JPH03131591A - Method for growing crystal and device for dissolving crystal raw material - Google Patents

Abstract

PURPOSE:To shorten the time for the growth of a single crystal and improve the yield of the crystal by employing a raw material forming a solid layer after once melting all of the raw material to eliminate spaces contained therein and subsequently solidifying the melted material when the single crystal is grown by a melting layer method. CONSTITUTION:In a method wherein a solid layer 5 comprising the substantially same material as that of a melted layer 4 is formed under the melted layer 4 comprising a melted crystal material and melted to control the volume of the melted layer 4, and the melted material is lifted and subsequently solidified to grow a single crystal, a material prepared by once melting the crystal material and subsequently solidifying the melted material is employed for the melted layer 4, thereby permitting to prevent the change of the melted material surface caused by the floating up of gases contained in the raw material, readily seed the melted layer when the lifting operation is started, and prevent the breakage of the single crystal during the lifting operation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for growing a crystal such as a silicon single crystal used as a semiconductor material, for example, and a crystal raw material melting apparatus used therefor.

[Conventional technology]

There are various crystal growth methods, one of which is the pulling method (Chickralski method).
As shown in the figure, after all of the crystal raw material inserted into the crucible 1 is melted, the molten liquid 4 is pulled up into a keyaki or wire 10.
By guiding the seed crystal 6 attached to the tip of the seed crystal 6 and pulling it upward, the melt 4 solidifies at the lower end of the seed crystal 6 and a crystal 7 grows.

When growing semiconductor single crystals using this method, impurity elements are often added to the melt before pulling in order to adjust the electrical resistivity and electrical conductivity type of the crystal. In the Chickralski method, the electrical resistance in the pulling direction is not uniform.

Segregation of impurities occurs due to the ratio C3/CI! of impurity concentration Cs in the crystal to impurity concentration CZ in the melt at the interface between the melt and the crystal during crystal growth. That is, since the effective segregation coefficient Ke is not 1, the concentration of impurities in the melt and eventually in the crystal changes as the crystal grows.

A fused layer method is known as a crystal growth method that prevents the segregation of impurities. The fused layer method, as shown in Figure 4,
This is a method in which a solid layer 5 made of substantially the same material as the melt is formed below the melt layer 4, and the crystals 7 are pulled up from the melt layer 4.

In the molten layer method, the volume of the molten liquid layer 40 is kept constant while the lower solid layer 5 is melted as the crystal is pulled up, and impurities are continuously added during crystal pulling to keep the impurity concentration in the molten liquid constant. Constant melt layer thickness method (Japanese Patent Publication No. 34-8242).

JP 63-252989, JP 62-880,
Utility Model Application No. 60-32474) or the melt layer thickness variation method (special application method) in which the impurity concentration in the melt is kept constant without adding impurities during crystal pulling by intentionally changing the volume of the melt layer. Patent application No. 1983-45602, patent application No. 1983
No. 45603 and Japanese Patent Application No. 60-57174) are known.

[Problem to be solved by the invention]

In the conventional molten layer method as described above, crystal pulling is started when only the upper part of the granular pieces (chips), bulk materials (lamps), etc. packed in the crucible as the raw material for the solid layer 5 is melted. Therefore, voids are created in the solid layer 5, and the gas inside them floats up and changes the scene, making it difficult to seed the seed crystal at the beginning of pulling, and also causing the crystal being pulled to break during crystal growth. There was a problem that the program would be interrupted.

The present invention was made to solve this problem, and by melting all the raw materials that will become the solid layer to eliminate voids, and then resolidifying the material, the crystal growth time can be shortened. The purpose of the present invention is to provide a crystal growth method with a high yield of crystals and a crystal raw material melting device for pretreatment used therein.

[Means to solve the problem]

The crystal growth method of the present invention includes forming a solid layer of substantially the same material as the melt layer below the melt layer in which the crystal material is melted;
In a method in which the solid layer is melted and the volume of the molten liquid layer is controlled while the molten liquid is pulled up and solidified to grow crystals, a material that has been once melted and solidified is used as the molten liquid by remelting the crystal raw material. It is characterized by

Further, the crystal raw material melting apparatus used to carry out the crystal growth method of the present invention includes a crucible that stores the crystal raw material, a heater that heats and melts the crystal raw material stored in the crucible, and a cooling system that cools the heated and melted crystal raw material. It is characterized by having the following.

[Effect]

In the crystal growth method of the first invention, the crystal raw material is once melted and solidified, and then the crystal is pulled up by remelting the material, so that the gas in the raw material does not float up and change the situation, and when the pulling starts. seeding becomes easier and the crystals do not break during pulling, thus reducing operational troubles and improving crystal growth efficiency.

If the raw material is once melted and solidified using the apparatus of the second aspect of the invention and is then provided to the crystal growth apparatus, time loss in the crystal growth apparatus can be avoided. Furthermore, since this apparatus has a cooling system, the time required for solidifying the once melted raw material can be further shortened.

(Example) Hereinafter, the present invention will be described based on drawings showing examples thereof.

FIG. 1 is a schematic diagram showing the implementation state of the crystal growth method of the present invention (hereinafter referred to as the method of the present invention), and 1 in the figure is a crucible. The crucible 1 is placed in the center of the chamber 8, and surrounding it is a heater 2 that is movable up and down and is made up of an induction heating coil, etc., and a heat insulating tube 3 is placed outside of the crucible 1. By adjusting the relative upward and downward positions of the crucible 1 and the heater 2, the depth of the molten liquid layer 4 and the thickness of the solid layer 5 in the crucible 1 can be relatively adjusted.

The crucible 1 has a double structure with a quartz container 1b arranged inside a graphite container 1a, and a shaft 1c for rotating and raising and lowering the crucible 1 is provided at the bottom of the graphite container 1a. , the crucible 1 is rotated and/or raised and lowered by the shaft 1c.

A pulling shaft 10 is vertically installed above the crucible 1 so as to be able to rotate and move up and down through a pull chamber 9 provided at the top of a chamber 8. A seed crystal 6 is removably attached to the lower end of the pulling shaft 10. After dipping the lower end into the melt layer 4,
By raising this while rotating it, a single crystal 7 is grown at the lower end of the seed crystal 6.

In the first invention method when using a crystal growth apparatus, before starting the main crystal growth process, first, a solid material of polycrystalline silicon, which is a lamp or a chip, is placed in a crucible l, and a single crystal to be pulled is placed in a crucible l. After charging the amount determined from the volume of , the heater 2 is raised and the solid material is melted from the bottom so that all the voids are eliminated.Then, the furnace is cooled to -degree room temperature to solidify the solution. This is a pretreatment for forming the solid layer 5.

Thereafter, by controlling the temperature and/or position of the heater 2, the molten liquid layer 4 is formed in the upper part of the crucible 1, and the solid layer 5 is formed in the lower part thereof to the required depth or thickness. After a seed crystal 6 is immersed in the layer 4, it is pulled up while being rotated, and a single crystal 7 is grown at its lower end.

When pulling about 80 aIl of single-crystal silicon with a diameter of 6 inches, the conventional method had an average of 5 interruptions in crystal growth, but the method of the present invention almost eliminates the interruptions. Furthermore, while seeding at the start of pulling conventionally required an average of 7 to 8 hours, according to the method of the present invention, it can be completed in 2 to 3 hours.

In addition, the pretreatment work of melting and solidifying the solid material is performed using the apparatus shown in Figure 2, and the re-solidified solid material from which voids have been removed is placed in the crucible of the crystal growth apparatus for main processing as shown in Figure 1. 1
Compared to the conventional method of putting the lamps and chips directly into the crucible 1 of the crystal growth apparatus for main processing, we succeeded in reducing the time by about 40 minutes, and obtained the same effect as in the above example. It was done.

FIG. 2 is a schematic cross-sectional view showing the configuration of the crystal mulberry melting apparatus of the second invention, which is basically similar in configuration to the heating section of the crystal growth apparatus shown in FIG. 1. 1 in the figure is a crucible, and the crucible 1 is placed in the center of the chamber 8, and on its outer periphery there is a heater 2, which is movably arranged to be raised and lowered and is made up of an induction heating coil, and further outside the crucible. A heat insulating cylinder 3 that can be raised and lowered is disposed in the holder, and the melt layer 1 in the crucible 1 is adjusted by adjusting the relative upward and downward positions of the crucible 1 and the heater 2.
2 and the thickness of the resolidified layer 11 can be relatively adjusted. The crucible 1 has a double structure in which a quartz container 1b is arranged inside a graphite container 1a,
A support stand 13 and a support stand 13 are provided at the bottom of the graphite container 1a.
A shaft 1c is provided for rotating and raising/lowering the crucible 1 placed on the shaft 1c.
Or it can be raised and lowered.

The support stand 13 is connected to the shaft 1c and has a cooling system connected to a coolant supply device (not shown) that circulates and supplies coolant. The coolant passes through the coolant passage 14 to cool the support stand 13, and by accelerating the cooling rate of the crystal raw material after melting, the operating time can be shortened. Since the necessary functions of the support stand 13 are to support the crucible and to accelerate the cooling rate, it goes without saying that it may have an integral structure with the graphite container 1a.

This pretreatment device performs pretreatment to melt the lamps and chips packed in the crucible 1 from below to eliminate voids, and then solidify the solution.

In this embodiment, an induction heating coil was used to heat the molten liquid, but it goes without saying that the present invention is also possible with a resistance heating type heater.

〔Effect of the invention〕

The method and apparatus of the present invention have the excellent effect of preventing the hot water level from being captured due to the boiling up of gas in the solid layer, improving the yield of crystals by preventing interruption of crystal growth, and shortening the time required for seeding. play.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a crystal growth apparatus showing the implementation state of the method of the present invention, FIG. 2 is a schematic cross-sectional view of the pretreatment apparatus of the present invention, and FIGS. 3 and 4 are the implementation states of the conventional method. FIG. 2 is a schematic cross-sectional view of a crystal growth apparatus showing. 1... Crucible 1a... Graphite container 1b... Quartz container 1c... Shaft 2... Heater 3... Heat retention cylinder 4... Molten liquid layer 5... Solid layer 6.・・Seed crystal
7... Single crystal 8... Channel noma 9... Pull chamber 10... Pulling shaft 11... Resolidified layer 12... Molten liquid layer 13... Support stand 14... Coolant passage patent

Claims (1)

[Claims] 1. A solid layer made of substantially the same material as the molten liquid layer is formed below a molten liquid layer obtained by melting a crystalline material, and the volume of the molten liquid layer is controlled by melting the solid layer. A method for growing crystals by pulling up and solidifying a molten liquid, the crystal growth method being characterized in that a crystal raw material that has been once melted and solidified is remelted and used as the molten liquid. 2. A crystal raw material melting device characterized by comprising a crucible for storing a crystal raw material, a heater for heating and melting the crystal raw material stored in the crucible, and a cooling system for cooling the heated and melted crystal raw material.