DE102010060591B4 - Plasma generator - Google Patents

Abstract

Plasma generator, which is equipped with a cylindrical chamber component, which has a cylindrical electrode (1), a screen (4), which is arranged in the cylindrical chamber component, around the cylindrical chamber component in a first chamber (2) which has gas supply connections (10) , and a second chamber (3) which has gas outlet connections (11) to subdivide, a rod-shaped electrode (5) which is placed inside the second chamber (3) on a central axis of the cylindrical electrode (1), and a sub-electrode ( 6), which is placed on the first chamber (2) and is able to apply a potential different from that of the cylindrical electrode (1), the plasma generator creating an electric field between the cylindrical electrode (1) and the rod-shaped electrode (5) applies to generate a plasma, further separately applying an electric field between the cylindrical electrode (1) and the sub-electrode (6) to separate a plasma t from the plasma which is generated between the rod-shaped electrode (5) and the cylindrical electrode (1), and which has plasma regions of the first chamber (2) and the second chamber (3), which through the holes of the diaphragm (4 ) are connected, the plasma generated between the rod-shaped electrode (5) and the cylindrical electrode (1) being a glow discharge, and the plasma generated between the cylindrical electrode (1) and the sub-electrode (6) , a glow discharge or an arc discharge, and wherein a pressure of the second chamber (3) is a pressure of 300 Pa to 101 kPa.

Description

TECHNICAL AREA

The present invention relates to a plasma generator which forms a stable plasma on the electrode members and generates a high density plasma.

STATE OF THE ART

Plasma is in a reactive state, so it has conventionally been widely used in surface treatment, thin film formation, etching, and other fields. In order to carry out a faster treatment, it is necessary to increase or increase the plasma density and to multiply the activated reactive ions. A plasma generator is also used with a DLC coating (diamond like carbon). Methane or acetylene or some other hydrocarbon gas is disassociated in plasma to produce radicals or ions or other activated reactive ions which are used to form DLC on the surface of a base material. When forming a DLC at a high speed, it is necessary to use high density plasma having a high density of activated reactive ions.

For this reason, in order to obtain a high density plasma, the method of increasing the gas pressure to increase the activated ions themselves, the method of increasing the electric field strength to improve the degree of dissolution, the method using a magnetic field, to contain the plasma; and other methods are used. However, with the method of using a magnetic field to confine the plasma, it is not possible to improve the plasma density by an order of magnitude ^{from that commonly used from 10 8} / cm ³ to 10 ¹⁰ / cm ^3. Furthermore, in the method of increasing the gas pressure or the method of increasing the power source voltage, there is a slight shift from the normally desired glow discharge (low temperature plasma) to an arc discharge (high temperature plasma), and hence a problem arises in the operation.

As a technique for increasing the electric field density (electric field density = voltage / distance), the technique of shortening the distance between the electrodes is effective, but when the distance between the electrodes is shortened without applying a higher voltage, it was not possible to generate plasma. The reason will be briefly explained next. Due to Paschen's law, there is a downward-facing curve of the correlation between the discharge start voltage and the (pressure x distance between electrodes). For this reason, when the distance between the electrodes becomes narrower under the same pressure, the voltage required to start the discharge increases and discharge does not continue to occur at the voltage at which discharge started .

As a result, arc discharge occurred locally and unstably due to the concentration of the electric field, etc., and stable discharge could not be obtained. In the prior art disclosed in Japanese Unexamined Patent Publication No. JP 2001 - 023 972 A As can be seen, attempts have been made to use a double tube electrode structure in order to obtain a uniform electric field, but the above problems have nonetheless been encountered.

• JP S57- 131 373 A ,
• US 2 920 234 A ,
• EP 1 518 669 A2 ,
• US 6 949 735 B1 ,
• US 3 944 873 A ,
• JP H07- 153 596 A,
• JP H02- 244 624 A,
• JP H11-82 556 A ,
• JP H11- 140 646 A ,
• US 2003/0 106 643 A1 ,
• CN 101 363 118 A ,
• US 6 599 588 B2 ,
• CN 1 692 492 A ,
• JP H 07-153596 A

Further prior art is disclosed in the following publications:

• JP S57-131 373 A ,
• U.S. 2,920,234 A ,
• EP 1 518 669 A2 ,
• US 6,949,735 B1 ,
• U.S. 3,944,873 A ,
• JP H07-153 596 A,
• JP H02- 244 624 A,
• JP H11-82 556 A ,
• JP H11-140646 A ,
• US 2003/0 106 643 A1 ,
• CN 101 363 118 A ,
• US 6 599 588 B2 ,
• CN 1 692 492 A ,
• JP H 07-153596 A

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the above problem.

The object of the invention is to provide a plasma generator which forms a stable plasma with narrow, small electrode components and which generates a high-density plasma.

This object is achieved by the subject matter of claim 1. Advantageous further developments thereof are the subject matter of the respective dependent claims.

In order to solve the above problem, it is a partial aspect of the invention of claim 1 to provide a plasma generator which is provided with a cylindrical chamber member which has a cylindrical electrode ( 1 ), a diaphragm or baffle plate ( 4th ), which is arranged in the cylindrical chamber component in order to convert the cylindrical chamber component into a first chamber ( 2 ), which gas supply connections ( 10 ), and a second chamber ( 3 ), which gas outlet connections ( 11 ) has, to subdivide, a rod-shaped electrode ( 5 ), which within the second chamber ( 3 ) on a central axis of the cylindrical electrode ( 1 ) is placed, and a lower electrode ( 6th ), which at the first chamber ( 2 ) is placed and is able to pick up one of the cylindrical electrode ( 1 ) has to apply different potential, whereby the plasma generator creates an electric field between the cylindrical electrode ( 1 ) and the rod-shaped electrode ( 5 ) to generate a plasma while still separating an electric field between the cylindrical electrode ( 1 ) and the lower electrode ( 6th ) to generate plasma separately from the plasma, which is between the rod-shaped electrode ( 5 ) and the cylindrical electrode ( 1 ) is generated, and which plasma areas of the first chamber ( 2 ) and the second chamber ( 3 ), which through the holes in the panel ( 4th ) are connected.

Due to this, it is possible to increase the plasma density to increase the activated reactive ions, and it is possible to perform treatment stably and at a higher speed. It is possible to provide active electrons and ions in the narrow, small electrode spaces in order to improve the particle density of the plasma and to maintain a discharge even with a low voltage.

It should be noted that the above assigned reference characters are examples indicating correspondence with specific embodiments described in the embodiments section explained later.

Figure list

• 1 Fig. 3 is a schematic view showing an embodiment of the present invention;
• 2 Fig. 13 is a schematic view showing another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, an embodiment of the present invention will be described while referring to the drawings. Components of the same nature in the embodiments are assigned the same reference numerals and explanations thereof are omitted.

The object treated in this embodiment of the present invention is, for example, a needle of an injector, an extrusion pin of a casting mold or another columnar object. At this point, an embodiment will be explained in which a plasma generator is used to treat the surface (removing impurities or improving the same) to form a thin layer of DLC, SiO ₂ , etc., or to etch otherwise treat a columnar object. The treated object is not limited to the examples illustrated above. The present invention is applicable as long as the object is columnar or cylindrical.

1 Fig. 13 is a schematic view showing a first embodiment of the present invention.

The explanation will be given using that the outer peripheral surface of a rod-shaped electrode 5 is dealt with in the present embodiment. The case where the treated object is a cylindrical body 12th is will be explained later. The cylindrical chamber member is a chamber that penetrates the interior of the cylindrical electrode 1 is surrounded, and is in a first chamber 2 which gas supply connections 10 has, and a second chamber 3 which gas outlet connections 11 has divided. To a first chamber 2 and a second chamber 3 to be subdivided is an aperture 4th placed in the cylindrical chamber component. The second chamber 3 has a rod-shaped electrode 5 which within it on a central axis of the cylindrical electrode 1 is placed. An electric field is created between this and the cylindrical electrode 1 applied to generate a plasma.

The voltage between the rod-shaped electrode 5 and the cylindrical electrode 1 is, as an example, preferably 100 V to 5 kV. A lower electrode is located inside or in the first chamber 6th placed. The voltage between the lower electrode 6th and the cylindrical electrode 1 is, as an example, preferably 50 V to 500 V. An electric field is established between the cylindrical electrode 1 and the rod-shaped electrode 5 applied to generate a plasma. Furthermore, it is separated from the plasma, which is between the rod-shaped electrode 5 and the cylindrical electrode 1 an electric field is generated between the cylindrical electrode 1 and the lower electrode 6th applied to generate a plasma. If the upper and lower chambers are not separated, the Arc discharge in the first chamber 2 the upper side the glow discharge in the second chamber 3 cause the bottom to become unstable, causing a separation by the bezel 4th necessary is.

Through holes of the cover 4th are dependent on the size of the cylindrical electrode on appropriate diameters and appropriate numbers 1 set up or discontinued. As an example of this embodiment is the bezel 4th inside a cylindrical electrode 1 of a diameter of 15 mm and a height of 150 mm or the like. Arranged to divide the inside of the cylindrical chamber at a position of about a height of 55 mm. Furthermore, a rod-shaped electrode is located within the second chamber 5 a diameter of 5 mm and a height of 50 mm or the like on the central axis of the cylindrical electrode 1 placed. In this case, 4 to 8 through holes of diameters of about 1 mm may be formed on the circumference. This particular example of the size of the cylindrical electrode 1 is just an example. The invention is not limited to this.

The gas supply connections 10 are in an isolator 20th provided and placed on the upper chamber. The gas outlet connections 11 are in an isolator 21 provided and placed on the lower chamber. The gas supply connections 10 and the gas outlet connections 11 can be placed at arbitrary locations of the upper chamber and the lower chamber, respectively. The top and bottom isolator 20th , 21 and the cylindrical electrode 1 can be sealed by a seal or packing, O-rings, etc. The rod-shaped electrode can be anchored with a chuck or a clamping device, etc. The center of the chuck or jig is formed to match the axial center of the inner circumference of the cylindrical electrode 1 to match. A plurality or multiplicity of gas outlet connections are located around this axial center 11 arranged radially.

The pressure of the gas coming from the gas supply connections 10 is 300 Pa to 101 kPa. As the gas, any one or a combination of two or more of a noble gas, a hydrocarbon and an oxygen gas can typically be used. Furthermore, any one or a combination of two or more of Ar, He, N ₂ , O ₂ , H ₂ , CH ₄ , C ₂ H ₂ , C ₂ H ₄ , C ₃ H ₈ , CF ₄ , C ₂ F ₆ , SF ₆ , SiH ₄ , SiH ₃ Cl, S ₁ H _{2 Cl 2} , Si (CH ₃ ) ₄ and (CH ₃ ) ₃ Si-NH-Si (CH ₃ ) _{3 can be} appropriately selected in accordance with the layer which to be formed, or the surface treatment of the target.

Gas flows from the upper first chamber 2 through the holes in the panel 4th to the lower second chamber 3 . Even while it is spreading, it moves in all directions, but under a pressure of 100 Pa or more, the diffusion causes the effect of increasing the gas flow. The charges move mainly through the flow of the gas. The pressure of the second chamber 3 is less than the pressure of the first chamber 2 . The pressure of the second chamber 3 is set to a pressure of 300 Pa to 101 kPa.

In this way, in the present invention, plasma is generated in a separate location from the inherently desired plasma chamber. The electrons and ions that are generated there due to the glow discharge, the thermions of the plasma, which are generated by the arc discharge, etc., are used and introduced into the desired plasma chamber or supplied to the desired plasma chamber. Because of this, glow plasma can be generated and maintained even with a lower electrical field.

Next, the operation of the first embodiment of the present invention will be explained.

The cylindrical chamber of the plasma generator is ^{evacuated to 1 × 10 -2} Pa or less by a rotating pump or rotary vane pump (turbo-molecular pump, cryopump and the like are also possible), then the layer formation surface is created by supplying Ar gas from the gas supply connections 10 cleaned. A voltage (100 V to 5 kV) is applied to the rod-shaped electrode from a DC pulse energy source 5 applied to generate a plasma, collisions of Ar ions with the rod-shaped electrode 5 and the cylindrical electrode 1 to cause and activate the film formation surface. In this case, an electrical discharge or spark erosion of the first chamber can also occur 2 be used.

Inside the first chamber 2 is a sub-electrode 6th which is able to apply a potential different from the cylindrical electrode 1 is placed. By applying an electric field to the lower electrode 6th creates the first chamber 2 Plasma. After that, the rod-shaped electrode 5 supplied with an electric field by a pulse energy source, therefore plasma is also in the other second chamber 3 generated. To form a layer, a material of CH4 or other hydrocarbon-based gas, etc. is supplied, the pressure is adjusted to 300 Pa to 101 kPa, and plasma is generated to form a layer. In this way it is possible to form a stable plasma on narrow, small electrode components and to generate a high-density plasma.

As an illustration, there may be a case of coating the surface of the rod-like electrode 5 may be mentioned with a DLC, but the invention is not limited thereto. The invention is not limited to the formation of a wear-resistant layer or a layer with high lubricity properties. The gas used and the applied voltage are appropriately selected in accordance with the surface treatment (removal of impurities or improvement), the formation of the thin layer, the etching or other treatment.

As another embodiment of the present invention, the following modification can be considered. 2 Fig. 13 is a conceptual view showing another embodiment of the present invention.

Inside the second chamber 3 is a cylindrical body 12th placed to be conductive with the cylindrical electrode 1 to be. The central axis of the inner peripheral surface of the cylindrical body 12th is on the central axis of the cylindrical electrode 1 placed. As explained above, plasma is generated in the same way as in the first embodiment. In this case, it becomes the inner peripheral surface of the cylindrical body 12th treated. As an example, there can be mentioned the case of coating the same with a DLC. It should be noted that the invention is not limited to this. It is not limited to the formation of a wear-resistant layer or a layer with high sliding properties. The gas used and the applied voltage are appropriately selected in accordance with the surface treatment (removal of impurities or improvement), the formation of the thin film, the etching or other treatment.

Claims (7)

Plasma generator, which is equipped with a cylindrical chamber component, which has a cylindrical electrode (1), a screen (4) which is arranged in the cylindrical chamber component, around the cylindrical chamber component in a first chamber (2) which has gas supply connections (10) , and a second chamber (3) which has gas outlet connections (11) to subdivide, a rod-shaped electrode (5) which is placed inside the second chamber (3) on a central axis of the cylindrical electrode (1), and a sub-electrode ( 6), which is placed on the first chamber (2) and is able to apply a potential different from that of the cylindrical electrode (1), wherein the plasma generator applies an electric field between the cylindrical electrode (1) and the rod-shaped electrode (5) in order to generate a plasma, further applying an electric field separately between the cylindrical electrode (1) and the sub-electrode (6) to generate a plasma separately from the plasma generated between the rod-shaped electrode (5) and the cylindrical electrode (1), and which has plasma areas of the first chamber (2) and the second chamber (3) which are connected by the holes in the diaphragm (4), wherein the plasma generated between the rod-shaped electrode (5) and the cylindrical electrode (1) is a glow discharge, and the plasma generated between the cylindrical electrode (1) and the sub-electrode (6) is a glow discharge or is an arc discharge, and wherein a pressure of the second chamber (3) is a pressure of 300 Pa to 101 kPa. Plasma generator after Claim 1 , wherein a pressure of the second chamber (3) is lower than a pressure of the first chamber (2). Plasma generator after Claim 1 wherein a gas supplied from the gas supply ports (10) is either a rare gas, hydrocarbon, and oxygen gas, or a combination of two or more types thereof. Plasma generator after Claim 1 , wherein a gas which is supplied from the gas supply connections (10) is either Ar, He, N ₂ , O ₂ , H ₂ , CH ₄ , C ₂ H ₂ , C ₂ H ₄ , C ₃ H ₈ , CF ₄ , C ₂ F ₆ , SF ₆ , SiH ₄ , SiH ₃ Cl, SiH ₂ Cl ₂ , Si (CH ₃ ) ₄ and (CH ₃ ) ₃ Si-NH-Si (CH ₃ ) _3, or a combination of two or more types is the same. Plasma generator according to one of the Claims 1 until 4th which coats a surface of the rod-shaped electrode (5) with a diamond-like carbon. Plasma generator according to one of the Claims 1 until 4th which places a cylindrical body (12) inside the second chamber (3) to be conductive with the cylindrical electrode (1), and wherein a central axis of an inner peripheral surface of the cylindrical body (12) is on a central axis of the cylindrical electrode (1 ) is placed. Plasma generator after Claim 6 coating the inner peripheral surface of the cylindrical body (12) with a diamond-like carbon.

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