JP2000327490A - Method and apparatus for producing silicon crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a silicon crystal by which a long belt-like silicon crystal being set in an optional form and having low impurity content and excellent crystallinity is continuously and stably grown. SOLUTION: The method for producing a silicon crystal is constituted of a process of first melting silicon in a crucible 14 wherein a couple of fine tubes 16a, 16b each having a through hole are erected at a desired distance and then forming a meniscus 22 between the fine tubes by raising molten liquid 20 to the upper end of each fine tube by using the capillarity of each fine tube, and a process of bringing a ribbon-like silicon seed crystal 19 into contact with the meniscus 22 and gradually pulling up the seed crystal to grow the belt-like silicon crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a silicon crystal and an apparatus for manufacturing the same, and more particularly, to a method for manufacturing a strip-shaped polycrystalline silicon and an apparatus for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, methods for producing a silicon crystal having a predetermined thickness include, for example, a dendrite method disclosed in Japanese Patent No. 2551441, and an EFG (Edge-defined Film-fed Growth) disclosed in Japanese Patent No. 1230908. ) Method is known. In the dendrite method, it is necessary to strictly control the temperature of the melt in order to maintain the dendrite shape, and it is difficult to control the thickness and width of the crystal. Also, EF
In the G method, as shown in FIG. 7, a polycrystalline silicon is melted in a quartz crucible 1 to form a melt 2, and a die made of a material that is hardly reacted with the melt and hardly deformed by the melt. After the seed crystal 3 is provided, the seed crystal 4 is applied to the melt 2 in the die 3 and the seed crystal 4 is gradually pulled up at a desired speed to grow a plate-like crystal 5 having a constant width and thickness. It is a way to make it.

[0003]

However, in the above-mentioned EFG method, the die 3 and the melt 2 come into contact with each other over a wide area in the width direction of the die 3 as shown in FIG. Therefore, the amount of impurities mixed into the die 3 increases. The incorporation of impurities causes the generation of defects in the grown crystal, and has a great effect on carrier movement and the like.

The present invention provides a method of manufacturing a silicon crystal capable of continuously and stably growing a long strip-shaped silicon crystal having excellent crystallinity with a small amount of impurities set in an arbitrary shape. And an apparatus for manufacturing the same.

[0005]

According to a method of manufacturing a silicon crystal according to the present invention, silicon is melted in a crucible in which a pair of thin tubes having through holes are erected at a desired distance.
A step of forming a meniscus between the capillaries by causing a melt to spring up to the capillaries using capillary action of the capillaries, and bringing a ribbon-shaped silicon seed crystal into contact with the meniscus; And a step of growing the band-shaped silicon crystal by gradually pulling up the silicon crystal.

Here, the thin tube means a cylinder having a circular or elliptical cross section, or a polygon having a cross section of square, rectangle, pentagon, hexagon, or the like.

According to the present invention, the melt of silicon generated in the crucible is sprinkled at the upper ends of the crucibles by utilizing the capillary phenomenon of a pair of thin tubes erected in the crucible, thereby forming the capillary. By forming a meniscus in between, the ribbon-like seed crystal is brought into contact with the melt in a state where the liquid level of the melt is kept constant, and the width and thickness constrained by the pair of thin tubes and the seed crystal are raised by pulling. The band-shaped silicon crystal can be stably grown. At this time, the thickness of the band-shaped silicon crystal can be more precisely adjusted by controlling the melt temperature and the pulling speed.

Further, since the contact area of the thin tube with the melt can be made smaller than that of the die used in the conventional EFG method, the amount of impurities mixed into the silicon crystal grown from the thin tube can be remarkably reduced. As a result, a band-shaped silicon crystal having excellent crystallinity can be grown.

An apparatus for manufacturing a silicon crystal according to the present invention comprises: a crucible containing a silicon melt; heating means for heating and melting the silicon contained in the crucible; A pair of thin tubes having through holes erected at a desired distance, and a ribbon-shaped silicon seed crystal that is brought into contact with the melt between the thin tubes and that is gradually pulled up by pulling means. Is what you do.

According to the present invention, it is possible to stably grow a band-shaped silicon crystal having a width regulated by the interval between the pair of thin tubes, and to significantly reduce the amount of impurities mixed into the silicon crystal to improve the crystallinity. The manufacturing apparatus of the silicon crystal which can grow the band-shaped silicon crystal excellent in this can be provided.

In the silicon crystal manufacturing apparatus according to the present invention, each of the thin tubes preferably has an upper end inclined at an angle of 60 ° or less with respect to a vertical direction.

If a pair of thin tubes having such a structure is used,
The silicon melt that has been pumped up from the upper end of these capillaries by capillary action can flow downward without stopping at the upper end in relation to the contact angle at the inclined tip end, so a thin-walled strip formed by pulling up with a seed crystal Silicon crystals can be grown. In other words, if the tip of the thin tube is flat, the silicon melt that has been pumped up by the capillary phenomenon stops at the tip due to the contact angle between the thin tube and the melt. Is limited by the diameter of the upper end of the thin tube, and it is difficult to make the thinner than that. On the other hand, the upper ends of the pair of thin tubes are set to 6
By making the shape inclined at an angle of 0 ° or less,
Due to the contact angle with the melt, the silicon melt that has been sprinkled from the upper end of the capillary by capillary action can flow downward without stopping at the upper end. By pulling up, a thin band-shaped silicon crystal can be grown.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an apparatus for manufacturing a silicon crystal according to the present invention will be described in detail with reference to FIGS.

FIG. 1 is a sectional view showing a silicon crystal manufacturing apparatus according to the present invention, and FIG. 2 is a plan view of FIG. For example, a bottomed cylindrical heat insulating container 11 made of a sponge-like carbon refractory is housed in a chamber (not shown) in which vacuum evacuation and gas replacement are performed. High frequency induction heating coil 1
2 is attached to the inside of the chamber (not shown) outside the heat insulating container 11. A heating element 13 made of, for example, carbon having a round-bottom concave portion is fitted into the heat insulating container 11. The high-frequency induction heating coil 12 and the heating element 13 constitute a heating means for heating and melting the raw granular silicon in the crucible described later. Note that the heating means is not limited to the case where these members are used, and a resistance heating method may be adopted.

A crucible 14 made of, for example, quartz for holding the raw granular silicon is fitted into the heating element 13. For example, a pair of cylindrical support members 15a made of quartz,
15b is welded to the inner surface of the bottom of the crucible 14 at a desired interval. For example, a pair of cylindrical thin tubes 16a and 16b made of carbon are used as the support members 15a and 15b.
b. In addition, a through-hole (not shown) is formed in the vicinity of the middle between the small tubes 16a and 16b. A lid 18 made of, for example, carbon and having a rectangular slit 17 opened at a position corresponding to the thin tubes 16a and 16b is provided with the heating element 13 and the crucible 14.
It is installed at the upper end of. This lid 18 is used to control the temperature gradient of the melt. Reference numeral 19 denotes a ribbon-shaped silicon seed crystal (silicon single crystal) pulled up by a pulling device (not shown).

The diameter of the thin tubes 16a, 16b is 3-6.
mm and a thickness of 1-2 mm.

Next, a method of growing a band-shaped silicon crystal (silicon polycrystal) using the above-described manufacturing apparatus will be described.

First, a predetermined amount of raw material granular silicon is charged into the crucible 14. The gas in the chamber (not shown) is evacuated, and for example, an argon gas is introduced into the chamber through a gas introduction pipe attached to the chamber to make an argon atmosphere. The raw material granular silicon is melted by applying high frequency from the high frequency induction heating coil 12 to the heating element 13 to generate heat. The silicon melt 20 in the crucible 14 flows into the inside of the pair of carbon thin tubes 16a and 16b through the not-shown through holes of the pair of carbon thin tubes 16a and 16b, springs up by capillary action, and springs up at the upper ends of the thin tubes 16a and 16b. 21
a, 21b and a pair of thin tubes 16a, 1b.
A meniscus 22 is formed between 6b. In this state, the ribbon-shaped silicon seed crystal 19 is lowered between the thin tubes 16a and 16b by a pulling device (not shown) and brought into contact with the meniscus 22. Subsequently, a belt-like silicon crystal is grown by pulling the seed crystal 19 at a predetermined speed by a pulling device. At this time, the melt 20 to be a silicon crystal is restrained by the pair of carbon thin tubes 16a and 16b wetted by the seed crystal 19 and the silicon melt, so that the width and the thickness are reduced without strict temperature control. A controlled band-shaped silicon crystal can be grown.

When the growth of the band-shaped silicon crystal is continued, the liquid level of the silicon melt 20 is lowered. However, the meniscus 22 to which the seed crystal 19 comes in contact is melted by the capillary action of the carbon thin tubes 16a and 16b. Is supplied, the band-shaped silicon crystal can be grown even when the liquid level of the melt 20 is lowered.

Further, in the process of growing the band-shaped silicon crystal, the thin tube can have a smaller contact area with the melt than the die used in the conventional EFG method.
The amount of impurities mixed into the growing silicon crystal from b can be significantly reduced. As a result, a band-shaped silicon crystal having excellent crystallinity can be grown.

Therefore, it is possible to continuously and stably grow a long strip-shaped silicon crystal having excellent crystallinity with a small amount of impurities set in an arbitrary shape.

The apparatus for manufacturing a silicon crystal according to the present invention is not limited to the structure shown in FIGS. 1 and 2 but may have the structure shown in FIGS. 3 to 6 described below. However, members similar to those in FIGS. 1 and 2 described above are denoted by the same reference numerals, and description thereof is omitted.

The apparatus for manufacturing a silicon crystal shown in FIGS. 3 and 4 has a cylindrical thin tube 16a, 16 made of a pair of carbon.
6b has upper end portions 23a and 23b inclined at an angle (θ) of 60 ° or less with respect to the vertical direction.

According to such a configuration, the pair of thin tubes 16
By forming the upper ends 23a, 23b of the a, 16b at an angle of not more than 60 ° with respect to the vertical direction, the thin tubes 16a, 16b can be formed in consideration of the contact angle with the melt 20.
Since the silicon melt 20 sprinkled by the capillary action from the upper end can flow downward without stopping at the upper end,
Without being restricted by the diameter of the upper end of the thin tubes 16a, 16b,
By pulling up with the silicon seed crystal 19, a strip-shaped silicon crystal having a small thickness can be grown. Here, when the inclination angle (θ) of the upper ends 23a and 23b exceeds 60 °,
Since the upper end is easily wetted with the melt 20 and the melt is easily stopped at the upper ends of the thin tubes 16a and 16b, it becomes difficult to grow a band-like silicon crystal thinner than the thin tube diameter.

Therefore, it is possible to continuously and stably grow a long strip-shaped silicon crystal having excellent crystallinity with a small amount of impurities set in an arbitrary shape and having a smaller thickness. .

The apparatus for manufacturing a silicon crystal shown in FIG. 5 includes a crucible 1 having cylindrical support members 24a and 24b each having a square cross section.
4 is welded to the inner surface at the bottom of the
a, 25b are respectively inserted into the support members 24a, 24b to be erected, and the carbon thin tubes 25a, 25b are formed in a tubular shape having a square cross section, and are 60 ° with respect to the vertical direction.
It has upper end portions 26a and 26b inclined at the following angles.

According to such a configuration, FIG.
Similar to the manufacturing apparatus of FIG. 4, a long band-shaped silicon crystal having excellent crystallinity with a small amount of impurities set in an arbitrary shape and having a smaller thickness is continuously and stably grown. be able to.

In the apparatus for manufacturing a silicon crystal shown in FIG. 6, cylindrical supporting members 27a and 27b extending in the thickness direction of the seed crystal are welded to the inner surface of the bottom of the crucible 14,
The pair of carbon thin tubes 28a, 28b
The carbon thin tubes 28a, 28b are vertically inserted into the tubes 7a, 27b, respectively, and have a rectangular cross section and have upper ends 29a, 29b inclined at an angle of 60 ° or less with respect to the vertical direction. .

According to such a configuration, FIG.
Similar to the manufacturing apparatus of FIG. 4, a long band-shaped silicon crystal having excellent crystallinity with a small amount of impurities set in an arbitrary shape and having a smaller thickness is continuously and stably grown. be able to.

The tubular thin tubes 28a and 28b each having a rectangular cross section that is long in the thickness direction of the band-shaped silicon crystal to be grown.
The positioning between the thin tubes 28a and 28b when inserting a seed crystal during the production of a crystal is facilitated.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail.

Using the silicon crystal manufacturing apparatus shown in FIGS. 1 and 2 described above, a band-shaped silicon polycrystal was grown under the following conditions.

<Manufacturing conditions>Crucible; 80 mm diameter, carbon thin tube; cylindrical body with outer diameter of 5 to 6 mm, inner diameter of 1 to 2 mm; distance of carbon thin tube; 40 to 50 mm; melt; silicon melt (around the melting point) Temperature), seed crystal; ribbon-like single-crystal silicon having a width of 40 to 50 mm and a thickness of 625 μm, and a seed crystal pulling rate of 2 to 3 mm / min.

The grown crystal was confirmed to be polycrystalline by powder X-ray diffraction. The amount of carbon in the grown crystal was measured by a charged particle activation analysis (RAA). As a result, it was confirmed that the amount of carbon was as small as 1 ppm or less.

[0035]

As described above in detail, according to the method and the apparatus for manufacturing a silicon single crystal according to the present invention, a long strip having excellent crystallinity with a small amount of impurities set in an arbitrary shape is provided. Silicon crystals can be grown continuously and stably, and have remarkable effects such as effective use for photoelectric conversion members of solar cells.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a silicon crystal manufacturing apparatus according to the present invention.

FIG. 2 is a plan view of the manufacturing apparatus of FIG.

FIG. 3 is a sectional view showing another apparatus for manufacturing a silicon crystal according to the present invention.

FIG. 4 is an enlarged sectional view of a main part of the manufacturing apparatus of FIG. 3;

FIG. 5 is an enlarged plan view of a main part showing still another apparatus for manufacturing a silicon crystal according to the present invention.

FIG. 6 is an enlarged plan view of a main part showing still another apparatus for manufacturing a silicon crystal according to the present invention.

FIG. 7 is a sectional view showing a conventional silicon crystal manufacturing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Heat insulation container, 12 ... High frequency induction heating coil, 13 ... Heating element, 14 ... Crucible, 16a, 16b, 25a, 25b, 28a, 28b ... Capillary tube, 19 ... Seed crystal, 20 ... Silicon melt, 21a, 21b ... Bump, 22 ... meniscus, 23a, 23b, 26a, 26b, 29a, 29b ... inclined upper end.

Claims (3)

[Claims] 1. A pair of thin tubes having through-holes melt silicon in a crucible that is erected at a desired distance, and a melt is sprinkled at the upper ends of the thin tubes by utilizing the capillary phenomenon of each of the thin tubes. Forming a meniscus between the thin tubes, and bringing a ribbon-shaped silicon seed crystal into contact with the meniscus, and gradually raising the seed crystal to grow a band-shaped silicon crystal. Manufacturing method of silicon crystal. 2. A crucible in which a melt of silicon is stored, heating means for heating and melting the silicon stored in the crucible, and standing on the inner surface of the crucible at a desired distance from each other. And a ribbon-shaped silicon seed crystal which is brought into contact with the melt between the thin tubes and is gradually pulled up by a pulling means. 3. Each of the thin tubes is 60 ° with respect to a vertical direction.
3. The silicon crystal manufacturing apparatus according to claim 2, wherein the apparatus has an upper end inclined at the following angle.