CN110983439A

CN110983439A - Raw material supply method and method for producing single crystal silicon

Info

Publication number: CN110983439A
Application number: CN201910922845.9A
Authority: CN
Inventors: 八木大地; 片野智一; 金原崇浩
Original assignee: Sumco Corp
Current assignee: Sumco Corp
Priority date: 2018-10-03
Filing date: 2019-09-27
Publication date: 2020-04-10
Also published as: JP7021626B2; JP2020055718A

Abstract

The present invention provides a raw material supply method, comprising the following steps: a solidification step of adjusting the power of a heater for heating the quartz crucible to solidify the surface of the silicon melt; a charging step of charging a solid material into a solidified portion of the surface; and a melting step of melting the solidified portion and the solid raw material, wherein the solidifying step is performed by adjusting the power of a heater in the solidifying step based on the power value of the heater in the deposition step of depositing the seed crystal in the silicon melt in the conventional production of the silicon single crystal.

Description

Raw material supply method and method for producing single crystal silicon

Technical Field

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

Background

Conventionally, when a plurality of silicon single crystals are continuously produced by the Czochralski (Czochralski) method, a method of reloading (recharging) a solid raw material for producing the 2 nd and subsequent silicon single crystals into a silicon melt in a crucible has been known (for example, see document 1: japanese patent application laid-open No. 2007-246356).

The method of document 1 includes: and a step of solidifying the surface of the silicon melt before the solid raw material is put into the silicon melt. In the solidification step, the power of a heater for heating the crucible is set so that the time until a region corresponding to 80% of the entire surface of the silicon melt is solidified and the inner diameter of the crucible satisfy a predetermined relationship.

However, in the method such as document 1, the surface solidification of the silicon melt proceeds to a level more than expected, and for example, the solidified portion sinks when the solid raw material is charged, so that there is a possibility that the quartz crucible is damaged. Further, the surface solidification of the silicon melt may not proceed to a degree more than expected, and the time for the solidification step may be prolonged.

Disclosure of Invention

The object of the present invention is to provide: a method for supplying a raw material and a method for producing a silicon single crystal, which can be suitably loaded without damaging a quartz crucible.

The raw material supply method of the present invention is characterized in that: the method for supplying a raw material for charging a solid raw material into a silicon melt in a quartz crucible when single-crystal silicon is produced by a pulling method using 1 quartz crucible, comprises the steps of: a solidification step of solidifying the surface of the silicon melt by adjusting the power of a heater for heating the quartz crucible; a charging step of charging the solid material to the solidified portion of the surface; and a melting step of melting the solidified portion and the solid raw material; wherein the solidification step is performed by adjusting the power of the heater in the solidification step based on the power value of the heater in the conventional process of depositing the seed crystal in the silicon melt during the production of the silicon single crystal.

The "power of the heater when the step of depositing the seed crystal in the silicon melt is performed" means a power immediately after the deposition of the seed crystal and before the pulling (for example, 1 second before the pulling), and means a power after the adjustment when the power is adjusted after the deposition and before the pulling.

In the raw material supply method of the present invention, it is preferable that the charging step adjusts the power of the heater in the charging step based on the power value of the heater in the case where the liquid deposition step is performed in the conventional production of single-crystal silicon.

In the raw material supply method of the present invention, it is preferable that the melting step adjusts the power of the heater used in the melting step based on the power value of the heater used in the melting step performed in the conventional production of single crystal silicon.

In the raw material supply method of the present invention, when the power of the heater in the liquid applying step is larger than a reference value for the liquid applying step, the power of the heater in the curing step is preferably larger than the reference value for the curing step.

In the raw material supply method of the present invention, when the power of the heater in the liquid applying step is smaller than a reference value for the liquid applying step, the power of the heater in the curing step is preferably smaller than the reference value for the curing step.

In the raw material supply method of the present invention, the curing step preferably adjusts the power of the heater based on the following formula (1):

A=B-α×(C-D)　… (1)

a: the adjusted power of the heater;

b: a curing process reference value;

c: a liquid deposition process reference value;

d: the power of the heater when the liquid applying process is carried out;

α, parameters for adjustment.

The curing step reference value B is a power value of the heater at which the curing speed of the surface of the silicon melt reaches a target value. The reference value C for the seed crystal deposition step is "the power of the heater when performing the step of depositing the seed crystal in the silicon melt" in the single crystal pulling apparatus in which the solidification rate of the silicon melt surface reaches the target value, and is the power immediately after the seed crystal is deposited and before the seed crystal is pulled (for example, 1 second before the pulling). The heater power after the liquid application and before the pulling is adjusted means the adjusted heater power. That is, the liquid applying step reference value C corresponds to the heater power D when the liquid applying step is performed in the single crystal pulling apparatus whose solidification speed reaches the target value, and (D-C) =0 in the single crystal pulling apparatus whose solidification speed reaches the target value.

The adjustment parameter α has a positive value close to 1, and specifically, can be set to a value in the range of 0 < α. ltoreq.2. by using this adjustment parameter α, it is possible to adjust the power in accordance with the characteristics of each single crystal pulling apparatus.

In the raw material supply method of the present invention, the solidification step, the charging step, and the melting step are each repeated 2 or more times, and the solidification step reference value is preferably set to a value that decreases as the number of repetitions increases.

The method for manufacturing a silicon single crystal of the present invention is characterized in that: the method for manufacturing a silicon single crystal is a method for continuously manufacturing a plurality of silicon single crystals by a pulling method using 1 quartz crucible, and comprises the steps of: a seed crystal deposition step of depositing a seed crystal in a silicon melt; a growing step of pulling up the seed crystal to grow a silicon single crystal; and a reloading step of performing the raw material supply method when reloading the silicon melt in the quartz crucible with a solid raw material for manufacturing the 2 nd and subsequent silicon single crystals, wherein the solidification step in the reloading step is a step of adjusting the power of the heater in the solidification step based on the power value of the heater when the liquid deposition step is performed in manufacturing any one of the silicon single crystals using the same quartz crucible.

The method for manufacturing a silicon single crystal of the present invention includes the steps of: an initial melt generation step of heating a quartz crucible containing a solid raw material to generate a silicon melt; and an additional charging step of additionally charging a solid raw material into the silicon melt in the quartz crucible by using the raw material supply method, wherein the power of the heater in the curing step is preferably adjusted in the curing step based on a power value of the heater when the liquid charging step is performed in the production of silicon single crystal just before using another quartz crucible.

The method for producing a silicon single crystal of the present invention is characterized in that: the method for producing 1 silicon single crystal by a Czochralski method using 1 quartz crucible comprises the steps of: an initial melt generation step of heating a quartz crucible containing a solid raw material to generate a silicon melt; an additional charging step of additionally charging a solid raw material into the silicon melt in the quartz crucible by the above-described raw material supply method; a seed crystal deposition step of depositing a seed crystal in a silicon melt; and a growth step of pulling up the seed crystal to grow the silicon single crystal, wherein the solidification step in the additional loading step is performed by adjusting power of the heater in the solidification step based on a power value of the heater when the liquid deposition step is performed in the production of the silicon single crystal just before using another quartz crucible.

In the method for producing single-crystal silicon of the present invention, it is preferable that the following deposition power adjusting step be provided between the deposition step and the growing step: adjusting the power of the heater to make the temperature of the silicon melt reach a predetermined temperature.

According to the present invention as described above, there can be provided: a method for supplying a raw material and a method for producing a silicon single crystal, which can be suitably loaded without damaging a quartz crucible.

Drawings

Fig. 1 is a schematic view of a single crystal pulling apparatus according to a related art and one embodiment of the present invention.

Fig. 2 is a flowchart of a method of manufacturing single crystal silicon in the above-described related art.

Fig. 3A is a schematic view showing the case of refilling in the related art and embodiment 1 and additional filling in embodiment 2, showing a curing process.

Fig. 3B is a schematic diagram showing the case of refilling in the related art and embodiment 1 and additional refilling in embodiment 2, showing the charging process.

Fig. 4 is a graph showing a relationship between an adjustment value of heater power at the time of seed crystal deposition and a solidification rate of a silicon melt, and is a result of an experiment conducted to guide the present invention.

Fig. 5 is a flowchart of a method for manufacturing single crystal silicon in embodiment 1.

Fig. 6 is a flowchart of a method for manufacturing single crystal silicon according to embodiment 2.

Fig. 7 is a graph showing the deviation (ばらつき, change) of the curing speed of comparative example 1 and example 1 in the example of the present invention.

Fig. 8 is a graph showing the deviation of the curing speed of comparative example 2 and example 2 in the above examples.

Detailed Description

[ correlation technique of the invention ]

First, a related art of the present invention is explained based on the drawings.

[ constitution of Single Crystal pulling apparatus ]

As shown in fig. 1, a single crystal pulling apparatus 1 is a device used in the Czochralski method, and includes a pulling apparatus main body 2, a memory 3, and a control unit 4.

The pulling device body 2 includes: a chamber 21, a crucible 22 disposed in the chamber 21, a heater 23 for heating the crucible 22, a pulling portion 24, a heat shield 25, a heat insulating material 26, and a crucible driving portion 27.

The single crystal pulling apparatus 1 is used in the MCZ (magnetic field applied Czochralski) method as shown by a two-dot chain line, and may have a pair of electromagnetic coils 28 disposed so as to sandwich the crucible 22 outside the chamber 21.

The chamber 21 includes a main chamber 211 and a pull chamber (sub chamber) 213 connected to an upper portion of the main chamber 211 via a gate valve 212. A gas inlet 21A for introducing an inert gas such as Ar gas into the main chamber 211 is provided in the draft chamber 213. A gas discharge port 21B for discharging gas in the main chamber 211 is provided at a lower portion of the main chamber 211.

The crucible 22 is a container for melting the solid raw material S (see fig. 3B) to form the silicon melt M. The crucible 22 includes a quartz crucible 221 and a graphite crucible 222 accommodating the quartz crucible 221. The quartz crucible 221 is exchanged for each growth of 1 or more single crystal silicon SM. On the other hand, the graphite crucible 222 is not exchanged every time 1 single-crystal silicon SM is produced, but exchanged at a time point when it is considered that the quartz crucible 221 cannot be appropriately supported.

The heater 23 is disposed around the crucible 22, and melts the silicon in the crucible 22. A bottom heater 231 shown by a two-dot chain line may be further provided below the crucible 22.

The pulling section 24 includes: a cable 241 with one end provided with a seed crystal SC; and a pulling driving part 242 for lifting and rotating the cable 241.

The heat shield 25 is provided to surround the single crystal silicon SM and shield radiant heat emitted upward from the heater 23.

The crucible driving unit 27 includes a support shaft 271 for supporting the graphite crucible 222 from below, and rotates and moves up and down the crucible 22 at a predetermined speed.

The hot zone in the single crystal pulling apparatus 1 refers to the chamber 21, the crucible 22, the heater 23, the cable 241, the heat shield 25, the heat insulator 26, the support shaft 271, the silicon melt M, the single crystal silicon SM, and the like.

The memory 3 stores various information necessary for manufacturing the silicon single crystal SM, such as a gas flow rate or a furnace pressure in the chamber 21, electric power to be supplied to the heater 23, and a rotational speed (pellet) of the crucible 22 or the silicon single crystal SM.

The control section 4 manufactures the single-crystal silicon SM based on various information stored in the memory 3 or an operation by an operator.

[ method for producing silicon Single Crystal ]

Next, a method for manufacturing single-crystal silicon SM by the multiple pulling method will be described. The multiple pulling method is a method of continuously manufacturing a plurality of single crystal silicon SM using 1 quartz crucible 221.

First, as shown in FIG. 2, a seed crystal SC is deposited on a silicon melt M contained in a crucible 22 (step S1: deposition step).

Then, the control unit 4 pulls the seed crystal SC to grow the single crystal silicon SM (step S2: growing step). The cultivation step comprises: a step (pulling step) of raising the crucible 22 while rotating the seed crystal SC; a step (cutting step) of cutting (cleaving) the tail of the single crystal silicon SM from the silicon melt M; a step (cooling step) of cooling the silicon single crystal SM cut from the silicon melt M while pulling it; a step (closing step) of storing the cooled silicon single crystal SM in the pulling chamber 213 and then closing the gate valve 212; and a step (taking-out step) of taking out the single crystal silicon SM from the pulling chamber 213.

After the completion of the growth process or during the execution of the growth process, the control unit 4 determines whether or not to perform growth of the next silicon single crystal SM (step S3).

In step S3, when the control unit 4 determines that the growth of the number of silicon single crystals SM set in advance is completed and the next growth is not performed, the process is terminated. On the other hand, when it is determined in step S3 that the growth of the previously set number of silicon single crystals SM has not been completed and the next growth is to be performed, control unit 4 sets the power of heater 23 to a preset reference value for the solidification step and solidifies the surface of silicon melt M (step S4: solidification step). By this solidification process, as shown in fig. 3A, the entire surface of silicon melt M is solidified to form solidified portion M1. The target value of the curing rate is, for example, 14 mm/min to 20 mm/min based on the experimental results so far, and a preferable value is 17 mm/min.

Thereafter, when the solidified portion M1 having an appropriate diameter and thickness is formed as shown by the solid line in FIG. 3A, the controller 4 charges the solid raw material S onto the solidified portion M1 as shown in FIG. 3B (step S5: charging step). In this charging step, the control section 4 sets the power of the heater 23 to a charging step reference value larger than the curing step reference value to suppress curing, and thereafter charges the solid raw material S in a chunk tube manner using the raw material supply device 5. The raw material supply device 5 lowers a cylindrical quartz tube 51 called a chunk tube filled with the solid raw material S onto the solidified portion M1, and then moves a bottom cover 52 attached to a lower end opening of the quartz tube 51 downward to open the lower end opening of the quartz tube 51, thereby feeding the solid raw material S into the solidified portion M1.

The transfer from the curing step to the charging step may be performed based on the result of visual confirmation by an operator or the result of imaging by an imaging means.

After that, when the charging of the solid raw material S is completed, the power of the heater 23 is set to a melting step reference value that is the same as the charging step reference value, that is, the power is maintained, and the process proceeds to a step of melting the solid raw material S (step S6: melting step).

Next, when the melting of the solid raw material S is completed, the control unit 4 determines whether or not the refilling is to be completed (step S7).

In step S7, when the control unit 4 determines that the number of loading steps set in advance has been performed and that reloading has been completed, the process returns to step S1 to start the production of the next silicon single crystal SM.

On the other hand, if it is determined in step S5 that the number of times of loading has not been performed and reloading is continued, the process returns to step S4.

Through the above-described process, a plurality of single crystal silicon SMs are continuously manufactured.

[ passing until the present invention is guided ]

The present inventors have made extensive studies and, as a result, have obtained the following findings.

The heat retaining property of the single crystal pulling apparatus 1 may vary depending on tolerances or deterioration of the shape or arrangement of the components of the hot zone. Examples of the components of the hot zone include the chamber 21, the crucible 22, the heater 23, the cable 241, the heat shield 25, the heat insulator 26, the support shaft 271, the silicon melt M, and the silicon single crystal SM.

The inventors concluded that: due to such a change in the heat retaining property of the single crystal pulling apparatus 1, the state of progress of solidification of the surface of the silicon melt M also changes, and there is a possibility that unexpected damage of the quartz crucible 221 occurs or the time for the solidification step becomes long.

Therefore, the following experiment was performed.

First, using the single crystal pulling apparatus 1 described above, the power of the heater 23 is set to the standard value for the seed crystal SC in the silicon melt M. The liquid applying step reference value may be, for example, an average value of powers in a liquid applying step performed in the past, but may be a value set according to another reference. For example, as the reference value for the seed crystal deposition step, the relationship (approximate line L) between the "adjustment value of the heater power at the time of deposition of the seed crystal SC" and the "solidification rate of the silicon melt M" shown in fig. 4 to be described later may be grasped, and the heater power at the time of deposition of the seed crystal SC when the solidification rate reaches the target value may be adopted.

Then, the power of the heater 23 is adjusted based on the state after the seed crystal SC is deposited. In this adjustment, when the temperature of silicon melt M is lowered to a level more than expected due to the low heat retaining property of single crystal pulling apparatus 1 and growth is rapidly performed, the power is increased. On the other hand, if the temperature of silicon melt M is increased to a level higher than the expected level due to the high heat retaining property of single crystal pulling apparatus 1, seed crystal SC may melt in silicon melt M, the power is reduced. Further, when the heat retaining property of the single crystal pulling apparatus 1 is within a predetermined range and the growth step can be performed appropriately, the power is maintained.

Thereafter, the processes of steps S3, S4, S5, S6, and S7 shown in fig. 2 were performed to produce a plurality of single-crystal silicon SMs, and the solidification rate in the solidification step after the 1 st single-crystal silicon SM was produced (hereinafter, sometimes referred to as "1 st solidification step") was confirmed.

Thereafter, the same experiment was carried out using different single crystal pulling apparatuses 1, and the relationship between the power adjustment value during the liquid application and the solidification rate in the 1 st solidification step was confirmed. In all experiments, the reference values of the solidification, charging, and melting steps in the 1 st solidification, charging, and melting steps were set to the same values.

The relationship between the power adjustment value during the deposition and the solidification rate of silicon melt M is shown in FIG. 4. The horizontal axis of fig. 4 shows the ratio of the power adjustment value with respect to the liquid application step reference value.

As shown by the approximate line L of fig. 4, it can be confirmed that: the larger the power adjustment value at the time of melting, the faster the solidification speed of silicon melt M. The results are considered to show: when the power adjustment value during the liquid application is large and the heat retaining property of the single crystal pulling apparatus 1 is low, the solidification speed in the solidification step is increased; when the adjustment value of the power is small and the heat retaining property of the single crystal pulling apparatus 1 is high, the solidification speed is low.

From the above explanation it is assumed that: the heat retaining property of the single crystal pulling apparatus 1 can be estimated by adjusting the power of the heater 23 during the liquid application, and the power of the heater 23 during the solidification, charging, and melting steps can be adjusted based on the estimation result, whereby the surface of the silicon melt M can be appropriately solidified, and reloading can be appropriately performed.

For example, when the power at the time of the liquid application is larger than the reference value of the liquid application step, the power at the time of the solidification, injection, or melting step is made larger than the reference value of the solidification, injection, or melting step.

It is considered that by making the power at the time of the curing step larger than the curing step reference value, the curing speed can be reduced, and defects caused by an excessively high curing speed, for example, defects such as breakage of the quartz crucible 221 due to progress of curing to an extent more than expected, can be suppressed.

Further, it is considered that by making the power at the time of the charging step larger than the charging step reference value, the temperature decrease of the solidified portion M1 at the time of charging the solid raw material S can be suppressed, and the problem that the solidified portion M1 becomes large or thick and the quartz crucible 221 is broken can be suppressed.

Further, by making the power at the time of the melting step larger than the melting step reference value, the temperature of the melt at the time of completion of the melting step can be raised, and the solidification rate at the time of next charging of the raw material can be adjusted to a target value (for example, 14 mm/min or more).

On the other hand, when the power at the time of the liquid application is smaller than the reference value of the liquid application step, the power at the time of the solidification, injection, and melting step is made smaller than the reference value of the solidification, injection, and melting step. It is considered that the curing speed can be increased by setting the power at the time of the curing step to be smaller than the curing step reference value, and a problem caused by an excessively low curing speed, for example, a problem that the curing is not progressed more than an assumed level and the time of the curing step is prolonged can be suppressed.

Further, it is considered that by making the power at the time of the charging step smaller than the charging step reference value, the melting rate of the solidified portion M1 can be reduced, the solid raw material S can be suppressed from being directly charged into the silicon melt M, and the silicon melt M can be suppressed from scattering.

Further, by making the power at the time of the melting step smaller than the melting step reference value, the temperature of the melt at the time of completion of the melting step can be lowered, and the solidification rate at the time of the next charging of the raw material can be adjusted to a target value (for example, 20 mm/min or less).

[ embodiment 1]

Next, a method for manufacturing single-crystal silicon SM by the multiple pulling method according to embodiment 1 of the present invention will be described. In the manufacturing method described in embodiment 1 and embodiment 2 described later, the diameter of the straight part of the single-crystal silicon SM after the cylindrical grinding may be 200mm, 300mm, 450mm, or another size. The dopant for resistivity adjustment may be added to the silicon melt M or may not be added.

In embodiment 1, steps different from the manufacturing method of the related art shown in fig. 2 are described in detail, and the same steps are denoted by the same reference numerals and are not described again. In the following steps, steps S12, S4, S5, S6, and S7 correspond to a refilling step using the raw material supply method of the present invention.

First, as shown in FIG. 5, a seed crystal SC is deposited in a silicon melt M (step S1: deposition step). In the liquid deposition step, the control unit 4 sets the power of the heater 23 to a reference value for the liquid deposition step, and then deposits the seed crystal SC on the silicon melt M.

Thereafter, the control unit 4 adjusts the power of the heater 23 based on the state of the seed crystal SC after deposition in order to properly perform the growth step (step S11: deposition power adjustment step). In this liquid applying power adjusting step, as described above in the course of the present invention, the power is increased when the heat retaining property of the single crystal pulling apparatus 1 is low, the power is decreased when the heat retaining property is high, and the power is maintained when the heat retaining property is within a predetermined range, based on the state of the seed crystal SC. By this adjustment, the temperature of silicon melt M immediately before the pulling step can be brought to a predetermined temperature.

Next, the control unit 4 pulls the seed crystal SC to grow the single-crystal silicon SM (step S2: growing step), and after the end of the growing step or during the growing step, the control unit 4 determines whether or not to grow the next single-crystal silicon SM (step S3).

In this step S3, the process is ended when the control unit 4 determines that the next growth is not to be performed, and when it determines that the next growth is to be performed, the power of the heater 23 is set based on the power of the heater 23 at the time of liquid application when the single crystal silicon SM is grown using the same quartz crucible 221 (step S12: solidification power, input power, melting power setting step based on the power at the time of liquid application).

In the solidification power, input power, and melting power setting step, the control unit 4 calculates the set power a (kw) of the heater 23 based on the following expression (1) in which the adjustment parameter α is 1.

A=B-α×(C-D)

=B-1×(C-D)　… (1)；

B: a standard value (kW) of the curing, charging and melting process;

c: a liquid application process reference value (kW);

d: the adjusted power (kW) of the heater 23 in the liquid applying power adjusting step.

At this time, the control unit 4 substitutes the solidification, charging, and melting process reference values shown in table 1 below for B in formula (1), and calculates the respective powers a of the solidification process, charging process, and melting process. In order to solidify the surface of silicon melt M, the solidification step reference value in table 1 is set to a value smaller than power P (kw) which is the input step reference value and the melting step reference value (for example, solidification step reference value B at the time of the input number of times 1 is 0.5 times power P). The solidification step reference value B is set such that B decreases as the number of repetitions of steps from the solidification step to the melting step increases. The power P is adjusted to a value of 14 mm/min to 20 mm/min, which is the target value of the solidification rate, because the power P varies depending on the heat retaining property of the single crystal pulling apparatus 1. For example, when the adjusted power P for the single crystal pulling apparatus 1 having a certain structure is 100kW, the reference value B of the solidification step in which the number of times of charging is 1 is 50kW, and the reference value B of the charging and melting steps is 100 kW.

The power a obtained by the formula (1) is larger than the solidification, charging, and melting step reference value B when the heat retaining property of the single crystal pulling apparatus 1 is low and the power D of the heater 23 after adjustment in the liquid-applying power adjustment step is larger than the liquid-applying step reference value C, and is smaller than the solidification, charging, and melting step reference value B when the heat retaining property of the single crystal pulling apparatus 1 is high.

[ Table 1]

Thereafter, control unit 4 adjusts the power of heater 23 to power a set in step S12 based on the solidification step reference value, and solidifies the surface of silicon melt M (step S4: solidification step), thereby forming solidified portion M1 in silicon melt M as shown in fig. 3A.

In this case, even under the condition that the single crystal pulling apparatus 1 has a low heat retaining property and the solidification speed is likely to be increased, the solidification process is performed at a power a higher than the solidification process reference value B, so that the solidification speed can be suppressed from becoming excessively high. Therefore, as shown by the two-dot chain line in fig. 3A, the transfer to the charging step described later can be easily performed before the cured portion M1 becomes too thick. As a result, the thickened solidified portion M1 can be prevented from sinking due to the input of the solid raw material S and causing damage or defects to the quartz crucible 221.

On the other hand, even in the case of the conditions that the single crystal pulling apparatus 1 has a high heat retaining property and the solidification speed is liable to be lowered, since the solidification step is performed at a power a lower than the solidification step reference value B, the solidification speed can be suppressed from being excessively lowered. This can prevent the curing step from being too long.

After that, when the solidified portion M1 having an appropriate diameter and thickness is formed, the controller 4 adjusts the power of the heater 23 to the power a set in step S12 based on the charging step reference value, and charges the solid raw material S into the solidified portion M1 (step S5: charging step).

In this case, even when the single crystal pulling apparatus 1 has a low heat retaining property and is under conditions in which the temperature of the solidified portion is likely to decrease when the solid raw material is charged, since the charging step is performed at a power a that is greater than the charging step reference value B, it is possible to suppress the solidified portion M1 from becoming large or thick and causing damage or defects to the quartz crucible 221.

On the other hand, even in the case of the conditions that the single crystal pulling apparatus 1 has a high heat retaining property and the solidified portion M1 is easily melted, since the charging step is performed at a power a smaller than the charging step reference value B, the solid raw material S can be prevented from being directly charged into the silicon melt M along with the melting of the solidified portion M1, and the silicon melt M can be prevented from scattering.

The transition from the solidification step to the charging step may be performed based on the visual check result of the operator or the imaging result of the imaging means, but by setting the power a based on the formula (1), the temperature variation of the silicon melt M in the solidification step becomes small and the variation of the time until the solidified portion M1 reaches the desired thickness becomes small regardless of the heat retaining property of the single crystal pulling apparatus 1, so that the transition may be performed after a predetermined time has elapsed from the start of the solidification step.

After that, when the charging 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 step reference value, that is, the power of the heater 23 is maintained, and the process proceeds to the step of melting the solid raw material S (step S6: melting step).

In this case, even in the case of the condition that the single crystal pulling apparatus 1 has a low heat retaining property and the solidified portion M1 is not easily melted, since the melting step is performed at a power a larger than the melting step reference value B, it is possible to suppress the inconvenience that the time for the melting step is long. The temperature of the melt at the completion of the melting step can be raised, and the solidification rate at the next charge of the raw material can be adjusted to a target value (for example, 14 mm/min or more).

On the other hand, even in the case of the conditions where the single crystal pulling apparatus 1 has a high heat retaining property and the solidified portion M1 is easily melted, since the melting step is performed at a power a smaller than the melting step reference value B, the melt temperature at the time of completion of the melting step can be lowered, and the solidification rate at the time of the next charging of the 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 the reloading is to be completed (step S7), and when it is determined that the reloading is to be completed by the number of times set in advance, that is, 4 times in the present embodiment, the process returns to step S1, and the next production of the single crystal silicon SM is started.

On the other hand, when it is determined in step S7 that reloading is to be continued, the process returns to step S12, and the power a of the heater 23 in the solidification step, the injection step, and the melting step is set. In the processing of step S12 from the 2 nd time onward, the control unit 4 substitutes the solidification, charging, and melting step reference value B, which corresponds to the number of repetitions of the steps from the solidification step to the melting step, into formula (1) based on the settings in table 1, and sets the power a.

Here, as shown in table 1, the reference value of the solidification step is preferably smaller 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 silicon melt M increases as the number of repetitions increases, and the heat retaining property of crucible 22 increases. As a result, the power obtained by the formula (1) is larger than the appropriate power, and the curing speed is too slow, which may cause a problem. As in the present embodiment, by decreasing the curing process reference value as the number of repetitions increases, the power obtained by equation (1) can be made substantially the same as the appropriate power, and defects due to excessively slow curing speed can be suppressed.

In the processing of step S12 after the 2 nd time, the power D of the heater 23 in the formula (1) may be a value obtained in the liquid applying power adjusting step in the production of the 1 st silicon crystal SM, or may be a value obtained in the liquid applying power adjusting step in the production of the silicon crystal SM immediately before, 2 before, or 3 before (for example, in the production of the 5 th silicon crystal SM, the 4 th, 3 rd, or 2 nd silicon crystal SM). Since the heat retaining property of the single crystal pulling apparatus 1 hardly changes in the continuous production of the single crystal silicon SM if the quartz crucible 221 is not exchanged, the process of step S12 can be easily performed if the value normally used in the production of the 1 st single crystal silicon SM is adopted.

[ Effect of embodiment 1]

According to embodiment 1 described above, the heat retaining property of the single crystal pulling apparatus 1 can be estimated from the power adjustment value of the heater 23 during the liquid deposition when the single crystal silicon SM is grown using the same quartz crucible 221, and the power of the heater 23 during the solidification step is adjusted based on the estimation result, whereby the surface of the silicon melt M can be appropriately solidified, and a problem that the quartz crucible 221 is damaged or a problem that the time for the solidification step is prolonged can be suppressed.

In addition, the power at the time of curing can be set by a simple method of simply substituting each value into the formula (1).

[ 2 nd embodiment ]

Next, a method for manufacturing single crystal silicon SM by a single pulling method according to embodiment 2 of the present invention will be described. The single pulling method refers to a method of manufacturing 1 single crystal silicon SM using 1 quartz crucible 221.

In embodiment 2, steps different from the manufacturing method of embodiment 1 shown in fig. 5 will be described in detail, and the same steps will be denoted by the same reference numerals and will be described in brief. In the following steps, steps S22, S4, S5, S6, and S23 correspond to an additional filling step using the raw material supply method of the present invention.

First, as shown in FIG. 6, crucible 22 containing solid raw material S is heated to produce silicon melt M (step S21: initial melt production step).

Thereafter, the control unit 4 sets the power of the heater 23 based on the power of the heater 23 during the liquid application when the silicon single crystal SM is grown just before using another quartz crucible 221 (step S22: solidification power, input power, melting power setting step based on the power during the liquid application).

In the solidification power, input power, and melting power setting step, the control unit 4 calculates the set power a (kw) of the heater 23 based on the above equation (1).

At this time, the control unit 4 substitutes the reference values for the solidification, injection, and melting steps shown in table 1 for B in formula (1) and calculates the powers a for the solidification, injection, and melting steps, respectively. The control section 4 uses, as the power D of the heater 23 in the formula (1), a value obtained in a later-described liquid applying power adjusting step at the time of growing the silicon single crystal SM just before using the other quartz crucible 221.

In table 1, the number of times of charging, or the reference values of the solidification, charging, and melting steps may be completely the same as those in embodiment 1, or at least one may be different. However, the curing process reference value is preferably set to: the reference value is smaller as the number of repetitions of the steps from the solidification step to the melting step increases. By setting the reference value for the curing step as described above, the power obtained by the equation (1) can be made substantially the same as the appropriate power, and defects caused by excessively slow curing speed can be suppressed.

Thereafter, control unit 4 adjusts the power of heater 23 to power A set in step S22 to cure the surface of silicon melt M (step S4: curing step). By setting the power of the heater 23 as described above, it is possible to suppress the breakage or the occurrence of flaws in the quartz crucible 221 or the time required for the solidification process from becoming excessively long, regardless of the heat retaining property of the single crystal pulling apparatus 1.

Thereafter, the controller 4 charges the solid raw material S into the solidified portion M1 (step S5: charging step), and melts the solid raw material S (step S6: melting step). In the charging step and the melting step, the controller 4 sets the power of the heater 23 to the power a set in step S22.

Next, the controller 4 determines whether or not to end the additional charging when the melting of the solid raw material S is completed (step S23), and when it is determined that the additional charging is not performed and continued a predetermined number of times, the control returns to step S22 to set the power a of the heater 23 in the solidification step. In the processing of step S22 after the 2 nd time, the control unit 4 substitutes the solidification, charging, and melting step reference value B corresponding to the number of repetitions of the steps from the solidification step to the melting step into formula (1) based on the settings in table 1, and sets the power a.

On the other hand, when it is determined in step S23 that the additional loading is ended, the production of single-crystal silicon SM is started.

The control unit 4 sets the power of the heater 23 to the reference value of the seed crystal deposition step, then deposits the seed crystal SC on the silicon melt M (step S1: deposition step), and adjusts the power of the heater 23 based on the state after deposition of the seed crystal SC in order to appropriately perform the growth step (step S11: deposition power adjustment step). Thereafter, the control unit 4 pulls the seed crystal SC to grow the single crystal silicon SM (step S2: growing step), and the process is terminated.

[ Effect of embodiment 2 ]

According to embodiment 2 described above, since the heat retaining property of the single crystal pulling apparatus 1 before and after the quartz crucible 221 exchange is almost unchanged, the heat retaining property of the single crystal pulling apparatus 1 can be estimated from the power adjustment value of the heater 23 during the liquid deposition when the single crystal silicon SM is grown immediately before using a different quartz crucible 221, and by adjusting the power of the heater 23 during the solidification step based on the estimation result, the surface of the silicon melt M can be appropriately solidified, and a problem that the quartz crucible 221 is damaged or the time for the solidification step is prolonged can be suppressed.

[ modified examples ]

The present invention is not limited to the above-described embodiments, and various improvements, design changes, and the like can be made without departing from the scope of the present invention.

For example, as shown by the two-dot chain line in fig. 1, a plurality of split heaters 232 arranged in parallel up and down may be used instead of the heater 23, and in the case of using two split heaters 232, the controller 4 preferably calculates the power a1(kW) of each split heater 232 based on the following expression (2) in which the adjustment parameter α is 0.5 in the solidification power, input power, and melting power setting step, and may decrease the solidification step reference value B1 as the number of process repetitions 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: a standard value (kW) of the curing, charging and melting process;

c1: a liquid application process reference value (kW);

d1: the adjusted power (kW) of the separate heater 232 in the liquid applying power adjusting step.

For example, if the power of the heater 23 for making the temperature of the silicon melt M just before the pulling step a predetermined temperature can be estimated in advance based on the conventional manufacturing conditions, the process of step S11 may not be performed.

In at least one of the charging step and the melting step, the power setting step based on the power at the time of liquid application using the expressions (1) and (2) may be not performed, but the power may be set to a reference value for the charging and melting steps.

In the case of the single crystal pulling apparatus 1 using the MCZ method, the silicon melt M may be applied with a magnetic field in the deposition step, the pulling step, and the melting step, and the magnetic field may not be applied in the solidification step and the charging step.

In the production of the 1 st silicon single crystal SM of embodiment 1, additional loading of embodiment 2 may be performed.

Examples

The present invention will be described in further 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 manufacturing a single crystal silicon SM having a heater 23 shown by a solid line in fig. 1 and a diameter of a straight cylinder portion after cylindrical grinding of 300mm was prepared.

Using this single crystal pulling apparatus 1, after the processes of steps S1, S11, S2, and S3 are performed in the multiple pulling method of the above embodiment shown in fig. 5, the solidification power, input power, and melting power setting process (step S12) based on the melting power are not performed, but the processes after the solidification process (step S4) are performed, and a plurality of single crystal silicon SMs are produced, and the solidification rate of silicon melt M in the solidification process of the 1 st time is confirmed. In comparative example 1, the reference values of the solidification, injection, and melting steps shown in table 1 were used as the power of the heater 23 in the solidification, injection, and melting steps.

Thereafter, the same experiment was performed by exchanging the quartz crucible 221 of the same single crystal pulling apparatus 1, and a total of 50 experiments were performed.

< example 1 >

After the processes of steps S1, S11, S2 and S3 were performed in the multi-pulling method of the above embodiment using the single crystal pulling apparatus 1 similar to that of comparative example 1, the solidification electric power, the input electric power and the melting electric power setting step (step S12) were further performed based on the liquid application electric power, and the electric power of the heater 23 was calculated based on the formula (1). Then, the solidification step (step S4), the charging step (step S5), and the melting step (step S6) were performed at the calculated power, and the processes after step S7 were further performed to produce a plurality of silicon single crystals SM, and the solidification rate of silicon melt M in the 1 st solidification step was confirmed. In example 1, the values shown in table 1 were used as the reference values for the curing, charging, and melting steps in formula (1).

Thereafter, the same experiment was performed by exchanging the quartz crucible 221 of the same single crystal pulling apparatus 1, and the total 34 times of experiment results were obtained.

< comparative example 2 >

A single crystal pulling apparatus 1 for manufacturing a single crystal silicon SM having a split heater 232 shown by a two-dot chain line in fig. 1 and a straight cylinder portion having a diameter of 300mm after cylindrical grinding was prepared.

The same treatment as in comparative example 1 was carried out using this single crystal pulling apparatus 1, and the solidification rate of silicon melt M in the 1 st solidification step was confirmed. In comparative example 2, as the power of the split heater 232 in the curing step, similarly to the curing step reference value shown in table 1, a value set so that the reference value becomes smaller as the number of steps from the curing step to the melting step increases is used. As the power of the split heater 232 at the time of the charging step and the melting step, the same value regardless of the number of repetitions of the steps from the solidification step to the melting step and a value larger than the solidification step reference value were used, as in the charging and melting step reference values shown in table 1.

Thereafter, the same experiment was performed by exchanging the quartz crucible 221 of the same single crystal pulling apparatus 1, and a total of 16 experiments were performed.

< example 2 >

The same treatment as in example 1 was carried out using the single crystal pulling apparatus 1 same as that of comparative example 2, and the solidification rate of the silicon melt M in the 1 st solidification step was confirmed. In example 2, in the solidification power, input power, and melting power setting step based on the liquid application power, the power of the separate heater 232 was calculated based on the formula (2). In example 2, the same values as the respective reference values of comparative example 2 were adopted as the reference values of the solidification, charging, and melting process in formula (2).

Thereafter, the same experiment was performed by exchanging the quartz crucible 221 of the same single crystal pulling apparatus 1, and the total of 12 times of experiment results were obtained.

< evaluation >

The curing rates for comparative example 1 and example 1 are shown in fig. 7, and the curing rates for comparative example 2 and example 2 are shown in fig. 8.

As shown in fig. 7 and 8, it can be confirmed that: the curing speed of examples 1 and 2 was less varied than that of comparative examples 1 and 2. It can thus be confirmed that: by performing the solidification power setting step based on the power at the time of deposition, variation in the solidification rate of the surface of the silicon melt M can be suppressed.

In particular, it was confirmed that: the variation in the direction in which the solidification rate increases is suppressed, and the problem that the solidification proceeds to an extent more than expected and the quartz crucible 221 is damaged can be suppressed.

Claims

1. A raw material supply method, characterized in that: the method for supplying a raw material for charging a solid raw material into a silicon melt in a quartz crucible when manufacturing single-crystal silicon by a pulling method using 1 quartz crucible, comprises the steps of:

a solidification step of adjusting power of a heater for heating the quartz crucible to solidify the surface of the silicon melt;

a charging step of charging the solid material to the solidified portion of the surface; and

a melting step of melting the solidified portion and the solid raw material;

wherein the solidification step is performed by adjusting the power of the heater in the solidification step based on the power value of the heater in the conventional process of depositing the seed crystal in the silicon melt during the production of the silicon single crystal.

2. The raw material supply method according to claim 1, characterized in that: the charging step is performed by adjusting the power of the heater in the charging step based on the power value of the heater in the conventional process of producing single crystal silicon.

3. The raw material supply method according to claim 1 or 2, characterized in that: the melting step is performed by adjusting the power of the heater in the melting step based on the power value of the heater in the conventional process of producing single crystal silicon.

4. The raw material supply method according to claim 1, characterized in that: in the curing step, when the power of the heater in the liquid applying step is larger than a reference value of the liquid applying step, the power of the heater in the curing step is made larger than the reference value of the curing step.

5. The raw material supply method according to claim 1 or 4, characterized in that: in the curing step, when the power of the heater in the liquid applying step is smaller than a reference value for the liquid applying step, the power of the heater in the curing step is made smaller than the reference value for the curing step.

6. The raw material supply method according to claim 1, characterized in that: the curing step is to adjust the power of the heater based on the following formula (1):

A=B-α×(C-D)　… (1)

a: the adjusted power of the heater;

b: a curing process reference value;

c: a liquid deposition process reference value;

d: the power of the heater when the liquid applying process is carried out;

α, parameters for adjustment.

7. The raw material supply method according to claim 6, characterized in that: the solidifying step, the charging step and the melting step are repeated for the same number of times of 2 or more,

the curing process reference value is set to a value that decreases as the number of repetitions increases.

8. A method for manufacturing a silicon single crystal, characterized by comprising: the method for manufacturing a silicon single crystal is a method for continuously manufacturing a plurality of silicon single crystals by a pulling method using 1 quartz crucible, and comprises the steps of:

a seed crystal deposition step of depositing a seed crystal in a silicon melt;

a growing step of pulling up the seed crystal to grow a silicon single crystal; and

the method for supplying a raw material according to any one of claims 1 to 7, wherein the step of refilling the solid raw material for producing single-crystal silicon of 2 nd or later is performed in refilling the silicon melt in the quartz crucible,

wherein the solidification step in the reloading step is performed by adjusting the power of the heater in the solidification step based on the power value of the heater when the liquid deposition step is performed in the production of any one of the silicon single crystals using the same quartz crucible.

9. The method for manufacturing a silicon single crystal according to claim 8, comprising the steps of:

an initial melt generation step of heating a quartz crucible containing a solid raw material to generate a silicon melt; and

an additional charging step of additionally charging a solid raw material into the silicon melt in the quartz crucible by the raw material supply method according to any one of claims 1 to 7,

wherein the solidification step in the additional filling step is performed by adjusting the power of the heater in the solidification step based on the power value of the heater when the liquid deposition step is performed in the production of the silicon single crystal just before the use of another quartz crucible.

10. A method for manufacturing a silicon single crystal, characterized by comprising: the method for producing 1 silicon single crystal by a Czochralski method using 1 quartz crucible comprises the steps of:

an initial melt generation step of heating a quartz crucible containing a solid raw material to generate a silicon melt;

an additional charging step of additionally charging a solid raw material into the silicon melt in the quartz crucible by the raw material supply method according to any one of claims 1 to 7;

a seed crystal deposition step of depositing a seed crystal in a silicon melt; and

a growing step of pulling up the seed crystal to grow the single crystal silicon,

11. The method for producing a silicon single crystal according to any one of claims 8 to 10, characterized in that: the method further comprises a liquid deposition power adjustment step between the liquid deposition step and the incubation step, the liquid deposition power adjustment step comprising: adjusting the power of the heater to make the temperature of the silicon melt reach a predetermined temperature.