JP2012092380A - Vacuum arc deposition method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum arc deposition method capable of assuring a position of a cathode spot to be in a front of an evaporation surface of a cathode material, and improving stability of vacuum arc discharge.SOLUTION: By an annular magnet arranged behind a back surface portion of the cathode and in the atmosphere, and having an inner diameter larger than an outer diameter of the cathode, lines of magnetic force are made to cross the evaporation surface of the cathode material so as to make an acute angle toward a center axis side of the cathode in an outer edge portion of the cathode material. Herein, a value A expressed by A=IBsin2θ is set to 70,000 or more, where θ (degrees) is a crossing angle made by the lines of magnetic force and the evaporation surface in the outer edge portion of the cathode, B (Gauss) is a magnetic flux density, and I(A) is an arc discharge current.

Description

  The present invention relates to a vacuum arc vapor deposition method used exclusively for forming a wear-resistant coating on machine parts, tools, dies and the like.

  The vacuum arc deposition method is a thin film formation method in which arc discharge is generated between the anode and the cathode, and the cathode material is evaporated and deposited on the substrate. It is often used as.

  However, a large lump of coarse particles (also called droplets) having a diameter of several μm to several hundreds of μm are scattered from the cathode spot of the cathode material, and the coarse particles adhere to the substrate and are coated. It is known that the characteristics deteriorate.

  In addition, the cathode spot stagnates in the central part or outer edge of the cathode material, preventing the uniform consumption of the cathode material, the utilization efficiency of the cathode material is deteriorated, or the cathode material moves to a side other than the evaporation surface of the cathode material, There is also a problem that the discharge may be lost.

Japanese Patent Laid-Open No. 11-142073 discloses an evaporation source used in a vacuum arc deposition method for dealing with the above problems.
In this evaporation source, a ring-shaped magnetic body and a magnetic field generation source are arranged on the outer peripheral portion of the cathode evaporating material, and the magnetic field lines intersecting the outer peripheral portion of the cathode material so as to have an acute angle inward with respect to the evaporation surface. Form a magnetic field with

  In addition, by arranging magnetic field line changing means having a polarity opposite to that of the magnetic field generation source in the rear central portion of the cathode evaporating substance, an acute angle is formed outwardly with respect to the evaporating surface in the vicinity of the evaporating substance central portion. A magnetic field having crossed magnetic field lines is formed.

Japanese Patent Laid-Open No. 11-142073

  It is known that the cathode spot of the vacuum arc discharge easily moves in the direction in which the lines of magnetic force are inclined at an acute angle on the evaporation surface of the cathode material. This phenomenon is considered to be caused by the Lorentz force due to the arc discharge current and the magnetic field, and the degree of movement of the cathode spot is considered to affect both the arc current and the magnetic flux density of the magnetic field.

In film formation by vacuum arc deposition, when the arc current is changed to adjust the film formation speed, etc., the degree of cathode spot movement also changes, so the cathode spot is maintained at the proper position of the cathode material. It is considered that the magnetic flux density required to do this varies depending on the magnitude of the arc current.
However, these points are not described in the cited document.

  Therefore, in order to obtain a stable arc discharge region in which the cathode spot can be maintained on the evaporation surface of the cathode material, the present invention quantitatively determines a value that can be derived from the arc discharge current and the magnetic flux density by changing the arc current. It is an object of the present invention to provide a vacuum arc vapor deposition method that prevents movement of the cathode spot to the cathode side surface or the like in use, and can maintain stable arc discharge on the cathode evaporation surface.

In order to solve the above-mentioned problems, the present invention provides a vacuum arc vapor deposition method in which a cathode is dissolved by arc discharge to evaporate a cathode material, which is disposed in the atmosphere behind the back surface of the cathode and has an inner diameter of By means of an annular magnet larger than the outer diameter of the cathode, the magnetic lines of force at the outer edge of the cathode material are crossed so as to be at an acute angle to the central axis side of the cathode material with respect to the evaporation surface of the cathode material, Assuming that the intersection angle between the magnetic field lines and the evaporation surface is θ (degrees), the magnetic flux density is B (Gauss), and the arc discharge current is I (A), the absolute value of A indicated by A = IB ² sin2θ is 70000. It is characterized by the above.

  According to the present invention, when an arc evaporation source is used, the position of the cathode spot can be kept in front of the evaporation surface of the cathode material, and a vacuum arc deposition method that improves the stability of the vacuum arc discharge can be provided.

It is a figure which shows roughly an example of the vacuum arc vapor deposition apparatus which implement | achieves the method of this invention. FIG. 2 is a diagram schematically showing an outline of a magnetic field state in an arc evaporation source of the vacuum arc vapor deposition apparatus in FIG. 1. 2 shows an arrangement of cathodes and lines of magnetic force according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is an example of an arc vapor deposition apparatus for carrying out the present invention.

  A vacuum deposition apparatus 101 shown in FIG. 1 is arranged at a position facing the evaporation source 2 in the vacuum vessel 1 for film formation, an arc evaporation source 2 provided on the outer wall 11 of the vessel 1, and the vessel 1. It includes an exhaust device EX for setting the inside of the holder 3 of the film formation target article W and the vacuum vessel 1 to a reduced pressure atmosphere for forming a desired film.

  The holder 3 is rotatably supported by the support unit 4 and can be rotated by the rotation drive unit 5. A bias voltage can be applied from the bias power source 6 to the film formation target article W supported by the holder 3 via the holder 3 so that an ionized cathode material, which will be described later, can be attracted to form a smooth film. The article holder 3 may be provided with a heater for heating the article in forming the film.

  The exhaust device EX may be any device that can exhaust and decompress the inside of the container 1. For example, a device including an exhaust pump such as a turbo molecular pump, a diffusion pump, or a claion pump can be used.

  The vacuum vessel 1 is provided with a gas introduction part 7 for introducing a predetermined gas as required. The gas introduction part 7 is used as a part for introducing nitrogen gas into the container 1 when, for example, the evaporation source cathode material is chromium and a chromium nitride film is formed. It can be used as a gas introduction part for performing pretreatment such as cleaning pretreatment by electric discharge or the like.

  The arc evaporation source 2 includes a cathode 20, a trigger electrode 25, an arc discharge power source 24, and the like. The cathode 20 is supported by a conductive cathode holder 21, is located in the container 1, and is directed toward the article holder 3.

  In the illustrated example, the cathode holder 21 is attached to the outer wall 11 of the container 1 from the outside via the electrical insulating member 22 and is attached to the outer wall 11 so as to be pressed toward the outer wall 11 by the holding member 23. A space 211 is formed in a portion of the cathode holder 21 facing the back surface of the cathode 20. If desired, cooling water can be passed through a water circulation device (not shown) if desired.

Although not limited thereto, the cathode 20 has a short cylindrical shape here, and is formed of a material selected according to a film to be formed.
In this case, the grounded container 1 serves as the anode for the cathode.
As for the anode, for example, an anode surrounding the end portion of the cathode 20 may be separately provided.

  The trigger electrode 25 faces the end face (cathode evaporation surface) 20S of the cathode 20 facing the article holder 3, and can be brought into contact with and separated from the cathode evaporation surface 20S by a reciprocating drive device (not shown). In FIG. 1, the trigger electrode 25 is shown as if it penetrates the cathode 20, but instead of passing through the cathode 20, it passes through the wall around the cathode so as to be able to reciprocate ( (Not shown).

  The arc discharge power supply 24 can apply an arc discharge voltage between the cathode 20 and the anode, and trigger between the cathode 20 and the trigger electrode 25 to induce arc discharge between the cathode 20 and the anode. Wiring connection is made to the cathode 20 or the like so that a working voltage can be applied. The trigger electrode 25 is grounded via a resistor 26 so that no arc current flows.

This arc evaporation source 2 is characterized by the following points.
That is, it is provided with a magnetic field forming magnet that is disposed in the atmosphere outside the outer wall 11 of the vacuum vessel 1 and attached to the outer wall. The magnetic field forming magnet 11 is a magnet that generates magnetic field lines intersecting the evaporation surface for controlling the position of the cathode spot by vacuum arc discharge on the cathode evaporation surface 20S.

  The magnetic field forming magnet may be a permanent magnet, an electromagnet, a combination of them, or a combination of a plurality of magnets. Here, it is an annular permanent magnet M. The magnet M will be further described later.

According to the vacuum evaporation apparatus 101 demonstrated above, the thin film containing the constituent material element of the cathode 20 can be formed on the film formation object W as follows.
First, the container door (not shown) is opened, the film formation target article W is mounted on the article holder 3, and the door is closed in an airtight manner. Next, the exhaust device EX is operated to exhaust from the container 1, and the inside of the container 1 is depressurized to the film forming pressure.

  In starting the film formation, in the evaporation source 2, the trigger electrode 25 is brought into contact with the evaporation surface 20S of the cathode 20 and is continuously pulled away. As a result, a spark is generated between the electrode 25 and the cathode 20, which triggers a vacuum arc discharge between the anode (container 1) and the cathode 20. The cathode material is heated by this arc discharge, the cathode material evaporates in the α direction, and plasma including the ionized cathode material is formed in front of the cathode 20.

In this example, during film formation, a bias voltage for attracting film-forming ions is applied from the power source 6 to the holder 3 in order to improve film adhesion. Further, the holder 3 is rotated by the drive unit 5 in order to form a uniform film on each article.
When a heater (not shown) is provided in the holder 3, the article can be heated with the heater as necessary.

Thus, a film containing the constituent element of the cathode material is formed on the article W. However, in the arc evaporation source 2, the annular magnet M for forming the magnetic field provides the following advantages.
The annular magnet M is arranged so that its inner diameter is larger than the outer diameter of the cathode 20 and is fitted to the cathode 20 with its central axis aligned when viewed from a direction perpendicular to the evaporation surface 20S of the cathode 20. The first magnetic pole N is provided on one side (on the side facing the container 1) in the central axis direction, and the second magnetic pole 12S having a reverse polarity is provided on the opposite side.

FIG. 2 schematically shows the outline of the state of the magnetic field in the arc evaporation source 2.
As shown in FIG. 2, the magnetic field forming magnet M generates magnetic lines of force inclined at an acute angle θ <b> 1 to the central portion of the evaporation surface with respect to the evaporation surface 20 </ b> S at the peripheral portion of the evaporation surface 20 </ b> S of the cathode 20. In the part, a magnetic field is generated that generates magnetic lines of force inclined at an acute angle θ2 with respect to the evaporation surface peripheral portion with respect to the evaporation surface 20S.

An arc spot due to arc discharge of the cathode evaporation surface 20S in the arc evaporation source 2 has a property that it easily moves in the direction in which the magnetic lines of force are inclined on the cathode evaporation surface 20S.
Therefore, as shown in FIG. 2, the cathode spot can be moved toward the center of the evaporation surface at the peripheral portion of the cathode evaporation surface 20S by the magnetic field lines. Thus, jumping out of the cathode spot from the cathode evaporation surface 20S and wraparound to the cathode side surface ss following the cathode evaporation surface 20S can be suppressed.

  Here, according to the present evaporation source, the cathode spot is prevented from jumping out from the cathode evaporation surface 20S as described above, but the magnetic flux density for maintaining the cathode spot on the evaporation surface varies depending on the magnitude of the arc current. Since they are considered, their relationship will be described in more detail.

  FIG. 3 is a diagram schematically showing the cathode 20, the magnetic field lines B, and the like. Consider a state in which magnetic field lines intersect the evaporation surface of the cathode 20 at an angle θ. The metal ions evaporated and ionized by the heat of the cathode spot move forward from the cathode evaporation surface 20S of the evaporated substance by diffusion. At this time, the moving direction of the metal ions is opposite to the direction of the arc current. Therefore, the Lorentz force due to the surrounding magnetic field is in a direction opposite to the direction considered from the arc current.

When k is the valence of an ion, e is the elementary charge, and the initial diffusion velocity of the ion is v ₀ , the Lorentz force F ₁ due to the diffusion of the metal ion is expressed by the following equation (1).

The direction of the Lorentz force F ₁ becomes also perpendicular to the both of the diffusion direction of the magnetic lines of force and ions. In this case, the evaporation material 2 is parallel to the evaporation surface. Ions are accelerated by this force, and the acceleration is considered to be determined by the component (Bcos θ) parallel to the evaporation surface of the magnetic flux density and the ion diffusion velocity v ₀ . Here, the absolute value of v ₀ is considered to be proportional to the evaporation rate of the evaporated substance, that is, the arc current I.
Here, the Lorentz force F ₂ due to the magnetic field acts again on the ions moving in the tangential direction. Here, if the interval Δt at which arc discharge occurs is constant, the velocity v ₁ of the tangential component of ions in the following equation is proportional to the Lorentz force F ₁ , so the Lorentz force F ₂ is expressed by the following equation (2): It becomes like this.

This force F ₂ because according to a direction perpendicular to the magnetic flux B, acute direction component is generated. Thereby, it is considered that the cathode spot moves in a direction in which the evaporation surface of the evaporating substance 2 and the magnetic flux intersect at an acute angle. If the value of the intensity of the effect of moving the cathode spot in the acute angle direction is A, A is expressed by the following equation (3).

  When the arc evaporation source is used, the direction of the magnetic field lines at the outer peripheral edge of the evaporated substance is set to an acute angle inward with respect to the evaporation surface of the cathode, and the value of A is set to a certain value or more, whereby the position of the cathode spot And the cathode spot can be kept in front of the evaporant without moving to the cathode side.

Based on the above thought, whether or not the evaporation source 2 shown in FIGS. 1 and 2 is used to move (fall down) to the cathode side surface ss of the cathode spot, that is, the cathode spot is stably held on the arc evaporation surface. As to whether or not the film was formed, TiN was formed using Ti with a diameter of 84 mm and a thickness of 32 mm for the cathode 20 and N ₂ for the film forming process gas, and the effect was confirmed.

  The magnetic flux density intensity B [Gauss] at the outer peripheral edge of the cathode evaporation surface 20S, the angle formed by the magnetic field lines and the evaporation surface is θ [deg.], The arc current value is I [A], and A is given by the above equation. Table 1 shows the combinations of the values of and the results of whether or not they fall. Whether or not it falls down was determined by whether or not arc discharge was continued for 1 hour.

  Under the condition that the value of A is 70000 or more, it has been clarified that the cathode spot falls sideways, that is, the arc discharge can be maintained on the cathode evaporation surface without moving to the cathode side surface, and the film can be stably formed.

  INDUSTRIAL APPLICABILITY The present invention can be used for forming a thin film by a vacuum arc vapor deposition method that can prevent a cathode spot from moving to other than the evaporation surface, thereby preventing arc discharge from being lost, and form a thin film stably.

DESCRIPTION OF SYMBOLS 101 Vacuum deposition apparatus 1 Vacuum vessel 11 Container outer wall 2 Arc evaporation source 20 Cathode 20S Cathode evaporation surface ss Cathode side surface 21 Cathode holder 211 Space 22 Insulating member 23 Holding member 24 Arc discharge power supply 25 Trigger electrode 26 Resistance 3 Article holder W Film formation object Article (film-forming article)
4 Supporting Unit 5 Driving Unit 6 Bias Power Supply 7 Gas Introducing Unit EX Exhaust Device M Ring Magnet for Magnetic Field Formation m Magnetic Strengthening Magnet R Nonmagnetic Refractory Metal Ring B Magnetic Field Line
Lorentz force due to diffusion of F ₁ metal ions
Lorentz force by moving metal ions by F ₂ F ₁ I Arc discharge current θ, θ1, θ2 Magnetic field lines and angle of cathode evaporation surface

Claims (1)

A vacuum arc vapor deposition method in which a cathode is melted by arc discharge to evaporate a cathode material, and is disposed in the atmosphere behind the back surface of the cathode, with an annular magnet having an inner diameter larger than the outer diameter of the cathode , The magnetic lines of force at the outer edge of the cathode material intersect with the evaporation surface of the cathode at an acute angle toward the central axis of the cathode, and the angle of intersection between the magnetic field lines and the evaporation surface at the outer peripheral edge of the cathode is θ ( Degree), the magnetic flux density is B (Gauss), and the arc discharge current is I (A), and the value of A indicated by A = IB ² sin2θ is 70000 or more.

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