JP2017183091A - Cathode member and plasma device using cathode member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cathode member capable of continuing stable sparkless discharge, even if the temperature of the cathode member rises rapidly, when performing discharge ignition by using a glassy carbon in the cathode member, and to provide a plasma device using the cathode member.SOLUTION: A cathode member for use in vacuum arc discharge is composed of glassy carbon, and has an index number larger than 7.3 represented by following expression (1). F=R×d (1), where R=σ×λ/α/E (2). In the expression (1), R is heat shock resistance (10W/m), d is the diameter (mm) of a circle having an area equal to the cross-sectional area of a cross-section perpendicular to the central axis of the cathode member. In the expression (2), σ is flexural strength (MPa), λ is eat conductivity (W/mK), α is thermal expansion coefficient (/10K), and E is Young's modulus (GPa).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a negative electrode member and a plasma apparatus using the negative electrode member.

  Conventionally, a disk-like cathode member has been used as a cathode member of a plasma apparatus for forming a thin film on a substrate surface. For example, in a vacuum arc deposition apparatus using vacuum arc discharge, a material for this cathode member is used. A carbon material having a sintered structure is used (see Patent Document 1).

  However, when such a cathode member is used, a large amount of sparks (sparks) are generated during discharge to generate macro particles (carbon particles having a size of 5 nm to several μm), and these macro particles fly and adhere to the substrate. As a result, there has been a problem that the surface roughness of the thin film formed deteriorates.

  In order to suppress the occurrence of such sparks and improve the surface roughness of the thin film, the cathode member 22 protruding from the disk-shaped pedestal portion 21 as shown in FIG. 2 is used instead of the conventional disk-shaped cathode member. Is used.

  In recent years, a plasma apparatus using glassy carbon as a cathode member has been proposed (see, for example, Patent Document 2). Since this glassy carbon does not have a grain boundary, it is possible to continue the sparkless discharge to prevent the generation of macro particles and to dramatically improve the surface roughness of the thin film.

JP 11-36063 A JP 2014-133912 A

  However, when a disk-shaped cathode member is made using the glassy carbon described above, the cathode member is damaged in about one minute from the start of discharge due to a rapid temperature rise when the discharge is ignited, and sparkless discharge is caused. Sometimes it was impossible to continue.

  On the other hand, when glassy carbon was used for the columnar cathode member 22 as shown in FIG. 2, the cathode member was not damaged as in the case of the disk-like cathode member, but the discharge was ignited. The cathode member may be instantaneously pulverized due to the rapid temperature rise at the time, and similarly, the sparkless discharge may not be continued.

  Accordingly, the present invention provides a cathode member capable of continuing a stable sparkless discharge even when a rapid temperature rise occurs in the cathode member when discharge ignition is performed using glassy carbon as the cathode member, and the cathode It is an object to provide a plasma device using a member.

The invention described in claim 1
A cathode member used for vacuum arc discharge,
The cathode member is made of glassy carbon and has an index F expressed by the following formula (1) larger than 7.3.
F = R × d (1)
However, R = σ × λ / α / E (2)
In Equation (1), R is the thermal shock resistance [10 ⁹ W / m], d is the diameter [mm] of a circle having the same area as the cross-sectional area of the cross section perpendicular to the central axis of the cathode member, In the formula (2), σ is a bending strength [MPa], λ is a thermal conductivity [W / mK], α is a thermal expansion coefficient [/ 10 ⁶ K], and E is a Young's modulus [GPa].

  While the inventor has repeatedly conducted various experiments and studies on the solution of the above problems, the thermal shock resistance R and the diameter d of the cathode member are greatly related to the occurrence of pulverization due to the rapid temperature rise of the columnar cathode member. I found out.

  That is, the thermal shock resistance R is a value indicating the degree to which a thermal shock accompanying a sudden temperature rise can be withstood by a constant diameter cathode member. When R is large, pulverization is difficult even when there is a rapid temperature rise, and when thermal shock resistance R is small, pulverization is easy even when the temperature rises slowly.

The thermal shock resistance R [10 ⁹ W / m] is the bending strength σ [MPa], thermal conductivity λ [W / mK], thermal expansion coefficient α [/ 10 ⁶ K], Young's modulus E of the cathode member. [GPa] can be used to express the following equation.
R = σ × λ / α / E (2)

  On the other hand, when heat is applied to the cathode member having a certain thermal shock resistance, if the diameter d is large, it is possible to withstand the impact caused by this heat and suppress the occurrence of pulverization. It can be seen that this is related to the occurrence of pulverization associated with an increase in temperature.

  The present inventor further conducted experiments and studies on how the thermal shock resistance R and the diameter d are related to the pulverization of the cathode member. As a result, if the product (R × d) of the thermal shock resistance R and the diameter d is an index F, if F is greater than 7.3, the occurrence of pulverization due to a rapid temperature rise of the cathode member is appropriately suppressed, It was found that stable sparkless discharge can be continued.

  As a result of further experiments by the present inventors, even when the cathode member is not a columnar cathode member, when the condition that F in the above formula (1) is larger than 7.3 is satisfied, It has been found that stable sparkless discharge can be continued, and the present invention has been completed.

The invention described in claim 2
The cathode member according to claim 1, wherein the cathode member has at least one columnar portion.

  In the present invention, a cathode member having at least one columnar portion can be preferably used as the cathode member.

The invention according to claim 3
The cathode member according to claim 1 or 2, wherein the cathode member is a single bar-shaped member.

  In the case of the structure in which the cathode member is provided on the pedestal portion as shown in FIG. 2, there is a possibility that a spark is generated when an arc spot which is a cathode spot of arc discharge moves to the pedestal portion. On the other hand, in the invention of this claim, the structure of the cathode member is a single bar-like member, so that the occurrence of sparks can be prevented and stable sparkless discharge can be continued. Moreover, since it is not necessary to create a base part, it can contribute to reduction of material cost.

The invention according to claim 4
The cross-sectional shape perpendicular to the central axis of the cathode member is any one of a circular shape, an elliptical shape, a polygonal shape, and a polygonal shape with rounded corners. The cathode member according to claim 1.

  By using a cathode member having these shapes, stable sparkless discharge can be continued.

The invention described in claim 5
The cathode member according to any one of claims 1 to 4, wherein the cathode member has a columnar shape or a substantially columnar shape.

  When a columnar or substantially columnar cathode member is used, a particularly stable sparkless discharge can be continued, which is preferable.

The invention described in claim 6
6. The cathode member according to claim 1, wherein a surface roughness Ra of the cathode member is smaller than 15.4 μm.

  In the case of a cathode member having a small surface roughness, it is possible to prevent the arc spot from moving to a position other than the cathode member during discharge, and to continue stable sparkless discharge.

The invention described in claim 7
The glassy carbon forming the cathode member is any one of glassy carbon, amorphous carbon, amorphous carbon, amorphous carbon, amorphous carbon, and non-graphitized carbon. 6. The cathode member according to any one of 6 above.

  By using these carbon materials as the glassy carbon constituting the cathode member, the sparkless discharge can be continued more stably.

The invention according to claim 8 provides:
A vacuum chamber, and a cathode member attached in the vacuum chamber,
In the plasma device, the cathode member is made of glassy carbon, and an index F expressed by the following formula (1) is larger than 7.3.
F = R × d (1)
However, R = σ × λ / α / E (2)
In Equation (1), R is the thermal shock resistance [10 ⁹ W / m], d is the diameter [mm] of a circle having the same area as the cross-sectional area of the cross section perpendicular to the central axis of the cathode member, In the formula (2), σ is a bending strength [MPa], λ is a thermal conductivity [W / mK], α is a thermal expansion coefficient [/ 10 ⁶ K], and E is a Young's modulus [GPa].

  As described above, when the cathode member is made of glassy carbon and the index F (= R × d) is larger than 7.3, stable sparkless discharge can be continued.

The invention according to claim 9 is:
The plasma device according to claim 8, wherein the cathode member has at least one columnar portion.

  As described above, in the present invention, a cathode member having at least one columnar portion can be preferably used as the cathode member.

The invention according to claim 10 is:
The plasma apparatus according to claim 8 or 9, wherein the discharge current I is controlled so that the discharge current I to the cathode member satisfies the following formula (3).
I <2.73 × F (3)

  When the inventor conducted an experiment, it was found that even when a cathode member having an index F larger than 7.3 was used, if the discharge current I was too large, stable sparkless discharge could not be continued.

Thus, when an appropriate discharge current I that can continue a stable sparkless discharge was obtained and further experiments were conducted, it was found that the following equation (3) should be satisfied.
I <2.73 × F (3)

The invention according to claim 11
The plasma device according to any one of claims 8 to 10, wherein the cathode member is a single bar-shaped member.

  As described above, by using a single bar-like member as the cathode member, it is possible to prevent the occurrence of sparks and continue stable sparkless discharge.

The invention according to claim 12
The cross-sectional shape perpendicular to the central axis of the cathode member is any one of a circular shape, an elliptical shape, a polygonal shape, and a polygonal shape with rounded corners. The plasma apparatus according to claim 1.

  As described above, stable sparkless discharge can be continued by using the cathode member having these shapes.

The invention according to claim 13
The plasma device according to any one of claims 8 to 12, wherein the cathode member has a columnar shape or a substantially columnar shape.

  As described above, when the shape of the cathode member is a columnar shape or a substantially columnar shape, it is preferable because a more stable sparkless discharge can be continued.

The invention according to claim 14
The plasma apparatus according to any one of claims 8 to 13, wherein the plasma apparatus is a vacuum arc vapor deposition apparatus including a holding member for holding a base material disposed in the vacuum chamber. .

  By holding the substrate in the vacuum chamber of the vacuum arc vapor deposition apparatus, stable film formation is possible during vacuum arc vapor deposition, and it can be preferably used as a plasma apparatus for forming a carbon film on the substrate surface.

The invention according to claim 15 is:
15. The plasma apparatus according to claim 14, further comprising magnetic field generating means for generating a magnetic field around the cathode member so that the arc spot moves spirally on the side surface of the cathode member.

  A uniform thin film can be formed on the surface of the substrate disposed facing the cathode member by moving the arc spot during discharge in a spiral shape on the side surface of the cathode member by the magnetic field generating means.

  According to the present invention, when the discharge is ignited using glassy carbon as the cathode member, the cathode member capable of continuing a stable sparkless discharge even if a rapid temperature rise occurs in the cathode member and the cathode A plasma device using the member can be provided.

It is the schematic which shows the structure of the plasma apparatus which concerns on one embodiment of this invention. It is a perspective view of a cathode member and a base part. It is a figure which shows distribution of the result in Experiment 1-Experiment 4. It is a figure which shows the area | region where the sparkless discharge continued in FIG.

  Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, first, the basic configuration of the plasma apparatus is described, then the cathode member that is a characteristic part of the present invention is described, and further, the plasma apparatus provided with such a cathode member is described. The film formation performed using these will be described. Finally, the main experiments conducted by the present inventor up to the present invention, such as an experiment specifying that the index F when the cathode member is not pulverized even if a rapid temperature rise occurs is greater than 7.3. The results will be described.

1. Plasma Device First, the basic configuration of the plasma device will be described. FIG. 1 is a schematic diagram showing the configuration of the plasma apparatus according to the present embodiment. In the present embodiment, a vacuum arc deposition apparatus that forms a thin film on the surface of the substrate using vacuum arc discharge is used as the plasma apparatus.

  As shown in FIG. 1, this plasma apparatus 100 has the same configuration as the conventional plasma apparatus except for the cathode member 22. Specifically, the plasma apparatus 100 includes a vacuum chamber 1, a cathode member 22, a pedestal portion 21, a backing plate 4, a holding member 3, a power source 7 and a power source 8, and a magnet 9. In addition, 5 in FIG. 1 is a plasma and 6 is a base material.

(1) Vacuum chamber The vacuum chamber 1 is connected to the ground node GND. Although not shown, the vacuum chamber 1 is provided with an exhaust port, and the vacuum chamber 1 can be evacuated to a predetermined degree of vacuum by an exhaust system such as a turbo molecular pump or a rotary pump.

(2) Cathode member In this Embodiment, the cathode member 22 is attached to the disk shaped base part 21. As shown in FIG. The pedestal portion 21 is installed in a state insulated from the vacuum chamber 1 through the backing plate 4 and is made of a carbon material.

  The pedestal portion 21 is, for example, a substantially disk-shaped member, and one surface is attached to the backing plate 4 and the other surface is directed to the base material 6 (see FIG. 1). Hereinafter, for convenience of explanation, the surface of the pedestal portion 21 facing the base material 6 is referred to as the upper surface of the pedestal portion 21.

  The cathode member 22 is a cylindrical member whose cross section perpendicular to the central axis is, for example, a circle, and protrudes from the upper surface of the pedestal portion 21 toward the base material 6.

(3) Holding Member The holding member 3 is disposed so as to face the cathode member 22 in the vacuum chamber 1 and is configured to hold a plurality of base materials 6. The holding member 3 is rotatably attached, and a thin film can be uniformly formed on each surface of the substrate 6 by rotating the holding member 3 during plasma irradiation.

(4) Magnet As shown in FIG. 1, in the present embodiment, a magnet 9 as a magnetic field generating means is provided outside the vacuum chamber 1. The magnet 9 is disposed in the vicinity of the back surface of the pedestal portion 21 and is disposed so as to generate a magnetic field directed in the axial direction and the radial direction of the cathode member 22. Thereby, the side of the cathode member 22 can be moved spirally in the arc spot during arc discharge.

(5) Power source The power source 7 is connected to the holding member 3 and applies a negative voltage (bias voltage) to the base material 6 via the holding member 3. The power supply 7 is also connected to the ground node GND. On the other hand, the power source 8 is connected to the backing plate 4 and applies a negative voltage to the cathode member 22 via the backing plate 4 and the pedestal portion 21. Similarly to the power supply 7, the power supply 8 is connected to the ground node GND.

(6) Trigger electrode Although not shown, the plasma device 100 is provided with a trigger electrode. By bringing the trigger electrode into contact with the cathode member 22, arc discharge is caused between the cathode member 22 and the inner wall of the chamber 1. The carbon material of the cathode member 22 is evaporated, and the carbon material can be vapor-deposited on the base material 21 disposed facing the cathode member 22.

(7) Gas supply means The plasma apparatus 100 may further be provided with a gas supply means (not shown) for supplying a gas having a predetermined function into the vacuum chamber 1. And rare gases such as argon, nitrogen gas, diborane, phosphine, and the like.

2. Next, the cathode member that is a characteristic part of the present invention will be described.

(1) Material of Cathode Member In the cathode member of the present invention, as described above, the cathode member 22 is formed of glassy carbon that is structurally free of grain boundaries. This glassy carbon is produced, for example, by baking and carbonizing a thermosetting resin such as a phenol resin.

  Examples of such glassy carbon include glassy carbon, amorphous carbon, amorphous carbon, amorphous carbon, amorphous carbon, non-graphitized carbon, and the like, specifically, manufactured by Nisshinbo Chemical Co., Ltd. Examples thereof include glassy carbon and glassy carbon manufactured by Tokai Carbon.

  In the present embodiment, since the cathode member 22 is formed from glassy carbon having no grain boundary, it is possible to perform a sparkless discharge in which no spark is generated during discharge, and a film formation surface due to the generation of macro particles. The deterioration of the roughness can be prevented.

(2) Index F of Cathode Member The plasma apparatus according to the present embodiment is different from the conventional one in that a cathode member having an index F shown below is larger than a predetermined value as the cathode member 22.

Specifically, in the plasma apparatus according to the present embodiment, a cathode member made of glassy carbon and having an index F expressed by the following formula (1) larger than 7.3 is used.
F = R × d (1)

  As described above, sparkless discharge can be performed by using the cathode member 22 formed of glassy carbon having no grain boundary. However, such a cathode member is pulverized when a rapid temperature rise occurs. There is a fear.

  However, in the present embodiment, since the cathode member 22 is configured so that the index F in the above formula (1) is larger than 7.3 as a result of an experiment described later, it is glassy. Despite the use of the cathode member 22 formed of carbon, it is possible to appropriately suppress the occurrence of pulverization of the cathode member 22 due to a rapid temperature rise and to continue stable sparkless discharge.

(A) Thermal shock resistance R As described above, the thermal shock resistance R in the formula (1) is obtained when a thermal shock accompanying a sudden temperature rise is applied to a cathode member having a constant diameter. It is a value that indicates the degree to which it can withstand the impact caused by the above. When the thermal shock resistance R is large, it is difficult to pulverize even if there is a rapid temperature rise, and when the thermal shock resistance R is small, the temperature rises slowly. However, it is easy to grind.

  The thermal shock resistance R is preferably a large value. Specifically, it is preferably 7.9 or more, and more preferably 12.2 or more. In addition, the maximum value of the thermal shock resistance R of glassy carbon is about 20.7.

(B) Diameter d On the other hand, the diameter d in the formula (1) is also required to have a certain size. That is, if the diameter d is too small, the electrical resistance of the cathode member 22 increases, so the amount of heat generation increases and the thermal shock increases, and the volume per unit length of the cathode member 22 decreases. Crushing tends to occur. For this reason, not only the thermal shock resistance R described above, but also the diameter d of the cathode member is related to the occurrence of pulverization accompanying a rapid temperature rise as described above.

  This diameter d is usually preferably 3 to 10 mm. When the diameter d is larger than 10 mm, the material efficiency is deteriorated, and the arc spot may not move during the arc discharge and the cathode member 22 may be broken. The length of the cathode member 22 in the axial direction is preferably adjusted according to, for example, the duration of arc discharge, and is preferably set to about 10 mm.

(C) About the index F The product (R × d) of the thermal shock resistance R and the diameter d is taken as the index F, and the cathode member having an appropriate value for this index F is Stable sparkless discharge can be continued without crushing.

  This index F needs to be a value larger than 7.3 as a result of an experiment described later. Thus, if the cathode member has an index F larger than 7.3, if the discharge current (arc current) I is small, it will not be crushed during the arc discharge, and a sufficiently stable sparkless discharge will be continued. Can do. As an example of a specific index F, when the diameter d is 10 mm, the maximum value of the thermal shock resistance R is about 20.7 as described above, so the maximum value of the index F is about 207.

(3) Relationship between index F and arc current I As described above, stable sparkless discharge can be continued by using a cathode member having an index F larger than 7.3. However, even when a cathode member having an index F larger than 7.3 is used, if the arc current I to the cathode member is too large, stable sparkless discharge may not be continued. For this reason, it is preferable that the plasma apparatus 100 includes a control unit that controls the arc current I in accordance with the value of the index F of the cathode member 22 being used.

At this time, it is preferable that the control unit controls the discharge current I so as to satisfy the condition shown in the following formula (3). In the equation (3), I is the discharge current (A), and F is the index F defined by the above equation (1). Further, 2.73 in the formula (3) is a constant found by the inventor through experiments described later.
I <2.73 × F (3)

  By controlling the arc current I in accordance with the value of the index F of the cathode member 22 so as to satisfy this equation (3), the cathode member 22 is reliably prevented from being crushed during arc discharge, and stable sparkless. Discharging can be continued.

(4) Other Configurations of Cathode Member In the above-described embodiment, the case where one columnar cathode member 22 is provided has been described, but the present invention is not limited to this. The cathode member preferably has at least one columnar portion, and may have two or more.

  In addition, the cathode member preferably has a circular, elliptical, polygonal, or polygonal shape with rounded corners in a cross-sectional shape perpendicular to the central axis. When the cathode member 22 is not cylindrical, the diameter d in the formula (1) is the area of a cross section perpendicular to the central axis of the cathode member, and the diameter of a circle having the same area as the obtained cross section area is obtained. It is obtained by calculating.

  Further, when the thickness of the cathode member varies depending on the axial direction, the average value of the areas of the respective cross sections in the axial direction is obtained, and the diameter of a circle having the same area as the average value of the area is calculated. The diameter is used as the diameter d in the formula (1).

  Further, the surface roughness (arithmetic average roughness Ra) of the cathode member 22 is preferably smaller than 15.4 μm, more preferably 8.6 μm or less. By using the cathode member 22 having such a small surface roughness, it is possible to prevent the arc spot from moving to a part other than the cathode member 22 during discharge, and to continue stable sparkless discharge.

3. Film Formation Performed Using Plasma Apparatus According to this Embodiment Next, a film forming procedure performed using plasma apparatus 100 configured as described above will be described.

  First, the pedestal 21 is attached to the backing plate 4 and the cathode member 22 is attached to the pedestal 21. At this time, the cathode member 22 is made of glassy carbon having an index F larger than 7.3 as described above.

  Next, after holding the substrate 6 with the holding member 3, the inside of the vacuum chamber 1 is reduced to a desired pressure, and a negative voltage (for example, −10 V to −300 V) is applied from the power source 7 to the substrate 6. Further, in the present embodiment, when a negative voltage is applied from the power supply 8 to the cathode member 22, the arc current I to the cathode member 22 based on the above equation (3) “I <2.73 × F”. Is controlled to be an appropriate value for the index F.

  Then, the trigger electrode and the cathode member 22 are brought into contact with each other to cause arc discharge between the inner wall of the chamber 1.

  When arc discharge occurs, an arc spot appears on the cathode member 22, and glassy carbon constituting the cathode member 22 evaporates to generate plasma 5. As a result, a carbon thin film can be formed on the surface of the base material 6 disposed to face the cathode member 22.

  At this time, since the index F of the cathode member 22 is made larger than 7.3 and the arc current I is controlled so as to satisfy the condition of “I <2.73 × F”, a rapid temperature due to arc discharge is increased. Even if the rise occurs in the cathode member 22, it is not pulverized by thermal shock as in the prior art. As a result, stable sparkless discharge can be continued and a suitable carbon thin film can be formed on the surface of the substrate.

4). Experimental Example Hereinafter, an experiment conducted by the present inventor until reaching the present invention will be described. As described above, based on the results of the following experiment, the present inventor has determined whether or not the index member F, which is the product of the thermal shock resistance R and the diameter d (R × d), crushes the cathode member during arc discharge. When this index F is larger than 7.3, it was confirmed that if the arc current I is small, it is not pulverized during discharge and stable sparkless discharge can be continued. .

(1) Experiment 1
In examining the parameter of whether or not the cathode member is pulverized during arc discharge, the present inventor firstly, in order to examine glassy carbon that can withstand a rapid temperature rise during arc discharge, Vacuum arc discharge was performed using a plurality of glassy carbons having different resistances R.

Specifically, vacuum arc discharge was performed using the plasma apparatus 100 shown in FIG. In this test, the vacuum chamber 1 is evacuated to 9.9 × 10 ⁻³ Pa by an exhaust device (not shown) such as a rotary pump and a turbo molecular pump, and a discharge point is generated so that an arc spot is generated in the cathode member 22. Arcing was performed and the discharge status was confirmed.

  Then, a cathode member 22 having a cylindrical shape (diameter d is 3 mm, height is 10 mm) was used. In addition, the magnet 9 was arranged to form a magnetic field in the direction of the base material 6 around the tip of the cathode member 22. When the magnetic field at this time was measured using a gauss meter (410-SCT type, manufactured by Lake Shore), the magnetic field in the axial direction of the cathode member 22 was 87 Gauss, and the magnetic field in the radial direction was 16 Gauss. Note that a bias voltage of −50 V was applied to the substrate, and the discharge time was set to 40 sec.

  In Experiment 1, as shown in Table 1 below, four types of cathode members 22 having different thermal shock resistance R in Experimental Examples 1 to 4 were used. In Table 1, the bending strength σ, the thermal conductivity λ, the thermal expansion coefficient α, and the Young's modulus E are all values at about 20 ° C. to 30 ° C. The bending strength σ is the bending strength.

  Table 2 summarizes the experimental results of Experimental Example 1 to Experimental Example 4 described above. In this experiment, the arc current was set to 80A.

  “Yes” in Table 2 indicates that stable sparkless discharge continued for 40 seconds, and “No” indicates that the cathode member 22 was crushed almost instantaneously (within about 1 second) after the discharge was ignited. . In Experiment 1, the same experiment was repeated three times for each experimental example, but the same result was obtained three times.

  From Table 2, in the experimental example 1 in which the cathode member was crushed, the thermal shock resistance R was as low as 7.9, so the pulverization could not withstand the temperature rise when the arc was set to 80A and the discharge was ignited. It is thought that. On the other hand, in Experimental Example 2 to Experimental Example 4 in which the thermal shock resistance R is larger than 7.9, it can be considered that the thermal shock due to a rapid temperature rise can be withstood and stable sparkless discharge can be continued.

  From this result, when the diameter d of the cathode member 22 is the same size, the cathode member 22 is stabilized without being pulverized by using glassy carbon having a thermal shock resistance higher than a certain value for the cathode member 22. It was confirmed that sparkless discharge was possible.

(2) Experiment 2
Next, the inventor conducted an experiment to examine the influence of the thickness of the cathode member 22 as to whether or not the cathode member 22 during discharge is pulverized.

  In Experiment 2, the glassy carbon of Example 2 (thermal shock resistance R = 12.2) in which the stable sparkless discharge was continued for 40 seconds in Experiment 1, and the diameter d of the cathode member 22 is shown in Table 3. A vacuum arc discharge was performed. Other conditions were set to the same conditions as in Experiment 1, and the discharge test was repeated three times for each experimental example as in Experiment 1. As a result, the same result was obtained three times. The experimental results are summarized in Table 3.

  From Table 3, when performing arc discharge with an arc current of 80 A, when glassy carbon having a thermal shock resistance R of 12.2 is used, Experimental Example 7 to Experiment in which the diameter d of the cathode member 22 is 3 mm or more In Example 9, it was confirmed that stable sparkless discharge could be continued. On the other hand, in the case of Experimental Example 5 to Experimental Example 6 in which the diameter of the cathode member 22 was 2 mm or less, the cathode member 22 was pulverized instantaneously after the discharge was ignited. From this, it was confirmed that even when the thermal shock resistance R is the same, if the diameter of the cathode member 22 is small, the pulverization of the cathode member 22 cannot be prevented appropriately.

  This is considered to be because when the diameter of the cathode member 22 is small, the electrical resistance of the cathode member 22 increases and the amount of heat generation increases. Further, it is considered that the cathode member 22 having a small diameter has a small volume per unit length, and the temperature rise when the discharge is ignited is further abrupt and the mechanical strength is also reduced.

  Therefore, the present inventor cannot prevent the cathode member 22 from being crushed only by the large thermal shock resistance R of glassy carbon, and the cathode member 22 cannot be crushed unless the diameter d is also a certain large value. Therefore, it is considered that the index F considering both the thermal shock resistance R and the diameter d can be a parameter for determining whether or not the cathode member 22 is crushed during arc discharge.

(3) Experiment 3 and Experiment 4
Therefore, the present inventor conducted an experiment to obtain data on the thermal shock resistance R and the diameter d by further changing the arc current I and the diameter d.

  In Experiment 3 and Experiment 4, vacuum arc discharge was performed under the same conditions as in Experiment 2 except that the arc current during arc discharge was changed. Specifically, in Experiment 3, the arc current was set to 40A, and in Experiment 4, it was set to 100A. The results of Experiment 3 with the arc current set to 40 A are shown in Table 4, and the results of Experiment 4 with the arc current set to 100 A are shown in Table 5.

  From Table 3 to Table 5, comparing Experimental Example 6, Experimental Example 11, and Experimental Example 16 in which the diameter d of the cathode member 22 was 2 mm, the cathode member 22 was not crushed in Experimental Example 11 in which the arc current was set to 40A. However, in Experimental Examples 6 and 16, the cathode member 22 was pulverized after the ignition of the discharge. This is considered to be because when the arc current is large, the amount of heat generation increases, and the temperature rises rapidly when the discharge is ignited.

  From this result, it is possible to confirm that a stable sparkless discharge can be realized by setting the arc current to a certain small value and using a cathode member having a large thermal shock resistance R and a certain large diameter d. It was.

(4) Regarding the relationship between the index F and the discharge current I Next, the index F (= R × d) is obtained based on the thermal shock resistance R and the diameter d acquired in the above experiments 1 to 4, and this index F The relationship between (R × d) and arc current was examined. The created graph is shown in FIG. In FIG. 3, the horizontal axis represents the index F (thermal shock resistance R × diameter d), and the vertical axis represents the arc current (A). In FIG. 3, “◯” and “X” mean the following.
○: When stable sparkless discharge continues for 40 seconds.
X: When the cathode member 22 pulverizes almost instantaneously (within about 1 sec) after starting.

  As a result of plotting the results of Experiment 1 to Experiment 4 on the graph as shown in FIG. 3, there are 2 areas where stable sparkless discharge can be continued and areas where the sparkless discharge cannot be continued, as shown in FIG. It was found that there was a clear division.

  The boundary between the two regions is considered to be a function (monotonically increasing function) in which the value on the vertical axis increases monotonously as the value on the horizontal axis increases.

When the cathode member does not exist (diameter d = 0), the volume of the cathode member 22 becomes 0. Therefore, if the calorific value does not converge to 0, the cathode member is caused by a rapid temperature rise when the discharge is ignited. , The arc current value I must be set to zero. Specifically, the calorific value and the electric resistance of the cathode member and Rc in the case of d = 0 is the RCI ^2, in order to be Rc → ∞, for the RCI ² → 0 is ^{I 2} → 0 That is, I needs to converge to zero. Therefore, the function f indicating the boundary between the two regions is a monotonically increasing function passing through the origin (0, 0) when I ≧ 0.

Based on the above knowledge, the inventor considered that the function f representing the boundary can be expressed by the following equation (4).
I = f (F) = κ · F (4)
In Expression (4), I is an arc current (A), F is an index defined by F = R × d described in Expression (1), and κ is a constant.

Then, as a function f satisfying such a condition, it was determined that κ = 2.73 as shown in the following equation (5) based on FIG.
f (F) = 2.73 · F (5)

In FIG. 4, the right side of the boundary represented by the equation (5) is a region where stable sparkless discharge can be continued, and this region can be represented by the following equation (3).
I <2.73 · F (3)

  Next, when examining the minimum value of the index F, the present inventor pays attention to the minimum necessary current value at which arc discharge is established in a general plasma apparatus, and the arc current having the minimum necessary current value is considered. In the case of I, the value of F that can satisfy the expression (3) was considered to be a minimum value that can continue stable sparkless discharge without crushing during discharge.

  Then, using a columnar cathode member having a thermal shock resistance R = 12.2 and a diameter of 3 mm, the value of the arc current I is changed to 10A, 15A, 20A, 30A, 40A, 80A, 100A, In this case, it was verified for 10 seconds whether or not the discharge was established. As a result, no discharge occurred when the value of the arc current I was 10 A or 15 A, but a sparkless discharge occurred when the arc current I was 20 A or more.

  Therefore, when the current value is set to 20 A or more, sparkless discharge is surely established, and the value of the index F in the case of I = 20 A is calculated from FIG. 4. As a result, the index F of the cathode member is calculated from 7.3. It was also found that if the arc current is small, stable sparkless discharge can be sufficiently performed without crushing during discharge.

  As described above, based on the results of Experiments 1 to 4 described above, the present inventors have a large relationship with the thermal shock resistance R and the diameter d of the cathode member in the occurrence of pulverization due to the rapid temperature rise of the cathode member. If the product (R × d) of the thermal shock resistance R and the diameter d is an index F, and F is larger than 7.3, the occurrence of pulverization due to a rapid temperature rise of the cathode member is appropriate. It was confirmed that stable sparkless discharge could be continued and the present invention could be completed.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above-described embodiments within the same and equivalent scope as the present invention.

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 3 Holding member 4 Backing plate 5 Plasma 6 Base material 7, 8 Power supply 9 Magnet 21 Base part 22 Cathode member 100 Plasma apparatus d Diameter of cathode member

Claims (15)

A cathode member used for vacuum arc discharge,
A cathode member comprising glassy carbon and having an index F expressed by the following formula (1) larger than 7.3.
F = R × d (1)
However, R = σ × λ / α / E (2)
In Equation (1), R is the thermal shock resistance [10 ⁹ W / m], d is the diameter [mm] of a circle having the same area as the cross-sectional area of the cross section perpendicular to the central axis of the cathode member, In the formula (2), σ is a bending strength [MPa], λ is a thermal conductivity [W / mK], α is a thermal expansion coefficient [/ 10 ⁶ K], and E is a Young's modulus [GPa].   The cathode member according to claim 1, wherein the cathode member has at least one columnar portion.   The cathode member according to claim 1, wherein the cathode member is a single bar-shaped member.   The cross-sectional shape perpendicular to the central axis of the cathode member is any one of a circular shape, an elliptical shape, a polygonal shape, and a polygonal shape with rounded corners. The cathode member according to claim 1.   The cathode member according to claim 1, wherein the cathode member has a columnar shape or a substantially columnar shape.   6. The cathode member according to claim 1, wherein the surface roughness Ra of the cathode member is less than 15.4 μm.   The glassy carbon forming the cathode member is any one of glassy carbon, amorphous carbon, amorphous carbon, amorphous carbon, amorphous carbon, and non-graphitized carbon. The cathode member according to any one of 6. A vacuum chamber, and a cathode member attached in the vacuum chamber,
The said cathode member consists of glassy carbon, and the index | exponent F represented by following formula (1) is larger than 7.3, The plasma apparatus characterized by the above-mentioned.
F = R × d (1)
However, R = σ × λ / α / E (2)
In Equation (1), R is the thermal shock resistance [10 ⁹ W / m], d is the diameter [mm] of a circle having the same area as the cross-sectional area of the cross section perpendicular to the central axis of the cathode member, In the formula (2), σ is a bending strength [MPa], λ is a thermal conductivity [W / mK], α is a thermal expansion coefficient [/ 10 ⁶ K], and E is a Young's modulus [GPa].   9. The plasma apparatus according to claim 8, wherein the cathode member has at least one columnar portion. The plasma apparatus according to claim 8 or 9, wherein the discharge current I is controlled so that the discharge current I to the cathode member satisfies the following formula (3).
I <2.73 × F (3)   11. The plasma apparatus according to claim 8, wherein the cathode member is a single bar-shaped member.   The cross-sectional shape perpendicular to the central axis of the cathode member is any one of a circular shape, an elliptical shape, a polygonal shape, and a polygonal shape with rounded corners. 2. The plasma apparatus according to claim 1.   The plasma device according to any one of claims 8 to 12, wherein the negative electrode member has a cylindrical shape or a substantially cylindrical shape.   The plasma apparatus according to any one of claims 8 to 13, wherein the plasma apparatus is a vacuum arc vapor deposition apparatus including a holding member for holding a base material disposed in the vacuum chamber.   15. The plasma apparatus according to claim 14, further comprising magnetic field generating means for generating a magnetic field around the cathode member so that the arc spot moves spirally on the side surface of the cathode member.

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