JPH05299193A - Plasma generating device - Google Patents

Abstract

PURPOSE:To provide a plasma generating device having extremely little ablation of a filament and a long life. CONSTITUTION:A needle valve 16 is gradually opened, and argon gas is introduced into a plasma generating device 9. A filament AC power source 26 is turned on, and the filament current If is gradually increased to the filament rated temperature. When a discharge power source 20 is turned on and the discharge voltage is applied, an electric discharge is started, and a discharge current Id flows. When the discharge current Id is increased, the sum of the filament heating current If and the discharge current Id/2 is detected by a detecting resistor 29 on the secondary side of a filament transformer, and this detection signal is fed to an error amplifier 30. The detected current value is compared with the rated current value by the error amplifier 30, a thyristor 31 is controlled based on the difference signal, and an increment of 1/2 of the discharge current Id is automatically subtracted from the heating current fed to a filament 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma generator for supplying argon gas or the like to a discharge part and further supplying electrons to the discharge part to generate plasma in the discharge part.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional ion plating apparatus using electrons from a plasma generator.
1 is a vacuum chamber. In the lower part of the vacuum chamber 1, a crucible 2 is arranged, and a material to be evaporated 3 is put therein. 4 is a filament, 5 is a high voltage power supply,
The electron beam generated from the filament 4 is deflected by 270 ° by a magnet (not shown), and the evaporated material 3 in the crucible 2 is irradiated with the electron beam. On top of the chamber 1 is placed a substrate 6 to which the ionized evaporation material is attached. An exhaust pipe 7 connected to a vacuum pump such as a turbo molecular pump (not shown) is provided at the bottom of the chamber 1. Further, inside the chamber 1, there is provided an electrode 8 having a ground potential for drawing out electrons from a plasma generating device described later. A plasma generation device 9 is provided on one side of the chamber 1. The plasma generation device 9 includes a filament 10 such as lanthanum hexaboride, an intermediate electrode 11, a screen electrode 12, an acceleration electrode 13, and an annular DC coil 1.
4, 15, an argon gas supply pipe 17 having a needle valve 16, a filament heating power source 18, a discharge stabilization resistor 19, a discharge power source 20, an intermediate electrode load resistor 21, and an acceleration power source 22. 23 is an exhaust pipe,
It is connected to a vacuum pump such as a turbo molecular pump (not shown). In the above configuration, first, the inside of the chamber 1 and the inside of the plasma generation device 9 are
The gas is exhausted to 10 ⁻⁵ Torr or less through the exhaust pipes 7, 23. After that, the needle valve 16 provided in the argon gas supply pipe 17 of the plasma generation device 9 is gradually opened to introduce the argon gas into the plasma generation device 9.
Then, the filament heating power source 18 is turned on, the filament current is gradually increased to the filament rated temperature, and electrons are emitted from the filament 16. Next, when the discharge power supply 20 is turned on and a discharge voltage is applied between the filament 16 and the screen electrode 12, a discharge is generated between them and a discharge current flows. Electrons from the filament collide with argon gas molecules to ionize the argon gas molecules, and this ionization proceeds to generate electron-excited plasma P. The flow rate of the argon gas and the discharge voltage at this time are adjusted to values at which the discharge is started according to Passion's law. Further, the plasma P generated in the plasma generator 9 is prevented from diverging by the magnetic field generated by the annular DC coil 14, and is focused in the central direction.

The electrons generated in the plasma P are applied with an accelerating voltage of about 100 V from the accelerating power source 22, extracted by the accelerating electrode 13, and irradiated toward the inside of the vacuum chamber 1 (electrode 8). At this time, the electrons are focused toward the center by the magnetic field generated by the DC coils 14 and 15,
Electrons are prevented from colliding with the acceleration electrode 13 and disappearing. In the vacuum chamber 1, the filament 4 is heated to emit electrons, and the evaporated material 3 in the crucible 2 is irradiated with electrons. The material 3 is heated and evaporated by irradiation with electrons. The evaporated material collides with the electrons from the plasma generation device 9 in the vacuum chamber 1, and is ionized and activated to generate plasma. The ionized material in the plasma is attracted to the substrate 6 and adheres to the substrate 6 for ion plating. If a reaction gas is supplied into the chamber 1 at the same time as the evaporation of the material 3 in the crucible 2, a substance based on the reaction between the evaporation material and the reaction gas can be attached to the substrate. For example, when the evaporation material is silicon and the reaction gas is oxygen gas, silicon dioxide (SiO ₂ ) is ion-plated on the substrate.

[0004]

With the above-mentioned structure, the filament 10 of the plasma generator 9 is formed in a spiral shape, and is further non-inductively wound so that the magnetic field due to the current flowing through the filament is canceled. .. The filament 10 may be wound in either a non-induction winding or an induction winding. By passing the heating current If from the heating power source 18 to the filament 10, the filament 10 is heated and electrons are emitted. The emission of the electrons is equivalent to the discharge current Id flowing into the filament 10. Usually, the tip of the filament 10 is heated best and the electrons are emitted most from this tip.
A discharge current of / 2 will flow. As a result, the heating current If and the discharge current I are applied to one terminal of the filament.
A current obtained by adding d / 2 to the current flows, and a current obtained by subtracting the discharge current Id / 2 from the heating current If flows to the other terminal. The temperature of half of the filament where the current obtained by adding the heating current and the discharge current flows exceeds the rated temperature, the sublimation of the filament member becomes intense, the wire becomes thin rapidly, and the life of the filament becomes extremely short. I will end up.

The present invention has been made in view of the above circumstances, and an object thereof is to realize a plasma generator having a long life by significantly reducing the consumption of filaments.

[0006]

A plasma generator according to the present invention comprises a discharge part, a means for introducing an inert gas into the discharge part, a filament for generating electrons to be supplied to the discharge part, and the filament. AC current source for supplying AC current to the filament, detection means for detecting current flowing in the filament, and control for controlling the amount of AC current flowing in the filament so that the detected current value becomes a predetermined value. And a means for generating plasma in the discharge part.

[0007]

The plasma generator according to the present invention heats the filament for supplying electrons to the discharge part with an alternating current, and further controls the current value flowing through the filament to a desired value.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows an ion plating apparatus using a plasma generator according to the present invention.
The same parts as those of the conventional device are given the same numbers. In this embodiment, the intermediate electrode 11 is insulated from the filament chamber F and the discharge chamber D and is connected to the discharge power source 2 via the load resistor 21.
It is connected to the positive side of 0. Screen electrode 12
Are insulated from the discharge chamber D and the acceleration chamber A and connected to the positive side of the discharge power source 20. The acceleration chamber A is insulated from the ground and connected to a vacuum pump (not shown) via the exhaust pipe 23 in order to maintain the pressure on the order of 10 ⁻⁴ Torr. The acceleration electrode 13 is insulated from the acceleration chamber A and the chamber 1, and is connected to the positive side of the acceleration power supply 23. The positive side of the acceleration power source 22 is connected to the ground, and the negative side is connected to the positive side of the discharge power source 20. The filament 10 is connected to an AC power supply 26 via a filament transformer 25. An intermediate tap on the secondary side of the transformer 25 is connected to one end of the stabilizing resistor 19, but balance resistors 27 and 28 are provided between the intermediate tap and both ends of the transformer 25 on the secondary side. .. As a result, the discharge voltage from the discharge power source 20 is applied to the intermediate tap as a bias voltage, so that the filament transformer is not DC-excited, that is, the unidirectional current does not flow in the coil. Reference numeral 29 is a detection resistor, 30 is an error amplifier, and 31 is a thyristor. The operation of such a configuration will be described below.

First, the inside of the chamber 1 and the inside of the plasma generator 9 are exhausted to 10 ⁻⁵ Torr or less through the exhaust pipes 7 and 23. Then, the needle valve 1 provided in the argon gas supply pipe 17 of the plasma generator 9
6 is gradually opened, and argon gas is introduced into the plasma generator 9. The filament AC power supply 26 is turned on, and the filament current If is gradually increased to the filament rated temperature. Next, when the discharge power supply 20 is turned on and a discharge voltage is applied, the discharge is started and the discharge current Id flows. At this time, electrons flow into the intermediate electrode 11 and the potential rises, but the intermediate electrode load resistor 21 is adjusted so that the voltage between the intermediate electrode 11 and the screen electrode 12 is about 15V. Next, the acceleration power supply 22 is turned on, and an acceleration voltage of several tens of volts is applied. Then, a current is passed through the annular DC coil 14, the current value is gradually increased, and the current flowing through the screen electrode 12 is adjusted to be the minimum. Further, a current is passed through the annular DC coil 15, the current value is gradually increased, and the current flowing through the acceleration electrode 13 is adjusted to be the minimum. When the discharge current is increased, the detection resistance 29 on the secondary side of the filament transformer detects the sum of the filament heating current If and the discharge current Id / 2, and this detection signal is supplied to the error amplifier 30. This error amplifier 3
At 0, the detected current value and the rated current value are compared, the thyristor 31 is controlled based on the difference signal, and the heating current supplied to the filament 10 is automatically the discharge current I.
An increase of 1/2 of d is reduced.

As described above, an alternating current is supplied to heat the filament 10, and the increase in the current due to the inflow of the discharge current is automatically reduced to heat the entire filament at a constant current value. As a result, it is possible to prevent the filament from being heated strongly locally, so that the life of the filament can be remarkably extended.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to this embodiment. For example, while electrons are extracted from the plasma generation device, ions may be extracted from the plasma.

[0012]

As described above, in the plasma generator according to the present invention, the filament for supplying electrons to the discharge part is heated by an alternating current, and further, the current value flowing in the filament is set to a desired value. Since it is configured to be controlled, it is possible to heat the entire filament at a constant current value at all times, and it is possible to prevent the filament from being heated strongly in part, so that the life of the filament can be significantly extended. Further, the discharge current can flow up to twice the rated filament current value by controlling the effective current flowing through the filament at a constant rated current.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an ion plating device using a plasma generation device according to the present invention.

FIG. 2 is a diagram showing an ion plating device using a conventional plasma generation device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber 2 ... Crucible 3 ... Evaporating material 4 ... Filament 5, 18 ... Power supply 6 ... Substrate 7, 23 ... Exhaust pipe 8 ... Electrode 9 ... Plasma generator 10 ... Filament 11 ... Intermediate electrode 12 ... Screen electrode 13 ... Acceleration electrode 14, 15 ... Annular DC coil 16 ... Needle valve 17 ... Argon gas supply pipe 19 ... Discharge stabilization resistance 20 ... Discharge power supply 21 ... Intermediate electrode load resistance 22 ... Acceleration power supply 25 ... Filament transformer 26 ... AC power supply 27, 28 … Balance resistance 29… Detection resistance 30… Error amplifier 31… Thyristor

Front page continuation (72) Inventor Katsunobu Aoyagi 2-1 Hirosawa, Wako-shi, Saitama, RIKEN (72) Inventor Kazutoshi Kusakabe 3-1-2, Musashino, Akishima-shi, Tokyo Japan Electronics Co., Ltd.

Claims (1)

[Claims] 1. A discharge part, means for introducing an inert gas into the discharge part, a filament for generating electrons to be supplied to the discharge part, and an alternating current source for supplying an alternating current to the filament. Detecting means for detecting the current flowing through the filament, and control means for controlling the amount of alternating current flowing through the filament so that the detected current value becomes a predetermined value, and generate plasma in the discharge part. A plasma generation device configured as described above.