JP2020055718A - Method for supplying raw material and method for manufacturing silicon single crystal - Google Patents

Abstract

To provide a method for supplying a raw material, capable of appropriately charging the raw material without damaging a quartz crucible.SOLUTION: The method for supplying a raw material comprises: the solidification step of controlling heater power for heating a quartz crucible to solidify the surface of a silicon melt; the dropping step of dropping a solid raw material into a solidification portion of the surface; and the melting step of melting the solidification portion and the solid raw material. The solidification step controls the heater power in the solidification step on the basis of the value of the heater power when performing the dipping step of dipping a seed crystal in a silicon melt when a conventional silicon single crystal is manufactured.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a raw material supply method and a method for producing a silicon single crystal.

Conventionally, when continuously producing a plurality of silicon single crystals by the CZ (Czochralski) method, a method of recharging a solid raw material for producing a second or subsequent silicon single crystal into a silicon melt in a crucible is known. (For example, see Patent Document 1).
The method of Patent Document 1 includes a step of solidifying the surface of the silicon melt before dropping the solid raw material into the silicon melt. In the solidifying step, the power of the heater for heating the crucible is set such that the time until the region corresponding to 80% of the entire surface of the silicon melt solidifies and the inner diameter of the crucible satisfy a predetermined relationship. ing.

JP 2007-246356 A

  However, in the method described in Patent Document 1, the solidification of the surface of the silicon melt proceeds more than expected, and for example, when the solid material is dropped, the solidified portion sinks, which may damage the quartz crucible. There is. In addition, solidification of the surface of the silicon melt may not proceed more than expected, and the time of the solidification step may be lengthened.

  An object of the present invention is to provide a method of supplying a raw material and a method of manufacturing a silicon single crystal that can appropriately charge a quartz crucible without damaging the quartz crucible.

The raw material supply method of the present invention is a raw material supply method for charging a solid raw material to a silicon melt in the quartz crucible when producing a silicon single crystal using one quartz crucible by the Czochralski method, Adjusting the power of a heater for heating the quartz crucible to solidify the surface of the silicon melt; dropping the solid material onto a solidified portion of the surface; and solidifying the solid material and the solid material. A solidifying step, during the production of a conventional silicon single crystal, the value of the power of the heater when performing a liquid contacting step of contacting the seed crystal to the silicon melt. On the basis of this, the power of the heater in the solidification step is adjusted.
The “power of the heater when the step of dipping the seed crystal into the silicon melt” means the power after dipping the seed crystal and immediately before pulling up (for example, one second before pulling up). When the power is adjusted after the liquid is applied and before the liquid is pulled up, the power after the adjustment is meant.

  In the raw material supply method of the present invention, the dropping step adjusts the power of the heater in the dropping step based on a value of the power of the heater at the time of performing the liquid contacting step in the production of the conventional silicon single crystal. Is preferred.

  In the raw material supply method of the present invention, the melting step adjusts the power of the heater in the melting step based on the value of the power of the heater when the liquid contacting step in the production of the conventional silicon single crystal is performed. Is preferred.

  In the raw material supply method of the present invention, in the solidifying step, when the power of the heater when the liquid contacting step is performed is larger than a liquid contacting step reference value, the power of the heater in the solidifying step is set to be larger than the solidifying step reference value. Is also preferably increased.

  In the raw material supply method of the present invention, in the solidifying step, when the power of the heater at the time of performing the liquid contacting step is smaller than the liquid contacting step reference value, the power of the heater in the solidifying step is set to be smaller than the solidifying step reference value. Is also preferably reduced.

In the raw material supply method of the present invention, it is preferable that the solidifying step adjusts the power of the heater based on the following equation (1).
A = B−α × (C−D) (1)
A: power of heater after adjustment B: reference value of solidification process C: reference value of immersion process D: power of heater when the above-mentioned immersion process is performed α: parameter for adjustment Note that the reference value of solidification process B is This is the value of the power of the heater such that the solidification rate of the silicon melt surface becomes the target value. The liquid contacting process reference value C is the “power of the heater when the step of contacting the seed crystal with the silicon melt” is performed in the single crystal pulling apparatus in which the solidification rate of the silicon melt surface becomes the target value. This means the power after the seed crystal is immersed and immediately before it is pulled up (for example, one second before it is pulled up). When the heater power is adjusted after the liquid is applied and before the liquid is pulled up, the adjusted heater power means the adjusted heater power. That is, the liquid contacting process reference value C is equivalent to the power D of the heater when the liquid contacting step is performed in the single crystal pulling device in which the solidification speed is the target value, and in the single crystal pulling device in which the solidification speed is the target value. Is (DC) = 0.
The adjustment parameter α is a positive value close to 1. Specifically, it can be a value within the range of 0 <α ≦ 2. By using the adjustment parameter α, power adjustment can be performed according to the characteristics of each single crystal pulling apparatus.

  In the raw material supply method of the present invention, the solidification step, the dropping step, and the melting step are each repeatedly performed twice or more the same number of times, and the solidification step reference value is increased as the number of times of the repetition increases. Preferably, it is set to a small value.

  The method for producing a silicon single crystal according to the present invention is a method for producing a silicon single crystal by continuously producing a plurality of silicon single crystals by using one quartz crucible by the Czochralski method, wherein a silicon melt is used as a seed crystal. And a growing step of pulling up the seed crystal to grow a silicon single crystal, and recharging a solid raw material for producing the second and subsequent silicon single crystals to a silicon melt in a quartz crucible. A recharging step of performing the above-described raw material supply method, wherein the solidification step in the recharging step is performed when the liquid contacting step is performed during the production of any silicon single crystal using the same quartz crucible. The power of the heater in the solidification process is adjusted based on the value of the power of the heater.

  In the method for producing a silicon single crystal of the present invention, an initial melt generation step of heating a quartz crucible containing a solid raw material to generate a silicon melt, and using the above-described raw material supply method, An additional charging step of additionally charging the silicon melt in the quartz crucible, wherein the solidifying step in the additional charging step performs the liquid contacting step at the time of producing a silicon single crystal immediately before using another quartz crucible. It is preferable to adjust the power of the heater in the solidification step based on the value of the power of the heater at that time.

  The method for producing a silicon single crystal of the present invention is a method for producing one silicon single crystal using one quartz crucible by the Czochralski method, wherein the quartz containing a solid raw material is contained. An initial melt generating step of heating the crucible to generate a silicon melt; an additional charging step of additionally charging a solid raw material to the silicon melt in the quartz crucible using the above-described raw material supply method; And a growing step of growing the silicon single crystal by pulling up the seed crystal, wherein the solidifying step in the additional charging step is performed immediately before using another quartz crucible. The method is characterized in that the power of the heater in the solidification step is adjusted based on the value of the power of the heater when the liquid contacting step is performed during the production of the silicon single crystal.

  In the method for producing a silicon single crystal of the present invention, a liquid-adhesion power adjusting step of adjusting the power of the heater so that the temperature of the silicon melt becomes a predetermined temperature between the liquid-immersion step and the growing step. Preferably, it is provided.

  According to the present invention described above, it is possible to provide a method for supplying a raw material and a method for manufacturing a silicon single crystal, which can appropriately charge a quartz crucible without damaging the quartz crucible.

FIG. 1 is a schematic view of a single crystal pulling apparatus according to a related art and an embodiment of the present invention. 5 is a flowchart of a method for manufacturing a silicon single crystal in the related art. It is a schematic diagram which shows the state of the said related art, the recharge in 1st Embodiment, and the additional charge in 2nd Embodiment, (A) shows a solidification process and (B) shows a dropping process. 4 is a graph showing the relationship between the adjustment value of the heater power when the seed crystal is immersed and the solidification rate of the silicon melt, which are results of an experiment conducted to guide the present invention. 3 is a flowchart of a method for manufacturing a silicon single crystal according to the first embodiment. 9 is a flowchart of a method for manufacturing a silicon single crystal according to the second embodiment. 4 is a graph showing the variation in the solidification rate of Comparative Example 1 and Example 1 in the example of the present invention. 4 is a graph showing a variation in solidification rate between Comparative Example 2 and Example 2 in the above example.

[Related Art of the Present Invention]
First, the related art of the present invention will be described with reference to the drawings.
[Structure of single crystal pulling device]
As shown in FIG. 1, the single crystal pulling apparatus 1 is an apparatus used for the CZ method (Czochralski method), and includes a pulling apparatus main body 2, a memory 3, and a control unit 4.
The lifting device main body 2 includes a chamber 21, a crucible 22 disposed in the chamber 21, a heater 23 for heating the crucible 22, a lifting unit 24, a heat shield 25, a heat insulator 26, And a part 27.
The single crystal pulling apparatus 1 is an apparatus used for an MCZ (Magnetic field applied Czochralski) method, as indicated by a two-dot chain line, and has a pair of electromagnetic coils disposed outside a chamber 21 with a crucible 22 interposed therebetween. 28 may be provided.

  The chamber 21 includes a main chamber 211 and a pull chamber 213 connected to the upper part of the main chamber 211 via a gate valve 212. The pull chamber 213 is provided with a gas inlet 21A for introducing an inert gas such as Ar gas into the main chamber 211. A gas exhaust port 21 </ b> B that exhausts gas in the main chamber 211 is provided below the main chamber 211.

  The crucible 22 is for melting a solid raw material S (see FIG. 3B) into a silicon melt M. The crucible 22 includes a quartz crucible 221 and a graphite crucible 222 that accommodates the quartz crucible 221. The quartz crucible 221 is replaced every time one or a plurality of silicon single crystals SM are grown. On the other hand, the graphite crucible 222 is not replaced every time one silicon single crystal SM is manufactured, but is replaced when it is considered that the quartz crucible 221 cannot be properly supported.

The heater 23 is arranged around the crucible 22 and melts silicon in the crucible 22. Note that a bottom heater 231 as shown by a two-dot chain line may be further provided below the crucible 22.
The pulling unit 24 includes a cable 241 to which the seed crystal SC is attached at one end, and a pulling drive unit 242 that moves the cable 241 up and down and rotates.
The heat shield 25 is provided so as to surround the silicon single crystal SM, and blocks radiant heat radiated upward from the heater 23.
The crucible driving unit 27 includes a support shaft 271 that supports the graphite crucible 222 from below, and rotates and moves up and down the crucible 22 at a predetermined speed.
The hot zones in the single crystal pulling apparatus 1 are the chamber 21, the crucible 22, the heater 23, the cable 241, the heat shield 25, the heat insulating material 26, the support shaft 271, the silicon melt M, the silicon single crystal SM, and the like.

The memory 3 stores various information necessary for manufacturing the silicon single crystal SM, such as the gas flow rate in the chamber 21, the furnace pressure, the electric power supplied to the heater 23, the rotation speed of the crucible 22 and the silicon single crystal SM.
The control unit 4 manufactures the silicon single crystal SM based on various information stored in the memory 3 and an operation of an operator.

[Production method of silicon single crystal]
Next, a method of manufacturing the silicon single crystal SM by the multi-pulling method will be described. The multi-pulling method is a method of continuously manufacturing a plurality of silicon single crystals SM using one quartz crucible 221.
First, as shown in FIG. 2, the seed crystal SC is immersed in the silicon melt M stored in the crucible 22 (step S1: immersion step).
Next, the control unit 4 raises the seed crystal SC to grow the silicon single crystal SM (Step S2: growing step). The growing step includes raising the seed crystal SC and raising the crucible 22 while rotating the crucible 22 (pulling step), separating the tail portion of the silicon single crystal SM from the silicon melt M (separating step), A step of cooling while pulling up the silicon single crystal SM separated from the liquid M (cooling step), a step of closing the gate valve 212 when the cooled silicon single crystal SM is stored in the pull chamber 213 (closing step), 213 for taking out the silicon single crystal SM (take-out step).

After or during the growing step, the control unit 4 determines whether or not to grow the next silicon single crystal SM (step S3).
In step S3, when the control unit 4 determines that the growth of the predetermined number of silicon single crystals SM is completed and determines that the next growth is not performed, the control unit 4 ends the process. On the other hand, in step S3, when the growth of the predetermined number of silicon single crystals SM is not completed and it is determined that the next growth is to be performed, the control unit 4 sets the power of the heater 23 to the predetermined value. The surface of the silicon melt M is solidified by setting a solidification process reference value (Step S4: solidification process). By this solidification step, as shown in FIG. 3A, the entire surface of the silicon melt M is solidified to form a solidified portion M1. As a target value of the solidification rate, a value of 14 mm / min or more and 20 mm / min or less can be exemplified as a result of experiments so far, and a preferable value is 17 mm / min.

Thereafter, as shown by a solid line in FIG. 3A, the control unit 4 forms the solidified portion M1 having an appropriate diameter and thickness, as shown in FIG. 3B, on the solidified portion M1. The solid raw material S is dropped (step S5: dropping step). In this dropping step, the control unit 4 sets the power of the heater 23 to a dropping step reference value larger than the solidification step reference value to suppress the solidification, and then uses the raw material supply device 5 to feed the solid raw material S in a chunk tube manner. Drop. The raw material supply device 5 lowers the cylindrical quartz tube 51 called a chunk tube filled with the solid raw material S onto the solidified portion M1, and then attaches the bottom cover attached to the lower end opening of the quartz tube 51. The solid raw material S is dropped onto the solidified portion M1 by moving 52 downward and opening the lower end opening of the quartz tube 51.
The transition from the solidifying step to the dropping step may be performed based on a result of a visual check by an operator or a result of photographing by the photographing means.

Thereafter, when the dropping of the solid raw material S is completed, the power of the heater 23 is set to the same melting process reference value as the dropping process reference value, that is, the step of melting the solid raw material S while maintaining the power (step S6: (Melting step).
Next, when the melting of the solid raw material S is completed, the control unit 4 determines whether or not to end the recharging (Step S7).
In step S7, when the controller 4 determines that the dropping process is performed a preset number of times and ends the recharge, the process returns to step S1 and starts the production of the next silicon single crystal SM.
On the other hand, if it is determined in step S5 that the dropping process has not been performed the preset number of times and the recharge is to be continued, the process returns to step S4.
Through the above processing, a plurality of silicon single crystals SM are continuously manufactured.

[History leading to the present invention]
The inventor has earnestly studied and obtained the following findings.
The heat retaining property of the single crystal pulling apparatus 1 may be different depending on the tolerance or deterioration of the shape or arrangement of the components of the hot zone. Examples of the components of the hot zone include a chamber 21, a crucible 22, a heater 23, a cable 241, a heat shield 25, a heat insulating material 26, a support shaft 271, a silicon melt M, and a silicon single crystal SM.
The inventor of the present invention has found that such a change in the heat retaining property of the single crystal pulling apparatus 1 also changes the progress of solidification of the surface of the silicon melt M, causing unexpected damage to the quartz crucible 221 or preventing the solidification process from being performed. It was estimated that the time could be longer.
Therefore, the following experiment was performed.

First, using the above-described single crystal pulling apparatus 1, the power of the heater 23 was set to the liquid deposition step reference value, and then the seed crystal SC was immersed in the silicon melt M. As the liquid-contacting step reference value, for example, an average value of the power in the liquid-contacting step performed in the past can be exemplified, but a value set by another reference may be used. For example, the relationship between “adjustment value of heater power when seed crystal SC is immersed” and “solidification rate of silicon melt M” as shown in FIG. It is possible to use the heater power when the seed crystal SC is immersed when the solidification speed reaches the target value.
Then, the power of the heater 23 was adjusted based on the state after the seed crystal SC was immersed. In this adjustment, the power was increased when the temperature of the silicon melt M was lower than expected due to the low heat retention of the single crystal pulling apparatus 1 and the growth was likely to proceed quickly. On the other hand, when the temperature of the silicon melt M is higher than expected because the single crystal pulling apparatus 1 has high heat retention, the power is reduced when the seed crystal SC is likely to be melted in the silicon melt M. Further, when the heat retaining property of the single crystal pulling apparatus 1 was within a predetermined range and the growing process could be performed appropriately, the power was maintained.
Thereafter, the processes of steps S3, S4, S5, S6, and S7 shown in FIG. 2 are performed to manufacture a plurality of silicon single crystals SM, and a solidification process after manufacturing the first silicon single crystal SM (hereinafter, referred to as “first solidification”). Solidification rate in the “process”).

Thereafter, a similar experiment was performed using a different single crystal pulling apparatus 1 to confirm the relationship between the power adjustment value at the time of liquid contact and the solidification rate in the first solidification step. In all the experiments, the solidification, dropping, and melting step reference values in the first solidification, dropping step, and melting step were set to the same value.
FIG. 4 shows the relationship between the adjusted value of the power at the time of liquid contact and the solidification rate of the silicon melt M. The horizontal axis of FIG. 4 shows the ratio of the power adjustment value based on the liquid landing process reference value.

  As shown by the approximate line L in FIG. 4, it was confirmed that the solidification rate of the silicon melt M was increased as the power adjustment value at the time of liquid landing was increased. This result indicates that when the adjusted value of the power at the time of liquid contact is large and the heat retaining property of the single crystal pulling apparatus 1 is low, the solidification rate in the solidification step is increased, the adjusted value of the power is small, and the single crystal pulling apparatus 1 It is considered that when the heat retention is high, it indicates that the solidification rate is low.

From the above, it is possible to estimate the heat retention of the single crystal pulling apparatus 1 by adjusting the power of the heater 23 at the time of liquid contact, and to adjust the power of the heater 23 during the solidification, dropping, and melting steps based on the estimation result. Thus, it is considered that the surface of the silicon melt M can be appropriately solidified and the recharge can be appropriately performed.
For example, when the power at the time of the liquid landing is larger than the reference value of the liquid landing step, the power at the time of the solidification, dropping and melting step is made larger than the reference value of the solidification, dropping and melting step.
By setting the power in the solidification step to be larger than the solidification step reference value, the solidification rate can be reduced, and a problem caused by the solidification rate being too fast, for example, solidification proceeds more than expected and the quartz crucible 221 is damaged It can be considered that the problem of performing the operation can be suppressed.
Further, by making the power in the dropping process larger than the reference value in the dropping process, it is possible to suppress the temperature drop of the solidified portion M1 when the solid raw material S is dropped, and the solidified portion M1 becomes large or thick. It is considered that the problem of causing the quartz crucible 221 to be damaged can be suppressed.
Further, by setting the power at the time of the melting step to be higher than the reference value of the melting step, the temperature of the melt at the time of completion of the melting step can be increased, and the solidification rate at the time of charging the next raw material can be set to the target value (for example, 14 mm / min or more).

On the other hand, when the power at the time of the liquid landing is smaller than the reference value of the liquid landing step, the power at the time of the solidification, dropping and melting step is made smaller than the reference value of the solidification, dropping and melting step. By setting the power during the solidification process to be smaller than the solidification process reference value, the solidification speed can be increased, and a problem caused by the solidification speed being too slow, for example, solidification does not proceed more than expected, and the solidification process takes a long time It can be considered that the problem of becoming irrelevant can be suppressed.
Further, by making the power at the time of the dropping step smaller than the reference value of the dropping step, the melting rate of the solidified portion M1 can be reduced, and the solid material S can be prevented from being directly dropped into the silicon melt M, It is considered that the silicon melt M can be prevented from scattering.
Further, by making the power at the time of the melting step smaller than the reference value of the melting step, the melt temperature at the time of completion of the melting step can be lowered, and the solidification rate at the time of charging the next raw material is set to the target value (for example, 20 mm / min or less).

[First Embodiment]
Next, a method of manufacturing the silicon single crystal SM by the multi-pulling method according to the first embodiment of the present invention will be described. In the manufacturing method described in the first embodiment and a second embodiment described below, the silicon single crystal SM may have a diameter of a straight body after cylindrical grinding of 200 mm, 300 mm, 450 mm, or another size. Further, a dopant for adjusting the resistivity may or may not be added to the silicon melt M.
In the first embodiment, steps different from the manufacturing method of the related art shown in FIG. 2 will be described in detail, and the same steps will be denoted by the same reference numerals and the description will be simplified. Steps S12, S4, S5, S6, and S7 of the following steps correspond to the recharging step using the material supply method of the present invention.

  First, as shown in FIG. 5, the seed crystal SC is immersed in the silicon melt M (step S1: immersion step). In the liquid-contacting step, the control section 4 sets the power of the heater 23 to the liquid-contacting step reference value, and then immerses the seed crystal SC into the silicon melt M.

  Thereafter, the control unit 4 adjusts the power of the heater 23 based on the state after the seed crystal SC is immersed in order to appropriately perform the growing step (Step S11: liquid immersion power adjusting step). In the liquid landing power adjustment step, as described in the above-described process leading to the present invention, when the heat retaining property of the single crystal pulling apparatus 1 is low based on the state of the seed crystal SC, the power is increased, When the heat retention is high, the power is reduced, and when the heat retention is within a predetermined range, the power is maintained. By this adjustment, the temperature of the silicon melt M immediately before the lifting step can be set to a predetermined temperature.

Next, the control unit 4 pulls up the seed crystal SC and grows the silicon single crystal SM (step S2: growing step). After the growing step is completed or during execution, the control unit 4 sets the next silicon single crystal SM. It is determined whether or not to grow (step S3).
In step S3, when determining that the next growth is not to be performed, the control unit 4 terminates the process, and when determining that the next growth is to be performed, grows the silicon single crystal SM using the same quartz crucible 221. The power of the heater 23 is set based on the power of the heater 23 at the time of the liquid landing (step S12: solidification power, dropping power, and melting power setting step based on the power at the time of liquid landing).
In the setting step of the solidification power, the dropping power, and the melting power, the control unit 4 calculates the power A (kW) of the heater 23 after the setting based on the following equation (1) where the adjustment parameter α is 1.
A = B-α × (CD)
= B-1 × (CD) (1)
B: Solidification, dropping, melting process standard value (kW)
C: Standard value of immersion process (kW)
D: Power (kW) of heater 23 after adjustment in liquid contact power adjustment step

At this time, the control unit 4 calculates the respective powers A of the solidification step, the dropping step, and the melting step by substituting the solidification, injection, and melting step reference values shown in Table 1 below into B in Equation (1). I do. In order to solidify the surface of the silicon melt M, the solidification process reference value in Table 1 is smaller than the power P (kW) that is the dropping process reference value and the melting process reference value (for example, the number of times of dropping is the first time). The solidification process reference value B at this time is set to 0.5 times the power P). Further, the solidification step reference value B is set to be smaller as the number of times of repeating the steps from the solidification step to the melting step increases. Further, since the power P varies depending on the heat retention of the single crystal pulling apparatus 1, the power P is adjusted so as to be the solidification rate target value of 14 mm / min to 20 mm / min. For example, when the power P after adjustment for the single crystal pulling apparatus 1 having a certain structure is 100 kW, the solidification process reference value B for the first dropping number is 50 kW, and the dropping and melting process reference value B is 100 kW.
The power A obtained based on the formula (1) is solidified when the single crystal pulling apparatus 1 has low heat retention and the power D of the heater 23 after the adjustment in the liquid landing power adjustment step is larger than the liquid deposition step reference value C. When the heat retention of the single crystal pulling apparatus 1 is high, it becomes smaller than the solidification, dropping and melting process reference value B.

Thereafter, the control unit 4 adjusts the power of the heater 23 to the power A set in step S12 based on the solidification process reference value, and solidifies the surface of the silicon melt M (step S4: solidification process). As shown in FIG. 3A, a solidified portion M1 is formed in the silicon melt M.
At this time, even if the heat retention of the single crystal pulling apparatus 1 is low and the solidification rate is likely to be high, the solidification rate is too high because the solidification step is performed with a power A larger than the solidification step reference value B. Can be suppressed. Therefore, as shown by a two-dot chain line in FIG. 3A, before the solidified portion M1 becomes too thick, it is possible to easily shift to a charging step described later. As a result, it is possible to prevent the thick solidified portion M1 from sinking due to the drop of the solid raw material S, and from damaging or damaging the quartz crucible 221.
On the other hand, even in the condition where the single crystal pulling apparatus 1 has a high heat retaining property and the solidification rate is likely to be slow, the solidification step is performed with a power A smaller than the solidification step reference value B, so that the solidification rate is prevented from becoming too slow. it can. Therefore, it is possible to suppress the time of the solidification step from becoming too long.

Thereafter, when the solidified portion M1 having an appropriate diameter and thickness is formed, the control unit 4 adjusts the power of the heater 23 to the power A set in step S12 based on the reference value of the dropping process, and adjusts the power on the solidified portion M1. (Step S5: dropping step).
At this time, the dropping process is performed with the power A larger than the dropping process reference value B even under the condition that the heat retaining property of the single crystal pulling apparatus 1 is low and the temperature of the solidified portion when the solid raw material is dropped is easily lowered. In addition, it is possible to prevent the solidified portion M1 from becoming large or thick, and from damaging or damaging the quartz crucible 221.
On the other hand, even when the single crystal pulling apparatus 1 has a high heat retaining property and the solidified portion M1 is easily melted, the dropping process is performed with the power A smaller than the dropping process reference value B. The raw material S can be prevented from being directly dropped into the silicon melt M, and the silicon melt M can be prevented from scattering.
Note that the transition from the solidification step to the dropping step may be performed based on the result of a visual check by an operator or the result of photographing by the photographing means. Irrespective of the heat retention, the dispersion of the temperature of the silicon melt M in the solidification step is reduced, and the dispersion of the time until the solidified portion M1 reaches a desired thickness is also reduced. It may be performed after a lapse of time.

Thereafter, when the dropping of the solid raw material S is completed, the power of the heater 23 is adjusted to the power A set in step S12 based on the melting process reference value, that is, the solid raw material S is maintained while the power of the heater 23 is maintained. The process proceeds to the melting step (Step S6: melting step).
At this time, even when the single crystal pulling apparatus 1 has low heat retention and the solidified portion M1 is hardly melted, the melting step is performed with the power A larger than the melting step reference value B, so that the time of the melting step becomes longer. The problem described above can be suppressed. Furthermore, the temperature of the melt at the time of completion of the melting step can be increased, and the solidification rate at the time of charging the next raw material can be adjusted to a target value (for example, 14 mm / min or more).
On the other hand, even when the single crystal pulling apparatus 1 has a high heat retaining property and the solidified portion M1 is easily melted, the melting step is performed with a power A smaller than the melting step reference value B. Can be lowered, and the solidification speed at the time of charging the next raw material can be adjusted to a target value (for example, 20 mm / min or less).

Next, when the melting of the solid raw material S is completed, the control unit 4 determines whether or not to end the recharging (step S7), and executes a predetermined number of times, in this embodiment, four dropping steps. If it is determined that recharging is to be ended, the process returns to step S1 to start manufacturing the next silicon single crystal SM.
On the other hand, when it is determined in step S7 that recharging is to be continued, the process returns to step S12, and the power A of the heater 23 in the solidification step, dropping step, and melting step is set. In the processing of step S12 for the second and subsequent times, the control unit 4 calculates the solidification, dropping, and melting step reference value B according to the number of repetitions of the steps from the solidification step to the melting step based on the settings in Table 1 according to the formula (1). ) To set the power A.

  Here, as shown in Table 1, the solidification step reference value preferably decreases as the number of repetitions of the steps from the solidification step to the melting step increases. If the solidification step reference value is set to the same value regardless of the number of repetitions, the more the number of repetitions increases, the more the silicon melt M increases, and the higher the heat retention of the crucible 22 becomes. As a result, the power obtained based on the equation (1) becomes larger than the appropriate power, and there is a possibility that a problem may occur due to the solidification speed being too slow. By reducing the solidification step reference value as the number of repetitions increases as in the present embodiment, the power obtained based on Expression (1) can be made substantially the same as the appropriate power, and the solidification speed is too slow. Can be suppressed.

  In the processing of step S12 for the second and subsequent times, the value obtained in the liquid contacting power adjustment step in manufacturing the first silicon single crystal SM is always used as the power D of the heater 23 to be substituted into the equation (1). Alternatively, at the time of producing the silicon single crystal SM immediately before, two or three before (for example, at the time of producing the fourth, third, or second silicon single crystal SM in the production of the fifth silicon single crystal SM). The value obtained in the liquid landing power adjustment step may be used. If the quartz crucible 221 is not replaced, the heat retention of the single crystal pulling apparatus 1 hardly changes during the continuous production of the silicon single crystal SM, so that the value at the time of manufacturing the first silicon single crystal SM can be easily used. Step S12 can be performed.

[Operation and Effect of First Embodiment]
According to the first embodiment, the heat retaining property of the single crystal pulling apparatus 1 can be estimated by the power adjustment value of the heater 23 when the silicon single crystal SM is grown using the same quartz crucible 221 at the time of liquid contact. By adjusting the power of the heater 23 during the solidification process based on the estimation result, the surface of the silicon melt M can be properly solidified, and the quartz crucible 221 is damaged. The problem that the time is long can be suppressed.
Further, the power at the time of solidification can be set by a simple method simply by substituting each value into the equation (1).

[Second embodiment]
Next, a method for manufacturing a silicon single crystal SM by a single pulling method according to the second embodiment of the present invention will be described. The single pulling method is a method of manufacturing one silicon single crystal SM using one quartz crucible 221.
In the second embodiment, steps different from those in the manufacturing method of the first embodiment shown in FIG. 5 will be described in detail, and the same steps will be denoted by the same reference numerals and the description will be simplified. Steps S22, S4, S5, S6, and S23 of the following steps correspond to the additional charging step using the material supply method of the present invention.

First, as shown in FIG. 6, the crucible 22 containing the solid raw material S is heated to generate a silicon melt M (Step S21: initial melt generation step).
Thereafter, the control unit 4 sets the power of the heater 23 based on the power of the heater 23 at the time of liquid landing when the silicon single crystal SM was grown immediately before using another quartz crucible 221 (step S22: Solidification power, dropping power, melting power setting step based on the power at the time of liquid contact).
In the setting step of the solidification power, the dropping power, and the melting power, the control unit 4 calculates the power A (kW) of the heater 23 after the setting based on the above equation (1).

At this time, the control unit 4 calculates the power A of each of the solidification step, the dropping step, and the melting step by substituting the solidification, dropping, and melting step reference values shown in Table 1 above into B of Equation (1). I do. The control unit 4 uses, as the power D of the heater 23 to be substituted into the equation (1), a value obtained in a liquid landing power adjustment step described later during the growth of the silicon single crystal SM immediately before using another quartz crucible 221. Used.
Note that the number of drops and the solidification, drop, and melting process reference values in Table 1 may all be the same as in the first embodiment, or at least one may be different. However, it is preferable that the solidification step reference value is set to be smaller as the number of times of repeating the steps from the solidification step to the melting step increases. By setting such a solidification process reference value, the power obtained based on the equation (1) can be made substantially the same as an appropriate power, and a trouble due to an excessively low solidification speed can be suppressed.

Thereafter, the controller 4 adjusts the power of the heater 23 to the power A set in step S22, and solidifies the surface of the silicon melt M (step S4: solidification step). By setting the power of the heater 23 as described above, it is possible to prevent the quartz crucible 221 from being damaged or damaged and the solidification step from becoming too long, regardless of the heat retention of the single crystal pulling apparatus 1.
Thereafter, the control unit 4 drops the solid raw material S onto the solidified portion M1 (step S5: dropping step) and melts the solid raw material S (step S6: melting step). In the dropping step and the melting step, the control unit 4 sets the power of the heater 23 to the power A set in step S22.

Next, when the melting of the solid raw material S is completed, the control unit 4 determines whether or not to terminate the additional charge (Step S23). If it is determined that the charging is continued, the process returns to step S22, and the power A of the heater 23 in the solidification process is set. In the processing of step S22 for the second and subsequent times, the control unit 4 calculates the solidification, dropping, and melting step reference value B according to the number of repetitions of the steps from the solidification step to the melting step based on the settings in Table 1 according to the formula (1). ) To set the power A.
On the other hand, when it is determined in step S23 that the additional charge is to be ended, the manufacture of the silicon single crystal SM is started.

  The control unit 4 sets the power of the heater 23 to the liquid contacting process reference value, and then immerses the seed crystal SC in the silicon melt M (Step S1: liquid contacting process) and appropriately performs the growing process. Then, the power of the heater 23 is adjusted based on the state after the seed crystal SC is immersed (step S11: immersion power adjusting step). Thereafter, the control unit 4 raises the seed crystal SC to grow the silicon single crystal SM (Step S2: growing step), and ends the processing.

[Operation and Effect of Second Embodiment]
According to the second embodiment, since the heat retention of the single crystal pulling apparatus 1 before and after the replacement of the quartz crucible 221 hardly changes, the liquid landing when the silicon single crystal SM was grown immediately before using the different quartz crucible 221 The heat retention of the single crystal pulling apparatus 1 can be estimated based on the power adjustment value of the heater 23 at the time, and the power of the heater 23 during the solidification process is adjusted based on the estimation result, whereby the surface of the silicon melt M is solidified. Can be appropriately performed, and the problem that the quartz crucible 221 is damaged and the problem that the time of the solidification process becomes long can be suppressed.

[Modification]
It should be noted that the present invention is not limited only to the above embodiment, and various improvements and design changes can be made without departing from the spirit of the present invention.

For example, as shown by a two-dot chain line in FIG. 1, instead of the heater 23, a plurality of divided heaters 232 arranged vertically may be used. In the case where two divided heaters 232 are used, the control unit 4 sets each of the divided heaters 232 based on the following equation (2) in which the adjustment parameter α is 0.5 in the solidification power, the dropping power, and the melting power setting step. It is preferable to calculate the power A1 (kW), and the solidification step reference value B1 may be reduced as the number of repetitions of the steps from the solidification step to the melting step increases, as in the above embodiment.
A1 = B1-α × (C1-D1)
= B1-0.5 × (C1-D1) (2)
B1: Solidification, dropping, melting process standard value (kW)
C1: Liquid landing process reference value (kW)
D1: power (kW) of divided heater 232 after adjustment in liquid landing power adjustment step

If the power of the heater 23 for setting the temperature of the silicon melt M to a predetermined temperature immediately before the pulling-up step can be estimated in advance based on, for example, conventional manufacturing conditions, the processing in step S11 may not be performed.
In at least one of the dropping step and the melting step, the power is set to the dropping and melting step reference value without performing the power setting step based on the power at the time of liquid contact using Equations (1) and (2). Is also good.
When the single crystal pulling apparatus 1 of the MCZ method is used, a magnetic field may be applied to the silicon melt M in the liquid contacting step, the pulling step, and the melting step, and the magnetic field may not be applied in the solidification step and the dropping step. .
At the time of manufacturing the first silicon single crystal SM of the first embodiment, the additional charge of the second embodiment may be performed.

  Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

<Comparative Example 1>
A single crystal pulling apparatus 1 for preparing a silicon single crystal SM having a heater 23 indicated by a solid line in FIG. 1 and having a diameter of a straight body of 300 mm after cylindrical grinding was prepared.
Using the single crystal pulling apparatus 1, after performing the processes of steps S 1, S 11, S 2, and S 3 in the multiple pulling method of the above-described embodiment shown in FIG. 5, solidification power and dropping power based on the power at the time of liquid contact Without performing the melting power setting step (step S12), the processing after the solidification step (step S4) is performed to produce a plurality of silicon single crystals SM, and the solidification rate of the silicon melt M in the first solidification step is reduced. confirmed. In Comparative Example 1, the solidification, dropping, and melting process reference values shown in Table 1 were used as the power of the heater 23 during the solidification, dropping, and melting processes.
Thereafter, the same experiment was performed by replacing the quartz crucible 221 of the same single crystal pulling apparatus 1, and a total of 50 experiments were performed.

<Example 1>
Using the same single crystal pulling apparatus 1 as in Comparative Example 1, after performing the processes of steps S1, S11, S2, and S3 in the multi-pulling method of the above-described embodiment, the solidifying power based on the power at the time of liquid landing and the dropping are further added. A power and melting power setting step (step S12) was performed, and the power of the heater 23 was calculated based on the equation (1). Then, the solidification step (step S4), the dropping step (step S5), and the melting step (step S6) are performed with the calculated power, and a plurality of silicon single crystals SM are manufactured by performing the processing after step S7. The solidification rate of the silicon melt M in the first solidification step was confirmed. In Example 1, the values shown in Table 1 were used as the solidification, dropping, and melting process reference values to be substituted into Expression (1).
Thereafter, the same experiment was performed by replacing the quartz crucible 221 of the same single crystal pulling apparatus 1, and a total of 34 experimental results were obtained.

<Comparative Example 2>
A single crystal pulling apparatus 1 for preparing a silicon single crystal SM having a divided heater 232 indicated by a two-dot chain line in FIG. 1 and having a diameter of a straight body after the cylindrical grinding of 300 mm was prepared.
Using the single crystal pulling apparatus 1, the same processing as in Comparative Example 1 was performed, and the solidification rate of the silicon melt M in the first solidification step was confirmed. In Comparative Example 2, the power of the divided heater 232 during the solidification step is set to be smaller as the number of repetitions of the steps from the solidification step to the melting step increases, similarly to the solidification step reference values shown in Table 1. Values used. In addition, the power of the divided heater 232 during the dropping step and the melting step is the same value as the dropping and melting step reference values shown in Table 1 regardless of the number of repetitions of the steps from the solidification step to the melting step, and A value larger than the solidification process reference value was used.
Thereafter, the same experiment was performed by replacing the quartz crucible 221 of the same single crystal pulling apparatus 1, and a total of 16 experiments were performed.

<Example 2>
The same processing as in Example 1 was performed using the same single crystal pulling apparatus 1 as in Comparative Example 2, and the solidification rate of the silicon melt M in the first solidification step was confirmed. In Example 2, the power of the divided heater 232 was calculated based on Equation (2) in the setting step of the solidification power, the dropping power, and the melting power based on the power at the time of liquid contact. In Example 2, the same values as the reference values of Comparative Example 2 were used as the reference values for the solidification, dropping, and melting steps to be substituted into Expression (2).
Thereafter, the same experiment was performed by replacing the quartz crucible 221 of the same single crystal pulling apparatus 1, and a total of 12 experimental results were obtained.

<Evaluation>
FIG. 7 shows the solidification rate of Comparative Example 1 and Example 1, and FIG. 8 shows the solidification rate of Comparative Example 2 and Example 2.
As shown in FIGS. 7 and 8, it was confirmed that the variation in the solidification rate in Examples 1 and 2 was smaller than that in Comparative Examples 1 and 2. From this, it was confirmed that by performing the solidification power setting step based on the power at the time of liquid contact, variation in the solidification rate on the surface of the silicon melt M can be suppressed.
In particular, it was confirmed that the dispersion to the one where the solidification speed was increased was suppressed, and it was confirmed that the problem that the solidification progressed more than expected and the quartz crucible 221 was damaged can be suppressed.

  23: heater, 221: quartz crucible, 232: divided heater (heater), M: silicon melt, S: solid raw material, SC: seed crystal, SM: silicon single crystal.

Claims (11)

In producing a silicon single crystal using one quartz crucible by the Czochralski method, a raw material supply method for charging a solid raw material to a silicon melt in the quartz crucible,
Adjusting the power of the heater for heating the quartz crucible, a solidifying step of solidifying the surface of the silicon melt;
A dropping step of dropping the solid raw material on the solidified portion of the surface,
A melting step of melting the solidified portion and the solid raw material,
The solidification step is based on a value of the power of the heater at the time of the previous manufacturing of the silicon single crystal, based on a value of the power of the heater at the time of performing the liquid contacting step of contacting the seed crystal with the silicon melt. A raw material supply method comprising adjusting power. In the raw material supply method according to claim 1,
The method according to claim 1, wherein the dropping step adjusts the power of the heater in the dropping step based on a value of the power of the heater when the liquid landing step in the production of the conventional silicon single crystal is performed. . In the raw material supply method according to claim 1 or 2,
The raw material supply method, wherein the melting step adjusts the power of the heater in the melting step based on the value of the power of the heater when the liquid contacting step in the production of the conventional silicon single crystal is performed. . In the raw material supply method according to claim 1,
In the solidifying step, when the power of the heater at the time of performing the liquid contacting step is larger than a liquid contacting step reference value, the power of the heater in the solidifying step is set larger than the solidifying step reference value. Raw material supply method. In the raw material supply method according to claim 1 or 4,
The solidifying step is characterized in that, when the power of the heater at the time of performing the liquid contacting step is smaller than a liquid contacting step reference value, the power of the heater in the solidifying step is set smaller than a solidifying step reference value. Raw material supply method. In the raw material supply method according to claim 1,
In the solidifying step, the power of the heater is adjusted based on the following equation (1).
A = B−α × (C−D) (1)
A: Heater power after adjustment B: Solidification process reference value C: Dipping process reference value D: Heater power when the above-mentioned dipping process is performed α: Adjustment parameter In the raw material supply method according to claim 6,
The solidification step, the dropping step, and the melting step are each repeatedly performed twice or more the same number of times,
The method according to claim 1, wherein the solidification step reference value is set to a smaller value as the number of repetitions increases. A method for producing a silicon single crystal by continuously producing a plurality of silicon single crystals using one quartz crucible by the Czochralski method,
A dipping step of dipping the seed crystal into the silicon melt,
A growing step of pulling up the seed crystal and growing a silicon single crystal,
A recharging step of performing the raw material supply method according to any one of claims 1 to 7, when recharging a solid raw material for producing a second or subsequent silicon single crystal to a silicon melt in a quartz crucible, With
The solidifying step in the recharging step is based on a value of the power of the heater when the liquid contacting step is performed during the production of any silicon single crystal using the same quartz crucible. A method for producing a silicon single crystal, comprising adjusting power. The method for producing a silicon single crystal according to claim 8,
Heating the quartz crucible containing the solid raw material to generate a silicon melt,
An additional charging step of additionally charging a solid raw material to the silicon melt in the quartz crucible using the raw material supply method according to any one of claims 1 to 7,
The solidification step in the additional charge step, the heater of the solidification step based on the value of the power of the heater at the time of performing the liquid landing step during the production of silicon single crystal immediately before using another quartz crucible A method for producing a silicon single crystal, characterized in that the power of the silicon single crystal is adjusted. A method for manufacturing a silicon single crystal, wherein one silicon single crystal is manufactured using one quartz crucible by the Czochralski method,
Heating the quartz crucible containing the solid raw material to generate a silicon melt,
An additional charging step of additionally charging a solid raw material to a silicon melt in the quartz crucible using the raw material supply method according to any one of claims 1 to 7,
A dipping step of dipping the seed crystal into the silicon melt,
A growing step of pulling up the seed crystal and growing a silicon single crystal,
The solidification step in the additional charge step, the heater of the solidification step based on the value of the power of the heater at the time of performing the liquid landing step during the production of silicon single crystal immediately before using another quartz crucible A method for producing a silicon single crystal, characterized in that the power of the silicon single crystal is adjusted. The method for producing a silicon single crystal according to any one of claims 8 to 10,
A silicon single crystal comprising a liquid-adhesion power adjustment step of adjusting the power of the heater so that the temperature of the silicon melt becomes a predetermined temperature between the liquid-immersion step and the growing step. Manufacturing method.

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