JP2002155355A - Method for starting pressure-gradient type plasma generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for starting a pressure-gradient type plasma generator by which the occurrence of an abnormal electric discharge by the magnetic field of a focusing coil can be prevented. SOLUTION: In the method for starting the pressure-gradient type plasma generator 1 having a pressure-gradient type plasma gun 11 and a focusing coil 13 enclosing a short tube part 12 for fixing the pressure gradient type plasma gun 11, gas for assisting electric discharge is introduced into the pressure- gradient type plasma gun 11 to perform low-current electric discharge and then the magnetic field by the focusing coil 13 is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for starting a pressure gradient type plasma generator applied to a vacuum film forming apparatus such as ion plating, plasma sputtering or plasma CVD.

[0002]

2. Description of the Related Art Conventionally, a pressure gradient type plasma generator 2 shown in FIG. 3 is known. This pressure gradient type plasma generator 2 has a pressure gradient type plasma gun 11 and a pressure gradient type plasma gun 11. And a focusing coil 13 surrounding the short tube portion 12. The short tube portion 12 is open toward the inside of the vacuum chamber 14. The focusing coil 13
As shown in FIG. 3, a magnetic field in the direction of the anode is formed from the pressure gradient plasma gun 11 to control the focusing state and direction of the plasma.

The pressure gradient plasma gun 11 holds an annular intermediate electrode portion 22 which is brought into a potential state between the cathode 21 and an anode (not shown) in the vacuum chamber 14, and the cathode 21, and discharges electricity to the central portion. A cathode mounting portion 24 having an inlet 23 for an auxiliary gas (eg, Ar gas), and a cathode mounting portion 24 in conduction with the cathode 21 and the intermediate electrode portion 22 are electrically insulated, for example, made of glass or ceramic. And an insulating tube 25 made of aluminum. The cathode 21 has an auxiliary electrode 26 made of a tubular Ta, which forms a flow path of the discharge auxiliary gas, and the auxiliary electrode 2.
Main electrode 2 made of a disc-shaped LaB ₆ surrounding the outer periphery of the tip end of the main electrode 2
7 and a cathode casing 28 made of a conductive material such as Mo for holding the main electrode 27.

When the pressure gradient type plasma generator 2 is started, first, the introduction of a discharge assisting gas at a predetermined flow rate (eg, 10 to 30 sccm) from the inlet 23 of the cathode mounting section 24 is started. A magnetic field is generated by passing a current through the intermediate electrode section 22 and the focusing coil 13.
Subsequently, 5 to 30 is applied between the auxiliary electrode 26 and the anode.
A, and indirectly heats the main electrode 27 by discharging a small current of about A, and 50-200 A between the main electrode 27 and the anode.
Transfer to a large current discharge.

[0005]

According to the above-described method for starting the pressure gradient plasma generator 2, the magnetic field generated by the focusing coil 13 is already applied to the cathode 21 and the intermediate electrode portion 22 at the time of the initial discharge which is a small current discharge. Is formed,
Plasma generated by the initial discharge is easily trapped by this magnetic field. For this reason, discharge is induced in the outer peripheral portion of the cathode casing 28 made of a conductive material such as Mo, as shown by A in FIG. 3, and the efficiency of energy supply to the cathode 21 is reduced. As a result, there arises a problem that it becomes difficult to heat the main electrode 27 to a temperature at which thermionic electrons are sufficiently emitted. Also, due to the induced discharge, a substance evaporated or sputtered from the cathode casing 28 made of a conductive material such as Mo adheres to the inner surface of the insulating tube 25, and the heat absorption of the insulating tube 25 increases, so that the cathode casing 28 There is a problem in that an abnormal temperature rise occurs in the outer peripheral portion and the O-rings (not shown) disposed at both ends of the insulating tube 25 are burned. SUMMARY OF THE INVENTION The present invention has been made in order to eliminate such a conventional problem, and a method of starting a pressure gradient type plasma generator capable of preventing occurrence of abnormal discharge due to a magnetic field of a focusing coil at an initial discharge. It is intended to provide.

[0006]

In order to solve the above-mentioned problems, a first aspect of the present invention is a pressure gradient type plasma gun and a focusing coil having a focusing tube surrounding a short tube portion for mounting the pressure gradient type plasma gun. In the method of starting the gradient plasma generator, after a discharge assisting gas is introduced into the pressure gradient plasma gun to cause a small current discharge, a magnetic field is generated by the focusing coil.

According to a second aspect of the invention, in addition to the configuration of the first aspect, the magnetic field is generated two to three minutes after the start of the small current discharge.

[0008]

Next, embodiments of the present invention will be described with reference to the drawings. FIGS. 1 and 2 show a pressure gradient plasma generator 1 to which the method according to the present invention is applied, which is substantially identical in structure to the pressure gradient plasma generator 2 shown in FIG. The same reference numerals are given to the same parts, and the description is omitted. As shown in the figure, the cathode mounting portion 24 is connected to a negative electrode of a power source 31 for discharging, and a positive electrode of the power source 31 for discharging is connected to a hearth 33 arranged at a lower portion in the vacuum chamber 14 for receiving a deposition material 32. And the hearth 33 forms the above-mentioned anode. In addition, the intermediate electrode portion 22 includes the first intermediate electrode 3
4 and a second intermediate electrode 35.
37 is connected to the positive pole of the power source 31 for discharge.
Further, a substrate 38 is disposed in an upper part in the vacuum chamber 14. Then, a plasma 39 is formed from the pressure gradient plasma gun 11 toward the evaporation raw material 32 on the hearth 33, whereby the evaporation raw material 32 is evaporated and deposited on the substrate 38 to form a thin film.

Next, a method of starting the pressure gradient plasma generator 1 according to the present invention applied to the pressure gradient plasma generator 1 will be described. When starting the pressure gradient plasma generator, first, as described above,
After the introduction of the discharge assisting gas at a predetermined flow rate (for example, 10 to 30 sccm) from the inflow port 23, a magnetic field is generated by applying a current to the intermediate electrode unit 22. After that, a small current of, for example, about 10 A is discharged between the auxiliary electrode 26 and the anode to indirectly heat the main electrode 27. And
When the small current discharge starts, an electric current is caused to flow through the focusing coil 13 to generate a magnetic field around the cross section of the focusing coil 13 represented by the magnetic force lines indicated by two-dot chain lines in FIG. Thereafter, the main electrode 27 is sufficiently heated to a temperature at which thermionic electrons are emitted, and the main electrode 27 shifts to a large current discharge of, for example, about 100 A.

As a result, discharge at the outer peripheral portion of the cathode casing 28 is avoided, evaporation and sputtering from the cathode casing 28 do not occur, and abnormal temperature rise at the outer peripheral portion of the cathode casing 28 can be prevented. The O-rings disposed at both ends are not burned, and the durability of the components near the outer peripheral portion can be improved. Further, Ta-LaB ₆ results plasma at the tip of the composite cathode 21 is concentrated, the main electrode 27 is heated to a possible thermionic emission temperature in a short time, to ensure a stable plasma in the early Will be possible.

After the small current discharge, the focusing coil 1
3. The more the magnetic field is generated by
While the temperature at the tip of the cathode casing 28 rises and promotes the heating of the main electrode 27, it is good to scatter plasma in a vacuum chamber for a long time in a state where a magnetic field is not formed by the focusing coil 13. It is not preferable to keep the state. Therefore, it is preferable to generate a magnetic field by the focusing coil 13 two to three minutes after the start of the small current discharge.

[0012]

As is apparent from the above description, according to the present invention, a discharge assisting gas is introduced into a pressure gradient plasma gun, a small current is discharged, and then a magnetic field is generated by a focusing coil. Discharge at the outer peripheral portion of the cathode casing of the pressure gradient plasma gun is avoided, and abnormal temperature rise at the outer peripheral portion can be prevented.As a result, burning of a seal member for maintaining a vacuum around the cathode can be prevented, and In addition to improving the durability of the components around the cathode, the plasma is concentrated at the tip of the cathode, so that the heating is promoted and a stable plasma can be secured early. It has the effect of becoming. Further, according to the present invention, since the magnetic field is generated two to three minutes after the start of the small current discharge, in addition to the above-described effects, the inside of the pressure gradient plasma generator is further damaged by the plasma. The effect that it becomes possible to suppress it is produced.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a pressure gradient plasma generator to which a starting method according to the present invention is applied.

FIG. 2 is a diagram showing a magnetic field generated by a focusing coil of the pressure gradient plasma generator shown in FIG. 1 and plasma formed under the magnetic field.

FIG. 3 is a diagram showing a magnetic field generated by a focusing coil of a conventional pressure gradient plasma generator and a discharge induced under the magnetic field.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Pressure gradient type plasma generator 11 Pressure gradient type plasma gun 12 Short tube part 13 Focusing coil 14 Vacuum chamber 21 Cathode 22 Intermediate electrode part 23 Inflow port 24 Cathode mounting part 25 Insulation tube 26 Auxiliary electrode 27 Main electrode 28 Cathode casing 31 Discharge Power supply 32 Deposition material 33 Hearth 34 First intermediate electrode 35 Second intermediate electrode

Claims (2)

[Claims] 1. A method for starting a pressure gradient plasma generator comprising a pressure gradient plasma gun and a focusing coil surrounding a short tube portion for mounting the pressure gradient plasma gun. A method for starting a pressure gradient type plasma generator, wherein a magnetic field is generated by the focusing coil after introducing a discharge assisting gas to cause a small current discharge. 2. The method according to claim 1, wherein the magnetic field is applied two to two times after the start of the small current discharge.
The method for starting a pressure gradient plasma generator according to claim 1, wherein the generation is performed after three minutes have elapsed.