JPH08104590A - Method for growing silicon single crystal - Google Patents

Abstract

PURPOSE: To grow a silicon single crystal free from disturbance in the crystal with one time of an FZ stage while preventing the polycrystallization and disturbance of the single crystal occurring in the polycrystal grains peeled from a raw material rod. CONSTITUTION: This method for growing the silicon single crystal by the FZ method comprises growing the silicon single crystal 3 by heating and melting the silicon raw material rod 1 by an induction heating coil 2 installed in a growth furnace 5. This induction heating coil 2 is provided with annular members 10 on the front surface side and/or lower surface side thereof. The inner peripheral edge 1a of the annular members 10 is inserted into a melting zone 4 where the silicon raw material rod 1 is melted. The silicon single crystal is grown by one time of the FZ stage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a silicon single crystal. More specifically, by the FZ method (float zone method or floating zone melting method), 1
The present invention relates to a method for growing a silicon single crystal in a single process.

[0002]

BACKGROUND OF THE INVENTION FZ method and CZ method (Czochralski method) are mainly used as a method for growing a silicon single crystal. The FZ method is a high-purity silicon which is less contaminated by impurities than the CZ method. It has a feature that a single crystal can be grown, and is advantageous when, for example, a high-resistance silicon single crystal is used for producing a high-power semiconductor element.

FIG. 3 is a schematic cross-sectional view showing the overall structure of a silicon single crystal growth apparatus that has been conventionally used when growing a silicon single crystal by the FZ method. Inside the growth furnace 5, a silicon polycrystalline raw material rod 1 having a predetermined diameter held by an upper shaft 8 and a seed crystal 6 held by a lower shaft 7 are housed. The raw material rod 1 is surrounded by a ring-shaped high-frequency induction heating coil (hereinafter referred to as “induction heating coil”) 2 for partially heating and melting the lower end of the raw material rod 1. It is arranged coaxially with.

When a silicon single crystal is grown using this apparatus, first, the seed crystal 6 held by the lower shaft 7 is brought into contact with the lower end of the raw material rod 1 held by the upper shaft 8 and the vicinity of the contact portion between the two. The raw material rod 1 and the seed crystal 6 are moved so that is on the same surface (heating surface) as the induction heating coil 2. Then, the lower end of the raw material rod 1 is melted by the induction heating coil 2, the seed crystal 6 is fused to the melting zone, and then the raw material rod 1 and the seed crystal 6 are integrated while dislocation-free by a seed drawing.

Next, the raw material rod 1 and the seed crystal 6 are lowered at a slow speed while rotating, and the heating surface of the induction heating coil 2 is relatively moved from the lower end to the upper end of the raw material rod 1. At this time, the region on the heating surface of the induction heating coil 2 of the raw material rod 1 is melted and the melting zone 4 is formed. The melting zone 4 gradually cools while emitting radiant heat as it passes over the heating surface, and becomes a single crystal according to the crystal orientation of the seed crystal. Then, the melting zone 4 moves from the lower end to the upper end of the raw material rod 1 to obtain the single crystal rod 3.

Conventionally, when the silicon single crystal 3 is grown by the FZ method, the step of heating and melting the raw material rod 1 by the induction heating coil 2 to move the melting zone 4 from the lower end to the upper end of the raw material rod 1 (FZ step). Was normally performed twice to obtain a silicon single crystal 3. This is because it is difficult for the raw material rod 1 to be completely made into a single crystal in one FZ process, and the obtained single crystal may be disturbed. It is considered that this cause is caused by the polycrystalline grains separated from the raw material rod 1.

That is, as shown in FIG. 4, the polycrystal grains 9 are separated from the solid-liquid interface 1a on the raw material rod 1 side, and are moved downward by convection in the melting zone 4, so that the polycrystal grains 9 cannot be completely melted. As soon as it reaches the solid-liquid interface 3a on the single crystal rod 3 side, the growing single crystal is polycrystallized. For this reason,
After growing the intermediate silicon polycrystalline rod in the first FZ step (prezoning) to make it difficult for the polycrystalline grains 9 to peel off,
In the second FZ step (dislocation free zoning), the silicon single crystal 3 was grown using the intermediate silicon polycrystal rod as a raw material rod.

[0008]

However, the FZ process is one
Since it takes a considerable amount of time to perform the process once, performing the FZ process twice is disadvantageous in terms of production efficiency in manufacturing a silicon single crystal. Therefore, the present invention prevents the single crystal from being polycrystallized or disturbed by the polycrystal grains separated from the raw material rod.
It is an object of the present invention to provide a silicon single crystal growth method capable of growing a silicon single crystal without crystal disorder in the Z step.

[0009]

In order to achieve the above technical object, the present invention uses the FZ method to grow a silicon single crystal by heating and melting a silicon raw material rod by an induction heating coil provided in a growth furnace. In the single crystal growth method, a ring-shaped member is provided on the upper surface side and / or the lower surface side of the induction heating coil, the inner peripheral edge of the ring-shaped member is inserted into the melting zone where the silicon raw material rod is melted, and the FZ is performed once The silicon single crystal was grown in the process.

The ring-shaped member is preferably made of quartz, sapphire or silicon nitride. It is also preferable to apply a static magnetic field to the melting zone.

[0011]

In the present invention, since the specific gravity of the polycrystalline grains 9 is about 10% smaller than that of the molten silicon (melting zone 4), the melting zone 4
The property of being easily floated on the surface of is used.

As shown in FIG. 2, a ring-shaped member 10 is provided on the upper surface side and / or the lower surface side of an induction heating coil 2 for heating and melting the silicon raw material rod 1, and the inner peripheral edge of the ring-shaped member 10 is made of the silicon raw material. When the rod 1 is inserted into the molten zone 4 melted, the polycrystalline grains 9 floating on the surface of the molten zone 4 and moving downward on the surface of the molten zone 4 are received by the ring-shaped member 10, so that The crystal grains 9 are suppressed from directly adhering to the growth interface 3a.

The ring-shaped member 10 is preferably made of quartz, sapphire or silicon nitride. In particular, when it is made of synthetic quartz, the risk of contamination from the ring-shaped member 10 can be further reduced.

The polycrystalline grains 9 received by the ring-shaped member 10 stay near the ring-shaped member 10 and either melt or enter the melting zone 4. The polycrystalline grains 9 that have entered the melting zone 4 move along with convection, but when a static magnetic field is applied to the melting zone 4, convection of molten silicon in the melting zone 4 can be suppressed, so that polycrystalline It is possible to lengthen the time required for the grains 9 to reach the growth interface 3a on the single crystal 3 side to completely melt the polycrystal grains, and further suppress polycrystallization and crystal disorder at the single crystal growth site.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be exemplarily described below with reference to the drawings. However, the dimensions, materials, shapes, relative positions, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto only unless otherwise specified, and are simply described. It's just an example.

FIG. 1 is a schematic view showing an embodiment of the silicon single crystal growth method of the present invention. The basic structure is the same as the conventional growth method shown in FIG. 3, but the method of this embodiment is
A ring-shaped member 10 made of synthetic quartz is provided on the lower surface side of the induction heating coil 2. An inner peripheral edge 10a of the ring-shaped member 10 is inserted into a melting zone where the silicon raw material rod is melted.

FIG. 2 is a partially enlarged view including the ring-shaped member 10. As shown in the figure, among the polycrystalline grains 9 separated from the solid-liquid interface 1a on the raw material rod 1 side, the polycrystalline grains 9 floating on the surface of the melting zone 4 move downward on the surface of the melting zone 4 due to gravity. Is prevented from moving by the ring-shaped member 10 and remains near the ring-shaped member 10 to melt or enter the melting zone 4. The polycrystalline grains 9 that have entered the melting zone 4 are
Melting while moving by convection.

When a silicon single crystal is grown in one FZ step using the conventional growth method, the single crystallization rate is 30.
%, And crystal disorder was generated, but when a silicon single crystal was grown in one FZ step using the growth method of this example, the single crystallization rate was 90% or more, and crystal disorder was observed. Could not be seen.

Although the ring-shaped member is installed on the lower surface side of the induction heating coil in this embodiment, the ring-shaped member may be installed on the upper surface side of the induction heating coil.

In the melting zone 4, 300-1000 gau
When a static magnetic field of ss is applied, the convection of molten silicon in the melting zone 4 is suppressed, so that the polycrystalline grains 9 riding on the convection are completely melted by the time they reach the growth interface 3a on the single crystal 3 side. It is possible to further suppress polycrystallization of the single crystal growth site and crystal disorder.

[0021]

As described above, according to the present invention, a silicon single crystal without crystal disorder can be grown from a silicon raw material rod by one FZ step, and a high-quality silicon single crystal with high productivity can be obtained. Crystals can be produced.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a silicon single crystal growth method of the present invention.

FIG. 2 is a partially enlarged view of the vicinity of a melting zone in FIG.

FIG. 3 is a schematic cross-sectional view showing an example of a conventional silicon single crystal growth method.

4 is a partially enlarged view of the vicinity of the melting zone in FIG.

[Description of sign]

 1 Raw material rod 1a Solid-liquid interface 2 Induction heating coil 3 Single crystal rod 3a Growth interface 4 Melting zone 5 Growth furnace 6 Seed crystal 7 Lower axis 8 Upper axis 9 Polycrystalline grain 10 Ring-shaped member

Claims (3)

[Claims] 1. A method for growing a silicon single crystal by an FZ method in which a silicon raw material rod is heated and melted by an induction heating coil provided in a growth furnace to grow a silicon single crystal, the upper surface side and / or the lower surface of the induction heating coil. A silicon single crystal growth characterized in that a ring-shaped member is provided on the side, the inner peripheral edge of the ring-shaped member is inserted into the melting zone where the silicon raw material rod is melted, and a silicon single crystal is grown in one FZ step. Method. 2. The method for growing a silicon single crystal according to claim 1, wherein the ring-shaped member is made of quartz, sapphire or silicon nitride. 3. The method for growing a silicon single crystal according to claim 1, wherein a static magnetic field is applied to the melting zone.