JPH0475880B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF INDUSTRIAL APPLICATION The present invention relates to an improvement in a double crucible consisting of an inner crucible for containing a melt and an outer crucible for holding the inner crucible. BACKGROUND OF THE INVENTION Double crucibles are widely used as containers for containing melted raw materials such as semiconductors. For example, in the Czyochralski method (hereinafter abbreviated as the CZ method), which is a method for producing silicon single crystals, a double crucible is used in which a quartz crucible is used as an inner crucible and a graphite crucible is used as an outer crucible. Figure 2 is an explanatory diagram showing an example of the configuration of the double crucible used in the CZ method and the relative position of the double crucible and the heat insulating cylinder. Figure 2 shows the relative position at the start of crystal growth. The figure is a longitudinal sectional front view showing the relative positions immediately before the end of crystal growth. In the figure, a double crucible 1 consists of an inner quartz crucible 3 and an outer crucible 4, and is rotatably and vertically supported by a crucible shaft 5. On the outer periphery of the double crucible 1, a heater 9 and a heat insulating cylinder 10 are provided for heating and melting the raw materials in the crucible 1.
is provided and housed in a water cooling chamber (hereinafter referred to as water cooling chamber 12) having an opening 11 at the top. To produce a silicon single crystal using the double crucible described above, the pulling shaft 1 above the double crucible 1 must be
The silicon single crystal seed held in 4 is immersed in the raw material melt 2, and after being blended, it is slowly pulled up and the silicon single crystal 13 is grown while the melt 2 is solidified. As the crystals grow, the raw material melt 2 gradually decreases and the liquid level drops, so the double crucible 1 is gradually raised by moving the crucible shaft 5 to keep the height of the melt 2 level constant. FIG. 2B shows the state immediately before the end of crystal growth. By the above operation, the diameter of the silicon single crystal 13 can be controlled with high precision. Problems to be Solved by the Invention However, when manufacturing a silicon single crystal using the conventional double crucible described above, the relative position of the crucible 1 and the heat insulating cylinder 10 is at the second position when the crystal starts to grow.
However, since the double crucible 1 is gradually raised as the crystal grows as described above, the relative position is the position shown in Figure 2 B just before the end of crystal growth. become. Therefore, in the latter half of crystal growth, the upper edge of the double crucible 1 is
0, the upper edge of the crucible 1 is rapidly cooled, and the temperature of the entire crucible 1 is rapidly reduced. As a result, a problem occurred in that silicon solidified matter 15 began to form from the edge of the melt 2 in the crucible 1, and normal crystal growth was inhibited. Means for Solving the Problems The present invention provides means for solving the above-mentioned conventional problems, and the gist of the first invention of the present invention is to provide an inner In a double crucible consisting of a crucible and an outer crucible for holding the inner crucible, the outer crucible is provided so as to be able to be divided into a plurality of parts in the vertical direction, and the upper part of the outer crucible has a material having a higher thermal conductivity than the lower part. It is in a double crucible made of small materials. Moreover, the gist of the second invention of the present invention is that
In a double crucible consisting of an inner crucible for accommodating the melt and an outer crucible for holding the inner crucible, the outer crucible is divided into a plurality of parts in the vertical direction, and the joints of the divided parts are It is a double crucible that is provided with a spacer with low thermal conductivity in at least one location. The present invention will be explained below based on the drawings. FIG. 1 is an explanatory diagram showing an example of the structure of the double crucible of the present invention and the relative position of the double crucible and the heat-insulating cylinder. In the figure, a double crucible 1 consists of an inner quartz crucible 3 that accommodates a raw material melt 2 and an outer graphite crucible 4 that holds the quartz crucible 3, and is rotatable and vertically movable by a crucible shaft 5. Possibly supported. The crucible 4 made of graphite is divided into an upper part 6 which is a cylinder and a lower part 7 which is a bowl, and a ring-shaped spacer 8 having low thermal conductivity is provided at the joint between the upper part 6 and the lower part 7. On the outer periphery of the double crucible 1, the double crucible 1
A heater 9 and a heat retaining cylinder 10 are provided for heating and melting the raw materials inside, and the chamber is housed in a water-cooling chamber 12 having an opening 11 at the top. Incidentally, FIG. 1 shows the state immediately before the end of crystal growth, that is, the state at the end of the process of pulling the silicon single crystal 13 while being held by the pulling shaft 14. Effect Using the double crucible configured as above,
When producing silicon single crystals by the CZ method, even at the final stage of crystal pulling as shown in Figure 1 above, silicon solidification from the edge of the quartz crucible occurs when a conventional double crucible is used. It doesn't produce things. This is because heat is removed by thermal radiation from the upper part 6 of the crucible 4 protruding from the heat insulating tube 10, and the temperature of the upper part 6 decreases, but since the spacer 8 with low thermal conductivity is provided, the lower part of the crucible 4 The temperature drop in No. 7 is small and is due to the fact that the temperature of the melt does not drop. Examples The following description will be based on examples. Silicon single crystals were produced by the CZ method using the double crucible of the present invention having the configuration shown in FIG. 1, and the crystal growth rate was compared with that when a conventional double crucible was used. The quartz crucible had an inner diameter of 16 inches, and the upper and lower parts of the outer graphite crucible were separated 100 mm above the bottom of the inner surface of the crucible, and a quartz spacer was provided at the joint of the parts. The diameter of the single crystal produced is 6inch. Table 1 shows the crystal growth rate in the latter half of crystal growth. When using a conventional double crucible, it is necessary to reduce the crystal growth rate in order to prevent the formation of silicon coagulum at the edge of the melt in the crucible, whereas with the double crucible of the present invention, it is necessary to reduce the crystal growth rate. In this case, such a deceleration operation is unnecessary, and the crystal growth rate, that is, the production rate, can be greatly improved.

[Table] In this example, a graphite crucible was used on the outside of the double crucible, divided into upper and lower parts, and a spacer with low thermal conductivity was provided at the joint, but the thermal conductivity of the upper part of the crucible was Instead of providing a spacer to reduce the size, high-purity ceramic or other material with low conductivity may be used for the upper part of the crucible. Furthermore, simply dividing the outer crucible is effective in reducing the amount of heat transfer, and the crucible is not limited to being divided into upper and lower halves, but may be divided into three or more. Effects of the Invention As described above, when producing, for example, a silicon single crystal by the CZ method using the double crucible of the present invention as a container for storing a melt of semiconductor raw materials, etc., the upper edge of the outer crucible Even if the temperature drops due to protrusion from the heat insulating cylinder, the temperature at the lower part of the outer crucible can be prevented from dropping, and the formation of silicon coagulates from the edge of the melt can be avoided.
As a result, the crystal growth conditions can be kept constant, and the operation to slow down the crystal growth rate, which was conventionally performed to prevent the formation of silicon coagulation, is no longer necessary, making it possible to significantly increase the production rate. , is extremely effective in practice.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of the structure of a double crucible according to the present invention and the relative positions of the double crucible and the heat-insulating tube, and FIG. 2 is an example of the structure of a conventional double-crucible and the crucible and the heat-insulating tube. FIG. 2 is an explanatory diagram showing the relative position with respect to the crystal growth. 1... Double crucible, 2... Raw material melt, 3...
Quartz crucible, 4... Crucible, 5... Crucible shaft, 6
...Top, 7...Bottom, 8...Spacer, 9...
... Heater, 10 ... Heat insulation tube, 11 ... Opening,
12... Water cooling chamber, 13... Silicon single crystal, 14... Pulling shaft, 15... Solidified material.

Claims (1)

[Scope of Claims] 1. A double crucible consisting of an inner crucible for containing a melt and an outer crucible for holding the inner crucible, wherein the outer crucible is provided so as to be divisible into a plurality of parts in the vertical direction, and A double crucible in which the upper part of the outer crucible is made of a material with lower thermal conductivity than the lower part. 2. The double crucible according to claim 1, in which the outer crucible is divided into two parts: an upper part that is a cylinder and a lower part that is a bowl. 3. In a double crucible consisting of an inner crucible for containing a melt and an outer crucible for holding the inner crucible, the outer crucible is divided into a plurality of parts in the vertical direction, and the joints of each of the divided parts are A double crucible which is provided with a spacer having low thermal conductivity in at least one part of the crucible. 4. The double crucible according to claim 3, wherein the outer crucible is divided into two parts: an upper part that is a cylindrical body and a lower part that is a bowl body, and a spacer is provided at the joint of the upper part and the lower part. 5. The double crucible according to claim 3 or 4, wherein the material of the inner crucible is quartz and the material of the outer crucible is graphite. 6. The double crucible according to claim 3 or 4, wherein the material of the inner crucible is quartz and the material of the outer crucible is ceramic.