JP5032042B2 - Plasma CVD apparatus and film forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma CVD apparatus capable of performing the uniform film deposition in a more extensive range than the plasma size. <P>SOLUTION: The plasma CVD apparatus comprises a chamber 10 with a substrate 5 arranged therein, a tubular member 20 having an opening part 18 opened in the chamber 10 so as to be opposite to the substrate 5, a plasma generator 24 for generating plasma into the tubular member 20, and a raw material gas feeder 22 for feeding a raw material gas to the tubular member 20. The inside diameter d of the opening part 18 of the tubular member 20 is smaller than the outside diameter D of the substrate 5. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a plasma CVD apparatus and a film forming method.

  Since carbon nanotubes (hereinafter referred to as “CNT”) have chemical stability and emit electrons in a low electric field, they are used for, for example, field emission display (FED) devices. Applied to electron sources.

A technique for producing this CNT by a plasma CVD method has been proposed (see, for example, Patent Document 1). In this technique, the substrate is first placed in a vacuum chamber maintained at a certain degree of vacuum. Next, a raw material gas composed of hydrocarbon gas and hydrogen gas is introduced into the vacuum chamber. Then, plasma is generated in the vacuum chamber, and the source gas decomposed by the plasma is brought into contact with the substrate surface. Thereby, CNT is produced on the substrate surface.
JP 2005-350342 A

  However, when a CNT is produced by arranging a substrate inside or below the plasma as in the above method, it is strongly influenced by the size and density distribution of the plasma. That is, almost no CNT is produced on the substrate surface outside the plasma size. Moreover, it is very difficult to generate a large plasma with microwaves. If the plasma density distribution is not uniform, the height and orientation state of the produced CNTs are not uniform.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a plasma CVD apparatus and a film forming method capable of forming a film uniformly over a range wider than the plasma size.

In order to achieve the above object, a plasma CVD apparatus according to the present invention is a plasma CVD apparatus for growing carbon nanotubes on a substrate to be processed, and is connected to the chamber in which the substrate to be processed is disposed, the chamber, A tubular member having an opening opening in the chamber so as to face the substrate to be processed; a plasma generator for generating plasma in the tubular member; and a raw material gas for supplying a raw material gas to the tubular member An inner diameter of the opening of the tubular member is smaller than an outer diameter of the substrate to be processed, and a porous plate is disposed in the opening and applied to the porous plate. The voltage is −400 to 200V.
Moreover, it is desirable that the plasma generator generate plasma by introducing a microwave into the tubular member made of a quartz material.
In order to generate plasma inside the tubular member, it is desirable that a magnetic field supply means is provided in the tubular member.
In this plasma CVD apparatus, plasma having a size equal to or smaller than the inner diameter of the tubular member can be generated, and active species generated by the plasma can be blown out from the opening into the chamber. As a result, active species are also emitted around the opening, so that the active species can be incident on the peripheral portion of the substrate to be processed. Therefore, uniform film formation can be performed in a wider range than the plasma size.
Further, in this plasma CVD apparatus, since the porous plate is disposed in the opening of the tubular member, the inside of the tubular member can be set at a higher pressure than the inside of the chamber. This pressure difference causes a gas flow from the tubular member toward the chamber. At that time, it is desirable that the porous plate be held in the same electrical state as the metal mesh plate.

The source gas supply device preferably supplies the source gas to the tubular member on the opposite side of the chamber across the plasma generation position.
According to this configuration, a gas flow from the plasma generation position toward the chamber is generated. Thereby, the active species generated at the plasma generation position can be blown out from the opening into the chamber.

Further, it is desirable that a porous plate is disposed in the opening.
According to this configuration, the inside of the tubular member can be set to a higher pressure than the inside of the chamber. Thereby, the active species generated inside the tubular member can be blown out from the perforated plate into the chamber.

In addition, it is desirable that the plasma generator generate plasma by introducing a microwave into the tubular member made of a quartz material.
According to this configuration, even when the plasma size generated by the microwave is small, uniform film formation can be performed over a wider range. In addition, the active species generated by the plasma generated by the microwave has a larger amount of radicals than the plasma generated by the RF. Therefore, it is possible to form a film on the substrate surface using radicals while suppressing the etching effect due to the incidence of ions.

In order to generate plasma inside the tubular member, it is desirable that a magnetic field supply means is provided in the tubular member .

On the other hand, the film forming method according to the present invention is a plasma CVD apparatus for growing carbon nanotubes on a substrate to be processed, the chamber in which the substrate to be processed is disposed, the chamber connected to the chamber, and the substrate to be processed includes a tubular member having an opening which opens into said chamber so as to face, the inner diameter of the opening of the tubular member, the formed smaller than the outer diameter of the substrate to be processed, before Symbol opening A film forming method using a plasma CVD apparatus provided with a perforated plate, wherein a raw material gas is supplied to the tubular member, plasma is generated inside the tubular member, and active species generated by the plasma are produced. by blowing through the opening into the interior of said chamber, and wherein when performing a film forming process on a substrate to be processed, a voltage of -400~200V to the perforated plate That.
Further, in order to generate plasma inside the tubular member, it is desirable to use a magnetic field supply means provided in the tubular member.
According to this configuration, active species are also emitted around the opening, so that the active species can be incident on the peripheral portion of the substrate to be processed. Therefore, uniform film formation can be performed in a wider range than the plasma size.

  According to the plasma CVD apparatus according to the present invention, plasma can be generated inside the tubular member, and the generated active species can be blown out from the opening into the chamber and incident on the substrate to be processed. Therefore, uniform film formation can be performed in a wider range than the plasma size.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size.

(First embodiment)
FIG. 1 is a schematic configuration diagram of a plasma CVD apparatus according to the first embodiment. The plasma CVD apparatus 1 according to the first embodiment includes a chamber 10 in which a substrate 5 to be processed is disposed, and an opening 18 connected to the chamber 10 and opening in the chamber 10 so as to face the substrate 5 to be processed. A tubular member 20, a plasma generator 24 that generates plasma inside the tubular member 20, and a raw material gas supply device 22 that supplies a raw material gas to the tubular member 20, and the inner diameter of the opening 18 of the tubular member 20. However, it is formed smaller than the outer diameter of the substrate 5 to be processed.

(Plasma CVD equipment)
The plasma CVD apparatus 1 includes a sealed chamber 10. Inside the chamber 10 is provided a stage 12 on which a substrate to be processed (hereinafter simply referred to as “substrate”) 5 is placed. A heater (not shown) that controls the temperature of the substrate 5 is provided inside the stage 12. Further, an evacuation device 14 such as a rotary pump or a turbo molecular pump is connected to the chamber 10 in order to depressurize the inside of the chamber 10.

  A tubular member 20 is connected to the chamber 10. The material of the tubular member 20 is arbitrary, but when plasma is generated by microwaves as described later, it is desirable that the tubular member 20 be made of quartz or the like that can introduce microwaves from the outside. Moreover, although the tubular member 20 is formed in the fixed internal diameter d along the axial direction, the part from which an internal diameter differs may be provided in a part of axial direction. The tubular member 20 includes an opening 18 that opens into the chamber 10 so as to face the substrate 5 to be processed. The inner diameter d of the opening 18 is smaller than the outer diameter D of the substrate 5 to be processed.

  A metal mesh plate 16 having a plurality of holes is disposed between the opening 18 of the tubular member 20 and the stage 12 on which the substrate 5 is placed. The metal mesh plate 16 functions as plasma shielding means, is made of a metal material such as stainless steel, and has a plurality of holes having a diameter of about 1 to 3 mm. The metal mesh plate 16 is held in an electrically floating state or held at a ground potential. When carbon nanotubes (hereinafter referred to as “CNT”) are grown on the surface of the substrate 5, a bias is applied between the metal mesh plate 16 and the stage 12 in order to grow CNTs perpendicular to the surface of the substrate 5. A power supply for applying voltage may be connected. In this case, for example, the distance between the metal mesh plate 16 and the substrate 5 may be about 20 to 100 mm, and the bias voltage may be about −400 to 200V.

A plasma generator 24 is provided at an intermediate portion in the axial direction of the tubular member 20. For the generation of plasma, RF (13.56 MHz), microwave (2.45 GHz), or the like can be used. However, if more radicals than ions are used in the film formation reaction, the amount of radicals generated is large. It is desirable to use waves. In addition, by using a microwave with a short wavelength, it is possible to generate plasma in a relatively localized region, and it is possible to generate plasma with a large electron kinetic energy. Furthermore, if the magnetic field by the magnetic field supply means provided in the tubular member 20 is applied to the generation of the plasma, the plasma can be stably generated at a low pressure. The plasma generator 24 using a microwave includes a microwave generator and a waveguide that connects the microwave generator to a tubular member, and generates plasma inside the tubular member 20 at the connection position of the waveguide. It is supposed to let you.

  Since the plasma generating device is provided on the tubular member 20 connected to the chamber 10 and the metal mesh plate 16 is provided between the tubular member 20 and the substrate 5, the plasma generation position and the substrate 5 are spaced apart. be able to. Accordingly, it is possible to suppress the substrate 5 from being heated by receiving energy from the plasma, and the temperature of the substrate 5 can be controlled by the heater provided on the stage 12. Further, it is possible to prevent the substrate 5 from being damaged due to damage from ions generated by the plasma.

  A raw material gas supply device is connected to the end of the tubular member 20 on the opposite side of the chamber 10 across the plasma generation position. That is, the source gas supply device is connected upstream from the plasma generation position. In addition, when growing CNT on the surface of the substrate 5, a carbon-containing gas is employed as a source gas. As a specific carbon-containing gas, it is possible to employ a vaporized alcohol in addition to a hydrocarbon gas such as methane, ethylene, and acetylene. In particular, it is desirable to employ methane gas that does not decompose at the substrate heating temperature. Note that at least one of hydrogen gas, ammonia, nitrogen gas, and argon is mixed with the carbon-containing gas and used for dilution of the carbon-containing gas and as a catalyst for CNT growth. The source gas supply device 22 is configured to be able to supply these gases.

(Film formation method)
Next, a film forming method using the plasma CVD apparatus 1 according to the first embodiment will be described. Here, a case where CNT is grown on the surface of the substrate 5 will be described as an example. CNT grows on transition metals such as Ni, Fe, and Co, or alloys containing these transition metals. Therefore, as the substrate 5, a substrate made of the above metal or a substrate in which a film made of the above metal is formed on a substrate of glass, quartz, Si or the like is adopted. In addition, if the coating film made of the metal is formed only in a partial region on the substrate, CNTs can be selectively grown only in the partial region.

  As a specific film forming method, first, the substrate 5 is placed on the stage 12 in the chamber 10, and the substrate 5 is heated to, for example, about 300 to 700 ° C. by a heater provided on the stage 12. Next, the inside of the chamber 10 is decompressed by operating the vacuum exhaust device 14. Next, the source gas is supplied from the source gas supply device 22 into the tubular member 20. As a source gas, for example, a mixed gas of methane gas and hydrogen gas is supplied. Next, the plasma generator 24 is driven to introduce microwaves into the tubular member 20. Thereby, plasma having a size equal to or smaller than the inner diameter of the tubular member 20 is generated. The source gas is excited by this plasma, and active species such as radicals and ions are generated.

  By the way, by supplying the source gas upstream of the plasma generation position, a gas flow from the plasma generation position toward the chamber 10 is generated. The active species generated at the plasma generation position diffuses on the gas flow and blows out into the chamber 10 from the opening 18 of the tubular member 20. Further, the plasma itself diffuses and blows out from the opening 18 into the chamber 10. As a result, active species are also emitted around the opening 18 having the inner diameter d, so that the active species can also enter the peripheral portion of the substrate 5 having the outer diameter D (> d). Therefore, even when the plasma size d generated by the microwave is small, uniform film formation can be performed in a wider range D.

  Of the active species blown out from the opening 18, ionic species are captured by the metal mesh plate 16 disposed between the opening 18 and the substrate 5, so that radicals can be mainly incident on the substrate 5. it can. Thereby, it is possible to grow CNTs perpendicular to the surface of the substrate 5 while suppressing the etching effect due to the incidence of ions. In addition to this, it is desirable to use active species excluding ionic species in the reaction by controlling the bias voltage applied to the substrate 5, the electric field and magnetic field in the apparatus, and the like.

(Second Embodiment)
FIG. 2 is a schematic configuration diagram of a plasma CVD apparatus according to the second embodiment. The plasma CVD apparatus 2 according to the second embodiment is different from the first embodiment in that the internal pressure of the tubular member 20 can be set higher than the internal pressure of the chamber 10. Note that detailed description of portions having the same configuration as in the first embodiment is omitted.

(Plasma CVD equipment)
In the second embodiment, the porous plate 17 is disposed in the opening 18 of the tubular member 20. The perforated plate 17 is formed by forming a plurality of small-diameter holes in a metal plate such as stainless steel. The perforated plate 17 only needs to be held in the same electrical state as the metal mesh plate of the first embodiment.
In the second embodiment, the raw material gas supply device 22 is connected to the tubular member 20 between the plasma generation position and the chamber 10. That is, the source gas supply device 22 is connected to the downstream side of the plasma generation position in the tubular member 20. The source gas supply device 22 may be connected to the upstream side from the plasma generation position as in the first embodiment.

(Film formation method)
Next, a film forming method using the plasma CVD apparatus 2 according to the second embodiment will be described. First, the vacuum exhaust device 14 is operated to decompress the inside of the chamber 10. Next, the source gas is supplied from the source gas supply device 22 into the tubular member 20. Here, since the porous plate 17 is disposed in the opening 18 of the tubular member 20, the inside of the tubular member 20 can be set to a higher pressure than the inside of the chamber 10. This pressure difference causes a gas flow from the tubular member 20 toward the chamber 10.

  Next, the plasma generator 24 is driven to generate plasma inside the tubular member 20. The active species generated by this plasma is diffused by the above-described gas flow and blown out from the perforated plate 17 into the chamber 10. The plasma itself diffuses and blows out from the perforated plate 17 into the chamber 10. As a result, active species are also emitted around the opening 18 having the inner diameter d, so that the active species can also enter the peripheral portion of the substrate 5 having the outer diameter D (> d). Therefore, even when the plasma size d generated by the microwave is small, uniform film formation can be performed in a wider range D.

  In Example 1, CNTs were grown on the substrate using the plasma CVD apparatus according to the first embodiment. In the plasma CVD apparatus 1 shown in FIG. 1, the tubular member 20 has an inner diameter d of 50 mm and a length of 150 mm. The distance between the connection position of the plasma generator 24 to the tubular member 20 and the opening 18 was set to 100 mm. The distance between the tubular member 20 and the metal mesh plate 16 was 30 mm, and the distance between the metal mesh plate 16 and the substrate 5 was 20 mm.

The outer diameter D of the substrate 5 was 100 mm, which is twice the inner diameter d of the tubular member 20. As the substrate 5, a 1-nm-thick Fe film formed on a silicon substrate by EB vapor deposition was employed. The metal mesh plate 16 was set at ground potential, the stage was set to -100 to 200 V, and a bias voltage was applied to the substrate. Further, the substrate 5 was heated to 600 ° C. by the heater of the stage 12. As source gases, CH ₄ gas was supplied at 20 sccm, H ₂ gas was supplied at 80 sccm, and 2.0 Torr from the source gas supply device 22. Further, a 500 W microwave was introduced into the tubular member 20 from the plasma generator 24 to generate plasma.

  As a result, uniform CNTs could be grown on the entire surface of the substrate 5 having an outer diameter of 100 mm. Specifically, CNTs having a height of about 11 μm could be grown perpendicular to the substrate 5 at both the central position of the substrate 5 and the position of about 5 mm from the substrate edge. When the outer diameter D of the substrate 5 is 100 mm (twice the inner diameter d of the tubular member 20), the CNT height variation in each part of the substrate 5 is within ± 5%, and the outer diameter D of the substrate 5 is 125 mm. In the case of (2.5 times the inner diameter d of the tubular member 20), the CNT height variation was within ± 10%. The same result as above was obtained when the internal pressure of the tubular member was in the range of 1 to 10 Torr, but the lower pressure was better.

In Example 2, CNTs were grown on the substrate using the plasma CVD apparatus according to the second embodiment. At that time, the internal pressure of the chamber was 1 Torr or less, the internal pressure of the tubular member was 10 Torr or less, and the other reaction conditions were the same as in Example 1.
As a result, uniform CNTs could be grown on the entire surface of the substrate. Even when the source gas was supplied to the upstream side of the plasma generation position, uniform CNTs could be grown on the entire surface of the substrate in the same manner as when the source gas was supplied to the downstream side of the plasma generation position.
(Comparative Example 1)

In Comparative Example 1, CNTs were grown on the substrate using the plasma CVD apparatus 101 shown in FIG.
FIG. 3 is a schematic configuration diagram of a plasma CVD apparatus according to Comparative Example 1. The plasma CVD apparatus 101 includes a quartz window 120 on the upper surface of the chamber 110. The quartz window 120 has an outer diameter of about 200 mm, which is the same as the outer diameter of the substrate 105. A microwave can be introduced into the entire surface of the quartz window 120 from the outside of the quartz window 120. A source gas supply device 122 is connected to the upper side of the chamber 110. Further, a metal mesh plate 116 is disposed between the upper portion of the chamber 110 serving as a plasma generation position and the lower portion of the chamber 110 where the stage 112 on which the substrate 105 is placed is disposed. The distance between the metal mesh plate 116 and the substrate 105 is set to 20 mm, and both the metal mesh plate 116 and the stage 112 are at ground potential.

In Comparative Example 1, the substrate 105 having an outer diameter of 200 mm was employed. Then, a source gas was supplied from the side surface of the chamber 110 and a 2 kW microwave was introduced from the quartz window 120 to generate plasma having a diameter of about 200 mm.
As a result, the CNT could be grown to a height of about 6 μm at the center position of the substrate 5, but the CNT could only be grown to a height of about 2 μm at a position 10 mm from the edge of the substrate.

  From the above results, as in the present invention, by generating plasma smaller in size than the substrate inside the tubular member and blowing it out into the chamber, it is possible to form a uniform film on the entire surface of the substrate. confirmed. On the other hand, it was confirmed that even if plasma having the same size as the substrate was generated in the chamber, it was difficult to form a uniform film on the entire surface of the substrate.

It should be noted that the technical scope of the present invention is not limited to the above-described embodiments, and includes those in which various modifications are made to the above-described embodiments without departing from the spirit of the present invention. That is, the specific materials and configurations described in the embodiments are merely examples, and can be changed as appropriate.
For example, in the present embodiment, the case where CNT is grown on the substrate surface has been described as an example. However, the present invention can also be applied to the case where a film other than CNT is formed on the substrate surface. 1 and 2, the apparatus is configured such that the substrate is disposed below the plasma. However, the apparatus may be configured such that the substrate is disposed above or on the side of the plasma.

1 is a schematic configuration diagram of a plasma CVD apparatus according to a first embodiment. It is a schematic block diagram of the plasma CVD apparatus which concerns on 2nd Embodiment. 2 is a schematic configuration diagram of a plasma CVD apparatus according to Comparative Example 1. FIG.

Explanation of symbols

  d ... plasma size (inner diameter of opening) D ... outer diameter of substrate 1,2 ... plasma CVD apparatus 5 ... substrate (substrate to be processed) 10 ... chamber 12 ... stage 16 ... metal mesh plate 17 ... perforated plate 18 ... opening DESCRIPTION OF SYMBOLS 20 ... Tubular member 22 ... Raw material gas supply device 24 ... Plasma generator

Claims (6)

A plasma CVD apparatus for growing carbon nanotubes on a substrate to be processed,
A chamber in which the substrate to be processed is disposed;
A tubular member connected to the chamber and having an opening that opens into the chamber so as to face the substrate to be processed;
A plasma generator for generating plasma inside the tubular member;
A source gas supply device for supplying source gas to the tubular member,
The inner diameter of the opening of the tubular member is smaller than the outer diameter of the substrate to be processed,
A plasma CVD apparatus, wherein a porous plate is disposed in the opening, and a voltage applied to the porous plate is −400 to 200V.   2. The plasma CVD apparatus according to claim 1, wherein the source gas supply apparatus supplies the source gas to the tubular member on the opposite side of the chamber across the generation position of the plasma.   The plasma CVD apparatus according to claim 1 or 2, wherein the plasma generation apparatus generates plasma by introducing a microwave into the tubular member made of a quartz material.   The plasma CVD apparatus according to any one of claims 1 to 3, wherein a magnetic field supply means is provided in the tubular member in order to generate plasma in the tubular member. A plasma CVD apparatus for growing carbon nanotubes on a substrate to be processed,
A chamber in which the substrate to be processed is disposed;
A tubular member connected to the chamber and provided with an opening that opens into the chamber so as to face the substrate to be processed;
The inner diameter of the opening of the tubular member, the formed smaller than the outer diameter of the substrate to be processed, even before Symbol film forming method using the plasma CVD apparatus perforated plate is provided in the opening portion,
A raw material gas is supplied to the tubular member, plasma is generated inside the tubular member, and active species generated by the plasma are blown out from the opening into the chamber to form a film on the substrate to be processed. When processing ,
A film forming method, wherein a voltage of −400 to 200 V is applied to the porous plate .   The film forming method according to claim 5, wherein a magnetic field supply unit provided in the tubular member is used to generate plasma inside the tubular member.

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