Hard carbon coating equipment

Abstract

To provide a film deposition apparatus of a hard carbon coating capable of obtaining a sufficient hardness, an adhesion and a film deposition rate of a coating of a hard carbon film.SOLUTION: A bias device 44 of a film deposition apparatus of a hard carbon coating 30 is equipped with a polarity inversion suppression device 46. When a positive ion is momentarily supplied from a co-axial type arc-plasma gun 40 to a tool base material 22 during a deposition, an inversion of a polarity of the tool base material 22 in deposition is suppressed by the polarity inversion control device 46. Consequently, the inversion of the polarity of the tool base material 22 in deposition is suppressed, and therefore, a sufficient hardness, an adhesion, and a film deposition rate of the hard carbon coating deposited on the tool base material 22 are obtained.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a hard carbon film forming apparatus for depositing a hard carbon film on a substrate as an object.

Background Art

[0002] In various processing tools such as cutting tools like drills, end mills, milling cutters, and inserts, non-cutting tools such as raising taps, forging tools, and press dies, or friction parts that require wear resistance, etc., it has been proposed to improve wear resistance and durability by coating the surface of a substrate made of cemented carbide or high-speed tool steel (HSS) with a hard carbon film. The hard carbon film is a film having a dense amorphous structure containing diamond and has a higher hardness compared to compound films such as TiAlN and CrN.

[0003] In order to coat such a hard carbon film, for example, a hard carbon film forming apparatus using a coaxial arc plasma gun described in Patent Document 1 has been proposed. This coaxial arc plasma gun does not use gas for the generation of electrons in an ultra-high vacuum chamber with a vacuum degree higher than 10 -5 Pa, so carbon particles with high kinetic energy can be densely deposited, and a hard carbon film with high adhesion and high purity can be formed.

[0004] Specifically, the hard carbon film deposition apparatus comprises a vacuum chamber for housing a substrate, a coaxial arc plasma gun, and an arc power supply unit for driving the coaxial arc plasma gun. The coaxial arc plasma gun comprises a cylindrical cathode electrode made of graphite, a cylindrical insulator that holds its outer ring, a trigger electrode attached to the tip of the cylindrical insulator, and a large-diameter cylindrical anode electrode that concentrically houses an inner electrode assembly in which the trigger electrode is attached to the outer circumference of the cylindrical insulator and the cathode electrode is inserted into the cylindrical insulator, thereby concentrically assembling the trigger electrode, cylindrical insulator, and cathode electrode. The arc power supply unit comprises an arc power supply positioned between the cathode electrode and ground, a trigger power supply positioned between the cathode electrode and trigger electrode, and a capacitor positioned between the cathode electrode and ground.

[0005] As a result, in the above-mentioned coaxial arc plasma gun, electrons are generated from the trigger electrode by surface discharge at a predetermined interval to trigger the device, and the positive charge stored in the capacitor is rapidly discharged to the cathode electrode to ionize the graphite, which is the target material constituting the cathode electrode, into plasma (positive ions). In other words, the target is ionized by pulsed arc discharge, and then high-energy positively charged graphite particles are scattered from the tip opening of the cylindrical anode electrode toward the substrate at ground potential and adhered to the substrate. This cycle is repeated, and a hard carbon film is formed on the surface of the substrate. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-063958 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, with conventional hard carbon film deposition equipment as described above, supplying a large amount of ion current to increase the deposition rate due to industrial requirements sometimes did not result in the desired hardness, adhesion, and deposition rate of the hard carbon film.

[0008] The present invention was made against the above circumstances, and its objective is to provide a hard carbon film deposition apparatus that can obtain sufficient hardness, adhesion, and deposition rate for a hard carbon film. [Means for solving the problem]

[0009] Based on the above circumstances, the inventors conducted various studies and concluded that when the amount of charge discharged from the capacitor per cycle increases and a large amount of positively charged graphite particles are scattered toward the substrate all at once, the grounded substrate lacks the energy to attract the ionized positively charged graphite particles, resulting in insufficient adhesion and adhesion speed. To resolve this issue, they performed film deposition using a negative bias power supply that applies a negative voltage lower than the ground potential to the substrate. However, simply applying a negative voltage to the substrate was insufficient in capacity to handle the repeatedly occurring instantaneous supply of positive ions, inevitably causing the substrate's polarity to reverse to a positive potential. As a result, the hardness, adhesion strength, and deposition speed of the film fixed to the substrate decreased. In response to this, further research revealed that actively releasing the positive charge of the substrate to ground in response to the instantaneous supply of positive ions effectively suppresses the reversal of the substrate's polarity in response to the instantaneous supply of positive ions. This invention is based on such findings.

[0010] In other words, the gist of the first invention is a hard carbon film deposition apparatus comprising a coaxial arc plasma gun that ionizes target graphite with pulsed arc discharge and repeatedly scatters high-energy positively charged graphite particles from the tip opening of a cylindrical anode electrode toward a substrate at ground potential to adhere to the substrate and deposit a hard carbon film on the substrate, and a bias device that applies a negative bias to the substrate during film deposition, wherein the bias device includes a polarity reversal suppression device that suppresses the reversal of the polarity of the substrate when instantaneous positive ions are supplied to the substrate from the coaxial arc plasma gun during film deposition.

[0011] The gist of the second invention is that, in the first invention, when the substrate is about to change from negatively charged to positively charged during film formation, the polarity reversal suppression device switches the potential of the substrate to the ground potential, thereby suppressing the reversal of the polarity of the substrate during film formation.

[0012] The gist of the third invention is that, in the first or second invention, the bias device includes a negative bias power supply device that applies a negative bias to the substrate during film formation.

[0013] The gist of the fourth invention is that, in the third invention, the bias device includes a synchronization signal supply device that outputs a timing signal synchronized with the discharge timing of the coaxial arc plasma gun, and applies a negative bias from the negative bias power supply device to the substrate at the negative bias application start time and negative bias application time represented by the timing signal.

[0014] The gist of the fifth invention is that, in the fourth invention, the synchronization signal supply device is equipped with a manual regulator for manually adjusting the negative bias application start time and negative bias application time represented by the timing signal.

[0015] The gist of the sixth invention is that, in any one of the third to fifth inventions, the negative bias power supply device includes a dedicated negative bias capacitor for suppressing positive charging of the substrate and maintaining a negative bias in response to the instantaneous supply of positive ions to the substrate during film formation from the coaxial arc plasma gun. [Effects of the Invention]

[0016] According to the hard carbon film deposition apparatus of the first invention, a polarity reversal suppression device is provided in the bias device, and when instantaneous positive ions are supplied to the substrate from the coaxial arc plasma gun during film deposition, the polarity reversal suppression device suppresses the reversal of the polarity of the substrate during film deposition. As a result, the reversal of the polarity of the substrate during film deposition is suppressed regardless of the supply of positive ions, so that sufficient hardness, adhesion, and deposition rate of the hard carbon film deposited on the substrate can be obtained.

[0017] According to the hard carbon film deposition apparatus of the second invention, the polarity reversal suppression device suppresses the reversal of the polarity of the substrate during film deposition by switching the potential of the substrate to the ground potential when the substrate attempts to change from negatively charged to positively charged during film deposition. As a result, the reversal of the polarity of the substrate during film deposition is suppressed regardless of the supply of positive ions, so that sufficient hardness, adhesion, and deposition rate of the hard carbon film deposited on the substrate can be obtained.

[0018] According to the hard carbon film deposition apparatus of the third invention, the bias device includes a negative bias power supply device that applies a negative bias to the substrate during film deposition. As a result, the polarity of the substrate is made negative by the negative bias power supply device during film deposition. This suppresses the reversal of the polarity of the substrate during film deposition regardless of the supply of positive ions, thereby obtaining sufficient hardness, adhesion, and deposition rate of the hard carbon film deposited on the substrate.

[0019] According to the hard carbon film forming apparatus of the fourth invention, the bias device includes a synchronization signal supply device that outputs a timing signal synchronized with the discharge timing of the coaxial arc plasma gun, and a negative bias is applied to the base material from the negative bias power supply device at the start time of negative bias application and the negative bias application time represented by the timing signal. Thereby, since the negative bias is applied in an appropriate time zone synchronized with the discharge timing of the coaxial arc plasma gun, sufficient hardness, adhesion, and film forming speed of the hard carbon film formed on the base material can be obtained.

[0020] According to the hard carbon film forming apparatus of the fifth invention, since the synchronization signal supply device includes a manual adjuster for manually adjusting the start time of negative bias application and the negative bias application time represented by the timing signal, there is an advantage that the timing signal synchronized with the discharge timing of the coaxial arc plasma gun can be appropriately adjusted according to the material.

[0021] According to the hard carbon film forming apparatus of the sixth invention, the negative bias power supply device includes a dedicated negative bias capacitor for suppressing the positive charging of the base material and maintaining the negative bias in response to the supply of instantaneous positive ions to the base material during film formation from the coaxial arc plasma gun. Thereby, when supplying instantaneous positive ions to the base material during film formation, the inversion of the polarity of the base material is suppressed, so that the inversion of the polarity of the base material during film formation is suppressed without increasing the scale of the negative bias power supply device, and sufficient hardness, adhesion, and film formation speed of the hard carbon film formed on the base material can be obtained.

Brief Description of the Drawings

[0022] [Figure 1] FIG. 16 is a front view showing a drill, which is an example of a cutting tool in which a hard carbon film is adhered to the surface of a cutting part by a hard carbon film forming apparatus provided with a bias device according to an embodiment of the present invention. [Figure 2] FIG. 19 is an enlarged bottom view showing the drill of FIG. 1 from the tip side for explaining the drill. [Figure 3]It is a schematic diagram for explaining the configuration of a hard carbon film forming apparatus according to an embodiment of the present invention when forming a film on a tool base material for a drill in FIG. 1. [Figure 4] It is a schematic diagram for explaining the configuration of a coaxial type arc plasma gun used in the hard carbon film forming apparatus of FIG. 3. [Figure 5] In the hard carbon film forming apparatus of FIG. 3, it is a schematic diagram for explaining the configuration and operation of a bias device that applies a bias potential to the tool base material during film formation, and it is a diagram showing a state where the polarity determination suppression device provided in the bias device does not make a ground connection to the tool base material. [Figure 6] In the hard carbon film forming apparatus of FIG. 3, it is a schematic diagram for explaining the configuration and operation of a bias device that applies a bias potential to the tool base material during film formation, and it is a diagram showing a state where the polarity inversion suppression device provided in the bias device makes a ground connection to the tool base material. [Figure 7] It is a time chart for explaining the operation of the negative bias power supply device of FIGS. 5 and 6. [Figure 8] It is a chart showing the film formation conditions and film characteristics of a plurality of samples prepared by the present inventors for film characteristic evaluation. [Figure 9] It is a chart showing the film formation conditions of two types of samples prepared by the present inventors for composition evaluation. [Figure 10] It is a graph showing the Raman spectroscopic analysis results of a sample obtained by a conventional hard carbon film forming apparatus among the two samples in FIG. 9. [Figure 11] It is a graph showing the Raman spectroscopic analysis results of a sample obtained by a hard carbon film forming apparatus equipped with a polarity inversion suppression device, a negative bias power supply device, and a negative bias dedicated capacitor among the two samples in FIG. 9.

Embodiments for Carrying Out the Invention

[0023] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings illustrate the main parts related to the invention, and dimensions, shapes, etc. are not necessarily drawn accurately. [Examples]

[0024] Figures 1 and 2 show a drill 10, which is an example of a part coated with a hard carbon film by a hard carbon film deposition apparatus 30 according to one embodiment of the present invention. Figure 1 is a front view seen from a direction perpendicular to the axis O, and Figure 2 is an enlarged bottom view seen from the tip side where the cutting edge 12 is provided. The drill 10 is made of a tool base material 22 which is made of cemented carbide or high-speed tool steel (HSS). This drill 10 is a two-blade twist drill, with a shank 14 and a body 16 integrally provided in the axial direction, and a pair of grooves 18 twisted clockwise around the axis O are formed in the body 16. A pair of cutting edges 12 are provided at the tip of the body 16 corresponding to the grooves 18, and when viewed from the shank 14 side, they rotate clockwise around the axis O, cutting a hole with the cutting edges 12, and chips are discharged through the grooves 18 to the shank 14 side. In Figure 1, the shaded area indicates the portion coated (adhered) with the hard carbon film 24.

[0025] Figure 3 is a schematic diagram illustrating the hard carbon coating deposition apparatus 30, or coaxial vacuum arc deposition apparatus, used in the manufacture of the drill 10. The hard carbon coating deposition apparatus 30 consists of a metal workpiece holder 32 that holds multiple workpieces, i.e., tool base materials 22 which are the substrates before the hard carbon coating 24 is applied; a rotary drive device 34 that rotates the workpiece holder 32 around a substantially vertical rotation center; a vacuum chamber 36 which serves as a processing container housing the tool base materials 22 and the like; and a vacuum pump that discharges the gas inside the vacuum chamber 36 to 10 -5 It is equipped with an exhaust system 38 that reduces the pressure to an ultra-high vacuum lower than approximately Pa, a coaxial arc plasma gun 40, an arc power supply unit 42, a bias device 44, and the like.

[0026] The arc power supply unit 42 drives the coaxial arc plasma gun 40 to emit arc plasma from its tip. The bias device 44 applies a bias voltage to the tool base material 22 via the workpiece holder 32 and the rotary drive device 34. The workpiece holder 32 holds the tool base material 22 in a position where its tip protrudes outward. The sheath heater H heats the tool base material 22 being deposited, which is held in the workpiece holder 32.

[0027] As shown in Figure 4, the coaxial arc plasma gun 40 is composed of a cylindrical cathode electrode KE which is a solid target made of graphite, a cylindrical insulator CE which is an insulator that holds the outside of the cathode electrode KE, a cylindrical trigger electrode TE attached to the tip of the cylindrical insulator CE, and an inner electrode assembly in which the trigger electrode TE is attached to the outer circumference of the cylindrical insulator CE and the cathode electrode KE is inserted into the cylindrical insulator CE, and the trigger electrode TE, cylindrical insulator CE and cathode electrode KE are assembled concentrically, and this inner electrode assembly is arranged concentrically within a cylindrical anode electrode AE ​​which has a larger diameter.

[0028] The arc power supply unit 42 includes an arc power supply AS connected between the cathode electrode KE and the earth E, a trigger power supply TS connected between the cathode electrode KE and the trigger electrode TE, and a capacitor C connected between the cathode electrode KE and the earth E.

[0029] In the coaxial arc plasma gun 40 configured in this way, electrons are generated by surface discharge from the trigger electrode TE at a predetermined frequency, for example, 100 Hz, triggering the gun. The charge stored in the capacitor C is then rapidly discharged to the cathode electrode KE, causing the graphite solid target constituting the cathode electrode KE to liquefy and vaporize, becoming plasma. High-energy plasma-formed graphite ion particles P are then scattered from the tip opening of the cylindrical anode electrode AE ​​toward the tool base material 22 by a pulsed arc discharge, thereby depositing a hard carbon coating 24 onto the tool base material 22.

[0030] In the hard carbon film deposition apparatus 30, the deposition operation is performed periodically in synchronization with the repeated charging and discharging of capacitor C in the arc power supply unit 42. Therefore, without using a cathode shutter or substrate shutter, the thickness of the carbon film deposited on the tool base material 22 can be controlled to a desired value by setting the number of charge and discharge cycles of capacitor C. Furthermore, since the hard carbon film deposition apparatus 30 does not use gas to generate electrons, 10 -5 A high-purity hard carbon film 24 can be formed under ultra-high vacuum conditions with a pressure lower than approximately Pa. Furthermore, because the plasma ionization rate is high at approximately 80% and the particle kinetic energy is high, a dense and highly adhesive hard carbon film 24 can be formed.

[0031] Figures 5 and 6 are schematic diagrams illustrating the configuration and operation of the bias device 44 in Figure 3. Figure 5 shows the ungrounded state of the tool base material 22 due to the bias device 44, and Figure 6 shows the grounded state of the tool base material 22 due to the bias device 44.

[0032] The bias device 44 comprises a polarity reversal suppression device 46, a synchronization signal supply device 48, and a negative bias power supply device 54. In order to obtain the hardness, adhesion, and deposition rate of the hard carbon coating 24 deposited on the tool base material 22, it maintains the polarity of the tool base material 22 as negative as possible during deposition, regardless of the periodic supply of a large amount of positive ions from the coaxial arc plasma gun 40, thereby suppressing polarity reversal of the tool base material 22 from negative potential to positive potential. In Figures 5 and 6, the circuit symbols shown in the blocks representing the polarity reversal suppression device 46 and the negative bias power supply device 54 are simplified representations of their functions, and in reality, they are composed of electrical circuits that operate to achieve those functions.

[0033] The polarity reversal suppression device 46 is installed between the tool base material 22 and the ground line EL. When the tool base material 22, which is being deposited by the coaxial arc plasma gun 40, attempts to reverse polarity from a negative bias potential supplied by the negative bias power supply device 54 to a positive potential, the device connects the tool base material 22 to the ground line EL to switch the potential of the tool base material 22 to the ground potential, thereby suppressing the reversal of polarity of the tool base material 22.

[0034] More specifically, the polarity reversal suppression device 46 includes a substrate potential detection circuit unit that detects the potential of the tool base material 22 being deposited with respect to the ground line EL using a coaxial arc plasma gun 40; a polarity reversal determination circuit unit that determines, based on the potential of the tool base material 22 detected by the substrate potential detection circuit unit and the rate of change of that potential (for example, the differential value of the potential), whether the tool base material 22 being deposited is about to reverse polarity from a negative bias potential supplied by a negative bias power supply unit 54 to a positive potential; and a ground line connection circuit unit that, when the polarity reversal determination circuit unit determines that the tool base material 22 being deposited is about to reverse polarity from a negative bias potential supplied by a negative bias power supply unit 54 to a positive potential, connects the tool base material 22 to the ground line EL to suppress the reversal of the substrate's polarity.

[0035] The synchronization signal supply device 48 includes a negative bias application start timing adjuster 50 and a negative bias application time adjuster 52, which adjust the negative bias application start time and negative bias application time, respectively, by the negative bias power supply device 54. For example, based on the potential of the cathode electrode KE of the coaxial arc plasma gun 40, the device supplies a timing signal ST to the negative bias power supply device 54, which represents the negative bias application start time and negative bias application time relative to the start time of pulsed arc discharge of the coaxial arc plasma gun 40. The negative bias application start timing adjuster 50 and the negative bias application time adjuster 52 are manual adjusters that adjust the negative bias application start time and negative bias application time, which are represented by the timing signal ST and are relative to the start time of irradiation of the coaxial arc plasma gun 40, according to manual operation.

[0036] The negative bias power supply unit 54 includes a negative bias power supply circuit 56 that generates a constant negative potential relative to the earth potential, for example -100V and 100kHz DC pulse-like negative bias, and a negative bias-dedicated capacitor 58 that is charged by the negative bias power supply circuit 56 and supplies negative charge to the tool base material 22 so that the polarity of the tool base material 22 is maintained as negative when a large amount of positive ion flow is instantaneously supplied from the coaxial arc plasma gun 40 to the tool base material 22. The negative bias-dedicated capacitor 58 applies a negative bias to the tool base material 22 according to the negative bias application start time and negative bias application time represented by the timing signal ST, thereby suppressing the reversal of the polarity of the tool base material 22. The negative bias-dedicated capacitor 58 is charged by the negative bias power supply circuit 56 during the period when the negative bias power supply unit 54 does not apply a negative bias to the tool base material 22.

[0037] Figure 7 is a time chart illustrating the operation of applying a negative bias to the tool base material 22 by the negative bias power supply unit 54, along with the periodically changing positive ion current from the coaxial arc plasma gun 40 (shown in the upper section). In Figure 7, time t1, which indicates the start of the irradiation cycle, is the start of the positive ion irradiation section by the coaxial arc plasma gun 40, i.e., the start of negative bias application. Time t2 is the end of negative bias application, time t3 is the end of that positive ion irradiation section, and time t4 indicates the end of this irradiation cycle. Preferably, the negative bias application section (time) (t1~t2) is set to approximately 50% of the positive ion irradiation section (time) in the first half of the positive ion irradiation section (t1~t3) which is repeated at a predetermined cycle.

[0038] Below, we will explain, using Figure 8, the film deposition conditions and evaluation results of the characteristics of the coatings deposited on each substrate when seven different samples, No. 1-1 to No. 1-7, with different deposition conditions, were deposited on a substrate (sample size: diameter 10 mm x thickness 5 mm) by the present inventors. Samples No. 1-1 to No. 1-7 were prepared using a hard carbon film deposition apparatus 30 under common deposition conditions for target material, introduced gas, substrate material, substrate temperature, processing pressure, output of coaxial arc plasma gun 40, and arc discharge frequency, but the bias conditions for the substrate during film deposition differed from one another.

[0039] Sample No. 1-1 was deposited with the substrate's bias voltage grounded to 0V. Sample No. 1-2 was deposited with a bias voltage of -100V and 100kHz continuously applied to the substrate from a negative bias power supply 54. Sample No. 1-3 was deposited with a bias voltage of -100V and 100kHz continuously applied to the substrate from a negative bias power supply 54, and with the polarity reversal suppression device 46 preventing the bias voltage of the substrate from reversing by grounding.

[0040] Samples No. 1-4 were deposited under the same conditions as Sample No. 1-3, but with the polarity reversal suppression device 46 removed to suppress bias voltage reversal, and with a dedicated negative bias capacitor 58 added. Sample No. 1-5 was deposited in the same negative bias power supply device 54 as Sample No. 1-3, but with a dedicated negative bias capacitor 58 added.

[0041] Sample No. 1-6 is equipped with a synchronization signal supply device 48 for controlling the on / off state of the negative bias power supply device 54 of sample No. 1-5. Sample No. 1-7 is formed with the negative bias-dedicated capacitor 58 removed from the negative bias power supply device 54 of sample No. 1-6.

[0042] The coating properties of each sample, from No. 1-1 to No. 1-7, were evaluated for coating hardness (GPa), peel critical load (N), and coating thickness (μm) under the following measurement conditions. (Coating hardness) Using a thin-film hardness tester compliant with ISO 14577-4:2016, the hardness H of the hard carbon coating 24 on the substrate was measured under the following conditions using the nanoindentation method specified in ISO 14577-4:2016. IT (GPa) was measured. • Test load: 5mN ·Load arrival time: 10 seconds ·Load holding time: 5 seconds • Load removal time: 10 seconds • Test points: 10 points

[0043] (Thin film critical load) Using a scratch tester, the thin-film critical load of the hard carbon coating 24 on the substrate was measured under the following measurement conditions. • Indenter: Diamond indenter with a 120° 0.2mm tip shape • Loading speed: 200 N / min Scratch speed: 10 mm / min

[0044] (Film thickness) The measurement was performed using a scale from secondary electron images of the cross-section of the hard carbon coating 24 on the substrate, observed using a scanning electron microscope. A larger coating thickness obtained under the same deposition conditions, such as the number of arc discharges, indicates a higher deposition rate.

[0045] In sample No. 1-2, despite a negative bias voltage of -100V and 100kHz being applied to the substrate by the negative bias power supply circuit 56, the film hardness and deposition rate (film thickness) were lower compared to sample No. 1-1, where the substrate was grounded. This is thought to be due to the substrate becoming positively charged. In sample No. 1-3, compared to sample No. 1-2, an improvement in film hardness and deposition rate (film thickness) was observed due to the suppression of positive charge accumulation on the substrate by the polarity reversal suppression device 46.

[0046] In sample No. 1-4, a dedicated negative bias capacitor 58 is used in the negative bias power supply 54 compared to sample No. 1-2, which allows for the maintenance of a certain degree of negative bias. However, the charging of positive charges is not completely suppressed, so although the hardness of the coating is improved, the critical peel load is reduced. In sample No. 1-5, a polarity reversal suppression device 46 is provided to suppress the charging of positive charges on the substrate compared to sample No. 1-2, and a dedicated negative bias capacitor 58 is added to the negative bias power supply 54. As a result, a negative bias is effectively applied to the substrate, and the hardness of the coating and the film deposition rate (film thickness) are further improved.

[0047] Sample No. 1-6 was equipped with a synchronization signal supply device 48 that supplied a timing signal ST synchronized with the irradiation of positive ions by a coaxial arc plasma gun 40, compared to Sample No. 1-5. A negative bias was applied to the substrate from a negative bias power supply device 54 only at the timing when the ion density was high among the positive ions irradiated from the coaxial arc plasma gun 40. As a result, a multilayer structure with significantly different film densities was created, and an improvement in adhesion force (peeling critical load) due to the relaxation of internal stress was observed. Sample No. 1-7 was equipped with a synchronization signal supply device 48 that supplied a timing signal ST synchronized with the irradiation of positive ions by a coaxial arc plasma gun 40, compared to Sample No. 1-3. Similar to Sample No. 1-6, an improvement in adhesion force (peeling critical load) was observed.

[0048] Of samples No. 1-1 to No. 1-7, those that met the acceptance criteria of having a film hardness of 51 GPa or higher, a peeling critical load of 31 N or higher, and a film thickness of 3.3 μm or higher were judged to be acceptable. Sample No. 1-1, which was rejected, was deposited with the substrate bias voltage grounded to 0V, and is therefore equivalent to a conventional product. In contrast, the deposition conditions for sample No. 1-2, which was rejected, included a negative bias power supply 54 that applied a negative bias to the substrate, and the deposition conditions for sample No. 1-4, which was rejected, included a negative bias power supply 54 and a dedicated negative bias capacitor 58, but the film hardness and film thickness were not as good as those of sample No. 1-1.

[0049] In contrast, the film deposition conditions for the acceptable samples No. 1-3, No. 1-5, and No. 1-6 all included the polarity reversal suppression device 46. According to the film deposition conditions for sample No. 1-7, which added the synchronization signal supply device 48 to the film deposition conditions for sample No. 1-3, the peeling critical load improved. According to the film deposition conditions for sample No. 1-5, which added the negative bias-dedicated capacitor 58 to the film deposition conditions for sample No. 1-3, the film hardness, peeling critical load, and film thickness were significantly improved. According to the film deposition conditions for sample No. 1-6, which added the synchronization signal supply device 48 and the negative bias-dedicated capacitor 58 to the film deposition conditions for sample No. 1-3, the film hardness, peeling critical load, and film thickness were significantly improved.

[0050] Next, the film deposition conditions and evaluation results of the characteristics of the films deposited on each substrate, when two types of samples No. 2-1 to No. 2-2 with different film deposition conditions were deposited on a substrate (sample size: diameter 10 mm x thickness 5 mm) by the present inventors, will be explained using Figures 9, 10, and 11.

[0051] Samples No. 2-1 and No. 2-2 were prepared using a hard carbon film deposition apparatus 30 under the same deposition conditions: target material, introduced gas, substrate material, substrate temperature, processing pressure, output of the coaxial arc plasma gun 40, and arc discharge frequency. However, the bias conditions for the substrate during deposition differed between the two samples. Specifically, sample No. 2-1 was deposited with the substrate bias voltage grounded to 0V. Sample No. 2-2 was deposited with a negative bias voltage of -100V and 100kHz continuously applied to the substrate from a negative bias power supply 54. Furthermore, a polarity reversal suppression device 46 prevented the substrate bias voltage from reversing by grounding, and a negative bias-dedicated capacitor 58 was provided in the negative bias power supply 54.

[0052] The coating properties of each sample, No. 2-1 to No. 2-2, were analyzed by Raman spectroscopy under the following conditions. (Raman spectroscopy) • Laser wavelength: 532nm • Laser output: 0.5mW

[0053] Figure 10 shows the Raman spectrum of sample No. 2-1, which was deposited without negative bias applied to the substrate. Figure 11 shows the Raman spectrum of sample No. 2-2, which was deposited with negative bias applied from the negative bias power supply 54, and the polarity reversal suppression device 46 prevented the bias voltage of the substrate from reversing by grounding, and a dedicated negative bias capacitor 58 was provided in the negative bias power supply 54.

[0054] In the Raman spectra of Figures 10 and 11, the 1333 cm⁻¹ spectrum is attributed to diamond. -1 The peak in the Raman spectrum of sample No. 2-2 is sharper and stronger than that of sample No. 2-1, indicating that the diamond crystallinity in the hard carbon coating 24 of sample No. 2-2 is higher.

[0055] As described above, the hard carbon film deposition apparatus 30 of this embodiment comprises a coaxial arc plasma gun 40 that ionizes the graphite of a target (cathode electrode KE) with pulsed arc discharge, and repeatedly scatters high-energy positively charged graphite particles (ionic particles P) from the tip opening of a cylindrical anode electrode AE ​​toward the tool base material (substrate) 22 at ground potential, thereby depositing a hard carbon film 24 on the tool base material 22, and a bias device 44 that applies a negative bias to the tool base material 22 during film deposition, wherein the bias device 44 includes a polarity reversal suppression device 46 that suppresses the reversal of the polarity of the tool base material 22 when instantaneous positive ions are supplied to the tool base material 22 from the coaxial arc plasma gun 40 during film deposition.

[0056] As a result, the polarity reversal suppression device 46 is provided in the bias device 44, and when positive ions are instantaneously supplied to the tool base material 22 during film formation from the coaxial arc plasma gun 40, the polarity reversal suppression device 46 suppresses the reversal of the polarity of the tool base material 22 during film formation. Therefore, since the reversal of the polarity of the tool base material 22 during film formation is suppressed regardless of the supply of positive ions, sufficient hardness, adhesion, and film formation rate of the hard carbon coating 24 formed on the tool base material 22 can be obtained.

[0057] Furthermore, according to the hard carbon film deposition apparatus 30 of this embodiment, the polarity reversal suppression device 46 switches the potential of the tool base material (substrate) 22 to the ground potential when the tool base material 22 attempts to change from negatively charged to positively charged during film deposition, thereby suppressing the reversal of the polarity of the tool base material 22 during film deposition. As a result, the reversal of the polarity of the tool base material 22 during film deposition is suppressed regardless of the supply of positive ions, so that sufficient hardness, adhesion, and deposition rate of the hard carbon film 24 deposited on the tool base material 22 can be obtained.

[0058] Furthermore, in the hard carbon film deposition apparatus 30 of this embodiment, the bias device 44 includes a negative bias power supply device 54 that applies a negative bias to the tool base material (substrate) 22 during film deposition. As a result, during the deposition of the hard carbon film 24, the polarity of the tool base material 22 is made negative by the negative bias power supply device 54. This suppresses the reversal of the polarity of the tool base material 22 during film deposition regardless of the supply of positive ions, thereby obtaining sufficient hardness, adhesion, and deposition speed of the hard carbon film 24 deposited on the tool base material 22.

[0059] Furthermore, according to the hard carbon film deposition apparatus 30 of this embodiment, the bias device 44 includes a synchronization signal supply device 48 that outputs a timing signal ST synchronized with the discharge timing of the coaxial arc plasma gun 40, and applies a negative bias from the negative bias power supply device 54 to the tool base material (substrate) 22 at the negative bias application start time and negative bias application time represented by the timing signal ST. As a result, the negative bias is applied at an appropriate time synchronized with the discharge timing of the coaxial arc plasma gun 40, so that sufficient hardness, adhesion, and deposition speed of the hard carbon film 24 deposited on the tool base material 22 can be obtained.

[0060] Furthermore, according to the hard carbon film deposition apparatus 30 of this embodiment, the synchronization signal supply device 48 is equipped with manual adjusters (negative bias application start timing adjuster 50, negative bias application time adjuster 52) for manually adjusting the negative bias application start timing and negative bias application time represented by the timing signal ST. This has the advantage that the timing signal ST synchronized with the discharge timing of the coaxial arc plasma gun 40 can be appropriately adjusted according to the material of the tool base material (substrate) 22 and the discharge frequency of the coaxial arc plasma gun 40.

[0061] Furthermore, according to the hard carbon film deposition apparatus 30 of this embodiment, the negative bias power supply unit 54 includes a dedicated negative bias capacitor 58 that maintains a negative bias by suppressing positive charging of the tool matrix 22 and supplying a negative charge to the tool matrix 22 in response to the instantaneous supply of positive ions to the tool matrix 22 from the coaxial arc plasma gun 40 during film deposition. As a result, in response to the instantaneous supply of positive ions to the tool matrix 22, a negative charge is supplied to the tool matrix 22 from the dedicated negative bias capacitor 58, thus maintaining a negative bias and suppressing polarity reversal of the tool matrix 22 when instantaneous positive ions are supplied to the tool matrix 22 during film deposition. Therefore, without increasing the capacity of the negative bias power supply unit 54, polarity reversal of the tool matrix 22 during film deposition is suppressed, and sufficient hardness, adhesion, and deposition speed of the hard carbon film 24 deposited on the tool matrix 22 can be obtained.

[0062] Although one embodiment of the present invention has been described above with reference to the drawings, the present invention can also be implemented in other embodiments.

[0063] For example, in the above-described embodiment, the tool base material 22 of the drill 10 was described as the substrate on which the hard carbon coating 24 was formed. However, various tool base materials such as cutting tools like drills, end mills, milling cutters, and turning tools, non-cutting tools like building taps, rolling tools, and press dies, or friction parts requiring wear resistance may be used as the base material.

[0064] Furthermore, in the above-described embodiment, the tool base material 22 was made of cemented carbide or high-speed tool steel, but it may be made of other metallic materials.

[0065] Furthermore, in the above-described embodiment, the hard carbon coating 24 was directly deposited on the tool base material 22, but it may also be deposited indirectly on the tool base material 22 via another film.

[0066] Although embodiments of the present invention have been described in detail above with reference to the drawings, these are merely examples, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of symbols]

[0067] 22: Tool base material (base material) 24:Hard carbon coating 30: Hard carbon film deposition apparatus 40: Coaxial Arc Plasma Gun 42: Arc power supply 44: Bias device 46: Polarity reversal suppression device 48: Synchronization signal supply device 50: Negative bias application start timing adjuster (manual adjuster) 52: Negative bias application time regulator (manual regulator) 54: Negative bias power supply 58: Capacitor specifically for negative bias AE: Anode electrode P: Ionic particles (graphite particles) KE: Cathode electrode (target) ST: Timing signal

Claims

1. A hard carbon coating deposition apparatus comprising: a coaxial arc plasma gun that ionizes a target graphite by pulse arc discharge, and repeatedly scatters high-energy positively charged graphite particles from a tip opening of a cylindrical anode electrode toward a substrate at a ground potential, causing the particles to deposit on the substrate, thereby depositing a hard carbon coating on the substrate; and a bias device that applies a negative bias to the substrate during coating, The bias device includes a polarity reversal suppression device that suppresses polarity reversal of the substrate when positive ions are momentarily supplied from the coaxial arc plasma gun to the substrate during film formation. A hard carbon coating deposition apparatus characterized by:

2. The polarity reversal suppression device suppresses the reversal of the polarity of the substrate during film formation by switching the potential of the substrate to a ground potential when the substrate is about to change from negatively charged to positively charged during film formation.

2. The hard carbon coating deposition apparatus according to claim 1, wherein:

3. The bias device includes a negative bias power supply device that applies a negative bias to the substrate during film formation.

3. The hard carbon coating deposition apparatus according to claim 1 or 2.

4. The bias device includes a synchronization signal supply device that outputs a timing signal synchronized with the discharge timing of the coaxial arc plasma gun, and applies a negative bias to the substrate from the negative bias power supply device at a negative bias application start time and a negative bias application time indicated by the timing signal.

4. The hard carbon coating deposition apparatus according to claim 3, wherein:

5. The synchronization signal supply device includes a manual adjuster for manually adjusting the negative bias application start time and negative bias application time indicated by the timing signal.

5. The hard carbon coating deposition apparatus according to claim 4, wherein:

6. The negative bias power supply device includes a negative bias dedicated capacitor for suppressing positive charging of the substrate and maintaining a negative bias in response to instantaneous supply of positive ions from the coaxial arc plasma gun to the substrate during film formation.

6. The hard carbon coating deposition apparatus according to claim 3, wherein the hard carbon coating deposition apparatus is a carbon coating deposition apparatus.

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