JPH10340794A - Plasma-generating apparatus - Google Patents

Abstract

(57) [Problem] To provide a plasma generation device that prevents electrode consumption under a high discharge voltage. SOLUTION: A cathode 4 having an annular cathode downstream of a cylinder into which a discharge gas is introduced, annular anodes 22 to 24 provided downstream of the cathode 4, and a final anode 7
By increasing the number of annular anodes 22 to 24 of the plasma generator for generating desired particles into plasma by generating an arc discharge between 2 and 3 or more, the potential difference between the annular anodes 22 to 24 is reduced. Become smaller. This potential difference
By setting the voltage to 12 V or less, the potential gradient at the annular anodes 22 to 24 becomes small, and the energy for sputtering decreases. As a result, plasma can be generated while keeping the inside of the reaction vessel 3 at a low pressure of 10 ^-4 Torr,
A dense film 8a can be formed on the substrate 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a plasma generator.

[0002]

2. Description of the Related Art A plasma generator is used as a film for ion plating, a gas ionizer or a heat source for evaporating a material.

FIG. 6 is a conceptual diagram of an ion plating apparatus using a conventional plasma generator.

[0004] The ion plating apparatus 1 mainly comprises a pressure gradient type plasma generator 2 and a reaction vessel 3. The plasma generator 2 generates an initial discharge between the cathode 4 having an annular cathode on the downstream side of the cylinder into which a discharge gas such as Ar is introduced, and the cathode 4 provided on the downstream side of the cathode 4. (A first anode 5 and a second anode 6) and a final anode 7 provided downstream of the second anode 6 to generate plasma by arc discharge between the anode 4 and the cathode 4. It is configured.

[0005] In the reaction vessel 3, a final anode 7 of the plasma generator 2 is arranged, and a reaction gas such as O ₂ gas or N ₂ gas is introduced. A crucible 9 for accommodating the film forming material 8 is arranged at the bottom of the reaction vessel 3, and a substrate 10 is arranged above the crucible 9 to form a film 8 a. The film material 8 in the crucible 9 is irradiated with an electron beam from an electron gun (not shown) provided outside the reaction vessel 3.

[0006] A direct current high voltage power supply 11 for generating arc discharge is connected to the cathode 4 and the final anode 7. Resistors 12 and 13 are inserted between the DC high-voltage power supply 11 and the first anode 5 and the second anode 6, respectively. DC power supply 14 is placed between crucible 9 and substrate 10.
Is connected.

When the plasma generator operates, a high DC voltage is applied between the cathode 4 and each of the anodes 5 to 7 to generate an arc discharge. When the electron beam is irradiated from the electron gun onto the film forming material 8 in the crucible, the film forming material 8 evaporates, and the evaporated particles are ionized while reaching the substrate 10 to form a plasma, which reacts with the plasmated reaction gas. The compound thus deposited adheres to the substrate 10 as a film 8a.

[0008]

Incidentally, it is known that in order to form a dense film on the substrate 10, the pressure in the reaction vessel 3 is preferably set to about 10 ^-4 Torr. To generate an arc discharge in the reactive gas atmosphere of such low pressures and O _2, N _2, etc., it is necessary to a potential difference as high as the voltage over 70V between the cathode 4 and the final anode 7 (Usually 40V-50V).

However, when the potential difference between the cathode 4 and the final anode 7 increases, the positive ions generated in the reaction vessel 3 collide with the first anode 5 and the second anode 6 to which a negative voltage is applied, and cause sputtering. Occurs. The sputtering causes the first anode 5 and the second anode 6 to be consumed, thereby not only shortening the life of the ion plating apparatus, but also causing particles of the sputtered anode material to enter the film 8a as impurities. For example, when the material of the first anode 5 and the second anode 6 is copper, the sputtered copper enters the reaction vessel 3 and is mixed with the film forming material 8 into the film 8a on the substrate 10 to reduce the quality of the product. Will drop.

On the other hand, the pressure in the reaction vessel 3 is increased by 10
^{When the} pressure is increased to ^-3 Torr, the probability that the discharge gas is taken into the film 8a increases, and as a result, the density of the film 8a decreases and the film becomes rough. When such a film is used for an optical filter, there is a problem in that the film changes with time and tends to contain water, and the absorption wavelength shifts.

An object of the present invention is to provide a plasma generating apparatus which solves the above-mentioned problems and prevents the electrodes from being consumed under a high discharge voltage.

[0012]

According to the present invention, a cathode having an annular cathode is provided downstream of a cylinder into which a discharge gas is introduced, and the cathode is provided downstream of the cathode. An annular anode for generating an initial discharge between the anode and a final anode for generating plasma by arc discharge between the anode and the cathode is provided downstream of the anode. At least three are provided on the downstream side, and the potential difference between the annular anodes is set to a predetermined value or less.

In the present invention, in addition to the above configuration, the potential difference between the annular anodes is preferably 12 V or less.

In the present invention, in addition to the above configuration, the inner diameter of the annular insulator provided between the annular anodes to hold the annular anode is preferably larger than the inner diameter of the annular anode.

According to the present invention, since the discharge voltage is constant,
Increasing the number of annular anodes from two to three or more reduces the potential difference between each annular anode. By setting this potential difference to a predetermined value, that is, 12 V or less,
The potential gradient at the annular anode is reduced and the energy of sputtering is reduced. As a result, plasma can be generated while keeping the inside of the reaction vessel at a low pressure of 10 ^-4 Torr, and a dense film can be formed.

Further, by making the inside diameter of the ring insulator provided between the ring anodes larger than the inside diameter of the ring anode, the ring insulator becomes a shadow of the ring anode, and collision of plasma particles can be prevented. The annular anode can be cooled by a water cooling method, but the annular insulator is effective because it is difficult to cool.

[0017]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a conceptual view showing an embodiment of an ion plating apparatus using the plasma generating apparatus of the present invention, and FIG. 2 is a view showing a film forming material in a crucible in the reaction vessel shown in FIG. It is explanatory drawing for demonstrating heating. FIG.
The same reference numerals are used for members similar to those of the conventional example shown in FIG.

The ion plating apparatus 20 shown in FIG.
Is mainly composed of a pressure gradient type plasma generator 21 and a reaction vessel (vacuum vessel) 3. The plasma generator 21 includes a cathode 4 having an annular cathode downstream of a cylinder into which a discharge gas (for example, Ar) is introduced;
Annular anode (first anode 22, second anode 22,
(Referred to as an anode 23 and a third anode 24) and a final anode 7 provided downstream of the third anode 24 to generate plasma by arc discharge between the cathode 4 and the anode 4.

Between the first anode 22, the second anode 23 and the third anode 24, these anodes 22 to 2
Annular insulators 25, 26 having an inner diameter larger than the inner diameter of 4
Is provided.

In the reaction vessel 3, a plasma generator 21
Of the reaction gas (for example, Ti
O ₂ gas is introduced when forming O ₂ film, and N ₂ gas is introduced when forming TiN ₂ film. A film forming material (for example, TiO ₂ or Ti
In the case of forming an N ₂ film, a crucible 9 containing Ti) 8 is arranged, and a substrate 10 on which a film 8 a is formed is arranged above the crucible 9. The crucible 9 is irradiated with an electron beam 31 from an electron gun 30 provided outside the reaction vessel 3 (see FIG. 2).

Between the cathode 4 and the final anode 7, a DC high voltage power supply 11 for generating an arc discharge is connected. DC high-voltage power supply 11 and first anode 22,
Resistors 27 to 29 for applying a predetermined voltage to the anodes 22 to 24 are inserted between the second anode 23 and the third anode 24, respectively. Between the crucible 9 and the substrate 10, a DC power supply 14 for accelerating the evaporated particles of the film forming material is connected.

When the plasma generator operates, a high DC voltage is applied between the cathode 4 and each of the anodes 22 to 24 to generate an arc discharge. When the electron beam 31 irradiates the Ti 8 in the crucible 9 from the electron gun 30, the Ti 8 evaporates, and the Ti 8 particles are ionized while reaching the substrate 10 to form plasma and react with the plasma O ₂ . TiO ₂ adheres to the substrate 10 as a film 8a.

FIG. 3 is a diagram showing the relationship between the position from the cathode of the plasma generator shown in FIG. 1 and the potential, and FIG.
FIG. 6 is a diagram showing a relationship between a position from a cathode of the conventional plasma device shown in FIG. 5 and a potential. 3 and 4, the horizontal axis indicates the position from the cathode, and the vertical axis indicates the potential.

The potential difference ΔV _a between the final anode 7 and the second anode 6 of the conventional plasma generator 2 is about 15 V, and the potential difference ΔV _b between the second anode 6 and the first anode 5 is 20 V or more. Met. Both anodes 5, 6
Consumption due to the occurrence of sputtering occurred (FIG. 6).

On the other hand, the potential difference ΔV ₁ between the final anode 7 and the third anode 24 of the plasma generator 21 shown in FIG. 1 is about 12 V, and the potential difference between the third anode 24 and the second anode 23 is The potential difference ΔV ₂ is about 12 V, and the potential difference ΔV between the second anode 23 and the first anode 22 is
₃ was about 12V. The anodes 22 to 24 were not consumed by sputtering.

That is, since the discharge voltage is constant, by increasing the number of annular anodes from two to three or more,
The potential difference between each annular anode becomes smaller. By setting the potential difference to a predetermined value, that is, 12 V or less, the potential gradient at the annular anode is reduced, the energy for sputtering is reduced, and the annular anode is not consumed by sputtering. As a result, 10 ^-4
Plasma can be generated while maintaining a low pressure of Torr, and a dense film can be formed.

Further, by making the inside diameter of the ring insulator provided between the ring anodes larger than the inside diameter of the ring anode, the ring insulator becomes a shadow of the ring anode, and collision of plasma particles can be prevented. The annular anode can be cooled by a water cooling method, but the annular insulator is effective because it is difficult to cool.

As described above, in the plasma generator according to the present invention, by increasing the number of annular anodes provided between the cathode and the final anode, the potential difference between the annular anodes is reduced, and the amount of sputtering is reduced. The smaller the potential difference between the annular anodes, the smaller the energy at which ions in the plasma collide with the electrodes, and the smaller the amount of sputtering. When the amount of sputtering is small, the consumption of the annular anode is reduced, the life of the plasma generator is prolonged, the probability of impurity contamination into the film being formed is reduced, and a dense film can be obtained. Therefore, the performance of the ion plating apparatus is improved.

Here, in this embodiment, the case where the electron gun is used to evaporate the film forming material in the crucible has been described. However, the present invention is not limited to this, and the plasma flow from the plasma generator 2 is bent by the magnetic field. By directly irradiating the film-forming material 8 in the crucible 9 to evaporate the film-forming material (see FIG. 5), generating electrons from the crucible and irradiating the film-forming material 8 in the crucible 9 by bending with a magnetic field. The film forming material 8 may be evaporated. still,
FIG. 5 is an explanatory diagram for explaining the heating of the film forming material in the crucible in the reaction vessel shown in FIG.

[0031]

In summary, according to the present invention, the following excellent effects are exhibited.

By providing at least three annular anodes on the downstream side of the cathode and making the potential difference between the annular anodes equal to or less than a predetermined value, it is possible to provide a plasma generator in which the electrodes are prevented from being consumed under a high discharge voltage. Can be.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an embodiment of an ion plating apparatus using a plasma generator of the present invention.

FIG. 2 is an explanatory diagram for explaining heating of a film forming material in a crucible in a reaction vessel shown in FIG.

FIG. 3 is a diagram showing a relationship between a position from a cathode of the plasma generator shown in FIG. 1 and a potential.

FIG. 4 is an explanatory diagram for explaining heating of a film forming material in a crucible in the reaction vessel shown in FIG.

FIG. 5 is an explanatory diagram for describing heating of a film forming material in a crucible in the reaction vessel shown in FIG.

FIG. 6 is a conceptual diagram of an ion plating apparatus using a conventional plasma generator.

[Explanation of symbols]

 Reference Signs List 3 reaction vessel 4 cathode 7 final anode 8 film-forming material (Ti) 8a film 9 crucible 10 substrate 21 plasma generator 22 annular anode (first anode) 23 annular anode (second anode) 24 annular anode (third anode) 25 , 26 annular insulator

Claims (3)

[Claims] 1. A cathode having an annular cathode is provided downstream of a cylinder into which a discharge gas is introduced, and an annular anode for generating an initial discharge with the cathode is provided downstream of the cathode. In a plasma generator provided with a final anode for generating plasma by arc discharge between the cathode and the cathode downstream of the annular anode,
A plasma generator, wherein at least three annular anodes are provided downstream of the cathode, and a potential difference between the annular anodes is set to a predetermined value or less. 2. The plasma generator according to claim 1, wherein a potential difference between said annular anodes is 12 V or less. 3. The plasma generator according to claim 1, wherein an inner diameter of an annular insulator provided between the annular anodes to hold the annular anode is larger than an inner diameter of the annular anode.