JP2008019129A - Apparatus for producing single crystal, method for producing single crystal, and single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for producing a single crystal by which the convection of a silicon melt can be controlled during pulling and the quality difference of the single crystal depending on the residual amount of the silicon melt can be reduced. <P>SOLUTION: The apparatus for producing the single crystal comprises a convection control member 35 which can be arranged in a silicon melt 4 and a supporting means for supporting the convection control member 35 from an upper part of a crucible. The convection control member 35 is formed to have a nearly circular disk shape capable of being positioned in a state nearly parallel to the bottom surface of the crucible and is composed of a plurality of plate-like pieces 36 divided by a plurality of line segments extended to outer edge parts from the central axis 15 position of the silicon single crystal 3 being pulled as the center in a plane view. The angle α formed by the tangential plane of the upper surface 36a of each plate-like piece 36 at the center and the central axis 15 direction in the downward direction is set in the cross section along the central axis, and the supporting means supports each plate-like piece 36 of the convection control member 35 so that the angle can be adjusted so as to control the convection of the silicon melt 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is capable of controlling the convection of the silicon melt at the time of pulling, and can reduce the quality difference of the single crystal depending on the amount of the remaining silicon melt, and the single crystal production thereof The present invention relates to a method for producing a single crystal using an apparatus and a single crystal.

  A silicon single crystal is grown by heating a polycrystalline silicon raw material contained in a crucible with a heater to form a silicon melt, and pulling it up from the silicon melt by the Czochralski method (hereinafter abbreviated as “CZ method”). It is manufactured by. In a silicon single crystal grown by the CZ method, a defect called a Grown-in defect is formed during crystal growth, and is detected when a silicon single crystal obtained after crystal growth is evaluated.

It is known that R-OSF (Ring-Oxidation induced Stacking Fault) may appear in the longitudinal section of a silicon single crystal grown while gradually reducing the pulling rate. The region where R-OSF appears shrinks from the outer peripheral side of the crystal to the inside as the pulling rate is reduced. The grown-in defects observed after crystal growth are different between the inside (crystal region pulled at a high speed) and the outside (crystal region pulled at a low speed) from the R-OSF. In the crystal region pulled at a high speed, a void defect (a void type defect) called COP (crystal originated particle) or FPD (flow pattern defect) is detected. In addition, in the crystal region pulled at a low speed, interstitial Si aggregates accompanied by dislocations are generated, and interstitial Si defects (dislocation cluster defects) are detected.
In addition, there is a defect-free region in which no Grown-in defect is detected between the R-OSF and the interstitial Si defect region. The void defect in the silicon single crystal is a deterioration factor of the initial oxide film breakdown voltage characteristic of the wafer. In addition, interstitial Si defects in the silicon single crystal also degrade device characteristics. Therefore, crystal growth in a defect-free region is desired because of the quality characteristics of the silicon single crystal.

Conventionally, a method of pulling up in a magnetic field (MCZ method) is known as a method for obtaining a uniform silicon single crystal that can suppress convection of a silicon melt (see, for example, Patent Document 1).
JP-A 64-24090

  However, the conventional technology cannot sufficiently suppress the convection of the silicon melt. In particular, when producing a silicon single crystal using the pulling method in a magnetic field, the amount of silicon melt in the crucible gradually changes (decreases), so the difference in strength of the magnetic field depending on the position in the silicon melt (solid-liquid interface) The difference in magnetic field strength between the position and the bottom of the crucible is large when the amount of residual silicon melt is large, and is small when the amount of residual liquid is small, and the amount of change in convection of the silicon melt due to the amount of residual silicon melt. The convection of the silicon melt could not be sufficiently suppressed. This convection in the silicon melt affects the temperature distribution near the solid-liquid interface, the shape of the solid-liquid interface (convex upward, etc.) due to this temperature distribution, or the surface of the crucible wall. It has been found that the oxygen concentration in the silicon melt, dopants, how impurities such as bubbles are incorporated into the single crystal, and as a result, the crystal quality in the single crystal are affected. For this reason, in the conventional technique, even if the pulling is performed under the same pulling conditions from the start to the end of pulling, the single crystal grown in the first half of the pulling and the single crystal grown in the second half of the pulling have a single crystal defect state, The quality of single crystals such as the oxygen concentration and dopant concentration of these materials greatly differed, and a single crystal having a desired quality could not be obtained, resulting in a significant decrease in yield.

  Specifically, for example, when a crystal of a defect-free region is manufactured while applying a cusp magnetic field, if the amount of silicon melt accommodated in the crucible is increased, the defect-free region is not formed immediately after the start of pulling. . When a crystal having a predetermined oxygen concentration or dopant concentration is produced while applying a cusp magnetic field, the in-plane distribution (Radial gradient of oxygen, ORG; Radial gradient of resistance; RRG) and the like change.

  The present invention has been made in view of the above circumstances, can control the convection of the silicon melt at the time of pulling, and reduce the quality difference of the single crystal depending on the residual amount of the silicon melt. It is an object of the present invention to realize a single crystal manufacturing apparatus, a single crystal manufacturing method using the single crystal manufacturing apparatus, and a single crystal.

The single crystal manufacturing apparatus of the present invention is a single crystal manufacturing apparatus for growing while pulling up a silicon single crystal from a silicon melt contained in a crucible.
A convection control member that is a plate-like body that can be arranged in the silicon melt, and a support means for supporting the convection control member from above the crucible,
The convection control member has a substantially disk shape that can be positioned substantially in parallel with the bottom surface of the crucible, and extends to an outer edge centering on a central axis position of the silicon single crystal that is pulled up in plan view. It consists of multiple plate-like pieces divided by line segments,
The supporting means can control the convection of the silicon melt by setting an angle α between a tangent plane of the upper surface of the plate-like piece at the center and a downward direction in the central axis in a cross section along the central axis. Thus, the above problem was solved by supporting the plate-like piece of the convection control member so that the angle can be adjusted.
In the present invention, the support means is capable of moving the tip of the plate-shaped piece on the central axis side up and down at a position on the outer surface of the silicon single crystal and on the inner wall of the crucible in plan view of the upper surface of the plate-shaped piece. A support rod suspended so as to rotatably support the plate-like piece,
One end can be brought into contact with the upper surface of the plate-like piece on the outer edge side in a plan view of the support rod, and the rod has a rod-shaped angle adjusting means that can expand and contract in parallel with the support rod.
By extending and contracting the angle adjusting means, the angle α of the plate-like piece can be set in a range of 0 to 180 °.
Also, in the present invention, when the angle α is set so that the convection control member is substantially parallel to the bottom surface of the crucible, the silicon melt has a direct influence on the quality of the single crystal grown. When the depth La, which is the distance between the silicon melt surface and the bottom surface of the crucible, exceeds the distance Lb so that the convection range is within the vertical distance Lb, the convection control member is It is preferable to be provided at a depth of the distance Lb from the liquid interface.
Further, the present invention comprises a magnetic field applying means for controlling the convection of the silicon melt,
The distance Lb may be set as a range in which the rate of change during pulling up of the magnetic field distribution applied by the magnetic field applying unit is 40% or less.
In addition, the present invention includes a heat shield member disposed on the upper side of the silicon melt, and when the convection control member moves in the vertical direction, the heat shield member is movable in the vertical direction. it can.
Further, the convection control member of the present invention can be at a position including at least a certain range of the silicon single crystal in a plan view.

The method for producing a single crystal of the present invention is a method for producing a silicon single crystal using the above-described single crystal production apparatus,
In the silicon melt, the above problem was solved by pulling up the silicon single crystal by controlling the angle α formed by the convection control member as a predetermined angle within a range of 0 to 180 °.
Further, in the present invention, the angle α is set by the support means so that the convection control member is positioned within the vertical distance Lb from the solid-liquid interface in a state substantially parallel to the bottom surface of the crucible, When the depth La, which is the distance between the silicon melt surface and the bottom surface of the crucible, exceeds the distance Lb, the convection range directly below the solid-liquid interface affects the quality of the single crystal grown in the silicon melt. Can be controlled to be within the distance Lb.
The method for producing a single crystal includes a step of melting a silicon raw material in the crucible to produce a silicon melt, a step of arranging the convection control member at a predetermined position in the silicon melt, A method of starting the single crystal pulling step after sequentially performing the step of adjusting the temperature of the silicon melt so as to become the pulling start temperature can be employed.
In the single crystal pulling step, the present invention applies a magnetic field to the silicon melt by the magnetic field applying unit, and the rate of change during pulling of the magnetic field distribution applied by the magnetic field applying unit is the distance Lb. Can be set as a range of 40% or less.
Moreover, the manufacturing method of said single crystal can be made into the method of pulling up the single crystal which has a defect-free area | region.

  In order to solve the above problems, the single crystal of the present invention is manufactured by any one of the above-described single crystal manufacturing apparatuses or any of the above-described single crystal manufacturing methods. .

  The single crystal manufacturing apparatus of the present invention is a single crystal manufacturing apparatus for growing while pulling up a silicon single crystal from a silicon melt accommodated in a crucible. Convection control is a plate-like body that can be placed in the silicon melt. And a support means for supporting the convection control member from above the crucible. The convection control member has a substantially disk shape that can be positioned substantially parallel to the bottom surface of the crucible and is pulled up in plan view. It consists of a plurality of plate-like pieces divided by a plurality of line segments extending to the outer edge centering on the center axis position of the silicon single crystal, and the support means is a cross section along the center axis in the center. The angle of the plate-like piece of the convection control member can be adjusted so that the convection of the silicon melt can be controlled by setting an angle α between the tangential plane of the upper surface of the plate-like piece and the downward direction in the central axis direction. By lifting, it is possible to reduce adverse effects on the single crystal pulling due to the silicon melt depth changes. In addition, since the convection control member is divided and the angle of the divided piece can be adjusted, the convection control member can be connected to the silicon melt without contacting the silicon single crystal being pulled up when the silicon melt is reduced. It is possible to reduce the silicon melt remaining in the crucible by pulling upward from the inside.

In the silicon melt, a main convection that rises along the quartz crucible body and falls near the center of the quartz crucible due to a temperature difference in the melt. In a conventional quartz crucible without a convection control device, the main convection is the only major convection generated in the silicon melt. On the other hand, in the silicon single crystal pulling apparatus of the present invention, by providing a convection control member, for example, as shown in FIG. 1 and FIG. 5 to FIG. Can produce secondary convection flowing in the opposite direction.

By this secondary convection, the atoms in the melt are well convectively mixed and diffused, and the effective diffusion coefficient D is greatly increased. Moreover, the temperature gradient Gm of the melt also increases. Therefore, systematic supercooling can be easily suppressed.
The secondary convection is an upward flow, transports the high-temperature melt to the solid-liquid interface shape center, the solid-liquid interface shape moves in the crystal direction, the temperature gradient of the crystal center near the solid-liquid interface increases, The temperature gradient difference is reduced. This increases the defect-free speed margin and increases the pass rate of defect-free crystals.

    In the present invention, the support means is capable of moving the tip of the plate-shaped piece on the central axis side up and down at a position on the outer surface of the silicon single crystal and on the inner wall of the crucible in plan view of the upper surface of the plate-shaped piece. A support bar that is suspended so as to rotatably support the plate-like piece, and one end can be brought into contact with the upper surface of the plate-like piece on the outer edge side in plan view of the support bar, and the support It has a rod-shaped angle adjusting means that can be expanded and contracted in parallel with the rod, and the angle α of the plate-shaped piece can be set in a range of 0 to 180 ° by expanding and contracting the angle adjusting means. Thus, by setting the angle of the plate-shaped piece to be supported, it is possible to produce an effect as if an uneven shape was formed on the surface of the convection control member. Set the uneven state of the control member And it makes it possible to give reliable results in secondary convection in the vicinity of the solid-liquid interface in the silicon melt.

  Further, at least the impurity concentration (dopant) concentration of the silicon melt near the solid-liquid interface is prevented from becoming higher than that of other portions of the silicon melt, and the silicon single crystal ingot is dislocated. Even if it is not, the uniformity of impurities (dopant) in the silicon single crystal ingot is desired, and the wafer surface resistivity distribution (RRG) and wafer surface oxygen distribution (ORG) when processing into a silicon wafer are desired. The shape is set to fall within the range.

RRG is defined as follows.
RRG = (wafer center resistivity ρ0−wafer side resistivity ρS) / wafer center resistivity ρ0
In general,
RRG (IN10) = (wafer center resistivity ρ0−wafer inside 10 mm resistivity ρS) / wafer center resistivity ρ0
RRG (IN5) = (wafer center resistivity ρ0−wafer inside 5 mm resistivity ρS) / wafer center resistivity ρ0
Etc. are used.
In the present invention, RRG (IN5) is used as RRG.

  The present inventor has conducted extensive research and found that the convection of the silicon melt during pulling changes depending on the shape of the bottom surface of the crucible. However, it is not practical to manufacture a crucible having an appropriate bottom shape according to the target quality of each single crystal to be manufactured, and it is not possible to replace the crucible while pulling up. However, the bottom shape of the crucible cannot be changed. Therefore, the present inventors have a deformable convection control member disposed in the silicon melt, and change the shape of the convection control member to an appropriate shape according to the target quality of each single crystal to be manufactured. It was found that the quality difference of the single crystal depending on the residual amount of the silicon melt can be reduced by making the convection of the silicon melt appropriately controllable.

  In the single crystal manufacturing apparatus of the present invention, the convection control member arranged in the silicon melt has a plurality of plate shapes divided on a line starting from the central axis of the silicon single crystal pulled up when viewed in plan. An angle α formed by the upper surface of the plate-shaped piece located near the central axis and the central axis in a cross section along the central axis is made variable. Therefore, the convection of the silicon melt at the time of pulling up is controlled by appropriately controlling the angle α in accordance with the target quality of each single crystal to be manufactured. As a result, it becomes possible to reduce the quality difference of the single crystals depending on the remaining amount of the silicon melt, and it is possible to manufacture single crystals having a desired quality with a high yield.

  Also, in the present invention, when the angle α is set so that the convection control member is substantially parallel to the bottom surface of the crucible, the silicon melt has a direct influence on the quality of the single crystal grown. When the depth La, which is the distance between the silicon melt surface and the crucible bottom surface, is equal to or greater than the distance Lb, the convection control member is a solid-liquid interface. To be located at a depth from Lb to Lb, the convection in the convection region in the vicinity of the solid-liquid interface that directly affects crystal growth is restricted to a range within the depth direction distance Lb, and directly affects the solid-liquid interface. It is possible to control the oxygen concentration, dopant concentration, temperature state, etc. within a predetermined range, and as a result, adverse effects on the single crystal to be pulled up due to the silicon melt depth change. It is possible to decrease.

  In the single crystal manufacturing apparatus of the present invention, the depth La of the silicon melt is such that the vertical distance between the lowest part of the convection control member and the melt surface from the start of the pulling to the start of the pulling. By controlling so that the position of the convection control member with respect to the melt surface does not change when it is at least within a predetermined range up to less than Lb, the depth La of the silicon melt is the distance Lb. When the convection of the silicon melt is controlled so as to be in a certain state, the convection of the silicon melt at the time of pulling can be further controlled as shown below.

That is, when a single crystal is manufactured using such a single crystal manufacturing apparatus, the amount of silicon melt remaining is large, and the depth of the silicon melt, which is the distance between the bottom of the crucible and the surface of the melt. The position of the convection control member relative to the melt surface when the thickness La is deeper than the vertical distance Lb between the lowermost portion of the convection control member and the melt surface at the start of pulling By controlling so as not to change, it is possible to control so that the silicon melt depth La is the distance Lb.
Therefore, when a single crystal is manufactured using the single crystal manufacturing apparatus of the present invention, fluctuations in the convection of the silicon melt from the start of the pulling up to the point where the distance is less than the distance Lb due to the decrease in the silicon melt accompanying the pulling. Very little.
Moreover, in the single crystal manufacturing apparatus of the present invention, the predetermined range is the entire range in which the depth La of the silicon melt is less than the distance Lb from the start of the pulling, so that the silicon melt In all ranges when the depth La of the silicon melt is deeper than the distance Lb, the convection of the silicon melt can be controlled to be in the state when the depth La of the silicon melt is the distance Lb. In this case, most of the single crystal pulled up becomes very small because the quality difference of the single crystal depending on the remaining amount of the silicon melt is small.

In addition, the present inventor has conducted intensive research and arranged a convection control member in the silicon melt, and while pulling up, the shape of the convection control member can be changed to appropriately control the convection of the silicon melt. By doing so, it was found that the quality difference of the single crystal depending on the remaining amount of the silicon melt can be reduced.
That is, in the above-described single crystal manufacturing apparatus, on the upper surface of the plate-like piece, at a position outside the outer diameter of the silicon single crystal and inside the inner wall of the crucible when viewed in plan, A support rod that supports the plate-like piece so as to be movable in the direction of the central axis is attached so that the angle α can be changed, and when viewed in plan, the plate-like piece is on a line passing from the central axis to the starting point. In the position overlapping with the plate-like piece, a rod-shaped angle adjusting means that can be expanded and contracted in the direction of the central axis in a state where one end is in contact with the plate-shaped piece, interlocked with the expansion and contraction of the angle adjusting means, When the angle α is changed, for example, the angle α is changed as shown below.

  When the angle adjusting means with one end abutting on the plate-shaped piece is expanded and contracted, the portion where the angle adjusting means abuts is used as a fulcrum, and the portion provided with the support bar is used as a power point to expand and contract the angle adjusting means. The plate-like piece is moved by the action of trying to balance the force applied to the piece, and the angle α is changed. Therefore, the shape of the convection control member can be changed without taking the convection control member out of the silicon melt, and the convection of the silicon melt can be appropriately controlled while being pulled up. The quality difference of the dependent single crystal can be reduced.

Further, the convection control member of the present invention has a shape including at least a certain range of the silicon single crystal (a range of a solid-liquid interface) in a plan view, and more specifically, the convection control member is substantially circular in a plan view. When the diameter of the silicon single crystal is Dd, the minimum diameter of the convection control member is at least included in the range of Dd to 1.8 Dd. Further, the maximum diameter of the convection control member can be a dimension that is substantially the same as the inner diameter of the crucible, that is, a shape that is located almost entirely inside the crucible in plan view so as not to contact the crucible wall. As a result, at least the convection in the convection region in the vicinity of the solid-liquid interface that directly affects crystal growth can be regulated to be within the depth direction distance Lb, thereby reducing the adverse effect on the single crystal to be pulled up. It becomes.
Furthermore, the convection control member has a shape that is located almost entirely inside the crucible, thereby maximizing the free surface of the melt when the convection control member comes into contact with the quartz crucible (the melt surface between the outside of the crystal and the inside of the quartz crucible). , Rapid increase in oxygen concentration is prevented. Usually, oxygen dissolved from quartz is evaporated from the melt free surface by 90% or more. Therefore, if the melt free surface decreases rapidly, the oxygen concentration in the melt rapidly increases and the oxygen concentration in the crystal to be pulled up also increases rapidly. It is expected to be.

The present invention further includes a magnetic field applying means for controlling the convection of the silicon melt, and the distance Lb is a range in which the rate of change during pulling up of the magnetic field distribution applied by the magnetic field applying means is 40% or less. Can be set. According to such a single crystal manufacturing apparatus, the convection in the portion directly affecting the quality of the single crystal immediately below the solid-liquid interface can be controlled by applying a magnetic field, and further, due to the difference in depth from the silicon melt surface. Since the difference in magnetic field strength can be reduced, it is possible to prevent variations in single crystal quality due to the pulling length.
The rate of change during the pulling of the magnetic field distribution is preferably set to 40% or less, more preferably 30% or less, or 20% or less.

The single crystal manufacturing apparatus includes a heat shield member disposed on the upper side of the silicon melt, and the heat shield member is movable in the vertical direction when the convection control member moves in the vertical direction. That is, that is, by providing a heat shield member arranged to face the silicon melt, convection of the silicon melt can be effectively suppressed.
However, in the above-described single crystal manufacturing apparatus provided with the support rod and the angle adjusting means, for example, when the convection control member is pulled up from the silicon melt in the middle of the pulling, the plate-shaped piece comes into contact with the heat shield member. There is a risk that it will end up. In particular, when the convection control member is pulled up, the plate-like piece located in the vicinity of the central axis hits the bottom surface of the crucible, so that the plate-like piece is not suspended from the support rod near the melt surface. The shape piece may be inclined downward toward the central axis. The plate-shaped piece inclined downward toward the central axis has a high risk of coming into contact with the heat shield member.
On the other hand, in the single crystal manufacturing apparatus provided with the support rod and the angle adjusting means, the heat shield member is movable in the central axis direction. When pulling up the convection control member, move the heat shield member to a height where there is a low risk of contact between the plate-shaped piece and the heat shield member, and then lift the convection control member. Contact between the strip and the heat shield member can be prevented.

Here, in this invention, when the said convection control member does not rotate synchronizing with a crucible, it is preferable that the crucible rotation at the time of raising made into object is set to about 0.1-10 rpm.
Moreover, in the single crystal pulling apparatus of the present invention, a convection control member rotating means that enables the convection control member to rotate in synchronization with the crucible can be provided. As described above, when the convection control member rotates in synchronization with the crucible, an arbitrary crucible rotation speed can be selected.

  The method for producing a single crystal of the present invention is a method for producing a silicon single crystal using the above-described single crystal production apparatus, wherein the angle α formed by the convection control member is 0 to 0 in the silicon melt. By pulling up the silicon single crystal by controlling it as a predetermined angle within the range of 180 °, it is possible to reduce the adverse effect on the single crystal to be pulled due to the change in the depth of the silicon melt caused by pulling up the single crystal. It becomes.

  Further, in the present invention, the angle α is set by the support means so that the convection control member is positioned within the vertical distance Lb from the solid-liquid interface in a state substantially parallel to the bottom surface of the crucible, When the depth La, which is the distance between the silicon melt surface and the bottom surface of the crucible, exceeds the distance Lb, the convection range directly below the solid-liquid interface affects the quality of the single crystal grown in the silicon melt. Is controlled to be within the vertical distance Lb, the convection in the convection region in the vicinity of the solid-liquid interface that directly affects the crystal growth is restricted to the range within the depth distance Lb, and directly on the solid-liquid interface. It is possible to control each parameter by preventing the influence of oxygen concentration, dopant concentration, temperature state, etc. from changing from a predetermined range. With and pulled due to the silicon melt depth changes occurring becomes possible to reduce the adverse effect on the single crystal.

  In the method for producing a single crystal of the present invention, a convection control member for controlling the convection of the silicon melt is disposed in the silicon melt after controlling the angle α to a predetermined angle. Since the crystal is pulled up, the convection of the silicon melt during pulling is controlled by the convection control member. Therefore, it becomes possible to reduce the quality difference of the single crystals depending on the residual amount of the silicon melt, and single crystals having a desired quality can be manufactured with a high yield.

  Further, in the above method for producing a single crystal, by pulling up the silicon single crystal while controlling the angle α, convection of the silicon melt at the time of pulling can be more effectively suppressed, and the remaining amount of silicon melt It becomes possible to further reduce the quality difference of the single crystal depending on.

  Further, in the method for producing a single crystal of the present invention, the position of the convection control member with respect to the melt surface changes when the depth La of the silicon melt is within at least a predetermined range up to the distance Lb. Since the silicon single crystal is pulled up while being controlled so as to prevent the single crystal from being produced, a single crystal having a small quality difference depending on the remaining amount of the silicon melt can be produced.

In the method for producing a single crystal, a step of melting a silicon raw material in a crucible to produce a silicon melt, a step of disposing a convection control member at a predetermined position in the silicon melt, a silicon melt And the step of adjusting the temperature so as to become the pulling start temperature, and then starting the single crystal pulling step, so that the convection control member can melt the silicon raw material or the silicon melt as shown below. It is possible to prevent the temperature adjustment of the pulling start temperature from being hindered, and it is possible to efficiently produce a single crystal.
Furthermore, a convection control member pulling step can be performed during the single crystal pulling step.

For example, it is not preferable to melt the silicon raw material after disposing the convection control member in the crucible because the convection control member may be softened because the melting temperature is higher than the pulling temperature. In fact, the quartz crucible may be softened when the silicon raw material is melted, which is not preferable when the convection control member is made of quartz. Therefore, at least after the melting of the silicon raw material, the convection control member should be immersed in the silicon melt. In addition, when the convection control member is disposed in the silicon melt after the step of adjusting the temperature by lowering the temperature from the melting temperature so that the temperature of the silicon melt becomes the pulling start temperature, the temperature is increased by disposing the convection control member. The starting temperature may fluctuate. Therefore, it is preferable to set the temperature at which the convection control member is pulled up after being immersed in the silicon melt.
On the other hand, after the silicon raw material is melted in the crucible, the convection control member is disposed at a predetermined position in the silicon melt, and then the temperature of the silicon melt is adjusted so as to be the starting temperature. The temperature of the silicon raw material (melt), which is high immediately after melting, and then drops to the starting temperature of pulling up, is naturally lowered by placing a convection control member in the silicon melt, and when the silicon raw material is melted Since it will approach the pulling start temperature lower than the temperature, compared to the case where no convection control member is arranged in the silicon melt, the pulling start temperature can be reached in a short time, and the total work for single crystal pulling Time can be shortened and a single crystal can be produced efficiently.
Note that the convection control member can be disposed at a position in the crucible before the melting step, for example, by lowering the silicon raw material melting temperature.

  Since the height of the convection control member and its angle α can be finely controlled by the support means, the formation state of the secondary convection is set more precisely and is influenced by the vortex flow in the melt. The dopant concentration / distribution and temperature gradient / state can be controlled more precisely. As a result, the crystal state of the single crystal to be pulled can be controlled more precisely.

In the present invention, the distance Lb can be set as a range in which the rate of change during pulling up of the magnetic field distribution applied by the magnetic field applying means is 40% or less. It is possible to control the convection of the portion that directly affects the crystal quality by applying a magnetic field, and to reduce the difference in magnetic field strength due to the difference in depth from the silicon melt surface.
For this reason, the convection in the convection region in the vicinity of the solid-liquid interface that directly affects the crystal growth is almost uniformly controlled in the magnetic field within the range in the depth direction distance Lb, and the oxygen concentration, dopant concentration, and The affected solid-liquid interface shape and the oxygen concentration, dopant concentration, defect distribution, temperature state, etc. in the nearby silicon melt change the silicon melt depth (solid-liquid interface) depending on the pulling length. It is possible to prevent the loss of the range and control each parameter. As a result, it is possible to reduce the adverse effect on the single crystal to be pulled due to the change in the depth of the silicon melt caused by the single crystal pulling.
The rate of change during the pulling of the magnetic field distribution is preferably set to 40% or less, more preferably 30% or less, or 20% or less.

In the present invention, it is also possible to set the above parameters in the single crystal to be pulled so as to change depending on the pulling length. In this case, the distance Lb from the solid-liquid interface to the convection control member is pulled up. By changing the length Lb and controlling the setting of the distance Lb over time, the shape of the solid-liquid interface can be set, the gradient of oxygen concentration, COP concentration, resistivity, etc. in the axial direction or non-uniform distribution It is also possible to pull up a single crystal having
At this time, for example, when applying a cusp magnetic field, if Lb is reduced,
Solid-liquid interface (lower convex → upper convex)
Oxygen concentration (decrease)
COP concentration (decrease)
Dopant concentration (increase)
Resistivity (decrease)
For example, when a cusp magnetic field is applied, when Lb is increased,
Solid-liquid interface (upward → downward)
Oxygen concentration (increase)
COP concentration (increase)
Dopant concentration (decrease)
Resistivity (increase)
There is a tendency to change. Therefore, in consideration of these, the value of Lb can be set sequentially as the pulling length increases. Of course, the control of these parameters includes the temperature conditions, the structure of the insulation material in the furnace, the rotation of the crucible and the single crystal, the pulling speed, the furnace pressure, the gas flow rate in the furnace, the gas composition, the magnetic field type and the application conditions, etc. It is preferable to carry out in conjunction with other parameters.

  In addition, when pulling up a single crystal having a defect-free region using the above-described method for producing a single crystal, a single crystal having a small quality difference depending on the amount of silicon melt remaining can be obtained. Even a single crystal having a defect-free region in which it was difficult to obtain can be manufactured with high yield. Alternatively, it is possible to obtain a single crystal as described above by controlling Lb and angle α.

  According to the single crystal manufacturing apparatus and the single crystal manufacturing method of the present invention, the convection of the silicon melt at the time of pulling can be controlled, and the generation of the quality difference of the single crystal depending on the residual amount of the silicon melt can be prevented. A single crystal having a desired quality characteristic can be produced in a short working time and with a high yield.

Hereinafter, the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a schematic cross-sectional view of a single crystal manufacturing apparatus according to a first embodiment of the present invention. In FIG. 1, the code | symbol 30 has shown the single crystal manufacturing apparatus. In the main chamber 1 of the single crystal manufacturing apparatus 30, a quartz crucible 5 for storing the silicon melt 4 and a graphite crucible 6 for protecting the quartz crucible 5 are supported by a holding shaft 13 by a crucible drive mechanism 21 so as to be rotatable and movable up and down. Has been. The heater 7 and the heat insulating material 8 are arranged so as to surround the quartz crucible 5 and the graphite crucible 6. A pulling chamber 2 for accommodating and taking out the grown silicon single crystal 3 is connected to the upper portion of the main chamber 1, and the silicon single crystal 3 is rotated by a wire 14 at the upper portion of the pulling chamber 2. A pulling mechanism (not shown) for pulling up is provided.

  In addition, a gas rectifying cylinder 11 is provided inside the main chamber 1 to block radiation from the silicon melt 4 to the silicon single crystal 3 and rectify the gas in the main chamber 1. A heat shield member 12 is installed at the lower part of the cylinder 11 so as to face the entire surface of the silicon melt 4 so as to cut off radiation from the surface of the silicon melt 4 and to keep the surface of the silicon melt 4 warm. Yes. Further, in the single crystal manufacturing apparatus of the present embodiment, as shown in FIG. 1, the lower end of the wire 31 penetrating the main chamber 1 is attached to the upper part of the gas rectifying cylinder 11 and provided outside the main chamber 1. The gear 32 (not shown) around which the wire 31 is wound is rotationally driven by the motor 32 so that the heat shield member 12 is movable in the vertical direction.

  A magnetic field generator (magnetic field applying means) 17 that applies a magnetic field to the quartz crucible 5 is provided outside the main chamber 1 so as to surround the main chamber 1. The magnetic field generator 17 generates, for example, a horizontal magnetic field toward the quartz crucible 5 and is composed of an electromagnetic coil or the like. The magnetic field generator 17 can be configured to apply a horizontal magnetic field to the quartz crucible 5, but a cusp magnetic field, which is a magnetic field configuration formed when a current in the reverse direction is passed through a pair of circular coils, is applied to the quartz crucible. 5 may be provided.

  A convection control member 35 is disposed in the silicon melt 4. The convection control member 35 is in a state when the depth La of the silicon melt 4 is the vertical distance Lb between the lowermost portion of the convection control member 35 and the melt surface 4a at the start of pulling. Thus, the convection of the silicon melt 4 is controlled. The position of the convection control member 35 relative to the melt surface 4a does not change from the start of pulling up until the depth La of the silicon melt 4 becomes less than the distance Lb due to the decrease in the silicon melt 4 accompanying pulling. It is supported and controlled by 18. In the present embodiment, the lowermost portion of the convection control member 35 is a portion close to the central axis 15 of the silicon single crystal 3 in the plate-like piece 36 constituting the convection control member 35 as shown in FIG. The central angle 36d of the plate-like piece 36 is.

  FIG. 2 is a plan view of a convection control member provided in the single crystal manufacturing apparatus shown in FIG. In FIG. 2, the outer diameter of the silicon single crystal is shown together to facilitate explanation of the shape of the convection control member. FIG. 3 is a view for explaining the plate-like piece constituting the convection control member, in which FIG. 3 (a) is a plan view of the plate-like piece, and FIG. 3 (b) is a drawing of the plate-like piece. It is plate-shaped sectional drawing cut | disconnected on the line | wire which passes along the length direction center and center axis | shaft of an arc-shaped edge. FIG. 4 is a perspective view for explaining the relationship between the expansion and contraction of the support bar and the angle adjusting means and the movement of the plate-like piece.

  As shown in FIG. 2, the convection control member 35 is a plate having a circular shape in plan view with the center axis 15 of the silicon single crystal 3 to be pulled up as the center 15. The convection control member 35 changes the angle α when moved up and down or as described later. It has a size slightly smaller than the inner diameter of the quartz crucible 5 to the extent that it does not come into contact with the quartz crucible 5 and is composed of six plate-like pieces 36 divided into six on the line starting from the central axis 15. . The six plate-like pieces 36 are formed in the same fan shape made of quartz, which is the same material as the quartz crucible 5, and the angle of the fan-shaped central angle 36d is 60 °. Further, as shown in FIG. 1, the upper surface 36 a of the plate-like piece 36 located in the vicinity of the central axis 15 can change an angle α formed with the central axis 15 in a cross section along the central axis 15. And in the single crystal manufacturing apparatus of this embodiment, the convection of the silicon melt 4 is controlled by controlling the angle α.

The angle α can be in the range of 0 to 180 °, and is determined according to the inner diameter and amount of residual liquid of the quartz crucible 5 and the target quality of the single crystal to be manufactured, but is not particularly limited, but is 60 to 120 °. It is desirable to be in the range. By controlling the angle α and forming a plane or conical surface centered on the central axis 15 on the upper surface side of the convection control member 35, the convection of the silicon melt at the time of pulling up can be controlled. The shape of the melt surface at the time can be made upward or downward, or the height of the protrusion can be adjusted. Therefore, the quality of the target silicon single crystal 3 such as the oxygen concentration can be appropriately controlled.
As shown in FIG. 1, by setting the angle α to 90 °, it is possible to realize a convection region having a shape substantially parallel to the bottom of the quartz crucible 5 and within a depth Lb described later.
In this case, the convection control member 35 and the quartz crucible inner surface are most easily connected. Since the change in melt convection between the state with and without the convection control member is the smallest, the defect distribution in the first half of the crystal (with the convection control member 35) and the second half of the crystal (without the convection control member 35) Changes in quality such as oxygen concentration are minimized.

FIG. 5 is a diagram showing a part of the manufacturing process of the silicon single crystal, and shows a state in which the silicon single crystal is pulled up by making the angle α smaller than 90 °. As shown in FIG. 5, when the angle α is smaller than 90 °,
Secondary convection is (large)
Solid-liquid interface (lower convex → upper convex)
Oxygen concentration (increase)
COP concentration (decrease)
Dopant concentration (increase)
Resistivity (decrease)
There is a tendency to change.
FIG. 6 is a diagram showing a part of the manufacturing process of the silicon single crystal, and is a diagram showing a state in which the angle α is larger than 90 ° and the silicon single crystal is pulled up. As shown in FIG. 6, when the angle α is larger than 90 °,
Secondary convection is (small)
Solid-liquid interface (upward → downward)
Oxygen concentration (decrease)
COP concentration (increase)
Dopant concentration (decrease)
Resistivity (increase)
There is a tendency to change.
Therefore, the value of the angle α can be sequentially set in consideration of these. Of course, the control of these parameters is not limited to the temperature conditions, the structure of the insulation material in the furnace, the rotation of the crucible and the single crystal, the pulling speed, the furnace pressure, the gas flow rate in the furnace, the gas composition, the magnetic field application state, etc. It is preferable to work in conjunction with parameters.

  In FIG. 1 and FIG. 2, the center angle 36d of the six plate-like pieces 36 is opposed to each other across the central axis 15, and the center angles 36d of the plate-like pieces 36 are separated from each other. ing. However, since the position of the central angle 36d of the plate-like piece 36 changes in conjunction with the change of the angle α, by controlling the angle α, the center of the plate-like piece 36 opposed across the central axis 15 is controlled. The corners 36d may be in contact with each other or separated from each other. Further, when the angle α is controlled, at least a part of at least two of the six plate-like pieces 36 overlap each other in the vicinity of the central axis 15 when viewed in plan. There is also.

  Further, as shown in FIG. 3B, the cross-sectional shape of the plate-like piece 36 is a flat plate in the region located in the vicinity of the central axis 15, and the plate-like piece 36 has an arcuate edge 36 c. As it goes, it first curves upward with a predetermined curvature indicated by reference numeral r1 in FIG. 3B, and further upwards with a curvature indicated by reference numeral r2 in FIG. 3B, which is smaller than the curvature indicated by reference numeral r1. 3b, which is smaller than the curvature indicated by reference numeral r1, is curved downward with the curvature indicated by reference numeral r3 in FIG. 3B, and has a gentle S-shaped cross-sectional shape as a whole. It is in a state close to the bottom shape.

The dimension of the convection control member 35 can be set to the dimension shown below, for example.
Radius _{R 3} of the convection controlling member 35 in a plan view, the inner surface diameter of the quartz crucible 5 is a 0.05～0.5Fai ₀ When phi _0, and preferably from 0.15～0.45Fai ₀ . Further, the curvature in the cross-sectional direction of the plate-like piece 36 is, in order from the side closer to the central axis 15, the curvature r1 is 0.1 when the curvature of the large curved portion (bottom surface portion) near the bottom center of the quartz crucible 5 is R _0. -5R ₀ , preferably 0.5-1.5R _0, and the curvature r2 is r ₀ when the curvature of the small curved portion (the rising portion connected from the external part to the side wall) near the bottom outer edge of the quartz crucible 5 is r _0. 0.01 to 5r ₀ , preferably 0.5 to 1.5r _0, and the curvature r3 is the plate-like piece 36 when the tangential plane at the fan-shaped tip position on the upper surface of the plate-like piece 36 is horizontal. Is set so that the tangent plane at the position of the fan-shaped outer edge is substantially horizontal and these both tangent planes are parallel, specifically 0.01 to 5r ₀ , preferably 0.5 to 1. .5r ₀ .
The thickness t of the plate-like piece 36 is preferably 1 to 100 mm, and more preferably 5 to 30 mm. The plate-like pieces 36 have substantially the same shape, and are symmetric with respect to the long axis of the silicon single crystal when the tangential plane at the fan-shaped tip position on the upper surface of the plate-like piece 36 is horizontal as the convection control member 35. It comes to become.

  Further, as shown in FIGS. 2 and 3A, the upper surface 36b of the plate-like piece 36 is outside the outer diameter 3a of the silicon single crystal 3 when viewed in plan and more than the inner wall of the quartz crucible 5. One end 18 a of a support bar 18 that supports the plate-like piece 36 so as to be movable in the direction of the central axis 15 is attached to the inner position. As shown in FIGS. 3A and 3B, the lower end 18 a of the support bar 18 is a substantially horizontal tubular shape, and is provided on the upper surface 36 b of the plate-like piece 36 and the rotation axis of the plate-like piece 36. The plate-like piece 36 can be freely changed in angle α by being fitted into a joint member 18b that is integrated with the shaft portion and is connected to the upper face of the plate-like piece 36 with the shaft portion being separated from the upper face of the plate-like piece 36. It is attached to become. This joining member 18b is provided at the center position of the fan-shaped arc on the upper surface of the plate-like piece 36 and in the vicinity of the outer edge of the portion having the curvature r3.

  As shown in FIG. 2, the position of the support bar 18 on the upper surface 36b of the plate-like piece 36 is outside the outer diameter 3a of the silicon single crystal 3 and inside the inner wall of the quartz crucible 5 when viewed in plan. The position is not particularly limited as long as it is a position, but it is desirable that the position is on a line A passing through the center in the length direction of the arc-shaped edge 36c of the plate-like piece 36 and the central axis 15 when viewed in plan. By setting the position of the support bar 18 on the upper surface 36b of the plate-shaped piece 36 to the above position, the load of the plate-shaped piece 36 is applied to the support bar 18 in a balanced manner in the extending direction of the edge 36c. .

  In addition, as shown in FIGS. 1, 2 and 3A, the plate-like piece 36 is located at a position overlapping with the plate-like piece 36 on a line A passing through the support rod 18 starting from the central axis 15 when seen in a plan view. A rod-shaped angle adjusting means 38 that is extendable in the direction of the central axis 15 with the lower end 38a in contact with the piece 36 is provided. In the single crystal manufacturing apparatus according to the present embodiment, as described later, the angle α between the top surface tangent plane of the plate piece 36 and the central axis 35 is interlocked with the expansion and contraction of the angle adjusting means 38. Has been changed.

Further, the position of the angle adjusting means 38 on the upper surface 36b of the plate-like piece 36 is not particularly limited as long as it overlaps the plate-like piece 36 on the line A shown in FIG. 3A, and FIG. 3 (b), as shown in FIG. 4, be an arrangement to be shorter than the distance R ₂ of the distance R ₁ is the central axis 15 and the angle adjusting means 38 of the central shaft 15 and the support rod 18 Alternatively, the distance R ₁ between the central axis 15 and the support rod 18 may be longer than the distance R ₂ between the central axis 15 and the angle adjusting means 38.

  Further, as shown in FIG. 4, the support rod 18 and the angle adjusting means 38 are both the upper rod members 18d and 38d that are not immersed in the silicon melt, and the tip members that are provided at the lower ends thereof and can be immersed in the silicon melt. 18c, 38c. In the present embodiment, the tip members 18c and 38c are made of quartz rods and are arranged below, and the rod members 18d and 38d are made of carbon and are arranged above. Further, upper ends 18 e and 38 e of the support rod 18 and the angle adjusting means 38 are provided so as to penetrate the support member 22 and the main chamber 1.

  The support member 22 is made of carbon, and is an annular plate that supports the support rod 18 and the angle adjusting means 38 so as to be movable up and down at an appropriate planar position inside the outer core of the main chamber 1 and above the quartz crucible 5. As shown in FIG. 1, the outer diameter when the support member 22 is viewed in plan is formed larger than the inner diameter of the annular upper heat insulating material 8 a extending inward from the top end of the heat insulating material 8. It is formed to be larger than the region overlapping the flow straightening cylinder 11 and the heat shield member 12. Further, as shown in FIGS. 1 and 4, an enlarged diameter portion 18 f formed by expanding the outer diameter of the rod member 18 d is formed at the lower end portion of the rod member 18 d of the support rod 18. As shown in FIGS. 1 and 4, the outer diameter of the enlarged diameter portion 18 f is larger than the inner diameter of the hole 22 a through which the support rod 18 of the support member 22 passes.

As shown in FIG. 1, the support member 22 is placed on the upper heat insulating material 8 a when the expanded diameter portion 18 f of the support bar 18 is located below the upper heat insulating material 8 a. When the enlarged diameter portion 18f is at a position above the upper heat insulating material 8a, the enlarged diameter portion 18f moves in conjunction with the vertical movement of the support bar 18 while being supported by the enlarged diameter portion 18f. Therefore, the region located around the support rod 18 and the angle adjusting means 38 when viewed in plan can be effectively kept warm by the support member 22. In addition, when the plate-like piece 36 is moved up and down, the support member 22 does not come into contact with the plate-like piece 36 and cause trouble.
Further, as shown in FIG. 1, motors 41 and 40 are arranged outside the main chamber 1, and by operating the motor 41, the support rod 18 is expanded and contracted in the direction of the central axis 15 to operate the motor 40. By doing so, the angle adjusting means 38 is expanded and contracted in the direction of the central axis 15.

The lengths h ₁ and h ₂ of the support rod 18 and the tip members 18c and 38c of the angle adjusting means 38 shown in FIG. 4 are not particularly limited. For example, the depth of the silicon melt 4 at the start of pulling is L ₀ . Then is the 0.1~1.8L _0, and preferably from 0.2~1.5L _0. Note that the lengths h ₁ and h ₂ of the tip members 18c and 38c may be the same or different.
The thicknesses φ ₁ and φ ₂ of the support rod 18 and the tip members 18c and 38c of the angle adjusting means 38 shown in FIG. 4 are not particularly limited as long as sufficient strength can be obtained. ˜300 mm, preferably 5˜80 mm. The thicknesses φ ₁ and φ ₂ of the tip members 18c and 38c may be the same or different.

In the present embodiment, the height H of the region where the plate-like piece 36 is installed in the direction of the central axis 15 is, for example, the height from the lower end of the cylindrical body of the quartz crucible 5 to the bottom of the quartz crucible 5. of the set to 0.1～1.8H ₀ When H _0, and preferably from 0.1~1.2H _0.

  In addition, the shape of the plate-like piece 36 constituting the convection control member 35 is not limited to the above shape. For example, the central axis 15 is placed on the upper surface side of the convection control member 35 by controlling the angle α. A parabolic shape or a spherical shape with a center can be formed. By controlling the angle α to form a paraboloid or a spherical surface centered on the central axis 15 on the upper surface side of the convection control member 35, the convection of the silicon melt at the time of pulling can be controlled. The shape of the melt surface at the time can be made upward or downward, or the height of the protrusion can be adjusted. Therefore, the quality of the target silicon single crystal 3 such as defect distribution and oxygen concentration can be appropriately controlled.

In the single crystal pulling apparatus of the present invention, the number of plate-like pieces 36 can be 3 to 36, preferably 4 to 12, and 6 as shown in FIG. Is more preferable.
As the number of the plate-like pieces 36 increases, the shape of the upper surface side of the convection control member 35 formed by controlling the angle α becomes more spherical and becomes a more precise protrusion in the circumferential direction around the axis. This is preferable because the convection of the silicon melt 4 in the above can be controlled uniformly and precisely without variation in the circumferential direction. Furthermore, as the number of the plate-like pieces 36 increases, the area when the plate-like pieces 36 are viewed from above with the plate-like pieces 36 suspended from the support rod 18 is reduced. Since it becomes difficult to contact the silicon single crystal 3 and the gas flow straightening cylinder 11, the plate-like piece 36 can be easily pulled up.
Further, the smaller the number of plate-like pieces 36, the smaller the number of support rods 18 and angle adjusting means 38, so that the support rod 18 and angle adjusting means 38 can control the inert gas introduced into the main chamber 1. The possibility of causing trouble can be reduced, and the possibility of contamination in the main chamber 1 due to the support rod 18 and the angle adjusting means 38 being disposed in the main chamber 1 can be reduced.
By setting the number of divisions of the plate-like piece 36 to 4 to 12, the convection of the silicon melt 4 at the time of pulling can be precisely controlled, the plate-like piece 36 can be easily lifted, and the cleanness in the main chamber 1 can be achieved. This can prevent the control of the inert gas introduced into the main chamber 1 from being hindered.

Further, the depth La of the silicon melt 4 varies depending on the decrease of the silicon melt 4 accompanying the pulling. The depth La of the silicon melt 4 at the start of pulling is determined by the diameter and length of the silicon single crystal 3 to be pulled up, the shape of the quartz crucible 5 and the like, and is not particularly limited. In the case of pulling up the single crystal 3, it is 0 to 1000 mm, preferably 5 to 800 mm.
The vertical distance Lb between the lowermost part of the convection control member 35 and the melt surface 4a at the start of pulling is the convection range directly below the solid-liquid interface that affects the quality of the grown single crystal. is set as the vertical distance, for example, the depth La of the silicon melt 4 at the pulling start is the 0.1～1.0L ₀ When L _0, is preferably a 0.3～0.8L ₀ The Here, the distance Lb is set when the angle α is 90 ° for the plate-like piece 36, and strictly speaking, when the angle α is set to other than 90 °, the distance Lb protrudes from the range of Lb as the convection control member 35. It is also possible. The distance Lb is preferably set as a range in which the rate of change during pulling up of the magnetic field distribution applied by the magnetic field generator 17 (magnetic field applying means) is 40% or less. The rate of change during the pulling of the magnetic field distribution is preferably set to 40% or less, more preferably 30% or less, or 20% or less.

  Further, an inert gas such as argon gas can be introduced from the gas inlet 10 provided at the upper portion of the pulling chamber 1, and after passing between the silicon single crystal 3 being pulled and the gas rectifying cylinder 11, the gas is blocked. The heat member 12 and the melt surface 4 a of the silicon melt 4 can be passed between and discharged from the gas outlet 9.

In order to grow a silicon single crystal by the CZ method using such a single crystal pulling apparatus 30, first, a silicon raw material is accommodated and filled in the quartz crucible 5, and the heater 7 is used in the quartz crucible 5. A silicon raw material is heated and melted to obtain a silicon melt 4.
Next, by operating the motor 41 to expand and contract the support rod 18, each of the six plate-like pieces 36 supported by the support rod 18 is moved in the vertical direction, so that a predetermined height position in the silicon melt 4 is obtained. To place. In this case, it is preferable that the angle α of the plate-like piece 36 is about 90 ° to 180 ° or about 120 ° so that the convection control member 35 is gently immersed in the silicon melt 4. A range is also acceptable.

Subsequently, the motor 40 is operated so that the lower ends 38a of the angle adjusting means 38 are brought into contact with the six plate-like pieces 36, respectively, and the angle adjusting means 38 is expanded and contracted to thereby extend the central axis of each plate-like piece 36. 1 is moved in the direction of the central axis 15 so that the angle α shown in FIG. 1 of each plate-like piece 36 is 90 °.
In the present embodiment, the angle α shown in FIG. 1 is changed in conjunction with the expansion and contraction of the angle adjusting means 38. More specifically, as shown in FIG. 4, when the angle adjusting means 38 with the lower end 38a in contact with the plate-like piece 36 is expanded and contracted, the height position of the lower end of the angle adjusting means 38 and the lower end of the support bar 18 are The plate-like piece 36 is rotated by the action of the rotational moment of the plate-like piece 36 due to the weight of the plate-like piece 36 by the expansion and contraction of the length of the angle adjusting means 38 in the chamber from the relationship with the rotational axis height position. Thus, the angle α is changed in the direction in which the tip of the plate-like piece 36 moves up and down. Specifically, when the angle adjusting means 38 having the lower end 38a in contact with the plate-like piece 36 is shortened and moved upward, the position where the angle adjusting means 38 comes into contact with the plate-like piece 36 changes, and the angle α And the tip of the plate-like piece 36 is lowered downward, and the convection control longitudinal section 35 is in a convex state. Further, when the angle adjusting means 38 moves downward, the position where the angle adjusting means 38 abuts on the plate-like piece 36 changes, the angle α decreases, the tip of the plate-like piece 36 rises upward, and convection control is performed. The longitudinal section 35 is convex upward.

In this way, the six plate-like pieces 36 are respectively arranged at predetermined positions in the silicon melt 4 at positions added Lb from the surface of the silicon melt 4, and as shown in FIG. Is set to 90 ° C., and the convection control member 35 having a plane centered on the central axis 15 on the upper surface side is disposed in the silicon melt 4.
Next, by operating the motor 32 to rotate the gear to adjust the length of the wire 31, the gas rectifying cylinder 11 and the heat shield member 12 are moved in the vertical direction, and a predetermined height in the main chamber 1 is increased. Place in the position.

  Subsequently, the magnetic field generator 17 is operated to start application of a magnetic field such as a horizontal magnetic field into the quartz crucible 5, and the temperature of the silicon melt 4 is raised and adjusted to the start temperature. The timing for starting the application of the magnetic field can be appropriately selected according to the target quality of the silicon single crystal 3 to be grown. The strength of the applied magnetic field is preferably set to 1000 G or more when the maximum strength is a horizontal magnetic field at the time of pulling up. In addition, the cusp magnetic field is preferably set so that the magnetic field strength at the intersection (substantially a plane circle) between the neutral surface and the inner surface of the quartz crucible is about 50G. Further, the height position of the magnetic field center can be in the range from the upper end to the bottom of the quartz crucible 5 at the time of pulling up, and when it is in the vicinity of the melt surface 4a of the silicon melt 4, convection of the silicon melt is effective. It is desirable that it can be suppressed. Here, the height position of the magnetic field center means the height position of the center of the magnetic field generating coil in the case of a horizontal magnetic field, and in the case of a cusp magnetic field, the vertical and horizontal magnetic field components are zero. Means a position. In addition, it can be changed appropriately before or after the completion of melting according to the characteristics of the single crystal to be pulled up (start timing, strength, maximum strength position height, etc.) and the filling and melting state of the silicon raw material. .

Thereafter, the single crystal pulling step is started as shown below.
That is, the quartz crucible 5 is rotated at a predetermined speed by the crucible drive mechanism 21, the seed crystal 16 fixed to the wire 14 is immersed in the silicon melt 4 in the quartz crucible 5, and gently pulled up while rotating to seed the seed Then, the silicon single crystal 3 having a substantially cylindrical straight body portion is grown by expanding the diameter to a desired diameter. The crystal rotation can be set to an arbitrary value depending on the characteristics of the crucible and the pulled crystal.
In the present embodiment, the silicon single crystal 3 is pulled up by applying a horizontal magnetic field from the magnetic field generator 17 into the quartz crucible 5 and also against the melt surface 4 a of the convection control member 35 disposed in the silicon melt 4. The position is controlled in such a manner that the depth La of the silicon melt 4 does not change from the start of the pulling up until the point where the depth La becomes less than the distance Lb due to the decrease in the silicon melt 4 accompanying the pulling.

  In the present embodiment, the vertical height of the melt surface 4 a during the pulling of the silicon single crystal 3 is controlled by the crucible drive mechanism 21 to be constant. Therefore, the position of the convection control member 35 relative to the melt surface 4a during the pulling of the silicon single crystal 3 is determined by the crucible drive mechanism 21 so that the depth La of the silicon melt 4 is increased from the start of the pulling of the silicon melt 4 accompanying the pulling. Control is performed so as not to change until the time when the distance becomes less than the distance Lb. The crucible drive mechanism 21 can be controlled using position control means (not shown). The position control means includes, for example, the position of the quartz crucible 5, the position of the convection control member 35 measured by a CCD camera, the position of the melt surface 4a of the silicon melt 4, the pulling length of the silicon single crystal 3, the temperature in the chamber In addition, the position of the quartz crucible 5 in the vertical direction is moved by the crucible driving mechanism 21 in accordance with information such as the surface temperature of the silicon melt 4 and the gas flow rate.

  In the present embodiment, the method of controlling the position of the convection control member 35 relative to the melt surface 4a during the pulling of the silicon single crystal 3 by the crucible drive mechanism 21 has been described as an example. The position of the convection control member 35 with respect to the melt surface 4a during the pulling may be adjusted by the support bar 18 and the angle adjusting means 38 as shown below. That is, the position of the convection control member 35 with respect to the melt surface 4a is maintained in the vertical position of the angle adjusting means 38 with respect to the individual plate pieces 36, in other words, from the angle adjusting means 38 to the individual plate pieces 36. In a state in which the force applied to is fixedly controlled, both the support bar 18 and the angle adjusting means 38 may be moved up and down for adjustment.

Thereafter, the growth of the silicon single crystal 3 is continued, and it is necessary as a convection control member pulling process when the depth La of the silicon melt 4 becomes less than the distance Lb due to the decrease of the silicon melt 4 accompanying the pulling. If there is, the gas rectifying cylinder 11 and the heat shield member 12 are pulled up to a height position with a low risk of contact with the plate-like piece 36 when the plate-like piece 36 is pulled up by the wire 31. At this time, the convection control member 35 can be pulled up at a speed of about 0.1 to 300 mm / min so as not to affect the single crystal growth.
Further, if there is no problem in pulling up the convection control member 35 without pulling up such as when the number of divisions of the plate-like pieces 36 is large, the gas rectifying cylinder 11 and the heat shield member 12 may not be pulled up. Further, the tip of the plate-like piece 36 can be moved to a position outside the quartz crucible 5 in plan view so that the silicon melt adhering to the plate-like piece 36 does not drop into the quartz crucible 5.
Next, as shown in FIG. 7, both the support rod 18 and the angle adjusting means 38 are moved upward, and the convection control member 35 is pulled up, thereby causing the convection control member 35 to hinder the growth of the silicon single crystal 3. Move it to a height where it will not be touched. The raised convection control member 35 can be reused by being cooled by an appropriate cooling method.
Thereafter, the gas flow straightening cylinder 11 and the heat shield member 12 are pulled down to a predetermined height position suitable for growing the silicon single crystal 3 by the wire 31, and the single crystal pulling process is continued.

  In the present embodiment, the convection control member 35 disposed in the silicon melt 4 is composed of six plate-like pieces 36 divided on a line starting from the central axis 15 when viewed in plan, and the central axis 15, the angle α formed between the upper surface 36 a of the plate-like piece 36 located in the vicinity of the central axis 15 and the central axis 15 can be changed. Therefore, when the angle α is appropriately controlled, the angle α can be changed. The convection of the silicon melt 4 can be effectively controlled. Therefore, a single crystal having a desired quality such as a defect state of the single crystal and a dopant concentration in the single crystal can be manufactured with a high yield.

  Further, in the present embodiment, the convection of the silicon melt 4 when the silicon melt 4 during the pulling of the silicon single crystal 3 is large and the depth La of the silicon melt is deeper than the distance Lb. The convection control member 35 is controlled so as to be in a state where the depth La of the silicon melt 4 is the distance Lb. Therefore, in this embodiment, the fluctuation of the convection of the silicon melt 4 from the start of the pulling up to the time when the amount of the silicon melt 4 being pulled becomes less than the distance Lb becomes very small. As a result, the quality difference of the silicon single crystal 3 depending on the amount of the remaining silicon melt 4 can be made very small.

  Furthermore, in this embodiment, since the silicon single crystal 3 is pulled up while applying a magnetic field by the magnetic field generator 17 that controls the convection of the silicon melt 4, the convection of the silicon melt 4 is more effectively suppressed. Can do.

  The present invention is not limited to the above-described example. For example, when pulling up the silicon single crystal 3, the surface of the melt of the convection control member 35 is pulled by pulling up the silicon single crystal 3 while controlling the angle α. You may change the position with respect to 4a suitably. Even in this case, the convection of the silicon melt can be appropriately controlled, and the quality difference of the single crystal depending on the remaining amount of the silicon melt can be reduced. In addition, since the single crystal manufacturing apparatus of the present invention can change the shape of the convection control member 35 without removing the convection control member 35 from the silicon melt 4, the silicon single crystal 3 can be formed while controlling the angle α. Even when it is pulled up, the cleanliness in the main chamber 1 is not hindered.

  In the example described above, the pulling up of the silicon single crystal 3 is controlled so that the position of the convection control member 35 relative to the melt surface 4a does not change until the depth La of the silicon melt 4 becomes less than the distance Lb. However, the position of the convection control member 35 with respect to the melt surface 4a is controlled so as not to change until the depth La of the silicon melt 4 becomes, for example, 50-30% of the depth La at the start of pulling. May be performed. In this case, the melt convection pattern directly under the crystal becomes constant, and a silicon single crystal ingot having a uniform quality such as defect distribution and oxygen concentration depending on the crystal axis direction is easily manufactured.

"Experiment 1"
Using the single crystal pulling apparatus 30 shown in FIG. 1, the relationship between the yield and the solidification rate when the silicon single crystal 3 having a diameter of 200 mm was grown by the CZ method was obtained by simulation analysis.
The yield here refers to the pass rate when the pulling rate V when growing the silicon single crystal is within the range of V ₀ ± 0.01 (mm / min) as the pass rate, the solidification rate of 0.025. The value obtained every time. This is because when the pulling speed is within the above range, a single crystal capable of manufacturing a defect-free wafer without crystal defects such as COP is pulled in the actual pulling.
Specifically, for example, if the maximum speed at which a _COP does not occur during a test is defined as V _COP and the minimum speed at which no LD (large dislocation) occurs is defined as V _LD , the pulling speed V ₀ = ( V _COP + V _LD ) / 2.
The pulling conditions excluding the pulling speed V were conditions for growing a silicon single crystal having a defect-free region over the entire length of the pulling length (solidification rate) as shown below.
That is, the distribution difference ΔG = −0.03 to 0.03G _{0 in} the radial direction of the crystal temperature gradient G (° C./mm) in the pulling axis direction near the solid-liquid interface when growing a silicon single crystal (where G ₀ is V / G (mm ² / ° C./min), which is the ratio between the pulling rate V (mm / min) and the crystal temperature gradient G (° C./mm) when growing a silicon single crystal ) Radial distribution difference Δ (V / G) = − 0.005 to 0.005, and using a condition optimized to obtain the highest pass rate when the solidification rate is 5%, a silicon single crystal The pulling conditions were not changed according to the solidification rate during pulling.
Further, the angle α shown in FIG. 1 is set to 90 °, and the position La of the convection control member 35 with respect to the melt surface 4a during pulling of the silicon single crystal 3 is less than the distance Lb when the depth La of the silicon melt 4 starts pulling. It was assumed that it did not change until that time.
The specific conditions are
α = 90 °
Lb = 180mm
La (initial value) = 400 mm
La (end value) = 30 mm
Crucible inner diameter = 600 mm
Lifting length = 3000mm
Crystal rotation = 10 rpm
Crucible rotation = 1 rpm

"Experimental example 2"
Using the same single crystal pulling apparatus as in Experimental Example 1 except that the convection control member 35 and the supporting means are not provided, the yield solidification when the silicon single crystal 3 is grown by the CZ method as in Experimental Example 1 The relationship with the rate was obtained by simulation analysis. The pulling conditions here were the same as in Experimental Example 1 except for Lb.

"Experiment 3"
The relationship with the yield solidification rate when the silicon single crystal 3 is grown by the CZ method in the same manner as in Experimental Example 1 using the same single crystal pulling apparatus as in Experimental Example 1 except that the convection control member 35 is not provided. Was obtained by simulation analysis. The pulling conditions here were optimized so as to obtain the highest pass rate when the solidification rate was 95%.
The specific conditions are
La (initial value) = 400 mm
La (end value) = 30 mm
Crucible inner diameter = 600 mm
Lifting length = 3000mm
Crystal rotation = 10 rpm
Crucible rotation = 1 rpm

The results of Experimental Examples 1 to 3 are shown in FIG. FIG. 8 is a graph showing the relationship between the pass rate and the solidification rate in the silicon single crystals of Experimental Examples 1 to 3.
As shown in FIG. 8, in Experimental Example 1, a high pass rate of 70% or more was obtained regardless of the solidification rate, and the difference in pass rate depending on the solidification rate was small.
Moreover, from FIG. 8, in Experimental Example 2 using conditions optimized to obtain the highest pass rate when the solidification rate is 5%, the pass rate gradually decreases as the solidification rate increases. Compared with Experimental Example 1, the difference in the pass rate depending on the solidification rate was very large. In Experimental Example 3 using conditions optimized to obtain the highest pass rate when the solidification rate is 95%, the pass rate gradually increases as the solidification rate increases. Compared with 1, the difference in the pass rate depending on the solidification rate became very large.
As described above, in Experimental Example 1 including the convection control member 35, the difference in the acceptance rate depending on the solidification rate is smaller than in Experimental Example 2 and Experimental Example 3 that do not include the convection control member 35. It has been confirmed that the provision of the convection control member 35 can reduce the quality difference of the single crystal depending on the remaining amount of the silicon melt.

"Experimental example 4"
Using the single crystal pulling apparatus 30 shown in FIG. 1, the relationship between the specific resistance and the solidification rate when an arsenic dopant silicon single crystal 3 having a diameter of 150 mm was grown by the CZ method was determined by simulation analysis.
The pulling conditions excluding the pulling speed V were not changed according to the solidification rate during pulling of the silicon single crystal.
The specific conditions are
α = 90 °
Lb = 100mm
La (initial value) = 300 mm
La (end value) = 30 mm
Crucible inner diameter = 450 mm
Lifting length = 3000mm
Crystal rotation = 10 rpm
Crucible rotation = -10 rpm

“Experimental Example 5”
Specific resistance when the silicon single crystal 3 is grown by the CZ method in the same manner as in Experimental Example 4 using the same single crystal pulling apparatus as in Experimental Example 4 except that the convection control member 35 and the supporting means are not provided. The relationship between the solidification rate and the solidification rate was obtained by simulation analysis. The pulling conditions here were the same as in Experimental Example 1 except for Lb.

  The results of Experimental Example 4 to Experimental Example 5 are shown in FIG. FIG. 9 is a graph showing the relationship between the specific resistance and the solidification rate of the silicon single crystals of Experimental Example 4 to Experimental Example 5 when the maximum value of the specific resistance of Experimental Example 5 is set to 100. As shown in FIG. 9, in the experimental example 4 including the convection control member 35 and the support means, the difference in resistivity depending on the solidification rate is compared with the experimental example 5 not including the convection control member 35 and the support means. Therefore, it was confirmed that the quality difference of the single crystal depending on the remaining amount of the silicon melt can be reduced by providing the convection control member 35 and the supporting means.

FIG. 1 is a schematic cross-sectional view of a single crystal manufacturing apparatus according to a first embodiment of the present invention. FIG. 2 is a plan view of a convection control member provided in the single crystal manufacturing apparatus shown in FIG. 3A and 3B are diagrams for explaining the plate-like piece constituting the convection control member. FIG. 3A is a plan view of the plate-like piece, and FIG. 3B is an arc shape of the plate-like piece. It is plate-shaped sectional drawing cut | disconnected on the line | wire which passes along the length direction center and center axis | shaft of the edge part. FIG. 4 is a perspective view for explaining the relationship between the expansion and contraction of the support bar and the angle adjusting means and the movement of the plate-like piece. FIG. 5 is a diagram showing a part of the manufacturing process of the silicon single crystal, and is a diagram showing a state in which the silicon single crystal is pulled up by making the angle α smaller than 90 °. FIG. 6 is a view showing a part of the manufacturing process of the silicon single crystal, and is a view showing a state where the angle α is larger than 90 ° and the silicon single crystal is pulled up. FIG. 7 is a diagram showing an implementation state when the amount of residual liquid is smaller than that of the device of the present invention (when the crystal bottom and the convection control device are pulled up). FIG. 8 is a graph showing the relationship between the pass rate and the solidification rate in the silicon single crystals of Experimental Examples 1 to 3. FIG. 9 is a graph showing the relationship between the specific resistance and the solidification rate in the silicon single crystals of Experimental Examples 4 to 5.

Explanation of symbols

1: main chamber, 3: silicon single crystal, 2: pulling chamber, 4: silicon melt, 4a: melt surface, 5: quartz crucible, 6: graphite crucible, 7: heater, 11: gas rectifying cylinder, 12 : Heat shield member, 13: holding shaft, 15: central shaft, 17: magnetic field generator (magnetic field applying means), 18: support rod, 18b: joining member, 18c, 38c: tip member, 18d, 38d: rod member, 21: crucible drive mechanism, 30: single crystal manufacturing apparatus, 14, 31: wire, 32, 40, 41: motor, 35: convection control member, 36: plate-like piece, 36a, 36b: upper surface, 36c: edge, 36d: Center angle, 38: Angle adjusting means.

Claims (12)

In a single crystal manufacturing apparatus for growing while pulling up a silicon single crystal from a silicon melt contained in a crucible,
A convection control member that is a plate-like body that can be arranged in the silicon melt, and a support means for supporting the convection control member from above the crucible,
The convection control member has a substantially disk shape that can be positioned substantially in parallel with the bottom surface of the crucible, and extends to an outer edge centering on a central axis position of the silicon single crystal that is pulled up in plan view. It consists of multiple plate-like pieces divided by line segments,
The supporting means can control the convection of the silicon melt by setting an angle α between a tangent plane of the upper surface of the plate-like piece at the center and a downward direction in the central axis in a cross section along the central axis. The apparatus for producing a single crystal is characterized in that the plate-like piece of the convection control member is supported so that the angle can be adjusted. The support means is configured to move the plate-like piece so that the tip of the plate-like piece on the center axis side can move up and down at a position on the upper surface of the plate-like piece on the outer side of the silicon single crystal and on the inner wall of the crucible. A support bar vertically suspended to support the rotation;
One end can be brought into contact with the upper surface of the plate-like piece on the outer edge side in a plan view of the support rod, and the rod has a rod-shaped angle adjusting means that can expand and contract in parallel with the support rod.
2. The single crystal manufacturing apparatus according to claim 1, wherein the angle α of the plate-like piece can be set in a range of 0 to 180 ° by expanding and contracting the angle adjusting means.   When the angle α is set so that the convection control member is substantially parallel to the bottom of the crucible, the convection range directly below the solid-liquid interface that affects the quality of the single crystal grown in the silicon melt is the vertical distance. When the depth La, which is the distance between the silicon melt surface and the bottom surface of the crucible, exceeds the distance Lb so that it is within Lb, the convection control member has a distance Lb from the solid-liquid interface. The single crystal manufacturing apparatus according to claim 1, wherein the single crystal manufacturing apparatus is provided so as to be positioned at a depth. Magnetic field applying means for controlling the convection of the silicon melt,
The single crystal manufacturing apparatus according to claim 3, wherein the distance Lb is set as a range in which a rate of change during pulling of the magnetic field distribution applied by the magnetic field applying unit is 40% or less.   2. The heat shield member disposed on the upper side of the silicon melt, wherein the heat shield member is movable in the vertical direction when the convection control member moves in the vertical direction. The single crystal manufacturing apparatus according to claim 4.   The single crystal manufacturing apparatus according to any one of claims 1 to 5, wherein the convection control member is located at a position including at least a certain range of the silicon single crystal in a plan view. A method for producing a silicon single crystal using the single crystal production apparatus according to any one of claims 1 to 6,
A method for producing a single crystal comprising pulling up the silicon single crystal by controlling the angle α formed by the convection control member as a predetermined angle within a range of 0 to 180 ° in the silicon melt. The angle α is set by the support means, with the convection control member positioned within a vertical distance Lb downward from the solid-liquid interface in a state substantially parallel to the bottom surface of the crucible,
Convection immediately below the solid-liquid interface that affects the quality of the single crystal grown in the silicon melt when the depth La, which is the distance between the silicon melt surface and the bottom surface of the crucible, exceeds the distance Lb. The method for producing a single crystal according to claim 7, wherein the range is controlled to be within the distance Lb. Melting the silicon raw material in the crucible to produce a silicon melt;
Disposing the convection control member at a predetermined position in the silicon melt;
The single crystal pulling step is started after sequentially performing the step of adjusting the temperature of the silicon melt so as to be the pulling start temperature, and starting the single crystal pulling step. A method for producing a single crystal. In the single crystal pulling step, a magnetic field is applied to the silicon melt by the magnetic field applying means,
The single crystal production according to claim 8 or 9, wherein the distance Lb is set as a range in which a rate of change during pulling of the magnetic field distribution applied by the magnetic field applying unit is 40% or less. Method.   The method for producing a single crystal according to claim 7, wherein the single crystal having a defect-free region is pulled up. A single crystal produced by the single crystal production apparatus according to any one of claims 1 to 6 or the single crystal production method according to any one of claims 7 to 11.

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