阅读说明：本技术 通电加热丝的制造方法以及制造装置 (Method and apparatus for manufacturing electric heating wire ) 是由 山田龙藏 青代信 浅利伸 于 2021-05-24 设计创作，主要内容包括：本发明提供一种能够在表面均匀地形成碳化钽的通电加热丝的制造方法以及制造装置。在本发明的一个方式所涉及的通电加热丝的制造方法中,向设置有钽丝的腔室导入乙炔气体,所述钽丝具有两个端部并以在垂直方向上折回的方式悬挂,一边控制导入所述腔室内的所述乙炔气体的供给量而使所述腔室的内压变化,一边通电加热所述钽丝,对所述钽丝的表面进行碳化处理。(The invention provides a method and an apparatus for manufacturing an electric heating wire capable of uniformly forming tantalum carbide on the surface. In a method of manufacturing an energization heating wire according to an aspect of the present invention, acetylene gas is introduced into a chamber in which a tantalum wire having two end portions and suspended so as to be folded back in a vertical direction is provided, and the tantalum wire is energized and heated while changing an internal pressure of the chamber by controlling a supply amount of the acetylene gas introduced into the chamber, thereby carbonizing a surface of the tantalum wire.)

1. A method for manufacturing an electric heating wire, wherein,

introducing acetylene gas into a chamber provided with a tantalum wire having both ends and suspended in a folded manner in a vertical direction,

while changing the internal pressure of the chamber by controlling the supply amount of the acetylene gas introduced into the chamber, the tantalum wire is electrically heated to carbonize the surface of the tantalum wire.

2. The manufacturing method of an energizing heating wire according to claim 1,

the internal pressure of the chamber is changed by repeating the rise and fall of the internal pressure of the chamber.

3. The manufacturing method of an energizing heating wire according to claim 2,

intermittently introducing the acetylene gas into the chamber.

4. The manufacturing method of an energizing heating wire according to claim 1 or 2, wherein,

the internal pressure of the chamber is changed by controlling the amount of exhaust gas in the chamber in addition to the amount of acetylene gas supplied.

5. A manufacturing apparatus having:

a chamber in which a tantalum wire having two ends is suspended to be folded back in a vertical direction;

an acetylene gas supply unit which introduces acetylene gas into the chamber;

a control unit that controls an internal pressure of the chamber by controlling a supply amount of the acetylene gas introduced into the chamber to change the internal pressure of the chamber; and the number of the first and second groups,

and a power supply that supplies power for heating the tantalum wire to the tantalum wire so as to carbonize the surface of the tantalum wire while changing the internal pressure of the chamber in an acetylene gas atmosphere.

6. The manufacturing apparatus according to claim 5,

the control unit controls the amount of the discharged gas in the chamber to change the internal pressure of the chamber in addition to the amount of the supplied acetylene gas.

Technical Field

The present invention relates to a method and an apparatus for manufacturing an electric heating wire used in, for example, a catalytic wire chemical vapor deposition method.

Background

There is a film formation method such as Catalytic Chemical Vapor Deposition (Cat-CVD). The film forming method of the method is as follows: for example, a reactive gas is supplied to a catalytic wire heated to 1500 to 2000 ℃, and a decomposed species (deposition species) generated by a contact reaction or a thermal decomposition reaction of the reactive gas is deposited on a film formation substrate.

The catalytic chemical vapor deposition method is similar to the plasma CVD method in that decomposed species of the reaction gas are deposited on the substrate to form a film. However, since the catalytic chemical vapor deposition method generates decomposition species of a reaction gas on a high-temperature catalytic wire, the catalytic chemical vapor deposition method includes, as compared with a plasma CVD method that generates decomposition species of a reaction gas by forming a plasma: no surface damage caused by plasma and high utilization efficiency of the raw material gas.

Tantalum is widely used as a material for a catalytic wire used in the catalytic chemical vapor deposition method. However, since metallic tantalum itself has low creep strength at high temperatures, if metallic tantalum is used as it is as a catalytic wire, it thermally elongates and fuses when heated. Therefore, in the case of using tantalum as a catalytic wire, a method of melting and hardening tantalum by subjecting tantalum to a boride treatment or a carbonization treatment can be used.

For example, patent document 1 discloses an electric current heating wire which is formed by introducing a carbon source gas into a vacuum chamber in which a tantalum wire is provided and applying a voltage to the tantalum wire, and which has a core portion made of tantalum and a peripheral portion made of tantalum carbide covering the core portion.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2012 and 41576.

Problems to be solved by the invention

In the case of film formation on a substrate by a catalytic chemical vapor deposition method or the like, an energizing heater wire having tantalum carbide uniformly formed on the surface thereof is required in order to form a film having uniform characteristics over the entire surface of the substrate.

Disclosure of Invention

In view of the above circumstances, an object of the present invention is to provide a method and an apparatus for manufacturing an energization heating wire capable of uniformly forming tantalum carbide on the surface thereof.

Means for solving the problems

In order to achieve the above object, in a method for manufacturing an electric conduction heating wire according to one aspect of the present invention,

introducing acetylene gas into a chamber provided with a tantalum wire having both ends and suspended in a manner folded back in a vertical direction,

while changing the internal pressure of the chamber by controlling the supply amount of the acetylene gas introduced into the chamber, the tantalum wire is electrically heated to carbonize the surface of the tantalum wire.

In this configuration, by performing the carbonization treatment while varying the internal pressure of the chamber, tantalum carbide can be uniformly formed on the surface of the tantalum wire over the entire length of the tantalum wire.

The internal pressure of the chamber may be changed by repeating the increase and decrease of the internal pressure of the chamber.

The acetylene gas may be intermittently introduced into the chamber.

The internal pressure of the chamber may be changed by controlling the amount of the discharged gas in the chamber, in addition to the amount of the acetylene gas supplied.

A manufacturing apparatus according to an embodiment of the present invention includes a chamber, an acetylene gas supply unit, a control unit, and a power supply.

The chamber is provided with a tantalum wire with two end parts in a suspended manner in the chamber in a mode of folding back in the vertical direction;

the acetylene gas supply unit introduces acetylene gas into the chamber.

The control unit controls the internal pressure of the chamber by controlling the amount of acetylene gas supplied into the chamber to change the internal pressure of the chamber.

The power supply supplies power for heating the tantalum wire to the tantalum wire so that the surface of the tantalum wire is carbonized while changing the internal pressure of the chamber in an acetylene gas atmosphere.

In this configuration, the carbonization of the tantalum wire can be performed while changing the internal pressure of the chamber, and therefore tantalum carbide can be uniformly formed on the surface of the tantalum wire over the entire length of the tantalum wire.

The control unit may control the amount of the acetylene gas supplied and may control the amount of the exhaust gas in the chamber to change the internal pressure of the chamber.

Effects of the invention

As described above, according to the present invention, it is possible to provide a method and an apparatus for manufacturing an energization heating wire capable of uniformly forming tantalum carbide on the surface of a tantalum wire over the entire length of the tantalum wire.

Drawings

Fig. 1 is a schematic configuration diagram of a manufacturing apparatus of an energization heating wire according to an embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view of an electric heating wire manufactured by the manufacturing apparatus.

Fig. 3 is a flowchart showing a method of manufacturing the energization heating wire.

Fig. 4 is a schematic view of an energization heating wire manufactured by performing carbonization treatment without changing the internal pressure of the vacuum chamber using the manufacturing apparatus.

Fig. 5 is a schematic view of an energization heating wire manufactured by carbonizing while changing the internal pressure of a vacuum chamber using the manufacturing apparatus.

Fig. 6 is a schematic diagram for explaining a carbonization mechanism of a tantalum wire and a mechanism in which unevenness of the carbonization process occurs.

Fig. 7 is a schematic diagram for explaining a mechanism in which unevenness of the carbonization treatment occurs in the manufacturing apparatus.

Fig. 8 is a graph showing a relationship between a time length and a tantalum wire temperature when the acetylene gas atmosphere is set to the first internal pressure.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[ Structure of manufacturing apparatus ]

Fig. 1 is a schematic configuration diagram of a catalytic wire manufacturing apparatus 1 as an energization heating wire according to an embodiment of the present invention. By carbonizing the surface of the tantalum wire 60 using the manufacturing apparatus 1, the catalytic wire 6 can be manufactured as an energization heating wire having tantalum carbide formed on the surface.

The manufacturing apparatus 1 comprises a vacuum chamber 3, a vacuum pump 4, an exhaust line 5, a first switch valve 7, a power supply 8, and acetylene gas (C) as a carbon source supply unit₂H₂) A supply section 9, an exhaust gas control section 10 as a first control section, a second on-off valve 11, a gas supply line 14, and a gas supply control section 15 as a second control section.

The vacuum chamber 3 is configured to be able to house a plurality of tantalum wires 60 therein.

A vacuum pump 4 as an exhaust unit is connected to the vacuum chamber 3 through an exhaust line 5. The vacuum pump 4 can vacuum-exhaust the vacuum chamber 3 to a predetermined degree of vacuum.

The exhaust line 5 connects the vacuum pump 4 and the vacuum chamber 3.

A first on-off valve 7 is provided on the exhaust line 5.

The exhaust control unit 10 controls the opening and closing of the first on-off valve 7, and controls the exhaust speed and the exhaust time in the vacuum chamber 3.

The acetylene gas supply unit 9 supplies acetylene gas into the vacuum chamber 3 through a gas supply line 14.

The gas supply line 14 connects the acetylene gas supply unit 9 and the vacuum chamber 3.

The second on-off valve 11 is provided on the gas supply line 14.

The gas supply controller 15 controls the opening and closing of the second on-off valve 11, and adjusts the amount and time of introduction of the acetylene gas into the vacuum chamber 3. In the present embodiment, during the carbonization treatment, the gas supply controller 15 controls the opening and closing of the second on-off valve 11 to control the supply amount of the acetylene gas introduced into the vacuum chamber 3 so as to change the internal pressure of the vacuum chamber 3. Thereby, the internal pressure of the vacuum chamber 3 is changed at the time of carbonization.

Further, the internal pressure of the vacuum chamber 3 during the carbonization treatment may be adjusted by controlling the amount of the discharged gas in the vacuum chamber 3 in addition to the amount of the acetylene gas supplied. The exhaust gas amount is controlled by controlling the opening and closing of the first on-off valve 7 by the exhaust gas control unit 10.

The tantalum wire 60 is made of metallic tantalum and has a rod shape. Each tantalum wire 60 having both ends hangs down in the vertical direction (in the present embodiment, the direction of gravity) in the vacuum chamber 3, and is suspended in the vacuum chamber 3 so as to be folded back in the vertical direction in the lower region in the vacuum chamber 3. The plurality of tantalum wires 60 are arranged in a straight line at predetermined intervals. In the following description, the arrangement direction of the plurality of tantalum wires 60 is referred to as "X-axis direction", the vertical direction is referred to as "Z-axis direction", and the direction perpendicular to these is referred to as "Y-axis direction".

Note that, although the tantalum wires 60 are arranged in about 8 sets, for example, fig. 1 shows a case where the tantalum wires 60 are arranged in 3 sets for convenience of explanation.

The length of the tantalum wire 60 differs depending on the size of a substrate to be film-formed by a catalytic chemical vapor deposition method using the catalytic wire 6 formed by carbonizing the surface of the tantalum wire 60. For example, a single catalytic filament 6 having a length of 2m to 6m is used. The length of the catalytic wire 6 is preferably 2m to 5m, and in the present embodiment, a tantalum wire 60 having a length of 4.5m before the carbonization treatment of the catalytic wire 6 is used. The tantalum wire 60 has the same length as the catalytic wire 6 formed by carbonizing the surface of the tantalum wire 60.

As shown in fig. 1, in one tantalum wire 60, the tantalum wire 60 is configured such that the lengths of the two connection terminals 64 of the tantalum wire 60 to the folded back portions are equal to each other. More specifically, in the present embodiment, the tantalum wire 60 (catalytic wire 6) is folded back and arranged in the vacuum chamber 3 so that the length of the folded back portion, that is, the portion extending in the X-axis direction is 120mm, and the length of the portions extending in the Z-axis direction on both sides of the folded back portion is 2200 mm.

The power supply 8 supplies electric power to the catalytic wire 6, and the catalytic wire 6 is electrically heated by continuous energization. Both ends of the catalytic wire 6 are connected to a power supply 8.

In the carbonization treatment, the tantalum wire 60 is heated while changing the internal pressure of the vacuum chamber 3 in the acetylene gas atmosphere, and the surface thereof is carbonized, whereby the catalytic wire 6 having tantalum carbide uniformly formed on the surface can be obtained. Details will be described later.

The manufacturing apparatus 1 is configured as described above.

[ Structure of catalytic filament (energized heating wire) ]

Next, the structure of the catalytic wire 6 will be explained. Fig. 2 is a sectional view schematically showing a sectional structure of the catalytic wire 6. As described above, the catalytic wire 6 is formed by carbonizing the surface of the tantalum wire 60. The catalytic wire 6 has a core portion 6a and a peripheral portion 6 b. The core portion 6a is a central portion of the catalytic wire 6, and the peripheral portion 6b is an outer peripheral portion of the catalytic wire covering the core portion 6 a. The core portion 6a is made of metallic tantalum (Ta), and the peripheral portion 6b is made of tantalum carbide (TaC)_x) And (4) forming.

Since metallic tantalum has low creep strength at high temperatures, catalytic wires made of metallic tantalum alone may thermally elongate and fuse during film formation. In contrast, in the catalytic wire 6 according to the present embodiment, the core portion 6a made of metallic tantalum is covered with the peripheral portion 6b made of tantalum carbide having high creep strength at high temperatures and high mechanical strength, so that the thermal durability and mechanical durability of the catalytic wire 6 can be improved. Specifically, although the catalytic wire made of only tantalum metal often needs to be replaced every time a film is formed, the catalytic wire 6 according to the present embodiment can be used for a plurality of film formation without being replaced.

On the other hand, tantalum carbide is less conductive (has a higher resistance) than metal tantalum, and a catalytic wire made of tantalum carbide alone requires a higher electric power when heated. In contrast, in the catalytic wire 6 according to the present embodiment, since the core portion 6a made of metallic tantalum is provided inside the cross-sectional structure, the electrical conductivity is high (the electrical resistance is low), and the catalytic wire can be heated with an applied voltage of the same level as that of the catalytic wire made of metallic tantalum alone.

Further, tantalum carbide has high stability against chemical reaction, and therefore boron used in a film formation step or the like in a catalytic chemical vapor deposition method using a catalytic wire can be prevented from diffusing into the core material. This prevents the core material from locally increasing in resistance due to boronation of tantalum, prevents the core material from fusing due to a temperature rise, and improves the durability of the core material. Therefore, the life of the catalytic wire can be extended.

[ method for producing catalytic wire (Electrical heating wire) ]

Using the manufacturing apparatus 1, the tantalum wire 60 is heated and the surface thereof is carbonized while changing the internal pressure of the vacuum chamber 3 in the acetylene gas atmosphere, and the catalytic wire 6 having tantalum carbide uniformly formed on the surface thereof can be obtained by the following method. The following describes the manufacturing flow of fig. 3.

One or more tantalum wires 60 as a raw material of the catalytic wire 6 are provided inside the vacuum chamber 3 of the manufacturing apparatus 1 (S11). The tantalum wire 60 is a wire made of metal tantalum, and the diameter thereof can be several mm, here 1.0 mm. The vacuum pump 4 is operated to evacuate the inside of the vacuum chamber 3 and reduce the pressure in the vacuum chamber 3. The pressure here was reduced to less than 0.05 Pa.

Next, acetylene gas is supplied from the acetylene gas supply unit 9 to the vacuum chamber 3. A voltage is applied from the power supply 8 to each tantalum wire 60 while changing the internal pressure of the vacuum chamber 3 in an acetylene gas atmosphere, thereby performing a carbonization treatment of the surface of the tantalum wire 60 (S12).

Each tantalum wire 60 is heated by resistance heating by the applied voltage. The power supplied to the tantalum wire 60 is adjusted according to the desired heating temperature, and may be, for example, 40A or 6.8kW of dc power. Acetylene (C) passing through the surface of the tantalum wire 60₂H₂) The peripheral portion 6b made of tantalum carbide as a reaction product is formed on the surface of the tantalum wire 60. That is, the catalytic wire 6 having the wire-shaped core portion 6a made of tantalum and the peripheral portion 6b covering the core portion 6a made of tantalum carbide is manufactured.

The change in the internal pressure of the vacuum chamber 3 during the carbonization treatment will be described with reference to fig. 5 (a).

The upper diagram of fig. 5(a) is a schematic diagram of the catalytic wire 6 manufactured by the manufacturing method of the present embodiment, and the lower diagram shows changes with time of the electric power supplied to the tantalum wire 60, which is the raw material of the catalytic wire 6, and the internal pressure of the vacuum chamber 3 during the carbonization process in manufacturing the catalytic wire 6.

Changing the internal pressure of the vacuum chamber 3 in the acetylene gas atmosphere means changing the concentration of acetylene gas in the vacuum chamber 3. In the present embodiment, the internal pressure is changed so that the supply amount of acetylene gas into the vacuum chamber 3 is changed with time, and the increase and decrease of the internal pressure of the vacuum chamber 3 are repeated alternately. Specifically, the supply amount of acetylene gas was changed by alternately supplying at 500sccm for 1 minute and at 0sccm for 1 minute repeatedly. In other words, the internal pressure is changed by intermittently supplying acetylene gas. When the supply amount of acetylene gas is 500sccm, the concentration of acetylene gas in the vacuum chamber 3 increases. When the supply amount is 0sccm, the acetylene gas concentration in the vacuum chamber 3 decreases. In the lower graph of fig. 5(a), the change in the internal pressure of the vacuum chamber 3 is schematically shown.

Hereinafter, the internal pressure of the vacuum chamber 3 at the time of carbonization is set to be a first internal pressure when the internal pressure is high, and a second internal pressure when the internal pressure is low. During the carbonization treatment, the internal pressure of the vacuum chamber 3 changes so that the first internal pressure and the second internal pressure alternate repeatedly. The first internal pressure is, for example, 1.0 Pa. The second internal pressure is lower than 1.0Pa, preferably 0.1Pa or lower, and in the present embodiment, 0.01Pa or lower. The treatment time was set to 20 minutes. The treatment time is a carbonization treatment time. 10 minutes out of the treatment time 20 minutes is the total time when the internal pressure of the vacuum chamber 3 is the first internal pressure. The remaining 10 minutes is the sum of the time during which the internal pressure of the vacuum chamber 3 becomes the second internal pressure.

As shown in fig. 5(a), during the carbonization treatment, the tantalum wire 60 is electrically heated. During the carbonization treatment, the first internal pressure in the vacuum chamber 3 is 1.0X 10^-5m³Exhausting at an exhaust rate of 1.0X 10 at the second internal pressure^-4m³Exhaust velocity of/s.

By performing the carbonization treatment while changing the internal pressure of the vacuum chamber 3 in the acetylene gas atmosphere, as shown in the upper diagram of fig. 5(a), the catalytic wire 6 in which tantalum carbide is uniformly formed on the surface over the entire length of the tantalum wire 60 can be obtained.

The tantalum wire 60 is heated at a temperature of 1000 ℃ or higher, and when the carbon concentration at the time of carbon infiltration into the tantalum wire is about 30 atomic% or higher, a carbonization reaction of tantalum occurs.

For example, the heating temperature of the tantalum wire 60 can be set in a range of 1800 ℃ to 2400 ℃. Here, the dc current value is set to 40A, but the dc current value is not limited to this, and can be set in a range of 10A to 60A, for example. The dc power is set to 6.8kW, but the dc power is not limited to this, and can be set to a range of 3kW to 10kW, for example. These numerical values are merely examples, and can be changed as appropriate depending on the thickness and length of the tantalum wire.

The treatment time is appropriately set according to the heating temperature of the tantalum wire 60. Under otherwise identical conditions, the higher the heating temperature, the more the formation of tantalum carbide is promoted. In other cases, the longer the heating time, the more the formation of tantalum carbide is promoted.

Here, the first internal pressure is set to 1.0Pa, but the present invention is not limited thereto, and can be set to a range of 1.0Pa to 10Pa, for example. Under otherwise identical conditions, the greater the pressure of the carbon atmosphere, the more promoted the formation of tantalum carbide.

Here, a case where the tantalum wire is carbonized while the internal pressure of the vacuum chamber 3 is kept constant will be described with reference to fig. 4. FIGS. 4 (A) to (D) are schematic views of catalytic wires 71 to 74 as comparative examples. The catalytic filaments 71 to 74 shown in fig. 4 (a) to (D) were produced by using the above-described production apparatus 1 during production thereof, while keeping the internal pressure of the vacuum chamber 3 constant during carbonization treatment and varying the pressure and treatment time of the acetylene gas atmosphere. The production was carried out by supplying 40A, 6.8kW of DC power to the tantalum wire 60, heating the wire, and carbonizing the wire for each of the catalytic wires 71 to 74.

Fig. 4 (a) is a schematic view of a catalytic wire 71 produced with an acetylene gas atmosphere of 10Pa and a treatment time of 30 minutes.

Fig. 4 (B) is a schematic view of a catalytic wire 72 produced with an acetylene gas atmosphere set to 10Pa and a treatment time set to 5 minutes.

Fig. 4 (C) is a schematic view of a catalytic wire 73 produced with an acetylene gas atmosphere set at 1.0Pa and a treatment time set at 30 minutes.

Fig. 4 (D) is a schematic view of a catalytic wire 74 produced with an acetylene gas atmosphere set at 1.0Pa and a treatment time set at 5 minutes.

In each of the catalytic wires 71 to 74 shown in fig. 4, the unfilled region is a region where tantalum carbide is formed and is yellow; in a region indicated by oblique lines obliquely upward and rightward, carbon (carbon) is precipitated and appears black; the area indicated by oblique right-downward oblique lines indicates orange color in the state where carbon deposition is just started. The region that appears black is referred to as a blackened region. The orange region is a state before blackening, and is referred to as an orange region.

As shown in fig. 4 (a) to (D), when the carbonization treatment is performed in a state where the internal pressure of the vacuum chamber 3 is constant, the catalytic wires 71 to 74 partially deposit carbon and exhibit black color, and thus a catalytic wire in which tantalum carbide is uniformly formed on the surface over the entire length of the tantalum wire 60 cannot be obtained.

Further, as shown in (A) to (D) of FIG. 4, the carbon deposition region is remarkably present in the upper part of the suspended catalytic wires 71 to 74. This is because, in the manufacturing apparatus 1, supply of acetylene gas to the vacuum chamber 3 is performed in the upper part of the manufacturing apparatus 1, and exhaust of the inside of the vacuum chamber 3 is performed in the lower part of the manufacturing apparatus 1, and a spatial concentration distribution of acetylene gas appears in the vacuum chamber 3.

The mechanism of occurrence of uneven formation of tantalum carbide (hereinafter referred to as "carbonization unevenness") in the carbonized catalytic wire in a state where the internal pressure of the vacuum chamber 3 is kept constant is as follows. The following description will be made with reference to fig. 6 and 7.

Fig. 6 is a schematic diagram for explaining a carbonization mechanism of a tantalum wire and a mechanism in which unevenness of the carbonization process occurs. In fig. 6, reference numeral 12 denotes carbon, and reference numeral 13 denotes hydrogen.

Fig. 7 is a schematic view for explaining the state of the tantalum wire 60 in the manufacturing apparatus 1 when the carbonization treatment is performed with the internal pressure of the vacuum chamber 3 kept constant, and for explaining the mechanism of occurrence of unevenness in the carbonization treatment.

The mechanism of carbonization of tantalum wire is explained.

As shown in fig. 6, in the carbonization treatment of the surface of the tantalum wire 60, the tantalum wire 60 is heated by applying power to the tantalum wire 60. As indicated by reference numeral 19, the acetylene contacts the tantalum wire 60 and pyrolysis of hydrogen occurs, thereby producing carbon 12 and hydrogen 13. The carbon 12 infiltrates the tantalum wire 60 and diffuses, forming tantalum carbide on the surface of the tantalum wire 60 by reacting with tantalum.

Next, a mechanism of occurrence of unevenness in carbonization treatment will be described with reference to fig. 6 and 7.

As shown in (a) of fig. 7, as described above, in the manufacturing apparatus 1, the spatial concentration distribution of acetylene gas occurs. In fig. 7 (a), the higher the density of dots, the higher the concentration of acetylene gas. As shown in fig. 7 (a), in the manufacturing apparatus 1, the upper portion side has a higher concentration of acetylene gas than the lower portion side. Accordingly, in the early stage of the reaction, in the carbonization treatment of the tantalum wire 60, more carbon is infiltrated into the upper portion side than the lower portion side of the tantalum wire 60, and the degree of carbonization is higher. Therefore, the resistance value of the tantalum wire increases due to the formation of tantalum carbide, and the resistance values of the upper portion and the lower portion of the tantalum wire 60 change. The upper part side has a larger potential difference than the lower part side.

Here, the diffusion of the carbon 12 in the tantalum wire 60 becomes slower as it penetrates from the surface to the center of the tantalum wire 60. Therefore, in the next stage of the reaction, as shown by the position indicated by reference numeral 20 in fig. 6, the carbon 12 is clogged in the region close to the surface in the tantalum wire 60, so that it is difficult to smoothly carburize the wire, and the carbon is excessively supplied, so that the carbon 12 is deposited on the surface of the tantalum wire 60 and appears black. The precipitated carbon 12 is bonded to hydrogen 13 to form CH having-polarity as at the position indicated by reference numeral 21_X. The CH having-polarity, as shown in fig. 7 (B), at the position indicated by reference numeral 22 in fig. 6_XIs attracted to the + pole side of the tantalum wire 60. Thus, CH_XMost of the gas concentrates on the plus electrode side of the upper portion of the tantalum wire 60, which has a higher gas concentration distribution than the lower portion, and the carbon concentration in this portion becomes high. In fig. 7 (B), a region where the carbon concentration is particularly high is indicated by dots.

In a further stage of the reaction, as shown in FIG. 7 (C), in CH_XOf a plurality of concentrated tantalum wires 60The plus electrode side on the upper side was smoothly carburized and carbonized, and the resistance value was further improved. As the resistance value increases, the heat generation temperature of the tantalum wire 60 also increases. As a result, for example, in fig. 7 (C), the heating temperature is different between the area on the plus electrode side on the upper side of the tantalum wire 60 indicated by the triple-hatched line and the area on the minus electrode side on the upper side of the tantalum wire 60 indicated by the double-hatched line, and the resistance distribution and the temperature distribution appear over the entire length of the tantalum wire 60.

In the further stage of the reaction, as shown in (D) of fig. 7, non-uniformity in the formation of tantalum carbide occurs due to the occurrence of the temperature distribution. The region above the plus electrode side of the tantalum wire 60 was carbonized. No carbonization was performed in the upper region of the-electrode side of the tantalum wire 60, and carbon was precipitated and appeared black. Once blackened, the temperature drop is accelerated. Accordingly, the temperature difference between the plus side and the minus side becomes larger, the degree of progress of carbonization becomes more different, and the tantalum formation on the surface becomes uneven over the entire length of the tantalum wire 60.

On the other hand, in fig. 7 (a) to (D), the regions below the imaginary broken line 80 are regions where the concentration of acetylene gas is relatively low, and the tantalum wire located in the regions does not have a distribution of resistance, does not have a variation in carbon concentration, and does not have a variation in formation of tantalum carbide.

Referring back to fig. 4, when the tantalum wire is carbonized while the internal pressure of the vacuum chamber 3 is kept constant, the area of deposited carbon varies depending on the process conditions. The production conditions of the catalytic wires 71 to 74 shown in fig. 4 (a) to (D) are as described above.

As shown in fig. 4 (a) and (B), the range of the blackened area differs depending on the treatment time in the same acetylene gas atmosphere (10 Pa). As shown in the figure, the range of the blackened area is smaller as the confirmation processing time is shorter.

As shown in fig. 4 (a) and (C), the blackening region differs depending on the acetylene gas atmosphere at the same treatment time. As shown in the figure, the smaller the pressure of the acetylene gas, the smaller the range of the blackened area, and becomes an orange area as a stage before the blackened at the-electrode side. In this way, it was confirmed that the unevenness in formation of tantalum carbide occurring over the entire length of the tantalum wire 60 was reduced by further reducing the pressure of acetylene gas, but the unevenness in carbonization treatment still occurred.

As shown in fig. 4 (C) and (D), the blackened area differs depending on the treatment time in the same acetylene gas atmosphere (1.0 Pa). As shown in fig. 4 (D), the orange region disappeared, and it was confirmed that the unevenness in formation of tantalum carbide occurred over the entire length of the tantalum wire 60 was reduced by shortening the treatment time, but the unevenness in carbonization still occurred.

Fig. 5 is a diagram illustrating an example of a case where the carbonization treatment is performed by changing the internal pressure of the vacuum chamber 3 by controlling the supply amount of acetylene gas so that the first internal pressure is 1.0Pa and the second internal pressure is 0.01Pa or less and alternately switching the first internal pressure and the second internal pressure. Specifically, the supply amount of acetylene gas was continuously changed in such a manner that 500sccm and 0sccm were alternately performed with the lapse of time. Acetylene gas was introduced into the vacuum chamber 3, and the carbonization treatment was started when the pressure in the vacuum chamber 3 reached 1.0 Pa.

The upper diagrams of (a) to (C) in fig. 5 show catalytic wires 6, 75, and 76 produced by carbonization while changing the internal pressure of the vacuum chamber 3, and they are produced with different times for once reaching the first internal pressure. The graphs shown on the lower sides of (a) to (C) in fig. 5 show the processing conditions in the production of the catalytic wire shown on the upper side of the graph, and show the temporal changes in the electric power supplied to the tantalum wire 60 as the raw material of the catalytic wire and the internal pressure of the vacuum chamber 3.

Fig. 5(a) shows the catalytic wire 6 in the present embodiment, and fig. 5 (B) and (C) show the catalytic wires 75 and 76 in the comparative example.

In the production of the catalytic wires 6, 75, and 76 shown in fig. 5(a) to (C), respectively, the production apparatus 1 was used to perform electric heating while dc power supplied to the tantalum wire 60, which is a raw material of the catalytic wire, was set to 40A and 6.8 kW. In any of the catalytic wires 6, 75, and 76, the total time of the first internal pressure of the vacuum chamber 3 during the carbonization treatment is 10 minutes.

In the production of the catalytic wire 6 shown in fig. 5(a), the internal pressure of the vacuum chamber 3 was changed by alternately repeating the supply of the first internal pressure for 1 minute and the supply of the second internal pressure for 1 minute, and the carbonization treatment was performed for a total carbonization treatment time of 20 minutes.

In the production of the catalytic wire 75 shown in fig. 5 (B), the internal pressure of the vacuum chamber 3 was changed by supplying the pressure at the first internal pressure for 5 minutes, the second internal pressure for 5 minutes, and the first internal pressure for 5 minutes in this order, and the carbonization treatment time was performed for a total of 15 minutes.

In the production of the catalytic wire 76 shown in fig. 5 (C), the internal pressure of the vacuum chamber 3 was changed by supplying the internal pressure at the first internal pressure for 5 minutes, supplying the internal pressure at the second internal pressure for 30 minutes, and supplying the internal pressure at the first internal pressure for 5 minutes in this order, and the carbonization treatment time was performed for a total of 40 minutes.

In each of the catalytic wires 75 and 76 in fig. 5 (B) and (C), the unfilled region is a region in which tantalum carbide is formed and appears yellow; the region indicated by oblique upper right oblique lines is a black region in which carbon precipitates and appears black.

As shown in (a) to (C) of fig. 5, even if the total of the times during which the vacuum chamber 3 has the first internal pressure is the same during the carbonization treatment time, regardless of the length of the time during which the vacuum chamber 3 has the second internal pressure, if the length of the time during which the vacuum chamber has the first internal pressure at one time is five minutes, a blackened area is generated, and the carbonization treatment is not uniform.

On the other hand, as shown in fig. 5(a), when the length of the time for which the first internal pressure is obtained once is set to 1 minute, which is shorter than 5 minutes shown in fig. 5 (B) and (C), the catalytic wire in which tantalum carbide is uniformly formed on the surface over the entire length of the tantalum wire can be obtained.

In this way, by shortening the length of time for which the first internal pressure is once reached and changing the internal pressure of the vacuum chamber 3 so that the first internal pressure and the second internal pressure alternate with each other, it is possible to obtain a catalytic wire in which tantalum carbide is uniformly formed on the surface over the entire length of the tantalum wire.

The reason for this is considered to be that clogging of carbon is alleviated at the position indicated by reference numeral 20 in the description using fig. 6. That is, it can be considered that: since the supply amount of carbon is reduced by shortening the time of the first internal pressure and the supply amount of carbon is further reduced by changing the first internal pressure to the second internal pressure, clogging of carbon is alleviated, and carburizing becomes difficult, and as a result, precipitation of carbon is suppressed.

As described above, it is considered that the CH is generated by the combination of hydrogen and carbon deposited on the surface of the tantalum wire due to the spatial concentration distribution of the acetylene gas in the production apparatus 1 and the blockage of carbon_XEtc., resulting in non-uniform formation of tantalum carbide.

As shown in the present embodiment, even if the spatial concentration distribution of the acetylene gas occurs in the production apparatus 1, the internal pressure of the vacuum chamber 3 is changed so as to alternate between the first internal pressure and the second internal pressure and the carbonization treatment is performed while shortening the time taken for the single change to the first internal pressure, thereby alleviating the clogging of carbon and obtaining a catalytic wire in which tantalum carbide is uniformly formed on the surface over the entire length of the tantalum wire.

The length of time for which the first internal pressure is once reached can be appropriately set according to the value of the first internal pressure and the heating temperature of the tantalum wire. The description will be given with reference to fig. 8.

Fig. 8 is a graph showing the results of measurement of process conditions under which tantalum carbide is not unevenly formed in the carbonization process of tantalum wire.

The solid line curve shown in the graph of fig. 8 shows the relationship between the heating temperature of the tantalum wire and the value of the first internal pressure at which the carbonization treatment non-uniformity does not occur when the value of the first internal pressure is 1.0 Pa. The other three dashed curves show the relationship between the heating temperature of the tantalum wire and the value of the first internal pressure at which the carbonization treatment unevenness does not occur, when the values of the first internal pressure are 0.1Pa, 10Pa, and 100Pa, respectively. In each curve, the formation of tantalum carbide was not uniform in the region on the left side of the curve, but was not uniform in the region on the right side of the curve.

The result of the data visualization process shown in fig. 8 is: the length of the time during which the vacuum chamber 3 is once brought to the first internal pressure and the length of the time during which the vacuum chamber is once brought to the second internal pressure are set to be the same, and the total of the time during which the vacuum chamber is subjected to the carbonization treatment is set to be 10 minutes. In the data shown in fig. 8, the carbonization treatment was performed with the supply amount of acetylene gas set to 500sccm for the time of the first internal pressure and 0sccm for the time of the second internal pressure.

And (3) confirming that: by setting the time for once reaching the second internal pressure to be equal to or less than the time for once reaching the first internal pressure, the length of time for once reaching the first internal pressure is shortened while changing the internal pressure of the vacuum chamber 3, thereby suppressing occurrence of unevenness in the carbonization treatment. Although the time for once reaching the second internal pressure may vary depending on the exhaust rate, the time for once reaching the second internal pressure may be, for example, 5% or more of the time for once reaching the first internal pressure, or the time for once reaching the second internal pressure may be 2 seconds or more, and it is preferable that the time is a length that the vacuum chamber 3 can completely decrease from the first internal pressure to a desired second internal pressure. The length of time for which the first internal pressure is once reached can be appropriately set according to the value of the first internal pressure.

As shown in fig. 8, in the curve of the solid line in the case where the first internal pressure value is 1.0Pa, for example, when the heating temperature of the tantalum wire is 2150 ℃ and the length of time of the first internal pressure is 1 minute, the formation unevenness does not occur. In fig. 8, the open circle represents the case where the heating temperature of the tantalum wire is 2150 ℃ and the length of time at the first internal pressure is 1 minute, and is located on the right side of the curve of the solid line.

In the solid line graph, when the heating temperature of the tantalum wire was 2150 ℃ and the length of time for which the first internal pressure was reached was 5 minutes, formation unevenness occurred. In fig. 8, the black circles indicate the case where the heating temperature of the tantalum wire is 2150 ℃ and the length of time at the first internal pressure is 5 minutes, and are located on the left side of the solid line curve.

In this way, the length of time during which the first internal pressure does not become uneven can be appropriately set according to the heating temperature of the tantalum wire.

As shown in fig. 8, the length of time during which the first internal pressure does not become uneven can be set appropriately according to the heating temperature of the tantalum wire, as in the case of the solid line curve, in the other broken line curves.

As shown in fig. 8, the length of time of the preferred first internal pressure for which the unevenness of the carbonization treatment does not occur differs depending on the value of the first internal pressure. However, in both cases, it was confirmed that the carbonization treatment was performed by changing the internal pressure of the vacuum chamber 3 so that the first internal pressure and the second internal pressure lower than the first internal pressure alternately alternate with each other while shortening the length of the time period for which the internal pressure was changed to the first internal pressure, thereby suppressing the occurrence of unevenness in the formation of tantalum carbide.

As described above, by carbonizing the tantalum wire 60 while changing the internal pressure of the vacuum chamber 3 in the acetylene gas atmosphere, the catalytic wire 6 having tantalum carbide uniformly formed on the surface over the entire length can be obtained.

A desired film can be formed on a substrate by a catalytic chemical vapor deposition method using a film forming apparatus (not shown) provided with the catalytic wire 6. Specifically, the substrate is disposed vertically opposite to the plurality of catalytic wires 6 provided in the film forming apparatus so as to hang down in the vertical direction. Then, the raw material gas is introduced into the film forming apparatus while being heated by supplying an alternating current to the catalytic wires 6, thereby forming a film. The raw material gas is brought into contact with the catalytic wire 6 heated to a high temperature, and decomposed species of the reaction gas generated by the catalytic reaction or the thermal decomposition reaction are deposited on the substrate to form a film.

In the present embodiment, since the film can be formed using the catalytic wire 6 in which tantalum carbide is uniformly formed on the surface over the entire length, a film having stable film characteristics can be formed in a plane. Further, since tantalum carbide is uniformly formed on the surface of the catalytic wire 6 over the entire length, thermal durability and mechanical durability are high. This prevents thermal elongation and fusion of the catalytic wires 6 during film formation, and eliminates the need to frequently replace the catalytic wires after film formation, thereby improving productivity of film formation.

The present invention is not limited to the embodiment, and can be modified within a range not departing from the gist of the present invention.

In the above-described embodiment, the internal pressure of the vacuum chamber is changed by changing the supply amount of the acetylene gas introduced into the vacuum chamber, but the present invention is not limited thereto.

For example, the amount of the discharged gas may be controlled in addition to the amount of the acetylene gas supplied, so that the change in the internal pressure of the vacuum chamber may be controlled.

In the above-described embodiment, the example of the energization heating wire in which tantalum carbide is formed on the surface of the tantalum wire has been described, but the energization heating wire is not limited thereto. For example, the energizing heater wire may be configured as follows: the electric heating wire having tantalum carbide formed on the surface of the tantalum wire is further coated with a coating layer made of at least one of a boride of tantalum and boron. In this structure, since the clad layer contains boride of tantalum or boron, for example, alloying reaction (silicidation) with silicon used in a film formation step in a catalytic chemical vapor deposition method using an energization heating wire can be prevented, and reduction in mechanical strength can be suppressed.

In the above-described embodiment, the tantalum wire is heated by supplying direct current thereto, but alternating current may be supplied thereto.

Description of the reference numerals

1: manufacturing apparatus

3: vacuum cavity (Chamber)

6: catalytic wire (electrified heating wire)

8: power supply

9: acetylene gas supply unit

10: exhaust control part (first control part)

15: gas supply control part (second control part)

60: tantalum wire