JPS61247683A - Pulling device for single crystal sapphire - Google Patents

Abstract

PURPOSE:To inhibit generation of carbon from a heater and to obtain single crystal sapphire of high quality in the titled device provided with a carbon heater by covering an inside wall surface of the carbon heater with tungsten carbide film. CONSTITUTION:A crucible 1 is placed in a chamber 12 and a cylindrical carbon heater 3 is arranged to the external periphery of the crucible 1 and insulated with a heat insulating body 4. The surface of the inside wall of the heater 3 is covered with tungsten carbide film 13 simultaneously. The starting material for sapphire in the crucible 1 is melted by heating with the heater in inert gas, and the molten sapphire 5 is pulled by a pulling shaft 7 holding a seed crystal 6 at the foot end. Thus, a single crystal sapphire is obtd. Since generation of gaseous carbon and carbon particles from the heater 3 are inhibited by this method, occurrence of inclusion in the pulled single crystal sapphire is retarded.

Description

[Detailed description of the invention] [Industrial application field] The invention relates to improvements in the single crystal zapphire pulling device 4.

[Summary of the invention]

The non-invention is a single-crystal pulling device for the Czochralski method (hereinafter referred to as "CZ furnace"), which is one of the devices for producing single-crystal sapphire.
In a CZ furnace that indirectly heats the crucible using a carbon heater as a heater, by testing the inner wall surface of the Tomocarbon heater with tungsten carbide, it was possible to improve the temperature during single crystal pulling. The evaporation of carbon from the carbon heater is suppressed, resulting in the contamination of carbon into the molten sapphire raw material.
By suppressing the reduction reaction caused by carbon in the dopant and the reaction between the reduced dopant and the crucible, the occurrence of inclusions, which are defects in the single crystal sapphire, is reduced.

[Prior art]

Single-crystal sapphire is mainly produced by the Czochralski method-2 (cC2 method). This method is carried out using a CZ furnace shown in FIG.

Hereinafter, a single crystal sapphire pulling apparatus will be explained with reference to the drawings.

FIG. 2 12 shows a chamber with an open top and bottom.

Inside this chamber +2, a Mo crucible 1 is installed,
On the outer periphery of the crucible 1, a cylindrical carbon heater 3 and carbon hot water sampling bodies 4 and 8 are sequentially provided. Further, if necessary, a reflecting plate 2 for controlling the hot water temperature distribution is installed above the crucible. Furthermore, the chamber 12
A pulling shaft 7 holding a seed crystal 6 at its lower end is rotatably suspended from the upper opening.

To pull the single crystal sapphire using the above-mentioned single crystal sapphire pulling device (d), the sapphire raw material (Or, O, Fe, O, etc. as a dopant if necessary) is added to the crucible 1.

The sapphire raw material is melted by the heater 51 and maintained by the heat insulators 4 and 8 and the reflector 2.
M, and while rotating the rotating shaft 7 (also the crucible 1 if necessary), add the seed crystal 6 (at the lower end of the pulling shaft 7) to the molten sapphire 5.
This is done by immersing it in I7 and pulling it up by 7ft using the pulling shaft.

[Important points and objects to be solved by the invention] Prior art] Pulling device d1. The heater 5 and heat insulating body 4 used in
Since No. 8 is made of carbon, it has the following drawbacks.

Inside the single crystal sapphire pulling case + 1ft, the carbon heater is heated to about 2100℃ to 2400℃, so the valley carbon member (carbon heater on the side)
has a vapor pressure, and carbon particles are generated by solidifying carbon gas and hycarbon gas. The generated carbon gas and carbon particles are dissolved or dispersed in the molten sapphire raw material 5 (to which a dopant is added if necessary). The carbon grains dispersed in the sapphire raw material 5 are incorporated into the single crystal during pulling of the single crystal and become crystal defects.

These crystal defects have lowered the yield of single crystals.

In addition, if nickel oxide, chromium oxide, etc. are added as a dopant in the sapphire raw material 5,
These dopants react with carbon dissolved or dispersed in the sapphire raw material 5, and the dopants become magnetic,
nickel or chromium] is formed in the metal. The metal produced here is M.

Reacts with crucible 1 and attacks MO crucible. Since the Mo particles that have reacted with the metal do not evaporate, they are dispersed in the molten raw material 5. The Mo grains are incorporated into the pulled crystal during pulling of the single crystal and become crystal defects. The yield decreased due to these crystal defects. Furthermore, as mentioned above, since the MO crucible is damaged, the crucible can only be used once or twice, which is a major factor in increasing manufacturing costs.

The present invention has been made to solve the above-mentioned drawbacks.

[Means to solve the problem]

A crucible and a cylindrical carbon heater that surrounds the crucible without contacting the crucible are disposed in the chamber, and a heat insulator that surrounds the carbon heater is provided, and the sapphire raw material in the crucible is immersed in an inert gas. The molten sapphire is heated by the cylindrical carbon heater with a force of n to melt it, and the molten sapphire is drawn up using a pulling shaft holding a seed crystal at the lower end while drawing the hot water with a heat insulating body arranged around the outer periphery of the heater. A single-crystal sapphire pulling device for producing single-crystal sapphire by pulling the single-crystal sapphire, characterized in that, among the carbon members, at least the inner wall surface of the heater is coated with tungsten carbide. An example of an uninvented fubi will be explained with reference to the drawings.

Practical example-1 It has the same structure as the single-crystal sapphire pulling device shown in FIG. 2 described above, but as shown in FIG. A sapphire single crystal was pulled by a method similar to the conventional method using a single crystal sapphire pulling apparatus with a different point.

Only M2O was used as a raw material.

Ar gas was used as an atmospheric gas at a rate of 5I/11tI#.

No carbon was found in the pulled sapphire single crystal, and a high quality sapphire crystal was obtained. When using conventional equipment, the yield was 60%, but
When the apparatus of the present invention was used, the yield was 80% or more.

Leprosy Example-2 It has the same structure as the single crystal sapphire pulling device t shown in Fig. 1 described above, but the V3 wall of the moisturizing body 4 and the reflection plate 8 shown in Fig. 1 are coated with a tungsten carbide film. A ruby single crystal was pulled using a single-crystal sapphire pulling device with a different point, using a method similar to the conventional method.

As a raw material, A+! 20. A sintered body in which Cr2O3 was mixed in five injections was used.

Ag/Ee mixed gas was flowed at 21/m as an atmospheric gas.

No carbon or molybdenum particles were found in the pulled ruby single crystal. Further, there were no MO particles mixed in the raw materials remaining in the MO sil crucible. When the conventional device was used, the yield was 50%, but when the inventive device was used, the yield was 80% or more.

〔Effect of the invention〕

As described above, according to the invention, since the generation of carbon gas and carbon particles from the carbon member in the single crystal sapphire pulling device is suppressed, inclusions (carbon particles or molybdenum particles) in the pulled single crystal sapphire are suppressed. ] is suppressed, and not only a high quality sapphire single crystal can be obtained, but also the yield is improved by about 50%.

As described above, the present invention is extremely useful in practice in producing single crystal sapphire.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a CZ furnace showing an example of the uninvented single crystal sapphire pulling device. FIG. 2 is a block diagram of a C2 furnace, which is a conventional single crystal sapphire pulling apparatus. Explanations of the symbols in the figure are as follows. 1... Crucible 2... Reflector 3... Carbon heater 4... Heat insulator 5... Molten raw material 6... Seed crystal 7... Pulling shaft 8... Reflector 9. ...Work coil 10...Gas inlet 11...Gas outlet 12...Chamber 15...Tungsten carbide or more

Claims (1)

[Claims] A crucible and a cylindrical carbon heater that surrounds the crucible without contacting the crucible are disposed in the chamber, and a heat insulator that surrounds the carbon heater is provided, and the sapphire raw material in the crucible is immersed in an inert gas. The molten sapphire is melted by heating with the cylindrical carbon heater, and the molten sapphire is pulled up using a pulling shaft holding a seed crystal at the lower end while being kept warm by a heat insulating body disposed around the outer periphery of the heater. An apparatus for producing single crystal sapphire according to the present invention, wherein at least an inner wall surface of the heater of the carbon member is coated with a tungsten carbide film.