JP6384921B2 - Silicon single crystal generation apparatus and silicon single crystal generation method - Google Patents

Description

  The present invention relates to a silicon single crystal production apparatus that produces a silicon single crystal by a casting method.

  The Czochralski (CZ) method and the floating zone (FZ) method are generally performed as methods for producing a silicon single crystal. In the CZ method, polycrystalline silicon is melted in a crucible and pulled together with a seed crystal having an orientation desired to be produced to produce a single crystal. In the FZ method, a seed crystal is disposed under a rod-shaped polycrystalline silicon, and a boundary portion between the seed crystal and the polycrystalline is melted by heating to generate a single crystal. Either method can produce high-quality silicon single crystals, but the equipment is expensive and the work process is cumbersome, making it unsuitable for large-scale products such as solar panels and mass production. Technology.

  Then, in order to produce | generate the large sized silicon crystal used for a solar panel etc. efficiently, the casting method is used (for example, refer patent document 1). In the casting method, solid silicon can be melted in a crucible and cooled to produce a large amount of silicon crystals at low cost. However, since this conventional casting method mainly produces polycrystals, a technique for efficiently producing a large amount of high-purity single crystals by the casting method is desired.

  With regard to the above problems, Patent Document 2 discloses a technique for producing a silicon single crystal using a casting method. The technique shown in Patent Document 2 uses a further heater arranged on the wall of the crucible placed on the heat sink while extracting heat from the heat sink arranged on the bottom of the crucible where the seed crystal is arranged. A technique for generating a silicon single crystal by causing growth of a seed crystal in a side region by heating is disclosed.

JP 2003-267717 A Special table 2011-528308 gazette

  However, the technique shown in Patent Document 2 requires the seed crystal to have a size corresponding to the entire bottom surface of the crucible, which increases the cost and is very difficult to increase in size. End up. Also, if the seed crystal is made small, the seed crystal information is not transmitted to the portion where the seed crystal is not arranged, so that polycrystalline silicon is generated, resulting in high quality silicon. There is a problem that a single crystal cannot be produced.

  In addition, there is a method in which the bottom surface of the crucible is divided into a plurality of blocks and a seed crystal is arranged for each block to grow, but there is a problem in that the growth collides between the blocks, resulting in a defect.

  The present invention provides a silicon single crystal production apparatus capable of easily producing a high-quality and large-sized silicon single crystal using a casting method.

  A silicon single crystal production apparatus according to the present invention includes a crucible in which a single silicon single crystal seed crystal is held in a partial region of a bottom portion and solid and / or liquid silicon is held, and the crucible An endothermic part that absorbs heat from below the crucible including at least the seed crystal region, and a heating part that heats a peripheral region of the region cooled by the endothermic part. The heat flux vector A and the heat flux vector B by the heating unit are controlled while maintaining a relationship of A × B <0.

  Thus, in the silicon single crystal production apparatus according to the present invention, the relationship between the heat flux vector A by the heat absorption part and the heat flux vector B by the heating part is A × B <0, that is, the direction of heat flow. Is controlled while maintaining the reverse relationship, it allows growth from the seed crystal in the upward direction and at the same time allows crystal growth from the seed to the lateral direction. In contrast, it is possible to reliably transmit seed crystal information and to produce a high-quality silicon single crystal with a minimum content of polycrystals.

  In addition, high-quality and large-sized silicon single crystals can be produced from a single small seed crystal in a simple work process using only a thermal control using a casting method, so mass production is performed with inexpensive equipment. There is an effect that it becomes possible.

  In the silicon single crystal production apparatus according to the present invention, the endothermic part cools the inside of the crucible from the bottom part of the crucible, and at the same time, the peripheral part of the region where the heating part is cooled by the endothermic part is defined as the bottom part of the crucible. It heats with the heat source arrange | positioned more downward.

  As described above, in the silicon single crystal generation apparatus according to the present invention, the peripheral region of the region cooled by the endotherm is lowered from the bottom surface of the crucible while absorbing the region of the seed crystal of the silicon single crystal from the bottom portion of the crucible. By heating with a heat source arranged in the above, it is possible to grow from the seed crystal in the upward direction and also to grow the crystal in the lateral direction, from a small seed crystal to a high-quality silicon single crystal containing no polycrystal There is an effect that it can be generated.

  The silicon single crystal generation apparatus according to the present invention includes a control unit that controls a heat flow rate of the heat absorption unit and the heating unit, and the control unit maintains at least a part of the silicon single crystal as a solid as a seed crystal. As described above, the temperature of the seed crystal region is adjusted by controlling the heat flow rate of the heat absorption part and the heating part.

  As described above, in the silicon single crystal production apparatus according to the present invention, the heat flow rate of the endothermic part and the heating part is controlled so that at least a part of the silicon single crystal maintains a solid as a seed crystal. Since the temperature of the region is adjusted, there is an effect that information can be surely transmitted from the seed crystal to produce a high-quality silicon single crystal that does not contain a polycrystal.

  The silicon single crystal production apparatus according to the present invention includes a control unit that controls a heat flow rate of the heat absorption unit and the heating unit, and the control unit is solidified by a growth surface of the silicon single crystal and a bottom surface of the crucible. Further, the heat flow rate of the heat absorption part and the heating part is controlled so that the angle of the silicon single crystal is maintained larger than 90 °.

  Thus, in the silicon single crystal production apparatus according to the present invention, the angle of the solidified silicon single crystal formed by the growth surface of the silicon single crystal and the bottom surface of the crucible is maintained larger than 90 ° (that is, in the lateral direction). Since the solid / liquid interface of the growing silicon crystal is maintained at less than 90 degrees in the growth direction with respect to the bottom of the crucible), the heat flow rate of the endothermic part and the heated part is controlled so As a result, information can be transmitted to produce a high-quality silicon single crystal that does not contain polycrystals.

  The silicon single crystal production apparatus according to the present invention controls the heat flux of the heat absorption part and / or the heating part based on the temperature detection means for detecting the temperature at a predetermined location in the crucible and the detected temperature. Control means.

  Thus, in the silicon single crystal production apparatus according to the present invention, in order to detect the temperature of a predetermined location in the crucible and control the heat flux of the endothermic part and / or the heating part based on the detected temperature, It is possible to produce a high-quality silicon single crystal that does not contain polycrystals and to perform work efficiently.

  A method for producing a silicon single crystal according to the present invention comprises a step of introducing a silicon single crystal seed crystal into a bottom portion of a crucible, and introducing solid silicon as a raw material of the generated silicon crystal; A melting step for heating and melting, and a crystal generation step for generating a silicon crystal by heating the molten raw material from below the crucible including at least the seed crystal region and simultaneously heating a peripheral region of the endothermic region The heat flux vector A due to heat absorption and the heat flux vector B due to heating are executed while maintaining a relationship of A × B <0.

  In the silicon single crystal production method according to the present invention, the crystal production step cools the inside of the crucible from the bottom surface of the crucible, and at the same time, the peripheral region of the region to be cooled is disposed below the bottom surface of the crucible. It heats with the heat source made.

  In the silicon single crystal production method according to the present invention, the crystal production step controls the heat absorption and the heat flow rate of the heating so that at least a part of the silicon single crystal maintains a solid as a seed crystal, The temperature of the seed crystal region is adjusted.

  In the method for producing a silicon single crystal according to the present invention, the crystal production step includes the endothermic process and the endothermic process so that an angle of the silicon single crystal formed by a growth surface of the silicon single crystal and a bottom surface of the crucible is maintained larger than 90 °. It is executed by controlling the heat flow rate of the heating.

  In the silicon single crystal production method according to the present invention, the crystal production step is executed by controlling the heat absorption and / or the heat flux of the heating based on the temperature detected at a predetermined location in the crucible. It is.

It is sectional drawing of the silicon single crystal production | generation apparatus which concerns on 1st Embodiment. It is a figure which shows the conventional general silicon crystal growth method. It is a figure which shows the crystal growth of the silicon | silicone implement | achieved with the silicon single crystal production | generation apparatus which concerns on 1st Embodiment. It is an image figure which shows an example of the heating from a heat source in the past, and an example of the heating from the heat source in the silicon single crystal production | generation apparatus which concerns on 1st Embodiment. It is a flowchart which shows the procedure of the silicon single crystal production | generation method which concerns on 1st Embodiment. It is a figure which shows the growth process at the time of growing a silicon single crystal with the silicon single crystal production | generation method concerning 1st Embodiment. It is a figure which shows the distribution of the single crystal and polycrystal of the silicon | silicone produced | generated with the silicon single crystal production | generation method concerning 1st Embodiment. It is a figure which shows the relationship between the angle which a silicon melt makes between a crucible bottom face and a growth surface, and the growth time in the silicon single crystal production | generation method which concerns on 1st Embodiment.

  Embodiments of the present invention will be described below. The present invention can be implemented in many different forms. Also, the same reference numerals are given to the same elements throughout the present embodiment.

(First embodiment of the present invention)
A silicon single crystal generation apparatus according to the present embodiment and a silicon single crystal generation method using the silicon single crystal generation apparatus will be described with reference to FIGS. The silicon single crystal production apparatus according to the present embodiment is for producing a silicon (Si) semiconductor single crystal mainly used as a solar panel by a casting method.

  The casting method used in the silicon single crystal production apparatus according to the present embodiment is to put a solid silicon raw material into a crucible and melt it at a high temperature, and to cool and solidify the molten liquid silicon by a predetermined method. Thus, a silicon crystal having a target shape is obtained. Normally, silicon solidified by this casting method becomes polycrystalline, but by placing a seed of single crystal in advance at the bottom of the crucible and performing a cooling method as described in detail below, there are few defects. High quality single crystals can be produced.

  An example of the silicon single crystal generation apparatus according to this embodiment is shown in the cross-sectional view of FIG. In the silicon single crystal generation apparatus 100, crucibles 3 and 4, which are containers for storing molten liquid silicon 1 and silicon crystals 2 generated by solidification of a part thereof, are placed on a pedestal 5. A bearing stand 6 connected to the pedestal 5 and supporting the pedestal 5 is disposed so as to be vertically movable. A heater 12-14 is disposed around the crucibles 3 and 4, the pedestal 5 and the bearing base 6, and temperature control for heating and cooling is performed. On the outermost periphery of the silicon single crystal generation apparatus 100, a heat insulating material 7-11 for blocking heat is disposed to block the movement of heat energy from the outside.

  FIG. 2 shows a conventional general silicon crystal growth method. FIG. 2 (A) shows the state of silicon in the crucibles 3 and 4 at a certain moment, and FIG. 2 (B) shows the crucible 3 when the growth has progressed from the state of FIG. 2 (A) over time. The state of silicon in 4 is shown. Conventionally, as shown in FIG. 2 (A), it has been generally practiced to cool the liquid silicon melted in the crucibles 3 and 4 from the bottom of the crucibles 3 and 4 to grow crystals. If the cooling is continued as it is, the interface between the liquid silicon and the solid silicon changes as the silicon crystal grows as shown in FIG. As is apparent from FIG. 2B, when a silicon crystal is grown by a conventional method, a region that cannot grow from a seed crystal of a silicon single crystal (a region indicated by a one-dot chain line in the drawing) is generated. The grown silicon crystal becomes polycrystalline.

  In order to eliminate the polycrystalline region, for example, a single crystal seed crystal may be arranged so as to cover the entire bottom surface of the crucibles 3 and 4, but the size of the seed crystal becomes very large, including the cost. Difficult to enlarge. When crystal growth is performed with a small seed crystal, as shown in FIG. 2A, the angle formed by the crystal growth interface and the bottom surfaces of the crucibles 3 and 4 (angle formed by the solid silicon single crystal) is 90 degrees. Therefore, as described above, a region that cannot grow from the seed crystal of the silicon single crystal is generated. In order to solve such a problem, in the present embodiment, the peripheral region of the region cooled from the bottom surface of the crucibles 3 and 4 is simultaneously heated from the bottom surface of the crucibles 3 and 4.

  FIG. 3 is a diagram showing silicon crystal growth realized by the silicon single crystal generation apparatus according to the present embodiment. FIG. 3 (A) shows the state of silicon in the crucibles 3 and 4 at a certain moment, and FIG. 3 (B) shows the crucible 3 when the growth has progressed from the state of FIG. 3 (A) over time. The state of silicon in 4 is shown. As shown in FIG. 3A, in this embodiment, the seed crystal region of the silicon single crystal disposed on the bottom surfaces of the crucibles 3 and 4 is cooled, and the peripheral region of the cooled region is simultaneously heated. To do.

  By doing so, the growth of the silicon single crystal proceeds so that the interface between the liquid silicon and the solid silicon forms a substantially ellipsoid as shown in FIG. That is, the angle formed by the crystal growth interface and the bottom surfaces of the crucibles 3 and 4 (the angle formed by the solid silicon single crystal) is larger than 90 degrees, and as shown in FIG. 2B, a region that cannot be grown from the seed crystal of the silicon single crystal as shown in FIG. 2B does not occur, and the seed crystal information is accurately transmitted even in the lateral growth. Quality silicon single crystals can be produced.

  FIG. 4 is a diagram illustrating an example of heating from a heat source. 4A shows an example of heating from the side surface of the conventional crucible, and FIG. 4B shows an example of heating from the bottom surface of the crucible in the present embodiment. As can be seen from FIG. 4, since the heat flux a to the heat source A is downward and the heat flux b from the heat source B is obliquely downward at the bottom of the crucible, the relationship between the heat flux a and b is a × b ≧ 0. Become. That is, as shown in FIG. 4A, the angle formed by the silicon single crystal between the crystal growth interface and the bottom surfaces of the crucibles 3 and 4 is 90 degrees or less, and the silicon polycrystal grows as described above. An area will be generated.

  On the other hand, in the case of silicon crystal growth realized by the silicon single crystal generation apparatus according to the present embodiment, the directions of the heat flux a and the heat flux b are opposite to each other as shown in FIG. Therefore, the relationship is a × b <0. That is, the angle formed by the silicon single crystal between the crystal growth interface and the bottom surfaces of the crucibles 3 and 4 is greater than 90 degrees, and as described above, the information on the seed crystal is accurately transmitted and the high-quality silicon single crystal Can be generated.

  Next, a silicon single crystal generation method using the silicon single crystal generation apparatus according to this embodiment will be described. FIG. 5 is a flowchart showing the procedure of the silicon single crystal generation method according to this embodiment. First, a seed crystal of silicon single crystal is put into the crucibles 3 and 4 and placed on the bottoms of the crucibles 3 and 4 (S1). At this time, the seed crystal is preferably arranged in the vicinity of the center of the bottom surface of the crucibles 3 and 4, but it is not always necessary to be in the vicinity of the center as long as the heat absorption by the heat absorption part is possible. For example, when the bottom surfaces of the crucibles 3 and 4 are rectangular, they may be arranged at any corner. Moreover, it is not preferable to divide the seed crystal into a plurality of regions and arrange them in a plurality of regions, and it is preferable to arrange one seed crystal in one region. When the seed crystal is arranged, a raw material to be a silicon single crystal to be generated is put into the crucibles 3 and 4 (S2). The crucibles 3 and 4 are heated by the heater 12-14 to melt the silicon raw material (S3). At this time, heating is performed so that at least a part of the seed crystal is maintained as a solid.

  When the raw material is melted, the seed crystal region is cooled from the bottoms of the crucibles 3 and 4, and the raw material is solidified while simultaneously heating the peripheral region of the cooled region (S4). At this time, the seed crystal region absorbs heat from the heat source A at the bottom of the crucibles 3 and 4, and the peripheral region of the cooled region is heated by the heat source B below the bottom of the crucibles 3 and 4. By doing so, the relationship between the heat flux a of the heat source A and the heat flux b of the heat source B can be a × b <0, and the angle formed by the crystal growth interface and the bottom surfaces of the crucibles 3 and 4 (silicon The angle formed by the single crystal is larger than 90 degrees, and the information of the seed crystal is accurately transmitted, so that a high-quality silicon single crystal can be generated. At this time, the heat flux is controlled by monitoring the temperature of the entire crucibles 3 and 4. While monitoring the temperature of the entire crucibles 3 and 4, heating and heat absorption are stopped at predetermined timings (S5 and S6) to complete the generation of the silicon single crystal. The stopping of heating and endothermic heat is controlled according to the shape of the crucibles 3 and 4 and the depth of the melt.

  FIG. 6 is a diagram showing a growth process when a silicon single crystal is grown by the method described above. The silicon crystal grows sequentially from FIG. 6A and finally grows to FIG. 6H, and the generation of the silicon single crystal is completed. As can be seen from FIG. 6, the growth proceeds radially (marshmallows, spheres, ellipsoids) around the seed crystal, and finally a polycrystal is formed in part as shown in FIG. Most of it can be produced as a single crystal.

  FIG. 8 is a diagram showing the relationship between the growth time when the silicon single crystal is grown by the above method and the angle formed by the silicon raw material melt between the crystal growth interface and the bottom surfaces of the crucibles 3 and 4. is there. Each plot (a) to (h) in the graph corresponds to (A) to (H) in FIG. In each step, by controlling the endotherm and heating based on the temperature of the entire crucible, the angle formed by the melt between the crystal growth interface and the bottom surfaces of the crucibles 3 and 4 (corresponding to the vertical axis in FIG. 8) is 90. Less than degrees. That is, it can be seen that the angle formed by the silicon crystal between the interface of crystal growth and the bottom of the crucible is always maintained at 90 degrees or more, and the crystal growth proceeds in a marshmallow shape (spherical shape, elliptical shape).

  As described above, according to the silicon single crystal generation apparatus and the silicon single crystal generation method using the apparatus according to the present invention, it is possible to grow a crystal from the seed crystal in the lateral direction instead of the upward direction. A high-quality silicon single crystal containing no crystals can be produced. In addition, high-quality and large-sized silicon crystals can be generated by a simple work process using only the heat control from the bottom of the crucible using the casting method, enabling mass production with inexpensive equipment. Become.

DESCRIPTION OF SYMBOLS 1 Liquid silicon 2 Silicon crystal 3-4 Crucible 5 Base 6 Bearing stand 7-11 Heat insulating material 12-14 Heater 100 Silicon single crystal production | generation apparatus

Claims (6)

A crucible in which a single silicon single crystal seed crystal is held in a partial region of the bottom portion and solid and / or liquid silicon is held;
Wherein the seed crystal in and the plane of the bottom below the bottom surface of坩堝is disposed at a position corresponding to the position to be held, from below of the crucible contains a region of at least the seed crystal silicon melt An endothermic part that absorbs heat;
The heat sink is disposed in a region below the bottom surface of the crucible and outside the heat absorbing portion in the surface of the bottom surface, and the heat absorbing portion is cooled by the heat absorbing portion simultaneously with cooling the inside of the crucible from the bottom surface portion of the crucible. A heating section for heating the peripheral area of the area to be
The heat flux vector A by the heat absorption part is a direction from the top to the bottom of the crucible, and the heat flux vector B by the heating part is a direction from the bottom to the top of the crucible, the vector A and The vector B is controlled so as to maintain a relationship of A × B <0 that is opposite to each other, and from the seed crystal with respect to the growth surface of the silicon single crystal that is the liquid / solid interface in the crucible. As the silicon single crystal grows, the liquid-side silicon melt is heated by the heating unit, and the solid-side silicon single crystal is cooled by the heat-absorbing unit, so that the growth surface of the silicon single crystal and the crucible a silicon single crystal producing apparatus silicon single crystal which is characterized that you grow solid side of the angle bottom formed of to be larger than 90 °. The silicon single crystal production apparatus according to claim 1,
Control means for controlling the heat flow rate of the heat absorption part and the heating part,
The control means adjusts the temperature of the seed crystal region by controlling the heat flow rate of the heat absorption part and the heating part so that at least a part of the silicon single crystal maintains a solid as a seed crystal. A silicon single crystal production apparatus characterized by the above. In the silicon single crystal production apparatus according to claim 1 or 2 ,
Temperature detecting means for detecting the temperature of a predetermined location in the crucible;
Control means for controlling a heat flow rate of the heat absorption part and the heating part ,
A silicon single crystal generating apparatus , wherein the heat flux of the heat absorption part and / or the heating part is controlled based on the temperature detected by the temperature detection means . A raw material charging step of charging a seed crystal of silicon single crystal into the bottom part in the crucible and charging solid silicon as a raw material of the generated silicon crystal;
A melting step of heating and melting the raw material;
An endothermic portion disposed at a position below the bottom surface of the crucible and corresponding to a position where the seed crystal is held in the surface of the bottom surface includes at least the seed crystal region. At the same time as absorbing heat from the bottom of the crucible, a heating region disposed in a region below the bottom surface of the crucible and outside the endothermic portion in the plane of the bottom surface is a peripheral region of the region cooled by the endothermic portion Forming a silicon crystal by heating
In the crystal generation step, a heat flux vector A in the direction from the top to the bottom of the crucible due to the endotherm and a heat flux vector B in the direction from the bottom to the top of the crucible due to heating by the heating means are The silicon single crystal is grown from the seed crystal at the growth surface of the silicon single crystal, which is the liquid / solid interface in the crucible. Accordingly, the silicon melt on the liquid side is heated by the heating unit, and the silicon single crystal on the solid side is cooled by the endothermic unit, so that the growth surface of the silicon single crystal and the bottom surface of the crucible form the solid side A method for producing a silicon single crystal, characterized in that the silicon single crystal is grown so that the angle of is larger than 90 ° . In the silicon single crystal production method according to claim 4,
The crystal generation step adjusts the temperature of the region of the seed crystal by controlling the heat absorption and the heat flow rate of the heating so that at least a part of the silicon single crystal remains solid as a seed crystal. A method for producing a silicon single crystal. In the silicon single crystal production method according to claim 4 or 5 ,
A method for producing a silicon single crystal, wherein the crystal production step is executed by controlling the heat absorption and / or the heat flux of the heating based on a temperature detected at a predetermined location in the crucible .

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