JP6354643B2 - Method for producing silicon single crystal - Google Patents

Description

  The present invention relates to a method for producing a silicon single crystal by the Czochralski method (CZ method).

  As a method for manufacturing a silicon single crystal used for manufacturing a semiconductor element, a CZ method is widely practiced in which a silicon single crystal is grown and grown from a raw material melt contained in a quartz crucible in a main chamber.

  In the CZ method, a seed crystal is immersed in a raw material melt in a quartz crucible under an inert gas atmosphere, and a predetermined silicon single crystal is grown by pulling up while rotating the quartz crucible and the seed crystal.

  It is known that a silicon single crystal manufactured by the CZ method has crystal defects (Grown-in defects) formed during the growth of the silicon single crystal. In general, silicon single crystals include intrinsic vacancy (vacancy) and interstitial Si (interstitial Si). The saturation concentration of these intrinsic point defects is a function of temperature, and a supersaturation state of point defects occurs with a rapid decrease in temperature during crystal growth. The supersaturated point defect proceeds in the direction of mitigating the supersaturated state by pair annihilation, outward diffusion and slope diffusion.

  It is known that when the crystal growth rate (that is, the crystal pulling rate) is high, the vacancies are easily oversaturated, and conversely, when the pulling rate is low, the interstitial Si is easily oversaturated. If the concentration of the supersaturated state becomes a certain level or more, they aggregate and form crystal defects (Grown-in defects) during crystal growth.

  That is, it is known that when the crystal pulling rate is high, the vacancies are dominant (V region), and when the crystal pulling rate is low, the interstitial Si is dominant (I region).

  As a grown-in defect in the V region, an OSF nucleus and a void defect are known. When the sample cut from the crystal is heat-treated in a wet oxygen atmosphere at a high temperature of about 1100 ° C., interstitial Si is injected from the surface, and stacking faults (SF) grow around the OSF nucleus. This is a defect observed as a stacking fault when selective etching is performed while rocking in the selective etching solution. This is called an oxidation induced stacking fault (OSF) because a stacking fault grows by the oxidation treatment.

  When the pulling rate is decreased in the V region, OSF is generated in a ring shape from the periphery of the crystal (OSF region). The OSF region shrinks toward the crystal center as the pulling rate decreases, and finally the OSF disappears at the crystal center.

  In addition, in the case of a boron-doped P-type crystal, the generation of the OSF region also depends on the resistivity. When a single crystal is grown at a normal pulling rate, the OSF region is generated around the crystal at about 0.02 Ωcm. The OSF region shrinks toward the crystal center as the resistivity decreases, and when the resistivity is about 0.009 Ωcm or less, the OSF region disappears at the crystal center.

  If a silicon wafer in which an OSF region is generated is used, defects may be formed on the surface layer of the epitaxial layer. In addition, the oxygen precipitation characteristics are greatly different between the inside and outside of the OSF region, and there is a possibility that an unforeseeable malfunction may occur depending on the temperature sequence in the subsequent device process. Therefore, conventionally, in order to obtain a silicon wafer in which no OSF region is generated, a method of lowering the pulling speed (low speed pulling) has been performed.

JP 2007-001847 A JP 2000-219598 A

  However, since the pulling speed is slow, the pulling at a low speed is costly, such as a reduction in the production capacity of the machine and an increase in material costs due to an increase in the amount of electric power and inert gas flowing into the furnace.

  Furthermore, as a result of investigations by the present inventors, it has been found that when the pulling is performed at a low speed, the yield of the silicon single crystal itself is lowered as follows.

  Dislocation may occur during the process of pulling up the silicon single crystal. When dislocation occurs in a short part of the straight body, the pulling is temporarily stopped, the silicon single crystal being pulled is melted again, and the production of the silicon single crystal is resumed from seeding again. In the case of dislocation, the pulling is finished as it is.

  The quartz crucible reacts with the raw material melt to form a so-called brown ring. As time elapses, the diameter of the brown ring increases and overlaps with each other so that the brown ring becomes invisible. At that time, a rough surface with poor flatness occurs on the inner surface of the quartz crucible. There, crystallized quartz is also scattered.

  Fine quartz chips are generated from the rough surface of the inner surface of the quartz crucible generated in this way and taken into the raw material melt. Further, when the quartz scrap reaches the silicon single crystal being pulled, it causes dislocation. In particular, crystallized quartz is difficult to dissolve in the raw material melt, so that it can easily reach the pulled silicon single crystal.

  The crystal pulling speed is affected by the temperature gradient near the solid-liquid interface. For example, in an environment with a large temperature gradient, the pulling rate can be increased. In the crystal growth direction, the top side of the crystal was fast and the bottom side was slow. The reason for slowing down on the bottom side is to raise the graphite crucible on the bottom side in order to keep the position of the liquid surface of the raw material melt constant, and radiation from the graphite crucible wall has the effect of hindering heat dissipation of the crystal Because. For this reason, it has become common knowledge to set the pulling speed to continuously decrease from the top side to the bottom side.

  Conventionally, the slow pulling speed that causes the OSF region to shrink and disappear by the crystal center is only about half the normal pulling speed. In such a case, it took twice as long to produce a silicon single crystal as compared to the case of a normal pulling rate. Further, even at such a low pulling speed, the pulling speed is set so as to continuously decrease from the top side to the bottom side in accordance with the conventional example as described above. For this reason, the pulling speed has become increasingly slower.

  Such low speed pulling is forced to operate for a long time, and if remelting occurs, the DF conversion rate (probability of obtaining a single crystal without dislocation over the entire crystal length) is greatly reduced. As a result, the yield of the single crystal itself decreased, resulting in a large cost increase.

  The present invention has been made in view of the above-described problems, and in manufacturing a silicon single crystal, it is possible to manufacture a silicon single crystal that suppresses generation of dislocations while suppressing generation of an OSF region with high yield. An object of the present invention is to provide a method for producing a silicon single crystal.

In order to achieve the above object, according to the present invention, there is provided a method for producing a silicon single crystal by the Czochralski method,
When the silicon single crystal to be pulled up is a boron-doped P-type silicon single crystal having a resistivity of 0.009 Ωcm to 0.02 Ωcm,
When the OSF region disappears at the crystal center, the ratio V _OSF / G of the OSF region disappearance pulling rate V _OSF (mm / min) and the temperature gradient G (K / mm) of the crystal center is obtained,
The silicon single crystal is pulled up while controlling the pulling rate so as to be slower than the OSF region disappearance pulling rate V _OSF calculated from the obtained ratio V _OSF / G in a range of 5% to 20%. A method for producing a silicon single crystal is provided.

  In this way, when the silicon single crystal to be pulled is a boron-doped P-type and the silicon single crystal has a low resistivity of 0.009 Ωcm or more and 0.02 Ωcm or less, the generation of the OSF region is suppressed and the presence is suppressed. A silicon single crystal in which the occurrence of dislocation is suppressed can be produced.

At this time, the pulling speed is controlled so as to be slower than the OSF region extinction pulling speed V _OSF , at least from 10% to 80% of the length of the straight body portion of the silicon single crystal to be pulled from the cone side. It is preferable to carry out in the region.

  In this way, it is possible to sufficiently control the diameter of the straight body portion of the silicon single crystal, and it is possible to obtain a crystal in which the OSF region disappears at the center substantially over the entire crystal.

Further, when the pulling rate is controlled so as to be slower than the OSF region disappearing pulling rate V _OSF , the pulling rate is controlled to increase continuously or intermittently as the pulling of the silicon single crystal proceeds. It is preferable to do.

  In this way, it is possible to more reliably suppress the occurrence of dislocations while suppressing the generation of the OSF region.

At this time, the ratio V _OSF / G can be calculated by the following formula (1).
V _OSF /G=1138.9×ρ ² −45.60 × ρ + 0.643 (1)
(Where, ρ: resistivity of single crystal (Ωcm), 0.009 ≦ ρ ≦ 0.02)

When the silicon single crystal to be manufactured is boron-doped P-type and the resistivity is 0.009 Ωcm or more and 0.02 Ωcm or less, the ratio V _OSF / G can be easily calculated by the above equation.

  In the method for producing a silicon single crystal of the present invention, when the silicon single crystal to be pulled is a boron-doped P type and the resistivity is 0.009 Ωcm or more and a low resistance silicon single crystal of 0.02 Ωcm or less, A silicon single crystal in which generation of dislocations is suppressed while generation is suppressed can be produced.

It is the schematic which showed an example of the silicon single crystal manufacturing apparatus which can be used by this invention. It is the graph which showed the resistivity profile of the axial direction of the silicon single crystal which manufactures calculated in the Example and the comparative example. 10 is a graph showing the relationship between the solidification rate and V / G in Comparative Example 3. It is the graph which showed the relationship between the solidification rate in Example and Comparative Example 1, and V / G.

  Hereinafter, the present invention will be described in detail as an example of an embodiment with reference to the drawings, but the present invention is not limited thereto.

  As mentioned above, low speed pulling was slow because the pulling speed was slow, and the cost of materials increased due to a decrease in the production capacity of the machine and an increase in the amount of power and inert gas flowing through the furnace. . Furthermore, as a result of investigations by the present inventors, it has been found that when the pulling is performed at a low speed, the yield of the silicon single crystal itself is lowered.

  Therefore, the present inventors have made a detailed study on the pulling speed in order to improve the dislocation-free rate. The silicon single crystal doped with boron focused on the phenomenon that the pulling speed at which the OSF region disappears increases as the resistivity decreases. Boron has a smaller covalent bond radius than silicon. Therefore, when its concentration is increased, the lattice becomes smaller and distortion occurs. In order to relax the strain, silicon interstitial atoms are likely to be generated.

  Regarding this phenomenon, for example, paragraph [0035] of Patent Document 1 describes that in the manufacture of a P-type low resistivity crystal, the OSF ring diameter contracts as the resistivity decreases. Further, FIG. 2 of Patent Document 2 discloses the relationship between the resistivity that becomes the entire V region and V / G for the P-type low resistivity crystal. However, the relationship between the resistivity and the pulling rate under conditions where the OSF region disappears has not been clearly disclosed.

  According to the investigation by the present inventors, the OSF region disappeared in all crystals having a resistivity of 0.009 Ωcm or less, and the following formula (1) was found as a condition for the OSF to disappear. And the best form for implementing these was scrutinized and the present invention was completed.

  The silicon single crystal manufacturing apparatus that can be used in the method for manufacturing a silicon single crystal of the present invention is not particularly limited, and for example, a silicon single crystal manufacturing apparatus as shown in FIG. 1 can be used.

  The quartz crucible 5 in the graphite crucible 6 disposed in the main chamber 1 is filled with the raw material melt 4, and the silicon single crystal 3 is pulled from the raw material melt 4 into the pulling chamber 2. A heater 7 for heating the raw material melt 4 is installed on the outer periphery of the graphite crucible 6, and a graphite shield 9 and a heat insulating member 8 are installed on the outer periphery of the heater 7 to insulate the heat from the heater 7. . An inert gas such as argon that fills the silicon single crystal manufacturing apparatus is introduced from the gas inlet 10, and the gas flows along the gas rectifying cylinder 13 and is exhausted from the gas outlet 11. Further, a heat shield member 12 that blocks radiation from the heater 7 and the raw material melt 4 is installed on the raw material melt 4 side of the gas flow straightening cylinder 13. The main chamber 1 is provided with a radiation thermometer 14 and a window 15 for observing the pulling state.

  Next, an example of the method for producing a silicon single crystal of the present invention will be described in detail. Below, the case where the silicon single crystal manufacturing apparatus of FIG. 1 is used is demonstrated.

(Raw material input process)
First, a silicon polycrystalline raw material as a raw material is put into a quartz crucible 5 accommodated in a silicon single crystal manufacturing apparatus. At this time, a boron dopant is also mixed so that the silicon single crystal 3 to be pulled is doped with boron. At that time, a silicon single crystal 3 of P-type boron doped and having a resistivity of 0.009 Ωcm or more and 0.02 Ωcm or less is obtained.

(Seeding process)
After these raw materials are melted by the heater 7 to obtain the raw material melt 4, a silicon single crystal piece is used as a seed crystal, which is brought into contact with the raw material melt 4 and then slowly pulled up while being rotated. Then, the silicon single crystal 3 is grown. At this time, after bringing the seed crystal into contact with the raw material melt 4, in order to eliminate the dislocation caused by propagation from the slip dislocation generated in the seed crystal at a high density by thermal shock, a tapered narrowing portion for narrowing the seed crystal; Subsequently, so-called seed drawing is performed (dash necking method) in which a drawn portion whose diameter is once narrowed to about 3 mm is formed.

  Alternatively, by applying a dislocation-free seeding method in which a seed crystal with a sharp tip is prepared, gently touching the raw material melt 4 and dipped to a predetermined diameter without pulling, and then pulling up. The single crystal 3 can also be pulled up.

(Cone process and straight body growth process)
Thereafter, the single crystal is thickened to a desired diameter to form a cone portion (cone step), then the straight body portion is grown, and the silicon single crystal is pulled up (straight body portion growth step). In the present invention, the silicon single crystal is pulled and manufactured while controlling the pulling speed as follows.

First, a ratio V _OSF / G between the OSF region disappearance pulling rate V _OSF (mm / min) and the temperature gradient G (K / mm) of the crystal center when the OSF region disappears at the crystal center is obtained. The calculation of V _OSF / G is based on two relationships: the pulling rate when the pulling rate is gradually decreased in the manufacture of boron-doped P-type crystals, the positional relationship of the OSF region, and the resistivity of the mass-produced product and the positional relationship of the OSF region. Can be sought.

At this time, the ratio V _OSF / G can be calculated by, for example, the following formula (1).
V _OSF /G=1138.9×ρ ² −45.60 × ρ + 0.643 (1)
(Where, ρ: resistivity of single crystal (Ωcm), 0.009 ≦ ρ ≦ 0.02)

Thus, when the silicon single crystal to be manufactured is boron-doped P-type and the resistivity is 0.009 Ωcm or more and 0.02 Ωcm or less, the ratio V _OSF / G can be easily calculated by the above equation (1). .

  Specifically, the temperature gradient G (K / mm) at the crystal center is the axial distance from the melting point 1412 ° C. to 1400 ° C. of the silicon, and the temperature difference 12 ° C. (1412 ° C.-1400 ° C.) is divided. It can be a numerical value. The temperature gradient G (K / mm) at the center of the crystal focusing on the temperature gradient at the center of the crystal is that when the crystal is pulled, the pulled crystal cools faster toward the periphery, and the OSF moves from the periphery toward the center. This is to shrink.

  It is known that the temperature gradient G at the crystal center is determined by the in-furnace structure (hot zone) in the silicon single crystal manufacturing apparatus. Therefore, for example, simulation by comprehensive heat transfer analysis software FEMAG (F. Dupret, P. Nicodeme, Y. Ryckmans, P. Waterers, and MJ Crochet, Int. J. Heat Mass Transfer, 33, 1849 (1990)). Can be used to determine the temperature gradient G of the crystal center.

From the ratio V _OSF / G thus determined, the OSF region disappearance pulling speed V _OSF is calculated. In the present invention, the silicon single crystal is pulled while controlling the pulling speed so as to be slower than the OSF region disappearance pulling speed V _{OSF in} the range of 5% to 20%.

In this way, the pulling-up is performed at a speed that is at least 5% slower than the OSF region disappearance pulling speed V _OSF, so that the pulling speed is sufficient to shrink the OSF area and disappear. Furthermore, since the upper limit for slowing the pulling speed is in the range of 20% or less of the OSF region disappearance pulling speed V _OSF , the pulling speed is sufficiently high to suppress the occurrence of dislocation.

At this time, control of the pulling speed so as to be slower than the OSF region extinction pulling speed V _OSF is at least from 10% to 80% from the cone side of the length of the straight body portion of the silicon single crystal to be pulled up. It is preferable to carry out in the region.

  As described above, the diameter is increased in the cone process, and when the desired diameter is reached, the diameter is controlled to be constant. Therefore, for example, in order to suppress the speed of diameter expansion for a while after entering the straight cylinder process, not only the temperature but also the pulling speed is maintained at a high speed to more reliably form a straight cylinder portion having a desired diameter. Can do. The diameter control at the time of the transition to the straight body process is such that if there is a region of less than 10% from the cone side of the length of the straight body part of the silicon single crystal to be pulled up, the straight body process of the silicon single crystal The diameter can be sufficiently controlled during the transition.

In addition, if the pulling rate is controlled so as to be slower than the OSF region extinction pulling rate V _OSF , at least in the region of up to 80% of the length of the straight body portion of the silicon single crystal to be pulled up, substantially the crystal A crystal in which the OSF region disappears at the center can be obtained throughout.

Further, when the pulling rate is controlled so as to be slower than the OSF region extinction pulling rate V _OSF , the pulling rate is controlled to increase continuously or intermittently as the pulling of the silicon single crystal proceeds. It is preferable.

The resistivity of the single crystal pulled up decreases from the top side to the bottom side due to segregation. Accordingly, the OSF region disappearance pulling speed V _OSF increases from the top side toward the bottom side. As described above, the silicon single crystal doped with boron has a higher pulling speed at which the OSF region disappears as the resistivity decreases.

  Therefore, if the pulling rate is controlled to increase continuously or intermittently with the progress of pulling of the silicon single crystal as described above, the generation of dislocations is suppressed while suppressing the generation of the OSF region. That can be done more reliably. The continuous or intermittent increase in the pulling speed as described above is sufficient if the average pulling speed with the passage of time increases continuously or intermittently. For example, the pulling speed is instantaneous for reasons such as controlling the crystal diameter. The pulling speed may be decreased or increased.

  As described above, the case where the single crystal manufacturing apparatus as shown in FIG. 1 having no magnetic field applying apparatus is used has been described here. However, the present invention is not limited to this, and includes, for example, a magnetic field applying apparatus. It is also possible to use a single crystal manufacturing apparatus corresponding to the MCZ method (Magnetic Field applied Czochralski method), which has the effect of raising the durability of a quartz crucible by pulling up a silicon single crystal while applying a magnetic field. Needless to say.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to these examples.

(Comparative Example 1)
A silicon single crystal 3 was manufactured using a single crystal manufacturing apparatus as shown in FIG. First, 100 kg of silicon polycrystal was charged as a raw material in a quartz crucible 5 having a diameter of 22 inches (550 mm), and heated and melted with a heater 7 to obtain a raw material melt 4. Thereafter, the silicon single crystal 3 having a diameter of 200 mm and a length of slightly less than 110 cm was pulled up.

  The target resistivity on the top side of the silicon single crystal to be manufactured was set to 0.015 Ωcm. The resistivity profile in the axial direction of the silicon single crystal was obtained by calculation from the target resistivity on the top side, and is shown in FIG. The “solidification rate” on the horizontal axis in FIG. 2 indicates the ratio of the weight of the silicon single crystal 3 during pulling when 100 kg of the raw material melt 4 is 1.

Using the above equation (1) from the resistivity profile of FIG. 2, the OSF region disappearance pulling rate V _OSF (mm / min) and the temperature gradient G (K / K) of the crystal center when the OSF region disappears at the crystal center. mm) ratio V _OSF / G. The ratio V _OSF / G thus determined is shown by a dotted curve in FIG.

Then, the OSF region disappearance pulling speed V _OSF was calculated from the ratio V _OSF / G. At this time, the temperature gradient G (K / mm) at the crystal center is a numerical value obtained by dividing the temperature difference 12 ° C. (1412 ° C.-1400 ° C.) by the axial distance from the melting point 1412 ° C. to 1400 ° C. of silicon. It was. From the hot zone used, the temperature gradient G was calculated to be 3.09 K / mm.

Then, the silicon single crystal was pulled up while controlling the pulling rate so as to be the value of the OSF region disappearance pulling rate V _OSF obtained as described above.

  As a result, in the silicon single crystal manufactured under the conditions of Comparative Example 1, an OSF region sometimes occurred near the center of the wafer.

(Comparative Example 2)
The pulling rate of the silicon single crystal was the same as that of Comparative Example 1 except that the silicon single crystal was pulled while controlling the pulling rate so that the pulling rate of the OSF region disappearance pulling rate V _{OSF of} Comparative Example 1 was 25% slower. A silicon single crystal was manufactured.

  A silicon single crystal was manufactured under the same conditions as above, and a total of 10 batches of silicon single crystals were manufactured. Then, the dislocation-free rate of the manufactured silicon single crystal and the presence / absence of the OSF region were examined.

  As a result, in the silicon single crystal manufactured under the conditions of Comparative Example 2, no OSF region was generated near the center of the wafer. However, the dislocation-free rate was 70%, which is lower than Example 1 described later, and dislocations occurred in many of the silicon single crystals produced.

Example 1
Similar to Comparative Example 1, except that the silicon single crystal was pulled while controlling the pulling rate so that the pulling rate of the silicon single crystal was 10% slower than the OSF region disappearance pulling rate V _{OSF of} Comparative Example 1. A silicon single crystal was manufactured. The ratio V / G at this time is shown by a solid curve in FIG.

  Under the same conditions, a silicon single crystal was manufactured, and a total of 10 batches of silicon single crystals were manufactured. Table 1 shows the number of times of remelting (times / batch) performed during production, the dislocation-free rate of the produced silicon single crystal, the yield index, and the presence or absence of the OSF region, together with the results of Comparative Example 3 described later. . The yield index represents the yield in Comparative Example 3 as 1.

(Comparative Example 3)

  The silicon single crystal was pulled in the same manner as in Comparative Example 1 except that the silicon single crystal was pulled while controlling the pulling rate so that the pulling rate of the silicon single crystal was constant at 0.4 mm / min in the straight body. Manufactured. The ratio V / G at this time is shown by a solid line in FIG. The pulling rate was set as a pulling rate at which the OSF region disappears without fail, so that the resistivity was constant in the straight cylinder without particular consideration.

  A silicon single crystal was manufactured under the same conditions as above, and a total of 10 batches of silicon single crystals were manufactured. As in Example 1, Table 1 shows the number of times of remelting performed during production (times / batch), the dislocation-free rate of the produced silicon single crystal, the yield index, and the presence or absence of the OSF region.

  As a result, as shown in Table 1, it can be confirmed that both the silicon single crystals manufactured in Example 1 and Comparative Example 3 are crystals in which no OSF region is generated and the OSF region disappears at the center. It was.

  The average pulling speed was 0.40 mm / min in Comparative Example 3, whereas it was 0.66 mm / min in Example 1. Thus, in Example 1, compared with Comparative Example 3, the average pulling speed could be increased by 65%.

  As shown in Table 1, the dislocation-free rate in Comparative Example 3 was 50%, which was lower than that in Example 1. In the case of Comparative Example 3, when there was no remelting, dislocations often occurred, but once remelting, the necessity of remelting tended to continue several times, so the remelting rate was 2 .5 times / batch and more than in Example 1. In addition, when the re-melting continued and the operation time became longer, only half of the setting was obtained, and the yield was very poor compared to Example 1.

  On the other hand, in the case of Example 1, the dislocation-free rate was 90%, which was higher than that of Comparative Example 3. Furthermore, in Example 1, there was almost no remelting and the remelting rate was 0.2 times / batch. Therefore, the silicon single crystal can be manufactured stably, and the yield is about 30% better than the comparative example.

  The above results are considered to be caused by the fact that when the operation time is prolonged, a rough surface is generated on the inner surface of the quartz crucible, and quartz scraps that cause dislocation are easily generated. The ratio at which such a rough surface is generated starts to increase rapidly when the final incoming time exceeds 80 hours. Therefore, whether or not a silicon single crystal can be pulled without dislocation changes greatly in about 80 hours.

In the case of Example 1, since the pulling speed was faster than that of Comparative Example 3, when no remelting was required, it took only about 45 hours of input time. On the other hand, in the case of Comparative Example 3, since the pulling speed was slower than that of Example 1, it took about 65 hours even when there was no remelting. Therefore, in the case of Comparative Example 3, when remelting occurred, it easily exceeded 80 hours, and the dislocation-free rate was greatly deteriorated. Even when the pulling rate of the silicon single crystal is more than 20% slower than the OSF region extinction pulling rate V _{OSF of} Comparative Example 1 as in Comparative Example 2, the time required for pulling becomes longer. The same problem as in Comparative Example 3 occurs.

  On the other hand, in Example 1, it is noted that in the crystal growth of boron-doped P-type low resistivity, the pulling rate at which the OSF region disappears at the center increases as the resistivity decreases, and the pulling rate is increased as the crystal growth proceeds. The time required for crystal growth could be shortened by increasing the area within a range where no region was generated. Thereby, compared with the comparative example 3, in Example 1, since deterioration of the quartz crucible was suppressed and generation | occurrence | production of dislocation could be suppressed, suppressing generation | occurrence | production of an OSF area | region, a dislocation-free rate was made into I was able to raise it.

(Example 2)
Similar to Comparative Example 1, except that the silicon single crystal was pulled while controlling the pulling rate so that the pulling rate of the silicon single crystal was 5% slower than the OSF region disappearance pulling rate V _{OSF of} Comparative Example 1. A silicon single crystal was manufactured.

  A silicon single crystal was manufactured under the same conditions as above, and a total of 10 batches of silicon single crystals were manufactured. Then, the dislocation-free rate of the manufactured silicon single crystal and the presence / absence of the OSF region were examined.

  As a result, in the silicon single crystal manufactured under the conditions of Example 2, no OSF region was generated near the center of the wafer. Further, the dislocation-free rate was 90%, the same result as in Example 1.

(Example 3)
Similar to Comparative Example 1, except that the silicon single crystal was pulled while controlling the pulling speed so that the pulling speed of the silicon single crystal was 20% slower than the OSF region disappearance pulling speed V _{OSF of} Comparative Example 1. A silicon single crystal was manufactured.

  A silicon single crystal was manufactured under the same conditions as above, and a total of 10 batches of silicon single crystals were manufactured. Then, the dislocation-free rate of the manufactured silicon single crystal and the presence / absence of the OSF region were examined.

  As a result, in the silicon single crystal manufactured under the conditions of Example 3, no OSF region was generated near the center of the wafer. Further, the dislocation-free rate was 80%, which is higher than that of Comparative Example 3, and was sufficiently practical.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

1 ... main chamber, 2 ... pulling chamber, 3 ... silicon single crystal,
4 ... Raw material melt, 5 ... Quartz crucible, 6 ... Graphite crucible, 7 ... Heater,
8 ... heat insulating member, 9 ... graphite shield, 10 ... gas inlet, 11 ... gas outlet,
12 ... Heat shielding member, 13 ... Gas rectifier, 14 ... Radiation thermometer, 15 ... Window.

Claims (3)

A method for producing a silicon single crystal by the Czochralski method,
When the silicon single crystal to be pulled up is a boron-doped P-type silicon single crystal having a resistivity of 0.009 Ωcm to 0.02 Ωcm,
When the OSF region disappears at the crystal center, the ratio V _OSF / G of the OSF region disappearance pulling rate V _OSF (mm / min) and the temperature gradient G (K / mm) of the crystal center is obtained,
Pulling up the silicon single crystal while controlling the pulling speed so as to be slower than the OSF region disappearance pulling speed V _OSF calculated from the obtained ratio V _OSF / G in a range of 5% to 20%,
When the pulling rate is controlled to be slower than the OSF region disappearance pulling rate V _OSF , the pulling rate is controlled to increase continuously or intermittently as the pulling of the silicon single crystal proceeds. A method for producing a silicon single crystal characterized by The pulling rate control so as to be slower than the OSF region extinction pulling rate V _OSF is performed at least in the region from 10% to 80% from the cone side of the length of the straight body portion of the silicon single crystal to be pulled up. The method for producing a silicon single crystal according to claim 1, wherein the method is performed. The method for manufacturing a silicon single crystal according to claim 1, wherein the ratio V _OSF / G is calculated by the following formula (1).
V _OSF /G=1138.9×ρ ² −45.60 × ρ + 0.643 (1)
(Where, ρ: resistivity of single crystal (Ωcm), 0.009 ≦ ρ ≦ 0.02)

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