Cathode in vacuum arc discharge generator, and vacuum arc discharge generator

Abstract

[Problem] To provide a vacuum arc discharge generator capable of guiding the position where a cathode material evaporates within a wide range and consuming the entire surface of a cathode surface, and a cathode for use in said vacuum arc discharge generator. [Solution] A vacuum arc discharge generator provided to a vacuum arc vapor deposition apparatus for performing arc discharge between a cathode and an anode connected via a power source in a vacuum to generate plasma and evaporating a cathode material constituting the cathode to perform vapor deposition, the vacuum arc discharge generator being used for generating and maintaining vacuum arc discharge plasma, and comprising a cathode 11 mainly composed of graphite as an evaporation source and a trigger electrode disposed to induce arc discharge. The cathode is provided with a cathode-surface surface 11A, the cathode-surface surface is provided with one or more continuous long groove parts 5, and, by configuring the groove parts to be adjacent to each other at a prescribed pitch P, one or more continuous raised parts 6 are formed between the adjacent groove parts.

Description

Cathode in vacuum arc discharge generator and vacuum arc discharge generator

[0001] The present invention relates to a vacuum arc discharge generator, and more particularly to a vacuum arc discharge generator used in a vacuum arc deposition apparatus for vaporizing and depositing a cathode material, primarily carbon, especially graphite, by generating plasma through arc discharge between a cathode and an anode in a vacuum, and a cathode for the vacuum arc discharge generator.

[0002] Generally, a vacuum arc deposition apparatus is an apparatus that vaporizes a cathode material from a cathode spot on the surface of a cathode surface by arc discharge generated between a cathode and an anode, and forms a vacuum plasma using this cathode-evaporated material, thereby forming (depositing) a thin film on the surface of a solid material placed in the plasma. Films formed by this type of apparatus are known to improve the wear resistance and corrosion resistance of solid surfaces when plasma containing metal ions or nonmetal ions is used. In particular, carbon films formed by using carbon plasma by using a cathode made primarily of carbon, especially graphite, are known to be highly useful as diamond-like carbon films (DLC films) consisting of a mixed crystal of diamond and graphite structures. Among these, hydrogen-free DLC films formed by vacuum arc deposition are the hardest of all DLC films, and have a high sp ３ Because it contains many structural components, it is also called tetrahedral amorphous carbon (ta-C), and is highly useful as a protective film for aluminum cutting tools and precision molds. The cathode may be made of a graphite material containing a single or multiple mixtures of graphite, metals, B, Si, P, S, Cl, Br, their oxides, carbides, nitrides, fluorides, sulfides, compounds, resins, and amorphous carbon. The cathode may also be primarily made of amorphous carbon.

[0003] In the vacuum arc discharge generator in such a vacuum arc deposition device, an arc discharge is generated by separating the trigger electrode from the cathode (arc, ignition) while a current is flowing between the cathode and the trigger electrode, and then the arc discharge induces the generation of plasma. -4The cathode arc discharge at a pressure of 10 Pa to 10 Pa releases vacuum arc plasma constituent particles such as cathode material ions, electrons, and neutral particles (atoms and molecules) in the cathode material.

[0004] In vacuum arc discharge generators, arc discharge is initiated by a trigger electrode to generate an arc discharge that forms a cathode spot, which serves as an evaporation point. When plasma is generated, emission holes are formed on the cathode surface at the location where vacuum arc plasma particles are emitted. The vacuum arc plasma particles originate at the ignition position (the position where the trigger electrode contacts) where plasma generation is induced, evaporating the surrounding cathode material. Therefore, emission holes may be formed only in a specific area. In such cases, the consumption of the cathode surface becomes uneven, which can cause poor contact of the trigger electrode. This can result in material waste, such as requiring the cathode surface to be regenerated by polishing, for example.

[0005] Therefore, some of the inventors of the present application developed a technology relating to the structure of a cathode and a trigger electrode in order to disperse the emission points of the vacuum arc plasma constituent particles (see Patent Document 1). This technology involves providing a finely textured surface on the cathode and smoothing the surface of the trigger electrode, thereby enabling the tips of the convex portions on the cathode surface to come into contact with the surface of the trigger electrode, enabling arc ignition and evaporating the cathode material from the convex portions. By concentrating emission holes on the convex portions, the convex portions are consumed, and then another convex portion is formed in a different position on the surface of the cathode. Utilizing this, the next arc is ignited when the tip of the other convex portion comes into contact with the surface of the trigger electrode.

[0006] Japanese Patent Application Laid-Open No. 2005-267909

[0007] The technology disclosed in the above-mentioned Patent Document 1 is structured so that unevenness is formed in advance on the surface of the cathode face, and when the tip of a convex portion is consumed, the tip of another convex portion can come into contact with the trigger electrode.The intended configuration is that if the convex portions appear irregularly over the entire cathode face, the cathode will be consumed as a whole.

[0008] However, because the state of the protrusion that should appear after the cathode is consumed cannot be easily controlled and the location of the protrusion cannot be predicted, in order to contact the tip of the most prominent protrusion among the protrusions that appear, the trigger electrode must be configured to have a flat contact surface with an area equal to or greater than that of the cathode surface, and this contact surface of the trigger electrode must be configured to face the contact surface with the cathode. Therefore, a drive mechanism is required to bring the trigger electrode, which has a relatively large surface, into contact with the cathode surface and then separate it (ignite) from it. In particular, when a vacuum arc discharges, vacuum arc plasma constituent particles (e.g., cathode material ions, electrons, cathode material neutral particles, etc.) are released, as well as droplets (cathode material particles ranging in size from submicrons to hundreds of microns). These droplets adhere to the contact surface of the trigger electrode, causing poor arc discharge. Therefore, the movement range of the trigger electrode must be increased to allow the trigger electrode to move away from the cathode surface. Furthermore, the state of the emission holes formed at the portion where the vacuum arc plasma constituent particles are emitted varies with each generation of plasma. Therefore, the state of other convex portions that appear after a convex portion is consumed depends on the conditions at the time when the cathode material evaporates. As a result, the shape of the cathode surface after evaporation is unstable, and there are concerns about the stability of arc discharge generation.

[0009] The present invention has been made in view of the above points, and its object is to provide a vacuum arc discharge generator and a cathode therefor that can induce the position at which the cathode material evaporates over a wide range and consume the entire surface of the cathode.

[0010] Therefore, the present invention, which relates to a cathode in a vacuum arc discharge generator, is provided in a vacuum arc deposition apparatus for generating plasma by conducting an arc discharge between a cathode and an anode connected via a power source in a vacuum, and for vaporizing and vapor-depositing a cathode material that constitutes the cathode, and the cathode in the vacuum arc discharge generator comprises a cathode made mainly of graphite as an evaporation source, and a trigger electrode arranged for inducing arc discharge, and for generating and maintaining vacuum arc discharge plasma, characterized in that the cathode has at least one cathode surface that serves as an emission surface from which the cathode material is emitted, and the cathode surface is provided with one or more continuous elongated grooves, and the grooves are arranged adjacent to each other at a predetermined pitch, so that one or more continuous raised portions are formed between adjacent grooves.

[0011] According to the above configuration, the cathode surface is provided with a continuous raised portion formed by the grooves. By igniting an arc at the raised portion with a trigger electrode, an arc discharge is generated, generating plasma and evaporating the cathode material forming the raised portion. Since the raised portions are continuously formed, the cathode spot (i.e., the evaporation position on the cathode surface) moves while being guided by the raised portions. Therefore, the cathode material is guided to be consumed within a range that can be guided by the previously formed raised portions. By disposing the raised portions over the entire cathode surface, the entire cathode surface can be consumed. Here, "one or more continuous grooves" refers to a single continuous groove as well as grooves formed by dividing the grooves into multiple segments. "Long" refers to a groove whose length is greater than its width, and is intended to be long enough to allow the cathode spot to move.

[0012] In the invention having the above configuration, the groove portion may be configured to have at least two side surfaces, and one or both of the side surfaces may be formed at an angle that is not perpendicular to a virtual smooth plane of the smooth cathode surface when the state before the groove portion is provided is assumed.

[0013] According to the above configuration, the raised portion formed by the grooves has an inclined surface that is not perpendicular to the virtual smooth plane of the cathode (the smooth cathode surface when assuming a state before the grooves are provided) due to the side surfaces of the grooves. The formation of this inclined surface allows the raised portion to have an apex portion with an appropriate angle, resulting in a shape in which part of the cathode surface is partially protruded, thereby enabling cathode spots of the cathode material to be induced. Furthermore, because the inclined surface is not perpendicular to the virtual smooth plane, the cathode material located on this inclined surface can be exclusively emitted. That is, in a direction perpendicular to the virtual smooth plane, the direction of emission of the cathode material is nearly identical, making it difficult for the cathode material to be emitted. However, since the inclined surface is exposed in the emission direction, the cathode material is easily emitted. In this case, when plasma is generated (cathode material is emitted), it is induced at the apex of the raised portion. However, since the cathode spot is formed in a range corresponding to an appropriate area including the apex angle, the inclined surface is also included in the cathode spot, allowing the cathode material to be emitted.

[0014] In the invention having the above configuration, the groove portion may be configured to have at least two side surfaces, and the two side surfaces may form a substantially V-shaped cross section.

[0015] According to the above configuration, by forming the groove in a substantially V-shape in cross section, it is possible to form apex corners of an appropriate angle on both sides of the raised portion formed by the groove, and also to form inclined surfaces on both sides of the raised portion. Therefore, the base point from which the cathode material is released can be guided to the apex of the raised portion, and the release of the cathode material can be induced by the inclined surfaces. Note that when the groove has a substantially V-shape in cross section, it is not excluded that one of the side surfaces can be perpendicular to the imaginary smooth plane. In such a shape, the cathode material will be released primarily from the other side surface that is not perpendicular to the imaginary smooth plane.

[0016] In the invention having the above configuration, the grooves are preferably arranged so that the depth to the deepest position is in the range of 0.01 mm to 5 mm and the pitch of adjacent grooves is in the range of 0.01 mm to 5 mm. More preferably, the depth is 0.05 to 0.5 mm and the pitch is 0.05 mm to 3.0 mm, and even more preferably, the depth is 0.05 mm to 0.2 mm and the pitch is 0.5 mm to 3.0 mm.

[0017] With this configuration, it becomes easy to move the cathode spots so that they are guided by the raised portions. That is, when the depth to the deepest position of the grooves is less than 0.01 mm, the difference between the grooves and the raised portions is small, making it difficult to guide the raised portions as cathode spots. When the depth exceeds 5 mm, the continuity between adjacent raised portions and grooves is eliminated (they are divided by the grooves), making it difficult to emit cathode material from an integrated cathode surface as a whole. On the other hand, when the pitch is less than 0.01 mm, the raised portions are too close together, resulting in an overall smooth cathode surface. When the pitch exceeds 5 mm, the spacing between adjacent raised portions becomes large, making it difficult to guide the cathode spots by the raised portions. Note that, experimentally, the most stable condition was observed when the depth to the deepest position of the grooves was 0.1 mm and the pitch was 1.0 mm. Therefore, the emission and movement of the cathode material can be stabilized by setting the pitch within a range of 0.5 to 2 times these dimensions. Furthermore, since the size of the range where cathode spots can occur is assumed to be approximately 3.0 mm, it is assumed that setting the upper limit of the pitch to 3.0 mm will enable the induction of cathode spots. If it becomes difficult to induce cathode spots, the vacuum arc discharge will not continue and will be extinguished. If the arc is extinguished, it will re-ignite, but if it is extinguished frequently, it will not be possible to form a film as desired. For example, if arcing and extinguishing are repeated in a short period of time, it will become difficult to continue the film formation process itself, and the manufacturing process will have to be terminated without obtaining a film with the desired thickness.

[0018] In the invention having each of the above configurations, the cathode surface of the cathode may be configured to be circular, the groove portion may be formed in the shape of a single continuous spiral extending from the center of the cathode surface, and the raised portion may be raised in a region adjacent to the spiral groove portion.

[0019] In the above configuration, the cathode spot moves while being guided by the spiral-shaped protrusion formed on the cathode surface, and the movement can be made to rotate continuously. That is, even when a long period of cathode material emission is required, continuous rotation over several revolutions is possible, so that a stable cathode material emission state can be maintained. Note that the spiral shape means a (planar) spiral shape with a constant depth direction, i.e., a so-called spiral shape.

[0020] In the inventions having the above configurations, the cathode surface of the cathode may be circular, the groove portions may be formed in a plurality of concentric circles centered on a central point of the cathode surface, and the raised portions may be raised in regions adjacent to the concentric groove portions.

[0021] The above-described configuration is configured with a plurality of concentric grooves instead of a long spiral groove. In the case of such a configuration, the cathode point moves in the circumferential direction while being guided by the raised portion (circular raised portion) that is a circular raised portion on the cathode surface, and further, after making a turn, the cathode point can continue to move in the circumferential direction while moving to another nearby circular raised portion.

[0022] Furthermore, in the inventions having the above configurations, the cathode surface of the cathode may be circular, the grooves may be formed by a plurality of similar polygons, and the similar polygons may be formed so that the ratio of similarity increases successively from the center to the periphery of the cathode surface while maintaining a constant pitch between adjacent polygons, and the raised portions may be raised in regions where the similar polygonal grooves are adjacent. In this case, the groove may be formed by a single, approximately spiral groove, and may have a continuous shape that forms a substantially similar polygon based on the similar polygon.

[0023] In the above configuration, instead of a plurality of concentric grooves, each groove is polygonal. However, even in this configuration, the cathode spot can be guided and rotated by the polygonal protrusion, just as in the case of a circular protrusion formed by concentric grooves. Furthermore, if the groove is formed as a single, continuous, approximately spiral shape based on a similar polygon, the cathode spot can be rotated in the same way as a spiral. Note that the term "approximately spiral" refers to a shape that approximates a smooth spiral and has multiple apex angles due to the basic polygon. The terms "approximately polygonal" and "approximately similar" refer to a state in which the polygon is distorted to form the above-mentioned approximately spiral shape, resulting in a shape that approximates a similar shape.

[0024] In the inventions having the above configurations, if the cathode surface of the cathode is polygonal, the grooves may be formed by a plurality of polygons similar to the polygons of the cathode surface, the similar polygons may be formed such that the ratio of similarity increases successively from the center to the periphery of the cathode surface while maintaining a constant pitch between adjacent polygons, and the raised portions may be raised in regions where the similar polygonal grooves are adjacent. In this case, the groove may be formed by a single, approximately spiral groove, and may have a continuous shape that forms a substantially similar polygon based on the similar polygon.

[0025] The above configuration is a configuration in which the cathode surface of the cathode is polygonal rather than circular, and the shape of the groove is polygonal to match the shape (polygon) of the cathode surface. Basically, it is the same as when the cathode surface is circular and the groove is polygonal.

[0026] In the inventions having each of the above configurations, the cathode surface of the cathode may be configured to be polygonal, the groove portions may be formed in a continuous spiral shape from any plurality of positions on the cathode surface, and the raised portions may be raised in regions where the spiral groove portions formed in each of the groove portions are adjacent to each other.

[0027] According to this configuration, for example, when the cathode surface of the cathode is rectangular having long and short sides, two regions are formed on the boundary line of the long side, and different continuous raised portions can be formed in each of the two regions by spiral grooves. In this case, the spiral shape may be the aforementioned approximately spiral shape, or a configuration in which concentric circles or similar polygons are used instead of a spiral may be used. When the cathode surface of the cathode is polygonal other than rectangular and can be divided into multiple regions, a spiral or approximately spiral groove may be provided in each of the multiple divided regions.

[0028] On the other hand, the present invention relating to a vacuum arc discharge generator is a vacuum arc discharge generator that uses any of the cathodes having the above-mentioned configurations, and is characterized in that the cathode is arranged so that a trigger electrode can contact the cathode surface.

[0029] In the vacuum arc discharge generator having the above configuration, when an arc is ignited by contact with the trigger electrode, an arc discharge is induced on the surface of the cathode surface, and plasma is generated, causing cathode material to be emitted from the surface of the cathode surface shaped as described above, thereby exerting the properties of the cathode, and as a result, it becomes possible to generate a vacuum arc discharge while consuming the entire cathode surface.

[0030] The present invention relating to the vacuum arc discharge generator having the above-described configuration may further comprise a magnetic field generating means, which may be disposed on the opposite side of the discharge surface of the cathode at an appropriate distance from the cathode.

[0031] In the above configuration, by disposing a magnetic field generating means on the opposite side of the cathode discharge surface (behind the cathode), it is possible to induce the movement direction of the cathode spot on the cathode surface. That is, as cathode material is emitted from the cathode spot, a current flows between the cathode and the anode, and a magnetic field is also generated around the current. Therefore, by applying a magnetic field from the outside to the magnetic field around the current so as to exert a magnetic Lorentz force, the position of the current flow (the position where the cathode material is emitted) can be changed. As a result of this magnetic force, the cathode spot can be induced in a predetermined rotational direction relative to the center of the cathode. Inducing the rotational direction in this way makes it easy to rotate the cathode spot, which is induced to move by the protrusion.

[0032] According to the present invention, the cathode spot can be moved by being guided by the long protrusions formed on the cathode surface, and as a result, the position where the cathode material is evaporated and emitted varies, and a wide range of the cathode surface is consumed. The expected variation in the emission position of the cathode material is induced by protrusions of various shapes formed by spiral, concentric, or linear grooves similar thereto formed on the entire surface of the cathode surface, and by sequentially moving the protrusions, the cathode material can be emitted from the entire surface of the cathode surface.

[0033] 1 is an explanatory diagram showing an overall outline of a vacuum arc evaporation apparatus; (a) is an explanatory diagram showing the entire cathode used in the first embodiment, and (b) is a partial cross-sectional view of the cathode used in the first embodiment; (b) is an explanatory diagram showing an example of a modification of the groove shape of the cathode used in the first embodiment; (c) is an explanatory diagram showing another modification of the cathode in the first embodiment; (d) is an explanatory diagram showing a cathode used in the second embodiment; (e) is an explanatory diagram showing a cathode used in the second embodiment; (f) is an explanatory diagram showing a vacuum arc discharge generator used in an experiment; (a) is an explanatory diagram showing the contact point of a trigger electrode, (b) is an explanatory diagram showing the experimental results of a target sample, and (c) is an explanatory diagram showing the experimental results of a comparative example; (f) is an explanatory diagram showing other modified examples; (g) is an explanatory diagram showing modified examples due to a change in the shape of the cathode.

[0034] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. First, the overall structure of a vacuum arc deposition apparatus will be briefly described, and then the details will be described.

[0035] FIG. 1 is a schematic diagram of a vacuum arc evaporation apparatus (also referred to as a film-forming apparatus). The vacuum arc evaporation apparatus according to the present invention includes a vacuum arc discharge generator 1, a plasma duct 2 serving as a transport path for particles of evaporated cathode material produced by the vacuum arc discharge generator 1, and a film-forming chamber 3 for film formation. Vacuum arc discharge induced by the vacuum arc discharge generator 1 evaporates cathode material from cathode points present on the surface of the cathode, and this cathode evaporated material forms a vacuum plasma, thereby forming (depositing) a thin film on the surface of a solid material placed in the plasma. The vacuum arc discharge generator 1 includes a cathode 11 and an anode 12 located nearby, each connected to an external arc power supply 13 via an insulated lead-in terminal 4 to enable arc discharge.

[0036] The cathode 11 is made of a film-forming material and corresponds to the target (evaporation material raw material). Various conductive solid materials can be used as the material for the cathode 11, but here, a material primarily made of graphite is used. The anode 12 is not limited to any particular material as long as it is conductive and can withstand temperatures of approximately 200°C. Simple metals, alloys, inorganic simple materials, inorganic compounds, etc. can be used. These can be used alone or as a mixture of two or more types. For example, stainless steel, mild steel, steel, copper, copper alloys, aluminum, aluminum alloys, graphite, etc. can be used. The vacuum vessel (chamber) itself can also be the anode.

[0037] A trigger electrode 14 is provided near the cathode 11, and is used to induce a vacuum arc between the cathode 11 and the anode 12. That is, the trigger electrode 14 is temporarily brought into contact with the surface of the cathode 11 and then pulled away (arc generation, ignition), thereby generating an electric spark between the cathode 11 and the trigger electrode 14. When an electric spark is generated, the electrical resistance between the cathode 11 and the anode 12 decreases, allowing a vacuum arc to be generated (transferred) between the electrodes 11 and 12.

[0038] Furthermore, a magnetic field generating means (permanent magnet or electromagnet) 15 is installed around the cathode 11 (on the opposite side of the discharge surface in the figure) with an appropriate gap therebetween. This magnetic field generating means 15 is intended to stabilize the cathode spot of the vacuum arc and the plasma generated by the arc discharge. Although the magnetic field generating means 15 is installed outside the chamber in the figure, it may also be installed inside the chamber. Furthermore, multiple magnetic field generating means 15 may be installed at appropriate positions. In other words, it is sufficient if a magnetic field that stabilizes the cathode spot and arc discharge is applied near the cathode surface. Note that a magnetic field generating device need not be installed, and the system may consist of only permanent magnets.

[0039] The film formation chamber 3 is open on the side facing the plasma generation means 1, and is equipped therein with a workpiece holding means 32 for holding workpieces A, B, ..., H. Charged particles (cathode material) emitted from the cathode are supplied to the workpiece A inside the film formation chamber 3 through the opening, and a film is formed on the workpiece. The workpiece holding means 31 rotates intermittently, so that a plurality of workpieces A to H can be sequentially placed facing the plasma generation means 1 and subjected to film formation.

[0040] In the vacuum arc discharge that forms the plasma flow, droplets are also emitted from the cathode point in addition to electrons and evaporated particles of the cathode material. Various mechanisms have been proposed to prevent these droplets from adhering to the workpieces A to H, and these mechanisms are appropriately selected and applied in the illustrated configuration.

[0041] A typical trigger electrode 14 is positioned so that it contacts the surface of the cathode 11 at a substantially constant position and ignites the arc. This ignition generates an electric spark, inducing a vacuum arc discharge. However, the position where the cathode material evaporates to form vacuum plasma (cathode spot) is the starting point, and the position is concentrated in the vicinity of the ignition point. Therefore, the area where the cathode material evaporates (is consumed) is extremely limited, resulting in uneven consumption. Therefore, the present invention is configured to evaporate the cathode material over a wide area of ​​the surface of the cathode 11.

[0042] <First embodiment relating to cathode> As described above, the vacuum arc discharge generator is configured to include the cathode 11 whose main material is graphite, which is an evaporation source, and the trigger electrode 14 arranged to induce arc discharge, and a long protrusion is formed on one of the surfaces of the cathode 11 on the discharge side (discharge surface, hereinafter sometimes referred to as the cathode surface).

[0043] A first embodiment of the invention relating to a cathode having such a configuration is shown in FIG. 2. Note that FIG. 2( a) shows the entire cathode 11, and FIG. 2( b) shows a partial cross section of the cathode 11. As shown in FIG. 2( a), the cathode of this embodiment is configured such that a cathode surface 11A is provided with a groove 5 that has a single continuous spiral (i.e., spiral) shape in a plan view. In particular, when the cathode 11 is configured in a cylindrical shape as shown in the figure, the cathode surface 11A has a circular shape. Therefore, by providing a spiral groove 5 extending from the center of the circular surface 11A to the outer periphery, the groove 5 can be formed over almost the entire cathode surface 11A. By providing such a groove 5, a single elongated protrusion 6 is formed that is continuous between adjacent grooves. Note that the shaded (grayscale) portion in FIG. 2( a) indicates the protrusion 6.

[0044] Here, as shown in FIG. 2(b), the grooves 5 provided on the cathode surface 11A are provided so that the interval between adjacent grooves 5, 5 is a predetermined pitch P, and the portion remaining between the adjacent grooves 5, 5 forms a raised portion 6. Here, the cross section of the groove 5 to be formed has two side surfaces 5a, 5b, and one of the side surfaces 5a, 5b (5a in the figure) is inclined. Here, inclination means a state in which the groove 5 is formed at an angle θa that is not perpendicular to an imaginary smooth plane X of the smooth cathode surface when the state before the grooves 11 are provided is assumed.

[0045] In the present invention, at least one side surface is inclined (configured so as not to be perpendicular to the imaginary smooth plane X), and therefore the other side surface may be inclined or perpendicular to the imaginary smooth plane X. Therefore, the groove portion 5 in this embodiment is exemplified as having one side surface 5a inclined and the other side surface perpendicular to the imaginary smooth plane X at an angle θb. In addition, a bottom surface 5c that is parallel to the imaginary smooth plane X is provided midway between both side surfaces 5a, 5b. In this embodiment, only one side surface 5a is inclined (not perpendicular to the imaginary smooth plane X).

[0046] On the other hand, the raised portion 6 is formed as a result of the groove portion 5 being provided, and does not protrude from the imaginary smooth plane X. In other words, it is in a protruding state relative to the groove portion 5. Therefore, the side surfaces 5a and 5b constituting the groove portion 5 also function as the side surfaces of the raised portion 6. Therefore, the upper ends (front end portions) 50 of the side surfaces 5a and 5b become the apex of the raised portion 5, and form a predetermined angle with one of the inclined side surfaces 5a (which is not perpendicular to the imaginary smooth plane X).

[0047] In the raised portion 6 configured as described above, a remaining portion 60 (the same plane as the imaginary smooth plane X) of a part of the (initial) cathode surface before the grooves 11 are provided may be formed in the width direction W of the elongated raised portion 6, depending on the size of the interval (pitch) P between adjacent grooves 5, 5 when the grooves 5 are formed. Since this remaining portion 60 is part of the initial cathode surface, it is a smooth plane, but it is sufficient if a vertex 50 having a predetermined angle (an angle that is not a right angle) is formed between this remaining portion 60 and the one side surface 5 a.

[0048] An important point of this embodiment is that by forming one of the side surfaces 5a inclined (not perpendicular to the imaginary smooth plane X), this side surface 5a forms a vertex 50 at a part of the raised portion 6, and the side surface 5a continuing from this vertex 50 is not perpendicular to the imaginary smooth plane X. With this configuration, the raised portion 5, which is relatively raised relative to the groove portion 5, is consequently in a protruding state on the surface 11A of the cathode 11, which facilitates contact of the trigger electrode 14 (see FIG. 1 ) with the raised portion 6 and serves as a cathode point (evaporation position) for facilitating the release of the cathode material. Furthermore, the presence of the side surface 5a that is not perpendicular to the imaginary smooth plane X causes the side surface 5a to be oriented in an angular direction relative to the release direction of the cathode material, thereby enabling the side surface 5a to serve as a region from which the cathode material is released. In contrast, if the other side surface 5b were perpendicular to the imaginary smooth plane X, the side surface 5b would be parallel to the release direction of the cathode material, making it difficult to release the cathode material from the side surface 5b. Furthermore, since the raised portions 6 having such a configuration are continuously configured as shown in FIG. 2( a), the cathode spots are guided in the longitudinal direction of the raised portions 6 and gradually change their positions. As a result, the cathode spots move, and the cathode material at the cathode spots is gradually evaporated (consumed), so that the entire cathode surface 11A can be used as cathode spots.

[0049] In order to exhibit the functions as described above, the shape of the groove portion 5 can be changed, for example, as shown in FIG. 3. The shape shown in FIG. 3(a) is such that by narrowing the pitch P in the above-described first embodiment (see FIG. 2(b)), the remaining portion 60 of the original cathode surface is not formed, and the cross-sectional shape of the groove portion 5 is made substantially V-shaped without providing the bottom surface 5c. Here, one side surface 5a is inclined (not perpendicular to the virtual smooth plane X), and the other side surface 5b is perpendicular to the virtual smooth plane X as an example.

[0050] Also in the above configuration, the upper end portion (the apex of the raised portion 6) 50 of one side surface 5a of the groove portion 5 protrudes relatively to the groove portion 5, so that it functions as a contact point of the trigger electrode 14 (see FIG. 1), and it becomes easier to release the cathode material. In particular, since there is no remaining portion 60 (FIG. 2(b)) near the apex 50 of the raised portion 6, the apex 50 of the raised portion 6 is in the most protruding state, so that the induction of the cathode point can be facilitated.

[0051] Similarly, the shape shown in FIG. 3(b) is a further modification of the shape shown in FIG. 3(a), and both side surfaces 5a and 5b of the groove portion 5 are inclined (not perpendicular to the virtual smooth plane X). In the case of such a configuration, since neither of the side surfaces 5a and 5b of the groove portion 5 is a plane perpendicular to the virtual smooth plane X, the release of the cathode material can be promoted from the side surfaces 5a and 5b on both sides of the apex 50 of the raised portion 6.

[0052] Regardless of the shape of the grooves 5 (FIGS. 2(b), 3(a), and 3(b)), the depth D to the deepest position is set in the range of 0.01 mm to 5 mm, and the pitch P between adjacent grooves 5 is set in the range of 0.01 mm to 5 mm. Preferably, the depth D is set to 0.05 to 0.5 mm and the pitch P is set to 0.05 mm to 3.0 mm, and more preferably, the depth D is set to 0.05 mm to 0.2 mm and the pitch P is set to 0.5 mm to 3.0 mm. When the pitch P is 0.5 mm or less, if the depth D is set to 0.1 mm or greater, the strength of the protrusions 6 is not maintained and they cannot be machined. Therefore, when the depth D is 0.1 mm or greater, a pitch P of 1.0 mm or greater may be required.

[0053] As described above, it has been experimentally clarified that adjusting the dimensions of the depth D and the pitch P affects the induction of cathode spots by the protrusions 6. The experimental results will be described later, but the effects of the dimensions of the depth D and the pitch P on the movement of the cathode spots can be summarized as follows.

[0054] That is, when the depth D of the grooves 5 is less than 0.01 mm, the difference between the grooves 5 and the protuberances 6 is so small that the difference between them is not clear, making it difficult to induce cathode spots using the protuberances 6. Furthermore, when the depth D exceeds 5 mm, adjacent protuberances 6 are divided (separated) by the grooves 5, resulting in a structure that resembles an aggregate of individual cylindrical materials consisting only of the protuberances 6, which may make it difficult to emit cathode material using the cathode surface 11A (emission of composite cathode material from multiple protuberances 6). On the other hand, when the pitch P is less than 0.01 mm, the protuberances 6 are too close together, approximating a smooth surface overall, making it difficult to induce cathode spots using the protuberances 6. Furthermore, when the pitch P exceeds 5 mm, the distance between adjacent protuberances 6 becomes so large that multiple protuberances 6 cannot be used simultaneously, making it difficult to induce cathode spots.

[0055] In the first embodiment described above, the cathode 11 is cylindrical and the cathode surface 11A is circular, so the grooves 5 are continuously configured to have a spiral (vortex) shape in a plan view. A similar shape may be provided by providing a plurality of concentric grooves 5.

[0056] FIG. 4 shows a plan view of the cathode surface 11A. FIG. 4(a) shows the first embodiment described above in plan view, and FIG. 4(b) shows a modified example thereof. As shown in FIG. 4(a), the spiral shape (spiral shape) in plan view is formed by grooves 5 with the same pitch P and gradually increasing in diameter from the center of the circular surface toward the outer periphery. In contrast, FIG. 4(b) shows a configuration in which multiple concentric grooves 51, 52, ..., 59 are provided. In this case, the individual diameters of adjacent concentric grooves 51 to 59 are adjusted so that the pitch P between them is the same.

[0057] By providing multiple concentric grooves 51-59 as in this modified example, raised portions 61, 62, ..., 69 are formed between adjacent grooves 51-59 at the same pitch P as the grooves 51-59, resulting in a state similar to that of the first embodiment. Even when multiple raised portions 61-69 are formed using such multiple grooves 51-59, the individual grooves 51-59 are continuous and each is appropriately long. Furthermore, the raised portions 61-69 are also continuous.

[0058] Even in this configuration, when vacuum arc discharge occurs in the raised portions 61 to 69, the movement of the cathode spot can be induced along an arc. Furthermore, movement of at least one revolution is possible, and if two or more adjacent raised portions 61 to 69 simultaneously become cathode spots, the movement is not induced along a single arc, and instead moves to another nearby raised portion 61 to 69, making movement of a second revolution possible.

[0059] Another modified example is shown in FIG. 5 . The modified example shown in this figure assumes that the cathode has a rectangular prism shape. In such a case, the cathode surface is rectangular, and linear grooves 5 are combined to form the entire cathode 11 in accordance with the shape. Note that the cathode 11 may have another polygonal prism shape (a polygonal cathode surface), but a rectangular prism shape (a square cathode surface) is shown here as an example. Note that FIG. 5( a) shows a roughly spiral (approximately spiral) shape in plan view, while FIG. 5( b) shows a collection of multiple similar shapes. Both show the cathode surface 11A of the cathode 11 in plan view.

[0060] In the modified example shown in FIG. 5( a), linear grooves 5 are successively connected to form a series of generally spiral (swirl) grooves 5, gradually increasing in length from the center of the cathode surface 11A. The pitch P between adjacent grooves 5 is adjusted to the same predetermined pitch P, as in the first embodiment. The cross-sectional shape of the grooves 5 in this case is also formed by selecting one of the various shapes described above. The remaining portion of the continuous grooves 5 forms a single, long, continuous protrusion 6, which can induce cathode spots, as in the first embodiment. The term "generally spiral" used here refers to a state similar to a spiral formed by combining multiple straight lines.

[0061] In the modified example shown in FIG. 5( b), the cathode surface 11A has a rectangular shape, and multiple similar rectangular grooves 51, 52, ..., 59 are arranged in a superimposed manner based on this rectangular shape. The similar polygons constituting the multiple grooves 51 to 59 have a similarity ratio that gradually increases from the center toward the periphery of the cathode surface 11A, and the similarity ratio is adjusted so that the pitch P between adjacent grooves 51 to 59 is constant. This type of configuration can be conceptualized as a modification of the aforementioned concentric circular grooves (see FIG. 4( b)) into a rectangular shape. The cross-sectional shapes of the grooves 51 to 59 in this case are also selected from the various shapes described above. The provision of the grooves 51 to 59 results in the formation of raised portions 51 to 59, which, like the aforementioned modified example configured with concentric circles, can enable cathode spot induction.

[0062] Although not specifically shown, a configuration may be adopted in which a circular spiral groove 5 or concentric grooves 51 to 59 (see FIG. 4 for both) are provided on a polygonal (quadrilateral) cathode surface 11A. Even when circular spiral grooves 5, 51 to 59 or concentric grooves are formed on a polygon, the resulting raised portions 6, 61 to 69 are formed over a wide area, making it possible to induce cathode spots in those areas. In this case, there are areas near the apex angles of the polygon where no grooves or raised portions are formed. However, since those areas are near the peripheral edges, not inducing cathode spots in those areas can stabilize the discharge state, and so a configuration is adopted in which no grooves are formed.

[0063] <Second Embodiment of Cathode> In the second embodiment of the cathode, grooves 5 are provided on a single cathode surface 11A to define multiple regions (induction regions) where cathode spots should be induced, and a raised portion 6 is formed by continuous grooves 5 in each induction region. This configuration is suitable for cases where the cathode surface 11A is a rectangle having long and short sides, or where the area of ​​the cathode surface 11A is large. When the cathode surface 11A is a rectangle that is elongated on one side (rectangle), the movement distance of the cathode spot in the long side direction becomes long. Furthermore, when the area is large, the movement distance in each direction also becomes long, making it difficult to induce the cathode spot. Therefore, in such cases, grooves 5 are provided separately for multiple divided induction regions, and continuous raised portions 6 are formed separately. As an example, an example of a case where the cathode surface 11A is rectangular (exclusively rectangular) is shown in FIGS. 6 and 7 . As shown in these figures, when a cathode 11 having a rectangular cathode surface 11A (the cathode 11 itself is a rectangular parallelepiped) is used, induction regions 7A, 7B are set in multiple locations (two locations in the figure) on the cathode surface 11A, and grooves 7 are provided in each of the induction regions 7A, 7B.

[0064] As shown in FIG. 6 , when the cathode surface 11A is rectangular and the length of the long side is approximately twice the length of the short side, the rectangle is divided into two along the long side, and each is designated as a separate induction region 7A, 7B. If the long side is longer, the rectangle may be divided into three or more parts. Grooves 5A, 5B, each of which has a spiral (spiral) shape in plan view, are provided in the divided induction regions 7A, 7B. By providing individual grooves 5A, 5B in each induction region 7A, 7B, each induction region 7A, 7B has its own spiral (spiral) raised portion 6A, 6B in plan view. The center of the spiral (spiral) shape in plan view can be set arbitrarily, but the center of the induction region 7A, 7B can be set as the center. When the cathode surface 11A is a rectangle elongated on one side, the movement distance of the cathode point in the long side direction becomes long, but by dividing it, the movement distance in the long side direction can be shortened. In this type of configuration, a trigger electrode is provided for each induction region 7A, 7B, and both induction regions 7A, 7B are simultaneously or alternately ignited to generate a vacuum arc discharge, thereby enabling the cathode material to be emitted from both induction regions 7A, 7B. Note that, although grooves 5A, 5B of the same shape (spiral in plan view) are formed in both induction regions 7A, 7B, the individual shapes may be different.

[0065] Similarly, as shown in Fig. 7, the induction regions 7A and 7B, which are divided into two along the long side of the cathode surface 11A, may be provided with grooves 5A and 5B that are generally spiral (or spiral) in plan view based on a square, thereby individually forming raised portions 6A and 6B that are generally spiral (or spiral) in plan view. In this case, the center of the generally spiral (or spiral) in plan view can also be set arbitrarily, but it can be the center of each induction region 7A and 7B. Furthermore, as in the case of Fig. 6, the entire cathode surface 11A can be used by simultaneously or alternately generating vacuum arc discharges in the two induction regions 7A and 7B to appropriately release the cathode material.

[0066] In any of the modified examples, the spiral (or approximately spiral) shape may be replaced by concentric circles or similar quadrangles. When the cathode surface 11A is another polygonal shape, two or more induction regions may be set, each of which may be provided with grooves 5 of a different shape and have raised portions 6 formed as appropriate. By providing a trigger electrode for generating a vacuum arc discharge individually for each induction region, the cathode material can be emitted from each induction region.

[0067] Furthermore, in the case of a configuration in which a magnetic field generating means is provided behind the cathode 11 (on the opposite side to the discharge surface), by individually installing a magnetic field generating means behind each of the induction regions 7A, 7B, it is also possible to induce the movement direction of the cathode spot in each of the induction regions 7A, 7B. The cross-sectional shape, pitch P, and other configurations of the grooves 5A, 5B are the same as those in the first embodiment, and the shape and various dimensions can be adjusted as necessary.

[0068] <Embodiment of Vacuum Arc Discharge Generator> This embodiment of the vacuum arc discharge generator uses the cathode 11 of any of the various forms described above, and the cathode surface 11A is arranged in a state where it can be contacted by the trigger electrode 14. Specifically, as shown in FIG. 8( a), the cathode surface 11A of the cathode 11 is disposed facing the trigger electrode 14. That is, the cathode surface 11A is arranged in the direction in which the cathode material is emitted, and when an arc discharge occurs on the cathode surface, plasma is generated, causing the cathode material emitted from the cathode surface to move toward the workpieces A to H and be supplied through the opening of the film formation chamber 3, thereby enabling film formation on the workpieces A to H inside (see FIG. 1).

[0069] 8A, in this embodiment, a substantially cylindrical anode 12 is disposed to form a region that serves as a transport path for evaporated particles, and a coil-shaped electromagnet 21 is disposed around the outer periphery of the substantially cylindrical anode 12. However, the anode 12 does not need to be substantially cylindrical, and the chamber (vacuum vessel) itself may serve as the anode. The electromagnet 21 need not be disposed. Furthermore, while the figure illustrates a state in which a magnetic field generating means 15 is disposed behind the cathode 11 (on the opposite side of the discharge surface (cathode surface 11A)), the magnetic field generating means 15 may not be disposed, and may be constituted by a permanent magnet.

[0070] Experimental Example: An experiment was conducted to determine whether a cathode spot can be induced by a protrusion using the cathode embodiment described above. The vacuum arc discharge generator used in the experiment, as shown in FIG. 8( a), included a cathode (graphite cathode) 11 with a surface processed into various shapes, installed in a chamber. One contact point with a trigger electrode 14 was provided on the cathode surface 11A. A roughly cylindrical anode 12 was placed in front of the discharge surface of the cathode 11 to form a transport path for evaporated particles. A coiled electromagnet 21 was placed around the periphery of the roughly cylindrical anode 12 to generate an induced magnetic field that guided charged particles generated by evaporation of the film-forming material in a predetermined direction. Furthermore, a permanent magnet 15 was placed behind the cathode 11 (on the opposite side of the discharge surface) outside the chamber, spaced 10 mm from the outer surface of the chamber.

[0071] In order to confirm the state resulting from changes in only the depth and pitch of the grooves 5, the cathodes 11 used were provided with grooves 5 having the same cross-sectional shape. That is, as shown in FIG. 8( b), the grooves 5 were configured with two side surfaces, one of which, 5 a, was inclined (not perpendicular to the imaginary smooth plane X), and the other, 5 b, was perpendicular to the imaginary smooth plane X, so as to prevent the formation of any remaining portions on the original cathode surface of the cathode 11 (see FIG. 3). The width dimension of one side surface 5 a was defined as pitch P, and the depth dimension of the other side surface 5 b in the perpendicular direction was defined as depth D. Cathode 11 was fabricated with grooves 5 of various shapes, differing only in these dimensions D and P. The shape of the grooves 5 in a plan view was all the same, unified as a spiral (spiral) shape based on a circle as shown in FIG. 4( a). Other conditions were as shown in the table below.

[0072]

[0073] In the experiment, cathodes 11 made to individual shapes were placed, and a contact point with a single trigger electrode was set at a specific location, and vacuum arc discharge was generated by igniting the trigger electrode. The vacuum arc discharge was generated for two minutes, and in order to maintain the vacuum arc discharge during this time, if the arc discharge did not continue, the trigger electrode repeatedly ignited the arc. The dimensions of the depth D and pitch P of the cathodes 11 used in the experiment, and the results of the number of times the arc was extinguished in two minutes are shown in the table below. The fewer the number of times the arc was extinguished, the better.

[0074]

[0075] According to the above results, when the cathode 11 in which the grooves 5 were formed with a pitch P of 1.0 mm and a depth D of 0.1 mm was used, a vacuum arc discharge was generated continuously for two minutes by a single arcing, which indicates that the discharge was stable and was found to be a suitable condition.

[0076] Furthermore, the above results also revealed that even under the same conditions of groove depth D, differences in the dimension of pitch P result in differences in discharge stability (a smaller number of arc extinctions is desirable). As a result, it was found that a dimension of pitch P of 1.0 mm is preferable.

[0077] Therefore, a comparative experiment was also conducted in which the pitch P was set to 1.0 mm and the groove depth D was set to 0.5 mm, but the discharge was not stable. In this case, the cross-sectional shape of the groove 5 was rectangular (with two perpendicular side surfaces and a parallel bottom surface). As a comparative experiment, a similar experiment was also conducted on a sample with a smooth cathode surface without grooves, but the result was that the arc was extinguished 9 times in 2 minutes.

[0078] Furthermore, after generating a vacuum arc discharge for two minutes, the state of the cathode surface 11A was observed. For comparison, a cathode without grooves 5 (i.e., a smooth surface) on the cathode surface 11A was also observed when a vacuum arc discharge was performed for two minutes. The results are shown in Figure 9 . Figure 9(a) shows a schematic diagram of the contact point T of the trigger electrode in a plan view of the cathode 11. Figure 9(b) shows the cathode with the most stable discharge (groove pitch P of 1.0 mm, depth D of 0.1 mm). Figure 9(c) shows the case of a smooth surface. Note that the shape of the grooves 5 is omitted in Figure 9(b). The shaded (grayscale) areas in Figures 9(b) and 9(c) indicate the areas where the cathode material was released (consumed). Images of the cathode surface 11A after the experiment were taken, but because the entire surface is black, it is difficult to determine the state of the released (consumed) cathode material, so these images are shown in the figures.

[0079] As can be seen from the results in Figures 9(b) and (c), when the cathode surface 11A had spiral grooves (as in Figure 9(b)), the cathode spot moved in an arc-like manner. However, when the cathode surface 11A was smooth and had no grooves (as in Figure 9(c)), the cathode spot moved up and down but did not move to the right half of the cathode surface 11A. It was confirmed from a video taken during discharge that the movement of the arc-shaped cathode spot in Figure 9(b) rotates clockwise in the figure. Furthermore, considering that the arc was extinguished only once during the two-minute discharge, the experimental results shown in Figure 9(b) indicate that the moving cathode spot is continuous, and therefore it is determined that it repeats two or more revolutions.

[0080] The state of the other specimens after the vacuum arc discharge was also observed, and visual inspection revealed that, for specimens with a relatively low number of arc extinctions (5 to 7 times in 2 minutes) among the experimental results shown in the table above, it was possible to clearly confirm that the cathode spot had moved in an arc shape overall. On the other hand, for specimens with a relatively high number of arc extinctions (13 or more times in 2 minutes), it was possible to confirm that the cathode spot had moved in an arc shape, although the movement distance was short.

[0081] From the above results, it was found that by forming grooves on the cathode surface, it is possible to induce the movement of the cathode spot in the direction of the continuous grooves. Furthermore, when the arc discharge is in a stable state, the cathode material can be emitted from the entire cathode surface because the arc repeats multiple revolutions, and the cathode material can be consumed over the entire cathode surface.

[0082] <Summary> As described above, according to the embodiment of the present invention, the presence of the elongated raised portions 6 formed by providing the elongated grooves 5 on the cathode surface 11A induces movement of the cathode spot, thereby gradually varying the emission position of the cathode material. As a result, the cathode material is evaporated and emitted from the entire cathode surface 11A, enabling efficient use of the cathode 11. Since such movement of the cathode spot is induced by the shape of the grooves 5 in a plan view, it is possible to control the movement of the cathode spot.

[0083] Although the embodiments and examples of the present invention have been described above, the present invention is not intended to be limited to these embodiments. Therefore, the elements constituting the above embodiments may be changed or other elements may be added. For example, by changing the cross-sectional shape of the groove 5, the cross-sectional shape of the formed raised portion 6 also changes depending on the shape of the groove 5, and therefore the cross-sectional shape may be modified in various ways.

[0084] A modification is shown in Figure 10. For example, as shown in Figure 10(a), of the two side surfaces 5a and 5b that form the groove 5, one side surface 5a is kept inclined while the other side surface 5b is also inclined. Even if the angle θb of inclination in this case is an acute angle, the raised portion 6 has a vertex 50, and therefore, the same effect as the example of the cross-sectional shape of the groove 5 in the first embodiment (see Figure 3(a)) can be obtained.

[0085] 10(b), a configuration may be adopted in which a remaining portion 60 is formed in which a part of the original cathode surface (the same surface as the imaginary smooth plane X) remains, and the other side surface 5b is inclined. In this case, the angle θb by which the other side surface 5b is inclined is an obtuse angle, and a configuration having a bottom surface 5c is provided, which is similar to the example of the cross-sectional shape of the groove portion 5 in the first embodiment (see FIG. 3(b)), and which can obtain the same effect, except that the remaining portion 60 and the bottom surface 5c are added to the apex 50 of the protrusion 6.

[0086] Furthermore, although the magnetic pole of the magnetic field generating means (e.g., permanent magnet) 15 that contacts the back of the cathode 11 (the opposite side of the discharge surface) is shown in the figure with the south pole on the cathode side, the magnetic pole may be reversed. In this case, it is expected that the movement direction of the cathode point during arc discharge will be reversed. Furthermore, even if the magnetic field generating means 15 is eliminated, it is expected that the cathode point will be guided along the longitudinal direction of the protrusion 6, considering that the protruding portion of the cathode surface 11A may be preferentially selected.

[0087] The cathode 11 of the present invention may have various variations as long as it has the basic configuration described above. One possible variation is that the cathode 11 does not have a single cathode surface 11A, but rather has multiple cathode surfaces. Examples of such variations are shown in FIG. 11 . Note that (b) and (d) in FIG. 11 are perspective views of a rectangular column-shaped cathode, while the others are perspective, partial cross-sectional views of a cylindrical cathode. The shaded areas (grayscale) in the figures indicate the surfaces that function as cathode surfaces for emitting cathode material.

[0088] Therefore, for example, as shown in Figures 11(a) and (b), the side portion 11B of the cathode 11 is tapered, and this tapered side portion 11B also functions as a cathode surface. To make this side portion 11B function as a cathode surface means that a groove 5 is also provided in the side portion 11B, and a corresponding protrusion 6 is formed. In this configuration, the cathode material can be emitted from the side portion 11B (cathode surface) as well as the basic flat portion 11A (cathode surface). In this case, the contact point with the trigger electrode may be either the flat portion 11A or the side portion 11B.

[0089] 11(c) and 11(d), the peripheral edge of the flat portion (cathode surface) 11A may be chamfered, and the chamfered portion 11C may function as the cathode surface. In such a configuration, grooves 5 and protrusions 6 are provided, as in the case where the tapered side portion 11B functions as the cathode surface (see FIG. 11(a) or 11(b)).

[0090] Furthermore, as shown in Figures 11(e) and (f), it is also conceivable to raise the peripheral edge of the flat portion of the cathode 11 (machining the inside into a concave shape) and have the inner flat portion 11D function as the cathode surface. In this case, depending on the processing convenience, the inner end surface 11Ea of the raised peripheral portion 11E may be perpendicular to the surface of the flat portion 11D (the configuration shown in Figure 11(e)), or may be tapered (the configuration shown in Figure 11(f)). In such cases, it is sufficient to have only the flat portion 11D function as the cathode surface. Of course, if processing is not difficult, there is no problem in having the inner end surface 11Ea function as the cathode surface. Note that in these exemplary cases, the moving cathode point does not deviate from the outer peripheral edge of the cathode 11, which has the advantage of reducing the number of times the vacuum arc discharge is extinguished.

[0091] In addition to the various conceivable forms of the cathode 11 as described above, if necessary, cathodes 11 of various shapes may be used, and by forming protrusions 6 by providing appropriate grooves 5 on the surface that is to function as the cathode surface, it becomes possible to induce cathode spots as shown in the present invention.

[0092] REFERENCE SIGNS LIST 1 Vacuum arc discharge generator 2 Plasma duct 3 Film formation chamber 4 Insulated lead-in terminal 5, 5A, 5B, 51, 52, 59 Groove portion 5a One side surface of groove portion 5b Other side surface of groove portion 5c Bottom surface of groove portion 6, 6A, 6B, 61, 62, 69 Raised portion 7A, 7B Induction region 11 Cathode 11A Cathode surface 11B Tapered side portion (cathode surface surface) 11C Chamfered portion (cathode surface surface) 11D Inner flat portion (cathode surface surface) 11E Peripheral portion 11Ea Inner end surface of peripheral portion 12 Anode 13 Arc power supply 14 Trigger electrode 15 Magnetic field generating means 21 Magnetic field generating unit (coil-shaped electromagnet) 31 Workpiece holding means 50 Upper end of side surface (peak of raised portion) 60 Remaining part D Depth of groove P Pitch of groove W Width direction of raised part X Virtual smooth plane θa, θb Angle between the side of groove and virtual smooth plane T Contact point of trigger electrode

Claims

1. A cathode in a vacuum arc discharge generator for generating and maintaining vacuum arc discharge plasma, which is installed in a vacuum arc evaporation device that generates plasma by conducting an arc discharge between a cathode and an anode connected via a power source in a vacuum and vaporizes the cathode material that constitutes the cathode for vapor deposition processing, and which comprises a cathode that is an evaporation source and a trigger electrode arranged for inducing arc discharge, wherein the cathode has at least one cathode surface that serves as an emission surface from which the cathode material is emitted, and the cathode surface is provided with one or more continuous elongated grooves, and the grooves are arranged adjacent to each other at a predetermined pitch to form one or more continuous raised portions between adjacent grooves.

2. The cathode in a vacuum arc discharge generator as described in claim 1, wherein the groove portion has at least two side surfaces, one or both of which are formed at an angle that is not perpendicular to an imaginary smooth plane of the smooth cathode surface when the state before the groove portion is provided is assumed.

3. A cathode in a vacuum arc discharge generator according to claim 1, wherein the groove portion has at least two side surfaces, and the two side surfaces form a substantially V-shaped cross section.

4. A cathode in a vacuum arc discharge generator as described in claim 1, wherein the grooves have a depth to their deepest point in the range of 0.01 mm to 5 mm, and the pitch between adjacent grooves is in the range of 0.01 mm to 5 mm.

5. A cathode in a vacuum arc discharge generator according to any one of claims 1 to 4, wherein the cathode surface of the cathode is circular, the groove is formed in a single continuous spiral from the center of the cathode surface, and the raised portion is raised in an area adjacent to the spiral groove.

6. A cathode in a vacuum arc discharge generator according to any one of claims 1 to 4, wherein the cathode surface of the cathode is circular, the grooves are formed in a plurality of concentric circles centered on the center point of the cathode surface, and the raised portions are raised in areas adjacent to the concentric grooves.

7. A cathode in a vacuum arc discharge generator as set forth in any one of claims 1 to 4, wherein the cathode surface of the cathode is circular, the grooves are formed by a plurality of similar polygons, and the similar polygons are formed so that the ratio of similarity increases successively from the center to the periphery of the cathode surface while the pitch between adjacent polygons is constant, and the raised portions are raised in areas where the grooves formed by similar polygons are adjacent.

8. The cathode in a vacuum arc discharge generator according to claim 7, wherein the groove portion is composed of a single, approximately spiral continuous line, and has a continuous shape that forms an approximately similar polygon based on the similar polygon.

9. A cathode in a vacuum arc discharge generator as set forth in any one of claims 1 to 4, wherein the cathode surface of the cathode is configured in a polygonal shape, the grooves are formed by a plurality of polygons similar to the polygons of the cathode surface, and the similar polygons are formed so that the ratio of similarity increases successively from the center to the periphery of the cathode surface while the pitch between adjacent polygons is constant, and the raised portions are raised in areas where the grooves formed by similar polygons are adjacent.

10. The cathode in a vacuum arc discharge generator as described in claim 9, wherein the groove portion is composed of a single, approximately spiral continuous line, and is formed into a continuous shape while forming an approximately similar polygonal shape based on the similar polygonal shape.

11. A cathode in a vacuum arc discharge generator according to any one of claims 1 to 4, wherein the cathode surface of the cathode is configured in a polygonal shape, the grooves are formed in a continuous spiral shape from any plurality of positions on the cathode surface, and the raised portions are raised in the spiral grooves formed in each of the grooves in areas adjacent to each groove.

12. A vacuum arc discharge generator using the cathode according to any one of claims 1 to 11, characterized in that the cathode is arranged so that a trigger electrode can contact the cathode surface.

13. A vacuum arc discharge generator as claimed in claim 13, further comprising magnetic field generating means, said magnetic field generating means being disposed on the opposite side of the discharge surface of said cathode at an appropriate distance from said cathode.

Images