CN113005509A

CN113005509A - Method for manufacturing silicon single crystal ingot

Info

Publication number: CN113005509A
Application number: CN202011111507.6A
Authority: CN
Inventors: 琴浦荣一郎
Original assignee: Sumco Corp
Current assignee: Sumco Corp
Priority date: 2019-12-20
Filing date: 2020-10-16
Publication date: 2021-06-22
Also published as: JP7184029B2; JP2021098622A

Abstract

Provided is a method for producing a single crystal silicon ingot, wherein the production yield can be improved by suppressing the occurrence of dislocation in the single crystal silicon ingot by suppressing the roughness of the inner surface of a quartz crucible in a CZ method using a multi-pulling method. The method for producing a silicon single crystal ingot of the present invention is characterized by comprising a magnetic field application step of cutting a pulled silicon single crystal ingot from a silicon melt and applying a magnetic field to the silicon melt remaining in a quartz crucible in a CZ method using a multi-pulling method.

Description

Method for manufacturing silicon single crystal ingot

Technical Field

The present invention relates to a method for producing a silicon single crystal ingot by the Czochralski (CZ) method, and more particularly, to a so-called multi-pulling method for continuously producing a plurality of silicon single crystal ingots using the same quartz crucible.

Background

A typical method for producing a single crystal silicon ingot is the czochralski method (CZ method). In the production of a silicon single crystal ingot by the CZ method, a silicon raw material such as polycrystalline silicon is filled into a quartz crucible, and the silicon raw material is heated and melted in a chamber to form a silicon melt. Then, the seed is brought into contact with the silicon melt in the quartz crucible, and the seed and the quartz crucible are rotated in a predetermined direction while the seed is gradually raised, thereby growing a silicon single crystal ingot below the seed.

As an application of this CZ method, a multi-pulling method is known. In the multi-pulling method, after a first single crystal silicon ingot is pulled up, a silicon raw material is additionally supplied into the same quartz crucible to be melted, and a second single crystal silicon ingot is pulled up from the obtained silicon melt. By repeating the raw material supply step and the pulling step, a plurality of single crystal silicon ingots were produced using one quartz crucible. According to the multi-pulling method, the original cost of the quartz crucible of each ingot can be reduced. Further, the frequency of disassembling the chamber and replacing the quartz crucible can be reduced, and therefore, the operation efficiency can be improved.

Patent document 1 describes that when two or more single crystal silicon ingots are pulled by the multi-pulling method, the ratio V/G of the pulling rate V with respect to the temperature gradient G of the solid-liquid interface is appropriately controlled, whereby the two or more single crystal silicon ingots have desired crystal qualities. Further, patent document 1 describes that by performing each pulling while applying a magnetic field, convection of the silicon melt in the crucible is controlled, and the convection of the silicon melt is stabilized, so that a single crystal can be grown with a good shape of the crystal growth interface.

Patent document 1: japanese patent laid-open No. 2005-187244.

However, in the CZ method using the multi-pulling method, since the same quartz crucible is continuously used, there is a problem that the single crystal is dislocated due to the roughness of the inner surface of the quartz crucible. That is, the quartz crucible before use has Silica (SiO) as a whole₂) However, in the process of growing a single crystal, a crystallized layer called cristobalite is locally formed on the inner surface of the quartz crucible due to exposure to the high-temperature silicon melt. The cristobalite is easily peeled off from the inner surface of the quartz crucible and is insoluble in a silicon melt. Therefore, when a part of cristobalite formed on the inner surface of the quartz crucible is peeled off and introduced into the silicon melt during the growth of a single crystal, the part of cristobalite reaches the solid-liquid interface of the growing single crystal silicon ingot, and dislocation of the single crystal occurs. The dislocation portion of the silicon single crystal ingot is not a product, and thus the yield is lowered.

In patent document 1, in the CZ method using the multi-pulling method, attention is paid to the crystal quality of a V region where Vacancy (Vacancy) predominates, an I region where Interstitial Silicon (Interstitial Silicon) predominates, and a defect-free n (neutral) region located therebetween. However, the problem of dislocation of the single crystal caused by the roughness of the inner surface of the quartz crucible is not concerned at all and is not solved.

Disclosure of Invention

In view of the above problems, an object of the present invention is to provide a method for producing a single crystal silicon ingot, which can improve the yield by suppressing the formation of dislocations in the inner surface of a quartz crucible in the CZ method using the czochralski method.

The present inventors have made intensive studies to solve the above problems and have obtained the following findings. That is, it was evaluated that the ratio of the rough region (the region of cristobalite and the region of a quartz crucible recessed by peeling off cristobalite) of the inner surface of the quartz crucible after pulling the inner surface a plurality of times by the multi-pulling method becomes larger as it is farther from the upper end surface of the quartz crucible. That is, it was found that the inner surface of the quartz crucible had a larger proportion of the region having roughness in the region closer to the bottom of the crucible than the region near the upper end. This is considered to be because the inner surface near the bottom of the quartz crucible is always exposed to the residual silicon melt after each pulling.

Therefore, the inventors of the present invention have obtained an idea of suppressing the roughness of the inner surface in the vicinity of the bottom of the quartz crucible by controlling the state of the remaining silicon melt not during the growth of the single crystal (pulling each time) but after each pulling. Specifically, the inventors of the present invention have found that, after slicing a pulled silicon single crystal ingot from a silicon melt, a magnetic field is applied to the silicon melt remaining in a quartz crucible to suppress convection of the remaining silicon melt, thereby suppressing a reaction between the inner surface of the quartz crucible and the silicon melt. It was found that, more preferably, after the silicon single crystal ingot is sliced from the silicon melt, the reaction between the inner surface of the quartz crucible and the silicon melt can be further suppressed by setting the rotation speed of the quartz crucible to a low value to suppress the convection of the silicon melt.

The main aspects of the present invention accomplished based on the above findings are as follows.

(1) A method for manufacturing a silicon single crystal ingot by repeating a step of filling a silicon raw material into a quartz crucible located in a main cavity, a step of heating and melting the silicon raw material to form a silicon melt in the quartz crucible, a step of pulling a silicon single crystal ingot from the silicon melt, a step of cutting the silicon single crystal ingot from the silicon melt and raising the silicon single crystal ingot in the main cavity to be accommodated in a pulling cavity above the main cavity, and a step of taking out the silicon single crystal ingot from the pulling cavity.

(2) In the method for producing a silicon single crystal ingot according to item (1), at least the magnetic field applying step is performed during a period from when the silicon single crystal ingot is sliced from the silicon melt to when the silicon single crystal ingot is stored in the pulling chamber.

(3) In the method for producing a single crystal silicon ingot according to the item (1) or (2), the magnetic field is either a horizontal magnetic field that forms a horizontal magnetic field distribution with respect to the silicon melt or a cusp magnetic field that forms a cusp-type magnetic field distribution with respect to the silicon melt.

(4) In the method for producing a single crystal silicon ingot according to item (3), the magnetic field is a horizontal magnetic field having a horizontal magnetic field distribution with respect to the silicon melt, and the magnetic field strength is 1000G to 5000G.

(5) In the method for producing a single crystal silicon ingot according to item (3), the magnetic field is a cusp magnetic field having a cusp-type magnetic field distribution with respect to the silicon melt, and the magnetic field strength is 300G to 1500G.

(6) The method of producing a silicon single crystal ingot according to any one of (1) to (5), wherein the rotation speed of the quartz crucible is set to 0.5rpm or more and 2.0rpm or less after the silicon single crystal ingot is sliced from the silicon melt.

Effects of the invention

According to the method for manufacturing a single crystal silicon ingot of the present invention, in the CZ method using the czochralski method, the roughness of the inner surface of the quartz crucible is suppressed, whereby dislocation of the single crystal silicon ingot can be suppressed, and the yield can be improved.

Drawings

FIG. 1 is a cross-sectional view along a pulling axis X schematically showing the structure of a silicon single crystal pulling apparatus 100 used in one embodiment of the present invention.

Fig. 2(a) to (H) are cross-sectional views schematically showing steps of the multi-pulling method.

Fig. 3 is a flowchart illustrating a method for manufacturing a single crystal silicon ingot according to an embodiment of the present invention.

FIG. 4 is a graph showing the surface roughness of the examples.

Detailed Description

(silicon Single Crystal pulling apparatus)

First, the structure of a silicon single crystal pulling apparatus 100 used in an embodiment of the present invention will be described with reference to fig. 1.

The silicon single crystal pulling apparatus 100 includes a main chamber 10, a pulling chamber 11, a crucible 16, a spindle 18, a spindle driving mechanism 20, a cylindrical heat insulator 22, a cylindrical heater 24, a cylindrical heat insulator 26, a seed chuck 28, a pulling wire 30, a wire elevating mechanism 32, and a pair of electromagnets 34.

The main chamber 10 is a bottomed cylindrical-shaped chamber that accommodates the crucible 16 therein. The traction chamber 11 has the same central axis as the main chamber 10, is provided above the main chamber 10, and is a cylindrical chamber having a smaller diameter than the main chamber 10. A gate valve 12 is provided between the main chamber 10 and the traction chamber 11, and the spaces in the main chamber 10 and the traction chamber 11 are communicated with each other and segregated by opening and closing the gate valve 12. A gas inlet 13 for introducing an inert gas such as Ar gas into the main chamber 10 is provided above the draft chamber 11. Further, at the bottom of the main chamber 10, a gas discharge port 14 is provided for discharging the gas in the main chamber 10 by sucking the gas by a vacuum pump not shown in the figure.

The crucible 16 is disposed in the center of the main chamber 10 and contains the silicon melt M. The crucible 16 has a double structure of a quartz crucible 16A and a graphite crucible 16B. The quartz crucible 16A directly supports the silicon melt M on the inner surface. The graphite crucible 16B supports the quartz crucible 16A on the outer side of the quartz crucible 16A. As shown in FIG. 1, the upper end of the quartz crucible 16A is higher than the upper end of the graphite crucible 16B, that is, the upper end portion of the quartz crucible 16A protrudes from the upper end of the graphite crucible 16B.

The main shaft 18 vertically penetrates the bottom of the main chamber 10 and supports the crucible 16 at the upper end. The spindle drive mechanism 20 rotates and moves up and down the crucible 16 via the spindle 18.

The heat insulator 22 is provided above the crucible 16 so as to surround the silicon single crystal ingot I pulled from the silicon melt M. Specifically, the heat insulator 22 includes a truncated cone-shaped shield body 22A, an inner flange portion 22B provided to extend horizontally from a lower end portion of the shield body 22A toward (inward of) the pull axis X, and an outer flange portion 22C provided to extend horizontally from an upper end portion of the shield body 22A toward (outward of) the cavity side, and the outer flange portion 22C is fixed to the heat insulator 26. The heat insulator 22 functions to control the temperature gradient in the direction of the pulling axis X in the central portion and the outer peripheral portion of the single crystal silicon ingot I by adjusting the amount of high-temperature radiant heat incident on the ingot I being grown from the silicon melt M, the heater 24, and the side wall of the crucible 16 or adjusting the amount of heat diffused in the vicinity of the crystal growth interface.

A cylindrical heater 24 is located at a position surrounding the crucible 16 within the main chamber 10. The heater 24 is a resistance heating type heater made of carbon, melts the silicon raw material charged into the crucible 16 to form the silicon melt M, and further heats the formed silicon melt M to maintain it.

The cylindrical heat insulator 26 is provided along the inner surface of the main chamber 10 below the upper end of the heat insulator 22 and apart from the outer peripheral surface of the heater 24. The heat insulator 26 exerts a heat retaining effect on a region in the chamber 10, particularly, below the heat insulator 22, and has a function of easily retaining the silicon melt M in the crucible 16.

A pulling wire 30, which holds a seed chuck 28 holding a seed S at a lower end, is arranged coaxially with the main shaft 18 above the crucible 16, and a wire lifting mechanism 32 rotates and lifts the pulling wire 30 and the main shaft 18 in opposite directions or in the same direction at a predetermined speed.

The pair of electromagnets 34 are located at left-right symmetrical positions with respect to the pulling axis X within the height range of the outer side of the main chamber 10 including the crucible 16. By passing a current through the windings of the pair of electromagnets 34, a horizontal magnetic field having a horizontal magnetic field distribution with respect to the silicon melt M can be generated. In addition, the magnetic field strength can be controlled by the magnitude of the current flowing through the winding.

Fig. 1 shows a pair of electromagnets 34 that generate a horizontal magnetic field, but instead of this, an electromagnet that generates a cusp magnetic field that forms a cusp-type magnetic field distribution with respect to the silicon melt M may be arranged. The configuration of the electromagnet that generates the cusp magnetic field is done conventionally.

(method for producing a silicon single crystal ingot by the Czochralski method)

The method for manufacturing a single crystal silicon ingot according to an embodiment of the present invention can be suitably implemented using the silicon single crystal pulling apparatus 100 described above. Here, a method for manufacturing a single crystal silicon ingot according to an embodiment of the present invention will be described with reference to fig. 2 and 3.

Step S1: raw Material filling Process

First, as shown in fig. 2(a), a silicon raw material N such as a polycrystalline silicon ingot is filled into a quartz crucible 16A located in the main chamber 10. At this time, the gate valve 12 is opened, and an inert gas atmosphere such as Ar gas is maintained in the main chamber 10 and the pull chamber 11 under reduced pressure. Further, the crucible 16 is located below within the main chamber 10 such that the silicon feedstock does not contact the insulator 22.

Step S2: raw Material melting Process

Next, as shown in fig. 2(B), the silicon raw material in the crucible 16 is heated and melted by the heater 24, and a silicon melt M is formed in the quartz crucible 16A. Thereafter, the crucible 16 is raised to the pulling start position. The "raw material melting step" is defined as a period from the time when heating by the heater 24 is started to the time when the crucible is completely raised.

Step S3: liquid deposition Process

Subsequently, the pulling wire 30 is lowered by the wire elevating mechanism 32 to deposit the seed crystal S into the silicon melt M.

[ steps S4 to S7: crystal growing Process

Subsequently, as shown in fig. 2(C), the silicon single crystal ingot I is pulled from the silicon melt M. Specifically, the crucible 16 and the pulling wire 30 are rotated in a predetermined direction, and the pulling wire 30 is pulled upward, so that the single crystal silicon ingot I is grown below the seed S. Further, as the ingot I is grown, the amount of the silicon melt M is decreased, but the crucible 16 is raised to maintain the level of the melt surface. The "crystal growth step" in the present specification is defined as a period from the time when the raising of the wire rod 30 is started to the time when the growth of the ingot I is completed (the time when the ingot I is cut from the silicon melt M).

In the crystal growth step, first, in order to make the single crystal dislocation-free, the seed is narrowed (reduced in diameter) by the punch method (ダッシュ method), and a neck portion I is formed_n(step S4). Next, shoulder I is grown to obtain an ingot of the necessary diameter_s(step S5), the body part I is grown by making the diameter constant when the silicon single crystal has a desired diameter_b(step S6). A body part I_bAfter the growth to a predetermined length, the single crystal is cut from the silicon melt M without dislocation and the tail is formed_t(step S7).

Step S8: procedure for raising ingot in Main Cavity

Next, as shown in fig. 2(D), the pulled silicon single crystal ingot I is sliced from the silicon melt M, raised in the main chamber 10, and accommodated in the pulling chamber 11 above the main chamber 10. In the present specification, the "ingot raising step in the main chamber" is defined as a period from a time when the single crystal silicon ingot I is sliced from the silicon melt M to a time when the entire single crystal silicon ingot I moves into the pulling chamber 11 and the gate valve 12 is closed. The pulling rate in this step is determined as appropriate in accordance with the quality characteristics of the crystal to be obtained.

Step S9: cooling Process in traction Chamber

Next, the silicon single crystal ingot I is placed in the pulling chamber 11 with the gate valve 12 closed, preferably, and cooled down to the take-out temperature of 500 ℃ or lower.

Step S10: ingot taking-out Process

Subsequently, the cooled silicon single crystal ingot I is taken out from the pulling chamber 11. Specifically, in a state where the gate valve 12 is closed, the pulling chamber 11 is lifted and rotated, and the ingot I is lowered in the pulling chamber 11 and is stacked on the conveyance carriage. Through the above steps, one single crystal silicon ingot I is produced.

Step S11: based on multi-pulling method

The present embodiment relates to a multi-pulling method of pulling up a plurality of single crystal silicon ingots I using the same quartz crucible 16A. Therefore, after the first single crystal silicon ingot I is taken out, the process returns to step S1 again to perform the next pulling, and the processes of steps S1 to S10 are performed again to produce a second single crystal silicon ingot I as shown in fig. 2(E), (F), (G), and H). By repeating these steps, the nth single crystal silicon ingot I is produced. n is an integer of 2 or more, and is not particularly limited. When the next pulling-up is not performed in step S11, the operation based on the same quartz crucible 16A is ended, and the crucible is replaced.

In the present embodiment, after the first to (n-1) th crystal growth steps (S4 to S7) are completed, the silicon melt M in the quartz crucible 16A needs to be maintained until the next step of filling the silicon raw material (S1) required for the crystal growth step is performed. Thus, the heating of the silicon melt M is continued without stopping the heater 24 in the ingot raising step (S8), the cooling step (S9) in the pulling chamber, and the ingot removing step (S10) in the main chamber from the first time to the (n-1) th time. Further, in the second to nth raw material filling steps (S1), the heating of the silicon melt M is continued without stopping the heater 24.

[ application of magnetic field ]

In the present embodiment, after the raw material melting step S2 is completed, a current is preferably passed through the windings of the pair of electromagnets 34 to apply a horizontal magnetic field to the silicon melt M. In this state, by proceeding from the liquid application step S3 to the crystal growth steps S4 to S7, thermal convection of the silicon melt M is suppressed during growth of a single crystal, and the temporal variation in the temperature in the vicinity of the melt surface (the temperature of the solid-liquid interface in crystal growth) is reduced, so that a single crystal silicon ingot in which the occurrence of dislocations and defects is suppressed can be easily obtained. The intensity of the horizontal magnetic field in the crystal growth step is not particularly limited, but it is preferable that the measured value at the center position of the crucible passing through the center of the magnetic field is 2000G to 5000G. When the intensity of the horizontal magnetic field in the crystal growth step is less than 2000G, it is difficult to control the convection of the silicon melt M in the vicinity of the solid-liquid interface, and a magnetic field exceeding 5000G is difficult to be generated due to the restriction of the magnetic field generator.

[ magnetic field application Process after ingot slitting ]

Further, in the present embodiment, it is important to perform a magnetic field applying step of applying a horizontal magnetic field to the silicon melt M remaining in the quartz crucible 16A after the single crystal silicon ingot I is cut from the silicon melt M. That is, the magnetic field applying step is performed during a certain period between the ingot raising step (S8) in the main cavity, the cooling step (S9) in the pulling cavity, and the ingot removing step (S10). Specifically, a horizontal magnetic field is applied so that the center of the magnetic field acts on the remaining silicon melt M. This suppresses convection of the remaining silicon melt M, suppresses a reaction between the inner surface of the quartz crucible 16A and the silicon melt M, and suppresses roughness of the inner surface of the quartz crucible. As a result, dislocation of the single crystal silicon ingot I produced in the next crystal growing step can be suppressed, and the yield can be improved.

From the viewpoint of more sufficiently suppressing the roughness of the inner surface of the quartz crucible, it is preferable that at least the magnetic field applying step is performed during the period from when the single crystal silicon ingot I is sliced from the silicon melt M to when it is accommodated in the pulling chamber 11, that is, during the ingot raising step (S8) in the main chamber. In this case, the horizontal magnetic field may be applied to the ingot raising step (S8) in the main chamber continuously without cutting off the horizontal magnetic field applied to the crystal growing step (S4 to S7).

Whether or not to apply the horizontal magnetic field in the cooling step (S9) in the pulling chamber is not particularly limited, but it is preferable to apply the horizontal magnetic field in this step from the viewpoint of more sufficiently suppressing the roughness of the inner surface of the quartz crucible.

Whether or not the horizontal magnetic field is applied in the ingot removing step (S10) is not particularly limited. In the case where it is desired to more sufficiently suppress the roughness of the inner surface of the quartz crucible, the horizontal magnetic field can be applied in this step. However, since the conveyance carriage is positioned near the main chamber 10 in this step, it is preferable not to apply the horizontal magnetic field in this step from the viewpoint of safety of the work.

The intensity of the horizontal magnetic field in the magnetic field application step is not particularly limited, and from the viewpoint of sufficiently obtaining the effect of suppressing the roughness of the inner surface of the quartz crucible, the measured value of the crucible center position through which the magnetic field center passes is preferably 1000G or more, more preferably 2000G or more. Further, the intensity of the horizontal magnetic field in the magnetic field applying step is preferably 5000G or less as a measured value of the central position of the crucible through which the center of the magnetic field passes, because of the restriction of the magnetic field generating device.

The case of applying the horizontal magnetic field was described above, but the magnetic field applied in the magnetic field applying step performed during any of the periods from the liquid applying step S3 to the crystal growing step S4 to S7, the ingot raising step (S8) in the main chamber, the cooling step (S9) in the pulling chamber, and the ingot removing step (S10) may be a cusp magnetic field having a cusp-type magnetic field distribution with respect to the silicon melt M instead of the horizontal magnetic field.

That is, after the raw material melting step S2 is completed, the cusp magnetic field may be applied to the silicon melt M. In this state, by proceeding from the liquid application step S3 to the crystal growth steps S4 to S7, thermal convection of the silicon melt M is suppressed during growth of a single crystal, and the temporal variation in the temperature in the vicinity of the melt surface (the temperature of the solid-liquid interface in crystal growth) is reduced, so that a single crystal silicon ingot in which the occurrence of dislocations and defects is suppressed can be easily obtained. The intensity of the horizontal magnetic field in the crystal growth step is not particularly limited, and it is preferable that the measured value at a position crossing the crucible wall is 300G or more and 1500G or less. When the intensity of the cusp magnetic field in the crystal growth step is less than 300G, it is difficult to control the convection of the silicon melt M in the vicinity of the solid-liquid interface, and a magnetic field exceeding 1500G is difficult to generate due to the restriction of the magnetic field generator.

Further, it is important to perform a magnetic field applying step of applying a cusp magnetic field to the silicon melt M remaining in the quartz crucible 16A after the single crystal silicon ingot I is cut from the silicon melt M. That is, the magnetic field applying step is performed during any one of the ingot raising step (S8) in the main chamber, the cooling step (S9) in the traction chamber, and the ingot removing step (S10). This can suppress convection of the remaining silicon melt M, suppress a reaction between the inner surface of the quartz crucible 16A and the silicon melt M, and suppress roughness of the inner surface of the quartz crucible. As a result, dislocation of the single crystal silicon ingot I produced in the next crystal growing step can be suppressed, and the yield can be improved. The presence or absence of the magnetic field application in each of steps S8, S9, and S10 is the same as in the case of the horizontal magnetic field.

The intensity of the cusp magnetic field in the magnetic field application step is not particularly limited, and from the viewpoint of sufficiently suppressing the roughness of the inner surface of the quartz crucible, it is preferable that the measured value of the position crossing the crucible wall is 300G or more. Further, it is preferable that the intensity of the cusp magnetic field in the cooling step is 1500G or less at a position across the crucible wall due to the limitation of the magnetic field generating means.

In addition, when n single crystal silicon ingots I are produced using the same quartz crucible 16A and thereafter the crucible is replaced, the magnetic field application step may be performed during any one of steps S8, S9, and S10 from the first time to the (n-1) th time, and the application of the magnetic field is not necessarily performed after the n-th step S8. This is because the magnetic field application step is intended to suppress dislocation in the crystal growth step following the magnetic field application step, and there is no crystal growth step using the same quartz crucible after the nth step S8.

[ rotation of crucible ]

After slicing the silicon single crystal ingot I from the silicon melt M, the rotation speed of the crucible is preferably lower than that in the crystal growing step, and is preferably 0.5rpm to 2.0 rpm. By setting the rotation speed of the crucible to 2.0rpm or less, convection of the remaining silicon melt M is suppressed, reaction between the inner surface of the quartz crucible 16A and the silicon melt M can be suppressed, and roughness of the inner surface of the quartz crucible can be suppressed. As a result, dislocation of the single crystal silicon ingot I produced in the next crystal growing step can be suppressed, and the yield can be improved. When the crucible rotation speed is less than 0.5rpm, it is difficult to make the heat load from the heater 24 uniform to the quartz crucible 16A, and it is difficult to perform stable crystal growth in the next pulling.

From the viewpoint of more sufficiently obtaining the effect of suppressing the roughness of the inner surface of the quartz crucible, it is preferable that the rotation speed of the crucible is set to 0.5rpm or more and 2.0rpm or less as described above at least in the ingot raising step (S8) in the main chamber during the period from the time when the single crystal silicon ingot I is sliced from the silicon melt M to the time when it is accommodated in the pulling chamber 11.

The rotation speed of the crucible in the cooling step (S9) in the pulling chamber is not particularly limited, but in this step, it is preferable to set the rotation speed of the crucible to 0.5rpm or more and 2.0rpm or less, from the viewpoint of more sufficiently obtaining the effect of suppressing the roughness of the inner surface of the quartz crucible.

The rotation speed of the crucible in the ingot removal step (S10) is not particularly limited, but in this step, the rotation speed of the crucible is preferably set to 0.5rpm to 2.0rpm in order to more sufficiently obtain the effect of suppressing the roughness of the inner surface of the quartz crucible.

When n single crystal silicon ingots I are produced using the same quartz crucible 16A and thereafter the crucible is replaced, the rotation speed of the crucible may be set as described above during any one of steps S8, S9, and S10 from the first time to the (n-1) th time, and the rotation speed of the crucible is not particularly limited after step S8 of the nth time. This is because, as described above, the rotational speed of the crucible is set in order to suppress dislocation in the next crystal growing step, and there is no crystal growing step using the same quartz crucible after the nth step S8.

Examples

With the silicon single crystal pulling apparatus having the structure shown in fig. 1, a single crystal silicon ingot was produced by repeating the multi-pulling method from the raw material filling step S1 to the ingot taking-out step S10 shown in fig. 3 twice.

First, a quartz crucible is filled with a silicon material (polycrystalline silicon mass), and heated and melted to form a predetermined amount of a silicon melt. Thereafter, a horizontal magnetic field was applied to the silicon melt, a crystal growth step was performed from the liquid deposition step, and the single crystal silicon ingot was sliced from the silicon melt at a time when the single crystal pulling rate was 80%, thereby producing a first single crystal silicon ingot (diameter 200 mm). At this time, the intensity of the horizontal magnetic field at the center of the crucible through which the center of the magnetic field passes was 3000G, and the rotation speed of the crucible was 5.0 rpm.

After the first single crystal silicon ingot is sliced from the silicon melt, the main chamber is raised and accommodated in the pulling chamber. During the ingot raising step, a horizontal magnetic field was applied to the silicon melt remaining in the quartz crucible so that the horizontal magnetic field intensity at the crucible center position through which the magnetic field center passes was as shown in table 1. That is, in comparative examples, the application of the horizontal magnetic field was stopped at the time when the silicon single crystal ingot was sliced from the silicon melt, and in invention examples 1 to 5, the horizontal magnetic field was also applied to the remaining silicon melt in the ingot raising step following the crystal growing step, and the application of the horizontal magnetic field was stopped at the time when the main valve was closed. And then, cooling the monocrystalline silicon ingot in the traction cavity to below 350 ℃, and taking out the monocrystalline silicon ingot from the traction cavity. In comparative example and invention example 5, after the ingot raising step, the rotation of the crucible was continued while maintaining the rotation speed of the crucible in the crystal growth step at 5.0rpm as shown in table 1, and in invention examples 1 to 4, the rotation speed of the crucible was set to be lower than that in the crystal growth step and the rotation of the crucible was continued as shown in table 1.

Next, a silicon raw material was additionally charged into the quartz crucible so as to have the same amount of silicon melt as that in the growth of the first single crystal silicon ingot, and the silicon raw material was heated and melted to form a silicon melt. Thereafter, the rotation speed of the crucible was set to 5.0rpm, a horizontal magnetic field was applied to the silicon melt, and the crystal growth step was performed from the liquid deposition step to produce a second single crystal silicon ingot (diameter 200 mm). At this time, the intensity of the horizontal magnetic field at the center of the crucible through which the center of the magnetic field passes was 3000G.

After the second silicon single crystal ingot was sliced, the application of the magnetic field was stopped, and after step S8 in fig. 3 was performed, the second silicon single crystal ingot was taken out from the pulling chamber.

(evaluation of surface roughness)

After the above-described step, the quartz crucible was recovered from the chamber, and the inner surface was sequentially observed in the longitudinal direction from the upper end surface to the bottom of the crucible, to determine the relationship between the distance from the upper end surface and the surface roughness. Here, the "surface roughness" of a position 50mm away from the upper end face is defined as a ratio of a total area of a cristobalite region and a region in which cristobalite is peeled and recessed with respect to an area of a region 50mm in a vertical direction (25 to 75mm away from the upper end face) x 50mm in a horizontal direction, which is observed with a position 50mm away from the upper end face as a center. The surface roughness at positions at distances of 100mm, 150mm, 200mm, 250mm and 300mm from the upper end face is also defined in the same manner. The relationship between the distance from the upper end face and the surface roughness at each level is shown in fig. 4, and the surface roughness at 300mm from the upper end face is also shown in table 1.

TABLE 1

As shown in fig. 4 and table 1, in inventive examples 1 to 5 in which a magnetic field was applied in the ingot raising step in the main chamber, the surface roughness was reduced as compared with the comparative example in which a magnetic field was not applied in the step. In particular, in the step, the surface roughness can be significantly reduced in invention examples 2 to 4 in which the horizontal magnetic field strength is set to 2000G or more and the crucible rotation speed is set to 0.5rpm or more and 2.0rpm or less.

Industrial applicability

According to the method for manufacturing a single crystal silicon ingot of the present invention, in the CZ method using the czochralski method, the roughness of the inner surface of the quartz crucible is suppressed, thereby suppressing dislocation of the single crystal silicon ingot and improving the yield.

Description of the reference numerals

100 silicon single crystal pulling apparatus

10 main chamber

11 traction chamber

12 gate valve

13 gas inlet

14 gas outlet

16 crucible

16A quartz crucible

16B graphite crucible

18 spindle

20 spindle driving mechanism

22 insulation

22A shield body

22B inner flange

22C outer flange

24 heater

26 heat insulator

28 crystal seed chuck

30 pulling wire

32 wire lifting mechanism

34 electromagnet

S crystal seed

N silicon feedstock

M silicon melt

I single crystal silicon ingot

I_nNeck part

I_sShoulder part

I_bBody part

I_tTail part

X pulls the shaft.

Claims

1. A method for producing a silicon single crystal ingot by repeating a step of filling a quartz crucible located in a main chamber with a silicon raw material, a step of heating and melting the silicon raw material to form a silicon melt in the quartz crucible, a step of pulling up a silicon single crystal ingot from the silicon melt, a step of slicing the silicon single crystal ingot from the silicon melt and raising the silicon single crystal ingot in the main chamber to be accommodated in a pulling chamber above the main chamber, and a step of taking out the silicon single crystal ingot from the pulling chamber, wherein a CZ method of pulling up a plurality of silicon single crystal ingots is performed using the same quartz crucible,

the method comprises a magnetic field applying step of cutting the silicon single crystal ingot from the silicon melt and applying a magnetic field to the silicon melt remaining in the quartz crucible.

2. The method of manufacturing a single crystal silicon ingot according to claim 1, wherein the silicon ingot is a silicon ingot,

and performing at least the magnetic field applying step during a period from when the single crystal silicon ingot is sliced from the silicon melt to when the single crystal silicon ingot is accommodated in the pulling chamber.

3. The method of manufacturing a single crystal silicon ingot according to claim 1 or 2,

the magnetic field is either a horizontal magnetic field that forms a horizontal magnetic field distribution with respect to the silicon melt or a cusp magnetic field that forms a cusp-type magnetic field distribution with respect to the silicon melt.

4. The method of manufacturing a single crystal silicon ingot according to claim 3, wherein the silicon ingot is produced by a method comprising the steps of,

the magnetic field is a horizontal magnetic field having a horizontal magnetic field distribution with respect to the silicon melt, and the magnetic field strength is 1000G to 5000G.

5. The method of manufacturing a single crystal silicon ingot according to claim 3, wherein the silicon ingot is produced by a method comprising the steps of,

the magnetic field is a cusp magnetic field having a cusp-type magnetic field distribution with respect to the silicon melt, and the magnetic field strength is 300G or more and 1500G or less.

6. The method of manufacturing a single crystal silicon ingot according to any one of claims 1 to 5, wherein the silicon ingot is a silicon ingot,

the single crystal silicon ingot is sliced from the silicon melt, and then the rotation speed of the quartz crucible is set to 0.5rpm to 2.0 rpm.