JP4510046B2 - Carbon wire enclosed heater - Google Patents

Description

  The present invention relates to a carbon wire encapsulated heater, and more particularly to a carbon wire encapsulated heater that can be suitably used in a semiconductor process and has good heat generation characteristics.

  In a semiconductor manufacturing process, strict temperature control in each heat treatment atmosphere is required in various heat treatment steps such as oxidation, diffusion, or CVD treatment. In addition, it is an essential requirement that the heating means in the heat treatment step does not become a source of a substance that degrades semiconductor performance such as impurity metals. From this, conventionally, for example, a heating element made of tungsten or the like is used. Many heaters whose outer sides are covered with a quartz glass tube are used.

  By the way, for example, when the heater is used in the field of semiconductor manufacturing processes, etc., if the quartz glass tube covering the heating element made of tungsten or the like is damaged, the atmosphere or cleaning liquid, polishing liquid, etc. will be contaminated with metal. As a result, there is a problem that the wafer is contaminated. Further, even if the quartz glass tube is not damaged, there is a problem that metal is contaminated from the heating element through the quartz glass tube.

The inventors of the present invention have proposed a carbon wire encapsulated heater that can be suitably used as a semiconductor manufacturing heater as compared with a metallic heating element from the viewpoint of preventing impurity metal contamination (Patent Document 1).
This carbon wire (heating element) is made by knitting a plurality of carbon fiber bundles made by bundling ultra-thin carbon fibers. Compared to conventional metal heating elements, this carbon wire has a smaller heat capacity and superior temperature rise / fall characteristics. Excellent resistance to high temperature in oxidizing atmosphere. In addition, because it is made by knitting a plurality of thin carbon fiber bundles, it is more flexible than a heating element made of a solid carbon material and can be easily processed into various structures and shapes as a heater for semiconductor manufacturing. Has the advantage.
JP 2000-21890 A

  By the way, recently, particularly in the field of semiconductor manufacturing industry, due to the large capacity integration of semiconductor circuits, the diameter of wafers has been increasing, and in addition, the demand for yield improvement has been strengthened to reduce costs, in order to meet these demands. Conventionally, more strict temperature control management is required. Therefore, the appearance of a heater that can heat a processing furnace or the like to a desired state and has little heat generation unevenness is desired.

As described above, this carbon wire encapsulated heater is very excellent from the viewpoint of preventing impurity metal contamination, but when using the heater, black spots are generated on the inner surface of the element pipe (quartz glass tube) encapsulating the carbon wire. Was recognized.
In particular, the occurrence of black spots was noticeably observed in a carbon wire encapsulated heater having a straight heat generating portion and having terminal portions at both ends via bent portions and having a U-shaped side surface.
The generation of black spots on the inner surface of the element pipe (quartz glass tube) enclosing the carbon wire is not preferable because it causes heat generation unevenness because it blocks and shields the radiant heat from the heater.

  Accordingly, the inventors of the present invention have conducted extensive research on the cause of black spots, and as a result, the amount of adsorbed moisture of the carbon wire enclosed in the element pipe (quartz glass tube) has an influence, and the element pipe (quartz glass tube). The inventors have found that the inner diameter has an influence, and have completed the present invention.

  The present invention has been made to solve the above technical problem, and an object of the present invention is to provide a carbon wire encapsulated heater in which the generation of black spots is suppressed, heat generation unevenness is small, and heat generation characteristics are good.

The carbon wire encapsulated heater according to the present invention made to solve the above object is a carbon wire encapsulated heater in which a carbon wire woven using a plurality of carbon fibers is encapsulated in a quartz glass member. The amount of moisture adsorbed is 2 × 10 ⁻³ g / cm ³ or less, the quartz glass member is tubular, and the ratio of the diameter of the carbon wire to the inner diameter of the quartz glass tube is 1: 2-5. It is characterized by.

The carbon wire sealed in the quartz glass member adsorbs a relatively large amount of moisture. Therefore, as shown in the following reaction formula, this adsorbed moisture reacts with the carbon wire when the temperature is raised, and when cooled, the reaction molecules adhere to the inner surface of the element pipe (quartz glass tube) as a black spot.
Scheme _{C + H 2 O ⇔ CO +} H 2
Therefore, in order to suppress the reaction, the amount of adsorbed moisture of the carbon wire enclosed in the quartz glass member is set to 2 × 10 ⁻³ g / cm ³ or less.

As described above, in the carbon wire encapsulated heater according to the present invention, since the carbon wire having an adsorbed moisture amount of 2 × 10 ⁻³ g / cm ³ or less is used, generation of black spots is suppressed and heat generation unevenness is small. Good heat generation characteristics can be obtained.

  Further, the quartz glass member is tubular, and the ratio of the diameter of the carbon wire to the inner diameter of the quartz glass tube is 1: 2 to 5.

When the ratio of the inner diameter of the quartz glass tube is less than 2 when the diameter of the carbon wire is 1, the possibility that the carbon wire and the inner surface of the quartz glass tube are in contact with each other is high. The distance from the wire to the inner surface of the quartz glass tube is very close.
Therefore, when the black spot molecules are generated, the black spots are concentrated on the inner surface of the quartz glass tube at the shortest distance without being dispersed inside the quartz glass tube.
As a result, a black spot can be confirmed from the appearance of the carbon wire encapsulated heater, and uneven heat generation occurs in such a portion, which is not preferable.

  On the other hand, when the ratio of the inner diameter of the quartz glass tube is more than 5 when the diameter of the carbon wire is 1, it is preferable because the heat capacity of the quartz glass tube increases and the thermal responsiveness at the time of raising and lowering the temperature decreases. Absent.

Further, the carbon wire encapsulated heater is a U-shaped carbon wire encapsulated heater having a linear heat generating portion and terminal portions via bent portions at both ends thereof, wherein the carbon wire is the quartz glass. It is desirable to be arranged eccentrically from the center of the tube.
As described above, when a carbon wire having an adsorbed moisture amount of 2 × 10 ⁻³ g / cm ³ or less is used, the occurrence of black spots is suppressed even if the carbon wire is eccentrically arranged from the center of the quartz glass tube. Thus, it is possible to obtain a carbon wire encapsulated heater with excellent heat generation characteristics with little heat generation unevenness.
Further, when the ratio of the inner diameter of the quartz glass tube is 2 to 5 when the diameter of the carbon wire is 1, the generation of black spots is suppressed even if the carbon wire is eccentrically arranged from the center of the quartz glass tube. Thus, it is possible to obtain a carbon wire encapsulated heater with excellent heat generation characteristics with little heat generation unevenness.

  As described above, according to the carbon wire encapsulated heater according to the present invention, it is possible to obtain a carbon wire encapsulated heater in which the generation of black spots is suppressed and the heat generation characteristics are good.

  An embodiment according to the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic cross-sectional view of a carbon wire encapsulated heater having a U-shaped side surface having a linear heat generating portion and terminal portions via bent portions at both ends, and FIG. FIG. 3 is a schematic cross-sectional view of a linear heat generating portion of a carbon wire encapsulated heater.

As shown in FIG. 1, the carbon wire encapsulated heater 1 includes a linear heat generating portion 2 and terminal portions 3 provided at both ends of the heat generating portion 2, and has a U-shaped side surface. .
The heat generating part 2 is composed of a quartz glass tube 20 containing a carbon wire 4 as a heat generating element made of a carbon fiber bundle, and includes a linear part 21. The quartz glass tube 20 includes the linear portion 21, a bent portion 22 that is bent at both ends thereof and connected to the terminal portion 3, and a large-diameter portion 23 that constitutes a part of the terminal portion 3.
As shown in FIG. 3A, the inner diameter C of the quartz glass tube 20 is formed so that the ratio is 2 to 5 when the diameter D of a carbon wire to be described later is 1. Note that the carbon wire 4 may be slightly changed and may have an elliptical shape. In this case, the short diameter of the ellipse is set to 1, and the inner diameter C of the quartz glass tube 20 is determined so as to have the above ratio.

Moreover, the said terminal part 3 has one connection line 31, and as shown in FIG. Since these terminal portions 3 have the same structure, only one terminal portion 3 will be described.
The terminal portion 3 includes a large-diameter portion 23 of the quartz glass tube 20 constituting the terminal portion 3, a straight tube 32 accommodated in the large-diameter portion 23, and a plurality of compressed and accommodated in the straight tube 32. Wire carbon material 33, a sealing glass tube 34 that seals the end of the quartz glass tube 20, and a connection line 31 made of tungsten (W) provided on the sealing glass tube 34.

  The carbon wires 4 are connected by a structure sandwiched between a plurality of wire carbon materials 33 compressed and housed in a straight pipe 32 in a compressed state, and connecting wires 31 are connected to the wire carbon materials 33.

Next, the carbon wire 4 will be described with reference to FIG.
This carbon wire 4 is produced by knitting a plurality of carbon fiber bundles made by bundling ultra-thin carbon single fibers into a braided or braided shape, compared to a conventional metal or SiC heating element. The heat capacity is small and the temperature rise / fall characteristics are excellent, and the high temperature durability is also excellent in a non-oxidizing atmosphere.

In addition, since it is made by knitting a plurality of thin carbon single fiber bundles, it is more flexible than a heating element made of Muku's carbon material, and has excellent shape deformation adaptability and workability.
Specifically, as the carbon wire 4, a knitted string having a diameter of about 2 mm using about 10 bundles of carbon fibers having a diameter of 5 to 15 μm, for example, about 3000 to 3500 carbon fibers having a diameter of 7 μm, Alternatively, carbon wires such as braided braids are used.

As the carbon wire 4, a carbon wire having an adsorbed moisture amount of 2 × 10 ⁻³ g / cm ³ or less is used.
Thus, since the carbon wire 4 has a small amount of adsorbed moisture, the reaction between the adsorbed moisture and the carbon wire is suppressed at the time of temperature rise. As a result, the adhesion of reactive molecules (black spots) to the inner surface of the quartz glass tube 20 is suppressed.
Even if a reaction between adsorbed moisture of 2 × 10 ⁻³ g / cm ³ or less and the carbon wire occurs at the time of temperature rise, in this case, it does not become a black spot and does not affect the heat generation characteristics of the heater. A thin film of a certain degree only adheres to the inner surface of the quartz glass tube 20.

The carbon wire braid span is about 2 to 5 mm. The braided or braided carbon wire 4 preferably has carbon fiber fluff 4a on the surface, and this fluff is a part of the carbon wire (single fiber) cut out of the carbon wire. It protrudes from the outer peripheral surface.
The surface fluff due to the carbon fiber is preferably about 0.5 to 2.5 mm.

In addition, from the viewpoint of exothermic homogeneity, durability stability and the like, and from the viewpoint of avoiding dust generation, the carbon fiber is preferably highly pure, and the amount of impurities contained in the carbon fiber is 10 ppm or less as ash weight. It is preferable that
More preferably, the amount of impurities contained in the carbon fiber is 3 ppm or less as ash weight.

And it is preferable to insert the carbon wire 4 in the quartz glass tube 20 so that only the fluff 4a is in contact with the inner wall of the quartz glass tube and the main body of the carbon wire 4 is not substantially in contact. By doing so, reaction under high temperature between quartz glass (SiO ₂ ) and carbon (C) of the carbon wire is suppressed as much as possible, and deterioration of the quartz glass and a decrease in durability of the carbon wire are suppressed.

However, as shown in FIG. 1, the carbon wire encapsulated heater 1 has a linear heat generating portion 2, and has terminal portions 3 through bent portions at both ends thereof. Therefore, the carbon wire 4 is arranged eccentrically from the center of the quartz glass 20.
That is, as shown in FIG. 3A, the carbon wire 4 is eccentrically arranged in the quartz glass tube 20, and the carbon wire 4 and the inner surface of the quartz glass tube 20 are in contact with each other.

At this time, the inner diameter C of the quartz glass tube 20 is formed so that the ratio is 2 to 5 when the diameter D of the carbon wire 4 is 1, as shown in FIG.
Thus, when the diameter D of the carbon wire 4 is set to 1, the ratio of the inner diameter C of the quartz glass tube 20 is 2 to 5, so the carbon wire 4 and the inner surface of the quartz glass tube 4 The area of the contact portion A can be reduced.
On the other hand, as shown in FIG. 3B, when the diameter D of the carbon wire 4 is 1, when the ratio is less than 2, the area of the contact portion B between the carbon wire 4 and the inner surface of the quartz glass tube 20 is as follows. It becomes large and is not preferable.

Further, since the ratio of the inner diameter C of the quartz glass tube 20 is 2 to 5, the distance d from the carbon wire 4 to the inner surface of the facing quartz glass tube 20 is long even in a non-contact portion. .
Therefore, even if the black spots (reactive molecules) are generated, they are dispersed inside the quartz glass tube 20 and formed as a thin black film inside the quartz glass tube 20.
In this way, since it is not formed intensively as a black spot in a specific portion of the quartz glass tube 20, heat generation unevenness does not occur.

On the other hand, when the ratio of the inner diameter C of the quartz glass tube exceeds 5 when the diameter D of the carbon wire 4 is 1, the heat capacity of the quartz glass tube 20 is increased, and the thermal responsiveness at the time of raising and lowering the temperature is lowered. Therefore, it is not preferable.
Further, black spots in the quartz glass tube 20 are likely to occur in a portion that is easily cooled.
Therefore, the inner diameter C of the quartz glass tube 20 becomes too large with respect to the diameter D of the carbon wire 4 (the ratio of the inner diameter C of the quartz glass tube when the diameter D of the carbon wire 4 is 1 exceeds 5). The distance d in FIG. 3 (a) is increased, and in particular, black spots are likely to occur in the portion a that is easily cooled.

  Considering the above, when the diameter D of the carbon wire 4 is 1, it is preferable that the ratio of the inner diameter C of the quartz glass tube 20 is 2 to 5.

In the carbon wire encapsulated heater 1 configured as described above, since the carbon wire 4 having an adsorbed moisture amount of 2 × 10 ⁻³ g / cm ³ or less is used, power is supplied to the carbon wire 4, Even when the temperature rise and fall is repeated, the generation of black spots is suppressed, and good heat generation characteristics with little heat generation unevenness can be maintained.
Similarly, when the inner diameter C of the quartz glass tube 20 is 2 to 5 times the diameter D of the carbon wire 4, the generation of black spots is suppressed, and good heat generation characteristics with less heat unevenness can be maintained. it can.

Using carbon wires with different amounts of adsorbed moisture, a U-shaped carbon wire encapsulated heater (straight portion length: 700 mm) shown in Fig. 1 is manufactured, and a temperature rise test is performed under the following conditions. We confirmed the occurrence of sunspots. The pressure inside the quartz glass tube 20 at the time of manufacturing the heater was 1 torr at a heater temperature of 1200 ° C.
Temperature rising conditions Temperature rising atmosphere: Air release system Element temperature: 1350 ° C
Operating time: 240h
The results are shown in Table 1.

  Thus, no black spot was observed in the carbon wire encapsulated heater using the carbon wire having a small amount of adsorbed moisture.

Also, using four types of quartz glass tubes with different inner diameters, the U-shaped carbon wire encapsulated heater (straight portion: 800 mm) shown in FIG. 1 was manufactured, and a temperature rise test was conducted under the following conditions. We confirmed the occurrence of sunspots. The pressure inside the quartz glass tube 20 at the time of manufacturing the heater was 1 torr at a heater temperature of 1200 ° C. A carbon wire having a moisture adsorption amount of 1 × 10 ⁻⁴ g / cm ³ or less was used.
Temperature rising conditions Temperature rising atmosphere: Air release system Element temperature: 1400 ° C
Operating time: 1h
The results are shown in Table 2.

  Thus, when the diameter of the carbon wire was 1 and the ratio of the inner diameter of the quartz glass tube was 2 to 5, it was recognized that the generation of black spots was suppressed. In Comparative Example 3, the heat capacity was large and the thermal response was inferior.

Further, using a quartz glass tube having an inner diameter of 3 mm and 10 mm, a U-shaped carbon wire encapsulated heater shown in FIG. 1 was manufactured, and a temperature rise test was performed under the following conditions to confirm the occurrence of black spots. The pressure inside the quartz glass tube 20 at the time of manufacturing the heater was 1 torr at a heater temperature of 1200 ° C. A carbon wire having a moisture adsorption amount of 1 × 10 ⁻⁴ g / cm ³ or less was used.
Temperature rise conditions Temperature rise atmosphere: Heat insulation pipe is set outside the heater pipe and the temperature rises Element temperature: 1600 ° C
Operating time: 1h
The results are shown in Table 3.

注）＊１は直線状部（発熱部）の石英ガラス管にのみ発生したことを意味する。
＊２は直線状部（発熱部）の石英ガラス管に薄黒膜が発生したことを意味する。
＊３は端子部の大径管部の石英ガラス管に黒点が発生したことを意味する。

Note) * 1 means that it occurred only in the quartz glass tube of the linear part (heating part).
* 2 means that a thin black film was generated in the quartz glass tube of the linear part (heating part).
* 3 means that a black spot was generated in the quartz glass tube in the large-diameter tube portion of the terminal portion.

  In Comparative Example 4, not only black spots but also white spots (Si) occurred. It was confirmed that there is an effect of suppressing black spots and white spots (Si) by increasing the inner diameter of the quartz glass tube.

FIG. 1 is a schematic cross-sectional view of a side U-shaped carbon wire encapsulated heater having a linear heat generating portion and terminal portions at both ends via bent portions. FIG. 2 is a schematic view of a carbon wire. FIG. 3 is a schematic cross-sectional view of a linear heat generating portion of the carbon wire encapsulated heater.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carbon wire enclosed heater 2 Heat generating part 3 Terminal part 4 Carbon wire 20 Quartz glass tube 21 Linear part 22 Bending part 23 Large diameter part 31 Connection line 32 Straight pipe 33 Wire carbon material 34 Sealing glass tube A Contact part B Contact part C Quartz glass inner diameter D Carbon wire diameter d Distance to the inner surface of the quartz glass tube

Claims (2)

In a carbon wire encapsulated heater in which a carbon wire woven using a plurality of carbon fibers is encapsulated in a quartz glass member,
The adsorbed moisture content of the carbon wire is 2 × 10 ⁻³ g / cm ³ or less,
The quartz glass member is tubular, and the ratio of the diameter of the carbon wire to the inner diameter of the quartz glass tube is 1: 2-5. The carbon wire encapsulated heater is a U-shaped carbon wire encapsulated heater having a linear heat generating portion and having terminal portions at both ends via bent portions,
The carbon wire encapsulated heater according to claim 1, wherein the carbon wire is arranged eccentrically from a central portion of the quartz glass tube.

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