JP2947152B2 - Single crystal manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a single crystal by the Czochralski method (hereinafter simply referred to as "CZ method"). The present invention relates to a lower structure of a single crystal manufacturing apparatus for preventing an accompanying accident from occurring.

[0002]

2. Description of the Related Art There are various methods for producing a single crystal, and the CZ method is widely applied in a method capable of mass production. The single crystal manufacturing apparatus used in this method is configured by disposing a crucible for accommodating a crystal forming material in a cylindrical metal chamber, and a heater disposed around the crucible.

FIG. 2 is a longitudinal sectional view illustrating a lower structure of a single crystal manufacturing apparatus using the CZ method. Usually, the crucible 1 used for the production of a silicon single crystal has a double structure, which includes an inner quartz container 1a and an outer graphite container 1b, and is set on a crucible support shaft 1c. A heater 2 is provided outside the crucible 1, and a material for crystal formation melted by the heater, that is, a melt 3 of polycrystalline silicon as a raw material is accommodated in the crucible 1.
The lower end of a seed crystal attached to the tip of pulling means (not shown) is brought into contact with the surface of the melt 3, and the seed crystal is pulled upward to grow a single crystal solidified with the melt at the lower end. . These parts and members are housed in the metal chamber 4 and constitute a single crystal manufacturing apparatus as a whole.

When a silicon single crystal is produced by the CZ method, the silicon melt 4 contained in the crucible is eluted from the quartz (SiO ₂ ) in the crucible container in order to grow the silicon single crystal from the silicon melt in the quartz container. Contains oxygen. Therefore, during the pulling of the single crystal, silicon monoxide (SiO 2) evaporating from the surface of the molten liquid and monoxide generated by a reaction between the silicon monoxide and a high-temperature graphite member such as the heater 2 and the graphite container 1b. Carbon (CO) is generated. Especially,
The fine powder or massive precipitate of silicon monoxide (SiO 2) adheres to the upper surface or side surface of the metal chamber 4 and falls on the surface of the melt 3 as the single crystal is pulled up, and this is taken into the crystal growth interface. As a result, dislocation of the crystal is caused.

During the pulling of the single crystal, a high-purity argon gas is always supplied as an inert gas from an upper central portion of the metal chamber 4 in order to remove deposits and the like of silicon monoxide. A gas flow is formed therein. This gas flow is discharged from the gas discharge pipe 5 together with silicon monoxide evaporated from the surface of the silicon melt 3 stored in the crucible and carbon monoxide generated by a reaction with the graphite member. As shown in FIG. 2, the gas discharge pipe 5 is provided on the bottom surface 4a of the metal chamber together with the leak receiving tray 6.

As described above, the crucible used for producing a silicon single crystal has a double structure, which is composed of an inner quartz container and an outer graphite container, and these containers have excellent heat resistance. However, it has the disadvantage that it is brittle and has poor impact resistance. Therefore, when the polycrystalline silicon raw material is charged into the crucible at the time of initial charging, a crack is generated in the crucible by the impact at that time, and a high-temperature molten liquid may flow out of the cracked portion out of the crucible during the pulling process. Also,
When a polycrystalline silicon raw material is charged during recharging, the melt contained in the crucible may scatter around. For this reason, the above-mentioned liquid leakage receiving tray 6 is attached to the bottom surface 4a of the metal chamber.
It is provided in.

However, if the high-temperature molten liquid 3 flows out or scatters out of the crucible during the pulling process, the molten liquid 3 is collected in the liquid leakage tray 6 provided on the bottom surface of the metal chamber, but causes a new accident. There is a risk. That is, the high-temperature silicon melt 3 flowing out has a strong erosion effect, and erodes the seal portion 7 provided between the liquid leakage tray 6 and the gas discharge pipe 5. Further, when a large amount of silicon melt flows out due to recent pulling of a heavy single crystal, the melt 3 collected in the leak receiving tray 6 is discharged to the gas discharge pipe 5.
It may flow into the inside. Once the seal part is eroded or the molten liquid flows into the gas discharge pipe, the cooling pipe provided in the metal chamber is easily damaged, the cooling water evaporates, and the high pressure steam is generated in the metal chamber. Will cause a steam explosion.

In the single crystal manufacturing apparatus, the cleaning operation of the gas discharge pipe is periodically performed, but there is a problem in this operation.
As described above, during the pulling of the single crystal, the argon gas with silicon monoxide that evaporates from the surface of the silicon melt 3 is always discharged from the gas discharge pipe 5. Therefore, silicon monoxide easily adheres to the inner surface of the gas discharge pipe 5, and when the adhesion becomes excessive, the gas flow in the metal chamber is obstructed. In order to prevent this, an operation of periodically removing silicon monoxide attached to the gas discharge pipe is performed. However, since the attached silicon monoxide easily causes an oxidation reaction, a dust explosion may occur during the operation of removing the silicon monoxide. Especially,
When a heavy single crystal is pulled, the amount of silicon monoxide attached tends to increase each time the single crystal is pulled, which is a problem to be noted.

[0009]

SUMMARY OF THE INVENTION The present invention overcomes the above-mentioned problems of the prior art and, even when pulling a heavy single crystal, causes accidents and mono-oxides caused by the melt flowing out of the crucible. It is an object of the present invention to provide a single crystal manufacturing apparatus having a lower structure for preventing occurrence of an accident accompanying a silicon removing operation.

[0010]

The gist of the present invention is the following single crystal manufacturing apparatus as shown in FIG.

That is, a single crystal formed by a Czochralski method, comprising a crucible 1 containing a raw material melt of a single crystal to be grown, a heater 2 for heating the melt, and a metal chamber 4 containing the above members A manufacturing apparatus, comprising: a plurality of gas discharge pipes 5 having an effective inner diameter of 80 mm or more, which are disposed on a bottom surface 4a of the metal chamber and close to a cylindrical inner wall surface 4b of the metal chamber; An apparatus for producing a single crystal, characterized in that a liquid leakage tray 6 disposed on the inner periphery is provided.

Here, "disposed close to the inner wall surface of the cylinder of the metal chamber" means that the gas discharge pipe may be arranged so as to be in contact with the inner wall surface of the cylinder of the metal chamber, or may be fixed to the inner wall surface of the cylinder. Means that they may be arranged at intervals. Also, "disposed on the inner periphery of multiple gas discharge pipes"
This means that the liquid leakage tray is disposed at the center of the bottom surface of the metal chamber, and a plurality of gas discharge pipes are provided on the outer periphery thereof.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A lower structure of a single crystal manufacturing apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an example of a lower structure of a single crystal manufacturing apparatus according to the present invention. As is apparent from the figure, the metal chamber 4 constituting the appearance of the manufacturing apparatus is a cylindrical vacuum vessel provided with a cooling pipe (not shown), and is arranged around a single crystal pulling axis. I have.
A crucible 1 is provided at a central position of the metal chamber 4, and a heater 2 surrounding the crucible 1 and heating the melt 3 in the crucible is provided around the crucible 1. The crucible 1 has a double structure with a quartz container 1a on the inside and a graphite container 1b on the outside. The crucible 1 is installed on a crucible support shaft 1c, and can rotate and move up and down.
On the other hand, on the bottom surface 4a of the metal chamber, a liquid leakage tray 6 is disposed at a center position with respect to the crucible support shaft 1c, and between the liquid leakage tray and the cylindrical inner wall surface 4b of the metal chamber, liquid leakage occurs. A plurality of gas discharge pipes 5 are provided on the outer periphery of the tray.

The present invention is characterized in that the gas discharge pipe 5 is arranged on the outer periphery of the liquid leakage receiving tray 6 and close to the cylindrical inner wall surface 4b of the metal chamber. The reason for disposing the gas exhaust pipe close to the inner wall surface of the cylinder of the metal chamber is to remove the arrangement position of the gas exhaust pipe from the liquid leakage tray and to arrange the gas exhaust pipe so as to surround the liquid leakage tray. is there. With this configuration, even if the high-temperature molten liquid flows out or scatters out of the crucible during the pulling process, the molten liquid is only collected in the liquid leakage tray, and the gas discharge pipe is connected to the molten liquid. And the melt does not flow into the gas discharge pipe. For this reason, the cooling pipe of the metal chamber is damaged, and an accident of steam explosion can be prevented. The position where the gas discharge pipe is arranged close to the inner wall surface of the cylinder of the metal chamber may be in contact with the inner wall surface of the cylinder, or may be arranged at a fixed distance from the inner wall surface of the cylinder. In any case, a plurality of gas discharge pipes may be arranged so as to surround the liquid leakage tray.

In the present invention, the effective inner diameter of the gas discharge pipe is
Must be at least 80mm. Conventionally, when the inner diameter of the gas discharge pipe is small, for example, when pulling a heavy single crystal (weight 115 kg to 190 kg) having a diameter of 8 inches and 12 inches, when using a gas discharge pipe having an effective inner diameter of 60 mm, In the case of, dust explosion often occurred during the operation of removing silicon monoxide attached to the inner surface of the gas discharge pipe.

From the experience of the conventional work, the effective inner diameter of the gas discharge pipe was required to be 80 mm or more. However, the upper limit is desirably 150 mm for the structural reasons of the single crystal manufacturing equipment.

A plurality of gas discharge pipes are required in the circumferential direction of the bottom surface of the metal chamber. The number of gas discharge pipes is determined by the distribution of argon gas. In general, the flow rate Vg of the argon gas depends on the gas supply pressure Pg, the gas flow rate Qg, the gas passage space sectional area Ag, and the furnace pressure Pf, and is expressed by the following equation (1).

Vg = (Qg / Ag) × (Pg / Pf) (1) From the above equation (1), to maintain a constant argon gas flow state, that is, to ensure a gas flow rate Vg and a gas flow rate Qg It can be seen that the cross-sectional area Ag of the gas passage space is required. Therefore, the required number of gas discharge pipes is determined in order to secure a predetermined gas passage space sectional area Ag, and these gas discharge pipes are arranged in the circumferential direction on the bottom surface of the metal chamber.

The liquid leakage tray is arranged on the inner periphery of the gas discharge pipe. That is, the liquid leakage tray is disposed at the center of the bottom surface of the metal chamber, and a plurality of gas discharge pipes are installed on the outer periphery of the liquid leakage tray. With this configuration, even if the high-temperature molten liquid flows out or scatters out of the crucible during the pulling process, the molten liquid is merely collected in the liquid leakage tray, and the gas discharge pipe erodes the molten liquid. It does not occur or the molten liquid flows into the gas discharge pipe, so that a steam explosion can be prevented. Further, the maximum capacity that the liquid leakage tray can collect is determined by the weight of the single crystal to be pulled. For example, in the case of pulling a heavy single crystal having a diameter of 8 inches and 12 inches (weight of 115 kg to 190 kg), a melt amount of 120 Kg is required in consideration of the initial charge amount.
A recovery capacity of g to 200 kg is required.

It is desirable that the liquid leakage tray is made of graphite. Graphite is relatively lightweight and easy to handle, and has a sublimation temperature exceeding 3000 ° C. and has excellent heat resistance, so it is suitable as a heat-resistant heat insulating material. Furthermore, because graphite can be produced with high purity, even if it is arranged in a single crystal production apparatus, there is little risk of contamination of the pulled crystal by heavy metals or the like.

[0022]

According to the apparatus for producing a single crystal of the present invention, even when pulling a heavy single crystal, a steam explosion caused by the molten liquid flowing out of the crucible and a dust explosion accompanying the work of removing silicon oxide are prevented. Generation can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of a lower structure of a single crystal manufacturing apparatus of the present invention.

FIG. 2 is a longitudinal sectional view illustrating a lower structure of a single crystal manufacturing apparatus using a conventional CZ method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Crucible, 1a ... Quartz container, 1b ... Graphite container, 1c ... Crucible support shaft 2 ... Heater, 3 ... Melt 4 ... Metal chamber, 4a ... Bottom of metal chamber,
4b… Cylinder inner wall surface 5… Gas discharge pipe 6… Liquid leakage tray 7… Seal part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-9-118583 (JP, A) JP-A-5-319996 (JP, A) JP-A-6-56570 (JP, A) JP-A-5-1997 270967 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C30B 1/00-35/00

Claims (1)

(57) [Claims] An apparatus for producing a single crystal by a Czochralski method, comprising: a crucible containing a raw material melt of a single crystal to be grown; a heater for heating the melt; and a metal chamber containing the member. There, on the bottom surface of the metal chamber, a plurality of gas discharge pipes having an effective inner diameter of 80 mm or more disposed close to the cylindrical inner wall surface of the metal chamber, and disposed on the inner periphery of the plurality of gas discharge pipes. An apparatus for producing a single crystal, comprising a liquid leakage tray.