JP6759147B2 - Method for manufacturing silicon single crystal - Google Patents

Description

The present invention relates to a method for producing a silicon single crystal, which is pulled up while growing a silicon single crystal by the Czochralski method (hereinafter referred to as "CZ method").

In recent years, in order to reduce the ON resistivity (internal resistivity at the time of ON) of a power MOSFET, a device manufacturer has requested an N-type low resistivity silicon single crystal to which a dopant impurity is added at a high concentration. This N-type low resistivity silicon single crystal was easily dislocated in the manufacturing process and was difficult to manufacture.

Specifically, if N-type dopant impurities are added at a high concentration during the growth of a silicon single crystal, the degree of freezing point depression becomes extremely large, and a compositional supercooling phenomenon occurs. When this compositional supercooling is large, growth different from the silicon growth surface starts at the crystal growth interface, and abnormal growth called Cell growth occurs. Due to this abnormal growth, dislocation of silicon single crystal occurs. Further, when a volatile dopant impurity is added at a high concentration, not only dislocation of the silicon single crystal due to Cell growth but also dislocation related to the volatile dopant is likely to occur.
As described above, it has been difficult to obtain a desired silicon single crystal because dislocations are likely to occur due to the addition of volatile dopant impurities at a high concentration.

Patent Documents 1 and 2 show methods for suppressing dislocation of silicon single crystals.
In Patent Document 1, in the shoulder growth step of a silicon single crystal, the distance between the lower end of the gas rectifying cylinder that rectifies Ar gas and the free liquid surface of the silicon melt is set to more than 30 mm, and the silicon single crystal is described. A method of performing shoulder growth is shown. Further, it has been shown that it is preferable to make the distance dimension between the lower end of the gas rectifying cylinder and the free liquid surface of the silicon melt in the shoulder growth step larger than the distance dimension in the body growth step.

Further, Patent Document 2 describes the distance dimension between the heat shield plate that shields the radiant heat from the silicon melt and the surface of the silicon melt at the start of the period for growing the straight body portion of the silicon single crystal. The temperature is set to 30 mm, and the heat shield plate and the silicon are grown during a period in which the straight body portion is grown 200 mm away from the boundary portion between the shoulder portion and the straight body portion of the silicon single crystal in the direction opposite to the pulling direction of the silicon single crystal. It has been shown that a silicon single crystal is produced with a distance dimension of 6 to 15 mm from the surface of the melt.

Japanese Unexamined Patent Publication No. 2010-6646 International Publication No. 2010-21272

However, even in the method for producing a silicon single crystal described in Patent Documents 1 and 2, there is a technical problem that dislocation formation cannot be sufficiently reduced.
In order to solve the above technical problems, the present inventors have diligently studied the cause of dislocation of silicon single crystals. As a result, in the method for producing a silicon single crystal described in Patent Document 1, the distance dimension between the lower end of the gas rectifying cylinder that rectifies Ar gas and the free liquid surface of the silicon melt is fixed. It was found that the distance dimension (more than 30 mm) is the reason why dislocation formation cannot be sufficiently reduced.
That is, in the process of growing the neck part to the shoulder part (crown growing) of the silicon single crystal, the shape of the solid-liquid interface between the silicon single crystal and the silicon melt changes, and the shape of the neck part to the shoulder part (crown) changes. Although it varies, the method for producing a silicon single crystal described in Patent Document 1 has a fixed distance dimension (more than 30 mm), and it has been clarified that this is the cause of dislocation.

Then, the present inventor has made it possible to suppress dislocation of a silicon single crystal by changing the distance dimension between the lower end of the gas rectifying cylinder and the free liquid surface of the silicon melt in response to this change. Et al. Found.

Further, even in the method for producing a silicon single crystal described in Patent Document 2, the distance dimension between the heat shield plate and the surface of the silicon melt in the initial growth step (neck portion to shoulder portion) is a fixed distance dimension ( Since the thickness is 20 to 30 mm), it is not possible to suppress the occurrence of dislocation of the silicon single crystal as in the method for producing a silicon single crystal described in Patent Document 1.

Further, in the method for producing a silicon single crystal described in Patent Document 2, after the initial growth step (neck portion to shoulder portion), the direction in which the silicon single crystal is pulled up from the boundary portion between the shoulder portion and the straight body portion of the silicon single crystal. During the period in which the straight body portion is grown 200 mm away from the above direction, the distance between the heat shield plate and the surface of the melt is set to 6 to 15 mm to suppress dislocation of the silicon single crystal. ing.
However, under the influence of the dislocation of the silicon single crystal in the initial growth process (neck to shoulder), the dislocation in the straight body is induced, and the dislocation of the silicon single crystal cannot be suppressed. , The present inventors have found.

Based on the above findings, the present inventors consider the shape change of the solid-liquid interface between the silicon single crystal and the silicon melt and the shape change of the crown in the crown growing step of the silicon single crystal, and consider the radiation shield and the silicon fusion. It is necessary to change the distance dimension from the surface of the liquid, and in addition, by further changing the distance dimension between the radiation shield and the surface of the silicon melt in the straight body growing step, the silicon single crystal is present. I came up with the idea that dislocation can be suppressed.
Then, he diligently studied the variable range of the distance dimension between the radiation shield and the surface of the silicon melt, and completed the present invention.

The present invention has been made under the above circumstances, and the radiation shield and the surface of the silicon melt are provided within a variable range of the distance dimension between the radiation shield and the surface of the silicon melt in the silicon single crystal manufacturing process. It is an object of the present invention to provide a method for producing a silicon single crystal in which dislocations of the crown and the straight body portion are suppressed by changing the distance dimension.

The method for producing a silicon single crystal according to the present invention, which has been made to achieve the above object, is a method for producing an N-type low-resistance silicon single crystal containing arsenic, antimony, or phosphorus, in which radiation is emitted in the crown growing step. The distance dimension from the lower end of the shield to the surface of the silicon melt is within the range of 30 to 50 mm, and the distance dimension from the lower end of the radiation shield to the surface of the silicon melt in the straight body growing process is within the range of 15 to 50 mm. At the same time, from the start of crown growing to the end of crown growing in the crown growing step, the distance dimension at the start of crown growing is gradually expanded within the range of 10 mm to 20 mm, and further, the straight body portion in the straight body part growing step. It is characterized in that the distance dimension at the end of crown growing is narrowed within the range of 20 to 35 mm between the start of growing and the end of straight body growing.

According to the present invention, the distance dimension from the lower end of the radiation shield in the crown growing step to the surface of the silicon melt is within the range of 30 to 50 mm, and the surface of the silicon melt from the lower end of the radiation shield in the straight body growing step. The distance dimension to is made within the range of 15 to 50 mm.
If the distance dimension in the crown growing step is less than 30 mm, the fluctuation of the dopant concentration near the outer surface of the crown becomes large and dislocation is likely to occur, and if the distance dimension exceeds 50 mm, it is due to the inert gas for purging in the chamber. The rectification is weakened, and the drop of deposits due to the solidified dopant tends to cause dislocation of the crown, which is not preferable.
More preferably, in the crown growing step, the distance dimension from the lower end of the radiation shield to the surface of the silicon melt is within the range of 30 to 40 mm.

Further, the distance dimension from the lower end of the radiation shield to the surface of the silicon melt in the straight body portion growing step is set within the range of 15 to 50 mm.
If the distance dimension is less than 15 mm, there is a risk that the radiation shield will come into contact with the melt interface due to fluctuations in the surface position of the silicon melt, which will greatly affect the temperature gradient of the silicon single crystal, which is not preferable.
On the other hand, when the distance dimension exceeds 50 mm, the rectification by the inert gas for purging gas in the chamber is weakened, and the dislocation due to the dropping of the deposits due to the solidified dopant increases, which is not preferable.
Preferably, the distance dimension from the lower end of the radiation shield to the surface of the silicon melt in the body growing step is 15 to 40 mm.

Further, from the start of crown growth to the end of crown growth in the crown growth step, the distance dimension at the start of crown growth is gradually expanded within the range of 10 mm to 20 mm. The expanded distance dimension is within the range of 30 to 50 mm described above.
In this way, since the distance dimension at the start of crown growth is gradually expanded within the range of 10 mm to 20 mm, it is optimal considering the shape change of the solid-liquid interface between the silicon single crystal and the silicon melt and the shape change of the crown. The distance dimension can be set, and dislocation of the crown can be suppressed.
If the distance dimension is less than 10 mm and the distance dimension exceeds 20 mm, dislocation occurs in the crown, which is not preferable.
When expanding the distance dimension by 10 to 20 mm, it is preferable to continuously increase the distance dimension at a constant speed.

Further, the distance dimension at the end of crown growing is narrowed within the range of 20 to 35 mm between the start of straight body growing and the end of straight body growing in the straight body growing step. The narrowed distance dimension is within the range of 30 to 50 mm described above.
Here, when the distance dimension is less than 20 mm and the distance dimension exceeds 35 mm, dislocation occurs in the straight body portion, which is not preferable.
When narrowing the distance dimension by 20 to 35 mm, it is preferable to continuously perform the distance dimension at a constant speed.

As described above, in the present invention, the crown and the straight body portion are dislocated by changing the distance dimension between the radiation shield and the surface of the silicon melt within a predetermined range in the silicon single crystal manufacturing process. It can be suppressed.

Here, it is desirable that the internal pressure of the chamber of the silicon single crystal manufacturing apparatus in the crown growing step and the straight body growing step is set to 200 to 300 Torr.
The internal pressure of the chamber during the growth of the silicon single crystal is controlled to 200 to 300 Torr in order to minimize the evaporation of the volatile dopant from the outer surface of the silicon single crystal. When the internal pressure is less than 200 Torr, the fluctuation of the dopant concentration near the crystal surface becomes large, the curvature of the growth fringes becomes non-uniform, and dislocations are likely to occur, which is not preferable.
On the other hand, when the internal pressure of the chamber exceeds 300 Torr, the deposits caused by the volatilized dopant weaken the rectifying action due to the decrease in the gas flow velocity in the chamber, and dislocations occur due to the dropping of the deposits. It is not preferable because it occurs.

Further, in the straight body portion growing step, it is desirable to narrow the distance dimension to the distance dimension at the start of crown growing by the time the straight body portion is grown by 200 mm.
That is, by the time the straight body portion before the end of straight body portion growth is grown by 200 mm, the distance dimension at the end of crown growth is narrowed within the range of 20 to 35 mm, and the distance dimension is set as the distance dimension at the start of crown growth. Is preferable.
In the growing of the straight body portion after exceeding 200 mm, if the distance dimension is larger than the distance dimension at the start of the crown growing, the pulling speed of the silicon single crystal decreases, and the silicon single crystal of good quality is grown. It is not preferable because crystals cannot be obtained.

Further, in the crown growing step, the rotation speed of the rutsubo is set to 1 to 3 rpm, the rotation speed of the seed crystal at the start of crown growing is set to 25 to 30 rpm in the direction opposite to the rotation direction of the rutsubo, and then the seed is set by the end of crown growing. It is desirable to reduce the rotation speed of the crystal to 10 to 14 rpm, to set the rotation speed of the rutsubo to 1 to 3 rpm, and to set the rotation speed of the seed crystal to 10 to 14 rpm in the straight body growing step.
In this way, the rotation speed of the seed crystal is gradually lowered from 25 to 30 rpm as the seed crystal grows, and by the time the crown growth is completed, the rotation speed is lowered to 10 to 14 rpm. Non-uniformity can be avoided and dislocation can be suppressed.
Further, by setting the rotation speed of the crucible to 1 to 3 rpm in the straight body portion growing step, the concentration distribution in the silicon single crystal plane can be made more uniform, and dislocation formation can be suppressed.

Further, it is desirable that the diameter of the silicon single crystal is 6 inches or more and 8 inches or less.

According to the present invention, in the silicon single crystal manufacturing process, by changing the distance dimension between the radiation shield and the surface of the silicon melt within a predetermined range, dislocation of the crown and the straight body portion is suppressed. A method for producing a crystal can be obtained.

FIG. 1 is a schematic configuration diagram of a silicon single crystal manufacturing apparatus used in the present invention. FIG. 2 is an enlarged view of a main part of the silicon single crystal manufacturing apparatus shown in FIG. FIG. 3 is a diagram showing the dislocation-free rate in Examples and Comparative Examples.

First, the silicon single crystal manufacturing apparatus used in the present invention will be described with reference to FIGS. 1 and 2.
The manufacturing apparatus 1 has a cylindrical chamber (chamber) 2, a crucible 3 provided in the crucible 2, and a carbon heater 4 for melting the raw material silicon loaded in the crucible 3. The crucible 3 is composed of a quartz glass crucible 3a on the inside and a graphite crucible 3b on the outside.

Further, in the chamber 2, a heat insulating cylinder 5 is provided around the outer periphery of the carbon heater 4. The heat insulating cylinder 5 is formed in a cylindrical shape, and an inwardly extending heat insulating plate 6 is provided at the upper end thereof. Further, a radiant shield 7 is provided on the growing (pulling) silicon single crystal C so as not to give extra radiant heat from the carbon heater 4 or the like.

In the radiation shield 7, openings 7a and 7b are formed in the upper part and the lower part so as to surround the periphery of the silicon single crystal C above and in the vicinity of the crucible 3, and the area of the opening increases from the upper part to the lower part. The tapered surface 7c is formed so as to gradually become smaller.
By providing the radiation shield 7, the purging inert gas (Ar gas) G supplied into the crucible 3 from above passes through the gap between the radiation shield 7 and the surface of the silicon melt M and passes through the crucible 3. It flows out and is finally discharged to the outside of the chamber 2 (outside the chamber).

Although not shown, a pulling mechanism for pulling up the silicon single crystal C is provided above the chamber 2. This pulling mechanism is composed of a winding mechanism driven by a motor and a pulling wire 8 wound by the winding mechanism.
Then, a seed crystal P is attached to the tip of the wire 8 so as to pull up the silicon single crystal C while growing it.

Although not shown, the silicon single crystal manufacturing apparatus 1 includes a motor for rotating the crucible 3, an elevating device for controlling the height of the crucible 3, the motor, and a control device for controlling the elevating device. It is configured to grow the silicon single crystal C while rotating the 3 and increasing the height of the crucible 3.

Further, although not shown, a gas supply port is provided in the upper part of the chamber 2 so that the purging inert gas (Ar gas) is supplied into the chamber 2. Further, a plurality of exhaust ports (not shown) are provided on the bottom surface of the chamber 2, and an exhaust pump (not shown) as an exhaust means is connected to the exhaust ports.
Therefore, the purging inert gas (Ar gas) G supplied into the chamber 2 from the gas supply port flows out of the crucible by the exhaust pump through the gap between the radiation shield 7 and the surface of the silicon melt M. Finally, the gas is discharged to the outside of the chamber 2 (outside the chamber).

Further, the radiation shield 7 will be described in detail with reference to FIG.
The radiation shield 7 is configured so that the distance dimension (interval) X between the surface M1 of the silicon melt M and the lower end 7d of the radiation shield 7 can be changed by an elevating device (not shown). That is, in the process of manufacturing a silicon single crystal, the radiation shield 7 can be raised and lowered so that the distance dimension (interval) X between the surface M1 of the silicon melt M and the lower end 7d of the radiation shield can be set to the optimum value.

In order to change the distance dimension (interval) X between the surface M1 of the silicon melt M and the lower end 7d of the radiation shield 7, it is conceivable to raise or lower the radiation shield 7 itself or to raise or lower the crucible 3.
When the crucible 3 is raised and lowered, the surface M1 of the silicon melt M may fluctuate due to the raising and lowering, the surface position of the surface M1 of the silicon melt M may fluctuate, and the diameter of the silicon single crystal may fluctuate.
On the other hand, when the radiation shield 7 is raised and lowered, the surface M1 of the silicon melt M does not shake due to the raising and lowering, so that the diameter of the silicon single crystal does not fluctuate, which is preferable.
Further, the radiation shield 7 can be easily moved up and down by winding the wire attached to the radiation shield 7 around the drum by a motor and pulling out the wire from the drum. Moreover, the radiant shield 7 can be raised and lowered smoothly and continuously.

Therefore, in the embodiment of the present invention, the distance dimension (interval) X between the surface M1 of the silicon melt M and the lower end 7d of the radiation shield 7 is changed by a more preferable method of moving the radiation shield 7. As a matter of course, the crucible 3 may be raised and lowered.

Next, the manufacturing method according to the present invention will be described.
The production method according to the present invention uses highly volatile arsenic, antimony, or phosphorus as a dopant when producing (growing) an N-type silicon single crystal having a wafer resistance value of 0.01 Ω · cm or less. It is a method for producing a single crystal, and is intended to reduce dislocations of a silicon single crystal, which is the largest cause of a decrease in yield.
In the manufacturing method described below, a case where the radiation shield 7 is raised and lowered will be described, but the present invention is not particularly limited to this, and the crucible 3 may be raised and lowered.

The outline of the method for producing a silicon single crystal will be described with reference to FIG. 1. First, the crucible 3 is filled with a polycrystalline silicon raw material, and the crucible 3 is slowly rotated and heated by a carbon heater 4, and the polycrystalline silicon raw material is heated. To melt.
Next, after the melting of the polycrystalline silicon raw material is completed, the surface temperature of the silicon melt is adjusted to the melting point of 1420 ° C., and a highly volatile arsenic, antimony, or phosphorus dopant is added. After that, the seed crystal P suspended by the wire 8 is immersed in the silicon melt M and blended to start growing the silicon single crystal, and the silicon ingot (silicon single crystal) is pulled up.
The silicon ingot (silicon single crystal) is pulled up (manufactured) through a neck growing step, a crown growing step, a straight body growing step, and a tail growing step.

The distance dimension X from the lower end 7d of the radiation shield 7 to the surface M1 of the silicon melt M in the crown growing step is regulated within the range of 30 to 50 mm. That is, the movement of the radiation shield 7 is restricted within the range of 30 to 50 mm in the distance dimension of the silicon melt M to the surface M1.

The reason why the distance dimension X (gap) is set to 30 mm or more in this way is that when the distance dimension X (gap) is 30 mm or less, the fluctuation of the dopant concentration near the outer surface of the crown becomes large and dislocations are likely to occur. ..
On the other hand, the reason why the distance dimension X (gap) is 50 mm or less is that when the distance dimension X is 50 mm or more, the rectification by the inert gas for purging (Ar gas) is weakened, and the volatilized dopant adheres to the inside of the chamber. This is because the solidified deposits may fall onto the crown, which may cause dislocation of the crown.
Considering that the shape of the crown is small at the start of growing the crown, it is preferable that the distance dimension X from the lower end 7d of the radiation shield 7 to the surface M1 of the silicon melt M is 30 to 40 mm.

Then, from the start of crown growth to the end of crown growth in the crown growth step, the distance dimension is gradually increased within the range of 10 mm to 20 mm from the start of crown growth according to the solid-liquid interface shape change and crown shape change accompanying the crown growth. Increase (rise) to.
When the distance dimension X at the start of growing the crown is set to 30 to 40 mm, even when the distance dimension X is increased (raised) within the range of 10 mm to 20 mm, the radiation shield 7 can be used. The distance dimension X of the silicon melt M to the surface M1 can be kept within the range of 30 to 50 mm.
When the distance dimension is gradually increased (raised) within the range of 10 mm to 20 mm, it is preferable to continuously increase (rise) the distance dimension at a constant speed.

In this way, in order to gradually increase (raise) the distance dimension within the range of 10 mm to 20 mm from the distance dimension at the start of crown growth, the shape of the solid-liquid interface between the silicon single crystal and the silicon melt changes. The optimum distance dimension can be set in response to the change in the shape of the crown, and the dislocation of the crown can be suppressed.
If the distance dimension is less than 10 mm, it is not possible to cope with the change in the shape of the crown, the dopant on the crown surface fluctuates, and dislocation formation cannot be suppressed, which is not preferable.
Further, when the distance dimension exceeds 20 mm, a gap larger than the shape change of the crown is formed, so that the deposit may fall on the crown, which may cause dislocation of the crown, which is not preferable. ..

Subsequently, in the straight body portion growing step following the crown growing step, the distance dimension X from the lower end 7d of the radiation shield 7 to the surface M1 of the silicon melt M is regulated within the range of 15 to 50 mm.
That is, the movement of the radiation shield 7 is restricted within the range of 15 to 50 mm in the distance dimension X from the surface M1 of the silicon melt M to the surface M1.
In particular, in the process of growing the straight body portion, the distance dimension X is preferably within the range of 15 to 40 mm, and the movement of the radiation shield 7 is more preferably limited to the range of 15 to 40 mm.

The distance dimension X from the lower end 7d of the radiation shield 7 to the surface M1 of the silicon melt M is limited to 15 mm or more because a Gap error occurs due to the tolerance of the crucible wall thickness and the like, and the silicon single crystal. This is because a Gap error or the like occurs due to a change in the melt surface due to a deviation in thickness, which increases the influence on the temperature gradient. Further, the distance dimension X is limited to 15 mm or more in order to ensure safety because the radiation shield is too close to the melt interface.
When the chamber internal pressure is 200 to 300 Torr, Gap 15 mm is an appropriate lower limit value.

Further, when the distance dimension X exceeds 50 mm, rectification by gas in the chamber is weakened, and dislocations due to dropping of deposits increase, which is not preferable.
Preferably, in the straight body growing step, the distance dimension X is preferably 15 to 40 mm.

Further, in this straight body part growing step, dislocations are likely to occur due to compositional supercooling, so that the distance dimension from the lower end of the radiation shield to the surface of the silicon melt is narrowed and the temperature gradient of crystal growing is increased.
Therefore, in the straight body portion growing step, the distance dimension X expanded in the crown growing step is gradually narrowed from the start of growing the straight body portion to the end of the straight body.

Specifically, the distance dimension X expanded in the crown growing step is narrowed by 20 to 35 mm from the distance dimension at the end of the crown growing step by lowering the radiation shield 7. The distance dimension X of the lowered radiation shield 7 is within the range of 15 to 50 mm described above.
Here, when the distance dimension is less than 20 mm, the temperature gradient of crystal growth cannot be sufficiently increased, so that dislocations are likely to occur due to compositional supercooling, which is not preferable.
Further, when the distance dimension exceeds 35 mm, the temperature gradient of crystal growth is small and dislocations are likely to occur due to compositional supercooling, which is not preferable.
When the distance dimension is gradually narrowed (descended) within the range of 20 mm to 35 mm, it is preferable to continuously narrow the distance dimension at a constant speed.

Further, based on the distance dimension X at the start of growing the crown, the distance dimension X is expanded in the crown growing, and the expanded distance dimension X is narrowed in the straight body portion growing step.
The method of narrowing the distance dimension X in the straight body part growing process is to narrow the distance dimension X from the start of straight body part growing to the end of straight body part growing, preferably from the start of straight body part growing to 200 mm of straight body part growing. Is preferable.

In this way, after the straight body has been grown by 200 mm, if it is larger than the distance dimension X at the start of growing the crown, the silicon single crystal may be deformed, and it is difficult to pull it up at the required pulling speed. Therefore, it becomes impossible to obtain a silicon single crystal of good quality.
On the other hand, when the growth length of the straight body portion is less than 200 mm, latent heat due to silicon single crystal formation is relatively easy to escape even if the distance dimension X is larger than the distance dimension X at the start of growing the crown, which is necessary. The pulling speed can be obtained, and a silicon single crystal of good quality can be obtained.

As described above, in the present invention, the crown and the straight body portion are dislocated by changing the distance dimension between the radiation shield and the surface of the silicon melt within a predetermined range in the silicon single crystal manufacturing process. Can be suppressed.

Next, the manufacturing conditions in the manufacturing method according to the present invention will be described.
The internal pressure of the chamber in the silicon single crystal manufacturing step (crown growing step, straight body growing step) is controlled to 200 to 300 Torr. The internal pressure of the chamber is set to 200 to 300 Torr in order to minimize the evaporation of the volatile dopant from the outer surface of the silicon single crystal.

Further, when the internal pressure of the chamber is less than 200 Torr, the fluctuation of the dopant concentration near the silicon crystal surface becomes large, the curvature of the growth fringes becomes non-uniform, and dislocations are likely to occur. Therefore, the internal pressure of the chamber is preferably 200 Torr or more.
On the other hand, when the internal pressure of the chamber exceeds 300 Torr, the deposits caused by the volatilized dopant weaken the rectifying action due to the decrease in the flow velocity of the purging inert gas, and dislocations occur due to the dropping of the deposits. Occurs. Therefore, the internal pressure of the chamber is preferably 300 Torr or less.

Further, when the silicon single crystal C is pulled up while growing by the CZ method, the seed crystal P and the crucible 3 are rotated in opposite directions at a predetermined number of rotations.
Specifically, in the crown growing step, the rut pot rotation speed is set to 1 to 3 rpm, the crystal rotation speed at the start of crown growing is set to 25 to 30 rpm, and then the rotation speed of the seed crystal is reduced to 10 to 14 rpm by the end of crown growing. .. Then, in the straight body portion growing step, the rotation speed of the crucible is set to 1 to 3 rpm, the rotation speed of the seed crystal is set to 10 to 14 rpm, and the silicon single crystal is pulled up.

When the number of rotations of the seed crystal P in the crown growing step is high, the growth fringes tend to be non-uniform. The non-uniformity of the growth fringes is the same as the rough interface when viewed microscopically, and is easily dislocated.
Therefore, in order to avoid non-uniformity of the growth fringes, the crystal rotation speed is adjusted to 25 to 30 rpm at an early stage of crown growth, the rotation speed of the seed crystal P is gradually lowered as the crown grows, and when the crown growth is completed. It is desirable to reduce the speed to 10 to 14 rpm.
Further, also in the straight body portion growing step, in order to avoid the non-uniformity of the growth fringes, the silicon single crystal C is pulled up while the rotation speed of the seed crystal P is maintained at 10 to 14 rpm.

Further, the rotation speed of the crucible 3 in the crown growing step and the straight body growing step is preferably 1 to 3 rpm in order to make the concentration distribution in the silicon single crystal plane as uniform as possible.

An example and a comparative example of the method for producing a silicon single crystal according to the present invention are shown in FIG.
In the production of this silicon single crystal, a Φ24 inch quartz crucible is charged with 150 kg of polycrystalline silicon raw material, doped with high concentration phosphorus, and a silicon single crystal is produced aiming at 0.9 mΩ · cm at a solidification rate of 80%. Raised (manufactured).
As a condition for growing a silicon single crystal, the internal pressure of the chamber of the manufacturing apparatus is kept constant at 250 Torr, the rotation speed of the seed crystal during crown growing is set to 27 rpm at the start of crown growing, and the final speed is gradually lowered during crown growing. It was lowered to 12 rpm. The rotation speed of the seed crystal was maintained at 10 to 14 rpm even in the straight body growing step. The rotation speed of the crucible 3 in the crown growing step and the straight body growing step was set to 1 to 3 rpm.

Then, the distance dimension X from the lower end 7d of the radiation shield 7 to the surface M1 of the silicon melt M was variously changed as shown in Table 1, and the dislocation-free rate of the silicon single crystal was measured. The results are shown in Table 1 and FIG.
The dislocation-free rate of the silicon single crystal was measured by visually determining whether or not the silicon single crystal had dislocations by monitoring in the furnace during the growth of the silicon single crystal.

尚、表１中の○は無転位率８０％以上を示す。△は無転位率５０〜８０％、×は無転位率５０％未満であることを示している。したがって、最適な距離寸法条件は、クラウンも直胴部も○で示す範囲である。

◯ in Table 1 indicates a dislocation-free rate of 80% or more. Δ indicates a dislocation-free rate of 50 to 80%, and × indicates a dislocation-free rate of less than 50%. Therefore, the optimum distance dimension condition is the range indicated by ◯ for both the crown and the straight body.

In FIG. 3, the thick line of the arrow is the case of the crown, and the change in the distance dimension from the start to the end of the growth of the crown is shown. Similarly, the thin line of the arrow indicates the change in the distance dimension in the straight body. Specifically, the view of FIG. 3 will be described by taking Example 1 (reference numeral 1) as an example.
In the first embodiment, as shown in FIG. 3, the distance dimension X from the lower end of the radiation shield to the surface of the silicon melt is set to 30 mm at the start of growing the crown. After that, the distance dimension is gradually expanded, and at the end of crown growing, the distance dimension is expanded by 10 mm to 40 mm. Then, the distance dimension is gradually narrowed from 40 mm of the distance dimension X at the start of growing the straight body portion, and the distance dimension X is narrowed by 25 mm to 15 mm by the time the straight body portion is raised by 200 mm.
◯ in FIG. 3 indicates a dislocation-free rate of 80% or more. Δ indicates a dislocation-free rate of 50 to 80%, and × indicates a dislocation-free rate of less than 50%. Therefore, the optimum distance dimension condition is the range indicated by ◯ for both the crown and the straight body.

As is clear from Examples 1 to 5 of FIG. 3, in Examples 1 to 5, a favorable result of 80% of no dislocation was obtained.
In the case of Comparative Example 1, the crown had no dislocation, but since the growth was started in a state where the distance dimension X was a little wide as 53 mm in the straight body part growing step, the crystal was easily deformed and the straight body part was dislocated. Occurred.
In the case of Comparative Example 2, the crown had no dislocation, but since the distance dimension X was narrowed to 10 mm in the straight body part growing step, the flow velocity of the inert gas (Ar gas) for purging became faster, and the silicon melted. Fluctuations occurred on the surface of the liquid, and the dislocation-free rate of the straight body decreased (dislocations increased).

In the case of Comparative Example 3, the distance dimension X in the crown growing step was narrow, and the dislocation-free rate of the crown was low (the dislocation was high). Further, since the straight body portion was grown in a state where the dislocation-free rate of the crown was low, the dislocation-free rate of the straight body portion was as low as less than 50%.
In the case of Comparative Example 4, since the distance dimension at the crown was constant at 25 mm, the dislocation-free rate of the crown was as low as 50% to 80% (the dislocation was high). Further, since the straight body portion was grown in this state, the dislocation-free rate of the straight body portion was as low as less than 50%.

In the case of Comparative Example 5, since the distance dimension X at the crown was expanded beyond 50 mm, the dislocation-free rate of the crown was as low as 50% to 80% (the dislocation was high). Further, since the straight body portion was grown in this state, the dislocation-free rate of the straight body portion was as low as less than 50%.
In the case of Comparative Example 6, the distance dimension X of the crown growing step and the straight body growing step was large, and the dislocation-free rate of the straight body was as low as less than 50%.

As described above, the distance dimension from the lower end of the radiation shield in the crown growing process to the surface of the silicon melt is within the range of 30 to 50 mm, and from the lower end of the radiation shield in the straight body growing process to the surface of the silicon melt. The distance dimension of is set within the range of 15 to 50 mm, and the distance dimension at the start of crown growing is gradually expanded within the range of 10 mm to 20 mm from the start of crown growing to the end of crown growing in the crown growing step. By narrowing the distance dimension at the end of crown growing from the start of straight body growing to the end of straight body growing in the straight body growing step within the range of 20 to 35 mm, the dislocation-free rate of the silicon single crystal can be reduced. It can be increased to 80% or more.

1 Silicon single crystal manufacturing equipment 2 Chamber (fire pot)
3 Crucible 4 Carbon heater 7 Radiation shield 7d Lower end of radiation shield C Silicon single crystal G Inert gas for purging M Silicon melt M1 Silicon melt surface P seed crystal X Between the lower end of the radiation shield and the surface of the silicon melt Distance dimension of

Claims (5)

In the method for producing an N-type low-resistance silicon single crystal containing arsenic, antimony, or phosphorus,
The distance dimension from the lower end of the radiation shield in the crown growing process to the surface of the silicon melt is within the range of 30 to 50 mm, and the distance dimension from the lower end of the radiation shield in the straight body growing process to the surface of the silicon melt is 15. While making it within the range of ~ 50 mm
From the start of crown growth to the end of crown growth in the crown growth step, the distance dimension at the start of crown growth is gradually expanded within the range of 10 mm to 20 mm, and further, from the start of straight body growth in the straight body growth step. A method for producing a silicon single crystal, which comprises narrowing the distance dimension at the end of crown growth within a range of 20 to 35 mm until the end of straight body growth. The method for producing a silicon single crystal according to claim 1, wherein the chamber internal pressure of the silicon single crystal manufacturing apparatus in the crown growing step and the straight body portion growing step is set to 200 to 300 Torr. In the straight body growing step,
The method for producing a silicon single crystal according to claim 1 or 2, wherein the distance dimension is narrowed to the distance dimension at the start of crown growth by the time the straight body portion is grown by 200 mm. In the crown growing step, the rotation speed of the rutsubo is set to 1 to 3 rpm, the rotation speed of the seed crystal at the start of crown growing is set to 25 to 30 rpm in the direction opposite to the rotation direction of the rutsubo, and then the rotation of the seed crystal is set by the end of crown growing. Reduce the number to 10-14 rpm,
The method for producing a silicon single crystal according to any one of claims 1 to 3, wherein the crucible rotation speed is 1 to 3 rpm and the seed crystal rotation speed is 10 to 14 rpm in the straight body portion growing step. .. The method for producing a silicon single crystal according to any one of claims 1 to 4, wherein the diameter of the silicon single crystal is 6 inches or more and 8 inches or less.

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