JPH0841632A - Small thermionic vacuum arc evaporation source - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a small evaporation source that can form a metal film with high adhesion strength over a wide range at high speed and can perform stable film formation with stable arc plasma. PROBLEM TO BE SOLVED: To provide an evaporation source capable of performing vapor deposition [Configuration] Evaporated metal material 5 evaporated from thermionic beam source 1
In the thermionic vacuum arc evaporation source provided with arc plasma conversion means for converting the vapor of the above into arc plasma, the thermoelectron beam source is used for controlling the temperature of the hot cathode 7, the Wehnelt electrode 10, and the hot cathode to be constant. The hot-cathode current source 8 and the electrode power source 11 for applying a negative voltage to the Wehnelt electrode to the hot-cathode, and the vaporized metal material supply device 4 includes a continuous supply mechanism 15 for continuously supplying the vaporized metal material having a small heat capacity. , A variable constant current source 12d for increasing the current at a speed programmed according to the heat capacity of the evaporated metal material by controlling power source 12 for accelerating electrons by keeping the thermionic beam source at a negative high voltage with respect to the supply device
And ballast load 12e

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention heats and evaporates a metal material in a vacuum container by an electron beam and ionizes a part of the metal material to form a thin film of the metal material on a workpiece prepared in the container. A small thermionic vacuum arc evaporation source.

[0002]

2. Description of the Related Art Conventionally, for metal deposition in a vacuum, a heat transfer evaporation source for directly heating and evaporating a crucible in an electric furnace or an electron beam from an electron beam source is accelerated by a voltage from a high voltage power source. An electron beam evaporation source for irradiating and heating an evaporated metal material in a crucible is known. In order to increase the adhesion of the metal vapor deposition film to the work, ion plating is used to accelerate metal ions in the plasma and irradiate the work surface. The deposition rate does not increase because it is lower than the metal evaporation density from the source.

A technique of using an arc plasma of metal vapor as a metal evaporation source which gives a high metal vapor pressure and a high ion density is disclosed in US Pat. No. 3,783,231. At the cold cathode, an arc spot formed by high temperature molten metal on the surface supplies metal vapor and high density electrons. The electrons from the thermionic cathode are accelerated and converged to irradiate the anode, which is a metal vapor source,
A technique for producing a more stable arc plasma and using it as a metal evaporation source is described in French Patent No. 1,496,697.
Are disclosed in the specification. Further, a hot cathode vacuum arc metal evaporation source miniaturized by focusing electrons from the hot cathode using a Wehnelt electrode is disclosed in Rev. Rou
m. Phys. 28, 10, 907 (1981). Disclosed by Musa et al.

As plasma for ion plating,
The evaporated metal material in the crucible heated by the electron beam,
A technique of using an arc plasma obtained by arcing with a current from another arc power source is disclosed in Hiroshi Kibe et al. (Summary of Surface Technology Association 89 Abstract, 218, 1994). This is the same as the above-mentioned G.1 in which the electron beam power source and the arc power source are shared. It is considered to have the same structure as the technology taught by Musa, but the latter is more suitable for miniaturization.

[0005]

The conventional evaporation source using the above-mentioned crucible has a drawback in that the adhesion strength of the metal vapor deposition film is weak, and an evaporation source of the type that ionizes metal vapor using an electron beam is not available. There is a drawback that the film speed is slow. Further, not only the evaporation amount of each evaporation source changes with time, but the evaporation source using arc plasma has a disadvantage that it lacks stability when the arc is ignited and when it is stationary. Further, since the conventional evaporation source is relatively large and cannot be freely moved during film formation, it has been desired to provide a small and movable evaporation source.

The present invention provides a small evaporation source capable of forming a metal film having a high adhesion strength over a wide range at high speed and performing stable film formation with stable arc plasma, and vapor deposition by changing the position and direction. The object is to provide an evaporation source capable of performing the above.

[0007]

According to the present invention, a thermoelectron beam source, a vaporized metal material supply device, and a thermoelectron beam source are maintained at a negative high voltage with respect to the vaporized metal material supply device to accelerate electrons. A thermoelectron equipped with a control power source and an arc plasmaization means for converting the vapor of the vaporized metal material of the vaporized metal material supply device vaporized by the irradiation of the electron beam from the thermoelectron beam source into arc plasma to ionize a part thereof. In the vacuum arc evaporation source, the thermionic beam source is a hot cathode, a Wehnelt electrode, a hot cathode current source for controlling the temperature of the hot cathode constant, and the Wehnelt electrode with respect to the hot cathode. The vaporized metal material supply device is provided with a continuous supply mechanism for continuously supplying the vaporized metal material having a small heat capacity to a position close to the thermionic beam source. Is the evaporated metal By constituted by a programmed variable constant current source to increase the current speed and ballast load to combine the arc plasma function depending on the heat capacity, and so as to achieve the first objective described above. The thermionic beam source includes a hot cathode, a Wehnelt electrode, an electron extraction electrode, a hot cathode current source for controlling the temperature of the hot cathode to a constant value, and a negative voltage with respect to the hot cathode to the Wehnelt electrode. The electron extraction electrode is provided with an electrode power source for giving a positive voltage to the hot cathode, or the hot cathode, the Wehnelt electrode, the electron extraction electrode, the deflection electrode, and the hot cathode. Hot cathode current source for controlling the temperature of the hot cathode, and an electrode for applying a negative voltage to the Wehnelt electrode and the deflection electrode to the hot cathode and a positive voltage to the electron extraction electrode to the hot cathode. And a robot arm is provided in the vacuum container of the thermionic vacuum arc evaporation source, and the thermoelectron beam source and the vaporized metal material supply device are mounted at the tip of the robot arm. The latter purpose is achieved.

[0008]

The evaporation source of the present invention is prepared in a vacuum, a negative voltage is applied to the Wehnelt electrode with respect to the hot cathode by an electrode power supply, and a control power supply is provided between the thermionic beam source and the evaporation metal material supply device. When a high negative voltage is applied and the hot cathode of the thermionic beam source is energized, the hot electron beam generated from the hot cathode is converged by the electrostatic field created by the hot cathode or electron extraction electrode and Wehnelt electrode, and is electrically grounded. Accelerated irradiation is performed toward the tip of the vaporized metal material of the vaporized metal material supply device at the potential. As a result, the vaporized metal material is heated, and when the electron beam heating exceeds a certain critical value (critical electron heating), vapor of the metal material is generated and the metal atoms are ionized to generate arc discharge. The heat generated by the arc discharge heats the tip of the vaporized metal material to enhance the vaporization of the metal material. The vapor stream containing such ions firmly adheres to the surface of the work by the chemical action of the ions. Since the evaporated metal material is formed so as to have a small heat capacity, its evaporation consumption is relatively fast,
In order to compensate for this, the continuous feeding device continuously feeds so that its tip is present at a predetermined position. Since the control power supply is composed of a variable constant current source that raises the current at a programmed speed according to the heat capacity of the evaporated metal material and a ballast load, arc discharge is stabilized and the control power supply accelerates electrons. Since it also has an arc plasma conversion function, the equipment for arc discharge is unnecessary and the evaporation source can be made compact.

If the thermoelectron beam source and the vaporized metal material supply device are provided in the vacuum container of the thermionic vacuum arc evaporation source, vapor deposition becomes possible. Therefore, a robot arm provided with these in the vacuum container. It is possible to form a metal film by applying a vapor flow to the work from any position.

[0010]

Embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, reference numeral 1 denotes a thermionic beam source provided inside a vacuum container 2 of a thermionic vacuum arc evaporation source that is evacuated to a vacuum, and a thermionic beam 3 emitted from the thermionic beam source 1 is The tip of the vaporized metal material 5 of the vaporized metal material supply device 4 is irradiated, and a part of the metal vapor evaporated from the vaporized metal material 5 is ionized by the arc plasma and is made of metal or plastic prepared in the vacuum container 1. A metal film is formed by adhering to the film forming surface of the work 6.

The thermionic beam source 1 comprises a cathode stem 7a,
A hot cathode 7 heated to an incandescent state by energization from a hot cathode current source 8 of direct current outside the vacuum container 2 to a cathode filament 7b of a tungsten wire stretched between 7a and a heat emitted from the cathode filament 7b. A cylindrical electron extraction electrode 9 for extracting electrons, and a cylindrical Wehnelt electrode 10 for converging the extracted thermoelectrons into a thermoelectron beam 3 by converging by an electrostatic field.
The thermoelectron beam 3 is electrically applied to the tip of the vaporized metal material 5 which is grounded to the vacuum container 2. For this irradiation, in addition to the cathode current source 8, a DC electrode power source 11
And a DC control power source 12 are provided, and the hot cathode current source 8
The neutral terminal 8a and the electrode reference terminal 11a of the electrode power supply 11 are connected to the negative high voltage terminal 12a of the control power supply 12, and
The ground terminal 12b of the control power supply 12 is connected to the vacuum container 2, the electron extraction electrode 9 is connected to the positive terminal 11b of the electrode power supply 11, and a slightly positive voltage is applied to the electrode reference terminal 11a to turn the Wehnelt electrode 10 on. The electrode power source 11 was connected to the first negative terminal 11c so as to give a slightly negative voltage to the electrode reference terminal 11a.

When the thermionic beam heating by the high voltage provided by the control power source 12 exceeds a certain critical value (critical electron heating), vapor of the vaporized metal material 5 is generated, and the metal atoms are ionized to cause arc discharge 13 Occurs. Arc discharge 13
Heats the tip of the rod-shaped evaporated metal material 5 to increase the evaporation of the evaporated metal material 5. The vapor stream of the metal vapor containing the ions thus generated reaches the film forming surface of the work 6 by flowing as shown by the arrow 14, and activates the surface of the work 6 by the chemical action of the ions and hardens the film forming surface. Adhere to.

The evaporated metal material 5 is designed in the shape of a rod having a small diameter in order to reduce the heat capacity in the evaporation portion, and its consumption is relatively quick. In order to continue the vapor deposition work for a long time, the evaporated metal material 5 is continuously supplied by the continuous supply mechanism 15 so that the distance between the Wehnelt electrode 10 and the tip of the evaporated metal material 5 is kept constant. In the example of FIG. 1, the continuous supply mechanism 15 attaches and fixes the root of the evaporated metal material 5 to a support base 15a extending through the introduction hole 2a formed in the vacuum container 2, and vertically moving the support base 15a. Is guided by a guide cylinder 15b provided inside the vacuum container 2, and a bellows 15c for vacuum-sealing the introduction hole 2a from the outside of the vacuum container 2 is provided. The lower end of the support base 15a is attached to the bellows 15c and driven by a motor. The support 15 by the cam 15e
A is configured to move up and down. The support base 15a is
The cam 15e rises at a speed that compensates for the consumption of the evaporated metal material 5, and the tip of the evaporated metal material 5 is always located at a predetermined position.

The Wehnelt electrode 10 of the thermionic beam source 1
When the gap between the vaporized metal material 5 and the evaporated metal material 5 is 20 mm and 35 mm, respectively, the voltage-current (thermoelectron beam current +
The arc current) characteristic is as shown in FIG. Curve A in FIG. 2 is when the gap is 20 mm, and curve B is when the gap is 35 mm. In these cases, the electric current changes from the area mainly composed of the thermionic beam current to the area mainly composed of the arc current,
The broken line portions of the respective curves A and B are unstable regions due to the transition. These curves A and B depend on the amount of metal vapor supplied from the vaporized metal material 5 to the arc, and thus on the heat transfer characteristics of the vaporized metal material 5.

On the other hand, the critical electron heating power P (W) is expressed by P = (πd ² / 4l) κθ ... (Equation 1), where d is the diameter (cm) of the evaporated metal material 5. ),
l is the length (cm) of the evaporated metal material 5, κ is the thermal conductivity (W / cm / deg) of the evaporated metal material 5, and θ is the critical heating temperature (d).
Eg). d = 0.15, l = 1, κ = 2.35, θ = 930
Then, the value of P becomes 39 (W), and this value is
This is the point at which arcing starts in the characteristic curve of. In the case of the present invention, it is possible to start arcing with extremely low power by designing the heat transfer of the evaporated metal material 5.

FIG. 3 shows the details of the control power supply 12. In this case, the control power supply 12 comprises a variable constant current source 12d for generating a current I ₀ proportional to the control signal of the control signal generator 12c and a ballast resistor 12e. Configured. The operation of the control power supply 12 will be described with reference to FIG. 3 and FIG.
The current I ₀ generated by the variable constant current source 12d becomes I ₀ = κ · f (t) ···· Equation (2) and becomes the control signal f (t) of the control signal generator 12c. Proportionally, this current I ₀ is given by I ₀ = I _a + I _b (Equation 3), and the current I _b flowing through the ballast resistor 12e and (thermionic beam current + arc current) I is the sum of the _a. Also,
Voltage V _b generated across the conductance g _b ballast resistor 12e is _{V b = g b × I b} ........................... formula (4).

In FIG. 2, the tangent of the angle ψ with the current axis of the diagonal line 16 passing through I ₀ = 100 mA is drawn equal to the conductance g _b (20 μmho in this case). If the curve B shows V _b −I _b in this case,
The operating point 17 that satisfies equations (3) and (4) is also on this diagonal line. I ₀ = 150 mA and I ₀ = 50 mA
The same relationship holds for the operating points 18 and 19 respectively corresponding to. Therefore, if the current of the variable constant current source 12d is given, the operating point where the line of tan θ = g _b intersects is the curve B.
Is fixed even if it is S-shaped, and the operation of arc discharge becomes stable.

From the density ρ (g / cm ³ ) of the evaporated metal material 5 and the specific heat C _p (J / g · deg), the temperature conductivity is κ / ρ.
Given by C _p , the time constant τ of the evaporated metal material 5 is approximately given by τ = l ² (κ / ρC _p ) ... Equation (5). When the evaporated metal material 5 is aluminum, (κ / ρC _p ) = 1.1 (s / cm ² )
The time constant is about 1 second for l = 1 cm. The f (t) of the variable constant current source 12d increases the current I ₀ until the critical electron heating according to the temperature rise of the evaporated metal material 5, and then waits for the arc to stabilize, and then a predetermined operating current with the same time constant. Is set to increase the current I ₀ up to. Therefore, stable arc discharge can be generated without a special power source or electrode for arc discharge, and the structure of the evaporation source can be simplified.

FIG. 4 shows a second embodiment of the present invention.
The electrode configuration of the thermoelectron beam source 1, the shape of the evaporated metal material 5, and the configuration of the continuous supply mechanism 15 of the evaporated metal material supply device 4 are different from those in FIG. In this example, a deflection electrode 20 as an electrode of the thermoelectron beam source 1 is provided outside the Wernelt electrode 10, and the thermoelectron beam 3 is deflected by the deflection electrode 20 to the tip of a thin-walled cylindrical metal evaporation material 5. And irradiated. Further, as the continuous supply mechanism 15, a support base 15a to which the cylindrical evaporated metal material 5 is attached is led out to the outside from a vacuum-sealed introduction hole 2a of the vacuum container 2, and is attached to a screw cylinder 15f fixed to the vacuum container 2. When the rotation of the motor 15d is transmitted to the support base 15a via the gears 15g and 15g by meshing with the screw on the outer periphery of the support base 15a, the support base 15a compensates the consumption of the evaporated metal material 5 by the screw cylinder 15f. The distance between the tip and the Wehnelt electrode 10 is raised so as to be constant. Other configurations and operations are substantially the same as those of the embodiment shown in FIG.

FIG. 5 shows a third embodiment of the present invention.
The thermoelectron beam source 1 is mounted on an electrode assembly 25, the thermoelectron beam source 1 does not have an electron extraction electrode, and the vaporized metal material supply device 4 is surrounded by the radiation fins 4a. The structure of the continuous supply mechanism 15 for the material 5 and the point that the thermoelectron beam source 1 and the vaporized metal material supply device 4 are attached to the robot arm 21 are different from the embodiment of FIG.
The wirings 22 and 23 to the hot cathode 7 and the Wehnelt electrode 10 are housed in the flexible insulator row 24. Wiring 2 for hot cathode 7
A hot cathode current source 8 is connected between the Wehnelt electrode 10 and the Wehnelt electrode 10. A negative high voltage wiring 23 to the Wehnelt electrode 10 is connected to a negative high voltage terminal 12a of the control power supply 12.
The ground terminal 12b of is connected to the vacuum container 2. In this embodiment, the electrode structure is simpler than that of the embodiment shown in FIGS. 1 and 4, but in this case as well, the thermoelectron beam 3 emitted from the cathode filament 7b produces an electrostatic field generated by the hot cathode and the Wehnelt electrode 10. Is converged by and is accelerated and irradiated toward the tip of the evaporated metal material 5 having the ground potential. The electrode assembly 25 is attached to the evaporation head 26 at an angle of about 45 °, and the angle of the thermoelectron beam 3 with respect to the axis of the evaporation head 26 is about 45 °. The supporting hole 27 for leading out the wire-shaped evaporated metal material 5 of the evaporation head 26 is inclined in the −45 ° direction with respect to the axis of the evaporation head 26, and the support hole 27 is tightened with respect to the diameter of the evaporated metal material 5. The fit is adjusted to give frictional resistance to the movement of the evaporated metal material 5. The supply of the evaporated metal material 5 is performed by a solenoid actuator 28 that reciprocates a feed claw 29, and the feed claw 29 bites into the wire of the evaporated metal material 5 at the time of its forward movement to extrude the wire.
At the time of the return movement, it separates from the evaporated metal material 5 and returns by itself. The radiating fins 4a prevent excessive temperature rise of the components of the continuous supply mechanism 15. The wire of the evaporated metal material 5 is wound around the wire reel 30 inside the evaporation head 26, so that the evaporated metal material 5 can be replenished even during a long continuous operation.

The evaporation head 26 is attached to a tip arm 21a constituting the robot arm 21, and the tip arm 21a is rotatably attached to a drive arm 21d via intermediate arms 21b and 21c. The drive arm 21d
Can be driven around an axis. By the movement of these arms, the evaporation head 26 can freely move inside the vacuum container 2, and vapor deposition can be performed on the work 6 from any direction.

[0022]

As described above, according to the present invention, in the thermionic vacuum arc evaporation source provided with the arc plasmaization means for ionizing a part of the vapor of the vaporized metal material of the vaporized metal material supply device, The electron beam source is composed of a hot cathode, a Wehnelt electrode, a hot cathode current source for controlling the temperature of the hot cathode constant, and an electrode power supply for applying a negative voltage to the Wehnelt electrode with respect to the hot cathode. The vaporized metal material supply device is provided with a continuous supply mechanism for continuously supplying the vaporized metal material having a small heat capacity to a position close to the thermionic beam source, and the control power source is provided in accordance with the heat capacity of the vaporized metal material. As it is composed of a variable constant current source that raises the current at a programmed speed and a ballast load and has an arc plasma conversion function, it is possible to obtain stable metal vapor without providing a special arc plasma electrode and power supply. Rather, it has the effect that a metal film with good adhesion strength can be formed over a wide range at a constant and relatively high speed, and the evaporation source can be downsized. A robot arm can be provided in the vacuum container, and the thermionic beam source and the vaporized metal material supply device can be mounted on the tip of the robot arm, which has the effect of performing vapor deposition by changing the position and direction of the work.

[Brief description of drawings]

FIG. 1 is a cutaway side view of an embodiment of the present invention.

FIG. 2 is a diagram of voltage-current characteristics of the embodiment of FIG.

FIG. 3 is a detailed diagram of a control power supply according to the embodiment of FIG.

FIG. 4 is a cutaway side view of a second embodiment of the present invention.

FIG. 5 is a cutaway side view of essential parts of a third embodiment of the present invention.

[Explanation of symbols]

1 Thermionic beam source 2 Vacuum container 3
Thermionic beam 4 Evaporated metal material supply device 5 Evaporated metal material 6
Work 7 Hot cathode 8 Cathode current source 9
Electron extraction electrode 10 Wehnelt electrode 11 Electrode power supply 1
2 Control power supply 12a High negative pressure terminal 12b Grounding terminal 1
2c Control signal generator 12d Variable constant current source 12e Ballast resistor
13 arc discharge 15 continuous supply mechanism 20 deflection electrode
21 robot arm

Claims (4)

[Claims] 1. A thermoelectron beam source, a vaporized metal material supply device, a control power source for accelerating electrons by keeping the thermoelectron beam source at a negative high voltage with respect to the vaporized metal material supply device, and the thermoelectron beam. In a thermionic vacuum arc evaporation source equipped with arc plasmaization means for arc plasmaizing the vapor of the vaporized metal material of the vaporized metal material supply device vaporized by irradiation of an electron beam from a source to ionize a part of the arc plasma, The hot electron beam source, a hot cathode, a Wehnelt electrode, a hot cathode current source for controlling the temperature of the hot cathode to be constant, and an electrode power supply for giving a negative voltage to the Wehnelt electrode with respect to the hot cathode. The evaporation metal material supply device is provided with a continuous supply mechanism for continuously supplying the evaporation metal material having a small heat capacity to a position close to the thermionic beam source, and the control power source controls the heat capacity of the evaporation metal material. Program accordingly A small thermionic vacuum arc evaporation source characterized by comprising a variable constant current source for increasing the current at a controlled speed and a ballast load, and also having an arc plasma conversion function. 2. The hot electron beam source includes a hot cathode, a Wehnelt electrode, an electron extraction electrode, a hot cathode current source for controlling the temperature of the hot cathode to a constant value, and the hot cathode to the Wehnelt electrode. 2. The miniature thermionic vacuum arc evaporation source according to claim 1, wherein a negative voltage is applied to the electron extraction electrode, and an electrode power source that applies a positive voltage to the hot cathode is applied to the electron extraction electrode. 3. The hot electron beam source comprises a hot cathode, a Wehnelt electrode, an electron extraction electrode, a deflection electrode, a hot cathode current source for controlling the temperature of the hot cathode constant, and the Wehnelt electrode. 2. An electrode power supply for applying a negative voltage to the hot cathode to the deflection electrode, and a positive voltage to the hot cathode to the electron extraction electrode.
The miniature thermionic vacuum arc evaporation source according to. 4. A robot arm is provided in the vacuum container of the thermionic vacuum arc evaporation source, and the thermionic beam source and the vaporized metal material supply device are mounted at the tip of the robot arm. Or the small-sized thermionic vacuum arc evaporation source described in 3.