JP2011169489A - Variable-temperature-gradient multi-zone type electric furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable-temperature-gradient multi-zone type electric furnace capable of changing a position of a heating element of a third zone which has been fixed heretofore, from the external. <P>SOLUTION: In this electric furnace including two or more heating elements in the so-called inner heat-type electric furnace having a heating section with the heating element and synthesizing a mono-crystal, a temperature distribution of the electric furnace can be changed by changing the position of the heating element as a heat source from the external. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric furnace for synthesizing crystals including single crystals and polycrystals for silicon solar cells.

  In the conventional internal heating type crystal growth type vertical electric furnace, the position of the heating element is fixed, and a certain temperature distribution can be obtained by changing the set temperature of each zone.

  However, the conventional method has a limit. For example, in a conventional internal heating type electric furnace, the heating element is fixed inside the electric furnace, and the position between the heating elements cannot be easily changed.

Japanese Patent Laid-Open No. 06-294585

  Therefore, the present invention provides a variable temperature gradient type multi-zone electric furnace in which the position of the heating element of the third zone that has been fixed so far can be varied from the outside.

  In order to solve the above-mentioned problems, the present invention provides a heating element in an electric furnace for synthesizing a so-called internal heating type single crystal having a heating part (inside the heating part and the heating element) having a large number of heating elements. Is an electric furnace composed of two or more, and the electric furnace has a configuration in which the temperature distribution can be changed by changing the position of a heating element as a heating source from the outside.

  Since the position between the third heating element and the second heating element is variable, a certain temperature distribution range can be covered.

  Further, by changing the speed of changing the distance between the heating elements from high to low, various materials can be melted or crystals can be grown.

  Furthermore, as an application example, it is considered that a longer crystal can be grown by moving the heating element during crystal growth.

It is an internal block diagram of a conventional electric furnace. It is an internal block diagram of the variable temperature gradient type multi zone type | mold electric furnace which is this invention. It is an internal block diagram which showed the state which moved the 3rd heating element of the variable temperature gradient type multi zone type | mold electric furnace which is this invention to the lowest part. It is the simplified figure which expanded a part of variable temperature gradient type multi zone type electric furnace which is the present invention. It is the simple figure which showed the state which changed the variable temperature gradient type multi zone type | mold electric furnace which is this invention for temperature distribution measurement. It is the figure which showed the temperature distribution measured with the variable temperature gradient type multi zone type electric furnace which is this invention.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is an internal configuration diagram of a conventional electric furnace. First, the internal structure of a three-zone vertical electric furnace will be explained using Fig. 1 among conventional multi-zone electric furnaces.

  The water cooling chamber 101 constituting the electric furnace 100 includes a cylindrical body chamber 11 whose outer peripheral surface is covered with a body chamber water cooling jacket 12, and an upper lid 10 that is attached to the upper surface of the body section chamber 11 via an upper flange 10. A lower lid 31 is fixed to the lower surface of the body portion chamber 11 with screws through a lower flange 23 and an O-ring.

  The upper flange 10 is insulated and sealed by a sealing member such as an O-ring, and an upper lid water cooling jacket 9 is attached to suppress an increase in temperature. On the other hand, the lower flange 23 is fixed to the fixing plate 22 by a fixing member such as a screw. Although not shown, the fixing plate 22 is fixed to a base or a gantry.

  An outer peripheral surface of the body portion chamber 11 is attached to a cooling port 32 so that it can be cooled with water. In the drawing, although there is one cooling port 32, two cooling ports 32 are attached for entrance / exit.

  In addition, first upper and lower heat insulating materials 53 and 16 and second upper and lower heat insulating materials 13 and 17 are installed on the inner wall surface of the body portion chamber 11. A heat insulating material separating plate 15 is installed between the second lower heat insulating materials 16 and 17. Due to the heat insulating materials 13, 53, 16, and 17, the temperature rise of the body portion chamber 11 is suppressed.

  A first heating element 4 is attached to the center of the lower surface of the upper lid 1 via a first heating element electrode 3 fixed by a stopper 7, and the first heating element 4 is a first heating element electrode 3. As a result, electricity can flow from the outside.

  A first thermocouple 40 is installed inside the first heating element electrode 3 as a heat sensor to control the temperature of the first heating element 4 via a heat insulating material 54. The upper surface heat insulating material 2 is installed on the outer peripheral portion of the electrode 3 by a heat insulating material fixing plate 41.

  A second heating element electrode 6 is installed between the upper surface heat insulating material 2 and the second upper heat insulating material 13, and a second heating element 14 is attached to the lower end of the second heating element electrode 6. ing. Therefore, electricity flows from the outside through the second heating element electrode 6 to the second heating element 14.

  The second heating element electrode 6 is sealed inside and outside of the upper lid 1 by an insulating seal member 8 such as an O-ring, and the second heating element electrode 6 and the upper lid 1 are insulated. The second heating element electrode 6 and the upper lid 1 are fixed by a stopper 7.

  The upper surface heat insulating material 2 located between the first heating element electrode 3 and the second heating element electrode 6 includes a second thermocouple 5 as a heat sensor for controlling the temperature of the second heating element 14. A third thermocouple 42 is installed as a heat sensor for controlling the temperature of the third heating element 18 described later.

  The third heating element 18 is a heating element installed below the second heating element 14, and a space is provided between the second heating element 14 and the third heating element 18. This space is further divided by the tip portion of the heat insulating material separating plate 15 so that the heat generated from the respective heating elements of the second heating element 14 and the third heating element 18 does not easily interfere with each other.

  The lower end of the third heating element 18 is connected to the third heating element electrode 19, and the lower end of the third heating element electrode 19 is fixed to the lower electrode fixing plate 26 via the electrode fixture 25. . Further, the lower electrode fixing plate 26 is fixed to the lower lid 31 via the electrode fixing rod 24.

  The second heating element electrode 19 is insulated and sealed by an O-ring or an insulating seal member 8, and upper and lower heat insulating materials 20 and 21 are installed inside the second heating element electrode 19.

  A cylindrical body projects downward from the center of the lower lid 31, and a seal flange 28 having a hole formed in the center is attached to the cylindrical body via a clamp 27. Further, a cylindrical furnace core tube 33 with a lid is installed on the center upper surface of the lower lid 31.

  A lower crucible support tube 29 is inserted into the hole of the seal flange 28, and the lower crucible support tube 29 and the seal flange 28 are sealed with a seal member.

  An upper crucible support tube 36 is connected to the upper end of the lower crucible support tube 29, and a crucible cradle 35 is attached to the upper end of the upper crucible support tube 26. A crucible 34 is placed on the crucible cradle 35. A plurality of heat reflecting plates 37 are attached to the lower outer peripheral surface of the upper crucible support tube 36.

The support tube 29 is fixed by a crucible support base cradle 38, and the crucible support tube 29 is fixed to a mounting plate 39 via the crucible support base cradle 38.
The lower end of the lower crucible support tube 29 is fixed to a crucible support tube support 38, and the crucible support tube support 38 is fixed to a mounting plate 39. A moving plate measuring plate 30 is connected to the lower surface of the mounting plate 39.

  A crystal can be synthesized by moving the crucible 34, and there is the moving plate measuring plate 30 for moving the crucible 34.

  The seal metal part 43 is a member for sealing the first thermocouple 40, and the seal metal part 44 is a member for sealing the second thermocouple 5 and the third thermocouple 42.

  The first and second lower heat insulating materials 16 and 17 are located outside the third heating element 18, and the first and second lower heat insulating materials 16 and 17 are the first and second upper heat insulating materials. Similar to the materials 53 and 13, the temperature rise of the body portion chamber 11 is suppressed.

  In FIG. 1, since all three heating elements 4, 14, and 18 are fixed, when changing the temperature distribution, the set temperature of the dedicated temperature control for the second heating element 14 and the third heating element 18 is changed. Although a moderate temperature distribution was obtained, there was a limit to this. Therefore, in the present invention, the third heating element 18 can be moved to obtain a more gentle temperature distribution.

  Next, the electric furnace of the present invention will be described with reference to FIG. FIG. 2 is an internal configuration diagram of the variable temperature gradient type multi-zone electric furnace according to the present invention, and FIG. 3 is an internal view showing a state where the third heating element of the variable temperature gradient type multi-zone electric furnace is moved to the lowermost part. FIG. 4 is a schematic diagram showing an enlarged part of a variable temperature gradient multi-zone electric furnace.

  As shown in FIGS. 2 and 3, the variable temperature gradient multi-zone electric furnace 102 according to the present invention is similar to the electric furnace 100 except for the following points.

  First, the heat insulating material located below the third heat generating element 18 and inside the third heat generating element electrode 19 is only the upper heat insulating material 20, and the place where the lower heat insulating material 21 was present is a cavity. Since the upper heat insulating material 20 is fixed by a fixing plate 51 attached to the third heating element electrode 19, the upper heat insulating material 20 does not slip downward and there is a space below the upper heat insulating material 20. Some state is maintained.

  Next, the electrode fixing rod 24 was removed, the lower electrode fixing plate 26 was made slightly smaller, and a third heating element moving base 45 was attached to the lower surface of the lower electrode fixing plate 26. As a result, the third heating element 18, the third heating element electrode 19, and the lower electrode fixing plate 26 are free from the lower lid 31 and can be moved up and down.

  As shown in FIGS. 3 and 4, by moving the lower electrode fixing plate 26 downward, the third heating element 18 and the third heating element electrode 19 are also moved downward. The first and second upper heat insulating materials 53 and 13 and the first and second lower heat insulating materials 16 and 17 also moved downward. At this time, a gap is formed above the first and second upper heat insulating materials 53 and 13, but the temperature distribution is not affected. On the other hand, the space below the upper heat insulating material 20 is lost because the upper heat insulating material 20 moves downward.

  FIG. 5 is a simplified diagram showing a state where the variable temperature gradient type multi-zone electric furnace according to the present invention is changed for temperature distribution measurement.

  First, the crucible 34 and the upper and lower crucible support tubes 36 and 29 are removed from the furnace core tube 33 with a lid, and the seal flange 28 is replaced with a measurement-specific seal flange 52. An alumina tube fixing bracket 49 is attached to the upper center surface of the seal flange 52, and an alumina tube 46 is attached to the alumina tube fixing bracket 49.

  An alumina protective tube 47 is provided inside the alumina tube 46, and a thermocouple 48 with an insulating tube is inserted into the alumina protective tube 47. The alumina protective tube 47 is fixed to the seal flange 52 with a seal fitting 43.

  The lower end of the alumina protective tube 47 is connected to a protective tube fixing metal fitting 50, and the protective tube fixing metal fitting 50 is fixed to a mounting plate 39 provided with a moving plate measuring plate 30 in the lower part. By moving the moving plate measuring plate 30, the alumina protective tube 47 and the thermocouple 48 inside the alumina tube 46 are moved, and the temperature can be measured at an arbitrary position.

  Since the alumina tube 46 is fixed inside the furnace core tube 33 with a lid, the thermocouple 48 is not affected by convection.

  FIG. 6 is a view showing a temperature distribution measured by the variable temperature gradient multi-zone electric furnace according to the present invention, and the third heating element 18 has moved to the uppermost part (FIG. 2) and the lowermost part (FIG. 3). Is the temperature distribution.

  As shown in FIG. 6, when comparing the conventional electric furnace 100 and the variable temperature gradient multi-zone electric furnace 102 of the present invention, the temperature of the conventional electric furnace 1 and the case where the third heating element 18 is located at the uppermost part are compared. The distribution was similar.

  When the third heating element 18 is at the uppermost part, the temperature distribution in the conventional electric furnace 1 is not shown because it has the same distribution as the conventional electric furnace 1.

  According to the present invention, a variable temperature gradient type multi-zone electric furnace 102 that can cover a certain temperature distribution range is constructed.

  By changing the speed of the moving mechanism of the third heating element 18 from high speed to low speed, various materials can be melted and crystals can be grown, and other new applications can be considered.

  Although the present invention has been described when there are three heating elements (4, 14, 18), the present invention can be applied to a furnace having two heating elements.

  When the number of heating elements is four or more, it is possible to obtain the same effect by enabling the electrodes of the heating elements of the portion to be moved to be moved simultaneously or individually.

  A unique application would be to allow longer crystals to grow by moving the heating element during crystal growth.

  The variable temperature gradient multi-zone electric furnace according to the present invention can be applied to the field of synthesizing electric furnaces and semiconductor crystals for synthesizing single crystals and polycrystals for silicon solar cells.

DESCRIPTION OF SYMBOLS 1 Upper cover 2 Upper surface heat insulating material 3 1st heating element electrode 4 1st heating element 5 2nd thermocouple 6 2nd heating element electrode 7 Stopper 8 Insulation seal member 9 Upper cover water cooling jacket 10 Upper flange 11 Body part chamber 12 Body part Chamber water cooling jacket 13 Second heat insulating material 14 Second heat generating member 15 Heat insulating material separating plate 16 First lower heat insulating material 17 Second lower heat insulating material 18 Third heat generating member 19 Second heat generating member electrode 20 Upper heat insulating material 21 Lower heat insulating material 22 Fixing plate 23 Lower flange 24 Electrode fixing rod 25 Electrode fixing tool 26 Lower electrode fixing plate 27 Clamp 28 Seal flange 29 Lower crucible support tube 30 Moving plate measuring plate 31 Lower lid 32 Cooling port 33 Furnace core tube 34 with crucible 35 crucible cradle 36 upper crucible support tube 37 heat reflecting plate 38 crucible support tube pedestal 39 mounting plate 40 first thermocouple 41 heat insulating material fixing plate 42 third thermocouple 43 Seal metal part 44 Seal metal part 45 Third heating element moving base 46 Alumina pipe 47 Alumina protective pipe 48 Thermocouple with insulating pipe 49 Alumina pipe fixing metal 50 Protection pipe fixing metal 51 Fixing base 52 Seal flange 53 First upper heat insulation Material 54 Heat insulation material 100 Electric furnace 101 Water-cooled chamber 102 Variable temperature gradient type multi-zone electric furnace

Claims (1)

  In an electric furnace comprising two or more heating elements in an electric furnace for synthesizing a so-called internal heating type single crystal having a heating part having a heating element, by changing the position of the heating element as a heating source from the outside, Electric furnace that can change the temperature distribution.

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