JP5368114B2 - Pt / Rh electrode for plasma generation, plasma generation apparatus, and plasma processing apparatus - Google Patents

Description

  The present invention relates to a plasma generating electrode, and more particularly, a plasma generating electrode that generates plasma of a supply gas by discharge, a plasma generating apparatus that generates plasma using this electrode, and a surface of an object to be processed. The present invention relates to a plasma processing apparatus.

  The plasma generator has characteristics of the plasma generated by the discharge according to the electrode shape, applied voltage characteristics, raw material and its supply form, etc., and the discharge phenomenon that generates plasma is glow discharge, abnormal glow discharge Radio Frequency (RF) discharge or corona discharge. For example, arc plasma generated by arc discharge is stabilized by cooling with an air flow or water cooling wall from the outer periphery in the injection direction, so that it has excellent controllability and high energy density at high temperatures. Used for processing and surface treatment. Furthermore, arc discharge is a discharge that occurs in a wide range of pressures from vacuum to atmospheric pressure, and various source gases (hereinafter referred to as “working gases”) can be easily converted into plasma. Accordingly, a desired surface treatment can be performed. Surface processing (etching, surface coating, etc.) and surface modification (improvement of wettability) according to the raw material gas and power supply by plasma processing the surface of workpieces such as semiconductor products, metal products, glass products, and processing members , Improvement of adhesiveness, improvement of biocompatibility), washing and desmear treatment, powder synthesis, thin film formation, and the like.

  A metal having a high melting point and a small work function is used for the plasma generating electrode, and tungsten (W), molybdenum (Mo), or the like is used as an electrode material. As shown in FIG. 37, the plasma arc torch described in Japanese Patent Laid-Open No. 10-296445 (Patent Document 1) and Japanese Patent Laid-Open No. 11-285834 (Patent Document 2) is provided with a rod-shaped electrode 108 made of tungsten. A nozzle electrode 116 is disposed on the outer periphery of the tip of the rod electrode 108. That is, a voltage is applied between the rod-shaped electrode 108 and the nozzle-shaped electrode 116 to generate plasma, and the plasma P is ejected from the ejection port 116a of the nozzle-shaped electrode 116 in a jet shape.

  As described above, FIG. 37 is a schematic diagram of plasma generation in the conventional plasma generation electrode. When the tungsten rod-shaped electrode 108 described in Patent Documents 1 and 2 is used as the plasma generation electrode, the tip of the electrode is formed. The wear material particles 109 are released from the electrode points 108b on the surface 108a. In the electric discharge machining technique described in Japanese Patent Application Laid-Open No. 2004-358623 (Patent Document 3), an alloy in which copper (Cu) or silver (Ag) is blended with W or Mo is used to reduce electrode wear as described above. Although it is used as an electrode material for electric discharge machining to reduce electrode wear, significant suppression of wear has not been realized.

In addition, as a plasma generating electrode used in an arc plasma generating apparatus, there is a grinding arc type electrode. Czemichowski: Gliding Arc. Applications to engineering and environment control, Pure and Applied Chemical, Vol. 666 (1994) pp. 1301-1310 (Non-Patent Document 1) and the like. Grinding arc electrodes can generate arc plasma by generating arc discharge at or near atmospheric pressure, creating a long-life, stable, high-purity arc plasma. There has been a demand for a mold electrode material.
As will be described later, in this specification, data described in “THE PGM DATABASE” http://www.platinummetalsreview.com/jmpgm/index.jsp (Non-patent Document 2) is cited.
JP-A-10-296445 Japanese Patent Laid-Open No. 11-285834 JP 2004-358623 A A. Czemichowski: Gliding Arc. Applications to engineering and environment control, Pure and Applied Chemical, Vol. 66 (1994) pp.1301-1310 “THE PGM DATABASE” http://www.platinummetalsreview.com/jmpgm/index.jsp

  As described above, when the rod-shaped electrode 108 made of tungsten shown in FIG. 37 is used, the wear material particles 109 are discharged together with the plasma P from the electrode point 108b. This is caused by spark wear due to an explosion phenomenon of the electrode point 108b or oxidation wear that peels off the oxidized electrode front end surface 108a. Therefore, when plasma processing is performed using a conventional plasma generating electrode, a large amount of wear material particles 109 adhere to the surface of the workpiece 122, and high-precision surface processing, uniform surface processing, or the like can be performed. could not. As a phenomenon in which the electrode material sublimates and evaporates and decreases and wears without being accompanied by the release of wear material particles, there is evaporation wear due to surface heating by Joule heat or plasma radiation.

  FIG. 38 is an enlarged photograph of the electrode tip when arc plasma is generated using a conventional rod-shaped electrode 108 made of W or Cu. (38A) As shown in the enlarged photograph of the upper and middle stages, tungsten oxide that has been peeled off by oxidation is formed on the periphery of the tip of the tungsten (W) rod-shaped electrode, and a large amount of wear material particles are rod-shaped. It can be seen that it was released from the electrode tip. (38A) From the electron microscope image shown in the lower part, it can be seen that the end surface of the rod-like electrode becomes brittle due to oxidation and is easily peeled off. That is, even when a high melting point electrode material (melting point of W: 3704 ° C.) is used, if the metal material is easily oxidized, it is not suitable as an electrode material for plasma generation and is described in Patent Documents 1 and 2. When a plasma torch is used for processing an object to be processed, a large amount of impurities are adhered.

  Further, (38B) of FIG. 38 shows the state of the tip of the rod-shaped electrode when arc plasma is generated using a copper rod-shaped electrode (Cu melting point: 1084 ° C.) having a relatively low melting point. (38B) In the upper enlarged photograph, it can be seen that the tip of the copper rod-shaped electrode is severely worn and a large amount of wear material particles are released. (38B) In the enlarged photograph shown in the middle stage, a large crater-like wear part of about several tens of μm to 100 μm or more is formed. Furthermore, (38B) the lower stage electron microscope image has fine wear parts of about 10 μm or less. (38B) From the enlarged photograph shown in the middle and lower stages, various wear material particles of various sizes can be seen. It turns out that it discharge | releases from the rod-shaped electrode front-end | tip.

  As a result of the plasma generation test using the rod-shaped electrode made of W or Cu, in Patent Document 3, when an alloy made of W and Cu is used as an electrode material, electrode wear due to arc discharge is effectively reduced. The result confirms that it was not done. That is, it is shown that W, Cu, and alloys thereof are not suitable electrode materials for arc discharge electrodes. Therefore, when arc plasma is generated using an electrode for arc discharge formed from a conventional electrode material, and surface processing or surface modification is performed by this arc plasma, wear material particles are released to the surface of the workpiece. Since the adhering material particles are mixed as impurities in the coating film, uniform surface treatment cannot be performed.

  FIG. 38 shows the results of a conventional plasma generating electrode used for generating arc plasma, but similar results are obtained when plasma is generated by glow discharge, abnormal glow discharge, RF discharge or corona discharge. It is done. That is, when the plasma is generated, the electrode surface reaches a temperature at which oxidation or evaporation can occur, and when a conventional plasma generation electrode is used, wear material particles are generated due to electrode wear, and a desired plasma treatment can be performed. It was difficult. In particular, in the abnormal glow discharge, since the electrode becomes high temperature, an electrode for plasma generation having high heat resistance has been demanded.

  The object of the present invention is to provide an electrode for plasma generation and a plasma generation apparatus that can significantly reduce the emission of wear material particles when the plasma is generated by electric discharge, reduce electrode wear, and have a long life. It is an object of the present invention to provide a plasma processing apparatus that performs high-precision surface processing or surface modification that imparts desired physical properties to the surface of the processing object.

The present invention has been made to solve the above problems, and a first aspect of the present invention is a plasma generation electrode of a plasma generation apparatus that generates plasma of a supply gas by discharge, and this plasma generation At least the discharge surface of the electrode for plasma is a plasma generating electrode formed from an electrode material of Pt.Rh metal represented by Pt 1 _-Y Rh _Y (0 <Y <1).

  A second aspect of the present invention is the plasma generating electrode according to the first aspect, wherein the Pt / Rh-based metal has a lattice constant a in the range of 3.80 to 3.92.

  A third aspect of the present invention is the plasma generating electrode according to the first or second aspect, wherein the melting point of the Pt / Rh metal is in the range of 1773 ° C. to 1966 ° C.

  A fourth aspect of the present invention is the plasma generating electrode according to any one of the first to third aspects, wherein the crystal structure of the Pt / Rh-based metal is a face-centered cubic lattice (FCC) structure.

  A fifth aspect of the present invention is the plasma generating electrode according to any one of the first to fourth aspects, wherein the crystal grain size of the Pt / Rh-based metal is in the range of 0.5 μm to 100 μm.

In a sixth aspect of the present invention, in any one of the first to fifth aspects, the density ρ of the Pt · Rh-based metal is in the range of 12.41 g / cm ^{3 to} 21.45 g / cm ^3. Electrode.

  A seventh aspect of the present invention is the plasma generating electrode according to any one of the first to sixth aspects, wherein the Pt / Rh metal has a Vickers hardness HV in the range of 50 Hv to 130 Hv.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, when the weight ratio of Rh to the Pt / Rh-based metal is X wt%, the lattice constant of the Pt / Rh-based metal is The a-X relational expression between a (Å) and the X weight% is a = −0.00113X + 3.908 ± 0.02.
This is a plasma generating electrode in which the lattice constant a is set by adjusting the weight ratio of Rh.

According to a ninth aspect of the present invention, in any of the first to eighth aspects, when the weight ratio of Rh to the Pt / Rh metal is X wt%, the melting point T of the Pt / Rh metal (° C.) and the X-wt% TX relational expression is T = −1.4890X + 1836.3 ± 70
Or when the X weight% is in the range of 0 ≦ X ≦ 30, the TX relational expression is T = −5.255X + 1785.3 ± 15
And the melting point T is set by adjusting the weight ratio of Rh.

According to a tenth aspect of the present invention, in any one of the first to ninth aspects, when the weight ratio of Rh to the Pt / Rh metal is X wt%, the density ρ of the Pt / Rh metal is ρ. (G / cm ³ ) and the ρ-X relational expression of X weight% is ρ = −0.08401X + 20.87 ± 0.6
And the density ρ is set by adjusting the weight ratio of the Rh.

In an eleventh aspect of the present invention, in any one of the first to tenth aspects, when the weight ratio of Rh to the Pt / Rh-based metal is X wt%, the Vickers hardness of the Pt / Rh-based metal The HV-X relational expression of HV (Hv) and the X weight% is HV = −2.76X + 51.85 ± 15
And the Vickers hardness HV is set by adjusting the weight ratio of the Rh.

  In a twelfth aspect of the present invention, in any one of the first to eleventh aspects, the weight ratio of Rh in the Pt / Rh-based metal is set to a range of 0 wt% to 40 wt%. Electrode.

  According to a thirteenth aspect of the present invention, in any one of the first to twelfth aspects, the electrode in which the discharge is generated is a high electric field electrode (= high voltage electrode; an electrode to which a voltage having a larger absolute value is applied. ) And a low electric field electrode (= low voltage electrode; an electrode to which a voltage having a smaller absolute value is applied, for example, a ground electrode), and the discharge surface is disposed on the opposing surface of the high electric field electrode. A plasma generating electrode in which at least a discharge surface of the high electric field electrode is formed of the electrode material.

  In a fourteenth aspect of the present invention, in the thirteenth aspect, the high electric field electrode is a rod-shaped electrode, the low electric field electrode is a nozzle-shaped electrode having a plasma injection port, and the electrode constitutes a pen jet electrode. The plasma generating electrode according to claim 11.

  A fifteenth aspect of the present invention is the plasma generating electrode according to the fourteenth aspect, wherein at least the tip of the rod-shaped electrode is formed from the electrode material.

  A sixteenth aspect of the present invention is the plasma generating electrode according to the thirteenth aspect, wherein the high electric field electrode is a protruding electrode having one or more protrusions on the discharge surface side.

  A seventeenth aspect of the present invention is a plasma generation apparatus that generates plasma using the plasma generation electrode according to any one of the first to sixteenth aspects.

  An eighteenth aspect of the present invention is a plasma processing apparatus for performing plasma processing on the surface of an object to be processed by the plasma generation apparatus according to the fifteenth aspect.

According to the first aspect of the present invention, at least the discharge surface of the plasma generating electrode for generating plasma is made of Pt.Rh-based metal electrode material represented by Pt 1 _-Y Rh _Y (0 <Y <1). Since it is formed, electrode wear can be greatly reduced, and release of wear material particles can be suppressed to a very small amount. The Pt / Rh-based metal is formed of a Pt—Rh alloy, and the Pt metal or Pt—Rh alloy forms a crystallite, and the crystallite constitutes a polycrystalline metal. It has been confirmed by observation with a scanning ion microscope that the Pt—Rh alloy according to the present invention forms crystallites. Compared to high melting point electrode materials such as W used for conventional plasma generation electrodes, the melting point of the Pt / Rh metal according to the present invention is low, and the melting point of W is 3704 ° C. The melting point of the bulk metal is 1773.degree. C., and the melting point of the bulk metal of Rh is 1960.degree. As will be described later, when the Pt / Rh-based metal is a Pt—Rh alloy, the content ratio of the Rh element is indicated by a weight ratio, and the composition ratio Y and the X weight% indicating the weight ratio are: X = 100 × 102.9 × Y / {195.1 × (1−Y) + 102.9 × Y}, the atomic weight of Pt is 195.1, and the atomic weight of Rh is 102.9. Is used. Therefore, the composition ratio Y is expressed by Y = 195.1 × X / {102.9 × (100−X) + 195.1 × X} using X wt%.

As a result of diligent research, the present inventors have conceived that oxidation resistance is an important factor for wear of the plasma generating electrode, and Pt and Rh have excellent oxidation resistance and heat resistance. Attention has been paid to the fact that a plasma generating electrode (also referred to as a “Pt / Rh-based electrode for plasma generation”) in which at least the discharge surface is formed of a Pt / Rh-based metal has been completed. This electrode for plasma generation can be used for generation of plasma by arc discharge, glow discharge, abnormal glow discharge, RF discharge or corona discharge, and can suppress electrode wear at the time of plasma generation. Thus, the electrode wear suppression effect becomes more remarkable as the discharge surface becomes higher in temperature. Furthermore, if the electrode for plasma generation according to the present invention is used, the release of wear material particles is suppressed to a very small amount. Therefore, plasma spraying can be performed by converting the working gas into plasma and mixing raw material powder or raw material gas. A high-purity coating film can be formed on the surface of the object to be processed by a thermal plasma CVD method or the like.
Furthermore, since the release of wear material particles is greatly suppressed, fine processing can be performed with high precision in thin film processing (for example, micro processing / removal of diamond thin film, micro processing / removal of diamond-like carbon film). it can. In addition, when the object to be processed is a metal material, if the plasma generated by the plasma generating electrode according to the present invention is used for melting and refining metal, thermal decomposition, reduction of metal oxide, etc., Mixing of wear material particles is prevented. Furthermore, if the desired working gas is turned into plasma and irradiated onto the surface of the object to be processed, the release of wearable material particles is suppressed, resulting in uniform surface modification (improvement of wettability, improvement of adhesion, improvement of biocompatibility, etc.) ), Cleaning, desmear treatment, etc. can be performed with high efficiency.

  According to the second embodiment of the present invention, since the lattice constant a is in the range of 3.80 to 3.92 mm, the Pt / Rh-based metal according to the present invention has less solid solution of impurities and suitable processing. It is possible to provide a discharge surface of an electrode for plasma generation having desired physical properties and shape from this electrode material. That is, when the lattice constant is smaller than 3.80 mm, the hardness increases and machining becomes difficult. On the other hand, when the lattice constant a is larger than 3.92 mm, impurities are easily dissolved, and it is difficult to impart desired characteristics to the plasma generating electrode. As a result of intensive studies, the present inventors have clarified a lattice constant suitable as the electrode material and have specified the range of the lattice constant.

  According to the third aspect of the present invention, since the melting point of the Pt / Rh metal is set in a range of 1773 ° C. to 1966 ° C., the discharge surface is suitably softened during plasma generation, and the wear material particles Release can be suppressed. One of the causes of the generation of wear material particles is an explosion phenomenon (spark wear) on the discharge surface. When a refractory metal material (W, Mo, etc.) is used as an electrode material, a hardness of a predetermined level or higher is obtained even at a high temperature. Since it is maintained, it is considered that the wear material particles are likely to be released due to spark wear. In the case of the Pt / Rh-based metal according to the present invention, it has excellent oxidation resistance, the melting point can be set in a suitable range, the discharge surface is suitably softened during plasma generation, and the wear material due to spark wear The release of particles can be suppressed to a very small amount. When at least the discharge surface of the plasma generating electrode is formed from a Pt—Rh alloy, the content of Rh relative to Pt is adjusted according to the application of the plasma and the type of working gas, and the electrode material is in the range of 1773 ° C. to 1966 ° C. The melting point of can be set to a suitable temperature. Further, other base metals (Ni and the like), preferably other noble metals (Ir and the like) can be further contained, but in that case, the melting point is set in the range of 1773 ° C. to 1966 ° C., The occurrence of spark wear can be suppressed. Furthermore, in consideration of the mechanical strength of the electrode material, the melting point is more preferably set in the range of 1773 ° C. to 1932 ° C., and it can be optimized when it is in the range of 1850 ° C. to 1932 ° C. It is clear from.

  According to the fourth aspect of the present invention, the Pt metal or Pt—Rh alloy forming the Pt · Rh-based metal forms a crystallite, and the crystal structure of the crystallite is a face-centered cubic lattice (FCC) structure. Have. In general, a face-centered cubic lattice metal is easy to process and has a high filling rate, so that solid solution of impurities is suppressed. Therefore, if the Pt / Rh metal according to the present invention is used for the electrode material, it has suitable electrical characteristics, and the electrode material can be easily processed into a predetermined shape to constitute a plasma generating electrode. .

  According to the fifth aspect of the present invention, since the crystal grain size of the Pt / Rh-based metal is in the range of 0.5 μm to 100 μm, suitable sputtering resistance is imparted to the electrode material, and the discharge surface is formed. It can be kept uniform. It has been confirmed that when the crystal grain size is larger than 100 μm, the sputtering resistance is deteriorated and a discharge surface suitable for plasma generation cannot be maintained. When the crystal grain size is smaller than 0.5 μm, the sputter resistance is improved, but a very large amount of wear particles tends to be easily generated. Therefore, by setting the crystal grain size in the range of 0.5 μm to 100 μm, it is possible to generate uniform plasma with less wear particles using the plasma generating electrode according to the present invention.

According to the sixth aspect of the present invention, since the density ρ of the Pt · Rh-based metal is in the range of 12.41 g / cm ^{3 to} 21.45 g / cm ³ , the amount of impurities contained in the electrode material is increased. In addition to the reduction, the porous surface of the discharge surface can be suppressed during electrode formation and / or plasma generation. When the density ρ is greater than 21.45 g / cm ³ , the absolute amount of impurities increases and it becomes difficult to suppress the mixing of impurities, and it is difficult to set the electrical characteristics of the plasma generating electrode to a predetermined value. In addition, there is a possibility that the impurities are mixed in the plasma together with the wear particles. Further, if the density ρ is smaller than 12.41 g / cm ³ , the discharge surface tends to become porous during electrode formation and / or plasma generation, which is one of the factors that increase the generation of wear particles. There was a concern. Therefore, by setting the density ρ of the Pt · Rh-based metal in the range of 12.41 g / cm ^{3 to} 21.45 g / cm ³ , it is possible to reduce the contamination of impurities and wear particles into the plasma. .

  According to the seventh aspect of the present invention, since the Vickers hardness HV of the Pt / Rh-based metal is in the range of 50 Hv to 130 Hv, generation of wear particles can be reduced and suitable hardness is imparted to the discharge surface. can do. If the Vickers hardness HV exceeds 130 Hv, the discharge surface becomes brittle, and it becomes difficult to process the plasma generating electrode into a predetermined shape. Further, the generation of the wear particles tends to increase. Therefore, the Pt / Rh-based metal according to the present invention has a Vickers hardness HV set in a range of 50 Hv to 130 Hv, so that it has a suitable durability, generates a small amount of wear particles, and has a desired shape. A generating electrode can be provided.

According to the eighth embodiment of the present invention, the a-X relational expression of the lattice constant a (Å) of the Pt · Rh-based metal and the X weight% is a = −0.00113X + 3.908 ± 0.02.
Therefore, the discharge surface can be formed from an electrode material having a predetermined lattice constant a by adjusting the weight ratio of Rh. The present inventors clarified the lattice constant of a suitable electrode material from the results of plasma treatment using the electrode for plasma generation and the analysis based on the X-ray diffraction (XRD) measurement of the electrode material, and from these experimental results The aX relational expression is derived. That is, the dependence of the lattice constant a on the X weight% is derived in a range in which a good plasma generation is possible by changing the weight ratio of Rh. Therefore, an electrode material having a desired lattice constant can be selected according to the content of Rh to form a plasma generating electrode. When the weight ratio of Rh is 30% by weight, the lattice constant a can be set to 3.874 ± 0.02Å. That is, the lattice constant a can be set within the range of 3.854 to 3.894. When the weight ratio of Rh is 40% by weight, the lattice constant a can be set to 3.863 ± 0.02 mm (within a range of 3.843 mm to 3.883 mm). Therefore, by adjusting the weight ratio of Rh, the lattice constant a can be easily set in the above-described lattice constant range of 3.80 to 3.92 示 し shown in the second embodiment.

According to the ninth embodiment of the present invention, the first T-X relational expression of the melting point T (° C.) of the Pt · Rh-based metal and the X weight% is T = −1.4890X + 1836.3 ± 70.
Therefore, the melting point T (° C.) can be set to a predetermined temperature range by adjusting the weight ratio of the Rh. When the X wt% is 30 wt%, the melting point T (° C.) can be set to 1881 ± 70 ° C. (within a range of about 1811 ° C. to about 1951 ° C.), and the X wt% is 40 wt% In this case, the melting point T (° C.) can be set to 1896 ± 70 ° C. (within a range of about 1826 ° C. to about 1966 ° C.).
Further, when the X weight% is in the range of 0 ≦ X ≦ 30, the second TX relational expression is
T = −5.255X + 1785.3 ± 15
Since the error range is small, the weight ratio of the Rh can be adjusted in the range of 0 ≦ X ≦ 30, and the melting point T (° C.) can be more reliably set within the predetermined temperature range. it can. In the ninth embodiment, the Rh content dependency of the melting point T (° C.) is derived by an approximately linear function. As will be described later, since the Rh content dependency is not strictly a linear function, the slope of the TX relational expression changes greatly in the range of 0 ≦ X ≦ 30 and 30 <X ≦ 100. Accordingly, based on the measurement data in the range of 0 ≦ X ≦ 30, the second TX relational expression is derived and applied to the Pt / Rh-based metal in which the X wt% is 0 wt% to 30 wt%. Thus, the melting T can be set with higher accuracy. When the second TX relational expression is applied, when the X wt% is 30 wt%, the melting point T (° C.) is set to 1890 ± 15 ° C. (within a range of about 1875 ° C. to about 1905 ° C.). can do.
As described above, by setting the melting point T (° C.) within a predetermined temperature range, it is possible to improve the workability of the electrode material and to suppress the generation amount of the wear particles during plasma generation. Therefore, since the melting point T (° C.) can be easily set by the Rh content of the Pt / Rh-based metal, a high-performance plasma generating electrode can be manufactured at a low cost.

According to the tenth aspect of the present invention, the density ρ (g / cm ³ ) of the Pt · Rh-based metal and the ρ-X relational expression of the X weight% is ρ = −0.08401X + 20.87 ± 0.6
Therefore, the density ρ can be set within a predetermined density range by adjusting the weight ratio of the Rh. The ρ-X relational expression is derived by clarifying the density of a suitable electrode material based on the result of plasma processing using a plasma generating electrode and density measurement. As described above, the impurity content and the like change according to the density ρ (g / cm ³ ), which affects the electrical characteristics of the plasma generating electrode such as the resistance value. Therefore, since the density ρ of the Pt / Rh metal can be easily controlled using the ρ-X relational expression, it is possible to provide a plasma generation electrode having desired electrical characteristics. When X wt% is 30% by weight, by setting the density ρ in 18.26 ± 0.6g / cm ³ (in the range of from about 17.66 g / cm ³ ~ about 18.86g / cm ³⁾ It can be the case X wt% is 40 wt%, the melting point T (° C.) and 17.51 ± 0.6g / cm ³ (about 16.91g ^/ cm 3 ~18.11 about g / cm ³ (Within range).
According to the eleventh aspect of the present invention, the HV-X relational expression of the Vickers hardness HV (Hv) of the Pt · Rh-based metal and the X weight% is HV = −2.76X + 51.85 ± 15
Therefore, the Vickers hardness HV can be set within a predetermined range by adjusting the weight ratio of the Rh. As described above, by setting the Vickers hardness HV within a predetermined range, it is possible to impart suitable workability to the electrode material and to suppress the generation of wear particles during plasma generation. For example, when the X weight% is 30 weight%, the Vickers hardness HV can be set to 135 ± 15 Hv (within a range of about 120 Hv to about 150 Hv), and the X weight% is 20 weight%. The Vickers hardness HV (Hv) can be set to 107 ± 15 Hv (within a range of about 92 Hv to about 122 Hv).

  According to the twelfth aspect of the present invention, since the weight ratio of Rh in the Pt / Rh metal is set in the range of 0 wt% to 40 wt%, the electrode material has a suitable mechanical strength. In addition, the life of the plasma generating electrode can be extended and can be easily processed into a desired shape. Therefore, it is possible to provide plasma generation electrodes having various shapes according to applications, such as for pen jets and grinding arcs. When the Rh content of the Pt / Rh-based metal increases, the amount of wear of the electrode in the arc discharge decreases. The mechanical strength of the plasma generating electrode increases when the Rh weight ratio exceeds 40% by weight. It has been confirmed from experiments that the remarkably decreases. That is, when the weight ratio of Rh contained in the Pt / Rh metal is set in the range of 0 to 40% by weight, the hardness, tensile strength, toughness and the like suitable for the plasma generating electrode according to the present invention are obtained. Is granted. Furthermore, in the above experimental results, a more suitable mechanical strength can be obtained when the weight ratio of Rh is set to 10 to 30% by weight.

Further, using the relational expressions used in the eighth to eleventh embodiments, when the weight ratio of Rh is in the range of 0 to 40% by weight, the lattice constant a is 3.863 ± 0.02Å to 3. It can be set in the range of 908 ± 0.02 mm. Further, the melting point T can be set in a range of 1836 ± 70 ° C. to 1896 ± 70 ° C., and the density ρ is set to 17.51 ± 0.6 g / cm ^{3 to} 20.87 ± 0.6 g / cm ^3. Can be set in the range.

  According to the thirteenth aspect of the present invention, when a discharge is generated in an electrode configured by facing a high field electrode and a low field electrode, the discharge surface on the facing surface side of the high field electrode is Since it is formed from an electrode material, it is possible to suppress the emission of wear material particles due to a high electric field. Here, the high electric field electrode corresponds to a high voltage electrode (cathode) to which a voltage having a larger absolute value is applied and emits electrons, and the low electric field electrode has an absolute value higher than that of a ground electrode, for example. It corresponds to a low voltage electrode (anode) to which a small voltage is applied. However, depending on how the voltage is applied, the reverse may be the case, such as when the high field electrode is the anode and the low field electrode is the cathode. When the structure of the discharge surface that concentrates the electric field on the electrode that causes the discharge, such as the tip of a protrusion provided on the electrode surface or the tip of a needle electrode, is formed, the electrode having such a structure is compared with the opposite electrode. The electric field concentrates to form a high field electrode. Here, the opposing electrode has a lower electric field or applied voltage than the high electric field electrode, and constitutes a low electric field electrode. Therefore, if at least the discharge surface of the high electric field electrode is formed from the electrode material of the Pt / Rh metal, the generation of wear material particles can be suppressed and high purity plasma can be generated.

  According to the fourteenth aspect of the present invention, since the high electric field electrode is a rod-shaped electrode, the low electric field electrode is the nozzle-shaped electrode, and the electrode constitutes a pen jet electrode, the plasma according to the present invention. Using the generation electrode, it is possible to generate a high-purity jet plasma flow with an extremely low content of the wear material particles. The pen jet electrode is composed of a nozzle-like electrode having a plasma injection port on the tip side of the rod-like electrode, and a voltage is applied to the rod-like electrode and the nozzle-like electrode so that the tip surface of the rod-like electrode and the vicinity of the tip surface are Concentrate the electric field on the discharge surface. Therefore, by forming at least the tip surface of the rod-shaped electrode and the discharge surface near the tip surface from a Pt / Rh-based metal, the wear material particles are released from the tip surface and the tip surface vicinity where the electric field is concentrated. Can be suppressed.

  Further, in the pen jet type electrode, it is possible to cool the plasma flow by providing a water cooling part on the outer periphery of the plasma generating part or by introducing an air flow, to easily control the size of the flux and to stabilize it. it can. Therefore, by forming the discharge surface from a Pt / Rh-based metal and generating a high-purity jet plasma flow, the plasma is irradiated to a predetermined region on the surface of the object to be processed without depositing / mixing impurities. Uniform surface processing and surface modification can be performed. Moreover, a tubular electrode can be used as the rod-shaped electrode, and an arc plasma of the working gas can be generated by supplying a working gas into the tube and applying a voltage to the tip of the tubular electrode and the inner surface of the nozzle-like electrode. .

  According to the fifteenth aspect of the present invention, since at least the tip of the rod-shaped electrode is integrally formed of a Pt / Rh-based metal, it is possible to easily manufacture a plasma generating electrode with very little electrode wear and a long life. it can. That is, since at least the entire tip of the rod-shaped electrode is formed of the electrode material, no special processing such as coating of the rod-shaped electrode of the Pt / Rh metal is required, and the discharge surface is made of Pt / Rh. The rod-shaped electrode made of a base metal can be manufactured. Furthermore, since at least the entire tip of the rod-shaped electrode is formed of the Pt / Rh metal, the discharge surface of the Pt / Rh metal is not lost due to the accumulation of a small amount of electrode wear, and the plasma generating electrode It is possible to extend the service life. Also, by exchanging only the tip formed from the Pt / Rh metal, it can be used as a plasma generating electrode, compared to the case where the entire rod-shaped electrode is formed from an expensive Pt / Rh metal. The manufacturing cost of the plasma generating electrode can be reduced.

  According to the sixteenth aspect of the present invention, since the high electric field electrode is a protruding electrode having one or more protrusions on the discharge surface side, the electric field is concentrated on the one or more protrusions formed on the discharge surface. And plasma can be generated with high efficiency. Furthermore, as described above, since the discharge surface of the protruding electrode that concentrates the electric field is formed from the Pt / Rh-based metal, the electrode wear is suppressed, and high-purity plasma with very little contamination of wear material particles is generated. It can be generated with high efficiency.

  According to the seventeenth aspect of the present invention, since the plasma is generated using the plasma generation electrode according to any one of the first to seventh aspects, a plasma generation apparatus that emits high-purity plasma stably for a long time is provided. Can be provided. The working gas supplied to the plasma generating apparatus according to the present invention may be any gas or vapor. For example, indoor air, dry air, humidified air, helium, argon, oxygen, nitrogen, hydrogen, hydrogen sulfide, carbonization By appropriately selecting hydrogen gas and a mixed gas thereof according to the purpose, it is possible to generate high-purity plasma with very little contamination of the wear material particles. Moreover, powder can also be mixed with those working gas. The pressure range of the working gas is not limited to the following range, but the lower limit of the pressure is about 1/10 (about 0.1 atm) of atmospheric pressure as a pressure condition with little electrode evaporation, The upper limit is preferably up to about 10 atm as a value at which the working gas can be safely used. Furthermore, it is more preferable that the pressure of the working gas is set in a range of 0.5 to 5 atm, and a desired plasma is stably generated by a plasma generation apparatus equipped with a pen jet type electrode or a grinding arc type electrode. Can be made.

  According to the eighteenth aspect of the present invention, since the surface of the object to be processed is subjected to plasma processing by the plasma generating apparatus of the eighth aspect, the wear material particles adhere to, deposit, and mix as impurities on the surface of the object to be processed. Can be prevented. Furthermore, by suppressing electrode wear, the surface treatment of the surface of the workpiece can be continuously performed for a long time. According to the plasma processing apparatus of the present invention, the above-described plasma spraying, thermal plasma CVD method, thin film processing, metal refining and thermal decomposition, metal oxide reduction, surface modification, cleaning and desmear treatment, powder synthesis -Plasma processing such as processing and thin film formation can be performed with extremely reduced contamination / deposition of the wear material particles.

FIG. 1 is a schematic configuration diagram of a plasma processing apparatus having a pen jet electrode according to the present invention. FIG. 2 is a photograph showing an image of plasma emitted from the injection port of the pen jet type plasma processing apparatus according to the present invention. FIG. 3 is a schematic cross-sectional view of a plasma generating apparatus having a dual-electrode water-cooled pen jet electrode according to the present invention. FIG. 4 is a schematic cross-sectional view of the electrode tip according to the present invention. FIG. 5 is an enlarged photograph of an electrode tip portion obtained by imaging the Pt / Rh metal electrode tip portion according to the present invention and each electrode tip portion made of a comparative Pt—Ir alloy after arc discharge. FIG. 6 is an enlarged photograph of the Pt metal electrode tip according to the present invention imaged after plasma generation. FIG. 7 is an enlarged photograph after discharge of each electrode tip portion made of a Pt—Ir alloy (7A) and a Pt—W alloy (7B) as comparative examples. FIG. 8 is a graph showing the power dependence of the electrode wear amount using the electrode tip of Pt metal and Pt—Rh alloy according to the present invention and the Pt—Ir alloy electrode tip of the comparative example. FIG. 9 is an optical micrograph of the surface of the workpiece processed by the plasma processing apparatus according to the present invention. FIG. 10 is a graph showing the accumulated wear amount (mg) with respect to the accumulated discharge time (min) of the electrode tip portion made of the Pt / Rh-based metal according to the present invention and various metals as comparative examples. FIG. 11 is a graph showing the discharge time dependence of the amount of wear in a plasma generating electrode using the Pt—Rh alloy according to the present invention as an electrode material. FIG. 12 is a graph showing the results of XRD analysis of a Pt / Ph metal according to the present invention. FIG. 13 is an enlarged graph showing the inside of the broken line in FIG. FIG. 14 is a graph showing a lattice constant with respect to the Rh content (% by weight) of the Pt / Rh metal according to the present invention. FIG. 15 is a state diagram of a Pt—Rh alloy which is an electrode material according to the present invention. FIG. 16 is a table showing melting points of the Pt / Rh metal and other metals and alloys according to the present invention. FIG. 17 is a graph in which the melting point of the Pt / Rh metal according to the present invention is plotted against the weight ratio of Rh (X wt%). FIG. 18 is a graph plotting the melting point of the Pt / Rh metal according to the present invention against the weight ratio of Rh (X wt%). (0% to 30% by weight) FIG. 19 is a graph in which the density ρ of the Pt / Rh metal according to the present invention is plotted against the weight ratio (X wt%) of Rh. FIG. 20 is a graph in which the Vickers hardness HV of the Pt / Rh metal according to the present invention is plotted against the weight ratio (X wt%) of Rh. FIG. 21 shows a secondary electron image (21A) and a reflected electron image (21B) on the surface of the Pt electrode. (Magnification: 1000 times) FIG. 22 shows a secondary electron image (22A) and a reflected electron image (22B) on the surface of the Pt electrode. (Magnification: 10,000 times) FIG. 23 shows a secondary electron image (23A) and a reflected electron image (23B) on the surface of the Pt electrode. (Magnification: 30000 times) FIG. 24 shows a secondary electron image (24A) and a reflected electron image (24B) on the electrode surface of the Pt / Rh metal (Rh is 10% by weight) according to the present invention. (Magnification: 1000 times) FIG. 25 is a secondary electron image (25A) and a reflected electron image (25B) on the electrode surface of the Pt / Rh metal (Rh is 10% by weight) according to the present invention. (Magnification: 10,000 times) FIG. 26 is a secondary electron image (26A) and a reflected electron image (26B) on the electrode surface of the Pt / Rh metal (Rh is 10% by weight) according to the present invention. (Magnification: 30000 times) FIG. 27 is a secondary electron image (27A) and a reflected electron image (27B) on the electrode surface of the Pt / Rh metal (Rh is 20% by weight) according to the present invention. (Magnification: 1000 times) FIG. 28 is a secondary electron image (28A) and a backscattered electron image (28B) on the electrode surface of the Pt / Rh metal (Rh is 20% by weight) according to the present invention. (Magnification: 10,000 times) FIG. 29 is a secondary electron image (29A) and a reflected electron image (29B) on the electrode surface of the Pt / Rh-based metal (Rh is 20% by weight) according to the present invention. (Magnification: 30000 times) FIG. 30 shows a secondary electron image (30A) and a reflected electron image (30B) on the electrode surface of the Pt / Rh metal (Rh is 30% by weight) according to the present invention. (Magnification: 1000 times) FIG. 31 shows a secondary electron image (31A) and a reflected electron image (31B) on the electrode surface of the Pt / Rh metal (Rh is 30% by weight) according to the present invention. (Magnification: 10,000 times) FIG. 32 is a secondary electron image (32A) (32C) and a reflected electron image (32B) on the electrode surface of the Pt / Rh metal (Rh is 30% by weight) according to the present invention. (Magnification: 30000 times, 5000 times) FIG. 33 is a graph showing the results of XRD analysis of a Pt / Ph metal according to the present invention. FIG. 34 is a schematic configuration diagram of a pen jet type plasma processing apparatus having a tubular bar electrode according to the present invention. FIG. 35 is a schematic configuration diagram of a plasma generating unit in which the plasma generating electrode according to the present invention is a grinding arc type electrode. FIG. 36 is a schematic configuration diagram when the plasma generating electrode according to the present invention includes a sawtooth electrode. FIG. 37 is a schematic diagram of plasma generation in a conventional plasma generation electrode. FIG. 38 is an enlarged photograph of the electrode tip when arc plasma is generated using a conventional rod-shaped electrode made of W or Cu.

Explanation of symbols

2 Plasma processing apparatus 4 Plasma generator 4a Plasma generator 6 Power supply 7 Plasma generator 8 Rod electrode 10 Electrode tip 10a Electrode tip 10b Coating film 10c Electrode tip body 12 Electrode base 14 Sleeve 15 Water cooling part 15a Cooling Water 16 Nozzle-like electrode 16b Injection port 18 Water-cooled electrode cap 18a Cooling water 20 Ground 22 Object to be processed 24 Guide body 26 Insulating portion 28 Working gas 30 Gas inlet 31 Three-phase AC power supply 32 Pulse modulator 34 Power regulator 36 Power meter 38 High voltage transformer 40 Coil 41 Ground 42 Capacitor 44 Tubular electrode 46 Tubular electrode tip 46a Electrode tip surface 50 Gas inlet 56 Second gas inlet 60 Grinding arc type electrode 60a Electrode 60b Electrode 61 Current path 62a Current line 62b Current line 63a Discharge surface 63b Electrode surface 65 Weakly ionized plasma 70 Plasma generating electrode 72a Saw blade electrode 72b Saw blade electrode 74 Ground electrode 76a Power source 76b Power source 77a Projection 77b Projection 108 Rod electrode 108a Electrode tip surface 108b Electrode point 109 Abrasion material particle 116 Nozzle Electrode 116a Injection port 122 Object to be processed d Irradiation distance P Plasma T ₁ thickness T ₂ thickness

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of a plasma processing apparatus 2 having a penjet electrode according to the present invention (hereinafter also referred to as “penjet plasma processing apparatus”). The plasma processing apparatus 2 includes a plasma generation apparatus 7 including a plasma generator 4 and a power supply unit 6 and a processing unit (not shown) on which an object to be processed 22 is placed. The plasma generator 4 is provided with a pen jet electrode composed of a rod-like electrode 8 and a nozzle-like electrode 16. The guide body 24 constituting the plasma generator 4 is provided with the rod-shaped electrode 8, and the nozzle-like electrode 16 is disposed on the injection port 16 b side of the guide body 24.

The working gas 28 supplied from the gas introduction port 30 circulates in the guide main body 24, is supplied to the plasma generation unit 4a, and is converted into plasma. The gas supply pressure of the working gas 28 causes the nozzle electrode 16 to Plasma P is ejected as a flux from the ejection port 16b. FIG. 2 shows a photograph of the plasma P ejected from the ejection port 16b of the pen jet type plasma processing apparatus 2 according to the present invention. In the test described later, dry air is used as the working gas 28, the gas supply pressure is set to 0.2 MPa, and the gas flow rate is set to 20 L / min. When dry air is used as the working gas 28, the workpiece 22 is irradiated with a plasma flow composed of N ₂ ⁺ , O ₂ ^+, or the like.

  According to the pen jet type plasma processing apparatus of the present invention, the working gas 28 can be selected from dry air, humidified air, helium, argon, oxygen, nitrogen, hydrogen, hydrogen sulfide, hydrocarbon gas, and a mixed gas thereof. The desired plasma P can be generated by selecting as appropriate. Although not shown, a commercially available gas cylinder, compressor, blower, nitrogen gas supply device, or the like can be used to supply the working gas to the gas inlet 30. In addition, commercially available valves, mass flow controllers, rotameters, etc. can be used to control the flow rate of the working gas. A flow rate meter may be added, and a regulator (not shown) that controls the gas supply pressure is installed. Is done.

  As shown in FIG. 1, a water-cooled electrode cap 18 is provided on the outer periphery of the guide body 24, and the nozzle electrode 16 is connected to the ground 20 through the water-cooled electrode cap 18. By circulating the cooling water 18a, the nozzle electrode 16 and the plasma generating part 4a are cooled, and damage to the nozzle electrode 16 and plasma diffusion are prevented. Further, an insulating portion 26 is formed around the plasma generating portion 4a to prevent an electric field from being formed between the water-cooled electrode cap 18 connected to the earth 20 and the rod-shaped electrode 8.

  Further, the rod-shaped electrode 8 is composed of an electrode tip portion 10 made of a Pt / Rh metal and an electrode base end portion 12 made of a base metal having a high melting point such as tungsten or stainless steel, and the electrode tip portion 10 and the electrode The base end portion 12 is electrically connected to the base end portion 12 by a sleeve 14 made of Cu or Ni having good electrical conductivity. Therefore, when the wear of the electrode tip 10 increases due to long-term use, only the electrode tip 10 made of Pt / Rh metal can be replaced. In this embodiment, the electrode tip 10 uses an electrode material having a diameter of 1.6 mm and a length of 9 to 10 mm. The length and diameter of the electrode tip 10 can be changed as appropriate, but in the case of the pen jet electrode of FIG. 1, the diameter of the electrode tip 10 is 0 in order to concentrate the electric field on the electrode tip surface 10a. It is preferably set to about 5 mm to 3 mm.

  As described above, the working gas 18 flows between the side surface of the rod-shaped electrode 8 and the guide body 24 from the gas inlet 30 of the plasma generator 4 and is supplied to the plasma generating unit 4a. . The electrode front end surface 10a or the electrode front end surface 10a and its vicinity serve as a discharge surface, and the working gas 28 supplied to the plasma generator 4a is plasma by arc discharge between the electrode front end surface 10a and the nozzle-like electrode inner surface 16a. The surface of the workpiece 22 is irradiated with the plasma P from the injection port 16b. In the test described later, the inter-electrode gap from the electrode tip surface 10a of the rod-shaped electrode 8 to the closest position of the nozzle-shaped electrode is set to about 2 mm, and the irradiation distance d between the injection port 16a and the workpiece 22 is It is set to 10 mm.

  The potential applied to the rod-shaped electrode 8 is applied by a pulse current supplied from the power supply unit 6. In this embodiment, the power supply unit 6 includes a pulse modulator 32 connected to a three-phase AC power supply 31, an LC series circuit composed of a coil 40 and a capacitor 42, and a high voltage transformer 38 connected to the ground 41. . With the pulse modulator 32, the pulse frequency and the pulse width can be freely adjusted. Further, the voltage is boosted by the high voltage transformer 38 and a high voltage pulse is applied between the rod-shaped electrode 8 and the grounded nozzle-shaped electrode 16. Further, in the LC series circuit, the decrease in the charging voltage in the capacitor 42 is suppressed by the coil 40, and the potential applied to the electrode tip surface 10a by the discharge from the capacitor 42 is held at the dischargeable potential. In an electrode wear test using various electrode tip portions 10 to be described later, the pulse width of the applied high voltage pulse is set to about 2 μs and the pulse frequency is set to about 20 kHz.

  In the embodiment of FIG. 1, arc discharge is generated by a high voltage pulse between the nozzle-like electrode 16 connected to the ground 20 through the water-cooled electrode cap 18 and the electrode tip surface 10a, and thermionic emission, field emission, Alternatively, plasma P is generated by electrons emitted by Schottky. At this time, a voltage of 10 to 15 kV is applied to the inter-electrode gap by the high voltage pulse, and the voltage of the inter-electrode gap is reduced to about 5 kV by arc discharge. Further, the pulse modulator 32 is provided with a power regulator 34 and a wattmeter 36, so that the supplied power can be freely adjusted, and in order to maintain the arc discharge potential, in the test described later, 100W to It is set in the range of 500W.

In the pen jet type plasma processing apparatus according to the present invention, the diameter of the electrode tip portion 10 made of a Pt / Rh metal is about 1.6 mm (cross-sectional area of the electrode tip surface 10a: about 2 mm ² ), and the pulse frequency Is about 30 kHz, the pulse width is about 2 μs, and the flow rate of the supplied working gas is about 20 L / min. When the supplied power is set to the following value, a suitable plasma is continuously generated by arc discharge or It can be generated intermittently. In this case, it is preferable that the average power is set to 200 W (100 W / mm ² ) or less, the maximum applied voltage is set to about 5 kV, and the maximum peak current is set to 10 A (5 A / mm ² ) or less. In other words, the average current density of the supplied current is preferably set to a predetermined value or less, and if the cross-sectional area is increased, the supplied power can be increased and the plasma generation amount can be increased. That is, if the density of the average power is set to 100 W / mm ² or less, the plasma generation amount can be appropriately adjusted according to the cross-sectional area.

  FIG. 3 is a schematic cross-sectional view of a plasma generating apparatus 7 having a double-electrode water-cooled pen jet electrode according to the present invention, and a water-cooling portion 15 is provided on the outer periphery of the electrode base end portion 12. In addition, about a member same as FIG. 1, some code | symbols and the description are abbreviate | omitted. By circulating the cooling water 15a, the electrode tip portion 10 is cooled together with the electrode base end portion 12, and evaporation of the electrode material is suppressed, so that the amount of wear of the electrode can be reduced. Therefore, the plasma P can be generated over a long time. Furthermore, it is possible to prevent plasma from being generated from the outer periphery in the vicinity of the electrode front end surface and evaporation of the electrode material, and a suitable jet plasma P is generated. Further, the flow rate and / or temperature of the cooling water 15a, 18a is adjusted according to the injection amount of the plasma P, and the stable operation of the plasma generator 7 over a long time can be realized. Furthermore, if the water cooling part 15 is brought close to the electrode front end surface 10a, the periphery of the outer edge of the electrode front end surface 10a is also cooled, so that the diffusion of plasma is suppressed and the flux of the generated plasma P can be reduced. .

FIG. 4 is a schematic cross-sectional view of the electrode tip 10 according to the present invention. In FIG. 1, the entire electrode tip 10 is made of Pt / Rh metal, but as shown in (4A), the electrode tip body 10c is coated with Pt / Rh metal by plating, vapor deposition or the like. The electrode tip can be formed by forming the film 10b. The Pt—Rh alloy is generally more expensive than the Pt pure metal, and the production cost of the plasma generation electrode according to the present invention can be reduced by reducing the amount of the Pt—Rh alloy used. When the coating film 10b is made of a Pt—Rh alloy containing a relatively large amount of Rh, and the electrode tip body 10c is made of Pt metal, the Pt—Rh alloy is formed at the interface and in the vicinity of the interface due to diffusion of the metal element. It is formed. Coating film 10b of the _second thickness T ₂ that is coated on the electrode front end surface 10a of the electric field concentrates is preferably thicker coating than the thickness T ₁ of the coating film 10b of the side surface. Further, as shown in (4B), the coating film 10b may be formed only in a predetermined region including the discharge surface. The _second thickness _{T 2} is preferably 0.1mm or more, more preferably 0.5mm or more.

  FIG. 5 is an enlarged photograph of an electrode tip portion obtained by imaging the Pt / Rh metal electrode tip portion according to the present invention and each electrode tip portion made of a comparative Pt—Ir alloy after arc discharge. As the electrode material of the electrode tip 10 shown in FIG. 1, a Pt—Rh alloy according to the present invention and a Pt—Ir alloy as a comparative example are used. After plasma generation by arc discharge for 10 minutes, the electrode tip surface 10a is enlarged and imaged. The diameter of each electrode tip used is about 1.6 mm, and the electrode tip surface 10a has the same surface area. The Rh content of the Pt—Rh alloy used as the electrode material is 10% by weight, and the Ir content of the Pt—Ir alloy is 20% by weight. When a Pt—Rh alloy electrode tip is used, 500 W of power is supplied to the pulse modulator, and when a Pt—Ir alloy electrode tip is used, 400 W of power is supplied. . Further, dry air is used as the working gas.

  As shown in (5A), when an electrode tip made of a Pt—Rh alloy is used, the shape of the electrode tip has substantially the same shape as before discharge when the supplied power is 500 W. As shown in (5B), when an electrode tip made of a Pt—Ir alloy is used, a remarkable deformation is seen in the shape of the electrode tip at a supplied power of 400 W. It is considered that this is because the electrode tip is heated and melted by ion collision or the like, and the electrode wear is increased by metal evaporation, oxidation wear, spark wear and the like. As shown in (5A), the electrode tip portion made of the Pt—Rh alloy according to the present invention has almost no electrode wear, and the emission of wear material particles is extremely reduced. Plasma generation using the Pt—Rh alloy This shows that high-voltage arc plasma can be generated with high efficiency by applying a high voltage.

  FIG. 6 shows an enlarged photograph of the Pt metal electrode tip according to the present invention taken after plasma generation. FIG. 7 shows a comparative example of a Pt—Ir alloy (7A) and a Pt—W alloy (7B). The enlarged photograph figure after discharge of each electrode front-end | tip which consists of) is shown. The results shown in FIGS. 6 and 7 are obtained when arc discharge is performed for 10 minutes with a supplied power of 300 W. Each electrode tip has a diameter of about 1.6 mm and a length of 9 mm. As shown in (6A) and (6B), the Pt metal electrode according to the present invention has good oxidation resistance, and the surface of the electrode tip after plasma generation has the same shape as before discharge. ing. In addition, in the scanning electron microscope image (SEM image) shown in (6C), micropores are slightly formed, but the surface state before the discharge is substantially maintained.

  On the other hand, as shown in (7A), in the case of an electrode tip formed from a Pt—Ir alloy (Ir content: 20% by weight), it has good oxidation resistance common to noble metals, but compared to before discharge. The shape has changed. That is, compared with the case where Pt metal is used, the amount of wear of the Pt—Ir alloy is large, and as described above, the electrode wear increases rapidly as the supply power and the discharge time increase. Furthermore, as shown in (7B), in the case of the electrode tip made of Pt—W alloy, significant deformation was caused by discharging at 300 W for 10 minutes. This is considered to be caused by a significant increase in Joule heat generation on the discharge surface as the electrical resistance increases due to the formation of tungsten oxide. Further, it can be seen from the SEM image that the inclusion of W reduces the oxidation resistance of the electrode material, the discharge surface becomes brittle, and a large amount of wear material particles are released.

  Next, the result of quantitatively measuring the electrode wear with respect to the supplied power using the Pt metal electrode tip according to the present invention and each electrode tip shown in FIG. 5 is shown. FIG. 8 is a graph showing the power dependence of the electrode wear amount using the electrode tip of Pt metal and Pt—Rh alloy according to the present invention and the Pt—Ir alloy electrode tip of the comparative example. The horizontal axis indicates the supplied power (Electric power (W)), the vertical axis indicates the amount of wear (Erosion amount (mg)), the discharge duration time is set to 10 minutes, and the electrodes before and after plasma generation The amount of wear is estimated from the mass difference at the tip. In this experiment, the double-electrode water-cooled pen jet type plasma generator shown in FIG. 3 is used. As shown in FIG. 8, in the case of the electrode tip made of Pt—Rh alloy in the range of supplied power of 100 W to 300 W, there is little or very little electrode wear, and the electrode is also in the range of 300 W to 500 W. The increase in wear is suppressed and only a slight increase in wear is observed. Therefore, it is shown that by using a Pt—Rh alloy as an electrode material, high-energy and high-purity plasma can be stably generated with much less contamination of wear material particles.

  In the case of a Pt metal electrode tip, the wear power is hardly worn or the wear amount is suppressed to a very small amount up to 300 W. When the supplied power reaches 400 W, the amount of wear increases rapidly, and is not suitable as an electrode material when generating high-energy and high-purity arc plasma. However, FIG. 6 shows that Pt metal is an excellent electrode material when the supplied power is 400 W or less.

  On the other hand, in the case of the electrode tip portion made of Pt—Ir alloy, the wear amount has already been significantly increased at 300 W, and the wear amount has been rapidly increased when the supplied power is 400 W. Furthermore, when it exceeds 400 W, the function itself as an electrode tends to deteriorate, and measurement at 500 W is not performed. That is, at the tip of the electrode made of Pt—Ir alloy, when the power supplied reaches 300 W, a clear increase in the amount of wear is observed, and the electrode wear shows a rapid increase in the range exceeding 300 W. Pt—Ir alloy It is difficult to use as an electrode material. In other words, if the power supplied to the plasma is 300 W or less, a Pt—Ir electrode can also be used.

  FIG. 9 is an optical micrograph of the surface of the workpiece processed by the plasma processing apparatus according to the present invention. An Si substrate is used as an object to be processed, and a dark field image of the surface of the Si substrate after plasma processing is taken by an optical microscope. (9A) is a surface of an unprocessed substrate (Untreated substrate). Is shown. When using a plasma processing apparatus equipped with a Pt—Rh alloy plasma generation electrode, as shown in (9B) and (9C), almost no wear material particles adhere to the supplied power of 100 W and 200 W, It turns out that it is the same state as the untreated substrate surface of (9A). Further, when the supply power is increased from 200 W to 400 W, the wear material particles are only slightly adhered as shown in (9D) and (9E). Compared to the case of using the Pt metal plasma generation electrode according to the present invention shown in (9F) to (9H), it can be seen that there is very little attachment of wear material particles.

  When the tip of the Pt metal electrode is used in the plasma processing apparatus according to the present invention, as shown in (9F), almost no wear particles are attached with the supplied power of 200W, and the supplied power of 300W shown in (9G). Even in this case, only a small amount of wear material particles adheres to the entire surface of the Si substrate. Further, in the case of the supply power of 400 W shown in (9H), it can be seen that relatively large wear material particles made of Pt metal are released from the electrode and adhere to the entire surface of the Si substrate. FIG. 8 shows a good agreement with the results shown in FIG. 8, showing that the Pt metal electrode tip can be used as an extremely excellent plasma generation electrode, with the release of wear material particles being suppressed up to about 300 W of power supply. Yes.

  Next, as a comparative example to the data of Pt metal and Pt—Rh alloy (Rh content: 10 wt%) according to the present invention, W metal, Cu metal, Pt—Ir alloy (Ir content: 20 wt%), The result of adding the data of Pt-W alloy (W content: 8 weight%) and comparing the discharge time dependence of the amount of electrode wear is shown. FIG. 10 shows an accumulated wear amount (Accumulated erosion amount (mg)) with respect to an accumulated discharge time (Accumulated discharge time (min)) of an electrode tip made of Pt / Rh metal according to the present invention and various comparative examples. FIG. Using the electrode tip formed from the above electrode material in the dual electrode water-cooled pen jet type plasma generating apparatus shown in FIG. 3, the amount of electrode wear for each discharge time is measured, and these values are plotted. In this measurement, the supplied power is set to 300W. Moreover, the diameter of each electrode front-end | tip part is all about 1.6 mm, and has the same front-end | tip surface area.

  As shown in FIG. 10, at the electrode tip portion of the Pt—Rh alloy, the wear amount is suppressed to a very small amount even for a long-time discharge. The amount of wear at the tip of the electrode made of Pt—Ph alloy after about 60 minutes of discharge is about 0.6 mg, which is much different from other metals. In the tip part of the Pt metal electrode, an increase in the wear amount is suppressed as compared with the metal of the comparative example, and the wear amount is about 2.4 mg after 60 minutes of discharge.

  On the other hand, the amount of wear reaches about 2.9 mg at the tip of the electrode made of Pt—Ir alloy. Further, the wear amount of Cu metal has already reached about 2.4 mg after 30 minutes of discharge, and in the case of W metal and Pt—W alloy, about 50 mg of W metal and Pt—W alloy for 5 minutes of discharge. The amount of wear is about 7 mg. When Pt metal and its alloys, Pt-Rh alloy, Pt-Ir alloy, and Pt-W alloy are compared, the stability of the plasma generating electrode is remarkably improved by containing Rh, and Ir and W alloys When forming the electrode, it can be seen that the electrode performance is degraded.

  FIG. 11 is a graph showing the dependence of the accumulated wear amount (Accumulated wear amount (mg)) on the accumulated discharge time (min) in the plasma generation electrode using the Pt—Rh alloy according to the present invention as an electrode material. It is a figure and the amount of wear of an electrode is measured by changing the Rh content of the Pt—Rh alloy. In this experiment, the double-electrode water-cooled pen jet type plasma generator shown in FIG. 3 is used, and the amount of wear over a longer time is compared. The case where the mass ratio of Rh in the Pt—Rh alloy is 10% is indicated by a circle (◯), the case of 20% is indicated by a triangle (Δ), and the case of 30% is indicated by a square (□). The supplied power is 300 W, and the diameter of each electrode tip is set to about 1.6 mm, including the Pt electrode (♦) as a comparative example. As in FIG. 10, the amount of wear for each discharge time is measured, and the values obtained by integrating them are plotted.

  As shown in FIG. 11, as the Rh content of the Pt—Rh alloy increases, the wear amount of the electrode decreases, and when the Rh mass ratio is 30%, the wear amount is less than that of the Pt electrode. The amount is reduced to about ½. In other words, the lifetime of the plasma generating electrode is approximately doubled, and the generation of impurities is suppressed to about half, and a more suitable plasma generating electrode can be obtained by increasing the Rh content. Yes. The tip of the Pt metal electrode has a larger amount of accumulated wear than when the Pt—Rh alloy is used, but the amount of accumulated wear is slightly increased compared to the other metals shown in FIG. Needless to say.

  In the test on the mechanical strength of the electrode material, the mechanical strength of the plasma generating electrode is remarkably lowered when the mass ratio of Rh exceeds 40%. That is, by setting the mass ratio of Rh in the range of 1 to 40%, suitable hardness, tensile strength, toughness, and the like are imparted to the plasma generating electrode according to the present invention. Furthermore, in the above-described test regarding the mechanical strength, a more suitable mechanical strength is obtained when the mass ratio of Rh is set to 10 to 30%.

  In order to elucidate that Pt / Rh-based metals have excellent characteristics as electrode materials for plasma generation electrodes based on the more essential physical properties of the metals, the present inventors have developed the Pt / Rh-based metals according to the present invention. Various physical property values of the metal are measured, and suitable physical property values are specified from the correspondence with the electrode performance. Below, the measurement result of the various physical-property values regarding a Pt * Rh type metal is shown.

  The present inventors pay attention to the lattice constant as a factor that the Pt / Rh metal according to the present invention is suitable for the electrode material, and derive the lattice constant of the Pt / Rh metal from the X-ray diffraction (XRD) analysis. Yes. FIG. 12 is a graph showing the results of XRD analysis of a Pt / Ph metal according to the present invention. Each data in the figure shows the X-ray diffraction intensity (Intensity) with respect to the diffraction angle 2θ by irradiation of Ca Kα rays (λ = 1.54060Å), and each contains 10 wt% of Pt metal (Pt) and Rh. X-ray diffraction of a Pt—Rh alloy (Pt—Rh 10%), a Pt—Rh alloy containing 20% by weight of Rh (Pt—Rh 20%), and a Pt—Rh alloy containing 30% by weight of Rh (Pt—Rh 30%). An intensity graph is shown. In the experiment, the lattice constant a is obtained by calculating the interplanar distance d from the diffraction angle 2θ of XRD corresponding to the (111) plane of the Pt · Rh metal in the broken line in FIG. FIG. 13 is an enlarged graph showing the inside of the broken line in FIG. 12, and it can be seen that the lattice constant of the Pt / Rh-based metal according to the present invention clearly changes according to the content of Rh. Although not shown, XRM analysis using a bulk metal of Rh is also performed.

  Table 1 shows the weight percent of Rh (Weight Percent of Rh) and the lattice constant a (Lattice Constant) obtained from the XRD analysis as Examples 1-4. The Rh metal (Rh 100% by weight in the table) shown as a comparative example has poor workability and is difficult to use as an electrode material. That is, when the lattice constant a in Table 1 is 3.797 mm or more, the workability of the electrode material is lowered, which indicates that it is difficult to use as an electrode for plasma generation. The inventors of the present invention have determined that the lattice constant a of a metal preferable as an electrode material is 3.80 or more from the dependence of the Rh content on the workability of the electrode material.

  For example, the lattice constant of Cu metal is about 3.608 mm, and the lattice constant of W metal is about 3.158 mm. However, as shown in FIG. 10, Cu metal and W metal are used as plasma generation electrodes. When used, the amount of wear was large. Therefore, when the lattice constant of the electrode material is smaller than 3.80 mm, not only the workability is deteriorated but also the possibility of contributing to the generation of wear particles is high. Furthermore, generally, as the lattice constant of the metal increases, the impurities easily dissolve, so the lattice constant of the electrode material is the lattice constant of Pt metal (Rh0 wt% in Table 1) (about 3.92Å). Preferably it is smaller. That is, in the Pt / Rh metal according to the present invention, the lattice constant a is preferably set in the range of 3.80 to 3.92 and more preferably set in the range of 3.87 to 3.92. Furthermore, even when other metal elements are added to the Pt / Rh-based metal, it can be used as a suitable electrode material by setting the lattice constant a in the range of 3.80 to 3.92.

FIG. 14 is a graph showing a lattice constant with respect to the Rh content (% by weight) of the Pt / Rh metal according to the present invention. The lattice constant a obtained by the XRD analysis shown in FIG. 13 is plotted against the Rh content (Weight Percent of Rh), and the relationship between the lattice constant a and the Rh content is approximated as shown below. Derived. A linear function indicated by a solid line is a fitting function for plotted data, and is optimized by a least square method. Further, the upper limit value of the lattice constant obtained from the error range of the experimental value is indicated by a one-dot chain line linear function, and the lower limit value is indicated by a two-dot chain line linear function. That is, when the error range is included, the ah relational expression showing the relationship between the Rh content and the lattice constant a, where the Rh content is X wt%, is expressed as follows.
a = −0.00113X + 3.908 ± 0.02
As described above, a suitable electrode material can be obtained by setting the lattice constant a within a desired range. If the content of Rh is adjusted or selected using the a-X relational expression, the lattice constant of the Pt / Rh metal according to the present invention can be set within a desired range, so that an electrode material with good workability is obtained. be able to. Therefore, a highly durable plasma generating electrode can be easily manufactured using this electrode material.

  FIG. 15 is a state diagram of a Pt—Rh alloy which is an electrode material according to the present invention. The vertical axis represents temperature (° C.), the horizontal axis represents the content (% by weight) of Rh with respect to Pt, curve A represents a solid phase line, curve B represents a liquidus line, and curve C represents a solubility line. This state diagram is obtained by quoting data described in “THE PGM DATABASE” http://www.platinummetalsreview.com/jmpgm/index.jsp (Non-patent Document 2). In the state (1), Pt and Rh are in a homogeneous melt state, and between the curve A and the curve B, the liquid phase and the solid phase are mixed. The state (2) on the low temperature side shows a complete solid solution state, and the state (3) on the low temperature side from the curve C, which is the solid solubility limit, is a Pt phase in which Rh is solid solution and / or crystallized with Pt as a main component. And a Rh phase in which Pt is dissolved and / or crystallized mainly composed of Rh and Rh (Pt + Rh). Further, at both ends of the curve C, when the Rh content is low, the Pt phase (4) is obtained, and when the Rh content is high, the Rh phase (5) is obtained.

  As shown in FIG. 15, the liquidus and solidus are in the range of the bulk melting point of Pt metal (1773.5 ° C.) and the bulk melting point of Rh metal (1963 ° C.) over the entire content. It is not common that the melting point of the binary alloy is completely within the melting point range of the two metal crystals. In the binary alloy, when the compounding ratio is within a predetermined range, the melting point of the two metals It often falls below the melting point of the crystal. For example, Au-Ni alloy, Ti-Zr alloy, Cr-Mo alloy, Pb-Sn alloy, Ag-Sr alloy and the like can be mentioned. In the Pt—Rh alloy according to the present invention, when the Rh content is 5% by weight, the melting point is about 1820 ° C., 10% by weight is about 1850 ° C., 20% by weight is about 1900 ° C. to 1903 ° C., and 30% by weight is about At 1930 ° C. to 1933 ° C. and 40% by weight, the temperature becomes about 1953 ° C., and the melting point of the alloy rises as the Rh content increases without decreasing from the bulk melting point of the Pt metal, and approaches the melting point of the Rh metal.

In FIG. 16, the table | surface which described melting | fusing point of Pt * Rh type metal which concerns on this invention, another metal, and an alloy is shown. As described above, spark wear is one of the causes of the generation of wear material particles, and this spark wear is caused by an explosion phenomenon on the discharge surface during plasma generation. Since this spark wear tends to be caused when a high melting point electrode material (W, Mo, etc .: see FIG. 16) is used, the melting point is relatively low and the tip of the electrode is moderately softened during plasma generation. Is determined to be preferable. In the case of the Pt—Rh alloy according to the present invention, it has excellent oxidation resistance, and the Rh content can be selected to set the melting point within an appropriate range. When the electrode material is in the range of the melting point of Pt metal (1773.5 ° C.) to the melting point of Rh metal (1960-1966 ° C.), spark wear is suppressed, and considering the mechanical strength of the electrode material, It is more preferable that the temperature is set in the range of 1773 ° C. to 1953 ° C., and it is clear from experiments that the temperature can be optimum when the temperature is in the range of 1850 ° C. to 1933 ° C.
The melting point of the Pt—W alloy is 1870 ° C., which is within the range of the preferred melting point of 1768 ° C. to 1963 ° C. described above. However, as shown in FIG. 7, in the electrode for plasma generation using the electrode material of the Pt—W alloy, remarkable electrode deformation is observed due to wear and melting. This is considered to be due to the low oxidation resistance of the Pt—W alloy, which indicates that the Pt—W alloy is inappropriate for use as an electrode material for the plasma generating electrode.

In FIG. 15, the melting point of the Pt / Rh metal is described so as to be uniquely determined according to the weight ratio of Rh. However, in practice, the same melting point is not always measured with respect to the weight ratio of Rh, and has a certain distribution depending on the production conditions of the alloy, the amount of impurities, and the like. Based on the measured melting point of the Pt / Rh-based metal, the present inventors reflect the above-described melting point distribution and can easily derive the melting point T (° C.) from the Rh weight ratio (X wt%). Finding a linear function. FIG. 17 is a graph in which the melting point of the Pt / Rh metal according to the present invention is plotted against the weight ratio of Rh (X wt%). Furthermore, a linear function is fitted to the plotted data to derive the TX relational expression, and an upper limit value (one-dot chain line) and a lower limit value (double store chain line) taking into account the size of the distribution range are described. Yes. The TX relational expression approximately derived from these data is expressed as follows.
T = −1.4890X + 1836.3 ± 70
By using this first TX relational expression, the melting point T (° C.) of the Pt / Rh metal can be set within a predetermined temperature range by adjusting the weight ratio of Rh.

Further, as shown in FIG. 15, the Pt / Rh-based metal according to the present invention is not linear with respect to the weight ratio of the Rh weight ratio, and the weight ratio of the Rh is about 0 to 30% by weight. On the other hand, the melting point temperature rises with a relatively large slope. Accordingly, in FIG. 18, the second TX relational expression is approximately derived by fitting a linear function to data in which the weight ratio of Rh is 0 wt% to 30 wt%. As shown in the figure, when Rh is in the range of 0 wt% to 30 wt%, it shows a good agreement with the linear function, and if the upper limit value (one-dot chain line) and the lower limit value (two-dot chain line) are considered, The TX relational expression 2 is expressed by the following expression.
T = −5.255X + 1785.3 ± 15
Using this second TX relational expression, the weight ratio of Rh is adjusted in the range of 0 ≦ X ≦ 30, and the melting point T (° C.) is more reliably set within a predetermined temperature range. Can do.

FIG. 19 is a graph in which the density ρ of the Pt / Rh metal according to the present invention is plotted against the weight ratio (X wt%) of Rh. The density ρ of Pt · Rh-based metals with different Rh weight ratios was measured and plotted, and the tendency of the density ρ (g / cm ³ ) with respect to the X weight% was derived approximately using a linear function. ing. When the Pt / Rh metal according to the present invention is used for a plasma generating electrode, if the density ρ is greater than 21.45 g / cm ³ , it tends to be difficult to set the electrical characteristics of the electrode to a predetermined value. I know that. This is considered to be due to the fact that the impurity content tends to increase with increasing density. Further, if the density ρ is smaller than 12.41 g / cm ³ , the discharge surface tends to become porous during electrode formation and / or plasma generation, which may be one of the factors that increase the generation of wear particles. There is. Therefore, it is preferable to set the density ρ of the Pt · Rh-based metal in the range of 12.41 g / cm ^{3 to} 21.45 g / cm ³ , and can stably impart predetermined electrical characteristics to the plasma generating electrode. In addition, it is possible to reduce the contamination of impurities and wear particles in the plasma.

As described above, in FIG. 19, the ρ-X relational expression is derived from the fitting to the actual measurement value, and the upper limit value (one-dot chain line) and the lower limit value (two-dot chain line) in the figure estimated from the measurement error. Based on the following,
ρ = −0.08401X + 20.87 ± 0.6
According to this ρ-X relational expression, the density ρ can be set within a predetermined density range by adjusting the weight ratio of the Rh. That is, the density of the Pt / Rh metal according to the present invention can be easily set within the above-mentioned preferred density range (12.41 g / cm ^{3 to} 21.45 g / cm ³ ).

  FIG. 20 is a graph in which the Vickers hardness HV of the Pt / Rh metal according to the present invention is plotted against the weight ratio (X wt%) of Rh. It is a plot of measured Vickers hardness HV of Pt / Rh metals with different Rh weight ratios. The Vickers hardness HV increases almost linearly in the range of X wt% from 0 to 30 wt%, and the tendency of the Vickers hardness HV (Hv) to X wt% is approximately derived using a linear function. ing. When a Pt / Rh-based metal is used for the plasma generating electrode, if the Vickers hardness HV exceeds 130 Hv, the discharge surface becomes brittle, and it becomes difficult to process the plasma generating electrode into a predetermined shape. Incidence increases. Moreover, when Vickers hardness HV becomes smaller than 50 Hv, durability shows a clear fall. That is, based on the electrode performance of the plasma generating electrode, it is preferable that the Pt / Rh-based metal is set to have a Vickers hardness HV in the range of 50 Hv to 130 Hv as an electrode material.

As described above, in FIG. 20, the HV-X relational expression of the Vickers hardness HV (Hv) and the X weight% is derived, and the upper limit value (one-dot chain line) and the lower limit value (two-dot chain line) of the Vickers hardness HV. ) Based on the following formula:
HV = -2.76X + 51.85 ± 15
By this HV-X relational expression, the Vickers hardness HV can be set within a predetermined range, the workability suitable for the electrode material can be imparted, and the generation of wear particles during plasma generation can be suppressed. .

  FIGS. 21 to 32 are scanning electron microscope (SEM) images of Pt / Rh metals according to the present invention. In each drawing, a secondary electron image and a reflected electron image by SEM are shown. As shown in FIG. 6 and the like, in the secondary electron image of the tip part of the Pt metal electrode, irregularities on the electrode surface were observed, but in the reflected electron image, the metal crystals constituting the Pt / Rh metal surface were observed. Depending on the structure and constituent elements, the observation images are displayed as black and white and their shades. That is, the difference in the crystal plane direction and the weight ratio of Rh in the Pt—Rh alloy can be observed by the reflected electron image.

  21 to 23 are SEM images of the surface of the Pt electrode not containing Rh. The magnification of each SEM image is 1000 times in FIG. 21, 10,000 times in FIG. 22, and 30000 times in FIG. In FIG. 21, (21A) is a secondary electron image, and (21B) is a reflected electron image. In (21B), in the Pt electrode formed from a single element, a difference appears in the density of black and white for each crystal grain due to the difference in the direction of the crystal plane where the electron beam is reflected in the crystallite. It can be seen that (21B) containing only Pt metal has a crystal grain size of about 1 μm. FIG. 22 shows an SEM image with a magnification of 30,000, and FIG. 23 shows an SEM image with a magnification of 30,000.

  FIGS. 24 to 26 are secondary electron images and reflected electron images on the electrode surface of the Pt—Rh alloy containing 10% by weight of Rh. In FIG. 24, the magnification is 1000 times, in FIG. 25 is 10000 times, and in FIG. It has doubled. In the reflected electron images (25B) and (26B) having a large magnification, the crystal grain size can be clearly observed. 27 to 29 are secondary electron images and reflected electron images on the electrode surface of the Pt / Rh-based metal (Rh is 20% by weight) according to the present invention. In (28B) and (29B), the crystal grain size is Observed clearly. Furthermore, the crystal grain size is clearly larger than when Rh is 10% by weight.

  30 to 32 are secondary electron images and backscattered electron images of a Pt—Rh alloy containing 30% by weight of Rh. In the backscattered electron images (30B) to (32B), as the weight ratio of Rh increases, the crystal grain size further grows, and some have a crystal grain size of 1 μm to 10 μm or more. . Therefore, it can be seen that the Pt—Rh alloy according to the present invention has a crystal grain size in the range of 0.5 μm to 100 μm.

  FIG. 33 is a graph showing the results of XRD analysis of a Pt / Ph metal according to the present invention. Similarly to FIG. 12, each data of (33A) indicates an X-ray diffraction intensity (Intensity) with respect to a diffraction angle 2θ by irradiation of Cu Kα rays (λ = 1.54060 Å). In FIG. 12, the plane distance d is calculated from the diffraction angle 2θ of XRD corresponding to the (111) plane of the Pt metal, and the lattice constant a is obtained. In FIG. 33, the (200) plane of the Pt metal, (220 ) Plane and XRD corresponding to the (311) plane are measured to obtain the lattice constant a. (33B) plots the lattice constant a when Rh is 10% by weight, 20% by weight and 30% by weight and when Pt or Rh described above is 100%. These data all follow the aX relational expression (relationship between Rh content and lattice constant a) shown in FIG.

  FIG. 34 is a schematic configuration diagram of a pen jet type plasma processing apparatus having a tubular rod-shaped electrode (hereinafter referred to as “tubular electrode 44”) according to the present invention. Hereinafter, a part of reference numerals and explanations of the same members are omitted. In this pen jet type plasma processing apparatus, a gas introduction port 50 is provided in the tubular electrode 44, and the working gas 28 flows through the tubular electrode 44 from the gas introduction port 50 and is supplied to the plasma generating unit 4a. . A high voltage pulse is applied between the electrode tip surface 46a of the tubular electrode tip 46 and the nozzle electrode 16 to generate arc discharge and generate plasma. Furthermore, in this embodiment, the second gas introduction port 56 is provided, and various substances can be supplied as the working gas according to the same gas or purpose as the working gas 28. In the electrode for generating plasma according to the present invention, the electrode front end surface 46a of the tubular electrode 44 and / or the discharge surface in the vicinity thereof is formed of a Pt / Rh-based metal, and electrode wear and wear material particles are suppressed.

  FIG. 35 is a schematic configuration diagram of the plasma generating unit 4a when the plasma generating electrode according to the present invention is a grinding arc type electrode 60. FIG. In the grinding arc type electrode, divergently shaped electrodes 60a and 60b arranged in the flowing working gas 28 are connected to current lines 62a and 62b, and a high voltage pulse is applied between the electrodes. Plasma P is generated by causing arc discharge. A strong ionized plasma (positive column (also referred to as “column”) or streamer) forming a current path 61 for arc discharge and a weakly ionized plasma 65 (plasma plume) in which almost no current flows are generated. . By forming the discharge surfaces 63a and 63b of the electrodes 60a and 60b from a Pt / Rh-based metal, electrode wear of the grinding arc electrode 60 can be suppressed and generation of wear material particles can be reduced.

When the plasma processing apparatus according to the present invention includes the grinding arc type electrode 60, the cross-sectional diameters of the electrodes 60a and 60b made of Pt / Rh metal are about 1.6 mm (cross-sectional area: about 2 mm ² ), and the pulse When the frequency is about 30 kHz, the pulse width is about 3 μs, and the flow rate of the supplied working gas is about 40 L / min, when the supplied power is set to the following values, it is suitable for the atmosphere and various working gases. Arc discharge can be generated to generate plasma continuously or intermittently. In this case, it is preferable to set the average power to 300 W (150 W / mm ² ) or less, the maximum applied voltage to about 7 kV, and the maximum peak current to 3 A (1.5 A / mm ² ) or less. Here, the unit area is the unit cross-sectional area of the electrodes 60a and 60b. In the case of the grinding arc type electrode 60, since arc discharge occurs between the discharge surfaces 63a and 63b, the discharge area is large, the supply power can be set to a relatively large value, and a relatively large amount of operation is performed. A gas can be circulated and converted into plasma. Therefore, if the density of the average power is set to 150 W / mm ² or less, the plasma generation amount can be appropriately adjusted according to the cross-sectional area.

  FIG. 36 is a schematic configuration diagram in the case where the plasma generating electrode 70 according to the present invention includes saw-toothed electrodes 72a and 72b. The plasma generating electrode 70 includes saw-tooth electrodes 72a and 72b on both outer sides and a ground electrode 74, and power sources 76a and 76b are connected to these electrodes. Each of the sawtooth electrodes 72a and 72b is provided with a plurality of sharp projections 77a and 77b. By concentrating the electric field on the sharp projections 77a and 77b, arc discharge is easily generated, and the plasma P is generated. Generated. By forming the discharge surfaces of the sawtooth electrodes 72a and 72b from a Pt / Rh metal, electrode wear due to electric field concentration on the protrusions 77a and 77b can be suppressed, and generation of wear material particles can be reduced. it can.

  The present invention is not limited to the above-described embodiments and modifications, and includes various modifications and design changes within the technical scope without departing from the technical idea of the present invention. Needless to say.

  The plasma generating electrode according to the present invention has excellent oxidation resistance and a suitable melting point because at least the discharge surface is formed from a Pt / Rh-based metal, and therefore has a suitable melting point. Electrode wear and release of wear material particles can be suppressed to a very small amount. Therefore, it is possible to provide a plasma generation apparatus that generates high-purity plasma using the plasma generation electrode. Furthermore, it is possible to suppress the adhesion of impurities by the plasma generation apparatus and realize a uniform plasma treatment of the surface of the workpiece. For example, the arc plasma generated by the plasma generation apparatus according to the present invention is a plasma that can be generated under a pressure of about atmospheric pressure and is used for various processing and surface treatments. It is possible to easily generate plasma from gas). Surface processing (etching, surface coating, etc.) and surface modification (improvement of wettability) according to the raw material gas and power supply by plasma processing the surface of workpieces such as semiconductor products, metal products, glass products, and processing members , Improvement of adhesiveness, improvement of biocompatibility), washing, desmear treatment, and the like.

Claims (16)

A plasma generation electrode of a plasma generation apparatus that generates plasma of a supply gas by discharge, wherein at least a discharge surface of the plasma generation electrode is expressed by Pt 1 _−Y Rh _Y (0 <Y <1). It is formed from an electrode material of Rh metal, the lattice constant a of the Pt / Rh metal is in the range of 3.80 to 3.92 mm, and the crystal grain size of the Pt / Rh metal is 0.5 μm to 100 μm. An electrode for plasma generation characterized by being in a range . 2. The plasma generating electrode according to claim 1 , wherein the melting point of the Pt · Rh-based metal is in a range of 1773 ° C. to 1966 ° C. 3. The electrode for plasma generation according to claim 1 or 2 , wherein the crystal structure of the Pt / Rh metal is a face-centered cubic lattice (FCC) structure. The electrode for plasma generation according to any one of claims 1 to 3 , wherein the density ρ of the Pt · Rh-based metal is in a range of 12.41 g / cm ^{3 to} 21.45 g / cm ³ . The electrode for plasma generation according to any one of claims 1 to 4 , wherein the Pt · Rh metal has a Vickers hardness HV in a range of 50Hv to 130Hv. When the weight ratio of Rh in the Pt / Rh metal is X wt%, the a-X relational expression of the lattice constant a (Å) of the Pt / Rh metal and the X wt% is a = −0. 00113X + 3.908 ± 0.02
In the represented, plasma generation electrode according to claim 1 to 5, wherein the lattice constant a by adjusting the weight ratio of the Rh is set. When the weight ratio of Rh to the Pt / Rh metal is X wt%, the melting point T (° C.) of the Pt / Rh metal and the TX relation of the X wt% is T = −1.4890X + 1836 .3 ± 70
Or when the X weight% is in the range of 0 ≦ X ≦ 30, the TX relational expression is T = −5.255X + 1785.3 ± 15
In the represented, plasma generation electrode according to any one of claims 1 to 6, wherein the melting point T is set by adjusting the weight ratio of the Rh. When the weight ratio of Rh to the Pt · Rh metal is X wt%, the relational expression between the density ρ (g / cm ³ ) of the Pt · Rh metal and the X wt% is ρ = −0.08401X + 20 .87 ± 0.6
In the represented, plasma generation electrode according to any one of claims 1 to 7, wherein the density ρ is set by adjusting the weight ratio of the Rh. When the weight ratio of Rh to the Pt / Rh metal is X wt%, the relational expression between the Vickers hardness HV (Hv) of the Pt / Rh metal and the X wt% is HV = −2.76X + 51.85 ± 15
The electrode for plasma generation according to any one of claims 1 to 8 , wherein the Vickers hardness HV is set by adjusting a weight ratio of the Rh. The electrode for plasma generation according to any one of claims 1 to 9 , wherein a weight ratio of Rh to the Pt / Rh metal is set in a range of 0 wt% to 40 wt%. The electrode in which the discharge is generated is configured such that a high field electrode and a low field electrode are opposed to each other, the discharge surface is disposed on the facing surface of the high field electrode, and at least the discharge surface of the high field electrode is the electrode material The electrode for plasma generation according to any one of claims 1 to 10 , formed from: The plasma generating electrode according to claim 11 , wherein the high electric field electrode is a rod-shaped electrode, the low electric field electrode is a nozzle electrode having a plasma injection port, and the electrode constitutes a pen jet electrode. The electrode for plasma generation according to claim 12 , wherein at least a tip portion of the rod-shaped electrode is formed of the electrode material. 12. The plasma generating electrode according to claim 11 , wherein the high electric field electrode is a protruding electrode having one or more protrusions on the discharge surface side. The plasma generating apparatus and generating plasma using the plasma generation electrode according to any of claims 1-14. A plasma processing apparatus, wherein a surface of an object to be processed is subjected to plasma processing by the plasma generating apparatus according to claim 15 .