequency.

[0016] The object W may be, for example, a metal material, but is not particularly limited thereto, and any material may be used, regardless of whether it is conductive or not. The shape of the object W is not particularly limited, and may be, for example, a cylindrical, columnar, plate-like, rectangular tube-like, rectangular column-like, spherical, or a three-dimensional object with a complex surface shape. In this embodiment, the object W will be described as a cylindrical metal member.

[0017] The object W has a treatment target surface S on which surface treatment is to be performed. In the example shown in FIG. 1 , the treatment target surface S of the object W is the outer surface, but the treatment target surface S can be selected arbitrarily. The treatment target surface S may be the entire surface of the object W, or a part of the surface. For example, the treatment target surface S may be the inner surface of a cylindrical object W, or may be both the inner and outer surfaces. If the object W is plate-shaped, one or both main surfaces of the object W may be the treatment target surface S. The treatment target surface S may be a curved surface or a flat surface. In the present disclosure, the treatment target surface S refers to a portion intended to be treated by high-density plasma, which will be described later, and does not include portions not intended to be treated by high-density plasma.

[0018] [Plasma surface treatment] 1 is an apparatus for using plasma to treat a treatment target surface S of a target object W. An overview of surface treatment using plasma will be described below.

[0019] The inner wall 11 of the chamber 10 is conductive, and plasma can be generated by applying a predetermined voltage between the object W to be processed and the inner wall 11. More specifically, plasma is generated within the chamber 10 by setting the pressure within the chamber 10 at a low pressure of approximately 0.1 Pa to 100 Pa and applying a voltage between the object W and the inner wall 11 of the chamber 10 using the bias power supply 40 to induce glow discharge. In the present disclosure, the plasma generated between the object W to be processed and the inner wall 11 of the chamber 10, which is grounded as described above, is referred to as "DC discharge plasma," and is distinguished from "high-density plasma," which will be described later.

[0020] The type of surface treatment performed by the surface treatment method of the present disclosure is not particularly limited, and various surface treatments that can be typically performed using plasma can be performed, such as film formation, oxidation treatment, nitriding treatment, etching, sputtering, etc. Examples of films that can be formed on the surface of the object W by film formation include a titanium oxide film, a titanium nitride film, a boron nitride film, and a DLC (Diamond Like Carbon) film.

[0021] The type of gas introduced into the chamber 10 during surface treatment is appropriately selected depending on the type of surface treatment to be performed. Typical gases include, but are not limited to, argon, hydrogen, methane, acetylene, oxygen, nitrogen, and tetramethylsilane. When performing surface treatment, one type of gas may be introduced, or two or more types of gases may be introduced simultaneously. If necessary, the chamber 10 may be provided with multiple gas inlets 12.

[0022] [High density plasma] The surface treatment apparatus 101 shown in Fig. 1 can generate high-density plasma in the chamber 10 by using an electrode 54, which is a high-density plasma generating element. In this disclosure, "high-density plasma" refers to plasma with a higher density than the above-mentioned "direct current discharge plasma." In other words, high-density plasma cannot be formed simply by applying a voltage between the object W and the inner wall 11 to cause a glow discharge, but requires a high-density plasma generating element to generate the high-density plasma.

[0023] As shown in FIG. 1 , the electrode 54 is provided so as not to contact the object W and is closer to the object W than the inner wall 11. Typically, the electrode 54 is set to the same potential as the object W. When DC discharge plasma is generated in the chamber 10 in this configuration, the density of the plasma generated in the surface region Sh near the electrode 54 is higher than the density of the plasma generated in other surface regions of the object W. In other words, the electrode 54 can generate high-density plasma in the surface region Sh, which is a portion of the surface S to be treated of the object W. The higher the density of the plasma generated on the surface of the object W, the faster the plasma treatment speed.

[0024] The potential of the electrode 54 may be the same as or different from that of the object W. However, even when the potential of the electrode 54 and the potential of the object W are different, in order to generate high-density plasma, the potentials of both the electrode 54 and the object W must be sufficiently lower than ground potential. The potentials of the electrode 54 and the object W that generate high-density plasma can be designed as appropriate based on common knowledge in the technical field, including when the potentials of the electrode 54 and the object W are different.

[0025] The distance between the electrode 54 and the processing target surface S of the object W may be 1 mm or more and 10 mm or less, preferably 4 mm or more and 8 mm or less, and more preferably 4 mm or more and 6 mm or less. When the distance between the electrode 54 and the processing target surface S is within the above range, the density of the high-density plasma in the surface region Sh can be further increased.

[0026] The electrode 54 is preferably plate-shaped. It may be a flat or curved plate, but a flat plate is preferred from the viewpoints of availability and versatility. When the direction of the electrode 54 having the largest dimension is defined as the longitudinal direction, the longitudinal dimension of the electrode 54 is preferably 5 cm or more and 50 cm or less, and more preferably 10 cm or more and 30 cm or less. When the dimensions of the electrode 54 are within this range, efficient and uniform surface treatment can be easily performed. Furthermore, when microwaves are introduced, it is preferable to set the dimensions of the electrode 54 according to the wavelength of the microwaves, as described below.

[0027] The microwave introducing element 50 included in the surface treatment apparatus 101 of this embodiment is configured to introduce microwaves to the electrode 54 in the chamber 10 through the quartz window 53. When microwaves are introduced to the electrode 54, the microwaves are superimposed on the electrode 54 and propagate along the surface of the electrode 54 in a surface region Sh near the electrode 54. The microwaves propagating along the surface of the electrode 54 in this manner can generate surface wave plasma near the surface of the object W. The surface wave plasma can further increase the density of the high-density plasma compared to when the electrode 54 is simply disposed.

[0028] When microwaves are introduced, electrode 54 is a plate electrode having a maximum longitudinal dimension, and the longitudinal dimension is preferably 50% to 150% of the microwave wavelength, and more preferably 70% to 130%. For example, when microwaves with a frequency of 2.45 GHz (wavelength of 12 mm) are introduced, the longitudinal dimension of the plate electrode is preferably 6 mm to 18 mm, and more preferably 8.4 mm to 15.6 mm.

[0029] However, it is generally difficult to generate high-density plasma uniformly over a large area. For this reason, DC discharge plasma has been used for surface treatment of objects W having large treatment surfaces S. However, surface treatment using DC discharge plasma has the problem of slow treatment speed.

[0030] [Surface treatment method] A surface treatment method according to one embodiment of the present disclosure is a method of performing surface treatment using a surface treatment device 101 shown in Fig. 1. In the surface treatment method of this embodiment, high-density plasma is generated on a part (surface region Sh) of the surface S to be treated by an electrode 54 (high-density plasma generating element) provided at a position away from the surface S to be treated of an object W, and the entire surface S to be treated is plasma-treated by rotating or moving the object W relative to the electrode 54.

[0031] The above method uses high-density plasma, which allows for faster processing speeds than surface processing using direct-current discharge plasma. The high-density plasma is formed on a portion of the surface S to be processed, but by moving or rotating the object W relative to the electrode 54, which is a high-density plasma generating element, to scan the entire surface S to be processed, the entire surface S to be processed can be processed at high speed.

[0032] As shown in FIG. 1 , in the surface treatment method of the present disclosure, the high-density plasma generating element (electrode 54) is provided at a position away from the surface S to be treated. If the high-density plasma generating element were in contact with the surface S to be treated, an arc discharge would occur at the contact point when the object W is moved or rotated relative to the high-density plasma generating element, causing deterioration of the surface. In the surface treatment method of the present disclosure, the high-density plasma generating element is provided at a position away from the surface S to be treated, so that the surface S to be treated is not deteriorated when the object W is rotated or moved relative to the high-density plasma generating element. With this configuration, the entire large-area surface S to be treated of the object W can be plasma-treated at high speed.

[0033] Furthermore, according to this embodiment, when the cylindrical object W is moved or rotated in the direction of arrow A1 or A2, the distance between the target surface S of the object W and the electrode 54 is maintained constant. By maintaining a constant distance between the target surface S and the high-density plasma generating element, the density of the high-density plasma generated by the high-density plasma generating element can be maintained constant, resulting in more uniform surface treatment. Thus, in the surface treatment method of the present disclosure, it is preferable to rotate or move the object W relative to the high-density plasma generating element while maintaining a constant distance between the target surface S of the object W and the high-density plasma generating element.

[0034] Furthermore, according to this embodiment, the object W and the electrode 54 rotate relatively around the rotation axis (specifically, the central axis of the cylindrical object W), and the electrode 54 extends along the rotation axis. When the object W is rotated relatively to the high-density plasma generating element, the high-density plasma generating element extends along the rotation axis, thereby minimizing fluctuations in the distance between the object W and the high-density plasma generating element. Note that the relative movement between the object W and the high-density plasma generating element in this case is not limited to rotation, and the object W and the high-density plasma generating element may also move relatively along the rotation axis.

[0035] In this embodiment, the object W has a cylindrical shape. When the object W has a cylindrical or columnar shape, rotation or movement is required to treat the entire surface S to be treated with high-density plasma. The surface treatment method of the present disclosure is suitable because it can treat the entire surface at high speed even when the object W has a cylindrical or columnar shape.

[0036] In this embodiment, the object W faces the electrode 54 in the horizontal direction. Therefore, particles and the like are less likely to accumulate on the treatment target surface S of the object W, and high-quality surface treatment can be performed.

[0037] Although the above embodiment shows an example in which a DC voltage is applied to the object W, a high-frequency voltage may be applied to the object W. That is, in the surface treatment method of the present disclosure, a DC voltage or a high-frequency voltage may be applied to the object W. By applying a DC voltage or a high-frequency voltage to the object W, the treatment speed can be increased.

[0038] Furthermore, in this embodiment, an electrode 54 is used as a high-density plasma generating element, which is disposed opposite the surface S to be treated. The size, shape, and placement of the electrode 54 within the chamber 10 can be freely selected, so by using the electrode 54 as a high-density plasma generating element, high-density plasma can be generated at a desired position and in a desired area.

[0039] In addition to those described above, examples of high-density plasma include microwave plasma, electron cyclotron resonance plasma (ECR), helicon wave excited plasma (HWP), magnetron plasma, magnetic neutral discharge (NLD), inductively coupled plasma (ICP), narrow electrode parallel plate plasma, UHF plasma, surface wave excited plasma (SWP), etc. The high-density plasma generating element is not particularly limited as long as it is a member that generates high-density plasma on a part of the surface to be treated, and examples include an antenna, a magnet, a coil, etc. in addition to an electrode.

[0040] [Another embodiment] FIG. 2 is a schematic diagram of a surface treatment apparatus 201, which is an example of an apparatus for performing a surface treatment method according to another embodiment of the present disclosure. Components identical to those in the surface treatment apparatus 101 shown in FIG. 1 are designated by the same reference numerals, and redundant description will be omitted. As shown in FIG. 2, the surface treatment apparatus 201 includes a chamber 210, in which an object Wa and an object Wb, which are different from the object Wa, are disposed as surface treatment targets. The objects Wa and Wb are fixed to fixed rods 220a and 220b, respectively, and configured to be movable or rotatable by moving mechanisms 230a and 230b. The configurations of the fixed rods 220a and 220b and the moving mechanisms 230a and 230b are identical to the fixed rod 20 and the moving mechanism 30 of the surface treatment apparatus 101, respectively. The shapes of the objects Wa and Wb may be the same as the object W in FIG. 1, e.g., cylindrical. As shown in FIG. 2, the objects Wa and Wb are disposed adjacent to each other with a given distance between them.

[0041] In the surface treatment device 201, when a voltage is applied between the object Wa and the object Wb and the inner wall 211 using the bias power supply 40 to generate a DC discharge plasma, the object Wa and the object Wb, which are at the same potential, are in close proximity to each other, and therefore a high-density plasma is generated in the surface region Sh between the object Wa and the object Wb. The generation of the high-density plasma between the object Wa and the object Wb is based on the same principle as the generation of the high-density plasma between the object W and the electrode 54, which are in close proximity to each other, in the surface treatment device 101. This allows the treatment surfaces S of the object Wa and the object Wb to be simultaneously treated with the high-density plasma in the surface region Sh. In other words, the surface treatment device 201 is configured so that the object Wb functions as a high-density plasma generating element for the object Wa, and the object Wa functions as a high-density plasma generating element for the object Wb. As in this embodiment, the surface treatment method disclosed herein also includes a method in which the high-density plasma generating element is a second object different from the object, and the high-density plasma generated between the object and the second object is used to simultaneously perform surface treatment of the object and the second object.

[0042] The number of objects to be surface-treated simultaneously is not limited to two, and may be three or more. When there are three or more objects, the arrangement of the objects is not particularly limited as long as high-density plasma is generated between one object and at least one other object adjacent to the object. An arrangement in which one object is adjacent to two or more objects and high-density plasma is generated between each object is preferable because it further improves the treatment speed. More specifically, the distance between the surfaces to be treated of adjacent objects may be 1 mm or more and 10 mm or less, preferably 4 mm or more and 8 mm or less, and more preferably 4 mm or more and 6 mm or less.

[0043] The surface treatment method of the present disclosure has been described above while showing specific embodiments, but the present disclosure is not limited to these, and configurations obtained by adding, deleting, or substituting components in each embodiment, and by combining part or all of multiple embodiments are also included in the present disclosure.

[0044] Although the electrode 54 is a component of the microwave introduction element 50, microwaves are not essential for generating high-density plasma, but can be introduced optionally to further increase the density of the high-density plasma. [Example]

[0045] (Example 1: Surface treatment using high-density plasma) A plate-shaped electrode was placed in the chamber as a high-density plasma generating element, and a DLC film was formed on the surface of a test workpiece using DC discharge plasma under the following film formation conditions: The inner wall of the chamber was used as the ground, and a negative bias voltage was applied to the workpiece and the electrode. The workpiece and the electrode were at the same potential. The distance between the workpiece and the electrode was 4 mm. The state of plasma generation during film formation was observed visually, and the film formation rate in the high-density plasma region formed near the electrode and the film formation rate in the region outside the high-density plasma region (hereinafter referred to as the "DC discharge plasma region") were calculated from the film thickness of the workpiece after film formation. <Film formation conditions> Bias voltage: -500V Gas flow rate: argon 40sccm, methane 200sccm, tetramethylsilane (TMS) 20sccm Chamber pressure: 75Pa Film formation time: 30 minutes The unit "sccm" is the unit of flow rate "mL / min" under standard conditions (temperature 0°C, pressure 101.3 kPa).

[0046] Visual observation during film formation confirmed that the plasma emitted stronger light in the region between the electrode and the workpiece. Furthermore, the film formation rate based on film thickness was 3.6 μm / h in the high-density plasma region and 1.2 μm / h in the DC discharge plasma region. The results of Example 1 indicate that high-density plasma can be generated on a portion of the surface to be treated by placing the electrode, thereby improving the surface treatment rate.

[0047] (Examples 2 to 6: Electrode length) In the apparatus used in Example 1, a microwave generator (Micro Electronics, model number: MMG-213V-2P) was further used to introduce microwaves with a frequency of 2.45 GHz (wavelength in vacuum: approximately 120 mm) into the plate electrode, generating high-density plasma to form a DLC film on the outer surface of a cylindrical workpiece. The film formation conditions were as follows: The workpiece had a longitudinal length of 200 mm and an outer diameter of 49 mm. The dimensions of the plate electrode in Examples 2 to 6 were 25 mm, 50 mm, 100 mm, 150 mm, and 200 mm along the longitudinal direction of the workpiece, respectively, and a width of 10 mm for each. The distance between the workpiece and the electrode was 4 mm. During film formation, the workpiece was rotated around the longitudinal direction as the rotation axis, thereby forming a film over the entire side surface of the workpiece. In each example, the film thickness was measured at 10 mm intervals on the surface within a range of ±100 mm along the longitudinal direction of the workpiece, with the microwave introduction position as the origin, and the film deposition rate (mm 3 / h) was calculated. The results are shown in Table 1. <Film formation conditions> Bias voltage: -500V Gas flow rate: argon 40sccm, methane 200sccm, TMS 20sccm Microwave power: 1000W Microwave duty ratio: 20% Microwave average power: 200W Chamber pressure: 75Pa Film formation time: 240 seconds

[0048] [Table 1]

[0049] The results of Examples 2 to 6 suggest that the film formation rate improves when the length (maximum dimension) of the electrode in the longitudinal direction is approximately the same as the wavelength of the microwave.

[0050] (Examples 7 to 12: Distance between workpiece and electrode) As in Examples 2 to 6, a DLC film was formed on the workpiece while a microwave with a frequency of 2.45 GHz was superimposed on the electrode. The length of the electrode in the longitudinal direction was 100 mm. In Examples 7 to 12, the distance between the workpiece and the electrode was set to 1 mm, 4 mm, 6 mm, 8 mm, 10 mm, and 20 mm, respectively. In each example, the film formation rate (mm 3 / h) are shown in Table 2.

[0051] [Table 2]

[0052] The above results show that the distance between the workpiece and the electrode affects the film formation rate, and that there is a preferred range. [Explanation of symbols]

[0053] 101,201 Surface treatment equipment 10,210 chambers 11,211 Interior walls 12 Gas inlet 13 Gas outlet 20,220a,220b Fixed rod 30,230a,230b Movement mechanism 40 Bias power supply 50 Microwave introduction element 51 Microwave Oscillator 52 Waveguide 53 Quartz window 54 electrode

Claims

1. generating high-density plasma on a portion of the surface to be treated by a high-density plasma generating element provided at a position away from the surface to be treated of the object; A surface treatment method in which the plasma treatment is performed on the entire surface of the treatment object by rotating or moving the object relative to the high-density plasma generating element.

2. 2. The surface treatment method according to claim 1, wherein the object is rotated or moved relative to the high-density plasma generating element while maintaining a constant distance between the surface to be treated and the high-density plasma generating element.

3. the object and the high-density plasma generating element rotate relatively about a rotation axis, and optionally move relatively along the rotation axis; The surface treatment method of claim 1 , wherein the high-density plasma generating element extends along the axis of rotation.

4. The surface treatment method according to claim 1 , wherein the object has a cylindrical or columnar shape.

5. The surface treatment method according to claim 1 , wherein a DC voltage or a high-frequency voltage is applied to the object.

6. 5. The surface treatment method according to claim 1, wherein the high-density plasma generating element is an electrode disposed opposite to the surface to be treated.

7. 7. The surface treatment method according to claim 6, wherein the distance between the electrode and the surface to be treated is 4 mm or more and 8 mm or less.

8. The surface treatment method according to claim 6 , wherein microwaves are superimposed on the electrode.

9. the electrode is a plate electrode having a maximum dimension in a longitudinal direction, The surface treatment method according to claim 8 , wherein the longitudinal dimension is 50% or more and 150% or less of the wavelength of the microwave.

10. 5. The surface treatment method according to claim 1, wherein a DC voltage is applied to the object and the high-density plasma generating element, and a microwave is introduced into the high-density plasma generating element to generate the high-density plasma.

11. the high-density plasma generating element is a second object different from the object; 3. The surface treatment method according to claim 1, wherein the surface treatment of the object and the surface treatment of the second object are performed simultaneously using high-density plasma generated between the object and the second object.

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