JP7120187B2 - Method for growing silicon single crystal and apparatus for pulling silicon single crystal - Google Patents

Description

The present invention relates to a silicon single crystal growing method and a silicon single crystal pulling apparatus.

A method called the Czochralski method (hereinafter referred to as the CZ method) is used for the production of silicon single crystals (single crystal ingots). In general, in the production of silicon single crystals using the CZ method, silicon single crystals with low oxygen concentration are of high quality in order to suppress the occurrence of crystal defects and oxygen precipitates. It is said that

Patent Document 1 describes a pulling apparatus capable of reducing the oxygen concentration in a silicon single crystal by controlling the heat center height of a heater.

JP 2018-111611 A

Silicon single crystals are required to have a reduced oxygen concentration, but may also require a certain degree of oxygen concentration. For example, when wafer strength is required, various oxygen concentrations are required, such as high oxygen concentration silicon single crystals.
Oxygen in the silicon melt is taken into the silicon single crystal through the solid-liquid interface, which is the crystal growth interface. Therefore, it is necessary to adjust the oxygen concentration at the solid-liquid interface in order to adjust the oxygen concentration. However, the lifting device has a problem that there is a limit to the adjustment of the oxygen concentration.

SUMMARY OF THE INVENTION An object of the present invention is to provide a silicon single crystal growing method and a silicon single crystal pulling apparatus that enable control of the oxygen concentration according to the needs of the silicon single crystal.

A method for growing a silicon single crystal according to the present invention is a method for growing a silicon single crystal by the Czochralski method, comprising a heating step of heating a silicon raw material in a quartz crucible to form a silicon melt; a magnetic field applying step of applying a horizontal magnetic field to the quartz crucible; and a quartz crucible temperature gradient setting step of setting a temperature gradient in the quartz crucible. A temperature gradient is applied to the quartz crucible so that a temperature gradient is generated between one side of the crucible in the direction of the magnetic field and the other side of the crucible in the direction of the magnetic field.

The method for growing a silicon single crystal described above includes an oxygen transfer direction estimating step of estimating an oxygen transfer direction of the silicon melt in the magnetic field applying step, and in the temperature gradient setting step of the quartz crucible, the magnetic field direction of the quartz crucible and the other side of the magnetic field direction, the temperature gradient may be set so that the temperature on the oxygen transfer source side estimated in the oxygen transfer direction estimation step is lower or higher. good.

In the method for growing a silicon single crystal, the oxygen transfer direction estimation step may estimate the oxygen transfer direction based on the rotational direction of the quartz crucible and the rotational direction of convection of the silicon melt.

In the method for growing a silicon single crystal, in the magnetic field applying step, the rotation direction of the convection is estimated based on the surface temperature of the silicon melt, and the rotation direction of the convection is set to the desired rotation direction. A magnetic field may be applied when .

According to the second aspect of the present invention, the device for pulling a silicon single crystal includes a quartz crucible rotatable around its axis, a heating device for heating the silicon melt in the quartz crucible, and a heating device for heating the silicon melt. a magnetic field applying device that applies a horizontal magnetic field to the quartz crucible, wherein the heating device is formed so as to create a temperature gradient between one side of the quartz crucible in the direction of the magnetic field and the other side of the direction of the magnetic field. characterized by

In the apparatus for pulling a silicon single crystal, the heating device may be a carbon heater, the carbon heater may be divided in a circumferential direction as a plurality of heater pieces, and each heater piece may be temperature-controllable.

In the apparatus for pulling a silicon single crystal, the heating device may be a carbon heater, and the carbon heater may have a different thickness on one side in the direction of the magnetic field and on the other side in the direction of the magnetic field.

According to the present invention, even when the oxygen in the silicon melt is transferred in either direction of the magnetic field during the growth of the silicon single crystal, the distance between one side of the quartz crucible in the direction of the magnetic field and the other side of the direction of the magnetic field is reduced. The oxygen concentration can be controlled by maintaining the temperature of the quartz crucible so as to create a temperature gradient at , and varying the concentration of oxygen eluted from the quartz crucible.

1 is a schematic cross-sectional view of a lifting device according to an embodiment of the invention; FIG. FIG. 2 is a sectional view taken along the line II-II of FIG. 1; FIG. 4 is an explanatory view showing the rotation direction of silicon melt convection, the rotation direction of the crucible, and the oxygen transfer direction. FIG. 3 is an explanatory diagram showing a flow generated in a silicon melt; It is a graph which shows the temperature change of the measurement point in a magnetic field application timing determination process. FIG. 4 is a temperature distribution diagram estimating the temperature state on the surface of the silicon melt. FIG. 4 is an explanatory diagram showing the oxygen transfer mechanism based on the direction of rotation of convection and the direction of rotation of the crucible; FIG. 4 is an explanatory diagram showing a difference in oxygen elution amount due to a temperature gradient of a heater; FIG. 4 is a cross-sectional view of a lifting device according to another embodiment of the present invention;

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[Lifting device]
FIG. 1 is a schematic cross-sectional view of a lifting device 1 according to an embodiment of the invention. FIG. 2 is a sectional view taken along line II-II of FIG. In order to facilitate understanding of the structure, the drawing shows X, Y and Z axes that are orthogonal to each other (the same applies to other drawings). The X and Y directions correspond to the horizontal direction, and the Z direction corresponds to the vertical direction.
A pulling apparatus 1 is an apparatus for pulling and growing a silicon single crystal S by the Czochralski method. As shown in FIG. 1 , the pulling device 1 includes a chamber 2 forming an outer shell, a crucible 3 arranged in the center of the chamber 2 , a heater 4 and a magnetic field applying device 5 .

The crucible 3 is a container in which the silicon melt M is stored and has a circular shape when viewed from above in the vertical direction. The crucible 3 has a double structure composed of an inner quartz crucible 3A and an outer graphite crucible 3B. The crucible 3 is fixed to the upper end of a support shaft 6 that can rotate and move up and down and extends along the Z axis.

The heater 4 is a heating device that heats the silicon melt M in the crucible 3 . The heater 4 has a cylindrical shape and is arranged coaxially with the central axis A of the crucible 3 outside the crucible 3 . The heater 4 is a resistance heating type so-called carbon heater that heats with Joule heat when an electric current passes through the heater. A heat insulator 7 is provided outside the heater 4 along the inner surface of the chamber 2 . A detailed structure of the heater 4 will be described later.

The magnetic field application device 5 is a device that applies a horizontal magnetic field to the silicon melt M in the crucible 3 .
The magnetic field applying device 5 includes a first magnetic body 5A and a second magnetic body 5B, each of which is an electromagnetic coil. The first magnetic body 5A and the second magnetic body 5B are provided outside the chamber 2 so as to face each other with the crucible 3 interposed therebetween. The magnetic field applying device 5 applies a horizontal magnetic field such that the positive direction of the magnetic field direction MD is the +Y direction (the direction from the front side to the back side of the paper surface in FIG. 1). The magnetic field strength of the horizontal magnetic field is, for example, 0.18 Tesla to 0.40 Tesla.
The magnetic lines of force generated by the magnetic field applying device 5 have different directions depending on the location due to the mutual repulsive force. Here, the magnetic field direction MD means the direction of the neutral line of magnetic lines of force in which the mutual repulsive forces are balanced. Also, the same direction as the direction of the magnetic lines of force is described as "the positive direction of the magnetic field direction MD", and the direction opposite to the direction of the magnetic lines of force is described as the "negative direction of the magnetic field direction MD".

A pull-up shaft 8 is arranged above the crucible 3 . The pull-up shaft 8 is made of wire or the like. The pull-up shaft 8 rotates coaxially with the support shaft 6 in the opposite direction or the same direction at a predetermined speed. A seed crystal SC is attached to the lower end of the pulling shaft 8 .

A thermal shield 9 is arranged in the chamber 2 . The heat shield 9 has a cylindrical shape and surrounds the silicon single crystal S being grown above the silicon melt M in the crucible 3 .
The heat shield 9 blocks high-temperature radiant heat from the silicon melt M in the crucible 3 , the heater 4 , and the side wall of the crucible 3 to the silicon single crystal S being grown. In addition, the heat shield 9 suppresses the diffusion of heat to the outside in the vicinity of the solid-liquid interface SI, which is the crystal growth interface, and reduces the temperature gradient in the direction of the pulling axis between the central portion of the single crystal and the outer peripheral portion of the single crystal. play a role in controlling

A gas introduction port 10 is provided in the upper portion of the chamber 2 . A gas inlet 10 introduces an inert gas such as argon gas into the chamber 2 . An exhaust port 11 is provided at the bottom of the chamber 2 . The exhaust port 11 sucks and discharges the gas in the chamber 2 by driving a vacuum pump (not shown). The inert gas introduced into the chamber 2 from the gas inlet 10 descends between the silicon single crystal S being grown and the thermal shield 9 . Next, the inert gas passes through the gap between the lower end of the heat shield 9 and the surface of the silicon melt M, and then flows outside the heat shield 9 and further outside the crucible 3 . After that, the inert gas descends outside the crucible 3 and is discharged from the exhaust port 11 .

The pulling device 1 comprises a temperature measuring device 12 for measuring the temperature of the surface MA of the silicon melt M. As shown in FIG. As shown in FIGS. 1 and 2, the temperature measurement device 12 measures three measurement points P1, P2, and P3 (P) on the surface MA of the silicon melt M and around the solid-liquid interface SI. Therefore, it has three reflectors 13 and three radiation thermometers 14 (only two radiation thermometers 14 are shown in FIG. 1).

The reflector 13 is installed inside the chamber 2 . From the viewpoint of heat resistance, it is preferable to use a silicon mirror whose one surface is mirror-polished to form a reflecting surface as the reflecting portion 13 .
A radiation thermometer 14 is installed outside the chamber 2 . The radiation thermometer 14 receives radiation light L incident through a quartz window 2A provided in the chamber 2, and measures the temperature of the measurement point P without contact.

The first measurement point P1 and the third measurement point P3 are set on a virtual plane F1 that includes the central axis A and is orthogonal to the magnetic field direction MD. The first measurement point P1 and the third measurement point P3 are set at symmetrical positions with respect to the central axis A. As shown in FIG.
The second measurement point P2 is set on the first magnetic body 5A side on a virtual plane F2 that includes the central axis A and is parallel to the magnetic field direction MD.

Next, the detailed structure of the heater 4 will be described.
The heater 4 is configured such that the heating capacity is different between one side and the other side of the magnetic field direction MD of the horizontal magnetic field when viewed from above in the vertical direction. Specifically, the heater 4 is configured to have different heating capabilities on both sides of the imaginary plane F1. That is, the heater 4 is formed so that a temperature gradient is generated between one side of the quartz crucible 3A in the magnetic field direction MD and the other side of the magnetic field direction MD.
The heater 4 of the present embodiment includes a first heating unit 4A located on one side (first magnetic body 5A side) of the virtual plane F1, and a heating unit 4A located on the other side (second magnetic body 5B side) of the virtual plane F2. and a second heating unit 4B located.

The first heating portion 4A and the second heating portion 4B are formed in a semi-cylindrical shape with a central angle of 180° in plan view. The first heating portion 4A and the second heating portion 4B have different thicknesses, and the thickness of the second heating portion 4B is thinner than the thickness of the first heating portion 4A. That is, since the electrical resistance of the second heating section 4B is greater than the electrical resistance of the first heating section 4A, if the same voltage is applied to the first heating section 4A and the second heating section 4B, the The amount of heat generated by the second heating unit 4B is greater than that of the first heating unit 4A.

[Method for growing silicon single crystal]
Next, a method for growing a silicon single crystal using the silicon single crystal pulling apparatus 1 of this embodiment will be described. The method for growing a silicon single crystal according to the present embodiment is carried out in consideration of the oxygen concentration distribution of the silicon melt M. As shown in FIG. Specifically, in the silicon single crystal growth method of the present embodiment, the direction of oxygen transfer in the silicon melt M is controlled, and the silicon melt M is heated by the heater 4 having a temperature gradient in the magnetic field direction MD. By doing so, the oxygen concentration distribution of the silicon melt M is controlled.
A silicon single crystal growing method includes a heating step, a temperature measuring step, a magnetic field application timing determining step, a magnetic field applying step, and a quartz crucible temperature gradient setting step for setting a temperature gradient in the quartz crucible 3A in this order. have in In addition, you may change suitably about the order of a process.

In the heating step, the silicon raw material in the crucible 3 is heated using the heater 4 in a non-magnetic field state, that is, in a state in which the magnetic field applying device 5 is not operated, to form the silicon melt M, and the silicon melt M is heated. It is a process to do.

The temperature measurement step is a step of measuring the temperature of the surface MA of the silicon melt M with the temperature measurement device 12 .
The magnetic field application timing determination step is a step of determining the timing of applying the magnetic field based on the result of measuring the temperature of the surface MA of the silicon melt M, and controlling the rotation direction of the convection CF.
The magnetic field application step is a step of applying a horizontal magnetic field to the silicon melt M in the quartz crucible 3A rotating while maintaining the temperature of the silicon melt M. FIG.
The quartz crucible temperature gradient setting step is a step of applying a temperature gradient to the quartz crucible 3A using the heater 4 after the magnetic field application step. A temperature gradient is generated between one side in the magnetic field direction MD and the other side in the magnetic field direction MD in the quartz crucible 3A by the quartz crucible temperature gradient setting step.

[Oxygen Transfer Direction in Silicon Melt in Crucible]
Here, the mechanism of oxygen transfer in the silicon melt M in the crucible 3 will be described.
The present inventors found that in the process of growing the silicon single crystal S, when the crucible 3 is rotated around the central axis A and a magnetic field is applied to the silicon melt M by the magnetic field applying device 5, oxygen in the silicon melt M A concentration distribution was found to occur. Specifically, with respect to the magnetic field direction MD, the oxygen concentration in one direction increases and the oxygen concentration in the other direction decreases, so that oxygen is transported in one of the magnetic field directions MD (positive direction or negative direction). occurs.
Transport refers to the movement of oxygen within the silicon melt M by diffusion and convection. Also, when oxygen is transferred from A to B, A is the transfer source side and B is the transfer destination side.

The present inventors have found that the oxygen transfer direction DF as shown in FIG. We have found that the direction of rotation R can be controlled by two factors. Specifically, the combination of (1) the rotation direction (clockwise, counterclockwise) of the convection CF and (2) the rotation direction R (clockwise, counterclockwise) of the crucible 3 determines which direction of the magnetic field direction MD It was found that it is possible to estimate how much oxygen is transferred to
The rotation direction of the convection CF described below is the clockwise rotation direction (shown in FIG. 3) or the counterclockwise rotation direction when viewed in the positive direction of the magnetic field direction MD (viewed in the +Y direction). . The rotation direction R of the crucible 3 is a clockwise rotation direction (shown in FIG. 3) or a counterclockwise rotation direction when viewed from above in the vertical direction (in the −Z direction).

[(1) Rotational direction of convection and its control method]
The direction of rotation of the convection CF used in the magnetic field application timing determination step and the control method thereof will be described in detail below. By the method described below, it is possible to control whether the direction of rotation of the convection CF is clockwise or counterclockwise.
The inventors have found that a convection CF occurs in the silicon melt M to which a magnetic field is applied. As shown in FIG. 3, the convection CF is generated between the surface MA of the silicon melt M and the bottom surface of the crucible 3, and the silicon melt M flows around the virtual axis V extending in the direction of the magnetic field MD. It is a flowing roll-like flow. The silicon melt M is stabilized by this flow.
The rotation direction of the convection CF is clockwise or counterclockwise when viewed from the positive direction of the magnetic field direction MD. I found that it can be done. Specifically, the direction of rotation of the convection CF can be controlled based on the temperature of the surface MA of the silicon melt M at the time of applying the magnetic field.

In the heating step of the silicon single crystal growing method of the present embodiment, no horizontal magnetic field is applied to the silicon melt M, and the quartz crucible 3A is rotated at 0.1 rpm to 1 rpm. In this state, since the silicon melt M is heated in the vicinity of the outer periphery of the quartz crucible 3A, upward convection from the bottom of the silicon melt M toward the surface MA is generated as shown in FIG. The rising silicon melt M is cooled on the surface MA of the silicon melt M, returns to the bottom of the quartz crucible 3A at the center of the quartz crucible 3A, and a downward flow D is generated.

In a state where the air rises in the outer peripheral portion and the downward flow D is generated in the central portion, the position of the downward flow D moves chaotically and deviates from the center due to instability due to thermal convection. Such a downward flow D is generated by the temperature distribution on the surface MA of the silicon melt M. The temperature is lowest at the portion corresponding to the descending flow D, and the temperature gradually increases from the descending flow D toward the outside of the surface MA.

FIG. 5 is a graph showing temperature changes at measurement points P1, P2, and P3 after the heating process. The horizontal axis of FIG. 5 is time, and the vertical axis is temperature.
After the heating process, as shown in FIG. 5, the temperatures at the measurement points P1, P2, and P3 all oscillate periodically. The vibration period is, for example, 600 sec, which does not match the crucible rotation period of 300 sec. The vibration phases are shifted by 90 sec at each of the measurement points P1, P2, and P3.

FIG. 6 shows the estimated temperature state of each of the four cycles of temperature vibration. For example, in the state of FIG. 6(A), the temperature is the lowest in the first region A1 whose center is shifted from the rotation center of the quartz crucible 3A, and the second region A2, the third region A3, The temperature increases in the order of the fourth area A4 and the fifth area A5.
When a magnetic field is applied by the magnetic field applying device 5 in the state of FIG. 6(D), the magnetic field strength increases, while the temperature approaches the state of FIG. In that state the magnetic field becomes strong enough and the flow is fixed by the braking force. In the state of FIG. 6(A), the downward flow leans to the right in the figure, and considering the flow in the plane perpendicular to the magnetic field, it rises at the crucible wall at the left end in the figure and shifts to the right from the center. Descending vortices dominate at points. It is considered that the vortex remains as the main stream even after the magnetic field is applied, and the temperature at the measurement point P1 is high, that is, it is fixed in the clockwise mode. Therefore, in the magnetic field application timing determination step, when the rotation direction of the convection CF is set to the clockwise mode, the timing shown in FIG. 6(D) is used. The direction of rotation can be controlled by starting the application of the magnetic field.

[(2) Crucible Rotation Direction]
The rotation direction R of the crucible 3 can be controlled by a drive source that drives the support shaft 6 . That is, by controlling the support shaft 6, it is possible to control whether the rotation direction R of the crucible 3 is clockwise or counterclockwise.

[Oxygen transfer direction based on convection rotation direction and crucible rotation direction]
Next, the oxygen transfer mechanism based on the rotation direction of the convection CF and the rotation direction R of the crucible 3 will be described. The inventors considered that the transport direction DF of oxygen is determined by the following mechanism.
As shown in FIG. 7( a ), the generation of the convection CF generates a flow indicated by an arrow CF<b>1 in the vicinity of the bottom surface of the crucible 3 . That is, in the vicinity of the bottom surface of the crucible 3, oxygen rides a flow toward one side in the X direction. Of the flows constituting the convection CF, the oxygen-rich melt carried by the ascending flow evaporates from the surface MA without supplying oxygen to the silicon melt M. On the other hand, the flow near the bottom surface of the crucible 3 serves to supply oxygen into the silicon melt M without evaporating oxygen from the surface MA.
Further, as shown in FIG. 7(b), when the crucible 3 rotates, a shear stress between the silicon melt M and the inner surface of the crucible 3 acts on the silicon melt M as indicated by an arrow R1.

The silicon melt M with a high oxygen concentration gathers on one side in the X direction by the flow CF1 at the bottom surface of the crucible 3, and is transported in the positive direction of the magnetic field direction MD by riding the flow due to the shear stress with the inner surface of the crucible 3. .

The following table shows the relationship between the direction of rotation of the convection CF and the direction of rotation R of the crucible 3 estimated by the above mechanism and the direction of transfer of oxygen. Thus, the direction of oxygen transfer DF in the silicon melt M can be estimated from the direction of rotation of the convection CF and the direction of rotation R of the crucible 3 . In other words, by controlling the direction of rotation of the convection CF and the direction of rotation R of the crucible 3, the direction of oxygen transfer DF can be controlled.

The oxygen transfer direction DF can be estimated by the mechanism described above, but can also be estimated by computer simulation. When estimating by computer simulation, it is desirable to use a three-dimensional flow model to consider the influence of the horizontal magnetic field on the flow and temperature of the melt inside the crucible and the influence of the heat environment inside the furnace.

In the pulling apparatus 1 of the present embodiment, even when oxygen in the silicon melt M is transferred due to the rotation of the convection CF and the rotation of the crucible 3, the oxygen concentration is controlled such that the unevenness of the oxygen concentration is reduced. It can be performed.
_In the temperature gradient setting step of the quartz crucible, for example, as shown in _FIG . put out. The heater 4 of this embodiment is formed so that a temperature gradient is generated between one side of the quartz crucible 3A in the magnetic field direction MD and the other side of the magnetic field direction MD. Therefore, more oxygen O ₂ is dissolved from the side of the quartz crucible 3A having a higher temperature. In this embodiment, more oxygen O ₂ is dissolved from the side closer to the second heating section 4B where the electrical resistance is greater than that of the first heating section 4A.
That is, in the silicon single crystal pulling apparatus 1 of the present embodiment, the elution amount of oxygen O ₂ due to heating by the heater 4 differs between one side and the other side of the magnetic field direction MD.

According to the above-described embodiment, by varying the concentration of oxygen O ₂ eluted from the quartz crucible 3 between one side and the other side of the magnetic field direction MD, oxygen in the silicon melt M during the growth of the silicon single crystal S is reduced. Even when O ₂ is transported in the positive direction or the negative direction of the magnetic field direction MD, it is possible to control the oxygen concentration, such as reducing non-uniformity of the oxygen concentration.
Specifically, as shown in FIG. 8, by controlling the rotation direction of the convection CF and the rotation direction R of the crucible 3, the oxygen transfer direction DF is set in the positive direction of the magnetic field direction MD, and the temperature gradient of the heater 4 Oxygen O ₂ is positively supplied to locations where the oxygen concentration becomes low due to oxygen transfer. As a result, non-uniformity of the oxygen concentration is reduced, so that oxygen taken into the silicon single crystal S from the solid-liquid interface SI can be increased to increase the oxygen concentration.

In the above embodiment, the temperature gradient of the heater 4 is achieved by varying the thickness of the heater 4, but it is not limited to this. For example, as shown in the modified example of FIG. 9, the heater 4 may be divided into a plurality of heater pieces 4C to 4F in the circumferential direction, and control may be performed such that the applied voltage is different for each of the heater pieces 4C to 4F.
By changing the applied voltage for each heater piece, the position at which more oxygen O ₂ is dissolved in the quartz crucible 3A can be changed to a desired position. Thereby, the temperature gradient can be set so that the desired side of the quartz crucible 3A in the magnetic field direction MD and the other side in the magnetic field direction MD has a higher temperature. By setting the temperature gradient, it is possible to further control the oxygen concentration in the silicon melt M, and thus to control the amount of oxygen taken into the silicon single crystal S.

The silicon single crystal growing method using the silicon single crystal pulling apparatus 1 of this modified example has an oxygen transfer direction estimation step of estimating the oxygen transfer direction in the magnetic field application step. In the silicon single crystal growth method of this modification, in the oxygen transfer direction estimation step, the oxygen transfer direction is estimated from the rotation direction R of the quartz crucible 3A and the rotation direction of the convection CF of the silicon melt M, and the temperature gradient of the quartz crucible In the setting step, the temperature gradient can be set so that the temperature on the oxygen transfer source side, which is estimated in the oxygen transfer direction estimation step, between one side of the quartz crucible in the magnetic field direction and the other side in the magnetic field direction is higher. . That is, by setting so that more oxygen is dissolved on the oxygen transfer source side, a single crystal with a higher oxygen concentration can be obtained than when the quartz crucible is not provided with a temperature gradient.
Conversely, when a temperature gradient is provided in the quartz crucible so that the temperature of the quartz crucible on the oxygen transfer source side is low, a single crystal with a lower oxygen concentration can be obtained than when the quartz crucible is not provided with a temperature gradient. .

Without being limited to this example, various oxygen concentrations can be controlled by maintaining the temperature of the quartz crucible 3A so as to create a desired temperature gradient between one side of the magnetic field direction MD and the other side of the magnetic field direction MD. It can be performed.

For example, in order to improve the strength of the wafer, it is preferable to grow a silicon single crystal S with a high oxygen concentration. This is because the presence of oxygen atoms between Si lattices improves the mechanical strength of the wafer.
Also, when used as a gettering site, a silicon single crystal S with a high oxygen concentration is preferable. This is because oxygen precipitates can be used as gettering sites for gettering impurity metals that diffuse during device fabrication.

On the other hand, silicon single crystal S for power devices preferably has a low oxygen concentration.
This is because the presence of oxygen precipitates in the channel portion of the device deteriorates the device characteristics. Power devices designed to allow current to flow in the direction of the height of the wafer (such as leakage current and deterioration of withstand voltage) require the crystal to be low-oxygen because the entire wafer becomes the channel.

Note that the number of divisions of the heater 4 is not limited to six divisions as shown in FIG. 9, but may be an arbitrary division number such as two divisions or four divisions. That is, various methods can be adopted as long as the temperature gradient of the heater 4 can be provided.

DESCRIPTION OF SYMBOLS 1... Pulling device, 2... Chamber, 3... Crucible, 3A... Quartz crucible, 4... Heater, 4C to 4F... Heater piece, 5... Magnetic field applying device, 12... Temperature measuring device, CF... Convection, M... Silicon melt , MD... magnetic field direction, S... silicon single crystal.

Claims (7)

A method for growing a silicon single crystal by the Czochralski method,
a heating step of heating the silicon raw material in the quartz crucible to form a silicon melt;
a magnetic field applying step of applying a horizontal magnetic field to the silicon melt;
a quartz crucible temperature gradient setting step of setting a temperature gradient in the quartz crucible;
In the quartz crucible temperature gradient setting step, a temperature gradient is applied to the quartz crucible so as to create a temperature gradient between one side of the quartz crucible in the direction of the magnetic field and the other side of the direction of the magnetic field after the step of applying the magnetic field. A method for growing a silicon single crystal, characterized by: In the method for growing a silicon single crystal according to claim 1,
an oxygen transfer direction estimation step of estimating the oxygen transfer direction of the silicon melt in the magnetic field application step;
In the temperature gradient setting step of the quartz crucible, the temperature of the oxygen transfer source side estimated in the oxygen transfer direction estimation step is lower than the one side of the quartz crucible in the magnetic field direction and the other side of the magnetic field direction. A method for growing a silicon single crystal, characterized in that the temperature gradient is set so as to increase or decrease. In the method for growing a silicon single crystal according to claim 2,
The method for growing a silicon single crystal, wherein the oxygen transfer direction estimation step estimates the oxygen transfer direction from the rotation direction of the quartz crucible and the rotation direction of convection of the silicon melt. In the method for growing a silicon single crystal according to claim 3,
In the magnetic field applying step, the direction of rotation of the convection is estimated based on the surface temperature of the silicon melt, and the magnetic field is applied when the direction of rotation of the convection is a desired direction. Crystal growth method. a quartz crucible rotatable about its axis;
a heating device for heating the silicon melt in the quartz crucible;
a magnetic field applying device that applies a horizontal magnetic field to the silicon melt,
An apparatus for pulling a silicon single crystal, wherein the heating device is formed so as to create a temperature gradient between one side of the quartz crucible in the direction of the magnetic field and the other side of the direction of the magnetic field. In the silicon single crystal pulling apparatus according to claim 5,
An apparatus for pulling a silicon single crystal, wherein the heating device is a carbon heater, the carbon heater is divided in a circumferential direction into a plurality of heater pieces, and the temperature of each of the heater pieces is controllable. In the silicon single crystal pulling apparatus according to claim 5,
The apparatus for pulling a silicon single crystal, wherein the heating device is a carbon heater, and the carbon heater has a different thickness on one side in the direction of the magnetic field and on the other side in the direction of the magnetic field.

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