JP2004175620A - Manufacturing method of single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a single crystal by which productivity and yield are improved and manufacturing cost of the single crystal is decreased, by solving the problem of causing dislocation which has become conspicuous especially in a large diameter nitrogen-doped crystal and a low resistivity crystal, and effectively manufacturing the single crystal of high quality. <P>SOLUTION: This single crystal is manufactured by Czochralski method and this manufacturing process of a single crystal includes a process in which a melt liquid is formed by melting a crystal feedstock and a dopant in a crucible, a process in which the melt liquid is left for not shorter than 2 hours keeping the surface temperature by more than 15°C higher than its melting point, and a process in which a single crystal is grown from the melt liquid by immersing a seed crystal in the melt liquid. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a single crystal, particularly often used as a substrate for an epitaxial wafer or an annealed wafer that is manufactured as a high-quality single crystal wafer, for example, a single crystal such as a low resistivity crystal and a nitrogen-doped crystal. The present invention relates to a manufacturing method and a single crystal.
[0002]
[Prior art]
Single crystals are mainly produced by the Czochralski Method (hereinafter abbreviated as CZ method).
[0003]
When a crystal is manufactured by the CZ method, the crystal is manufactured using, for example, a single crystal manufacturing apparatus 17 as shown in FIG. The single crystal manufacturing apparatus 17 has a member for melting a polycrystalline crystal raw material, a mechanism for pulling up a single crystal, and the like, and these are housed in the main chamber 1. A pulling chamber 2 extending upward from the ceiling of the main chamber 1 is connected, and a mechanism (not shown) for pulling the single crystal 3 by a wire 13 is provided above the pulling chamber 2.
[0004]
In the main chamber 1, a quartz crucible 5 for accommodating a melt 4 in which a crystal raw material and the like are melted and a graphite crucible 6 for supporting the quartz crucible 5 are provided. These crucibles 5 and 6 are driven by a driving mechanism (not shown). ) So as to be rotatable up and down. The driving mechanism of the crucibles 5 and 6 raises the crucibles 5 and 6 by the liquid level lowering in order to compensate for the lowering of the liquid level of the melt 4 due to the pulling of the single crystal 3.
[0005]
Further, a heater 7 for melting the raw material is arranged so as to surround the crucibles 5 and 6. Outside the heater 7, a heat insulating member 8 is provided so as to surround the periphery thereof in order to prevent heat from the heater 7 from being directly radiated to the main chamber 1.
[0006]
Further, an inert gas such as an argon gas is introduced into the main chamber 1 from a gas inlet 10 provided in an upper part of the pulling chamber 2. The introduced inert gas passes between the single crystal 3 being pulled up and the gas rectification cylinder 11, passes between the lower part of the heat shield member 12 and the liquid surface of the molten liquid 4, and passes through the main chamber 1. It is discharged from a gas outlet 9 provided at the lower part.
[0007]
A crystal raw material is accommodated in a quartz crucible 5 arranged in such a single crystal production apparatus 17, and the quartz crucible 5 is heated by a heater 7 to melt the crystal raw material in the quartz crucible 5. The seed crystal 16 fixed by the seed holder 15 connected to the wire 13 is immersed in the molten liquid 4 obtained by melting the crystal raw material in this manner, and then the seed crystal 16 is pulled up, so that the seed crystal 16 is pulled up. A single crystal 3 having a desired diameter and quality is grown below the crystal 16. At this time, after the seed crystal 16 is immersed in the melt 4, so-called seed drawing (necking) is performed, in which the diameter is once reduced to about 3 mm to form a drawn portion, and then the diameter is increased to a desired diameter. The single crystal is being pulled.
[0008]
When a single crystal is manufactured by such a CZ method, it is known that temperature control is performed in order to suppress introduction of minute defects, twins, and the like into the single crystal and to improve productivity and yield. ing.
For example, as such a temperature control, in order to suppress the introduction of minute defects and dislocations into a single crystal to be manufactured, when a silicon single crystal is manufactured by the CZ method, 1440 after melting a crystal raw material. It is disclosed that a silicon single crystal is pulled while maintaining the entire silicon melt at a temperature of not more than ℃ (for example, see Patent Document 1).
Further, in order to prevent twins and polycrystals from being generated, it is also disclosed that a single crystal is pulled by controlling a temperature gradient of a melt in a crucible (for example, see Patent Document 2).
[0009]
As a single crystal manufactured by such a CZ method, for example, a silicon single crystal can be cited, and a mirror-finished wafer cut out from the silicon single crystal and processed is widely used as a substrate of a semiconductor element.
[0010]
In particular, an epitaxial wafer in which a silicon thin film is epitaxially grown on a silicon single crystal wafer has been widely used as a wafer for manufacturing individual semiconductors, bipolar ICs, and the like because of its excellent characteristics. MOS and LSI are also widely used in microprocessor units and flash memory devices because of their excellent soft error and latch-up characteristics. As an example of such excellent characteristics of the semiconductor epitaxial wafer, there is substantially no so-called grown-in defect introduced in the production of a single crystal in the epitaxial layer, so that defects such as reliability of the DRAM are reduced. That is to do. For this reason, the demand for epitaxial wafers is expanding more and more.
[0011]
As such an epitaxial wafer, a substrate using a low resistivity crystal of, for example, 0.1 Ωcm or less or a substrate using a nitrogen-doped crystal for the substrate has a strong gettering ability. Therefore, there is much demand and the importance is increasing more and more.
[0012]
For the same reason, the importance of annealed wafers is increasing. In particular, nitrogen-doped crystals are increasingly used for substrates as a technique for improving the quality of the wafer surface layer by performing annealing and at the same time forming a gettering source inside the wafer.
[0013]
Furthermore, in recent years, semiconductor devices have become more highly integrated and more precise, and the diameter of wafers used has been increasing. In particular, there is an increasing demand for large diameter wafers with a diameter of 150 mm, 200 mm or more, and even 300 mm or more.
As described above, in particular, the importance of a large diameter nitrogen-doped crystal and a low resistivity crystal is increasing.
[0014]
[Patent Document 1]
JP-A-7-25695
[Patent Document 2]
JP-A-9-175892
[0015]
[Problems to be solved by the invention]
By the way, when growing a large diameter crystal by the CZ method, there is a problem that dislocations are likely to occur, especially from the era when a crystal having a diameter of 150 mm or more has been grown. In particular, when producing a nitrogen-doped crystal or a low resistivity crystal having a large diameter, the occurrence of dislocations has been significantly increased. If dislocations occur during single crystal growth, the growing crystal is re-melted and the single crystal is grown again. At present, a single crystal is finally formed while repeating this remelting several times.
[0016]
However, even if dislocations occur many times, the productivity will be reduced.However, during re-melting, the quartz crucible may be damaged and a single crystal may not be grown. This has led to a decline in productivity. In such a situation, the amount of the product that can be obtained with respect to the amount of the input crystal raw material is reduced, and the yield is also reduced. As a result, there has been a problem that the cost of manufacturing a single crystal is increased.
[0017]
The present invention has been made in view of such problems, and has become particularly conspicuous in large-diameter nitrogen-doped crystals and low resistivity crystals, etc., and solves the problem of dislocations during crystal growth, It is an object of the present invention to provide a single crystal manufacturing method capable of efficiently manufacturing a high quality single crystal, thereby improving the productivity and yield thereof and reducing the cost of the single crystal manufacturing.
[0018]
[Means for Solving the Problems]
The present invention has been made in order to solve the above problems, and in a method for producing a single crystal by the Czochralski method, at least, a step of melting a crystal raw material and a dopant in a crucible to generate a molten liquid, A step of maintaining the surface temperature of the melt at least 15 ° C. higher than the melting point of the crystal raw material for at least 2 hours, and a step of immersing a seed crystal in the melt and growing a single crystal from the melt. A method for producing a single crystal is provided (claim 1).
[0019]
As described above, when a single crystal is produced by the Czochralski method, a melt is generated by melting a crystal raw material and a dopant in a crucible, and then the melt is heated to a surface 15 ° C. or more higher than the melting point of the crystal raw material. By keeping the temperature for 2 hours or more, it is possible to sufficiently dissolve the dopant and the like, which have conventionally been often dissolved in the melt, into the melt. Therefore, one of the causes of dislocations during the subsequent growth of the single crystal, which is a problem that the dopant or the like remains dissolved in the melt, can be solved. The number of dislocations can be reduced. As a result, productivity and yield during single crystal production can be improved.
[0020]
In this case, the dopant may be one or more of boron, silicon nitride, carbon, and silicon carbide.
[0021]
In this way, the dopant that melts together with the crystal raw material, boron, silicon nitride, carbon, or silicon carbide, which has been frequently doped into the crystal for high quality in recent years, is also considered as a hardly soluble one. By the leaving step in the present invention, such a hardly soluble dopant can be sufficiently dissolved in the melt.
[0022]
In this case, the single crystal to be grown has a resistivity in the range of 0.001 to 0.1 Ωcm and / or a nitrogen concentration of 1 × 10 5 ^Thirteen / Cc or more 1 × 10 ^Fifteen / Cc or less (claim 3).
[0023]
As described above, even when the single crystal to be grown has a low resistivity or a nitrogen concentration in the above-described range, it is necessary to introduce a large amount of a hardly soluble dopant into the single crystal. The hardly soluble dopant having a large amount can be sufficiently dissolved in the melt.
[0024]
In this case, the diameter of the single crystal to be grown can be 150 mm or more (Claim 4), and the Czochralski method can be an MCZ method that applies a magnetic field (Claim 5). ). Furthermore, the single crystal to be grown can be a silicon single crystal.
[0025]
If the single crystal to be grown has a large diameter of, for example, 150 mm or more, the diameter of the crucible to be used must be large. However, a large-diameter crucible has a portion where the distance from the heater is large, and a low-temperature portion is formed in the melt, so that the hardly soluble substance is hardly dissolved. Further, in the MCZ method, since the convection of the melt in the crucible is suppressed, the temperature in the crucible becomes more non-uniform, and a low-temperature portion is formed in the melt. For this reason, solidification easily occurs in the melt, and the hardly soluble dopant tends to remain undissolved. In the present invention, such a solidified product and the remaining dissolved dopant can be sufficiently dissolved in the solution by the leaving step. Therefore, the single crystal production method of the present invention is effective for use in producing a silicon single crystal, which has recently been increased in diameter in recent years and often produced by the MCZ method in recent years.
[0026]
In this case, it is preferable that the surface temperature of the maintained molten liquid is set to a temperature exceeding 20 ° C. from the melting point of the crystal raw material, and the time for leaving the liquid is 10 hours or less (claim 7).
[0027]
As described above, if the surface temperature of the melt to be maintained in the leaving step is set to a temperature higher than the melting point of the crystal raw material by more than 20 ° C., for example, the dopant or the like may be used for a shorter time such as 10 hours or less. Can be more sufficiently melted in the melt. Therefore, the productivity and the yield at the time of manufacturing a single crystal can be reliably improved.
[0028]
Furthermore, the present invention provides a single crystal produced by the method for producing a single crystal (claim 8).
[0029]
Thus, for example, a large-diameter nitrogen-doped crystal or a low-resistance crystal produced by the single crystal production method of the present invention has high quality and stable characteristics, and is comparatively more in comparison with the conventional one. It can be inexpensive.
[0030]
Hereinafter, the present invention will be described in more detail.
The present inventors have found that, when a single crystal is produced by the CZ method, a crystal material and a dopant are melted into a melt as in the conventional method, and then the melt can be rapidly grown to maintain productivity. It is considered that, when the growth of the single crystal is started at a certain temperature, the poorly soluble dopant or the like does not completely dissolve in the melt, thereby causing a dislocation phenomenon. In other words, the present inventors start cultivating a single crystal by immersing the seed crystal in the melt while the hardly soluble dopant or the like is not completely melted. It was thought that the crystal was dislocated by approaching and further adhering to the crystal. In particular, in recent years, in growing large-diameter crystals, a sparingly soluble dopant is often used to dope carbon or nitrogen. In addition, a large amount of boron needs to be introduced in order to reduce the resistivity, and it is considered that dislocations have occurred due to the residual melting of boron.
[0031]
Therefore, the present inventors have conducted intensive studies and repeated experiments, and as a result, the cause of the occurrence of dislocations during the growth of a single crystal is, indeed, the fact that the hardly soluble dopant or the like does not completely dissolve in the melt, Was found to be caused by floating and attaching to the growing single crystal. Conventionally, it was found that the single crystallization was achieved during remelting several times because the hardly soluble dopant or the like finally melted during remelting.
[0032]
Thus, the present inventors, without melting the crystal raw material and dopant to form a melt immediately after the crystal growth, without melting the quartz crucible higher than the melting point of the crystal raw material the melt so that the quartz crucible is softened It is found that dislocation phenomenon can be avoided by leaving the dopant etc. sufficiently in the melt by leaving it at a high temperature for a certain time or more and then growing a single crystal from the melt. The present invention has been completed.
[0033]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.
In the present invention, at the time of producing a single crystal by the Czochralski method, at least, a step of melting a crystal raw material and a dopant in a crucible to generate a molten liquid; A single crystal is produced by performing a step of maintaining the above high surface temperature for 2 hours or more and a step of immersing a seed crystal in the melt and growing a single crystal from the melt.
[0034]
First, a process of melting a crystal raw material and a dopant in a crucible to generate a melt will be described.
In this step, for example, a crystal raw material such as polycrystalline silicon and a dopant are filled in a crucible and melted. At this time, while the melt and the crystal raw material are mixed, the temperature of the melt in the quartz crucible is the melting point of the crystal raw material. However, when the raw material in the melt is completely melted, the temperature of the melt exceeds the melting point and rises sharply. If the temperature rises beyond the desired maintenance temperature in the next standing step, not only will the time required for the temperature drop be lost, but if the temperature is too high, the quartz material crucible will soften or melt. The liquid may boil.
[0035]
Therefore, an operation such as lowering the power of the heater is performed before the crystal raw material is completely melted, and the temperature in the crucible is immediately increased to a desired maintenance temperature in the next process without raising the temperature in the crucible more than necessary after the completion of the melting. Reaching is important to maintain high productivity.
[0036]
Examples of the dopant which is added together with the crystal raw material and melted include a dopant for giving conductivity to a single crystal such as boron, and a dopant for suppressing crystal defects such as nitrogen and carbon. These are melted together with the crystal raw material either alone or in combination.
[0037]
As a method of doping boron, there are a case where a metal boron element is used as it is, and a case where a crystal (or an alloy) grown thereby is crushed is used as a dopant. In general, when growing a crystal having a low resistivity, for example, in the range of 0.001 Ωcm or more and 0.1 Ωcm or less, the metal boron element is used as a dopant as it is. Crystallized material (or alloyed with silicon) is used as a dopant. Although the dopant is slightly insoluble even once crystallized with silicon, the metal boron element has a melting point of 2080 ° C. and is particularly insoluble.
[0038]
When doping with nitrogen, silicon nitride (Si ₃ N ₄ ). The purpose of doping is to improve the gettering ability and to control the size of the grown-in defect to be small. To obtain these effects, the nitrogen concentration in the crystal must be 1 × 10 ^Thirteen / Cc or more is required. On the other hand, when the nitrogen concentration in the crystal is 1 × 10 ^Fifteen If it exceeds / cc, there is a problem that it approaches the solid solubility limit and does not form a single crystal. Therefore, the nitrogen concentration in the crystal is 1 × 10 ^Thirteen / Cc or more 1 × 10 ^Fifteen It is important to dope so as to fall within the range of / cc or less. Silicon nitride used in this manner is also insoluble, having a melting point of 1900 ° C.
[0039]
Further, examples of the hardly soluble dopant include carbon having a melting point of 3600 ° C. and silicon carbide having a melting point of 2700 ° C. Carbon may be doped for the purpose of controlling the gettering ability.
The hardly soluble substances listed above exceed the melting point of silicon and also exceed the softening point of quartz crucibles.However, if they are left for a predetermined period of time, they undergo a chemical reaction with the melt and dissolve into the melt, causing dislocation. The generation of suspended matter that causes air pollution is suppressed.
[0040]
According to the method of the present invention, even if the dopant to be melted together with the crystal raw material is, for example, such a hardly soluble dopant, in the next standing step, the molten liquid is maintained at a surface temperature higher than the melting point of the crystal raw material. By allowing the dopant to stand for a desired time, a chemical reaction occurs between the dopant and the molten crystal raw material, so that the dopant can be sufficiently dissolved in the melt. It is said that molten silicon dissolves almost everything, although there is a difference in the melting rate.
[0041]
Next, a description will be given of a step of keeping the melt at a surface temperature higher than the melting point of the crystal raw material by 15 ° C. or more for 2 hours or more.
[0042]
At the time of leaving, the surface temperature of the molten liquid is at least 15 ° C. higher than the melting point of the crystal raw material, and moreover 20 ° C. higher than the melting point. For example, when the crystal raw material is silicon, the melting point is about 1420 ° C. By maintaining the temperature at a temperature of not less than 1 ° C., preferably at a temperature of more than 1440 ° C., solidification hardly occurs in the melt, and the dopant can be sufficiently melted in the melt, thus suppressing dislocations can do.
[0043]
On the other hand, in a situation where the surface temperature of the melt becomes too high, the temperature of the crucible near the heater will be higher. As a result, not only does the crucible become damaged and a single crystal cannot be grown, but when the temperature rises further, the crucible may soften and lose its shape. Therefore, it is preferable to avoid extremely high temperatures, and it is preferable that the temperature be lower than the softening temperature of the crucible. Further, for example, since the softening point of a quartz crucible used for producing a single crystal is around 1650 ° C., the temperature at which the temperature of the crucible portion close to the heater becomes maximum should not exceed at least 1600 ° C. More preferred.
[0044]
Further, by setting the leaving time to at least 2 hours or more, preferably 3 hours or more, a dopant or the like can be dissolved in the melt, so that dislocations can be suppressed and productivity and production cost can be reduced. Can be improved.
[0045]
On the other hand, if the standing time is as long as 12 hours, the dopant and the like can be sufficiently melted in the melt, and the effect of melting the dopant and the like does not change much even if the standing time exceeds 12 hours. Therefore, even when the crystal is left for more than 12 hours, the number of dislocations generated during the growth of the crystal is not so different from the number of dislocations when the crystal is left for 12 hours. For this reason, the adverse effect of the time loss due to the long standing time increases, which leads to a decrease in productivity. Further, the load on the crucible and the heater increases, which is not preferable.
[0046]
As a condition in such a leaving step, it is preferable that the surface temperature of the maintained melt is higher than the melting point of the crystal raw material by more than 20 ° C. By increasing the temperature in this manner, the undissolved residue of the dopant or the like can be more sufficiently melted in the melt even for a shorter time, for example, 10 hours or less. Therefore, productivity and yield can be further improved.
[0047]
Next, a step of immersing a seed crystal in the melt and growing a single crystal from the melt will be described.
[0048]
In recent years, single crystals such as silicon single crystals have remarkably increased in diameter. As the diameter of the single crystal grown in this single crystal growing step increases, the diameter of the crucible used accordingly increases. In a large-diameter crucible, since there is a portion where the distance from the heater is large, a portion where the temperature of the melt is low is generated and solidification easily occurs. In particular, the hardly soluble dopant is apt to remain undissolved, and as a result, dislocations occur frequently. Therefore, the method for producing a single crystal of the present invention is particularly suitable for producing a single crystal having a large diameter, for example, 150 mm or more, 200 mm or more, or even 300 mm or more.
[0049]
Also, when growing such a large-diameter crystal, the MCZ method for applying a magnetic field to control the convection of the melt in the crucible is increasing. However, when a magnetic field is applied, the convection of the molten liquid in the crucible is generally suppressed, so that the temperature distribution in the crucible becomes non-uniform, and a low-temperature portion is generated. For this reason, the hardly soluble dopant and the like are more likely to remain dissolved in the molten liquid, and as a result, dislocations are more frequently generated. ADVANTAGE OF THE INVENTION The crystal manufacturing method of this invention can make a hardly soluble dopant etc. fully melt | dissolve in a melt, even when the convection in a melt is controlled by applying a magnetic field during crystal growth.
[0050]
The single crystal grown by the single crystal manufacturing method of the present invention as described above has high quality and stable characteristics. In addition, since dislocation at the time of growing a single crystal is suppressed, the productivity and the yield are improved, so that the material is supplied at a lower cost than in the past.
[0051]
【Example】
Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
(Example 1)
A single crystal manufacturing apparatus whose schematic diagram is shown in FIG. 1 and a hot zone equipped with a crucible having a diameter of 800 mm were used to grow a single crystal having a diameter of 300 mm by the MCZ method.
A quartz crucible was charged with 320 kg of silicon polycrystal as a crystal raw material, and a single crystal having a straight body length of about 120 cm was grown while applying a horizontal magnetic field having a central magnetic field strength of 3500 G to the quartz crucible. At this time, a metal boron element was put in a quartz crucible together with the polycrystal as a dopant so that the resistivity was 0.008 Ωcm in a single crystal of 0 cm. After melting the silicon polycrystal and the metal boron element into a melt, the temperature of the surface of the melt is set to about 20 ° C. higher (about 1440 ° C.) than the melting point of silicon crystal (about 1420 ° C.). This was left at this temperature for 6 hours without any operation. Thereafter, a seed crystal was immersed in the melt, and a single crystal was grown from the melt. When the crystal was dislocated in the middle, the crystal was melted again, and this was repeated until a single crystal usable as a product was obtained. Eleven single crystals were grown under these conditions, and the number of dislocations per single crystal and productivity were determined.
[0052]
The result is shown in FIG. As a result, the number of dislocations per line was 1.09. The productivity of the single crystal was 1.35 when the productivity of Comparative Example 1 of the prior art described later was set to 1.
[0053]
(Example 2)
A single crystal was grown under exactly the same conditions as in Example 1 except that the melt was set at about 20 ° C. higher than the melting point of the silicon crystal and then left for 12 hours. Under these conditions, ten single crystals were grown, and the number of dislocations per single crystal and the productivity were determined. The result is shown in FIG. As a result, the number of dislocations per line was 0.5, which was extremely reduced as compared with Example 1. The productivity of the single crystal was 1.31 when the productivity of Comparative Example 1 described later was set to 1.
For this reason, in Example 2, the number of dislocations was reduced as compared to Example 1 with the prolonged leaving time, but the productivity of Example 2 was reduced due to the prolonged leaving time. It turns out that it is almost equivalent to Example 1.
[0054]
(Example 3)
A single crystal was grown under exactly the same conditions as in Example 1 except that the melt was set at about 20 ° C. higher than the melting point of the silicon crystal and then left for 3 hours. Under these conditions, ten single crystals were grown, and the number of dislocations per single crystal and the productivity were determined. The result is shown in FIG. As a result, the number of dislocations per line was 2.1. The productivity of the single crystal was 1.23 when the productivity of Comparative Example 1 described later was set to 1.
From this, it can be seen that in Example 3, the number of dislocations was increased as compared with Example 1, but the productivity was significantly improved as compared with the case where no dislocation was performed.
[0055]
(Example 4)
A single crystal was grown under exactly the same conditions as in Example 1 except that the melt was set at about 30 ° C. higher than the melting point of the silicon crystal and then left for 6 hours. Under these conditions, ten single crystals were grown, and the number of dislocations per single crystal and the productivity were determined. As a result, the number of dislocations per line was 0.90, which was smaller than that in Example 1. In addition, the productivity of the single crystal was 1.44 when the productivity of Comparative Example 1 described later was set to 1.
From this, in Example 4, it is possible to dissolve the hardly soluble substance more quickly by raising the temperature at the time of standing than in Example 1, and the number of dislocations is further reduced as compared with Example 1. Therefore, it can be seen that the productivity is further improved.
[0056]
(Example 5)
After setting the melt at about 20 ° C. higher than the melting point of the silicon crystal, the standing time was set to 3 hours, the resistivity was set to about 20 Ωcm at 0 cm of the single crystal, and the nitrogen concentration was set to 3 × 10 ^Thirteen A single crystal was grown under exactly the same conditions as in Example 1, except that silicon nitride was added together with the polycrystalline raw material in the quartz crucible to be / cc. At this time, as the dopant for controlling the resistivity, a dopant once crystallized with silicon was used instead of the metal boron element. Nine single crystals were grown under these conditions, and the number of dislocations per single crystal and the productivity were determined. The result is shown in FIG. As a result, the number of dislocations per one was 0.44. Further, the productivity of the crystal was 1.23 when the productivity of Comparative Example 2 described later was set to 1.
[0057]
(Comparative Example 1)
Example 1 was repeated except that the melt was set at about 20 ° C. higher than the melting point of the silicon crystal, and the seed crystal was immediately immersed in the melt to grow a single crystal without being allowed to stand. A single crystal was grown under exactly the same conditions, and the number of dislocations per single crystal and the productivity were determined. Eight single crystals were grown under these conditions, and the number of dislocations per single crystal and the productivity were determined. The result is shown in FIG. As a result, the number of dislocations per line was 3.25.
[0058]
(Comparative Example 2)
Example 5 was repeated except that the melt was set at about 20 ° C. higher than the melting point of the silicon crystal, and the seed crystal was immediately immersed in the melt to grow a single crystal without being left. A single crystal was grown under exactly the same conditions. Eight crystals were grown under these conditions, and the number of dislocations per single crystal and the productivity were determined. The result is shown in FIG. As a result, the number of dislocations per line was 1.13.
[0059]
FIG. 2 is a graph comparing the number of dislocations per single crystal and the productivity under each single crystal production condition of Examples 1, 2, 3 and Comparative Example 1.
From FIG. 2, as compared with Comparative Example 1 in which there is no standing time, in Examples 1, 2, and 3 where the leaving time is 3 hours or more, the number of dislocations per single crystal is remarkable. It can be seen that it is less. Furthermore, the number of dislocations per single crystal decreases as the standing time increases to 3 hours, 6 hours, and even 12 hours.
[0060]
On the other hand, when comparing the productivity, Examples 1, 2 and 3 in which the leaving time was 3 hours or more were significantly improved in comparison with Comparative Example 1 in which there was no leaving time. You can see that it is doing. This is because even if there is a time loss of leaving the first, second, and third embodiments, the number of dislocations is reduced, and the time loss due to repeated remelting when dislocations occur is reduced. Because it is decreasing.
Therefore, productivity can be improved by optimizing the leaving time. In other words, it can be understood that the number of dislocations can be reduced and the productivity can be improved if the leaving time is set to 2 hours or more.
[0061]
FIG. 3 is a graph comparing the number of dislocations per single crystal and the productivity under each single crystal production condition of Example 5 and Comparative Example 2.
As can be seen from FIG. 3, the number of dislocations per single crystal in Example 5 where the leaving time was 3 hours was remarkably reduced as compared with Comparative Example 2 where the leaving time was not used. You can see that On the other hand, when comparing the productivity, Example 5 in which the leaving time was 3 hours showed that the productivity was significantly improved as compared with Comparative Example 2 in which there was no leaving time. Understand.
[0062]
Note that the present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention, and any device having the same operation and effect can be realized by the present invention. It is included in the technical scope of the invention.
[0063]
For example, in the above-described embodiment, a case where a silicon single crystal having a diameter of 300 mm is manufactured has been described by way of example. However, the present invention is not limited to this, and is also applicable to a case where a single crystal having another diameter is manufactured. This is particularly effective when applied to the production of a single crystal having a large diameter such as a diameter of 150 mm or more, or a diameter exceeding 300 mm.
[0064]
Further, in the above embodiment, the single crystal is manufactured by setting the surface temperature of the melt to be maintained in the leaving step at a temperature higher by 20 ° C. or 30 ° C. than the melting point of the crystal raw material. The temperature is not limited to these, as long as the surface temperature of the melt is at least 15 ° C. higher than the melting point of the crystal raw material and the temperature of the highest temperature portion of the crucible is lower than the softening temperature of the crucible. If applicable.
[0065]
【The invention's effect】
As described above, according to the present invention, the gettering ability of the gettering ability is improved by successfully melting the hardly-soluble dopant, which has been frequently doped into a single crystal in recent years for high quality, into a melt. It is possible to improve the productivity and reduce the cost of high-quality crystals with high crystal defects and few crystal defects, and high yield in LSI devices can be expected.
[Brief description of the drawings]
FIG. 1 is a schematic view of a single crystal manufacturing apparatus and a hot zone.
FIG. 2 is a graph comparing the number of dislocations per single crystal and the productivity under each single crystal production condition of Examples 1, 2, and 3 and Comparative Example 1.
FIG. 3 is a graph comparing the number of dislocations per single crystal and the productivity under each single crystal production condition of Example 5 and Comparative Example 2.
[Explanation of symbols]
1 ... main chamber, 2 ... pulling chamber, 3 ... single crystal,
4 ... melt, 5 ... quartz crucible, 6 ... graphite crucible, 7 ... heater,
8: heat insulating member, 9: gas outlet, 10: gas inlet,
11: gas rectifying cylinder, 12: heat shielding member, 13: wire,
14 ... shaft, 15 ... seed holder, 16 ... seed crystal,
17: Single crystal production equipment.

Claims (8)

In the method of producing a single crystal by the Czochralski method, at least a step of melting a crystal raw material and a dopant in a crucible to generate a melt, and setting the surface temperature of the melt at 15 ° C. or more higher than the melting point of the crystal raw material. A method for producing a single crystal, comprising: a step of maintaining and leaving to stand for 2 hours or more; and a step of immersing a seed crystal in the melt and growing a single crystal from the melt. The method according to claim 1, wherein the dopant is at least one of boron, silicon nitride, carbon, and silicon carbide. The single crystal to be grown has a resistivity in the range of 0.001 Ωcm to 0.1 Ωcm and / or a nitrogen concentration in the range of 1 × 10 ¹³ / cc to 1 × 10 ¹⁵ / cc. The method for producing a single crystal according to claim 1, wherein: The method for producing a single crystal according to any one of claims 1 to 3, wherein a diameter of the single crystal to be grown is 150 mm or more. The method of manufacturing a single crystal according to claim 1, wherein the Czochralski method is an MCZ method in which a magnetic field is applied. The method for producing a single crystal according to any one of claims 1 to 5, wherein the single crystal to be grown is a silicon single crystal. 7. The method according to claim 1, wherein the surface temperature of the maintained melt is set to a temperature exceeding 20 ° C. from the melting point of the crystal raw material, and the standing time is set to 10 hours or less. 3. The method for producing a single crystal according to item 1. A single crystal produced by the method according to any one of claims 1 to 7.

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