JPH05279170A - Unit for pulling up silicon single crystal - Google Patents

Abstract

PURPOSE:To provide a single crystal-pulling up unit which can inhibit the crystals from becoming polycrystalline and increase the production efficiency. CONSTITUTION:In the silicon single crystal-pulling up unit where molten silicon is held in the quartz crucible, the seed crystal hung down from the top is dipped in the silicon melt and the single crystal is pulled up where the silicon melt is always kept constant at the same level in the quartz 24, a skirt-like thermal insulator 33 is set on the outer periphery of the support 26 for holding the quartz crucible 24 through the graphite crucible 25 so that the tail of the insulator comes near to the heater. Further, in this case, the insulator is constituted from graphite, silicon nitride, silicon carbide, ceramic containing silicon carbide fibers, carbon fibers or their combination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for pulling a silicon single crystal by the Czochralski method (hereinafter referred to as CZ method), and more specifically, it holds a liquid surface of a silicon melt at a constant height. The present invention also relates to a silicon single crystal pulling apparatus for pulling a silicon single crystal.

[0002]

2. Description of the Related Art A schematic view of a conventional example of a silicon single crystal pulling apparatus by the CZ method is shown in FIG. The silicon single crystal pulling apparatus will be briefly described with reference to FIG. 2. The pulling apparatus 1 includes a main chamber 2 and a pull chamber 3 above the main chamber 2, and a gate valve 1a is provided between them.

Here, the lower main chamber 2 has a quartz crucible 4 for holding a silicon melt in the center thereof.
Are provided so as to fit in a graphite crucible 5, and these crucibles 4 and 5 are rotatably supported by a support 6. A heater 7 is provided around the graphite crucible 5, and a heat shield 8 is provided around the heater 7. Furthermore, a diameter control optical system diameter detector 11 for monitoring the diameter of the silicon single crystal 10 pulled up from the silicon melt 9 in the quartz crucible 4 is installed in the shoulder of the main chamber 2.

The pulling of the silicon single crystal by the pulling apparatus 1 configured as described above is carried out by immersing the seed crystal 10a suspended by the wire 12 in the silicon melt 9 in the quartz crucible 4 to form the seed crystal 10a and the quartz crucible. It is carried out by pulling up while rotating 4 and 4 in the same direction or in the opposite direction.

By the way, in order to accurately control the diameter of the silicon single crystal 10, the diameter control optical system diameter detector 11 must always face the interface between the silicon melt 9 and the silicon single crystal 10. However, if the position of the quartz crucible 4 is constant in the height direction, the interface between the silicon melt 9 and the silicon single crystal 10 will move downward as the crystal is pulled up. The diameter control of 10 cannot be performed well.

Therefore, in the conventional pulling apparatus, the diameter control optical system diameter detector 11 is fixedly provided, and the quartz crucible 4 is pushed up by the support 6 by the amount of the silicon melt 9 reduced by the crystal pulling. Therefore, the liquid surface of the silicon melt 9 is always kept constant.

[0007]

However, in the case of pulling the silicon single crystal 10 by the pulling apparatus 1, there have been the following disadvantages in the past.

That is, in the pulling apparatus 1, the heater 7 fixedly provided in the main chamber 2 descends relative to the quartz crucible 4 as the quartz crucible 4 is pushed up. Since the heat capacity of the entire silicon melt 9 is reduced due to the decrease in the amount of the silicon melt 9 and the space under the graphite crucible 5 is widened to increase the heat dissipation, the liquid surface temperature of the silicon melt 9 is initially increased. It will be lower than. As a result, the silicon melt 9 in the quartz crucible 4 solidifies from the surroundings, or SiO evaporated from the liquid surface of the silicon melt 9 adheres to the inner surface of the quartz crucible 4 and solidifies, and this falls into the quartz crucible 4. Then, it was taken into the crystal, and there was a problem that the crystal was polycrystallized.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a pulling device capable of preventing polycrystallization of crystals and enhancing production efficiency.

[0010]

In order to achieve the above object, the present invention is to hold a silicon melt in a quartz crucible, immerse a seed crystal suspended from above into the silicon melt, and pull up a silicon single crystal. In the pulling device for a silicon single crystal, which is designed to always keep the liquid level position of the silicon melt of the quartz crucible at the same height, in the outer periphery of the support that supports the quartz crucible from below through the graphite crucible, The tip is provided with a skirt-shaped heat insulating portion close to the heater. In this case, the heat insulating portion is preferably made of graphite, ceramics containing silicon nitride, silicon carbide and silicon carbide fiber, carbon fiber, or a combination thereof.

[0011]

According to the above-mentioned means, when the crystal is pulled,
Even if the quartz crucible rises, it is possible to effectively use the radiant heat of the heater, and as a result, it is possible to prevent the decrease in the liquid surface temperature of the silicon melt as much as possible and improve the yield, In addition, power consumption can be reduced accordingly.

[0012]

Embodiments of the present invention will be described below with reference to the schematic view of FIG.

The pulling device 21 is composed of a main chamber 22 located below and a pull chamber 23 above it, and a gate valve 20 is provided between the main chamber 22 and the pull chamber 23 so that the chambers 22 and 23 can be separated from each other.

Here, in the lower main chamber 22,
A quartz crucible 24 for holding a silicon melt is provided in the center of the quartz crucible 25 so as to fit in the graphite crucible 25. The crucibles 24 and 25 are supported by the support 26.
It is supported so that it can rotate and move up and down. On the other hand, a heater 27 is provided around the graphite crucible 25,
Further, a heat shield 28 is provided around it. The quartz crucible 2 is installed in the shoulder of the main chamber 22.
An optical system diameter detector 31 for diameter control for monitoring the diameter of the silicon single crystal 30 pulled up from the silicon melt 29 in 4 is installed. The configuration up to this point is similar to the conventional configuration.

In the present embodiment, the heat insulating portion 33 is provided on the outer periphery of the support 26 of the pulling device 21 thus constructed. The heat insulating portion 33 has a skirt shape. The heat insulating portion 33 is not particularly limited, but is made of graphite, ceramics containing silicon nitride, silicon carbide, and silicon carbide fibers are covered with graphite, carbon fibers are covered with graphite, or the like. It is formed of a material having a large heat insulating effect such as a composite body of. When the heat insulating portion is formed of a material that may become a pollution source such as ceramics, it is desirable to completely cover the surrounding area with graphite in order to prevent the inside of the chamber from being polluted. Further, it is desirable that the skirt of the skirt-shaped heat insulating portion 33 extends downward as much as possible, and that the hem is as close as possible to the heater 24.

According to the silicon single crystal pulling apparatus 21 of the embodiment thus configured, the following effects can be obtained.

That is, since the heat insulating portion 33 is provided, even if the quartz crucible 24 rises as the crystal is pulled up, the radiant heat of the heater 27 does not escape below the graphite crucible 25, and as a result, the heater 27 The heat can be effectively used, and the drop of the liquid surface temperature of the silicon melt 29 can be prevented as much as possible, the yield can be improved, and the power consumption can be correspondingly reduced. By the way, taking an 8-inch silicon single crystal pulling machine as an example, the average power of the conventional apparatus was 140 kW, but it could be reduced to 134 kW in this example. Further, in the conventional case, there was about 20% of the crucible residue of the silicon melt even when the average power was 140 kW, but in the case of this example, the crucible residue could be almost eliminated.

Although the pulling device according to the embodiment of the present invention has been described above, the present invention is not limited to the embodiment and various modifications can be made without departing from the scope of the invention. There is no end.

[0019]

As described above, according to the present invention, a silicon melt is held in a quartz crucible, a seed crystal suspended from above is immersed in the silicon melt, and a silicon single crystal is pulled up. In the crystal pulling device, on the outer periphery of the crucible support that supports the quartz crucible from below,
Since the skirt-shaped heat insulator whose hem is close to the heater is provided, it is possible to prevent the drop of the liquid surface temperature of the silicon melt as much as possible, and the yield is improved. Power consumption can also be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a lifting machine according to an embodiment.

FIG. 2 is a schematic view of a conventional pulling machine.

[Explanation of symbols]

 21 pulling machine 24 quartz crucible 26 support 27 heater

Claims (2)

[Claims] 1. A silicon melt is held in a quartz crucible,
A seed crystal hung from above is immersed in the silicon melt, and in pulling up the silicon single crystal, in a silicon single crystal pulling device that always holds the liquid level position of the silicon melt in the quartz crucible at the same height. A pulling device for a silicon single crystal, characterized in that a skirt-shaped heat insulating portion having a hem near the heater is provided on the outer periphery of a support that supports the quartz crucible from below via a graphite crucible. 2. The heat insulating portion is made of graphite, ceramics containing silicon nitride, silicon carbide and silicon carbide fiber, carbon fiber, or a combination thereof. Silicon single crystal pulling device.