Plasma processing apparatus and plasma processing method

Abstract

To provide a plasma processing apparatus which can form a thicker surface modification layer than a conventional one while being low in cost.SOLUTION: A plasma processing apparatus 100 for processing a workpiece 10 includes: a first electrode 1 and a second electrode 2 to which a power feeding part is connected; a first dielectric 3 in a tubular shape covering the first electrode; a first light-emitting gas 4 sealed in the first dielectric; a mounting part on which the workpiece is mounted at a position separated from the first dielectric; and a plasma source gas existing in a gap between the first dielectric and the workpiece. The first electrode, the first light-emitting gas, the first dielectric, the plasma source gas, and the second electrode are arranged in this order from the first electrode toward the second electrode.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a plasma processing apparatus and a plasma processing method. [Background technology]

[0002] One type of optical cleaning device is the atmospheric pressure plasma processing device, which applies a high voltage between electrodes under atmospheric pressure to generate plasma, which is used to remove organic matter adhering to the surface of a workpiece (object to be processed) or to make the surface hydrophilic (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-320845 A Summary of the Invention [Problem to be solved by the invention]

[0004] In atmospheric pressure plasma treatment, active species of atmospheric components generated by the plasma act on the surface of the workpiece to modify the surface of the workpiece. However, there is a need to modify not only the very surface of the workpiece, but also from the surface to the inside of the workpiece, that is, to thicken the surface modification layer.

[0005] Specific examples are shown below. In a process for plating a circuit board made mainly of a resin material, the surface modification layer of the circuit board may be treated before the plating is formed in order to increase the strength of the plating. In such a surface modification process, there is a need to thicken the surface modification layer of the workpiece in order to improve the adhesion between the circuit board and the plating material. In addition, there is a demand for the surface modification process to be low cost.

[0006] Therefore, an object of the present invention is to provide a plasma processing apparatus and a plasma processing method that are capable of forming a thicker surface modification layer than before while being low cost. [Means for solving the problem]

[0007] The plasma processing apparatus for processing a workpiece of the present invention comprises: a first electrode and a second electrode to which a power supply unit is connected; A first dielectric body having a tube shape covering the first electrode; A first luminous gas sealed inside the first dielectric material; a placement portion on which the workpiece is placed at a position spaced apart from the first dielectric; a plasma source gas present in a gap between the first dielectric and the workpiece; The first electrode, the first light emitting gas, the first dielectric, the plasma source gas, and the second electrode are arranged in this order from the first electrode toward the second electrode.

[0008] Although details will be described later, when the plasma processing apparatus of the present invention is used, the surface of the workpiece is modified by two reactions. In the first reaction, when a voltage is applied between the first electrode and the second electrode, the plasma source gas present in the gap between the first dielectric and the workpiece is converted into plasma, and the plasma-converted active species directly act on the surface of the workpiece, modifying the surface of the workpiece. The process utilizing this first reaction is based on the same mechanism as conventional atmospheric pressure plasma processing.

[0009] The second reaction is a process in which, when a voltage is applied between the first electrode and the second electrode, ultraviolet light is emitted from the first luminous gas sealed inside the first dielectric, and the ultraviolet light acts on the workpiece to modify the surface and the vicinity of the surface of the workpiece. Since the ultraviolet light penetrates into the inside of the workpiece, the surface can be modified even further into the workpiece than in the process using the first reaction. Therefore, when the surface of the workpiece is modified by two reactions as in the present invention, a thicker surface modification layer can be formed compared to the case of only atmospheric pressure plasma treatment.

[0010] Conventionally, etching methods that utilize chemical reactions of chemicals have been known as surface modification treatments that can form thick surface modification layers. However, the present invention does not use chemicals, so the device configuration is simple, low cost, and has little impact on the natural environment.

[0011] As will be described in detail in each embodiment, in the above-mentioned plasma processing apparatus, the "mounting section on which the workpiece is placed" may be provided on the second electrode, or on a workpiece transport section, etc.

[0012] The first electrode may extend in one direction as a whole. The term "extending in one direction as a whole" means that the electrode extends in only one direction when viewed as a whole, but may extend in a direction other than the one direction when a part of the electrode is enlarged and viewed.

[0013] The first electrode may be in a coil shape. The "coil shape" is an example of an electrode that "extends in a direction other than one direction" when viewed in part, but as described below, there are coil shapes that extend in one direction as a whole. The use of a coil-shaped electrode allows for uniform discharge.

[0014] The plasma source gas may be present in the gap between the second electrode and the workpiece. This allows surface modification by atmospheric pressure plasma on both sides of the workpiece. In this case, the placement unit is provided on the workpiece transport unit or the like, rather than on the second electrode.

[0015] a tube-shaped second dielectric body covering the second electrode; A second luminous gas is sealed inside the second dielectric material, The first electrode, the first light-emitting gas, the first dielectric, the plasma source gas, the second dielectric, the second light-emitting gas, and the second electrode may be arranged in this order from the first electrode toward the second electrode, thereby enabling surface modification by atmospheric pressure plasma and ultraviolet light on both sides of the workpiece, respectively.

[0016] a conveying unit that conveys the workpiece located between the first dielectric and the second electrode; and a control unit that controls the transport unit to adjust the transport speed of the workpiece based on at least one of the intensity of the ultraviolet light emitted from the first light-emitting gas and the input energy for generating plasma from the plasma source gas. This makes it possible to achieve a desired and uniform degree of surface modification.

[0017] A drive unit for moving at least one of the first electrode, the second electrode, and the placement unit in a direction perpendicular to a surface of the workpiece; a control unit that controls the drive unit so as to adjust a gap between the first electrode and the workpiece based on at least one of an intensity of the ultraviolet light emitted from the first light-emitting gas and an input energy for generating plasma from the plasma source gas; and This allows the degree of surface modification of the workpiece 10 to be desired and uniform. To move the first electrode or the second electrode in a direction perpendicular to the surface of the workpiece, the first electrode or the second electrode itself may be connected to a drive unit, or a support (e.g., a lamp house) that supports the first electrode or the second electrode may be connected to the drive unit.

[0018] A gas supply unit for supplying the plasma source gas may be provided.

[0019] At least one of the first electrode and the second electrode may be arranged in a plurality of rows along the surface of the workpiece. This allows the power supply start timing and the input voltage to be changed between the plurality of arranged electrodes. Alternatively, the use of some of the electrodes can be stopped.

[0020] A conveying unit that conveys the workpiece, which is a long sheet, The conveying section may support the long sheet by sandwiching both sides of the long sheet, thereby enabling the long sheet to be accurately positioned so as not to rise or sink.

[0021] The plasma processing method of the present invention includes a first electrode and a second electrode to which a power supply unit is connected, a tubular first dielectric covering the first electrode, a first light-emitting gas sealed inside the first dielectric, and a plasma source gas present in a gap between the first dielectric and a workpiece, the method comprising: carrying the workpiece into a plasma processing apparatus in which the first electrode, the first light-emitting gas, the first dielectric, the plasma source gas, the workpiece, and the second electrode are arranged in this order from the first electrode toward the second electrode; treating the carried-in workpiece with plasma generated from the plasma source gas and ultraviolet light emitted from the first light-emitting gas; Equipped with.

[0022] The workpiece may be a circuit board having through holes, vias, and the like. Effect of the Invention

[0023] It is possible to provide a plasma processing apparatus and a plasma processing method that are capable of forming a thicker surface modification layer than before while being low cost. [Brief description of the drawings]

[0024] [Figure 1] 1 is a diagram showing a main part of a plasma processing apparatus according to a first embodiment; [Diagram 2] 1 is a diagram illustrating a plasma processing apparatus according to a first embodiment. [Diagram 3] 1 is a control block diagram of a plasma processing apparatus according to a first embodiment. [Figure 4A] 1 is a cross-sectional view of a main part of a plasma processing apparatus according to a first embodiment taken along an XZ plane. [Figure 4B] FIG. 13 is a diagram showing a modified example of the first electrode. [Diagram 5] FIG. 13 is a diagram showing a main part of a plasma processing apparatus according to a second embodiment. [Figure 6A] FIG. 13 is a diagram showing a main part of a plasma processing apparatus according to a third embodiment. [Figure 6B]FIG. 13 is a diagram showing a main part of a plasma processing apparatus which is a modified example of the third embodiment. [Figure 7] FIG. 13 is a diagram showing a plasma processing apparatus according to a fourth embodiment together with an embodiment of a workpiece transport device. [Figure 8] FIG. 1 is a diagram for explaining a tensile test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] An embodiment of a plasma processing apparatus will be described with reference to the drawings. Note that the following drawings are schematic illustrations, and the dimensional ratios in the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily match.

[0026] In the following, each drawing will be described with reference to the XYZ coordinate system. In this specification, when a direction is expressed and a positive or negative direction is to be distinguished, it is described with a positive or negative sign, such as "+X direction" and "-X direction". When a direction is expressed without distinguishing between positive and negative directions, it is simply described as "X direction". That is, in this specification, when it is simply described as "X direction", both "+X direction" and "-X direction" are included. The same applies to the Y direction and the Z direction. In the embodiment described below, the -Z direction represents the direction of gravity.

[0027] First Embodiment [Principle of plasma processing equipment] FIG. 1 is a diagram showing a main part of a plasma processing apparatus 100 according to an embodiment of the present invention. The principle of the plasma processing apparatus 100 will be described with reference to this diagram. The plasma processing apparatus 100 includes a first electrode 1, a second electrode 2, and a first dielectric 3 covering the first electrode 1. There is a gap between the first electrode 1 and the first dielectric 3, and a first light-emitting gas 4 is sealed in this gap. There is a plasma source gas between the first dielectric 3 and the second electrode 2. Therefore, from the first electrode 1 toward the second electrode 2, the first electrode 1, the first light-emitting gas 4, the first dielectric 3, the plasma source gas, and the second electrode 2 are arranged in this order.

[0028] Although the workpiece 10 is not a component of the plasma processing apparatus 100, it is shown in FIG. 1 for convenience of explanation. Similarly, the workpiece 10 may also be shown in the plasma processing apparatuses in FIG. 2 and subsequent figures. The workpiece 10 is placed on a placement part with a gap G1 between the first dielectric 3 and the second electrode 2. In FIG. 1, the second electrode 2 functions as the placement part. The second electrode 2 supports the workpiece 10, thereby placing the workpiece 10 at a specified position.

[0029] The first electrode 1 and the second electrode 2 are connected to a power supply unit 5. The power supply unit 5 applies a high AC voltage between the first electrode 1 and the second electrode 2. As a result, the following two reactions occur in the plasma processing apparatus, and the workpiece 10 is processed by these two reactions.

[0030] The first is a reaction on the surface of the workpiece 10 by atmospheric pressure plasma. Hereinafter, this reaction may be referred to as the "first reaction." When a high voltage is applied between the first electrode 1 and the second electrode 2, the plasma source gas present in the gap G1 between the first dielectric 3 and the workpiece 10 is turned into plasma, generating atmospheric pressure plasma P1. In FIG. 1, the area where the atmospheric pressure plasma P1 is generated is shown by hatching with a dashed line. When air is present in the gap G1, nitrogen molecules or oxygen molecules contained in the air are turned into plasma. The plasma-converted active species breaks the chemical bonds of the organic molecules on the surface of the workpiece 10, causing a chemical reaction. This makes it possible to modify the surface of the workpiece 10 by removing organic contaminants or forming hydrophilic functional groups (hydroxyl groups, carbonyl groups, carboxy groups, etc.) on the surface of the workpiece 10. If there are few organic contaminants on the surface of the workpiece 10 and the surface is hydrophilic, when plating is formed on the workpiece 10, the adhesion of the plating to the workpiece 10 is high and the plating is less likely to peel off.

[0031] The second is a reaction on or near the surface of the workpiece 10 using ultraviolet light. Hereinafter, this reaction may be referred to as the "second reaction." When a high voltage is applied between the first electrode 1 and the second electrode 2, a dielectric barrier discharge occurs, exciting the atoms of the first luminous gas 4 and instantaneously transforming into an excimer state. When returning from this excimer state to the original state (ground state), ultraviolet light (excimer light) L1 having a spectrum specific to that excimer is emitted. In FIG. 1, the ultraviolet light L1 is illustrated by arrows made of thick lines, one of which is labeled "L1."

[0032] The second reaction includes a reaction that occurs when the workpiece 10 directly absorbs the ultraviolet light L1 (hereinafter referred to as the "direct reaction"), and a reaction in which the ultraviolet light L1 activates the oxygen present in the ultraviolet light irradiation atmosphere to generate atomic oxygen, and the generated atomic oxygen acts on the workpiece 10 (hereinafter referred to as the "reaction mediated by atomic oxygen").

[0033] The direct reaction occurs when the energy of the ultraviolet light itself breaks the chemical bonds of the organic molecules contained in the workpiece 10. For example, the Norrish reaction is known as a direct reaction. The Norrish reaction is a photodecomposition reaction in which a ketone or aldehyde is used as a substrate, and two radicals are generated on a carbonyl group due to photoexcitation. The photodecomposition reaction can remove organic contaminants from the workpiece 10 or generate hydrophilic functional groups.

[0034] Reactions mediated by atomic oxygen are caused by the absorption of UV light by atmospheric oxygen molecules and the ozone produced by their subsequent reactions. For example, UV light with a central wavelength of 172 nm generated by a xenon excimer lamp (i.e., a dielectric barrier discharge excimer lamp filled with xenon gas) is strongly absorbed by atmospheric oxygen molecules O2, directly converting them into excited oxygen atoms O( 1 D) (see formula (1) below) or via ozone O3, excited oxygen atoms O( 1 D) is produced (see equations (2) and (3) below). O2+hν(172nm) → O( 1 D)+O(3 P) …(1) O( 3 P) + O2 → O3…(2) O3+hν(172nm) → O( 1 D) + O2…(3)

[0035] As another example, UV light with central wavelengths of 185 nm and 254 nm emitted by a low-pressure mercury lamp is absorbed by oxygen molecules O2 in the atmosphere to generate ozone O3 (see formulas (4) and (5) below). Furthermore, ozone O3 absorbs UV light of 254 nm to generate excited oxygen atoms O(1D) (see formula (6) below). O2+hν(185nm) → O( 3 P)+O( 3 P) …(4) O( 3 P) + O2 → O3…(5) O3+hν(254nm) → O( 1 D) + O2…(6)

[0036] In the above formula, hν represents the energy of ultraviolet light. O( 3 P) and O( 1 D) represents atomic oxygen. In other words, ultraviolet light converts oxygen contained in the irradiated environment into atomic oxygen (O( 3 P) or O( 1 D)) Atomic oxygen is active and can break chemical bonds of organic molecules in the workpiece 10. This can remove organic contaminants from the workpiece 10 or provide or generate hydrophilic functional groups.

[0037] The ultraviolet light L1 penetrates into the workpiece 10, although only near the surface. In addition, oxygen molecules are also present inside the workpiece 10. Therefore, these reactions using the ultraviolet light L1 (direct reactions and reactions mediated by atomic oxygen) occur not only on the surface of the workpiece 10, but also inside the workpiece 10 to a depth that the ultraviolet light L1 can penetrate. As a result, it is presumed that the second reaction using the ultraviolet light L1 can modify the inside of the workpiece 10, compared to the treatment using the first reaction.

[0038] As described above, the surface modification treatment by the first reaction and the second reaction makes it possible to form a thick surface modified layer that is difficult to form by the conventional simple atmospheric pressure plasma treatment alone.

[0039] The wavelength of the ultraviolet light L1 varies depending on the type of luminescent gas filled in the first dielectric 3. For example, when the filled gas is Kr, Ar, or Xe, ultraviolet light having a relatively strong spectrum at wavelengths of 146 nm, 126 nm, or 172 nm is emitted, respectively. When the discharge gas is a mixed gas of Kr and Cl, or a mixed gas of Xe and Cl, ultraviolet light having a relatively strong spectrum at wavelengths of 222 nm or 308 nm is emitted, respectively.

[0040] [Comparison of surface modification using atmospheric pressure plasma and ultraviolet light] Using infrared spectroscopy (ATR-FTIR), we compare and analyze surface modification using atmospheric pressure plasma and ultraviolet light, and explain the results. Like ultraviolet light, infrared light penetrates into the inside of the sample, albeit to a small extent. Therefore, by using ATR-FTIR, it is possible to obtain an infrared absorption spectrum that reflects not only the composition of the sample surface, but also the composition from the sample surface to a depth of several hundred nm to several μm, which is the depth that infrared light can penetrate.

[0041] Table 1 shows the ATR-FTIR results for three samples. Sample S1 is a sample of COP (cycloolefin polymer) that has been subjected to only atmospheric pressure plasma treatment. This sample was obtained by atmospheric pressure plasma treatment using the remote method. In the remote method, only active species generated by plasma are sprayed onto the sample for surface treatment, and no UV light is irradiated. Sample S2 is a sample of COP that has been subjected to only UV light irradiation treatment (wavelength 172 nm). Sample S3 is a comparative sample of COP that has not been subjected to any surface modification treatment.

[0042] The "Absorbance (relative value)" in Table 1 indicates the absorption of the stretching vibration of C=O at a wave number of 1700 cm -1 ~1750cm -1The absorbance of each sample in is expressed as a relative value when the average absorbance of sample S3 (untreated sample) is set to 1. The larger the "absorbance (relative value)," the greater the amount of C=O bonds in the hydrophilic group. Also, as mentioned above, due to the characteristics of ATR-FTIR, this value reflects the composition from the surface of the sample to a depth of several hundred nm to several μm, where infrared light can penetrate.

[0043] [Table 1]

[0044] As can be seen from Table 1, the absorbance of sample S1 is greater than 1, which is the reference value for sample S3. This indicates that atmospheric pressure plasma treatment has increased the number of C=O bonds, which are hydrophilic groups, on the surface of the sample. Furthermore, the absorbance of sample S2 is greater than that of sample S1, indicating that it has a high surface modification capability. This is thought to be because, unlike atmospheric pressure plasma treatment, ultraviolet light irradiation treatment also modifies the sample inside the sample, near the surface.

[0045] [Plasma processing equipment] The plasma processing apparatus 100 will be described in its entirety with reference to Figures 2 and 3. Figure 2 shows a cross-sectional view of the plasma processing apparatus 100 in the YZ plane. Figure 3 shows a control block diagram of the plasma processing apparatus 100.

[0046] [First electrode and second electrode] The plasma processing apparatus 100 includes a first electrode 1 and a second electrode 2. As shown in FIG. 2, in the plasma processing apparatus 100 of this embodiment, a workpiece 10 is placed on the flat second electrode 2 along the XY plane. In the plasma processing apparatus 100, three first electrodes (1a, 1b, 1c) are arranged in the Y direction. Each of the three first electrodes (1a, 1b, 1c) is covered with a first dielectric 3. As described above, a first light-emitting gas 4 is sealed in the gap between each first dielectric 3 and each first electrode (1a, 1b, 1c).

[0047] A combination of the electrodes and the tubular dielectric covering the electrodes is sometimes called a "lamp." The plasma processing apparatus 100 has a lamp house 20 that encloses three lamps. The lamp house 20 is a support that supports the lamps. The inner wall of the lamp house 20 may have a reflective member for directing the ultraviolet light toward the workpiece 10.

[0048] The lamp house 20 can be moved in the Z direction perpendicular to the surface of the workpiece 10 by the lamp house drive unit 21. The control unit 40 controls the lamp house drive unit 21. This adjusts the gap G1 between the workpiece 10 and the first dielectric 3. The size of the gap G1 affects the degree of surface modification by the atmospheric pressure plasma. Specific examples of the lamp house drive unit 21 include an electric, pneumatic, or hydraulic actuator. Note that to adjust the gap G1, instead of (or in addition to) moving the lamp house in the Z direction, the second electrode 2 may be moved in the Z direction so that the workpiece 10 moves in the Z direction.

[0049] In the plasma processing apparatus 100, two second electrodes (2a, 2b) are arranged in the Y direction. A high AC voltage is supplied between the three first electrodes (1a, 1b, 1c) and the two second electrodes (2a, 2b) from a power supply unit 5. The power supply unit 5 is controlled by a control unit 40 (see FIG. 3). The power supply unit 5 includes a power supply that supplies the high AC voltage. As a modified example, the power supply unit 5 may receive the high AC voltage from a power supply external to the plasma processing apparatus 100.

[0050] FIG. 4A is a cross-sectional view of the main part of the plasma processing apparatus 100 along the XZ plane. As shown in FIG. 4A, the first electrode 1 extends in the X direction as a whole. The first dielectric 3 also extends in the X direction as a whole. The second electrode 2 and the workpiece 10 extend along the XY plane. Therefore, the region on the workpiece 10 that is in contact with the atmospheric plasma P1 and the region on the workpiece 10 that is irradiated with the ultraviolet light L1 are both longitudinal in the X direction. In order to process the entire surface of the workpiece 10, the workpiece 10 is processed while being moved relative to the first electrode 1, the second electrode 2, and the first dielectric 3 in the Y direction. Usually, the workpiece 10 is moved relative to the first electrode 1, the second electrode 2, and the first dielectric 3, but the first electrode 1, the second electrode 2, and the first dielectric 3 may be moved relative to the workpiece 10, or both the workpiece 10 and the first electrode 1, the second electrode 2, and the first dielectric 3 may be moved. In consideration of production efficiency, the speed of the relative movement is desirably as high as possible within a range that allows surface modification, for example, 5 to 15 mm / sec, and preferably 8 to 12 mm / sec.

[0051] The timing of starting power supply to each electrode (1a, 1b, 1c, 2a, 2b) arranged in the Y direction may be different from each other. Power supply may be started when the workpiece 10 approaches each electrode (1a, 1b, 1c, 2a, 2b). The input voltage may be changed depending on the electrode, and depending on the processing conditions, some electrodes may be stopped from being used without applying a voltage to them. In this embodiment, the number of first electrodes 1 does not match the number of second electrodes 2, but the number of first electrodes 1 may match the number of second electrodes 2.

[0052] In Fig. 4A, the first electrode 1 is made of a conductor that extends linearly parallel to the X-axis, but the first electrode 1 is not limited to this type of conductor. In a modified example of the first electrode 1 shown in Fig. 4B, the conductor is wound in a coil shape (spiral shape), and the electrode extends in the X-direction as a whole. In the case of a coil-shaped electrode as shown in Fig. 4B, the gap G1 between the local position of the coil-shaped electrode and the workpiece 10 is not fixed but distributed, allowing uniform discharge.

[0053] The gap G1 between the workpiece 10 and the first dielectric 3 may be set depending on the material or thickness of the workpiece 10, or the desired degree of surface modification. The gap G1 may be, for example, 3 mm or less, and is particularly preferably 1 mm or less. The voltage applied to the electrodes may be set according to the gap G1, for example, 1 to 12 kV. If the degree of surface modification of the workpiece 10 is constant, the smaller the gap G1, the lower the voltage applied to the electrodes can be set.

[0054] The first electrode 1 and the second electrode 2 are made of a conductive material. As the electrode material, tungsten or a steel material such as stainless steel may be used.

[0055] The gap G1 may be adjusted based on the input energy (for example, the voltage applied to the electrodes) for generating the plasma. The relationship between the gap G1 and a suitable applied voltage may be obtained in advance by measurement, and may be appropriately selected, for example, by using a look-up table. The input energy may be measured by a measuring instrument (for example, a voltmeter), or the energy density of the plasma may be measured by a plasma detector 42 (see FIG. 3), and the gap G1 may be adjusted based on these measurement results. The intensity of the ultraviolet light emitted from the first light-emitting gas 4 may be measured by a photodetector 41 (see FIG. 3), and the gap G1 may be adjusted based on the measurement results. The control unit 40 may adjust the gap G1 based on the measurement results. The plasma detector 42 may be a detector that measures electromagnetic waves emitted together with the plasma, a detector that irradiates millimeter waves, neutral particles, or ions and measures the reaction thereto, a detector that inserts a probe into the plasma and measures the current, or the like, as appropriate, depending on the usage environment.

[0056] [First Dielectric] The first dielectric 3 is made of a dielectric material that transmits ultraviolet light, such as quartz glass. The first dielectric 3 has a tubular shape. The first electrode 1 is disposed inside the tubular shape so as not to contact the inner wall of the tube. The shape of the tube is not limited to a cylinder as shown in each drawing, and may be a square tube. The outer diameter of the first dielectric 3 may be, for example, 4 to 10 mm, preferably 5 to 7 mm. The inner diameter of the first dielectric 3 may be 2 to 9 mm, preferably 3 to 5 mm. The thickness of the first dielectric 3 may be 0.5 mm to 3.5 mm, preferably 1 to 3 mm.

[0057] [Work] The workpiece 10 is preferably a dielectric. When the workpiece 10 is a dielectric, a dielectric barrier discharge occurs over the entire surface of the workpiece 10, so that the workpiece 10 is more likely to be treated evenly. The workpiece 10 is made of a resin material such as PTFE (polytetrafluoroethylene) or COP (cycloolefin polymer). The size and thickness of the workpiece 10 are not particularly limited, but the workpiece 10 in this embodiment is a plate-like body having a thickness of 500 mm in the X direction, 300 mm in the Y direction, and 1.6 mm in the Z direction. As will be described later, the workpiece 10 may be a long sheet that is thinner and longer in one direction. However, the workpiece 10 does not have to be a dielectric.

[0058] [Transport section] As shown in Figures 2 and 3, the plasma processing apparatus 100 of this embodiment has a transport unit 25. The transport unit 25 transports the workpiece 10 in the +Y direction. The transport unit 25 of this embodiment is composed of multiple transport rollers. The multiple transport rollers have a power source (not shown) such as a motor, and rotate the transport rollers. The power source of the transport rollers is controlled by the control unit 40 (see Figure 3). The transport rollers are an example of the transport unit 25, and a transport arm, a gas bearing, an ultrasonic bearing, or the like may also be used as the transport unit 25.

[0059] The conveying speed of the workpiece 10 may be adjusted by controlling the conveying unit 25 based on the input energy for generating the plasma (e.g., the voltage applied to the electrodes). Alternatively, the input energy may be measured by a measuring instrument (e.g., a voltmeter) or the energy density of the plasma may be measured by a plasma detector 42, and the conveying speed of the workpiece 10 may be adjusted by controlling the conveying unit 25 based on these measurement results. The intensity of the ultraviolet light emitted from the first light-emitting gas 4 may be measured by a photodetector 43, and the conveying speed of the workpiece 19 may be adjusted by controlling the conveying unit 25 based on the measurement results. This allows the degree of surface modification of the workpiece 10 to be uniform.

[0060] [Gas supply section] As shown in FIG. 2 and FIG. 3, the plasma processing apparatus 100 of this embodiment has a gas supply unit 30. The gas supply unit 30 supplies a plasma source gas for generating active species of atmospheric pressure plasma to the gap G1 between the first dielectric 3 and the workpiece 10. The gas supply unit 30 is connected to a gas nozzle 31, and supplies an atmospheric gas around the plasma between the first electrode 1 and the workpiece 10 from the gas nozzle 31. As the plasma source gas, air or an inert gas such as nitrogen or argon can be used. Gases such as oxygen, acrylic acid, hydrogen, ammonia, water, or ethyl alcohol may be added to the air or inert gas. Alternatively, various acidic, alkaline, and neutral liquids may be included in the air or inert gas in a mist form.

[0061] A desired gas can be supplied in a specified amount by supplying gas from the gas supply unit 30. When air is used as the plasma source gas, the air within the plasma processing apparatus 100 can be used, and therefore the gas supply unit 30 is not an essential component of the plasma processing apparatus 100. However, the gas supply unit 30 may be used to supply a specified amount of air in which the moisture content in the air is controlled.

[0062] Second Embodiment 5 is a diagram showing the main parts of a plasma processing apparatus 200 according to a second embodiment. The following will mainly describe the differences between the second embodiment and the first embodiment. Items not described below are the same as those in the first embodiment. The third and subsequent embodiments will be described in the same manner as the second embodiment.

[0063] The second electrode 2 of the plasma processing apparatus 200 is spaced apart from the -Z side surface 10b of the workpiece 10 in the -Z direction. The second electrode 2 is covered with a second dielectric 6, and a second light-emitting gas 7 is sealed in the gap between the second electrode 2 and the second dielectric 6. A gap G2 is formed between the second dielectric 6 and the -Z side surface 10b of the workpiece 10. A plasma source gas is present in the gap G2, and when a high voltage is applied between the first electrode 1 and the second electrode 2, atmospheric pressure plasma P2 is generated from the plasma source gas. Furthermore, ultraviolet light L2 is emitted from the second light-emitting gas 7 sealed inside the second dielectric 6. As a result, surface modification is performed on the -Z side surface 10b of the workpiece 10 by the atmospheric pressure plasma P2 and the ultraviolet light L2.

[0064] In the second embodiment, since the workpiece 10 is separated from the second electrode 2, the placement portion for the workpiece 10 is not the second electrode 2. In this embodiment, the placement portion is a transport portion 25 (a plurality of transport rollers). In this embodiment, the transport portion 25 has a function of supporting the workpiece 10 during processing and a function of transporting the workpiece 10.

[0065] Each conveying roller can be moved in the Z direction perpendicular to the surface of the workpiece 10 by a Z direction drive unit 26. This adjusts the size of the gap G1 and the gap G2. The gap G2 may be the same value as the gap G1, or may be a different value. An electric, pneumatic or hydraulic actuator can be used as the Z direction drive unit 26.

[0066] The lamp composed of the second electrode 2 and the second dielectric 6 may also be supported by a lamp house and may have a lamp house drive unit for moving the lamp in the Z direction perpendicular to the surface of the workpiece 10. By bringing the first electrode 1 and the second electrode 2 closer together (by controlling the sum of the gap G1 and the gap G2 to be smaller), the degree of surface modification can be increased, or the applied voltage can be reduced.

[0067] The second luminous gas 7 may be the same as the first luminous gas 4, or a different gas may be used. Also, gas supply units 30 may be arranged on both the +Z side and the -Z side of the work 10 to supply different gases, or the supply amounts of the gases may be different. Of course, the gas supply unit 30 may be arranged on only one of the +Z side and the -Z side of the work 10.

[0068] <Third embodiment> FIG. 6A shows a main part of a plasma processing apparatus 300 according to a third embodiment. The second electrode 2 of the plasma processing apparatus 300 has a flat plate shape along the XY plane. The second electrode 2 is separated from the -Z side surface 10b of the workpiece 10, as in the second embodiment. However, in the plasma processing apparatus 300 of this embodiment, the second electrode 2 is not covered with a dielectric, and the second light-emitting gas 7 is not enclosed. Therefore, the plasma processing apparatus 200 only generates the atmospheric pressure plasma P2 in the gap G3 between the second electrode 2 and the -Z side surface 10b of the workpiece 10, and does not generate the ultraviolet light L2. Therefore, only the surface modification by the atmospheric pressure plasma P2 is performed on the -Z side surface 10b. Note that the surface modification by the atmospheric pressure plasma P1 and the ultraviolet light L1 is performed on the +Z side surface 10b.

[0069] 6B shows a main part of a plasma processing apparatus 350 which is a modified example of the third embodiment. In the plasma processing apparatus 350, the second electrode 2 is curved. By curving the second electrode 2, the distance between the first electrode 1 and the second electrode 2 can be kept constant, and the workpiece 10 can be processed with more uniform plasma.

[0070] <Fourth embodiment> 7, a plasma processing apparatus 400 according to a fourth embodiment is shown. In this embodiment, the workpiece is a long sheet 11. The plasma processing apparatus 400 is used together with a roll-to-roll type workpiece transport device 450. The plasma processing apparatus 400 and the workpiece transport device 450 form a plasma processing system 470.

[0071] The usage of the plasma processing apparatus 400 will be described. A roll 45 on which the long sheet 11 is wound is attached to a workpiece transport device 450. The long sheet 11 is sent toward the plasma processing apparatus 400 by the rotation of the roll 45 and the feed roller 28. The long sheet 11 unwound from the roll 45 enters the plasma processing apparatus 400. Before the long sheet 11 passes between the first electrode 1 and the second electrode 2, the long sheet 11 is supported by sandwiching both sides of the long sheet 11 between the transport rollers (25a, 25b) constituting the transport section 25. After the long sheet 11 passes between the first electrode 1 and the second electrode 2, the long sheet 11 is supported by sandwiching both sides of the long sheet 11 between the transport rollers (25c, 25d) constituting the transport section 25. By sandwiching and supporting the long sheet 11 between the transport rollers (25a, 25b, 25c, 25d), the long sheet 11 is accurately positioned in the Z direction perpendicular to the surface of the long sheet 11. This prevents the long sheet 11 from floating up or sinking between the first electrode 1 and the second electrode 2. The long sheet 11 which has been treated is sequentially wound up on a roll .

[0072] The above describes the embodiments and their modifications. However, the present invention is not limited to the above-described embodiments and modifications, and various modifications or improvements can be made to the above-described embodiments without departing from the spirit of the present invention. In addition, the embodiments and modifications can be combined. EXAMPLES

[0073] As the workpiece 10, three sets of PTFE sheets used as high-frequency circuit boards were prepared. Through holes with an inner diameter of 1 mm were formed in the PTFE sheets. The inner walls of the through holes were then plated, but prior to the plating, the surface of the PTFE sheets was modified so that the plating could easily adhere to the PTFE sheets. The degree of surface modification is a physicochemical index of the surface that enhances adhesive strength. The degree of surface modification may be evaluated by, for example, a water contact angle or the like, or oxidation-reduction may be evaluated by XPS or the like, in addition to the evaluation methods described below.

[0074] For sample S4, a PTFE sheet was subjected to surface modification using atmospheric pressure plasma and ultraviolet light for 10 seconds in the plasma processing device 100 shown in the first embodiment (FIG. 2). For sample S5, a PTFE sheet was subjected to surface modification using atmospheric pressure plasma and ultraviolet light for 20 seconds in the plasma processing device 100 shown in the first embodiment (FIG. 2). For sample S6, a PTFE sheet was subjected to wet fluoro-etching treatment using a chemical solution. Fluoro-etching treatment is known as a treatment for modifying the surface of a substrate using a chemical solution or plasma. For sample S7, a comparison sample was not subjected to surface modification.

[0075] A tensile test was performed to measure the plating strength of samples S4 to S7. A method of the tensile test will be described with reference to FIG. 8. FIG. 8 is an enlarged cross-sectional view of a main part of the work 10 (samples S4 to S7) for explaining the tensile test. A plating film 51 was formed on the inner wall of the through hole 15 of the work 10, i.e., samples S4 to S7. A tin-plated soft copper wire 55 was inserted into the plating film 51, and the plating film 51 and the tin-plated soft copper wire 55 were joined with lead-free solder 52. Then, the work 10 was fixed, and the tin-plated soft copper wire 55 was pulled in the direction T1 in the figure, to determine the tensile strength. Since the plating film 51 and the tin-plated soft copper wire 55 are firmly joined with the lead-free solder 52, breakage due to tension occurs between the through hole 15 and the plating film 51. Therefore, the adhesion between the through hole 15 of the work 10 and the plating film 51 can be evaluated by the tensile test. For the tensile test, a small tabletop testing machine EZ Test manufactured by Shimadzu Corporation was used.

[0076] The results of the tensile test are shown below. The results are expressed as relative values, with the tensile strength of the fluoro-etched sample S6 taken as 1. Sample S7 was unable to be measured in the tensile test due to poor plating.

[0077] [Table 2]

[0078] A comparison of Sample S4 and Sample S5 with Sample S7 shows that the surface modification by atmospheric pressure plasma and ultraviolet light enhances adhesion. A comparison of Sample S4 and Sample S5 with Sample S6 shows that the surface modification by atmospheric pressure plasma and ultraviolet light does not have as high an adhesive strength as the surface modification by fluoro-etching, but it does have high adhesive strength exceeding half (0.5) the tensile strength of the fluoro-etching. In other words, it was found that the surface modification by atmospheric pressure plasma and ultraviolet light can ensure sufficient adhesiveness for practical use. Also, as described above, the treatment by atmospheric pressure plasma and ultraviolet light in this embodiment is more cost-effective than the fluoro-etching treatment because of the simple device configuration, and is superior in terms of its small impact on the environment. [Explanation of symbols]

[0079] 1:First electrode 2 :Second electrode 3: First dielectric 4: First emitting gas 5: Power supply unit 6: Second dielectric 7: Second luminous gas 10: Work 11: Long sheet 20: Lamp House 21: Lamp house drive unit 25: Transport section 26: Z-direction drive unit 28: Feed roller 30: Gas supply section 31: Gas nozzle 40: Control section 41: Photodetector 42: Plasma detector 45, 46: Rolls (of long sheets) 100, 200, 300, 350, 400: Plasma treatment equipment 450: Work transport device 470: Plasma processing system G1,G2,G3: Gap L1,L2: Ultraviolet light P1, P2: Atmospheric pressure plasma

Claims

1. A plasma processing apparatus for processing a workpiece, comprising: a first electrode and a second electrode to which a power supply unit is connected; A first dielectric body having a tube shape covering the first electrode; A first luminous gas sealed inside the first dielectric material; a placement portion on which the workpiece is placed at a position spaced apart from the first dielectric; a plasma source gas present in a gap between the first dielectric and the workpiece; the first electrode, the first light-emitting gas, the first dielectric, the plasma source gas, and the second electrode are arranged in this order from the first electrode to the second electrode; a plasma source gas is generated by forming a potential difference between the first electrode and the second electrode, and ultraviolet light is generated from the first light-emitting gas at least inside the first dielectric between the first electrode and the second electrode.

2. The plasma processing apparatus according to claim 1 , wherein the first electrode extends generally in one direction.

3. The first electrode is characterized in that it has a coil shape. The plasma processing apparatus according to claim 2 .

4. 4. The plasma processing apparatus according to claim 1, wherein the plasma source gas is also present in a gap between the second electrode and the workpiece.

5. a tube-shaped second dielectric body covering the second electrode; A second luminous gas is sealed inside the second dielectric material, 5. The plasma processing apparatus according to claim 4, characterized in that, from the first electrode toward the second electrode, the first electrode, the first light-emitting gas, the first dielectric, the plasma source gas, the second dielectric, the second light-emitting gas, and the second electrode are arranged in this order.

6. a conveying unit that conveys the workpiece located between the first dielectric and the second electrode; a control unit that controls the transport unit so as to adjust a transport speed of the workpiece based on at least one of an intensity of the ultraviolet light emitted from the first light-emitting gas and an input energy for generating plasma from the plasma source gas; The plasma processing apparatus according to any one of claims 1 to 3, comprising:

7. A drive unit for moving at least one of the first electrode, the second electrode, and the placement unit in a direction perpendicular to a surface of the workpiece; a control unit that controls the drive unit so as to adjust a gap between the first electrode and the workpiece based on at least one of an intensity of the ultraviolet light emitted from the first light-emitting gas and an input energy for generating plasma from the plasma source gas; and The plasma processing apparatus according to any one of claims 1 to 3, comprising:

8. 4. The plasma processing apparatus according to claim 1, further comprising a gas supply unit for supplying the plasma source gas.

9. 4. The plasma processing apparatus according to claim 1, wherein at least one of the first electrode and the second electrode is arranged in a plurality of electrodes along the surface of the workpiece.

10. A conveying unit that conveys the workpiece, which is a long sheet, 4. The plasma processing apparatus according to claim 1, wherein the transport section supports the long sheet by sandwiching both sides of the long sheet.

11. carrying the workpiece into a plasma processing apparatus including a first electrode and a second electrode to which a power supply unit is connected, a tubular first dielectric covering the first electrode, a first light-emitting gas sealed inside the first dielectric, and a plasma source gas present in a gap between the first dielectric and the workpiece, such that the workpiece is arranged in the following order from the first electrode toward the second electrode: the first electrode, the first light-emitting gas, the first dielectric, the plasma source gas, the workpiece, and the second electrode; generating a plasma from the plasma source gas by forming a potential difference between the first electrode and the second electrode, and generating ultraviolet light from the first luminescent gas between the first electrode and the second electrode and at least inside the first dielectric; treating the carried-in workpiece with plasma generated from the plasma source gas and ultraviolet light emitted from the first light-emitting gas; A plasma processing method comprising:

12. 12. The plasma processing method according to claim 11, wherein the workpiece is a circuit board having at least one of a through hole and a via.

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