JP4569957B2 - Crucible for producing polycrystalline semiconductor and method for producing polycrystalline semiconductor - Google Patents

Description

  The present invention relates to a crucible for producing a polycrystalline semiconductor and a method for producing a polycrystalline semiconductor, which can suitably produce a polycrystalline semiconductor having a crystal orientation close to that of a single crystal.

Silicon is widely used as a material for semiconductors used in integrated circuits and the like, and as a material for solar cells. This silicon is an excellent material from the viewpoint of industrial production and resources, and most of the silicon that has been put into practical use as a solar cell material is silicon.
Currently, solar cells using single crystal silicon are the mainstream as power supply solar cells, but high-quality polycrystalline silicon solar cells are required to realize inexpensive solar cells.

As a method for producing this polycrystalline silicon, for example, in Japanese Patent Application Laid-Open No. 9-71497, a single crystal of silicon is arranged as a seed crystal at a cone-shaped bottom portion, and a crucible bottom portion in the vicinity thereof is cooled to thereby form a solid material. A method of obtaining high-quality polycrystalline silicon without melting the seed crystal when silicon is melted is disclosed.
Japanese Patent Laid-Open No. 10-7493 discloses that a single crystal silicon is placed as a seed crystal on the inner bottom surface of a flat crucible without gaps, and the temperature at the bottom of the crucible is precisely controlled to prevent melting of the seed crystal. A method for obtaining high-quality polycrystalline silicon with uniform orientation is disclosed.

JP-A-9-71497 Japanese Patent Laid-Open No. 10-7493

By the way, in the proposed manufacturing method, since the seed crystal arranged at the bottom of the crucible is silicon of the same material as the semiconductor material, it is necessary to always keep the seed crystal below the melting point. It was necessary to cool the bottom of the crucible.
That is, in the proposed manufacturing method, there is a problem that a part of the semiconductor material is cooled while being heated and melted, and the energy efficiency is remarkably lowered.

In addition, since the interface between the semiconductor material and the seed crystal in the crucible melts during the melting of the semiconductor material, the seed crystal needs to have a thickness of 20 mm or more, which increases the manufacturing cost and increases the manufacturing cost of solar cells and the like. There was a problem.
Furthermore, since the single crystal of silicon is lower in density than the silicon melt, it is difficult to place it on the bottom of the crucible as it is, and there is a problem that some fixing means must be taken and the crucible manufacturing cost increases. was there.

  The present invention has been made in order to solve the above-mentioned problems, and is capable of producing a polycrystalline semiconductor that can produce a polycrystalline semiconductor that has good energy efficiency, low cost, and uniform crystal orientation close to that of a single crystal. An object of the present invention is to provide a crucible for use and a method for producing a polycrystalline semiconductor.

The present invention has been made to achieve the above object, and a crucible for manufacturing a polycrystalline semiconductor according to the present invention has a seed crystal disposed on the inner bottom surface of the crucible, and a semiconductor material is inserted into the crucible. In an active atmosphere, for melting a semiconductor material in a crucible by a heating means, and removing the heat from the bottom where the seed crystal is disposed, and gradually solidifying the molten semiconductor material for manufacturing a polycrystalline semiconductor In the crucible, a plurality of grooves are formed on the bottom surface in the crucible with a predetermined interval, or a plurality of cones or pyramid depressions are formed with a predetermined interval, and an angle formed between a side surface and a surface perpendicular to the groove , or the angle between the side surface and the center line of the recessed portion of the conical or pyramid, formed on the 54.7 to 70 degrees, Taneyui valley bottom of the groove, or the valley bottom of the recess When placing, it is characterized in that the side surface of the groove or at least a portion of the side surface of the recess, is arranged so as to be exposed.

According to the crucible for manufacturing a polycrystalline semiconductor according to the present invention, a plurality of grooves are formed at a predetermined interval on the bottom surface in the crucible, or a conical or pyramidal depression is formed at a predetermined interval. When the semiconductor material is cooled, the bottom of the valley of the groove or the depression is easily cooled, and the crystal is likely to grow along the [100] direction with the seed crystal as a base point, so that a semiconductor crystal having a uniform crystal orientation can be formed. .
The inert atmosphere means a vacuum or an atmosphere in which an inert gas that does not oxidize the semiconductor material when heated is present.

In this case, the angle formed between the side surface of the groove and the surface perpendicular to the groove, or the angle formed between the side surface of the conical or pyramidal depression and the center line is formed at 54.7 to 70 degrees. A crystal can easily grow along the [100] direction as a base point, a semiconductor crystal with a more uniform crystal orientation can be produced, and a polycrystalline semiconductor close to a single crystal can be manufactured.
Here, the angle formed between the side surface of the groove and the surface perpendicular to the surface, or the angle formed between the side surface of the conical or pyramidal depression and the center line is set to 54.7 to 70 degrees [100]. If the direction is the generation plane, the stable plane of the (111) plane is 54.7 degrees, that is, if the angle is larger than 54.7 degrees, single crystals randomly generated from the crucible wall are suppressed by the (111) stable plane. This is because polycrystallization is hindered and grains (particles) become large.
Accordingly, it is preferable that the angle formed between the side surface of the groove and the surface perpendicular to the groove, or the angle formed between the side surface of the concave portion of the cone or the pyramid and the center line is 54.7 to 56 degrees, and the optimum value is 54.7. More than degrees.

In addition, the present invention has been made to achieve the above object, and a polycrystalline semiconductor manufacturing method according to the present invention includes a groove formed on the inner bottom surface of the crucible using the above-described crucible for manufacturing a polycrystalline semiconductor. A seed crystal is arranged at the bottom of the valley or at the bottom of the depression , and a semiconductor material is inserted into the inside, and the semiconductor material in the crucible is heated and melted by a heating means in an inert atmosphere. In the polycrystalline semiconductor manufacturing method of solidifying the molten semiconductor material while gradually removing heat from the bottom where the crystals are arranged, the semiconductor material is Si and the seed crystal is 3C-SiC. It is said.

Since the sublimation temperature of 3C-SiC of the seed crystal is much higher than the melting point of Si (silicon) of the semiconductor material and is chemically stable and high in strength, the conventional silicon single crystal is used as a seed crystal. It is not necessary to perform cooling to prevent melting of the seed crystal while melting Si of the semiconductor material.
Therefore, the energy loss is small as in the prior art, the energy efficiency can be increased, and the manufacturing cost can be reduced. Furthermore, the 3C—SiC single crystal is heavier than the bulk density of 3.16 and the silicon melt density of 2.56, and can be placed on the bottom of the crucible without using a special fixing method.

As this, when the valley portion of the groove formed on the inner bottom surface of the polycrystalline semiconductor manufacture crucibles, or recess 3C-SiC seed crystal valley portion of the are arranged to improve the efficiency of the above-described energy In addition to reducing the manufacturing cost and further eliminating the need for fixing the seed crystal, the bottom of the groove or the recess is efficiently cooled when the semiconductor material is cooled, so that the seed crystal is used as a starting point along the [100] direction. As a result, the crystal grows easily, a semiconductor crystal having a uniform crystal orientation can be produced, and a polycrystalline semiconductor almost as close to a single crystal can be produced.

  As the seed crystal, a 3C-SiC / Si hetero-growth substrate grown on a Si substrate by vapor phase can be used.

As described above, according to the crucible for manufacturing a polycrystalline semiconductor according to the present invention, it is possible to obtain a polycrystalline semiconductor having a crystal orientation close to that of a single crystal.
Moreover, according to the method for producing a polycrystalline semiconductor according to the present invention, a polycrystalline semiconductor can be obtained with good energy efficiency and at a low cost. Moreover, if the said manufacturing method is implemented using the said crucible for polycrystalline semiconductor manufacture, the polycrystalline semiconductor with which the crystal orientation close | similar to a single crystal was arrange | equalized can be obtained.

Hereinafter, a polycrystalline semiconductor manufacturing method according to the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view showing a schematic configuration of a polycrystalline semiconductor manufacturing apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view of a crucible used in the manufacturing apparatus shown in FIG. This device includes a sealed container 1, the inside of which is cut off from the atmosphere and kept in an inert atmosphere. The inert atmosphere may be configured such that the inside of the sealed container 1 is kept in a vacuum by, for example, a vacuum pump, or an inert gas such as argon gas is put in the container. It may be configured to be supplied and maintained in an inert gas atmosphere.
That is, the internal atmosphere of the sealed container 1 may be maintained in a non-oxidizing environment, and the semiconductor may be configured not to be affected by oxidation even if the semiconductor is heated and melted in the sealed container 1.

A cylindrical heating furnace 4 including a heating body 2 and a thermal insulator 3 is provided in the sealed container 1. In addition, an induction heating coil 5 is wound around the outside of the thermal insulator 3, and the heating body 2 is heated by energizing the induction heating coil 5.
Although not shown, a thermocouple, a control circuit, etc. (not shown) are provided to control the heating body 2 to a predetermined temperature, and the power applied to the induction heating coil 5 is controlled. .

  As shown in FIG. 1, a crucible 6 in which a semiconductor material 7 made of Si and a seed crystal 8 made of 3C—SiC are inserted is disposed in an internal space formed by the heating furnace 4 in the sealed container 1. . This crucible 6 is formed, for example, in a bowl shape with silica glass, and is placed on a support base 9.

The support base 9 is formed of, for example, a surface layer, a bottom layer made of graphite, and an intermediate layer made of carbon fiber, and is placed on a pedestal 10 attached to the rotary shaft 11.
Accordingly, when the pedestal 10 is rotated by the rotating shaft 11, the support base 9 and the crucible 6 are also rotated around the rotating shaft 11, and the semiconductor material 7 in the crucible 6 is uniformly heated by this rotation.

  Note that by configuring the rotary shaft 11 to be movable in the vertical direction, the distance between the heating furnace 4 and the crucible 6 can be controlled, and the temperature can be adjusted. Further, in this manufacturing apparatus, it is not necessary to provide a cooling means for cooling the bottom surface of the crucible 6 provided in the conventional apparatus.

As shown in FIG. 2, 3C—SiC, which is the seed crystal 8, is disposed on the flat bottom surface portion of the bowl-shaped crucible 6. This seed crystal 8 is a 3C-SiC / Si hetero-growth substrate in which a 3C-SiC film is vapor-phase grown on the surface of the Si wafer.
In the 3C-SiC / Si hetero-growth substrate, the silicon substrate is melted during the heating and melting of the Si semiconductor material, and only the 3C-SiC single crystal film remains at the bottom of the crucible 6.
Moreover, since the bulk density 3.16 of 3C-SiC is larger than the melt density 2.56 of silicon, the crystal film is maintained at the bottom of the crucible 6 without special fixing means. Is done.

In the polycrystalline semiconductor manufacturing apparatus thus configured, first, a 3C—SiC / Si hetero-growth substrate as the seed crystal 8 is spread over the entire bottom surface of the crucible 6, and Si as the semiconductor material 7 is loaded inside the crucible 6. Enter.
When the Si is dissolved, the temperature of the bottom surface of the bottom of the crucible 6 is controlled to be not less than the melting point of Si and not more than the melting point of the seed crystal. At this time, since the melting point of Si is 1420 degrees, and the melting point of 3C—SiC is 2830 degrees, it can be easily controlled.
In particular, since the single crystal Si that is the same as the semiconductor material 7 is not used for the seed crystal 8 as in the prior art, it is not necessary to cool the bottom of the crucible 6 and energy efficiency can be improved.

After melting the Si semiconductor material 7, cooling of the crucible 6 is started, and a semiconductor crystal is grown along the [100] direction, which is the direction of the surface of the seed crystal 8. At this time, the crystal grows along the direction of the surface of the seed crystal 8 disposed on the bottom surface of the crucible 6, and a polycrystalline semiconductor having a crystal orientation close to that of a single crystal is obtained.
After the semiconductor material 7 is solidified, the crystal is taken out from the crucible 6 and cut into a predetermined thickness to form a Si semiconductor substrate.

  As described above, in the polycrystalline semiconductor manufacturing method according to the present invention, the semiconductor material 7 is placed in the crucible 6 in which the semiconductor seed crystal 8 is arranged on the bottom surface, and the semiconductor is formed in the crucible 6 in an inert atmosphere. It is a polycrystalline semiconductor manufacturing method in which the material 7 is heated and melted by heating means, cooling is started from the bottom of the crucible 6, and the entire crucible is gradually cooled to solidify the molten material. In particular, Si is used as the semiconductor material 7, The seed crystal 8 is characterized in that 3C-SiC is used.

Further, a crucible for manufacturing a polycrystalline semiconductor capable of manufacturing a polycrystalline semiconductor having a crystal orientation close to that of a single crystal will be described with reference to FIGS.
FIG. 3 shows a crucible 20 according to the present invention having a partial cross-section of a silica glass crucible having a plurality of grooves 21 (grooved irregularities) formed at predetermined intervals on the bottom thereof. A 3C-SiC substrate or 3C-SiC / Si that becomes the seed crystal 8 at the bottom 22 of the bottom groove 21
A hetero growth substrate is placed.
Thus, since the groove | channel 22 is formed in the bottom face of the crucible 20, cooling efficiency is improved and crystal solidification starts from the arrange | positioned seed crystal. Therefore, this becomes the base point, and the crystal orientation can be propagated throughout the crucible.

  More preferably, a groove 24 is formed on the bottom outer side 23 of the crucible 20 so as to face the groove 22 so that the thickness of the crucible becomes thin. As a result, the cooling efficiency is further improved, and crystal solidification starts from the arranged seed crystal 8, which becomes the base point and can propagate the crystal orientation throughout the crucible.

Further, in a crucible in which a seed crystal having a plane orientation of (100) is used, the angle α formed between the side surfaces 25 and 26 forming the groove 22 and the plane perpendicular to the crucible is set to 50 to 70 degrees. . More preferably, it is formed at 54 to 56 degrees, and optimally at 54.7 degrees or more.
On the other hand, even in a crucible in which a seed crystal with a (111) plane orientation is used, similarly to the crucible in which a seed crystal with a (100) plane orientation is used, it is perpendicular to the side surfaces 25 and 26 forming the groove 22. The angle α formed with the surface is set to 50 to 70 degrees. More preferably, it is formed at 54 to 56 degrees, and optimally at 54.7 degrees or more.

  Since the groove 21 is formed in this way, it becomes easy to grow a crystal along the [100] direction with the seed crystal 8 as a base point, and a semiconductor crystal having a uniform crystal orientation can be formed. An infinitely close polycrystalline semiconductor can be manufactured.

  Moreover, the groove | channel 22 does not mean only the recessed part extended, but the thing by which the recessed part 27 is arrange | positioned at the array form as shown in FIG. 4 is also included. Then, by disposing the 3C—SiC seed crystal 8 at the bottom of the recess 27, the 3C—SiC seed crystal 8 is similarly used as a base point, and a solidified crystal having a uniform orientation in the entire crucible 28 is obtained.

  Further, as shown in FIG. 5, the crucible 30 may be a plurality of conical or pyramidal depressions 31 formed at a predetermined interval at the bottom thereof. FIG. 5 shows a conical depression 31. In addition, as the hollow part 31 of a pyramid, it is not restricted to a square pyramid as shown in FIG. 6, A polygonal pyramid may be sufficient.

In addition, a 3C—SiC substrate or a 3C—SiC / Si hetero-growth substrate serving as the seed crystal 8 is disposed on the valley bottom 32 of the recess 31. The depth of the valley bottom 32 is formed to be 0.4 to 0.8H of the bottom thickness H of the crucible. This is for efficient cooling.
Thus, since the hollow part 31 is formed in the bottom face of the crucible 30, the cooling efficiency is improved and crystal solidification starts from the arranged seed crystal 8 as in the case of the groove. Therefore, this becomes the base point, and the crystal orientation can be propagated throughout the crucible.

In addition, in a crucible in which a seed crystal having a plane orientation of (100) is used, the angle α formed between the peripheral surface (side surface) forming the conical or pyramidal depression 31 and the center line is 50 to 70 degrees. Is set to More preferably, it is formed at 54 to 56 degrees, and optimally at 54.7 degrees or more.
On the other hand, even in a crucible in which a seed crystal having a (111) plane orientation is used, the side surface and the center forming the conical or pyramidal depression 31 are the same as in the crucible in which a seed crystal having a (100) plane orientation is used. The angle α formed with the line is set to 50 to 70 degrees. More preferably, it is formed at 54 to 56 degrees, and optimally at 54.7 degrees or more.
The pyramid depression 31 is preferably formed in, for example, a regular triangular pyramid or a regular quadrangular pyramid. Further, in a crucible in which a seed crystal having a plane orientation of (100) is used, it is preferable that a plurality of regular quadrangular pyramid depressions are formed at predetermined intervals on the bottom surface of the crucible, and the plane orientation is (111). In the crucible in which the seed crystal is used, it is preferable that a plurality of equilateral triangular pyramid depressions are formed at predetermined intervals on the bottom surface in the crucible.

  As described above, since a plurality of conical or pyramidal depressions 31 formed at a predetermined interval are formed, the crystal is likely to grow along the [100] direction from the seed crystal as a base point, and the crystal orientation A uniform semiconductor crystal can be produced, and a polycrystalline semiconductor close to a single crystal can be manufactured.

  As described above, in the crucible for manufacturing a polycrystalline semiconductor according to the present invention, a plurality of grooves are formed at a predetermined interval on the bottom surface of the crucible, or a plurality of conical or pyramidal depressions are formed at a predetermined interval. Corresponding to the plane orientation of the seed crystal formed, the angle formed between the side surface of the groove and a surface perpendicular to the groove, or the angle formed between the side surface of the conical or pyramidal depression and the center line is set to a predetermined angle. There is a feature in that.

[Example 1]
Using a crucible (a bowl shape with a side of 55 cm and a height of 40 cm) with twelve square pyramid depressions (20 mm / 20 mm per side, 15 mm deep) and 12 rows arranged at the bottom, A seed crystal 3C-SiC / Si is arranged as a seed crystal of orientation (100), and 140 kg of polysilicon is filled in a crucible, and this is heated and melted to a melting point of polysilicon of 1420 ° C. or higher, and a predetermined cooling temperature is set. And solidified by cooling.
When the solidified silicon was cut and the cross section was observed, the semiconductor crystal grew in a uniform direction upward from the top of the depression. It was confirmed that the domain became larger toward the upper side, and the quality of the polycrystalline semiconductor was remarkably improved as compared with the case where a normal crucible was used.

[Example 2]
As a seed crystal with a plane orientation (100) on the bottom of a flat bottom crucible (55 cm side and 40 cm height) as shown in FIGS. 1 and 2, 3C-SiC / Si having a thickness of 1 μm as a seed crystal of plane orientation (100) The substrate was placed over the entire surface and filled with 140 kg of polysilicon to be melted.
This was heated and melted to a melting point of polysilicon of 1420 ° C. or higher, and cooled and solidified at a predetermined cooling temperature. When the solidified silicon was cut and the cross section was observed, the semiconductor crystal had grown from the bottom to the top of the crucible with a uniform direction. Although the 3C-SiC film remains at the bottom of the solidified silicon due to the difference in thermal expansion, the quality of the polycrystalline semiconductor is improved compared to the case where a Si single crystal is used as a seed crystal. Was.

Example 3
As shown in FIG. 3, a 3C-SiC film thickness is formed as a seed crystal with a plane orientation (100) on the groove bottom of a grooved crucible (a saddle shape having a side of 55 cm, a height of 40 cm, a groove width of 1 cm, and a depth of 1 cm). A 1 μm 3C—SiC / Si substrate was placed and filled with 140 kg of polysilicon to be melted.
This was heated and melted to a melting point of polysilicon of 1420 ° C. or higher, and cooled and solidified at a predetermined cooling temperature. When the solidified silicon was cut and the cross-section was observed, the semiconductor crystal grew from the seed crystal arranged at the bottom of the groove with a uniform direction toward the top of the crucible from the bottom. The quality of the polycrystalline semiconductor is large with highly oriented domains, and is improved as compared with the case where the seed crystal is arranged on the entire surface of the flat bottom.

Example 4
A crucible in which a plurality of quadrangular pyramid-shaped depressions as shown in FIG. 6 are formed (one side of 55 cm, a height of 40 cm in a bowl shape, a depression: a square pyramid with a side of 1 cm, a depth of 0.8 cm, and 24 depressions in a row × A 3C-SiC / Si substrate having a 3C-SiC film thickness of 1 μm was placed as a seed crystal with a plane orientation (100) at the bottom of the valleys of the 24 rows of depressions, and 140 kg of polysilicon to be melted was filled. . This was heated and melted to a melting point of polysilicon of 1420 ° C. or higher, and cooled and solidified at a predetermined cooling temperature.
When the solidified silicon was cut and the cross section was observed, the semiconductor crystal grew in a uniform direction upward from the bottom seed crystal part of the depression. It was confirmed that the domain became larger toward the upper side, and the quality of the polycrystalline semiconductor was remarkably improved as compared with the case where a normal crucible was used.

In the above description of the embodiment of the crucible for manufacturing a polycrystalline semiconductor, the case where Si is used as the semiconductor material and the 3C-SiC / Si substrate is used as the seed crystal has been described as an example, but BP / Si and ZrSO ₄ are used as the seed crystal. It is also possible to apply it.
On the other hand, the polycrystalline semiconductor manufacturing method is applied when Si is used as a semiconductor material and 3C-SiC is used as a seed crystal.

FIG. 1 is a cross-sectional view showing a schematic configuration of a polycrystalline semiconductor manufacturing apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view of a crucible used in the manufacturing apparatus shown in FIG. FIG. 3 is a sectional view showing a schematic configuration of a crucible for manufacturing a polycrystalline semiconductor according to an embodiment of the present invention. FIG. 3 is a sectional view showing a modification of the crucible for manufacturing a polycrystalline semiconductor according to the embodiment of the present invention. FIG. 5 is a sectional view showing another modification of the crucible for manufacturing a polycrystalline semiconductor according to the embodiment of the present invention. FIG. 6 is a plan view showing another modification of the recess formed in the crucible.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Airtight container 2 Heating body 3 Thermal insulator 4 Heating furnace 5 Induction heating coil 6 Crucible 7 Semiconductor material 8 Seed crystal 9 Support base 10 Base 11 Rotating shaft 20 Crucible 21 Groove 22 Valley bottom 23 Bottom outside 24 Groove 25 Side 26 Side 26 Recessed portion 28 Crucible 30 Crucible 31 Recessed portion 32 Valley bottom 33 Side surface (circumferential surface)

Claims (3)

A seed crystal is arranged on the inner bottom surface of the crucible, and a semiconductor material is charged therein. Under an inert atmosphere, the semiconductor material in the crucible is heated and melted by heating means, and heat is applied from the bottom where the seed crystal is arranged. In a crucible for manufacturing a polycrystalline semiconductor, which solidifies molten semiconductor material gradually upward while taking
On the bottom surface in the crucible, a plurality of grooves are formed with a predetermined interval, or a plurality of cones or pyramid depressions are formed with a predetermined interval,
An angle formed between a side surface and a vertical surface of the groove, or an angle formed between a side surface of the conical or pyramidal depression and a center line is formed at 54.7 to 70 degrees ,
When the seed crystal is disposed at the bottom of the groove or at the bottom of the recess, the side surface of the groove or at least a part of the side of the recess is disposed. A crucible for manufacturing crystalline semiconductors. Using a crucible as claimed in claim 1, wherein the valley portion of the formed grooves to crucible inside bottom surface, or together with placing the seed crystal on the valley portion of the recess, is charged with the semiconductor material inside the crucible In an inert atmosphere, a polycrystalline semiconductor in which a semiconductor material in a crucible is heated and melted by a heating means, and the molten semiconductor material is solidified gradually upward while removing heat from the bottom where the seed crystal is disposed. In the manufacturing method,
A method for producing a polycrystalline semiconductor, wherein the semiconductor material is Si and the seed crystal is 3C-SiC. The seed crystal, Si polycrystalline semiconductor manufacturing method according to claim 2 Symbol mounting, characterized in that on a substrate a hetero growth substrate to 3C-SiC / Si was vapor-grown.

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