JPH11273835A - Carbon heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the consumption period and thereby extend product life by forming one or more grooves in one surface of a current path of a carbon heater that generates heat by carrying current to the current path, having a cross-sectional shape which has corner parts on its four corners. SOLUTION: This carbon heater is formed from a cylindrical body 8 made by shaping graphite into a cylindrical form. In the cylindrical body 8, first slits 8a formed from the upper edge to the vicinity of the lower edge and second slits 8b formed from the lower edge to the vicinity of the upper edge are alternately formed at equal intervals around its entire circumference. By partitioning the cylindrical body 8, the first and second slits 8a, 8b run alternately between the upper edge side and the lower edge side, have constant cross-sectional areas and form a current path 9 having a cross-sectional shape having corner parts 9a at all their corners. In the peripheral surface of the cylindrical body 8, groove parts 10 are formed along the first and second slits 8a, 8b. The reduced portion of the current path 9 due to the grooved parts 10 is distributed equally to parts on both the sides of the grooved parts 10 in the width direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon heater that generates heat by passing a current through a current path.

[0002]

2. Description of the Related Art In a conventional carbon heater, after a cross-sectional area (total resistance) of a current path and the like are determined based on a power supply capacity and a specific resistance of the carbon heater itself, for example, as shown in FIG. By forming the cylindrical body 50 having an inner diameter of graphite with a uniform thickness by graphite, and forming slits 50a alternately at equal intervals from the upper end and the lower end of the cylindrical body 50, a portion partitioned by these slits 50a is defined. The current path 51 has a cross-sectional area of

[0003]

By the way, the current path 51 of the carbon heater formed as described above is shown in FIG.
As shown in FIG. 6, the cross section has corner portions 51a at four corners by being divided by slits 50a.
When electricity is supplied to the carbon heater, the corner portion 51a has a property of being locally consumed, so that the corner portion 51a is consumed from the corner portion 51a. Then, as the consumption of the corner portion 51a progresses and the consumable surfaces 51b and 51b of the adjacent corner portions 51a and 51a are joined together as shown by a two-dot chain line, a new corner portion 51 is added to the joined portion.
With the appearance of c, it has the property that consumption is further accelerated.

As a result, the slit 50a is formed in the cylindrical body 50 having a uniform thickness and the current path 51 is formed.
In the configuration described above, the cross-sectional shape of the current path 51 is substantially rectangular, and the gap between the corner portions 51a in the thickness direction is narrow, so that the consumable surfaces 51b are joined at an early stage,
The rapid decrease in the cross-sectional area of the current path 51 causes the calorific value of the carbon heater to exceed the product usage limit in a short period of time. Furthermore, when the carbon heater is used in a highly reactive atmosphere, the consumption due to the reaction occurs in addition to the consumption due to the local spark, so the consumption of the corner portion 51a becomes more conspicuous, and the calorific value becomes extremely short. You will exceed the possible limits. In addition, when the thickness of the carbon heater is reduced due to wear, the strength of the carbon heater is reduced, so that the carbon heater is easily damaged even under a slight load due to vibration during handling, operation, cleaning, etc. Then, the broken pieces become pollutants.

As described above, in the conventional carbon heater, since the interval between the corner portions 51a in the thickness direction is small,
Due to the consumption of the corner portion 51a, the heat generation exceeds the usable limit within a short period of time and the strength becomes insufficient, resulting in a problem that the product life is shortened. Therefore, an object of the present invention is to provide a carbon heater capable of extending the life of a product by increasing a consumption time until a heat generation amount exceeds a usable limit or the strength becomes insufficient.

[0006]

In order to solve the above-mentioned problems, the present invention provides a carbon heater which generates heat by energizing a current path having a cross-sectional shape having corners at four corners. Is characterized in that one or more grooves are formed.

In the above configuration, when the carbon heater is used, the corner portion is consumed by local sparking between the adjacent corner portion and the like, so that the thickness between the corner portions of the current path is reduced. To go. In particular, if the environment in which the carbon heater is used is an atmosphere having a high reactivity, the consumption due to the reaction occurs in addition to the consumption due to the local spark, so that the consumption of the corners becomes more remarkable, and the thickness between the corners becomes thin in a short period of time. It is becoming. Then, as the wear of the corners progresses, the wear surfaces of the corners join together to form a new corner,
As the cross-sectional area of the current path decreases more remarkably due to wear, the resistance value of the current path changes, and the heat generation exceeds the usable limit. In addition, when the thickness of the corner portion is reduced due to the progress of wear of the corner portion, insufficient strength occurs.

At this time, when the groove is present on at least one surface of the current path as in the present invention, the thickness between the corners of the current path is made larger than that without the groove if the cross-sectional area of the current path is constant. be able to. As a result, the consumption time until a new corner portion appears due to the joining of the consumable surfaces can be made longer than when the same thickness is formed, and as a result, the product life can be extended. Especially,
When used in a highly reactive atmosphere, the consumption time until a new corner portion appears can be extended, so that the product life extension effect can be more remarkably exhibited. In addition, if the gap between the corners of the current path becomes thicker, the consumption time until the thickness becomes insufficient can be lengthened, and the product life can be prolonged also in this regard.

Here, the cross-sectional shape having corners at the four corners means that the surface sandwiched between the corners may be any of a curved surface and a planar shape as long as the corners are provided at the four corners. Means that. That is, the cross-sectional shape of the current path is
The inner and outer surfaces of the current path may be curved, or each surface of the current path may be flat, as in the case where a current path is created by forming a slit in a flat plate. May be used.

Further, the carbon heater can be formed of a graphite extruded material or isotropic graphite,
It can be formed of a C composite. When the carbon heater is formed of a C / C composite,
Since the corners themselves are less likely to be consumed by the C / C composite, the product life can be further extended. Note that C
As the / C composite, those in which carbon fibers are arranged in 1D, 2D, 3D or more can be used. In addition, the material of the carbon heater is preferably in the range of 5 to 30 μΩ · m in that the function as the carbon heater can be sufficiently exhibited.

Further, the carbon heater may have a layer made of glassy carbon, pyrolytic carbon or silicon carbide formed on the surface of the current path. When such a layer is formed on the surface of the current path, the inside of the current path can be surrounded by a layer of glassy carbon or the like. Even if it does, it is possible to prevent materials such as graphite from scattering as particles and becoming contaminants. Further, when the layer made of silicon carbide is formed on the surface of the current path, in addition to the above-described effect of preventing the generation of contaminants, even when the use environment of the carbon heater is a highly reactive atmosphere, The silicon carbide layer can delay the reaction with the material such as graphite in the current path, thereby extending the product life.

The glassy carbon layer can be formed by applying a thermosetting resin such as a phenolic resin on the surface of the current path, heating and curing, and then heat-treating. The pyrolytic carbon layer can be formed by depositing carbon obtained by thermally decomposing a hydrocarbon such as methane gas or a hydrocarbon compound on the surface of the current path by a CVD method and / or a CVI method. Further, the silicon carbide layer is formed by depositing a material containing silicon and carbon by CVD and / or CVI.
It can be formed by depositing on the surface of the current path by the method.

The above-described carbon heater can be suitably used for a CZ device. That is, in the CZ device,
When the Si raw material is melted to produce a bulk Si single crystal, SiO gas is generated, and this SiO gas consumes the corner of the carbon heater, so that the corner is consumed more than when only the local spark is consumed. Notable occurrence. Accordingly, when a carbon heater having the same width as the conventional one is used in a CZ device, it is necessary to change the operating conditions of the CZ device in order to extend the product life of the carbon heater. If the carbon heater can increase the thickness between the corners as shown in FIG.
The product life can be reliably extended without changing the operating conditions of the Z device.

The carbon heater according to the present invention can be applied not only to a carbon heater for a CZ apparatus, but also to a carbon heater for heat treatment of various metals and ceramics. It can be applied to the carbon heater for the purpose.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 4, the carbon heater according to the present embodiment is provided in a CZ apparatus 1 for producing a Si single crystal. The CZ device 1 includes a storage chamber 2 whose inside can be depressurized to a vacuum state, a crucible 3 rotatably provided in the storage chamber 2 and storing a raw material 5 made of Si, and a crucible 3 arranged around the crucible 3. Carbon heater 4 for heating and melting raw material 5 in 3
Is placed above the crucible 3 and grown while pulling up a single crystal of Si from the raw material 5 in a molten state to form a bulk S
and a driving device 7 which is an i-single crystal 6.

As shown in FIG. 1, the carbon heater 4 comprises a cylindrical body 8 made of graphite in a cylindrical shape. As shown in FIG. 2, a first slit 8a formed from the upper end to the vicinity of the lower end and a second slit 8b formed from the lower end to the vicinity of the upper end are alternately formed in the cylindrical body 8 at equal intervals. Have been. The first and second slits 8a and 8b partition the cylindrical body 8 to alternately advance from the upper end to the lower end, have a constant cross-sectional area, and have corners 9a at four corners. A current path 9 having a cross-sectional shape is formed.

A groove 10 is formed on the outer peripheral surface of the cylindrical body 8 along the first and second slits 8a and 8b. As shown in FIG. 3, the groove 10 is formed substantially at the center of one surface of the current path 9 sandwiched between the widthwise corners 9 a. Further, the amount of reduction of the current path 9 by the groove 10 is equally distributed to both side portions of the groove 10 in the width direction. Accordingly, the current path 9 has a greater thickness between the corner portions 9a in the thickness direction than when the corner portions 9a are formed at a constant thickness in FIG. , Consumable surface 9b
It takes a long time before they join and a new corner 9c appears.

The operation of the carbon heater 4 in the above configuration will be described. First, the diameter of the carbon heater 4 and the cross-sectional area (total resistance) of the current path 9 are set so that the raw material 5 can be sufficiently melted based on the power supply capacity of the CZ apparatus 1 and the size of the crucible 3 in FIG. Determine the number of slits and the like.
Thereafter, the depth of the groove 10 is determined so that the thickness of the current path 9 is not less than the limit thickness Le, and the reduction in the cross-sectional area due to the groove 10 is uniformly distributed to both side portions of the groove 10 in the width direction. Thus, the sectional shape of the current path 9 is determined so as to have the above-described sectional area (total resistance). And FIG.
As shown in (1), a carbon heater 4 having the specifications determined in this way is created.

Next, as shown in FIG. 4, a carbon heater 4 is installed in the storage chamber 2 of the CZ device 1. Then, after charging the raw material 5 made of Si into the crucible 3, energization of the carbon heater 4 is started in a state where the pressure in the storage chamber 2 is reduced to a vacuum state, and the raw material 5 is melted by the heat generated by the carbon heater 4. Thereafter, the liquid level of the raw material 5 in the molten state is pulled up by the driving device 7 to grow the crystal, thereby producing the Si single crystal 6.

When the production of the Si single crystal 6 is started as described above, the raw material 5 is melted and the Si
O gas is generated. SiO gas, as shown in FIG.
Corner 9a of current path 9 constituting carbon heater 4
Will be mainly consumed. The corner 9a
Is also consumed by local sparking between the adjacent corners 9a. Thus, the thickness of the current path 9 is gradually reduced from both ends in the width direction where the corners 9a exist. At this time, the current path 9 is
The reduced cross-sectional area is evenly distributed to both sides of the groove 10, and the thickness at both ends where the corners 9 a are present is made thicker than when the corners 9 a are formed with a constant thickness in FIG. 16. ing. As a result, the consumable surfaces 9b and 9b are joined to each other as shown by a two-dot chain line in FIG.
The consumption time until the appearance of c becomes longer than before.

As described above, as shown in FIG. 1, the carbon heater 4 of the present embodiment generates heat by energizing the current path 9 having a cross section having four corners 9a at the four corners. The configuration is such that both ends of the path 9 are formed thicker than the central part. That is, the carbon heater 4 is configured such that the groove 10 is formed in the current path 9 so as to increase the thickness of both ends.

According to the above configuration, as shown in FIG.
By distributing the decrease in the cross-sectional area due to the groove 10 to both ends, it is possible to increase the thickness of both ends while maintaining a predetermined cross-sectional area. Therefore, when the corner portion 9a is consumed by using the carbon heater 4, a new corner portion 9c is formed by joining the consumable surfaces 9b.
Can be made longer than when it is formed with the same thickness, and as a result, the product life can be extended. Also, a corner 9a of the current path 9
If the thickness between the portions 9a is increased, the consumption time until the thickness becomes insufficient can be extended, and in this respect, the product life can be extended.

The carbon heater 4 according to the present embodiment
The first and second slits 8a are formed in a cylindrical body 8 having a cylindrical shape.
8b, and these first and second slits 8a.
Although it is constituted by forming the groove 10 along 8b, it is not limited to this. That is, the carbon heater 4 may be composed of the flat plate 21 of FIG. 5 or the strip 22 of FIG. In addition, the groove 10
7 and 8 may have a triangular shape or a concavely curved shape as shown in FIGS. 7 and 8, and a plurality of may be formed in parallel as shown in FIG. Further, the groove 10
As shown in FIGS. 10 to 14, one or more of the same or different shapes such as a triangular shape or a concavely curved shape may be formed on at least one surface of the current path 9. That is, a configuration in which a triangular groove 10 as shown in FIG. 10 is formed on both surfaces, a configuration in which a curved groove 10 as shown in FIG. 11 is formed on both surfaces, and a plurality of grooves 10 as shown in FIG. Are formed on both surfaces, a triangular groove 10 is formed on one surface and a plurality of grooves 10 are formed on the other surface as shown in FIG. 13, and a curved groove 10 is formed as shown in FIG. May be formed on one surface, and the triangular groove 10 may be formed on the other surface.

In this embodiment, the case where the carbon heater 4 is formed of graphite is described.
It may be created by a C / C composite. And
When the carbon heater 4 is formed of the C / C composite, the consumption of the corner portion 9a itself can be reduced due to the difficulty of consumption of the C / C composite, so that the product life can be further extended. Further, in the present embodiment, the case where the carbon heater 4 is applied to the CZ apparatus 1 is described, but the present invention is not limited to this, and all carbon heaters for heat treatment of various metals and ceramics are used. It can be applied to a carbon heater for use.

[0025]

According to the present invention, there is provided a carbon heater which generates heat by energizing a current path having a cross-sectional shape having corners at four corners, wherein one or two or more grooves are formed on at least one surface of the current path. Configuration.

According to the above configuration, assuming that the cross-sectional area of the current furnace is constant, the presence of the groove makes it possible to increase the thickness between the corners of the current path as compared with the case without the groove. Therefore, when the corner portion is worn out and the thickness is reduced by using the carbon heater, the consumption time until the calorific value becomes a cross-sectional area exceeding the usable limit due to the appearance of a new corner portion is reduced. Since it is longer than the case where it is not formed with the same thickness, there is an effect that the product life can be extended as a result. In particular, when used in a highly reactive atmosphere, the consumption time until a new corner portion appears can be extended, so that the product life extension effect can be more remarkably exhibited. Also, by increasing the thickness between the corners,
Since the consumption time until the thickness becomes insufficient in strength can be lengthened, the effect that the product life can be prolonged also in this regard.

Further, the carbon heater may be made of a C / C composite. In this case, since the corner portion itself is made of the C / C composite and is hardly consumed, the product life can be further extended. This has the effect.

In the carbon heater, a layer made of glassy carbon or pyrolytic carbon may be formed on the surface of the current path. In this case, the inside of the current path is surrounded by a layer of glassy carbon or the like. Therefore, even if the material such as graphite in the current path has a property such as brittleness, it is possible to prevent the material such as graphite from scattering as particles and becoming a pollutant. To play.

Further, the carbon heater may have a layer made of silicon carbide formed on the surface of the current path. In this case, in addition to the above-described effect of preventing the generation of pollutants,
Even when the environment in which the carbon heater is used is a highly reactive atmosphere, the effect of the silicon carbide layer delaying the reaction with the material such as graphite inside the current path and extending the product life can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a carbon heater.

FIG. 2 is a perspective view of a main part of a carbon heater.

FIG. 3 is an explanatory diagram showing a cross-sectional shape of a current path.

FIG. 4 is a schematic configuration diagram of a CZ device.

FIG. 5 is a perspective view of a main part of the carbon heater.

FIG. 6 is a partially cutaway perspective view showing a carbon heater.

FIG. 7 is an explanatory diagram showing a cross-sectional shape of a current path.

FIG. 8 is an explanatory diagram showing a cross-sectional shape of a current path.

FIG. 9 is an explanatory diagram showing a cross-sectional shape of a current path.

FIG. 10 is an explanatory diagram illustrating a cross-sectional shape of a current path.

FIG. 11 is an explanatory diagram showing a cross-sectional shape of a current path.

FIG. 12 is an explanatory diagram showing a cross-sectional shape of a current path.

FIG. 13 is an explanatory diagram showing a cross-sectional shape of a current path.

FIG. 14 is an explanatory diagram showing a cross-sectional shape of a current path.

FIG. 15 is a perspective view of a conventional carbon heater.

FIG. 16 is an explanatory diagram showing a cross-sectional shape of a conventional current path.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CZ apparatus 2 Storage chamber 3 Crucible 4 Carbon heater 5 Raw material 6 Si single crystal 7 Driver 8 Cylindrical body 8a 1st slit 8b 2nd slit 9 Current path 9a Corner part 10 Groove part

Claims (4)

[Claims] 1. A carbon heater that generates heat by supplying current to a current path having a cross-sectional shape having corner portions at four corners, wherein at least one surface of the current path has one or more grooves formed therein. A carbon heater characterized by the following. 2. The carbon heater according to claim 1, wherein the carbon heater is made of a C / C composite. 3. The carbon heater according to claim 1, wherein a layer made of glassy carbon or pyrolytic carbon is formed on the surface of the current path. 4. The semiconductor device according to claim 1, wherein a layer made of silicon carbide is formed on a surface of said current path.
The carbon heater as described.