JPH09241094A - Production of semiconductor single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a single crystal from having the dislocation occurring in the deterioration by the thermal load of a quartz crucible and to efficiently melt the Jumpy raw materials loaded in this quartz crucible in the production of a semiconductor single crystal by a CZ method or the CZ method involving the execution of continuous charging. SOLUTION: The lumpy raw materials 5 are heated by a main heater 2 enclosing the quartz crucible 1 and rod melting heaters 21 of raw material supplying devices 20 installed above the quartz crucible 1 and the electric power to be supplied to the main heater 3 is dropped down to a prescribed value at the time of melting the lumpy raw materials 5 of the polycrystalline silicon loaded in the quartz crucible 1 in the production of the semiconductor single crystal by a continuous charging method. As a result, the thermal load to be applied on the quartz crucible 1 is made smaller and the deterioration thereof is suppressed. In addition, the lumpy raw materials 5 are heated from a transverse direction and above and, therefore, the melting is executed more rapidly than heretofore.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor single crystal, and more particularly to a method for manufacturing a semiconductor single crystal which efficiently dissolves a bulk material loaded in a quartz crucible.

[0002]

2. Description of the Related Art Generally, high-purity single crystal silicon is used for a substrate of a semiconductor element, but the Czochralski method (hereinafter referred to as CZ method) is mainly used for its production. In the CZ method, a graphite crucible is placed on the upper end of a crucible shaft installed in a chamber of a semiconductor single crystal manufacturing apparatus via a crucible receiver, and a quartz crucible housed in the graphite crucible is loaded with polycrystalline silicon. The polycrystalline silicon is heated and melted by a heater provided around the graphite crucible to form a melt. Then, the seed crystal attached to the seed chuck is immersed in the melt, and the seed chuck is pulled up while rotating the seed chuck and the graphite crucible in the same direction or in the opposite direction to grow single crystal silicon.

As a means for improving the productivity of semiconductor single crystals by the CZ method, a recharge method in which a step of pulling single crystal silicon from a melt, then recharging and melting a raw material polycrystal, and pulling the single crystal silicon is repeated. There is. Further, when pulling a large-diameter and long single-crystal silicon, after the completion of melting of the initial raw material, it is possible to use an additional charge method in which a raw material polycrystal is added to the melt before the single crystal pulling is started to increase the melt. is there. The single crystal manufacturing apparatus disclosed in Japanese Unexamined Patent Publication No. 7-187881 uses rod-shaped polycrystalline silicon as a raw material for recharging or additional charging, and is provided with an outward annular rim at the upper end and a crucible at the lower end. Located in the vicinity of the melt filling area inside, a cylindrical screen arranged around the single crystal pulling zone, and inside the screen, the single crystal pulling zone was surrounded and opened close to the opening of this screen. A sub-heater for melting the material is provided. Alternatively, the lower part of the cylindrical screen has a heating element structure, and a screen integrated with the sub-heater is provided. The sub-heater can dissolve rod-shaped polycrystalline silicon used for recharging or additional charging without causing liquid splash, and granular polycrystalline silicon can also be easily dissolved.

[0004]

In the production of a semiconductor single crystal by the CZ method, the bulk raw material charged in a quartz crucible must first be melted to form a melt prior to pulling the semiconductor single crystal. The crucible receives the highest heat load when the raw materials are melted. When the quartz crucible is subjected to an excessive heat load, the quartz crucible is deformed to deteriorate the roundness, or the bubbles contained in the quartz crucible expand to impair the uniformity of the wall thickness. For this reason, the position of the melt surface with respect to the quartz crucible changes, and the position of the quartz crucible at the start of pulling the single crystal between batches shifts, which causes fluctuation in quality.

In addition to the above, deterioration of the quartz crucible is cited as the biggest problem. When the heat load applied to the quartz crucible is large, the transparent layer on the inner surface of the quartz crucible is melted and the layer containing bubbles is exposed to the melt. When the bubbles burst in this state, the extremely small pieces are mixed in the melt and easily adhere to the single crystal to cause dislocation.

In recent years, large-diameter wafers exceeding 6 inches have become mainstream, and single crystal silicon having a diameter of 6 inches or more is required. For this reason, the semiconductor single crystal manufacturing apparatus becomes large in size, and particularly when pulling a large diameter single crystal having a diameter of 8 inches or more, the operation time per batch becomes long, which causes deterioration of the quartz crucible in the latter half of the straight body part growing process. There is a high possibility that dislocations will result. As a means for preventing the deterioration of the quartz crucible, there is a method of reducing the heat load applied to the quartz crucible by lowering the electric power supplied to the heater, but it is not preferable because the raw material melting time becomes long and the productivity is lowered.

As one of the means for efficiently producing large-diameter single crystal silicon by the CZ method, continuous pulling of the single crystal silicon while continuously supplying the raw material into the crucible according to the amount of the grown single crystal silicon. The charge method is used. FIG. 3 is a partial cross-sectional view showing an example of a semiconductor single crystal manufacturing apparatus by the continuous charge method, in which a plurality of raw material supply devices 20 are installed above the edge of the quartz crucible 1. The raw material supply device 20 melts rod-shaped polycrystalline silicon (hereinafter referred to as polycrystalline rod) 23 suspended from above the main chamber 9 and drops it into the melt 10. The rod melting heater 21 and the rod. A protective cylinder 24 surrounding the melting heater 21 and a raw material supply pipe 25 attached to the bottom of the protective cylinder 24 are provided. An annular melt cover 22 is attached to the lower portion of the protective cylinder 24 and serves as a passage for discharging the inert gas introduced into the raw material supply device 20 from the main chamber 9. An exhaust pipe is attached to the outer edge of the melt cover 22. 26 is connected.

The quartz crucible 1 used in the semiconductor single crystal manufacturing apparatus by the continuous charge method has a zone for continuously supplying the raw material at the edge thereof, so that it is better than the quartz crucible used in the ordinary CZ method. It has a large inner diameter and a shallow depth. Therefore, the distance from the main heater 2 to the center of the quartz crucible 1 becomes long, and the quartz crucible 1
It is difficult for heat to be transferred to the vicinity of the center of the crucible when melting the massive raw material charged in Therefore, in order to avoid deterioration of the quartz crucible 1, the melting time becomes longer than that in the case of using a normal quartz crucible.

The present invention has been made by paying attention to the above-mentioned conventional problems, and in the production of a semiconductor single crystal by the CZ method, the heat load applied to the quartz crucible is reduced and the single crystal resulting from the deterioration of the quartz crucible is formed. It is an object of the present invention to provide a method for producing a semiconductor single crystal that prevents dislocation formation and that can efficiently dissolve a bulk material loaded in a quartz crucible.

[0010]

In order to achieve the above object, a method for producing a semiconductor single crystal according to the present invention is a method for producing a semiconductor single crystal by the CZ method, in which a crucible is melted when a bulk raw material loaded in the crucible is melted. The lumped raw material is heated by the surrounding annular main heater and the heating means installed above the crucible, and the electric power supplied to the main heater is lowered to a predetermined value.

Further, in the production of a semiconductor single crystal by a continuous charge method for producing a semiconductor single crystal while supplying a raw material, a heating means installed above the crucible is used for heating or melting the supply raw material in the crucible. The bulk material was heated and the electric power supplied to the main heater was lowered to a predetermined value.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention prevents the quartz crucible from being overheated when the bulk raw material charged in the quartz crucible is melted in the initial stage of the semiconductor single crystal production by the CZ method. Is the way to do it. That is, C
In the production of a semiconductor single crystal by the Z method, the bulk material is heated by the heating means and the main heater installed above the crucible. At this time, by reducing the electric power supplied to the main heater to a predetermined value, the heat load applied to the quartz crucible is reduced, the deterioration due to heat is suppressed, and dislocation of the semiconductor single crystal is prevented. Further, by using the main heater and the heating means in combination, the time required for melting the massive raw material does not become long even if the power supplied to the main heater is lowered, and the massive raw material can be efficiently melted.

In the production of a semiconductor single crystal by the continuous charge method, the bulk heater in the crucible is heated by using the main heater 2 and the rod melting heater 21 shown in FIG. 3, so that the semiconductor single crystal by the CZ method is used. The power supplied to the main heater can be reduced in the same manner as in the manufacturing of, and the heat load applied to the quartz crucible is reduced.

Next, an embodiment of the method for producing a semiconductor single crystal according to the present invention will be described with reference to the drawings. FIG. 1 is a partial cross-sectional view showing, as a first embodiment of the present invention, a step of melting a bulk material loaded in a quartz crucible in the production of a semiconductor single crystal by a continuous charge method. This semiconductor single crystal manufacturing apparatus is an apparatus for pulling up a semiconductor single crystal while melting a polycrystalline rod suspended from above a main chamber and continuously supplying its droplets to a melt, and an edge portion of a quartz crucible 1. Two sets of raw material supply devices 20 are installed above, and a rod melting heater 21 is incorporated in the raw material supply device 20. The main heater 2 is provided below the raw material supply device 20.
The melt cover 2 attached to the upper end of the heat insulating cylinder 3 surrounding the
2 fixed. The melt cover 22 forms a discharge path for the inert gas introduced into the raw material supply device 20.

A quartz crucible 1 housed in a graphite crucible 4 is loaded with a predetermined amount of massive raw material 5 made of polycrystalline silicon. At this time, in order to avoid interference between the lower end of the raw material supply device 20 and the massive raw material 5, the crucible shaft 6 is driven to lower the graphite crucible 4 and the quartz crucible 1 to predetermined positions.

When melting the bulk material 5, the main heater 2
And electric power is supplied to both of the rod melting heaters 21 incorporated in the raw material supply device 20. In this case, the polycrystalline rod is not suspended in the rod melting heater 21. The lump raw material 5 is heated by the main heater 2 and the rod melting heater 21. The electric power supplied to the main heater 2 is set lower than when the bulk raw material is melted by the conventional method using only the main heater.

As an example, when it took 8 hours to melt the bulk raw material by the conventional method, it was possible to melt it in 6 hours by using the main heater and the rod melting heater together.
If the bulk material is melted by the main heater in 6 hours without heating by the rod melting heater, the electric power supplied to the main heater must be increased by 15 kW, which causes deterioration of the quartz crucible.

As a second embodiment of the present invention, FIG. 2 is a partial cross-sectional view showing a case where a bulk raw material in a quartz crucible is melted by using a semiconductor single crystal manufacturing apparatus having a heating device above the crucible. The same components as those in FIG. 1 are designated by the same reference numerals as those in FIG. Similarly to the first embodiment, in the case of the second embodiment, the graphite crucible 7 and the quartz crucible 8 are lowered to avoid the interference between the lower end of the heating device 30 and the massive raw material 5, and the main heater 2 and the heating device 30 are connected. Activate. The heating device 30 may be a plurality of heaters that are independent of each other, and may have an annular shape.
Individual heaters may be used. The electric power supplied to the main heater 2 is set lower than when the bulk raw material is melted by the conventional method.

In the case of a semiconductor single crystal manufacturing apparatus having a heating means above the crucible, the bulk raw material can be melted without deterioration of the quartz crucible by using the main heater and the heating means together when melting the bulk raw material loaded in the quartz crucible. Can be dissolved in a short time.

[0020]

As described above, according to the present invention, C
In the initial step of manufacturing a semiconductor single crystal by the Z method or the CZ method in which continuous charging is performed, the heating means installed above the crucible is used together with the main heater when melting the bulk raw material loaded in the quartz crucible. Even if the electric power supplied to the main heater is lowered, the melting time does not become long, and the bulk material can be efficiently melted. Further, since the heat load applied to the quartz crucible by the main heater is reduced, deterioration of the quartz crucible due to the heat load, which has been a problem in the past, can be suppressed, and dislocation of the semiconductor single crystal can be prevented.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing, as a first embodiment of the present invention, a step of melting a bulk material in the production of a semiconductor single crystal by a continuous charge method.

FIG. 2 is a partial cross-sectional view showing a case where a bulk raw material is melted using a semiconductor single crystal manufacturing apparatus having a heating device above a crucible as a second embodiment of the present invention.

FIG. 3 is a partial cross-sectional view showing an example of a conventional semiconductor single crystal manufacturing apparatus by a continuous charge method.

[Explanation of symbols]

 1,8 Quartz crucible 2 Main heater 4,7 Graphite crucible 5 Bulk material 20 Raw material supply device 21 Rod melting heater 30 Heating device

Claims (2)

[Claims] 1. In the production of a semiconductor single crystal by the Czochralski method, when melting a lumped raw material loaded in a crucible, the lumped raw material is heated by an annular main heater surrounding the crucible and a heating means installed above the crucible. A method for manufacturing a semiconductor single crystal, which comprises heating and reducing the electric power supplied to the main heater to a predetermined value. 2. In the production of a semiconductor single crystal by a continuous charge method for producing a semiconductor single crystal while supplying a raw material,
Heating the bulk material in the crucible using a heating means installed above the crucible to heat or melt the feedstock;
A method for manufacturing a semiconductor single crystal, characterized in that the electric power supplied to the main heater is lowered to a predetermined value.