JP2570348Y2 - Single crystal growth equipment - Google Patents

Description

[Detailed description of the invention]

[0001]

[Industrial application field] The present invention uses the Czochralski method (CZ).
Method), and an improvement of a single crystal growth apparatus using a molten layer method.

[0002]

2. Description of the Related Art FIG. 4 is a schematic longitudinal sectional view showing a general single crystal growth apparatus utilizing the Czochralski method, wherein 1 is a crucible, 2 is a cylindrical heater made of carbon. ing. A crucible 1 and a heater 2 are arranged concentrically with the crucible 1 in a chamber (not shown). The crucible 1 has an outer layer crucible 1b made of carbon arranged outside an inner layer crucible 1a made of quartz.
The crystal material is put into the inner layer crucible 1a, and the heater 2 is energized to be heated and melted. The heater 2 is heated by energizing through an electrode (not shown) provided at the lower end thereof.

In such a conventional apparatus, after the raw material for crystallization in the crucible 1 is melted, the molten liquid is added to the pulling shaft 3.
A single crystal 5 is grown at the lower end of the seed crystal 4 by immersing the seed crystal 4 suspended at the lower end of the seed crystal 4 and rotating and raising the seed crystal 4.

[0004]

By the way, in the conventional apparatus as described above, the heater 2 is formed in a cylindrical shape having a uniform inner diameter and outer diameter, that is, a constant thickness in the axial direction and the circumferential direction. In addition, since the heat from the central portion of the heater 2 is difficult to escape in addition to the heat radiation from the upper and lower ends of the heater 2, the heat generation distribution in the axial direction of the heater 2 is highest at the central portion of the heater. , It decreases rapidly toward the lower end. Moreover, since the heater 2 is made of carbon, it degrades by reacting with the SiO _X gas evaporating from the surface of the melt.
The degree of this deterioration is such that the reaction proceeds more rapidly in the high-temperature portion, so that the thickness of the heater 2 becomes thinner due to the deterioration in the central portion in the axial direction, and the heating value of the thinned portion is further increased by increasing the resistance value. Increase.

FIG. 5 shows the temperature distribution of the heater 2 at the beginning of use,
5 is a graph showing the temperature distribution after deterioration, in which the abscissa indicates the heat generation temperature, and the ordinate indicates the position of the heater 2 in the axial direction. In the graph, the dashed line shows the temperature distribution at the time of melting the crystal raw material at the beginning of use of the heater, and the solid line shows the temperature distribution at the time of melting the crystal raw material when the number of single crystal pulling batches is 70. As is clear from this graph, even at the beginning of use, the temperature at the center of the heater 2 is higher than the temperatures at the upper and lower ends, but the temperature difference becomes more remarkable as the number of pulling batches increases. I understand.

When the crucible is heated by using such a heater, the crucible 1 is locally heated by the heater 2, so that the crucible is softened and deformed, and the molten liquid is boiled in the vicinity of a region opposed to the center of the heater 2. In addition, there are problems such as melting of the inner layer crucible 1a, dislocation of the single crystal, and reduction of the product yield. The present invention has been made in view of such circumstances, and its purpose is to uniformize the temperature distribution in the axial direction of the heater to suppress local deterioration and prevent local heating of the crucible. It is an object of the present invention to provide a single crystal growth apparatus capable of extending the life and further improving the product yield.

[0007]

According to the present invention, there is provided a single crystal growing apparatus in which a cylindrical heater is arranged around a crucible,
In a single crystal growing apparatus in which a raw material for crystal is melted in a crucible and a single crystal is pulled by dipping a seed crystal in the melt, the heat is distributed in the axial direction to make the heat distribution in the axial direction of the heater uniform. Are characterized in that the thickness of both ends is thinner than the center.

[0008]

According to the present invention, the electric resistance of both ends in the axial direction of the heater is made thinner than that of the central part so that the electric resistance value of both ends is made larger than that of the central part. Thus, the amount of generated heat is increased, and the amount of generated heat in the axial direction can be made uniform.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing embodiments thereof. FIG. 1 is a longitudinal sectional view of a single crystal growth apparatus according to the present invention, in which 11 denotes a crucible, and 12 denotes a cylindrical heater made of carbon. A crucible 11 and a heater 12 are provided concentrically around the crucible 11 in a chamber (not shown). The crucible 11 has a double structure in which an inner layer crucible 11a made of quartz and an outer layer crucible 11b made of carbon are arranged concentrically inside and outside similarly to the conventional apparatus.
The raw material for crystallization put into the furnace is heated and melted by the heater 12.

The heater 12 is formed in a cylindrical shape, and the thickness thereof is gradually reduced toward the upper end and the lower end in a range of 1/4 L of the total length L in the axial direction from both end surfaces. Specifically, the thickness of the upper and lower terminal portions is made 20% thinner than the thickness t of the central portion, and the electric resistance value is increased by that amount to increase the calorific value, thereby making the heat distribution uniform. ing.

[0011] Thus, in such a device of the present invention,
The raw material for the crystal is put into the crucible 11, the heater 12 is operated to dissolve the material, and the seed crystal is suspended in the melt on the pulling shaft 13.
Soak 14 and raise it while rotating it to seed crystal
The single crystal 15 is grown at the lower end of the substrate 14.

FIG. 2 is a graph showing the temperature distribution of the heater in the apparatus of the present invention, in which the abscissa indicates the heat generation temperature and the ordinate indicates the position of the heater 12 in the axial direction. In the graph, the broken line the temperature distribution in the use initial period of the crucible 11, a solid line shows the temperature distribution of the heater 12 when the pulling batch number B _t has reached 70 times. The two-dot chain line shows the temperature distribution when the number of batches is 70 in the conventional apparatus. As is clear from this graph, the temperature distribution in the axial direction of the heater 12 is significantly uniform in both the temperature distribution in the initial stage of use of the heater 12 and the temperature distribution in the 70th pulling batch. I understand. As a result, it was confirmed that the life of the heater 12 can be extended by 30% as compared with the conventional heater having a uniform inner diameter and outer diameter.

FIG. 3 is a graph showing a comparison result of pulling yield of a single crystal between the device of the present invention and the conventional device. The horizontal axis represents the number of batches of pulling (the number of pulled single crystals).
The vertical axis shows the yield. In the graph, the solid line shows the results of the device of the present invention, and the two-dot chain line shows the results of the conventional device. As is apparent from this graph, the yield of the device of the present invention is smaller than that of the conventional device even when the number of pulling batches is increased.

In the above-described embodiment, the case where the heat generation distribution is improved by changing the thickness of the heater in accordance with the position in the axial direction of the heater has been described. Similarly, the heater is disposed in the surrounding chamber. The heat retaining state of the heat retaining material may be appropriately set.

[0015]

As described above, in the device of the present invention, the thickness of the heater at both ends is smaller than that at the center in the axial direction. The exothermic temperature at both ends in the axial direction is relatively higher than that at the center, so that the exothermic temperature is equalized, local heating of the heater and crucible is suppressed, and deterioration of the heater and damage to the crucible are prevented. In addition, the present invention has excellent effects such that the single crystallization rate of the single crystal to be pulled can be improved and the yield can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of the device of the present invention.

FIG. 2 is a graph showing a heat generation distribution in the axial direction of the device of the present invention.

FIG. 3 is a graph showing a comparison result of a single crystal yield between the device of the present invention and a conventional device.

FIG. 4 is a schematic longitudinal sectional view of a conventional crystal growth apparatus using the Czochralski method.

FIG. 5 is a graph showing a heat generation distribution in the axial direction of the heater.

[Explanation of symbols]

 11 crucible 11a inner crucible 11b outer crucible 12 heater 13 pulling shaft 14 seed crystal 15 single crystal

Claims (1)

(57) [Scope of request for utility model registration] 1. A single crystal growing apparatus in which a cylindrical heater is arranged around a crucible, a raw material for crystal is melted in the crucible, and a seed crystal is immersed in the melt to pull up a single crystal. A single crystal growth apparatus characterized in that the thickness of both ends in the axial direction is made thinner than the central portion in order to make the heat distribution in the axial direction of the heater uniform.