JP5262346B2 - Method for producing silicon single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing process of a silicon single crystal which is capable of controlling first dislocation generation in a shoulder process where a silicon single crystal expands its diameter and grows and producing a silicon single crystal at a high productivity and a silicon single crystal. <P>SOLUTION: The manufacturing process grows a silicon single crystal 1 by pulling the silicon single crystal from silicon melt 5 contained in a crucible 4 using a highly volatile dorpant for resistance adjustment while feeding Ar gas and comprises a shoulder growth step to grow the silicon single crystal 1 to an ingot having a specific diameter and a body growth step to grow the ingot grown in the shoulder growth step to have the specific diameter to a rod-like shape. In the shoulder growth step, the distance L1 between the bottom edge 11a of a gas distributing column 11 to distribute Ar gas and the free liquid surface 51 of the silicon melt 5 is set larger than 30 mm. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a silicon single crystal manufacturing method and a silicon single crystal, and in particular, a silicon single crystal manufacturing method capable of manufacturing a low-resistance silicon single crystal used as a semiconductor material with high production efficiency, and , And the silicon single crystal obtained thereby.

  Generally, as a method for growing a silicon single crystal, there are methods called FZ method and Czochralski method (CZ method). The CZ method is a method of growing a silicon single crystal by bringing a seed crystal into contact with a silicon melt in a crucible and slowly rotating it to produce an ingot. Performed in an Ar gas atmosphere. Moreover, in such a CZ method, first, after a silicon single crystal is expanded to an ingot of a predetermined diameter in a process called a shoulder process, the ingot is grown in a rod shape in the process of the trunk process. A series of processes is performed (for example, refer to Patent Document 1).

  However, in the conventional method as described in Patent Document 1, for example, for a semiconductor having a low resistance of 10 mΩcm or less using a highly volatile resistance adjusting dopant such as As, red phosphorus, and Sb. In the silicon single crystal manufacturing process, dislocations frequently occur in the shoulder process. For this reason, since it is necessary to repeat the crystal pulling from the silicon melt many times, there is a problem that the cycle time of crystal growth becomes long and the productivity becomes low. In particular, the resistivity is as low as 4 mΩcm or less. This becomes conspicuous when growing a silicon single crystal for semiconductor which is a resistor.

  Although the cause of frequent dislocations in the shoulder process as described above is not clear, for example, in crystal pulling growth using a non-volatile dopant such as boron (B) or phosphorus (P), the shoulder It is clear that dislocations sometimes occur during the partial process, but dislocations do not occur as frequently as when a highly volatile resistance adjusting dopant is used. For this reason, it is considered that the cause of dislocation formation in the shoulder process is related to the volatilized dopant.

  Here, conventionally, in the manufacturing process of a low-resistance silicon single crystal for semiconductor using a highly volatile resistance adjusting dopant, the lower end of the Ar gas rectifying cylinder in the shoulder process and the free liquid of silicon melt The distance between the surfaces (hereinafter sometimes referred to as a gap) is usually in the range of about 10 to 30 mm, as in the case of using a nonvolatile resistance adjusting dopant. Similarly, also in the trunk process following the shoulder process, the gap between the lower end of the gas rectifying cylinder and the free liquid level of the silicon melt is in the range of about 10 to 30 mm.

  In addition, in the manufacturing process of a low resistance semiconductor silicon single crystal using a highly volatile resistance adjusting dopant, a large amount of dopant is added to make the resistance lower, and in particular, the resistivity is 4 mΩcm or less. A large amount is added when manufacturing a silicon single crystal for a semiconductor. At this time, since highly volatile dopants such as As, red phosphorus, and Sb usually have a low segregation coefficient, compositional supercooling occurs at the solid-liquid interface of the crystal-melt, and dislocations are likely to occur. It is necessary to increase the melt temperature gradient in the direction perpendicular to the interface. For this reason, a method of reducing the gap between the lower end of the gas rectifying cylinder and the free liquid surface of the silicon melt is usually employed so that the grown crystal is not heated from the side surface side. On the other hand, when the gap between the lower end of the gas flow straightening cylinder and the free liquid surface of the silicon melt is increased, the temperature gradient of the crystal is reduced, which is disadvantageous in terms of preventing the compositional overcooling as described above. It will be.

  In addition, the compositional supercooling in the above description refers to J.I. W. Rutter and B.M. This is the first supercooling mechanism proposed by Chalmers (for example, see Non-Patent Document 1). For example, in the following general formula (1), compositional supercooling does not occur in the case of the relationship represented by the left side> the right side. On the other hand, in the case of the relationship represented by the left side <the right side, compositional supercooling occurs. Therefore, in conventional techniques such as the technique described in Non-Patent Document 1, increasing the temperature gradient of the silicon melt is a method for preventing compositional supercooling.

As described above, in the manufacturing process of a low-resistance semiconductor silicon single crystal using a highly volatile resistance adjusting dopant such as As or Sb, the segregation coefficient is small, for example, As is 0.35 and Sb is 0.023. For this reason, the dopant concentration is high in the latter half part of the trunk grown by the trunk process, and dislocation due to compositional supercooling tends to occur, while the dopant concentration in the shoulder process is higher than that in the trunk process. Is considered to be in a state where the concentration is low and compositional supercooling hardly occurs.
JP 2005-15296 A Hideo Nakae, “Coagulation optics”, Agne, p114-p117

  However, as a result of diligent research by the present inventors, in an actual shoulder process in the case where a low resistance semiconductor silicon single crystal is grown using a highly volatile resistance adjusting dopant by a conventional method, It has been clarified that dislocations become remarkable as compared with non-volatile crystals doped with dopants such as B and P. For this reason, in the shoulder process, it is necessary to repeat the crystal pulling from the silicon melt many times, and the time (manufacturing cycle time) for manufacturing one single crystal ingot becomes very long, and the productivity is increased. There was a big problem that the remarkably decreased.

  The present invention has been made in view of the above problems, and can suppress dislocations in a shoulder process for growing a silicon single crystal while expanding the diameter, and can produce a low-resistance silicon single crystal used as a semiconductor material with high production. An object is to provide a method for producing a silicon single crystal that can be produced efficiently, and a silicon single crystal produced thereby.

  The inventors of the present invention have intensively studied the shoulder growth process (shoulder process) for growing a silicon single crystal while expanding the diameter, and found that the gap between the lower end of the gas rectifying cylinder and the free surface of the silicon melt in the shoulder process. It has been found that dislocations can be prevented from occurring by setting the distance (gap) between the two to an appropriate range.

That is, the present invention uses a highly volatile resistance-adjusting dopant, supplies Ar gas, and grows a silicon single crystal having a low resistivity of 10 mΩcm or less from a silicon melt contained in a crucible. A method for producing a silicon single crystal,
A shoulder growth step for expanding the silicon single crystal to an ingot having a predetermined diameter; and a trunk growth step for growing the ingot grown to a predetermined diameter in the shoulder growth step into a rod shape.
In the shoulder growth step, the distance between the lower end of the gas rectifying cylinder for rectifying the Ar gas and the free surface of the silicon melt is reduced to 35 mm or more and 160 mm so as to reduce the thermal stress generated in the crystal. The method for producing a silicon single crystal is characterized in that the distance is larger than the distance in the trunk growth step.
The method for producing a silicon single crystal according to the present invention uses a highly volatile resistance adjusting dopant, supplies Ar gas, and grows the silicon single crystal while pulling up the silicon single crystal from the silicon melt contained in the crucible. A shoulder growth step for expanding the silicon single crystal to an ingot having a predetermined diameter, and a body growth step for growing the ingot grown to a predetermined diameter in the shoulder growth step into a rod shape. The shoulder growth step can be performed with a distance between the lower end of the gas rectifying cylinder for rectifying the Ar gas and the free liquid level of the silicon melt being greater than 30 mm.

  According to such a configuration, when a silicon single crystal for semiconductor having a low resistance of 10 mΩcm or less is grown using a highly volatile resistance adjusting dopant such as As, red phosphorus, and Sb, the silicon single crystal is grown. Dislocation can be suppressed in the shoulder growth process (shoulder process) in which growth is performed while expanding the diameter. This reduces the number of repeated crystal pulls from the silicon melt in the shoulder growth process, and shortens the manufacturing cycle time, making it possible to manufacture silicon single crystals with high production efficiency. It becomes.

In the method for producing a silicon single crystal of the present invention, in the shoulder growth step, the distance between the lower end of the gas rectifying cylinder and the free liquid level of the silicon melt is the distance in the trunk growth step. It is possible to use a method that is performed with a larger distance.
According to such a configuration, in the shoulder growth process (shoulder process), since dislocations at the shoulder of the silicon single crystal to be grown are suppressed, the frequency of the redrawing process of the crystal pulling is reduced, and the shoulder growth The manufacturing cycle time in the process can be shortened. On the other hand, in the trunk growth process (trunk process), the melt temperature gradient in the direction perpendicular to the solid-liquid interface between the silicon single crystal and the silicon melt can be increased, so even when the dopant concentration increases. Thus, it becomes possible to prevent compositional supercooling and to suppress dislocations in the body of the silicon single crystal to be grown. Thereby, since the manufacturing cycle time can be shortened similarly to the above, it becomes possible to manufacture a silicon single crystal with high production efficiency.

The present invention also provides a silicon single crystal produced by the above-described method for producing a silicon single crystal of the present invention.
Since the silicon single crystal of the present invention is obtained by the production method of the present invention, the crystal quality is excellent and the cost is low.

  According to the method for producing a silicon single crystal of the present invention, with the above configuration, since dislocation can be suppressed in the shoulder growth step, it is possible to reduce redrawing of the crystal from the silicon melt many times, and the production cycle time. This makes it possible to manufacture a silicon single crystal for semiconductors having a low resistance with high production efficiency.

Hereinafter, an embodiment of a method for producing a silicon single crystal and a silicon single crystal according to the present invention will be described with reference to the drawings as appropriate.
1 and 2 are schematic cross-sectional views showing an example of a silicon single crystal pulling apparatus 30 used in the manufacturing method of the present invention, and FIGS. 3 (a) and 3 (b) are shoulder growth steps (shoulders). It is a graph which shows the thermal stress distribution in a crystal | crystallization in a part process. The drawings referred to in the following description are drawings for explaining a silicon single crystal manufacturing method and a silicon single crystal. The size, thickness, dimensions, and the like of each part shown in the drawings are different from actual dimensional relationships. There may be.

  The silicon single crystal manufacturing method of the present embodiment uses a highly volatile resistance adjusting dopant, supplies Ar gas, and grows while pulling up the silicon single crystal 1 from the silicon melt 5 contained in the crucible 4. A shoulder growing step of expanding the silicon single crystal 1 to an ingot having a predetermined diameter, and an ingot grown to a predetermined diameter in the shoulder growing step. A body growth step for growing in a rod shape, and the shoulder growth step is a distance (gap) L1 between the lower end 11a of the gas rectifying cylinder 11 for rectifying the Ar gas and the free liquid surface 51 of the silicon melt 5. Is performed with a thickness exceeding 30 mm.

[Silicon single crystal pulling equipment]
As shown in FIGS. 1 and 2, the silicon single crystal pulling apparatus 30 used in the manufacturing method of the present embodiment includes a crucible 4 in which the silicon melt 5 is put, and a heater arranged concentrically around the crucible 4. 6, a support shaft 7 that supports the crucible 4 from below, and a gas rectifying cylinder 11 provided on the upper side of the crucible 4.

  The crucible 4 has a bottomed cylindrical inner layer holding container 4a made of a material such as quartz, and is similarly formed into a bottomed cylindrical shape and is fitted to the outside of the inner layer holding container 4a to hold an outer layer made of a material such as graphite. It is comprised from the container 4b. The crucible 4 has a lower portion supported by a support shaft 7 and is configured to rotate at a predetermined speed.

As described above, the heater 6 is arranged around the crucible 4 and is arranged concentrically with the crucible 4. The heater 6 heats and melts the silicon melt 5 put in the crucible 4.
As described above, the support shaft 7 is a support member that supports the crucible 4 from below, and rotates the crucible 4 at a predetermined speed by being rotated by a power source such as a motor.

  The gas rectifying cylinder 11 is arranged on the upper side of the crucible 4, in the illustrated example, the lower end 11 a of the gas rectifying cylinder 11 enters the inside from the opening 41 of the crucible 4. Further, the gas flow straightening cylinder 11 is formed in a taper shape whose diameter is reduced from the upper end 11b toward the lower end 11a. With the above configuration, the gas rectifying cylinder 11 rectifies Ar gas supplied into the silicon single crystal pulling apparatus 30 toward the solid-liquid interface between the silicon melt 5 and the silicon single crystal 1 to form a hot zone. .

  In the silicon single crystal pulling apparatus 30 configured as described above, the crucible 4 is filled with the silicon melt 5 melted by the heater 6, and the central axis of the crucible 4 has a pulling rod or a wire. A lifting shaft A consisting of is arranged. A seed chuck 2 and a seed crystal 1a are attached to the tip of the pulling shaft A.

[Growth of silicon single crystal]
Hereinafter, a procedure for manufacturing the ingot-shaped silicon single crystal 1 using the silicon single crystal pulling apparatus 30 configured as shown in FIGS. 1 and 2 will be described.
In the present invention, as shown in FIG. 1, the seed crystal 1 a is brought into contact with the surface of the silicon melt 5 accommodated in the crucible 4, and a predetermined speed in the same direction or in the opposite direction with the same axis as the support shaft 7. The silicon single crystal 1 formed by the solidification of the silicon melt is grown by pulling up the pulling shaft A while rotating at.

  In the present invention, as shown in FIG. 2, first, in the shoulder forming step (shoulder process), the seed crystal 1a is brought into contact with the silicon melt 5 in the crucible 4 and slowly pulled up at a predetermined speed. By pulling up the axis A, the growing silicon single crystal is expanded to a predetermined diameter to form a so-called ingot shoulder 1b. At this time, as shown in FIG. 2, Ar gas for preventing a chemical reaction is supplied into the silicon single crystal pulling apparatus 30, and the vicinity of the solid-liquid interface between the silicon melt 5 and the growing silicon single crystal 1. The crystal growth process is performed while being distributed toward the market.

  Next, following the shoulder growth step, in the trunk growth step, an ingot of the silicon single crystal 1 having the shoulder 1b grown to a predetermined diameter is grown into a rod shape by growing the trunk 1c. Specifically, as in the shoulder growth step, the body 1c of the silicon single crystal 1 is grown by pulling up the pulling shaft A while slowly rotating at a predetermined speed. And the silicon single crystal 1 can be finally obtained as a rod-shaped ingot by growing the silicon single crystal 1 to the target length.

“Distance (gap) L1 between the gas flow straightening cylinder and the free surface of the silicon melt”
The shoulder growth step (shoulder process) provided in the manufacturing method of the present invention is performed by a distance (gap) between the lower end 11a of the gas flow straightening cylinder 11 and the free liquid level 51 of the silicon melt 5 as shown in FIG. ) L1 is set to more than 30 mm. Thus, for example, when a silicon single crystal for semiconductor having a low resistance of 10 mΩcm or less is grown using a highly volatile resistance adjusting dopant such as As, red phosphorus, and Sb, dislocations are formed. Therefore, it is possible to suppress the crystal pulling from the silicon melt many times, shorten the cycle time of crystal growth, and improve the productivity.

  In order to suppress the occurrence of dislocations as described above frequently in the shoulder growth step in which the shoulder is grown to a predetermined diameter in the initial step when growing the silicon single crystal, the present inventors have earnestly studied. A study was conducted. As a result, in the shoulder growth process, by setting the gap between the lower end 11a of the gas flow straightening cylinder 11 and the free liquid surface 51 of the silicon melt 5 to the above dimensions, occurrence of dislocation can be suppressed. It was found that the cycle time of crystal growth can be shortened.

Although the reason why the dislocation of crystals in the shoulder growth step can be reduced by the above configuration is not clear, for example, the following reasons can be considered.
The dislocation formation in the silicon single crystal as described above is considered to occur because very small foreign matters floating on the free liquid surface of the silicon melt are taken into the crystal in the shoulder growth step. Conventionally, the shoulder growth step is usually performed with the gap L1 in the range of about 10 to 30 mm.

Here, as shown in the graph of FIG. 3A, it can be seen that when the gap L1 is 20 mm, the thermal stress in the vicinity of the solid-liquid interface between the silicon single crystal and the silicon melt is high.
On the other hand, as shown in the graph of FIG. 3B, when the gap L1 is 50 mm, the thermal stress in the vicinity of the solid-liquid interface between the silicon single crystal 1 and the silicon melt 5 is greatly reduced. Is possible. Thus, even if very small foreign matter is taken into the silicon crystal, it is considered that dislocation does not occur.
Thus, by setting the gap L1 between the lower end 11a of the gas flow straightening cylinder 11 and the free liquid surface 51 of the silicon melt 5 to a large size, specifically, more than 30 mm, the thermal stress near the solid-liquid interface is greatly reduced. It becomes possible to do.

  Further, in the manufacturing method of the present invention, the gap L1 between the lower end 11a of the gas flow straightening cylinder 11 and the free liquid level 51 of the silicon melt 5 in the shoulder growth step as shown in FIG. It is more preferable that the distance is larger than the gap L2 in the trunk growth step. Thus, the gaps L1 and L2 between the lower end 11a of the gas flow straightening cylinder 11 and the free liquid surface 51 of the silicon melt 5 are expressed as “(gap L1 in the shoulder growth process)> (gap L2 in the trunk growth process). ) ”, The following effects can be obtained.

  First, in the shoulder growth process, since dislocations are suppressed in the shoulder 1b of the silicon single crystal 1 to be grown, the redrawing process of the crystal pulling is reduced, and the manufacturing cycle time in the shoulder growth process can be shortened. . On the other hand, in the trunk growth step, the melt temperature gradient in the direction perpendicular to the solid-liquid interface between the silicon single crystal 1 and the silicon melt 5 can be increased, so even if the dopant concentration increases, Overcooling can be prevented, and dislocation formation in the body 1c of the silicon single crystal 1 to be grown is suppressed. Thereby, since the manufacturing cycle time can be shortened similarly to the above, it becomes possible to manufacture a silicon single crystal with high production efficiency.

"Process Conditions"
As each process condition in the manufacturing method of this invention, it is possible to apply the condition generally used as a process condition of a silicon single crystal conventionally without any limitation.
Since the present invention is basically a method of reducing the thermal stress generated in the crystal by increasing the gap L1 in the shoulder growth step and reducing dislocations, other process conditions are conventionally known. The same conditions can be used. That is, as each process condition in the shoulder growth step, the crystal rotation speed during growth is appropriately set in the range of 0 to 30 rpm, the crucible rotation speed is 0 to 30 rpm, and the pulling speed is in the range of 0.1 to 3 mm / min. Is possible.

"Occurrence of foreign matter"
In the manufacturing process of a low resistance silicon single crystal for semiconductor using a highly volatile resistance adjusting dopant, the shoulder was formed under the same conditions as in the manufacturing process using a volatile dopant. Even in the case where the non-volatile dopant is used, the frequency of dislocation tends to be smaller. Such a difference is largely related to whether or not the dopant is volatilized. When a volatile dopant is used, it is considered that foreign substances related to the volatile dopant are floating on the free surface of the silicon melt. It is done. This can be explained as follows.

  Volatile dopants are evaporated from the free surface of the silicon melt. As a result of intensive studies by the present inventors using numerical simulation, it is clear that circulating flows R1 and R2 as shown in FIG. 2 are formed on the free liquid surface of the silicon melt. Here, the evaporated dopant or its reactant is trapped in the circulating flow R2 and once transported to the upper part of the furnace. However, since the temperature of the upper part of the furnace is low, the evaporated dopant or the reaction product thereof aggregates, and it is considered that these fall down and float as foreign matters on the free liquid surface of the silicon melt.

  On the other hand, in the manufacturing method of the present invention, the shoulder growth step is performed with the distance (gap) L1 between the lower end 11a of the gas flow straightening cylinder 11 and the free liquid surface 51 of the silicon melt 5 exceeding 30 mm. The evaporated dopant or its reactant is carried along the circulating flow R1 in FIG. For this reason, it is considered that the evaporated dopant or its reaction product does not go to the upper part of the furnace but goes to the lower part of the furnace and does not float as a foreign substance on the free liquid surface 51 of the silicon melt 5. Therefore, in the manufacturing method of the present invention, the occurrence of dislocations frequently is suppressed in the shoulder forming step, so that the crystal pulling from the silicon melt is not repeated again and the cycle time of crystal growth is shortened. It is considered possible.

  As described above, according to the method for producing a silicon single crystal of the present invention, a silicon single crystal for a semiconductor having a low resistance of 10 mΩcm or less using a highly volatile dopant for resistance adjustment with the above configuration. Dislocations in the shoulder growth step when growing 1 can be suppressed. Thereby, in the shoulder growth process, the crystal pulling from the silicon melt 5 is prevented from being repeated again and again, and the manufacturing cycle time can be shortened, so that the silicon single crystal 1 is manufactured with high production efficiency. Is possible.

  Further, by setting the gap L1 between the lower end 11a of the gas flow straightening cylinder 11 and the free liquid surface 51 of the silicon melt 5 in the shoulder growth process to be larger than the gap L2 in the trunk growth process, In the growth process, dislocations at the shoulder of the silicon single crystal to be grown are suppressed. As a result, the redrawing process of crystal pulling in the shoulder growth process is reduced, and the manufacturing cycle time in the shoulder growth process can be shortened. On the other hand, in the trunk growth step, the melt temperature gradient in the direction perpendicular to the solid-liquid interface between the silicon single crystal and the one silicon melt 5 can be increased, so even if the dopant concentration increases, Overcooling can be prevented, and dislocation formation in the body 1c of the silicon single crystal 1 to be grown is suppressed. Therefore, the manufacturing cycle time can be shortened, and a silicon single crystal can be manufactured with high production efficiency.

  Moreover, since the silicon single crystal of the present invention is obtained by the production method of the present invention, the crystal quality is excellent and the cost is low.

  Examples Hereinafter, the method for producing a silicon single crystal and the silicon single crystal of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[Experimental Example 1]
A single crystal pulling apparatus 30 shown in FIGS. 1 and 2 is used to grow a plurality of silicon single crystals by bringing the seed crystal 1a into contact with the surface of the silicon melt 5 accommodated in the crucible 4 and pulling up the pulling shaft A. I let you.
The pulling conditions at this time were a charge amount of 120 kg, a pulling diameter of 210 mm, and 900 g of As as a dopant. Further, the pulling speed was set in the range of 0.5 to 0.9 mm / min, the crystal (seed) rotation speed was changed in the range of 8 rpm to 14 rpm, and the crucible rotation speed was changed in the range of 6 rpm to 10 rpm. Moreover, the nuclear conditions were adjusted so that the shape of the shoulder portion was the same, and the pulling process was performed in a total of 5 batches, and the number of dislocations in the shoulder formation step was investigated.

In this experimental example, since a volatile dopant is used, the dopant evaporates over time, and the dopant concentration in the silicon melt decreases. For this reason, when dislocations are generated, the crystals are dissolved, and the dip process is started again. However, according to the elapsed time, the evaporated amount of dopant is re-doped and pulled up.
Furthermore, in the manufacturing process, the gap L1 between the lower end 11a of the gas flow straightening cylinder 11 and the free liquid level 51 of the silicon melt 5 in the shoulder growth step is appropriately changed to the dimensions shown in Table 1 below. The crystal was grown.
The results are shown in Table 1 below.

  As shown in Table 1, dislocations in the shoulder growth step are achieved by setting the gap L1 between the lower end 11a of the gas flow straightening cylinder 11 in the shoulder growth step and the free liquid surface 51 of the silicon melt 5 to be greater than 30 mm. It is clear that the occurrence of crystallization can be reduced.

[Experiment 2]
Similar to Experimental Example 1, by using the single crystal pulling apparatus 30 shown in FIGS. 1 and 2, the seed crystal 1a is brought into contact with the surface of the silicon melt 5 accommodated in the crucible 4 and the pulling shaft A is lifted. A plurality of silicon single crystals were grown.
The pulling conditions at this time were a charge amount of 120 kg, a pulling diameter of 210 mm, and 1200 g of As as a dopant. Further, the pulling speed was set in the range of 0.5 to 0.9 mm / min, the crystal (seed) rotation speed was changed in the range of 8 rpm to 14 rpm, and the crucible rotation speed was changed in the range of 6 rpm to 10 rpm. Moreover, the nuclear conditions were adjusted so that the shape of the shoulder portion was the same, and the pulling process was performed in a total of 5 batches, and the number of dislocations in the shoulder formation step was investigated.

Moreover, since a volatile dopant is used like the said Experimental example 1, a dopant evaporates with time passage and the dopant density | concentration in a silicon melt falls. For this reason, when dislocations are generated, the crystals are dissolved, and the dip process is started again. However, according to the elapsed time, the evaporated amount of dopant is re-doped and pulled up.
Further, as in the above experimental example 1, the gap L1 between the lower end 11a of the gas flow straightening cylinder 11 and the free liquid level 51 of the silicon melt 5 in the shoulder growth process is appropriately changed in the dimensions shown in Table 2 below. Crystal growth was performed.
The results are shown in Table 2 below.

  As shown in Table 2, dislocations in the shoulder growth step are achieved by setting the gap L1 between the lower end 11a of the gas flow straightening cylinder 11 in the shoulder growth step and the free liquid surface 51 of the silicon melt 5 to be greater than 30 mm. It is clear that the occurrence of crystallization can be reduced.

It is a figure which illustrates typically an example of the manufacturing method of the silicon single crystal of this invention, and is a schematic sectional drawing which shows an example of the single crystal pulling apparatus used in this invention. It is a figure which illustrates typically an example of the manufacturing method of the silicon single crystal of this invention, and is a schematic sectional drawing which shows an example of the single crystal pulling apparatus used in this invention. It is a figure which illustrates typically an example of the manufacturing method of the silicon single crystal of this invention, and is a graph which shows the thermal stress distribution in a crystal | crystallization in a shoulder part growth process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Silicon single crystal (ingot), 1b ... Shoulder part, 1c ... Trunk part, 4 ... Crucible, 5 ... Silicon melt, 51 ... Free liquid surface (silicon melt), 11 ... Gas rectifier cylinder, L1, L2 ... The distance (gap) between the lower end of the gas flow straightening tube and the free surface of the silicon melt

Claims (1)

Production of a silicon single crystal using a highly volatile dopant for resistance adjustment, supplying Ar gas, and growing a silicon single crystal having a resistivity of 10 mΩcm or less from a silicon melt contained in a crucible while pulling it up A method,
A shoulder growth step for expanding the silicon single crystal to an ingot having a predetermined diameter; and a trunk growth step for growing the ingot grown to a predetermined diameter in the shoulder growth step into a rod shape.
In the shoulder growth step, the distance between the lower end of the gas rectifying cylinder for rectifying the Ar gas and the free surface of the silicon melt is reduced to 35 mm or more and 160 mm so as to reduce the thermal stress generated in the crystal. A method for producing a silicon single crystal, wherein the distance is larger than the distance in the trunk growth step.

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