JPS6018638B2 - Silicon single crystal pulling equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in silicon single crystal pulling equipment.

Silicon single crystals are mainly produced by the Czokolafsky method (CZ method).

In this method, polycrystalline silicon raw material is placed in a rubbo, heated from the surroundings to melt the polycrystalline silicon, and the melt is pulled upward using a seed crystal to produce a single crystal.
By the way, the pulling device used in the above CZ method has conventionally been
Lubbo is constructed by providing a graphite container on the outer periphery of a Lubpo main body made of quartz glass to prevent plastic deformation of the main body,
It has a structure in which this is layered in a chamber in which a heater and the like are provided.

However, when melting the polycrystalline silicon raw material in the crucible and pulling up the melt with such a pulling device, the crucible body made of quartz glass, the protector made of graphite, and the force Si02(S)
+C(S)→Si02{g-10CO{g' reaction is 13
It starts at around 00℃ and reaches about 1500qo by the time the single crystal pulling operation is carried out, so the CO generated is
and SiO gas is mixed into silicon. In addition, since molten polycrystalline silicon is in direct contact with the Rubbo body made of quartz glass, Si02(S) + Si(S) → Rui○(g
} reaction occurs, and the quartz glass component is directly mixed into the silicon.

As a result, the silicon single crystal after pulling contained carbon at a concentration of 3 × 1 and Mom/cc and oxygen at a concentration of 1 and 8 am/cc, which became the nucleus for the formation of micro defects and caused large imperfections in the crystal. This was one of the causes. The present invention has been made in order to eliminate the above-mentioned drawbacks, and aims to provide a silicon single crystal pulling apparatus capable of producing a high purity silicon single crystal with extremely low levels of carbon and oxygen contamination. Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In the figure, 1 is a chamber whose upper and lower parts are closed, and Rubbo 2 is arranged inside this chamber 1, and Rubbo 2 is placed on a rotatable support rod 3 inserted from the lower entrance of the chamber 1. has been done.

This crucible 2 is composed of a graphite base material 4 and a silicon nitride film 6 coated on the surface of the graphite base material 3 with a silicon carbide film 5 interposed therebetween. Furthermore, a cylindrical graphite heater 7 and cylindrical heat shields 8 and 9 are sequentially arranged around the outer periphery of the rubbo 2 .

The lower end of the graphite heater 7 is bent inward, and a ring-shaped insulating plate 11 is interposed between the bent part 10 and the lower part of the chamber 1, and is screwed from the bent part 10 to the lower part of the chamber 1. The heater 7 is fixed to the chamber 1 with bolts 12 . Furthermore, a pulling chain 14 holding a seed crystal 13 at its lower end is rotatably suspended from the upper entrance of the chamber 1. According to such a configuration, when the polycrystalline silicon raw material is put into Rubbo 2 and the heater 7 is energized to heat Rubbo 2, the polycrystalline silicon raw material is melted and becomes molten silicon 15.

In this state, while rotating the crucible 2 with the support rod 3, the seed crystal 13 at the lower end of the pulling chain 14 is immersed in the molten silicon 15 inside the crucible 2, and pulled up while rotating.
A silicon single crystal having a predetermined crystal orientation is manufactured. Therefore, in the process of melting the polycrystalline silicon and pulling the silicon single crystal, Rubbo 2 has a temperature of 1300 to 1500
Although the crucible 2 is heated to a high temperature of approximately
This further prevents carbon and oxygen from entering the molten silicon 15. Moreover, since the silicon nitride film 6 on the outer surface of the rubbo 2 does not directly contact the graphite base material 4 and is covered with the silicon carbide film 5, the silicon nitride film 6 on the graphite base material 4 under high temperature can prevent the reduction of That is, when a silicon nitride film is directly coated on a graphite base material, the silicon nitride film is reduced by the graphite base material under high temperature and decomposed into active Si and N2. Even if Si in the decomposition product mixes into molten silicon, it does not become an impurity source, but when active N2 mixes into molten silicon, it produces Si3N4 and becomes an impurity source for the pulled silicon single crystal. However, crucible 2
By coating the graphite substrate 4 with a silicon nitride film 6 via a silicon carbide film 5 that has good adhesion to both the base material and silicon nitride, the silicon nitride film 6 is reduced at high temperatures. , decomposition can be inhibited and Si3N4 can be prevented from being generated in molten silicon. Therefore, according to the pulling device of the present invention, not only can the incorporation of carbon and oxygen into the molten silicon in the crucible be suppressed to the utmost, but also Si3N4 in the molten silicon can be suppressed as much as possible.
Since the formation of silicon can be prevented, it is possible to produce a silicon single crystal with good crystallinity and less impurities that become the nucleus of microdefect formation.

In fact, it was confirmed from the following experimental example that a good silicon single crystal could be produced.

Experimental Example 1 Graphite with an apparent specific gravity of 1.75 m/cc and a coefficient of thermal expansion of 3.0 x 10-6/°C was processed and subjected to high purity treatment to produce a Rubbo-shaped graphite base material.

Next, this graphite substrate was placed in a furnace maintained at 1,400 qo, and the rate of SIC17 was 8cc/min, and the rate of SIC17 was 20cc/min.
After introducing 0 cc of NH3 gas per minute and causing Si to be separated out on the surface of the substrate and simultaneously reacting with the graphite of the substrate to form SIC for 5 minutes, NH3 gas was further introduced at 100 cc per minute to form Si on the SIC film. A Si3N4 film was deposited for 30 minutes to form a 1.5 m thick silicon carbide film on a graphite substrate through a 50 mm thick silicon carbide film.
A rubbo coated with a silicon nitride film of 00 Am was manufactured.
Experimental Example 2 First, graphite having an apparent specific gravity of 1.60 m/cc and a coefficient of thermal expansion of 4.2 x 10-6/°C was processed to produce a Rubbo-shaped graphite base material.

Next, this base material was placed in a furnace maintained at 1300 qo, and SIC 4 was heated at 8 cc/min and C74 was heated at 10 cc/min.
, Day 2 was introduced at 200 cc per minute, and after forming a 20 mm thick SIC film on the substrate surface, the introduction of C7 Day 8 was stopped.
Instead, introduce an N ratio of 100 cc per minute to a thickness of 1 on the SIC.
Rubbo was manufactured by depositing a 50 m thick Si3N4 film.
Therefore, the Rubbo of Experimental Examples 1 and 2 above and the Luppo with a graphite protector provided on the outer periphery of the Si02 Rubbo body (Comparative Example 1)
A pulling device was constructed of Rubbo (Comparative Example 2) in which the surface of a graphite base material was coated with a silicon nitride film, and a silicon single crystal was manufactured using these pulling devices.

When the carbon concentration and Si3N4 intervening state of each silicon single crystal obtained were investigated, the results were as shown in the table below. It should be noted that the constituent members of the silicon single crystal pulling apparatus according to the present invention, such as the heater other than the lug, are not limited to the above-mentioned embodiments, and can be arbitrarily changed in design.

As detailed above, according to the present invention, in the process of melting and melting the polycrystalline silicon in the Lubbo and pulling the molten silicon, it is possible to not only suppress as much as possible the incorporation of carbon and oxygen into the molten silicon in the Lubbo, but also to S in molten silicon
It is possible to provide a Sea J-Con single crystal pulling apparatus that can prevent the generation of i3N4 and thereby produce a good silicon single crystal with extremely few impurities that become the nucleus of microdefect formation.

[Brief explanation of drawings]

The figure is a sectional view of a silicon single crystal pulling apparatus showing an embodiment of the present invention. 1...Chiyamba, 2...Rubbo, 3...Support, 4.
...Graphite base material, 5... Silicon carbide film, 6... Silicon nitride film, 13... Seed crystal, 14... Pulling chain,
15. ．． ．． molten silicone.

Claims (1)

[Claims] 1. In a pulling device that places a crucible in a chamber and pulls up molten silicon in the crucible to produce a silicon single crystal, the crucible is coated with a silicon nitride film on the surface of a graphite base material via a silicon carbide film. A device for pulling a silicon single crystal, which is characterized by a structure in which: