JP2008150681A - Apparatus for forming film by direct-current plasma - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for forming a film by direct-current plasma, which inhibits an occurrence of overdischarge on an electrode face of a cathode or on an insulation film of a cooling plate, by preventing electrons from being charged up in a carbon component even when the carbon component in a decomposing gas has deposited on the electrode face of the cathode or on the insulation film, and can form a carbon film that has uniform film thickness, high film quality and superior performance as a field electron emission source. <P>SOLUTION: The apparatus for forming the film by direct-current plasma has a cathode 12 and an anode 14 arranged inside a vacuum film-forming chamber 10 so that both electrode faces are opposed to each other. The cathode 12 is mounted on a region 16a for mounting the cathode thereon, which is set in the approximately middle of a cooling plate 16. An insulation film 18 is formed annularly on a circumferential region 16b which surrounds the perimeter of the region 16a annularly for mounting the cathode thereon in the cooling plate 16. The cathode 12 is made of a molybdenum material, and has a discharge-inhibiting material 36 made of the molybdenum material provided on the insulation film 18. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, a direct current negative voltage is applied to the cathode to generate direct current plasma in the vicinity of the electrode surface of the anode to decompose the gas for forming the carbon film, and the back surface of the substrate is disposed on the electrode surface of the anode. The present invention relates to a direct current plasma deposition (CVD) apparatus for depositing a carbon film having a size of the order of nm, which has field electron emission performance as a field electron emission source on the surface of a substrate.

  A conventional DC plasma film forming apparatus will be described with reference to FIG. 7. The conventional DC plasma film forming apparatus has a vacuum film forming chamber 10. The cathode 12 and the anode 14 are arranged at predetermined positions in the vacuum film forming chamber 10 so that the electrode surfaces 12a and 14a face each other in parallel at a predetermined interval.

  A cooling plate 16 made of a metal such as SUS is disposed in close contact with the back surface 12b of the cathode 12 in a heat conductive coupling state. The cooling plate 16 is for cooling the cathode 12 by heat conduction, and is configured to have a larger planar dimension and a larger plate thickness than the cathode 12 to increase the cooling capacity.

  The cooling plate 16 has a substantially central region as a cathode mounting region 16a on the surface on which the cathode 12 is mounted, and an outer peripheral region 16b outside the cathode mounting region 16a. Since the cooling plate 16 generates plasma only between the cathode 12 and the anode 14, an insulating film 18 made of ceramic, for example, is formed on the outer peripheral surface excluding the cathode mounting region 16a.

  As the material of the cathode 12, metals such as SUS, Fe, Cu, and Al are used. The vacuum film forming chamber 10 is grounded. The anode 14 is grounded, and the cathode 12 is connected to the negative electrode of the DC power supply 20. The positive electrode of the DC power supply 20 is grounded via the power switch 22. When the power switch 22 is closed, a negative DC voltage is applied to the cathode 12. In addition, a gas introduction system 24 and a vacuum exhaust system 26 are connected to the vacuum film forming chamber 10.

  In the DC plasma film forming apparatus having the above configuration, the internal pressure of the vacuum film forming chamber 10 is controlled to a required vacuum pressure by the evacuation system 26, and the source gas is introduced into the vacuum film forming chamber 10 by the gas introduction system 24. A mixed gas of hydrocarbons as hydrogen and hydrogen as a carrier gas is introduced.

  In this state, when a DC negative voltage is applied to the cathode 12 from the DC power supply 20, plasma 28 is generated near the electrode surface 14 a of the anode 14. The mixed gas is decomposed by the plasma 28, and the carbon component in the decomposed gas is deposited on the surface of the substrate 30 disposed on the electrode surface 14a of the anode 14 with the back surface of the substrate facing, and as a result. A carbon film serving as a field electron emission source is formed on the surface of the substrate 30.

  However, in the DC plasma film forming apparatus, when the pressure in the vacuum film forming chamber 10 is a low pressure lower than the required vacuum level, not only the plasma 28 between the cathode 12 and the anode 13 but also the cooling plate 16 as shown in FIG. The plasma 29 is also spread and generated on the outer peripheral region 16b.

  For this reason, part 32 and 33 of the carbon component in the gas decomposed by the plasmas 28 and 29 are deposited in stripes or the like on the electrode surface 12 a of the cathode 12, its side surface 12 c, and the insulating film 18.

  In this case, conventionally, metals such as SUS, Fe, Cu, and Al are used as the material of the cathode 12, and therefore the carbon component 32 deposited on the electrode surface 12a and the side surface 12c is non-conductive. In addition, the carbon component 33 deposited in a stripe pattern on the insulating film 18 is also non-conductive.

  At this time, since the carbon components 32 and 33 are non-conductive, the carbon components 32 and 33 are charged with electrons. Then, the plasmas 28 and 29 which are generated at a low density and large when the pressure in the vacuum film forming chamber 10 is low are reduced and become smaller as the pressure increases.

  When the amount of electrons charged up to the carbon components 32 and 33 exceeds a threshold value, the charge-up electrons may discharge (arc discharge) 34 and 35 toward the electrode surface 14a of the anode 14.

  When the abnormal discharges 34 and 35 are strong, the plasma 28 disappears as shown in FIG. 9, and when the abnormal discharges 34 and 35 are partially generated, the plasma 28 is deformed as shown in FIG. When the abnormal discharges 34 and 35 are weak, the plasma 28 is reduced as shown in FIG.

The above abnormal discharges 34 and 35 affect the performance of the carbon film as a field electron emission source as a result of the carbon film not being formed on the surface of the substrate 30 or being unevenly formed and the quality of the carbon film being deteriorated. End up. Patent Document 1 and the like are provided as a direct-current plasma film forming apparatus.
JP 2006-283970 A

  Therefore, the present invention provides a direct current plasma film forming apparatus capable of forming a carbon film having excellent performance with uniform film thickness and high quality as a field electron emission source by suppressing the occurrence of abnormal discharge described above. It is a problem to be solved.

  In the DC plasma film forming apparatus according to the present invention, a cathode and an anode are disposed in a vacuum film forming chamber with their electrode surfaces facing each other, and the cathode is mounted on a cathode mounting region set at a substantially center of a cooling plate. In addition, in the DC plasma film forming apparatus in which the insulating film is formed in an annular shape on the outer peripheral region surrounding the outer periphery of the cathode mounting region in the cooling plate, at least the electrode surface of the cathode is made of molybdenum material or the A molybdenum material is deposited on at least the electrode surface of the cathode, and a discharge preventing material made of molybdenum material is provided on the insulating film.

  The cathode includes both the case where only the electrode surface is made of molybdenum material, the case where the electrode surface and side surfaces are made of molybdenum material, and the case where the whole cathode is made of molybdenum material. The cathode may not be made of molybdenum material, but may be deposited only on the electrode surface, or on the electrode surface and side surfaces.

  The discharge preventing material on the insulating film has a disk shape (disk shape or the like) extending from between the cathode mounting region and the cathode back surface to the outer peripheral edge of the insulating film, or the outer peripheral edge of the cathode mounting region as the inner diameter. It is good also as an annular. The discharge preventing material may have a shape with a constant thickness in the radial direction or a shape with a gradually decreasing thickness.

  The molybdenum material and the discharge preventing material constituting the cathode can be integrated or separated.

  The planar view shape (the shape when viewed from the plane direction) of the back surface of the cathode includes both a circle and a rectangle, and the planar view shape of the surface of the cooling plate includes both a circle and a rectangle.

  The planar shape of the discharge preventing material varies depending on the planar shape of the cathode and the planar shape of the cooling plate, for example, a disc shape, a rectangular plate shape, a disc shape, a rectangular disc shape, an annular plate shape, etc. .

  The molybdenum material is not limited to a material made only of molybdenum, and can contain alloys with other metals as long as the molybdenum contains high purity.

  The film material of the insulating film is not particularly limited, but is preferably ceramic.

  In this DC plasma deposition apparatus, the anode is grounded and a negative DC voltage is applied to the cathode to generate plasma in the space between the cathode and the anode. The introduced gas is decomposed by the plasma, and the carbon component generated by the decomposition is formed as a field electron emission source on the surface of the substrate disposed on the anode.

  In this case, low-density plasma is generated not only between the cathode and the anode but also on the discharge preventing material even when the internal pressure of the vacuum film forming chamber is a low pressure equal to or lower than the predetermined vacuum pressure. As a result, the gas is decomposed to generate a carbon component, and a part of the carbon component is deposited in stripes on the outer peripheral surface of the cathode and the discharge preventing material. When the vacuum film forming chamber pressure reaches the predetermined vacuum pressure, the plasma is reduced, and high-density plasma is generated in the vicinity of the electrode surface of the anode. At this time, since the carbon component deposited in the above-described stripe shape is made of a molybdenum material and the cathode and the discharge prevention material are made conductive, electrons are not charged up to the stripe-like carbon component. Thus, the charged electrons do not affect the film formation of the substrate disposed on the electrode surface of the anode.

  Therefore, in the present invention, since the discharge preventing material on the cathode and the insulating film is made of molybdenum material, the carbon component decomposed by the plasma in the vicinity of the electrode surface of the anode has a uniform film thickness and high quality on the substrate surface. A carbon film having excellent performance as a field electron emission source is deposited by film quality.

  According to the present invention, a carbon film as a field electron emission source can be formed on the substrate surface with a uniform film thickness and high quality.

  Hereinafter, a DC plasma film forming apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing a configuration of a DC plasma film forming apparatus according to an embodiment. In the figure, 10 is a vacuum film forming chamber, 12 is a cathode, 14 is an anode, 16 is a cooling plate, 18 is an insulating film, 20 is a DC power source, 22 is a power switch, 24 is a gas introduction system, 26 is a vacuum exhaust system, 28 is a film forming plasma, and 30 is a substrate. The said board | substrate 30 is not limited to the shape, For example, not only circular in cross section but non-circles, such as an ellipse and a rectangle, are included. The substrate 30 includes a flat substrate, a linear substrate, and the like. The linear shape does not limit the size of the diameter, and can include a wire-like concept.

  In the above-described configuration, the DC plasma film forming apparatus is characterized in that the entire cathode 12 is made of a molybdenum material, and the discharge preventing material 36 made of a disk-shaped molybdenum material is disposed between the cathode 12 and the cooling plate 16. It is what.

  In the above, the entire cathode 12 is made of molybdenum material. However, only the electrode surface 12a of the cathode 12 or the electrode surface 12a and the side surface 12c are made of molybdenum material having a predetermined thickness, or the electrode surface 12a of the cathode 12 is made. Molybdenum material may be applied to the upper surface or the electrode surface 12a and the side surface 12c.

  The discharge preventing material 36 has a flat plate shape or a disk shape, and has an outer diameter larger than the outer diameter of the cathode 12 and extends on the insulating film 18. The discharge preventing material 36 may be disposed so as to extend to an intermediate portion of the insulating film 18 or to the outer peripheral edge of the insulating film 18.

  In the following, in the vacuum film forming chamber 10, a cathode 12 and an anode 14 are arranged with their electrode surfaces facing each other in parallel. The cathode 12 is mounted on the cathode mounting area 16 a of the cooling plate 16. The discharge preventing material 36 has a disk shape that covers the insulating film 18 on the outer peripheral region 16b from the cathode mounting region 16a of the cooling plate 16.

  In the DC plasma film forming apparatus having the above configuration, the internal pressure of the vacuum film forming chamber 10 is reduced by the evacuation system 26, and a mixed gas of hydrocarbon and hydrogen is supplied into the vacuum film forming chamber 10 by the gas introduction system 24. When the DC negative voltage is applied to the cathode 12 from the DC power source 20, as shown in FIG. 2, when the vacuum pressure in the vacuum film forming chamber 10 is low, the space between the cathode 12 and the anode 14 and the insulating film 18 are reduced. Large but low density plasmas 28 and 29 are generated. The gas is decomposed by the plasmas 28 and 29, and the carbon components 32 and 33 in the gas are deposited on the outer peripheral surface of the cathode 12 and the insulating film 18 in various pattern shapes such as islands, stripes, and particles. Come to come.

  When the vacuum pressure in the vacuum film forming chamber 10 is controlled to be high, the plasmas 28 and 29 are reduced as shown in FIG. 3, and the plasma 29 is reduced to a level that can be substantially ignored, so that only the plasma 28 is obtained. . This plasma 28 is generated in the vicinity of the electrode surface 14 a of the anode 14 and becomes a plasma in which a carbon film serving as a field electron emission source is deposited on the surface of the substrate 30.

  In this case, since the cathode 12 is made of molybdenum material and the discharge preventing material 36 made of molybdenum material is disposed on the insulating film 18, the carbon films 32 and 33 are conductive. , 33 is not charged up with electrons, so that no discharge occurs from the carbon films 32, 33. As a result, the plasma 28 in the vicinity of the electrode surface 14a of the anode 14 is maintained at high quality and high density. As a result, carbon having excellent film quality and uniform quality as a field electron emission source on the surface of the substrate 30 is obtained. A film is formed. This carbon film consists of a needle-like carbon film (a carbon film that has a needle shape with a diameter decreasing toward the tip), and emits electrons with high performance and high efficiency by concentrating the electric field on a large number of fine protrusions. The source.

  The molybdenum material composing the cathode 12 and the molybdenum material composing the discharge preventing material 36 preferably have a high purity of 99% or more. If molybdenum is included in high purity, a molybdenum alloy alloyed with another metal may be used in order to improve functions such as high temperature characteristics.

  As molybdenum, single crystal high purity molybdenum is more preferable. Molybdenum has a large electric field multiplication factor β and is excellent in the field electron emission characteristics from the surface of the cathode 12 under a direct current high electric field.

  The cathode 12 and the discharge prevention plate 36 may be made of a solid integrated molybdenum material as shown in FIG.

  Alternatively, as shown in FIG. 5, a hollow discharge preventing material 40 in which the cathode side discharge preventing material 38 made of molybdenum covering the outer peripheral surface of the cathode 12 and the insulating film side discharge preventing material 36 are integrated may be used. .

  Alternatively, as shown in FIG. 6, it may be constituted by an annular plate-shaped discharge preventing material 42 made of molybdenum material surrounding the outer periphery of the cathode 12 made of molybdenum material.

  The present invention is not limited to the above-described embodiments, and includes various changes or modifications within the scope described in the claims.

FIG. 1 is a cross-sectional view showing a configuration of a DC plasma film forming apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the DC plasma film forming apparatus of FIG. 1 during operation. FIG. 3 is a cross-sectional view of the main part when the vacuum film forming chamber pressure of the DC plasma film forming apparatus is low. FIG. 4 is a diagram illustrating a configuration example of the cathode and the discharge preventing material. FIG. 5 is a diagram showing another configuration example of the cathode and the discharge preventing material. FIG. 6 is a diagram showing still another configuration example of the cathode and the discharge preventing material. FIG. 7 is a cross-sectional view of a conventional DC plasma film forming apparatus. FIG. 8 is a cross-sectional view of a conventional DC plasma film forming apparatus in operation. FIG. 9 is a cross-sectional view when a strong abnormal discharge occurs from the cathode to the anode of the conventional DC plasma film forming apparatus. FIG. 10 is a cross-sectional view when a partial abnormal discharge occurs from the cathode to the anode of a conventional DC plasma film forming apparatus. FIG. 11 is a cross-sectional view for explaining a problem when a weak abnormal discharge occurs from the cathode to the anode of the conventional DC plasma film forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Vacuum film-forming chamber 12 Cathode 12a Electrode surface 12b Side surface 12c Back surface 14 Anode 14a Electrode surface 16 Cooling plate 16a Cathode mounting area 16b Outer peripheral area 18 Insulating film 20 DC power supply 28 Plasma 29 Plasma 30 Substrate 32 Carbon component 33 Carbon component 36-42 Discharge prevention material

Claims (5)

  A direct current plasma film forming apparatus in which a cathode and an anode are arranged in a vacuum film forming chamber with their electrode surfaces facing each other in parallel, and the cathode is mounted on a cooling plate having at least the cathode side surface coated with an insulating film. Wherein at least the electrode surface of the cathode is made of molybdenum material, or a molybdenum material is deposited on at least the electrode surface of the cathode, and a discharge preventing material made of molybdenum material is provided on the insulating film. A direct current plasma film forming apparatus.   2. The DC plasma deposition apparatus according to claim 1, wherein the cathode is entirely made of a molybdenum material.   The discharge preventing material is formed in a plate shape or a plate shape including a cathode mounting region and an outer peripheral region of a cooling plate, and is interposed between the cooling plate and the cathode. Item 3. The direct-current plasma deposition apparatus according to Item 1 or 2.   The DC plasma film forming apparatus according to claim 1, wherein the discharge preventing material is formed in an annular plate shape covering an insulating film.   5. The direct-current plasma film forming apparatus according to claim 1, wherein the cathode and the discharge preventing material are integrated.

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